AISC 358s2-20 PUBLIC REVIEW DRAFT 1 AISC 358s2-20 Public Review Draft Dated August 2, 2019 Supplement No. 2 to Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications AMERICAN INSTITUTE OF STEEL CONSTRUCTION 1 2 3 4 Prequalified Connections for 5 Special and Intermediate 6 Steel Moment Frames for 7 Seismic Applications 8 Supplement No. 2 9 10 11 12 2020 13 14 A supplement to ANSI/AISC 358-16 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 AMERICAN INSTITUTE OF STEEL CONSTRUCTION 35 130 East Randolph Street, Suite 2000 36 Chicago, Illinois 60601 37 38
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AISC 358s2-20 PUBLIC REVIEW DRAFT 1
AISC 358s2-20 Public Review Draft Dated August 2, 2019 Supplement No. 2 to Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications
AMERICAN INSTITUTE OF STEEL CONSTRUCTION
1
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Prequalified Connections for 5
Special and Intermediate 6
Steel Moment Frames for 7
Seismic Applications 8
Supplement No. 2 9
10
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2020 13
14
A supplement to ANSI/AISC 358-16 15
16
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION 35
130 East Randolph Street, Suite 2000 36
Chicago, Illinois 60601 37 38
AISC 358s2-20 PUBLIC REVIEW DRAFT 2
AISC 358s2-20 Public Review Draft Dated August 2, 2019 Supplement No. 2 to Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications
All rights reserved. This book or any part thereof 46
must not be reproduced in any form without the 47
written permission of the publisher. 48
49
The AISC logo is a registered trademark of AISC. 50
51
The information presented in this publication has been prepared by a balanced committee following American 52 National Standards Institute (ANSI) consensus procedures and recognized principles of design and construction. 53 While it is believed to be accurate, this information should not be used or relied upon for any specific application 54 without competent professional examination and verification of its accuracy, suitability and applicability by a 55 licensed engineer or architect. The publication of this information is not a representation or warranty on the part of 56 the American Institute of Steel Construction, its officers, agents, employees or committee members, or of any other 57 person named herein, that this information is suitable for any general or particular use, or of freedom from 58
infringement of any patent or patents. All representations or warranties, express or implied, other than as stated 59 above, are specifically disclaimed. Anyone making use of the information presented in this publication assumes all 60 liability arising from such use. 61 62 Caution must be exercised when relying upon standards and guidelines developed by other bodies and incorporated 63 by reference herein since such material may be modified or amended from time to time subsequent to the printing of 64 this edition. The American Institute of Steel Construction bears no responsibility for such material other than to refer 65 to it and incorporate it by reference at the time of the initial publication of this edition. 66
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Printed in the United States of America 68
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AISC 358s2-20 Public Review Draft Dated August 2, 2019 Supplement No. 2 to Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications
AMERICAN INSTITUTE OF STEEL CONSTRUCTION
70
PREFACE 71
72
73
(This Preface is not part of AISC 358s2-20, Supplement 2 to Prequalified Connections for Special and 74
Intermediate Steel Moment Frames for Seismic Applications, but is included for informational purposes only.) 75
76
This supplement was developed by the AISC Connection Prequalification Review Panel (CPRP) using a 77
consensus process. This document is the second supplement to ANSI/AISC 358-16, Prequalified Connections 78
for Special and Intermediate Steel Moment Frames for Seismic Applications. 79
This supplement expands the prequalification scope of Chapter 11 SidePlate Moment Connection and 80
Chapter 12 Simpson Strong-Tie Strong Frame. The SidePlate moment connection prequalification has been 81
expanded to include a new biaxial configuration with HSS or built-up box columns as well as a new bolted 82
configuration, configuration C (tuck). The Simpson moment connection prequalification has been expanded to 83
include an end-plate connection for smaller beams, stronger Yield-Links, a design procedure for the Yield-84
Link buckling restraint mechanism, and to expand beam and column limitations. 85
A non-mandatory Commentary has been prepared to provide background for the provisions of the 86
Standard and the user is encouraged to consult it. Additionally, non-mandatory User Notes are interspersed 87
throughout the Standard to provide concise and practical guidance in the application of the provisions. 88
The reader is cautioned that professional judgment must be exercised when data or recommendations in 89
this Standard are applied, as described more fully in the disclaimer notice preceding the Preface. 90
91
This Standard was approved by the CPRP: 92
93
Michael D. Engelhardt, Chairman 94
Brett R. Manning, Vice-Chairman 95
John Abruzzo 96
Cam Baker 97
Joel A. Chandler 98
Michael L. Cochran 99
Theodore L. Droessler 100
Gary Glenn 101
Ronald O. Hamburger 102
Amit Kanvinde 103
Gregory H. Lynch 104
Jason McCormick 105
Pat McManus 106
Kevin Moore 107
Thomas M. Murray 108
Thomas A. Sabol 109
Robert E. Shaw, Jr. 110
James A. Swanson 111
Jamie Winans 112
Benham Yousefi 113
Margaret A. Matthew, Secretary 114
115
The CPRP gratefully acknowledges the following individuals for their contributions to this document: 116
117
Henry Gallart 118
Steven Pryor 119
Behzad Rafezy 120
121
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AISC 358s2-20 Public Review Draft Dated August 2, 2019 Supplement No. 2 to Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications
AISC 358s2-20 Public Review Draft Dated August 2, 2019 Supplement No. 2 to Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications
AMERICAN INSTITUTE OF STEEL CONSTRUCTION
SYMBOLS 166
167
This Standard uses the following symbols in addition to the terms defined in the Specification for Structural Steel 168
Buildings (ANSI/AISC 360-16) and the Seismic Provisions for Structural Steel Buildings (ANSI/AISC 341-16). 169
Some definitions in the following list have been simplified in the interest of brevity. In all cases, the definitions given 170
in the body of the Standard govern. Symbols without text definitions, used in only one location and defined at that 171
location, are omitted in some cases. The section or figure number on the right refers to where the symbol is first used. 172
173
Symbol Definition Section 174
175
Ac Area of concrete in the column, if applicable, in.2 (mm2) ............................................... 11.4 176
Ag Area of the steel column, in.2 (mm2) .............................................................................. 11.4 177
Ay-link Yield area of reduced Yield-Link section, in.2 (mm2) ..................................................... 12.9 178
L Distance between column centerlines, in. (mm) ........................................................ 11.3(5) 205
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
Lbm-side Length of nonreduced Yield-Link at beam side, in. (mm) ....................................... Fig. 12.2 206
Lcant Lever arm from start of reduced region to edge of spacer plate bolt hole, plus plate stretch 207
from 0.05 rad of rotation, in. (mm) ................................................................. Figure 12.4(a) 208
209
Lcol-side Length of nonreduced Yield-Link at column side, in. (mm) .................................... Fig. 12.2 210
Lcrit Length of critical shear plane through cover plate as shown in Figure C-11.6, in. 211
AISC 358s2-20 Public Review Draft Dated August 2, 2019 Supplement No. 2 to Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications
Zxb Plastic modulus of beam about the x-axis, in.3 (mm3) ..................................................... 11.7 254
Zxc Plastic modulus of column about the x-axis, in.3 (mm3) .................................................. 11.7 255
a Horizontal distance from centerline of bolt holes in shear plate to 256
face of column, in. (mm) .......................................................................................... 12.4(2) 257
b Vertical distance from centerline of bolt holes in Yield-Link flange to 258
face of Yield-Link stem, in. (mm) ................................................................................. 12.9 259
b Distance from the bolt centerline to the beam centerline, in. (mm) ................................ 12.9 260
bbm-side Width of nonreduced Yield-Link at beam side, in. (mm) ......................................... Fig. 12.2 261
bcol-side Width of nonreduced Yield-Link at column side, in. (mm) ..................................... Fig. 12.2 262
bflange Width of Yield-Link flange at column side, in. (mm) .............................................. Fig. 12.2 263
bn Net width of buckling restraint plate, in. (mm) .............................................................. 12.9 264
byield Width of reduced Yield-Link section, in. (mm)....................................................... Fig. 12.2 265
db-brp Diameter of bolt connecting buckling restraint plate to beam 266
flange, in. (mm) ................................................................................................. Figure 12.3 267
db-flange Diameter of bolt connecting Yield-Link flange to column flange, 268
in. (mm) ....................................................................................................................... 12.9 269
db-sp Diameter of bolts in shear plate, in. (mm) ...................................................................... 12.9 270
db-stem Diameter of bolts connecting Yield-Link stem to beam flange, in. (mm) ........................ 12.9 271
dpl Depth of vertical shear element, in. (mm) ................................................. Commentary 11.7 272
dc1, dc2 Depth of column on each side of a bay in a moment frame, in. (mm) ............................. 11.3 273
cf Specified compressive strength of the concrete infill, if applicable, ksi (MPa) ................ 11.4 274
g Gap increase due to transverse shortening of the Yield-Link thickness, in. (mm) ............ 12,9 275
gflange Vertical distance between rows of bolts in connection of Yield-Link flange 276
to column flange, in. (mm) ..................................................................................... Fig. 12.2 277
gstem Horizontal distance between rows of bolts in connection of Yield-Link stem 278
to beam flange, in. (mm) ........................................................................................ Fig. 12.2 279
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
hflange Height of Yield-Link flange, in. (mm) .................................................................... Fig. 12.2 280
lo Effective buckling wave length .................................................................................... 12.9 281
lpl Effective length of horizontal shear plate, in. (mm)................................... Commentary 11.7 282
nBRP-bolts Total number of buckling restraint plate bolts ................................................................ 12.9 283
nbolt Number of bolts in Yield-Link stem-to-beam flange connection .................................... 12.9 284
nbolt-sp Total number of bolts in shear plate............................................................................... 12.9 285
nbolt-sp-horz Total number of horizontal bolts resisting axial force in the shear plate in line with the 286
central bolt ................................................................................................................... 12.9 287
nbolt-sp-vert Total number of vertical bolts resisting shear force in the shear plate ............................. 12.9 288
nrows Number of rows of bolts in Yield-Link stem .................................................................. 12.9 289
p Minimum of bflange/2 or sflange, in. (mm) .......................................................................... 12.9 290
pe Effective (tributary) length per bolt from the yield line pattern, in. (mm) ....................... 12.9 291
rt Required tension force per bolt in Yield-Link flange to column flange 292
sb Distance from center of last row of bolts to beam-side end of 294
Yield-Link, in. (mm) .............................................................................................. Fig. 12.2 295
sc Distance from the reduced section of the Yield-Link to the center of the first 296
row of bolts, in. (mm) ............................................................................................ Fig. 12.2 297
sflange Spacing between bolts for Yield-Link flange-to-column-flange connection, 298
in. (mm) ................................................................................................................ Fig. 12.2 299
sstem Spacing between rows of bolts for Yield-Link stem-to-beam-flange connection, 300
in. (mm) ................................................................................................................ Fig. 12.2 301
svert Vertical distance from center of the top (or bottom) shear plate bolt to 302
center of center shear plate bolt, in. (mm) ...................................................................... 12.9 303
tBRP-min Minimum thickness of buckling restraint plate to prevent yielding during compression of 304
the link stem, in. (mm) .................................................................................................. 12.9 305
tcp Thickness of cover plates, in. (mm) .......................................................... Commentary 11.7 306
tflange Thickness of Yield-Link flange, in. (mm) ............................................................... Fig. 12.2 307
tstem Thickness of Yield-Link stem, in. (mm) ................................................................. Fig. 12.2 308
x Distance from plastic hinge location to centroid of connection element, in. (mm) ........... 11.7 309
Δ0.04 Axial deformation in Yield-Link at a connection rotation of 0.04 rad ............................. 12.9 310
Δ0.07 Axial deformation in Yield-Link at a connection rotation of 0.07 rad ............................. 12.9 311
Δy Axial deformation in Yield-Link at expected yield, in. (mm) ......................................... 12.9 312
k Coefficient of dry kinetic friction, taken as 0.3 .............................................................. 12.9 313
θy Connection rotation at expected yield of Yield-Link, rad ............................................... 12.9 314
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
CHAPTER 11 315
SIDEPLATE MOMENT CONNECTION 316
317
The user’s attention is called to the fact that compliance with this chapter of the standard requires use of an 318
invention covered by multiple U.S. and foreign patent rights.1 By publication of this standard, no position is taken 319
with respect to the validity of any claim(s) or of any patent rights in connection therewith. The patent holder has 320
filed a statement of willingness to grant a license under these rights on reasonable and nondiscriminatory terms and 321
conditions to applicants desiring to obtain such a license, and the statement may be obtained from the standard’s 322
developer. 323
11.1. GENERAL 324
The SidePlate® moment connection utilizes interconnecting plates to connect beams to columns. The 325 connection features a physical separation, or gap, between the face of the column flange and the end of 326 the beam(s). Both field-welded and field-bolted options are available. Beams may be either rolled or 327 built-up wide-flange sections or hollow structural sections (HSS). Columns may be either rolled or 328 built-up wide-flange, built-up box, boxed I-shaped, or HSS sections. Built-up flanged cruciform 329
sections consisting of rolled shapes or built up from plates may also be used as columns for biaxial 330 configurations. Figures 11.1, 11.2, and 11.3 show the various field-welded and field-bolted uniaxial 331 connection configurations. The field-bolted option is available in three configurations, referred to as 332 configuration A (standard), configuration B (narrow) and configuration C (tuck) as shown in Figure 333 11.3. 334
335 In the field-welded connection, top and bottom beam flange cover plates (rectangular or U-shaped) are 336 used at the end(s) of the beam, as applicable, which also serve to bridge any difference between flange 337 widths of the beam(s) and of the column. The connection of the beam to the column is accomplished 338
with parallel full-depth side plates that sandwich and connect the beam(s) and the column together. In 339 the field-bolted connection, beam flanges are connected to the side plates with either a cover plate or a 340 pair of angles and high strength pretensioned bolts as shown in Figures 11.2 and 11.3. Column 341 horizontal shear plates and beam vertical shear elements (as applicable) are attached to the wide-flange 342 column and beam webs, respectively. 343
344
(a) (b) (c)
1 The SidePlate
® connection configurations and structures illustrated herein, including their described fabrication and
erection methodologies, are protected by one or more of the following U.S. and foreign patents: U.S. Pat. Nos. 5,660,017; 6,138,427; 6,516,583; 6,591,573; 7,178,296; 8,122,671; 8,122,672; 8,146,322; 8,176,706; 8,205,408; 9,091,065; Mexico Pat. No. 208,750; New Zealand Pat. No. 300,351; British Pat. No. 2497635; all held by MiTek
Holdings LLC. Other U.S. and foreign patent protection are pending.
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and column construction;(b) two-sided wide-flange beam and column construction; (c) wide-flange 346 beam to either HSS or built-up box column; (d) HSS beam without cover plates to wide-flange column 347 with the same flange width; (e) HSS beam to wide-flange column; and (f) HSS beam to either HSS or 348
built-up box column. 349
350
351
(a) (b) (c)
(d) (e) (f)
Fig. 11.2. Assembled SidePlate uniaxial field-bolted standard configurations (configuration A): (a) 352 one-sided wide-flange beam and column construction; (b) two-sided wide-flange beam and column 353
construction; (c) wide-flange beam to either HSS or built-up box column; (d) HSS beam to wide-flange 354 column with the same flange width; (e) HSS beam to wide-flange column; and (f) HSS beam to either 355
HSS or built-up box column. 356
357
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(a) (b) (c)
Fig. 11.3. SidePlate field-bolted connection configurations: (a) a typical field-bolted standard 358 connection (configuration A); (b) a typical field-bolted narrow connection (configuration. B); (c) a 359
Figure 11.4 shows the connection geometry and major connection components for uniaxial field-361 welded configurations. 362 363
364
Cover Plate Configurations
Plan
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
Elevation
(a)
(b)
(c)
(d)
Fig. 11.4. SidePlate uniaxial field-welded configuration geometry and major components: (a) typical 365 wide-flange beam to wide-flange column—detail, plan, and elevation views; (b) HSS beam without 366 cover plates to wide-flange column with the same flange width—plan view; (c) HSS beam to wide-367
flange column—plan view; and (d) wide-flange beam to built-up box column— plan view. 368
369
Figure 11.5 shows the connection geometry and major connection components for biaxial field-welded 370
configurations, which permits connecting up to four beams to a column. Figure 11.6 shows the 371
analogous field-bolted biaxial connection with built-up box or HSS columns. Built-up box and HSS 372
columns may be filled with concrete. All field-bolted beam configurations as shown in Figure 11.3 and 373
all field-welded configurations as shown in Figure 11.4 are permitted in biaxial applications. 374
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375
Fig. 11.5. SidePlate biaxial field-welded connection with built-up flanged cruciform column plan 376 views: (a) four sided; (b) three sided; and (c) two sided (corner) configurations. 377
378
379
Fig. 11.6. SidePlate biaxial field-bolted connection with built-up box/HSS columns plan views: (a) four 380
sided; (b) three sided and (c) two sided (corner) configurations. 381
382 Figure 11.7 shows the SidePlate built-up box/HSS biaxial configuration. Figure 11.7(b) shows the 383 assembly of the two intersecting side plates that are attached to the column to receive the beams as 384 shown in Figure 11.7(c). Each side plate is slotted to accommodate the other orthogonal side plate as 385 shown in Figure 11.7(a). The configuration shown in Figure 11.7(b) will be referred to as the side plate 386
interlock assembly herein. 387
(a) (b) (c)
(a) (b) (c)
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
(a) (b) (c)
Fig. 11.7. SidePlate built-up box/HSS biaxial configuration: (a) slotted intersecting side plates; (b) 388 side plate interlock assembly; and (c) column assembly. 389
Two different details may be used for constructing the side plate interlock assembly depending on the 390 type of the column. Figure 11.8(a) shows the plan view of a typical SidePlate biaxial configuration 391 with an HSS column where the side plates are connected with four fillet welds as shown in Figure 392 11.8(b). Figure 11.8(c) shows a typical SidePlate biaxial configuration with a built-up box column 393 where the side plates are connected with a combination of fillet and PJP welds as shown in Figure 394
11.8(d). The latter detail with PJP welds may also be used with HSS columns. 395
User Note: The side plate interlock assembly may be preassembled prior to attachment to the HSS or 396 built-up box columns. The side plates of the interlock assembly with PJP welds shown in Figure 397 11.8(d) may alternatively be attached to the column one at a time while turning the column around its 398 longitudinal axis. 399
400
(a) (b)
401
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
(c) (d)
Fig. 11.8. Biaxial side plate interlock assembly welding options: (a) HSS column plan view (b) side 402 plate interlock assembly welding configuration with HSS column; (c) built-up box column plan view; 403
(d) side plate interlock assembly welding configurations with built-up box column. 404
The SidePlate moment connection is proportioned to develop the probable maximum moment capacity 405 of the connected beam. Plastic hinge formation is intended to occur primarily in the beam beyond the 406 end of the side plates away from the column face, with limited yielding occurring in some of the 407 connection elements. 408
User Note: Moment frames that utilize the SidePlate connection can be constructed using one of three 409 methods: the full-length beam erection method (SidePlate FRAME configuration), the link-beam 410 erection method (SidePlate original configuration), and the fully shop prefabricated method. These 411
methods are described in the Commentary. 412
413
11.2. SYSTEMS 414
The SidePlate moment connection is prequalified for use in special moment frame (SMF) and 415 intermediate moment frame (IMF) systems within the limits of these provisions. The SidePlate moment 416 connections are prequalified for use in planar moment-resisting frames and orthogonal intersecting 417 moment-resisting frames (biaxial configurations, capable of connecting up to four beams at a column 418 as illustrated in Figures 11.5 and 11.6). 419
420
11.3. PREQUALIFICATION LIMITS 421
1. Beam Limitations 422
Beams shall satisfy the following limitations: 423
424 (1) Beams shall be rolled wide-flange, HSS, or built-up I-shaped beams conforming to the 425
requirements of Section 2.3. Beam flange thickness shall be limited to a maximum of 2.5 in. (63 426
mm). 427
(2) Rolled wide-flange beam depths shall be limited to W40 (W1000) and W44 (W1100) for the 428
field-welded and field-bolted connections, respectively. The depth of built-up wide-flange beams 429
shall not exceed the depth permitted for rolled wide-flange beams. 430
(3) Beam depths shall be limited as follows for HSS shapes: 431
(a) For SMF systems, HSS14 (HSS 356) or smaller. 432
(b) For IMF systems, HSS16 (HSS 406) or smaller. 433
(4) Rolled and built-up wide-flange beam weight shall be limited to 302 lb/ft (449 kg/m) and 400 lb/ft 434
(595 kg/m) for the field-welded and field-bolted connections, respectively. Beam flange area of 435
the field-bolted connection shall be limited to a maximum of 36 in.² (22900 mm2). 436
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(5) The ratio of the hinge-to-hinge span of the beam, Lh, to beam depth, d, shall be limited as follows: 437
(a) For SMF systems, Lh/d is limited to: 438
6 or greater with rectangular shaped cover plates. 439
4.5 or greater with U-shaped cover plates for field-welded connections. 440
4.0 or greater with U-shaped cover plates for field-bolted connections. 441
(b) For IMF systems, Lh/d is limited to 3 or greater. 442
The hinge-to-hinge span of the beam, Lh, is the distance between the locations of plastic hinge 443 formation at each moment-connected end of that beam. The location of the plastic hinge shall be 444 taken as one-third of the beam depth, d/3, for the field-welded connection and one-sixth of the 445 beam depth, d/6, for the field-bolted connection, away from the end of the side-plate extension, as 446 shown in Figure 11.9. Thus, 447
L = distance between column centerlines, in. (mm) 451
dc1, dc2 = depth of column on each side of a bay in a moment frame, in. (mm) 452
User Note: The 0.33d and 0.165d constants represent the distance of the plastic hinge from the 453 end of the side plate extension. A represents the typical extension of the side plates from the face 454 of column flange. 455
(6) Width-to-thickness ratios for beam flanges and webs shall conform to the limits of the AISC Seismic 456
Provisions. 457
(7) Lateral bracing of wide-flange beams shall be provided in conformance with the AISC Seismic 458
Provisions. Lateral bracing of HSS beams shall be provided in conformance with AISC Specification 459
Appendix 1, Section 1.3.2c, taking 1 2 1M M in AISC Specification Equation A-1-7. For either 460
wide-flange or HSS beams, the segment of the beam connected to the side plates shall be considered 461
to be braced. Supplemental top and bottom beam flange bracing at the expected hinge is not required. 462
(8) The protected zone in the beam for the field-welded and field-bolted connections shall consist of the 463
portion of the beam as shown in Figure 11.10 and Figure 11.11, respectively. 464
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465
Fig. 11.9. Plastic hinge location and hinge-to-hinge length. 466
2. Column Limitations 467
Columns shall satisfy the following limitations: 468
(1) Columns shall be any of the rolled or built-up wide-flange, built-up box, boxed I-shaped, HSS or 469
flanged cruciform sections consisting of rolled shapes or built-up from plates meeting the 470
requirements of Section 2.3. Flange and web plates of built up box columns shall continuously be 471
connected by fillet welds or PJP groove welds along the length of the column. 472
(2) HSS column shapes must conform to ASTM A1085. 473
(3) The beam shall be connected to the side plates that are connected to the flange tips of the wide-474
flange or corners/sides of HSS or box columns. 475
(4) Rolled shape column depth shall be limited to W44 (W1100). The depth of built-up wide-flange 476
columns shall not exceed that for rolled shapes. Flanged cruciform columns shall not have a width 477
or depth greater than the depth allowed for rolled shapes. Built-up box columns shall not have a 478
width exceeding 33 in. (840 mm). 479
(5) There is no limit on column weight per foot. 480
(6) There are no additional requirements for column flange thickness. 481
(7) Width-to-thickness ratios for the flanges and webs of columns shall conform to the requirements 482
of the AISC Seismic Provisions. 483
(8) Lateral bracing of columns in accordance with AISC Seismic Provisions Section E3.4c1 is not a 484
requirement if the beam is braced at the top beam flange (e.g. with a deck or slab), otherwise, 485
lateral bracing of columns shall conform to the requirements of the AISC Seismic Provisions. 486
487
488
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
489
(a) 490
491
492
493
(b) 494
Fig. 11.10. Location of beam and side plate protected zones for the field-welded connection: (a) one-495
sided connection; (b) two-sided connection. 496
497
498
(a) 499
500
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501
(b) 502
Fig. 11.11. Location of beam protected zone for the field-bolted connection: (a) one-sided connection; 503 (b) two-sided connection. 504
3. Connection Limitations 505
The connection shall satisfy the following limitations: 506
(1) All connection steel plates, which consist of side plates, cover plates, horizontal shear plates, and 507
vertical shear elements (if applicable) must be fabricated from structural steel that complies with 508
ASTM A572/A572M Grade 50 (Grade 345). 509
Exception: The vertical shear element as defined in Section 11.6 may be fabricated using ASTM 510 A36/A36M material. 511
(2) The extension of the side plates beyond the face of the column shall be within the range of 0.65d 512
to 1.0d for the field-welded connection and 0.65d to 1.7d for the field-bolted connection, where d 513
is the nominal depth of the beam. 514
(3) The protected zone of the connection in the side plates shall consist of a portion of each side plate 515
that is 6-in. (150 mm) high and starts at the inside face of the flange of a wide-flange or HSS 516
column and ends either at the end of the gap (field-welded connection) or the edge of the first bolt 517
hole (field-bolted connection) as shown in Figures 11.10 and 11.11. 518
11.4. COLUMN-BEAM RELATIONSHIP LIMITATIONS 519
Beam-to-column connections shall satisfy the following limitations: 520
(1) Beam flange width and thickness for rolled, built-up, and HSS shapes shall satisfy the following 521
equations for geometric compatibility (see Figure 11.12): 522
(a) Field-welded connection 523
bbf + 1.1tbf + 1/2 in. ≤ bcf (11.4-1a) 524
bbf + 1.1tbf + 12 mm ≤ bcf (11.4-1aM) 525
(b) Field-bolted connection 526
bbf + 1.0 in. ≤ bcf (11.4-1b) 527
bbf + 25 mm ≤ bcf (11.4-1bM) 528
529
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where 530 bbf = width of beam flange, in. (mm) 531 bcf = width of column flange, in. (mm) 532 tbf = thickness of beam flange, in. (mm) 533 534
Mv = additional moment due to shear amplification from the center of the 552 plastic hinge to the centerline of the column. Mv shall be computed as 553 the quantity Vhsh; where Vh is the shear at the point of theoretical 554 plastic hinging, calculated in accordance with Equation 11.4-3, and sh 555 is the distance of the assumed point of plastic hinging to the column 556 centerline, which is equal to half the depth of the column plus the 557
extension of the side plates beyond the face of column plus the 558 distance from the end of the side plates to the plastic hinge, d/3. 559
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2 pr
h gravityh
MV V
L (11.4-3) 560
where 561
Lh = distance between plastic hinge locations, in. (mm) 562 Mpr = probable maximum moment at plastic hinge, kip-in. (N-563
mm) 564 Vgravity = beam shear force resulting from 1.2D + f1L + 0.2S (where f1 565
is the load factor determined by the applicable building 566 code for live loads, but not less than 0.5), kips (N) 567
Ry = ratio of expected yield stress to specified minimum yield stress, Fy, as 568
User Note: The load combination of 1.2D + f1L + 0.2S is in 571 conformance with ASCE/SEI 7-16. When using the 2015 International 572 Building Code, a factor of 0.7 must be used in lieu of the factor of 0.2 573 for S (snow) when the roof configuration is such that it does not shed 574 snow off the structure. 575
(ii) For the uniaxial connection, the value of ∑M*pc shall be the sum of the projections of 576
the nominal flexural strengths of the column, Mpc, above and below the connection 577 joint, at the location of theoretical hinge formation in the column (i.e., one quarter the 578 column depth above and below the extreme fibers of the side plates), to the beam 579 centerline, with a reduction for the axial force in the column (Figure 11.13). The 580 nominal flexural strength of the column shall be computed as: 581
*pc ec yc uc gM Z F P A (11.4-4) 582
where 583 Fyc = minimum specified yield strength of the column at the connection, ksi 584
(MPa) 585 H = story height, in. (mm) 586 Hh = distance along column height from ¼ of column depth above top edge of 587
lower story side plates to ¼ of column depth below bottom edge of upper 588 story side plates, in. (mm) 589
Puc/Ag = ratio of column axial compressive load, calculated in accordance with load 590 and resistance factor provisions, to gross area of the column, ksi (MPa) 591
Zc = plastic section modulus of column, in.3 (mm3) 592 Zec= equivalent plastic section modulus of column, Zc, at a distance of ¼ column 593
depth from top and bottom edge of side plates, projected to beam centerline, 594 in.3 (mm3), and calculated as: 595
2
2
c cec
h h
Z H Z HZ
H H
(11.4-5) 596
597 (iii) For the biaxial connection, the value of about each axis for the square HSS or 598
built-up box columns shall be taken as: 599 600
* 0.67 1
0.85
ucpc ec ye
g ye c c
PM Z F
A F A f
(11.4-6) 601
602
where 603 Fye = actual yield strength of the column at the connection. In the absence of Fye, 604
the expected yield strength of the column (RyFyc) may be used, ksi (MPa) 605 Ag = area of the steel column, in.2 (mm2) 606 Ac = area of concrete in the column, if applicable, in.2 (mm2) 607 fc
’ = specified compressive strength of the concrete infill, if applicable, ksi 608 (MPa) 609
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610 611 For column sections with unequal properties about both axes, interaction equations 612 based on rational analysis shall be used. 613 614 USER NOTE: Guidance for checking columns subject to biaxial bending and axial 615 force is provided in AISC Seismic Provisions Section E3 Commentary. 616
617 For the purpose of satisfying strong column-weak beam requirements, it shall be 618 permitted to take the actual yield strength of the column material as the specified yield 619 strength and to consider the full composite behavior of the column for axial and 620 flexural loading action if it is filled with concrete. 621 622
(b) For IMF systems, the column-beam moment ratio shall conform to the requirements of the 623
AISC Seismic Provisions. 624
625
Fig. 11.13. Force and distance designations for calculation of column-beam moment ratios. 626
11.5. CONNECTION WELDING LIMITATIONS 627
Filler metals for the welding of beams, columns, and plates in the SidePlate connection shall meet the 628 requirements for seismic force-resisting system welds in the AISC Seismic Provisions. 629
User Note: Mechanical properties for filler metals for seismic force-resisting system welds are detailed 630 in AWS D1.8/D1.8M as referenced in the AISC Seismic Provisions. 631
The following welds are considered demand critical welds: 632
(1) Shop fillet weld {2} that connects the inside face of the side plates to the wide-flange or HSS 633 columns (see plan views in Figure 11.14, Figure 11.15 and Figure 11.16) and for biaxial cruciform 634 dual-strong axis configurations connects the outside face of the secondary side plates to the 635 outside face of primary side plates (see Figure 11.5). 636
(2) Shop fillet weld {5} that connects the edge of the beam flange to the beam flange cover plate or 637 angles (see Figures 11.17 and 11.18). 638
(3) Shop fillet weld {5a} that connects the outside face of the beam flange to the beam flange U-639 shaped cover plate or angles (see Figures 11.17 and 11.18). 640
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(4) Field fillet weld {7} that connects the beam flange cover plates to the side plates [see Figure 641 11.19(a)] or connects the HSS beam flange to the side plates. 642
(5) Fillet weld {8} that connects the top angles to the side plates in the field-bolted connection. 643
(6) Shop weld {9} that connects side plate {A} to the column face (see Figures 11.20 and 11.21). 644
(7) Shop fillet weld {10} that connects the intersecting orthogonal side plates to construct the side plate 645 interlock assembly in biaxial connections (see Figures 11.20 and 11.21). 646
11.6. CONNECTION DETAILING 647
The following designations are used herein to identify plates and welds in the SidePlate connection 648
shown in Figures 11.14 through 11.21: 649
1. Plates/Angles 650
{A} Side plate, located in a vertical plane parallel to the web(s) of the beam, connecting frame beam to 651
column. 652
{B} Beam flange cover plate bridging between side plates {A}, as applicable. 653
{C} Vertical shear plate. 654
{D} Horizontal shear plate (HSP). This element transfers horizontal shear from the top and bottom 655
edges of the side plates {A} to the web of a wide-flange column. 656
{E} Erection angle. One of the possible vertical shear elements {F}. 657
{F} Vertical shear elements (VSE). These elements, which may consist of angles and plates or bent 658
plates, transfer shear from the beam web to the outboard edge of the side plates {A}. 659
{G} Longitudinal angles welded to the side plates {A} for connecting the beam flange cover plate 660
(field-bolted connection). 661
{H} Longitudinal angles welded to the beam flange for connecting to the side plates {A} (field-bolted 662
connection). 663
{T} Horizontal plates welded to the side plates {A} for connecting the beam flange cover plate as an 664
alternative for Angle {G} (field-bolted connection). 665
2. Welds 666
{1} Shop fillet weld connecting exterior edge of side plate {A} to the horizontal shear plate {D} or to the 667
face of a built-up box column or HSS section. 668
{2} Shop fillet weld connecting inside face of side plate {A} to the tip of the column flange or to the 669
corner of an HSS or built-up column section; and for biaxial dual-strong axis configurations 670
connects outside face of secondary side plates to outside face of primary side plates. 671
{3} Shop fillet weld connecting horizontal shear plate {D} to wide-flange column web. Weld {3} is also 672
used at the column flanges where required to resist orthogonal loads through the connection due to 673
collectors, chords, or cantilevers. 674
{4} Shop fillet weld connecting vertical shear elements {F} to the beam web, and where applicable, the 675
vertical shear plate {C} to the erection angle {E}. 676
{5} Shop fillet weld connecting beam flange tip to cover plate {B}/angles {H}. 677
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{5a} Shop weld connecting outside face of beam flange to cover plate {B} (or to the face of the beam 678
flange with the angles {H}). 679
{6} Field vertical fillet weld connecting vertical shear element (angle or bent plate) {F} to end of side plate 680
{A} (field-welded connection). 681
{7} Field horizontal fillet weld connecting the cover plate {B} to the side plate {A}, or connecting HSS 682
beam corners to side plates (field-welded connection). 683
{8} Shop weld connecting the longitudinal angles {G} or horizontal plate {T} to the side plate {A} (field-684
bolted connection). 685
{9} Shop fillet weld connecting side plate {A} to HSS/built-up box column in biaxial configuration. 686
{10} Shop weld connecting the intersecting orthogonal side plates to construct the side plate interlock 687
assembly. 688
Figure 11.14 shows the connection detailing for a one-sided moment connection configuration in which 689 one beam frames into a column (A-type). Figure 11.15 shows the connection detailing for a two-sided 690 moment connection configuration in which the beams are identical (B-type). Figure 11.16 shows the 691 connection detailing for a two-sided moment connection configuration in which the beams differ in 692 depth (C-type). Figures 11.17 and 11.18 show the beam assembly shop detail for the field-welded and 693 field-bolted connections, respectively. Figure 11.19 shows the beam-to-side-plate field erection detail. 694 If two beams frame into a column to form a corner, the connection detailing is referred to as a D-type 695
(not shown). The connection detailing for a three-sided and four-sided moment connection 696 configuration is referred to as an E-type and F-series, respectively (not shown). Figures 11.14, 11.15, 697 and 11.16 show the field-welded connection. The same details are applicable to the field-bolted 698 connection by using the beam end details for the field-bolted connection. 699
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
712
Fig. 11.17. Beam shop detail (field-welded). 713
714
715
Fig. 11.18. Beam shop detail, field-bolted standard (configuration A) 716
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(a)
(b)
Fig. 11.19. Beam-to-SidePlate field erection detail: (a) elevation and section B-B, field welded; (b) 717 elevation and section B-B, field-bolted standard (configuration A). 718
719
(a) (b)
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(1) Bolts shall be arranged symmetrically about the axis of the beam. 727
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(2) Types of holes: 728
(a) Standard holes shall be used in the horizontal angles {G} and {H}. 729
(b) Either standard or oversized holes shall be used in the side plates and cover plates. 730
(c) Either standard or short-slotted holes (with the slot parallel to the beam axis) shall be used in 731
the angle of the vertical shear element (VSE), if applicable. 732
(3) Bolt holes in the side plates, cover plates, and longitudinal angles shall be made by drilling, 733
thermal cutting, punching, or sub-punching and reaming. Bolt hole fabrication using thermal 734
cutting is not permitted for plates thicker than 2 in. (50mm). 735
(4) All bolts shall be installed as pretensioned high-strength bolts. 736
(5) Bolts shall be pretensioned high-strength bolts conforming to ASTM F3125 grade A490, A490M, 737
or F2280 or ASTM F3148 (fixed spline assemblies). Bolt diameter is limited to 1-1/2 in. (38 mm) 738
maximum. 739
(6) The use of shim plates between the side plates and the cover plate or angles is permitted at either 740
or both locations, subject to the limitations of the RCSC Specification. 741
(7) Faying surfaces of side plates, cover plates, and angles shall have a Class A slip coefficient or 742
higher. 743
User Note: The use of oversized holes in the side plates and cover plates with pretensioned bolts 744
that are not designed as slip critical is permitted, consistent with AISC Seismic Provisions 745
Section D2.2. Although standard holes are permitted in the side plate and cover plate, their use 746
may result in field modifications to accommodate erection tolerances. 747
748
11.7. DESIGN PROCEDURE 749
Step 1. Choose trial frame beam and column section combinations that satisfy geometric compatibility 750 based on Equation 11.4-1 or 11.4-1M. For SMF systems, check that the section combinations satisfy 751 the preliminary column-beam moment ratio given by: 752
∑ (FycZxc) > 1.7 ∑ (FybZxb) (11.7-1) 753
where 754 Fyb =specified minimum yield stress of beam, ksi (MPa) 755 Fyc = specified minimum yield stress of column, ksi (MPa) 756 Zxb = plastic section modulus of beam, in.3 (mm3) 757
Zxc = plastic section modulus of column, in.3 (mm3) 758
Step 2. Approximate the effects on global frame performance of the increase in lateral stiffness and 759 strength of the SidePlate moment connection due to beam hinge location and side plate stiffening in the 760 mathematical elastic steel frame computer model by using a 100% rigid offset in the panel zone, and by 761 increasing the moment of inertia, elastic section modulus, and plastic section modulus of the beam to 762 approximately three times that of the beam for a distance of approximately 77% of the beam depth 763 beyond the column face (approximately equal to the extension of the side plate beyond the face of the 764 column), illustrated in Figure 11.22. 765
SMF beams that have a combination of shallow depth and heavy weight (i.e., beams with a relatively 766 large flange area such as those found in the widest flange series of a particular nominal beam depth) 767 require that the extension of the side plate {A} be increased up to the nominal depth of the beam, d, for 768 field-welded connections and 1.7d for field-bolted connections. 769
User Note: This increase in extension of side plate {A} of the field-welded connection lengthens fillet 770 weld {7}, thus limiting the extremes in the size of fillet weld {7}. Regardless of the extension of the 771
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side plate {A}, the plastic hinge occurs at a distance of d/3 and d/6 from the end of the side plates for 772 the field-welded and field bolted connections, respectively. 773
Step 3. Confirm that the frame beams and columns satisfy all applicable building code requirements, 774 including, but not limited to, stress or strength checks and design story drift checks. 775
Step 4. Confirm that the frame beam and column sizes comply with prequalification limitations in 776 accordance with Section 11.3. 777
778
779
Fig. 11.22. Modeling of component stiffness for linear-elastic analysis. 780
Step 5. Upon completion of the preliminary and/or final selection of lateral load-resisting frame beam 781 and column member sizes using SidePlate connection technology, the engineer of record submits a 782 computer model to SidePlate Systems, Inc. In addition, the engineer of record shall submit the 783 following additional information, as applicable: 784 Vgravity = factored gravity shear in moment frame beam resulting from the load combination of 1.2D 785
+ f1L + 0.2S (where f1 is the load factor determined by the applicable building code for live 786 loads, but not less than 0.5), kips (N) 787
User Note: The load combination of 1.2D + f1L + 0.2S is in conformance with ASCE/SEI 788
7-16. When using the 2015 International Building Code, a factor of 0.7 must be used in lieu 789 of the factor of 0.2 for S (snow) when the roof configuration is such that it does not shed 790 snow off of the structure. 791
(a) Factored gravity shear loads, V1 and/or V2, from gravity beams that are not in the plane of the 792
moment frame, but connect to the exterior face of the side plate(s), 793
where 794
V1, V2 = beam shear force resulting from the load combination of 1.2D + f1L + 0.2S (where f1 is 795 the load factor determined by the applicable building code for live loads, but not less 796 than 0.5), kips (N) 797
798 (b) Factored gravity loads, Mcant and Vcant, from cantilever gravity beams that are not in the plane of 799
the moment frame, but connect to the exterior face of the side plate(s), 800
where 801
Mcant = cantilever beam moment resulting from code applicable load combinations, kip-in. (N-802 mm) 803
804
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Vcant = cantilever beam shear force resulting from code applicable load combinations, kips (N) 805
User Note: Code applicable load combinations may need to include the following when looking 806
at cantilever beams: 1.2D + f1L + 0.2S and (1.2 + 0.2SDS)D + QE + f1L + 0.2S, which are in 807
conformance with ASCE/SEI 7-16. When using the 2015 International Building Code, a factor 808 of 0.7 must be used in lieu of the factor of 0.2 for S (snow) when the roof configuration is such 809 that it does not shed snow off of the structure. 810
(c) Perpendicular amplified seismic lateral drag or chord axial forces, A, transferred through the 811
SidePlate connection. 812
A = amplified seismic drag or chord force resulting from the applicable building code, kips (N) 813
User Note: Where linear-elastic analysis is used to determine perpendicular collector or chord 814 forces used to design the SidePlate connection, such forces should include the applicable load 815 combinations specified by the building code, including consideration of the amplified seismic 816 load, Ωo. Where nonlinear analysis or capacity design is used, collector or chord forces 817 determined from the analysis are used directly, without consideration of additional amplified 818 seismic load. 819
(d) In-plane factored chord axial forces, A||, transferred along the frame beam through the SidePlate 820
connection. 821
A|| = amplified seismic chord force resulting from applicable building code, kips (N) 822
Step 6. Upon completion of the mathematical model review and after additional information has been 823 supplied by the engineer of record, SidePlate engineers provide project-specific connection designs. 824 Strength demands used for the design of critical load-transfer elements (plates, welds, and columns) 825 throughout the SidePlate beam-to-column connection and the column are determined by superimposing 826 maximum probable moment, Mpr, at the known beam hinge location, then amplifying the moment 827 demand to each critical design section based on the span geometry, as shown in Figure 11.9, and 828 including additional moment due to gravity loads. For each of the design elements of the connection, 829
the moment demand is calculated using Equation 11.7-2, and the associated shear demand is calculated 830 as: 831
group pr uM M V x (11.7-2) 832
where 833
Cpr = connection-specific factor to account for peak connection strength, including strain 834 hardening, local restraint, additional reinforcement, and other connection conditions. The 835 equation used in the calculation of Cpr is provided by SidePlate as part of the connection 836 design. 837
User Note: In practice, the value of Cpr for SidePlate connections as determined from 838 testing and nonlinear analysis ranges from 1.15 to 1.35. 839
Fy = specified minimum yield stress of yielding element, ksi (MPa) 840 Lh = distance between plastic hinge locations, in. (mm) 841
Mgroup = maximum probable moment demand at any connection element, kip-in. (N-mm) 842 Mpr = maximum probable moment at the plastic hinge as defined in Section 2.4.3, kip-in. (N-mm), 843
calculated as: 844
pr pr y y xM C R F Z (11.7-3) 845
846 Ry = ratio of expected yield stress to specified minimum yield stress, Fy 847 Vgravity = gravity beam shear resulting from 1.2D + f1L + 0.2S (where f1 is the load factor determined 848
by the applicable building code for live loads, but not less than 0.5), kips (N) 849 Vu = maximum shear demand from probable maximum moment and factored gravity loads, kips 850
(N), calculated as: 851
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2 pr
u gravityh
MV V
L (11.7-4) 852
Zx = plastic section modulus of beam about x-axis, in.3 (mm3) 853
x = distance from plastic hinge location to centroid of connection element, in. (mm) 854
Step 7. SidePlate designs all connection elements according to the proprietary connection design 855 procedures contained in the SidePlate Connection Design Software (version 16 for field-welded and 856 version 17 for field-bolted connections). The version is clearly indicated on each page of calculations. 857 The final design includes structural notes and details for the connections. 858
User Note: The procedure uses an ultimate strength design approach to size plates and welds, 859 incorporating strength, plasticity, and fracture limits. For welds, an ultimate strength analysis 860 incorporating the instantaneous center of rotation may be used as described in AISC Steel Construction 861
Manual Section J2.4b. For bolt design, eccentric bolt group design methodology incorporating ultimate 862 strength of the bolts is used. Refer to the Commentary for an in-depth discussion of the process. 863
In addition to the column web panel zone strength requirements, the column web shear strength shall 864 be sufficient to resist the shear loads transferred at the top and bottom of the side plates. The design 865 shear strength of the column web shall be determined in accordance with AISC Specification Section 866 G2.1. 867
Step 8. Engineer of record reviews SidePlate calculations and drawings to ensure that all project-868 specific connection designs have incorporated the information provided in Step 5. 869
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CHAPTER 12 870
SIMPSON STRONG-TIE STRONG 871
FRAME MOMENT CONNECTION 872
873
The user’s attention is called to the fact that compliance with this chapter of the 874 standard requires use of an invention covered by patent rights.* By publication of this 875
standard, no position is taken with respect to the validity of any claim(s) or of any 876 patent rights in connection therewith. The patent holder has filed a statement of 877 willingness to grant a license under these rights on reasonable and nondiscriminatory 878 terms and conditions to applicants desiring to obtain such a license. The statement 879 may be obtained from the standard’s developer. 880
12.1. GENERAL 881
The Simpson Strong-Tie® (SST) Strong Frame® moment connection is a partially 882 restrained (Type PR) connection that uses a modified shear plate connection (single-883 plate shear connection) for shear transfer and a modified T-stub or end-plate 884
connection (the Yield-Link® structural fuse) for moment transfer, as shown in Figure 885 12.1. The central bolt in the vertical line of bolts in the shear plate uses a standard bolt 886 hole and defines the center of rotation for the joint, while the rest of the bolt holes are 887 slotted to allow rotation of the beam around the central bolt. Matching holes in the 888 beam web are all standard holes. This prevents moment transfer through the shear 889 plate connection. The central bolt and all horizontally slotted shear plate bolts 890 participate in shear resistance. The central bolt is also designed, together with the 891 additional horizontally aligned bolts, to resist the axial force in the beam at the 892
connection. The modified T-stub and end-plate link connections, which bolt to both 893 the beam flange and column flange, are configured as yielding links and contain a 894 reduced yielding area in the stem of the link that is prevented from buckling in 895 compression via a separate buckling restraint plate. The connection is based on a 896 capacity-based design approach, wherein connection response remains elastic under 897 factored load combinations, and seismic inelastic rotation demand is confined 898 predominantly within the connection with little, if any, inelastic behavior expected 899 from the members. 900
901
12.2. SYSTEMS 902
The Simpson Strong-Tie connection is prequalified for use in special moment frame 903 (SMF) and intermediate moment frame (IMF) systems within the limits of these 904 provisions. 905
Exception: Simpson Strong-Tie connections with concrete structural slabs are 906 prequalified only if the concrete structural slab is kept at least 1 in. (25 mm) from both 907 sides of both column flanges. It is permitted to place compressible material in the gap 908 between the column flanges and the concrete structural slab. 909
910
911 912 913 914 915 *The proprietary design of the Yield-Link structural fuse and its use in moment-resisting connections is 916
protected under U.S. Patent Nos: 8,375,652; 8,001,734; 8,763,310; Japan Pat. No. 5398980; and 917
China Pat. No. ZL200710301531.4. Other U.S and foreign patent protection are pending. 918
919
920
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921
922
923
(a) T-stub Yield-Link 924
925
926
(b) End-plate Yield-Link 927
Fig. 12.1. Simpson Strong-Tie Strong Frame moment connection. 928
929
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
930
12.3. PREQUALIFICATION LIMITS 931
1. Beam Limitations 932
Beams shall satisfy the following limitations: 933
(1) Beams shall be rolled wide-flange or welded built-up I-shaped members. 934
(2) Beam depth is limited to: 935
(a) For T-stub Yield Links, a maximum of W36 (W920) for rolled shapes. 936
Beam depth for built-up members shall not exceed the maximum depth of 937
the permitted W36 (W920) shapes. 938
(b) For end-plate Yield-Links, minimum W8 to maximum W12 shapes. Beam 939
depth for built-up members shall comply with the minimum and maximum 940
depths permitted for W8 to W12 sections. 941
(3) There are no limits on the beam web width-to-thickness ratio beyond those listed 942
in the AISC Specification. The beam flange width-to-thickness ratio shall not 943
exceed r per Table B4.1b of the AISC Specification. Flange thickness shall be 944
designed in accordance with Step 10 in the Design Procedure and shall not be 945
less than 0.40 in. (10 mm). 946
(4) Lateral bracing of beams and joints: there are no requirements for stability 947
bracing of beams or joints beyond those in the AISC Specification. 948
(5) The protected zone shall consist of the Yield-Links, the shear plate, and the 949
portions of the beam in contact with the Yield-Links and shear plate. 950
User Note: Limits on beam weight and span-to-depth ratio are not required for 951 the SST moment connection because plastic hinging in the connection occurs 952
solely within the Yield-Links. Span-to-depth ratio is typically limited to control 953 moment gradient and beam shear, both of which are limited by the shear plate 954 connection within the design procedure. 955
2. Column Limitations 956
Columns shall satisfy the following limitations: 957 958 (1) Columns shall be any of the rolled or built-up I-shaped members permitted in 959
Section 2.3. 960
(2) The beam shall be connected to the flange of the column. 961
(3) Column depth is limited to a maximum of W36 (W920) for rolled shapes. 962
Column depth for built-up members shall not exceed the maximum depth 963
permitted for W36 (W920) shapes. 964
(4) There is no limit on the weight per foot of columns. 965
(5) There are no additional requirements for flange thickness. 966
(6) Column width-to-thickness ratios shall comply with the following: 967
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(a) Where column-to-foundation connections are designed to restrain column 968
end rotation, column width-to-thickness ratios shall comply with AISC 969
Seismic Provisions Table D1.1 for highly ductile members within the first 970
story. 971
(b) At other locations and for other conditions, column width-to-thickness 972
ratios shall comply with the AISC Specification. 973
(7) Lateral bracing of columns shall be provided in accordance with the AISC 974
Seismic Provisions. 975
Exception: When columns are designed in accordance with Section 12.9 and 976 maximum nominal flexural strength, Mn, outside the panel zone is limited such 977 that Mn ≤ FySx, it is permitted that bracing be provided at the level of the top 978 flange of the beam only. 979
3. Bolting Limitations 980
Bolts shall conform to the requirements of Chapter 4. 981
Exceptions: 982
983
(1) The following connections shall be made with ASTM F3125 Grade A325 or 984
A325M bolts installed either as snug-tight or pretensioned, except as noted. It 985
shall be permitted to use ASTM F3125 Grade F1852 bolts for pretensioned 986
applications. 987
(a) Yield-Link flange- or end plate-to-column flange bolts 988
surface preparation between the Yield-Link stem and beam flange shall not be 993
required, but faying surfaces shall not be painted. 994
12.4. COLUMN-BEAM RELATIONSHIP LIMITATIONS 995
Beam connection-to-column connections shall satisfy the following limitations: 996
(1) Panel zones shall conform to the requirements of the AISC Specification. 997
(2) Column-beam connection moment ratios shall be limited as follows: 998
(a) For SMF systems, the column-beam connection moment ratio shall 999
conform to the requirements of the AISC Seismic Provisions. The value 1000
of*pbM shall be taken equal to pr uvM M , where Mpr is 1001
calculated according to Equation 12.9-27, and where Muv is the additional 1002
moment due to shear amplification from the center of the vertical line of 1003
bolts in the shear plate to the centerline of the column. Muv is calculated as 1004
2u cV a d , where Vu is the shear at the shear-plate connection 1005
calculated in Section 12.9, Step 12, a is the distance from the centerline of 1006
the shear-plate shear bolts to the face of the column as shown in Figure 1007
12.3(c), and dc is the depth of the column. 1008
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
(b) For IMF systems, the column-beam moment ratio shall conform to the 1009
requirements of the AISC Seismic Provisions. 1010
12.5. CONTINUITY PLATES 1011
Continuity plates shall satisfy the following limitations: 1012
(1) The need for continuity plates shall be determined in accordance with Section 1013
12.9. 1014
(2) Where required, design of continuity plates shall be in accordance with the AISC 1015
Specification. 1016
(3) Continuity plates may be welded to the column flange and column web with 1017
Yield-Link flange-to-stem connections may be CJP groove welds or double-sided 1020 fillet welds. 1021
(1) CJP groove welds shall conform to the requirements of demand critical welds in 1022
the AISC Seismic Provisions. 1023
(2) Double-sided fillet welds shall be designed to develop the tensile strength of the 1024
unreduced Yield-Link stem at the column side, bcol-side, and shall be demand 1025
critical. 1026
12.7. FABRICATION OF YIELD-LINK CUTS 1027
The reduced section of the Yield-Link shall be cut using the following methods: laser, 1028 plasma or water-jet method. Maximum roughness of the cut surface shall be 250 µ-in. 1029 (6.5 microns) in accordance with ASME B46.1. All transitions between the reduced 1030 section of the Yield-Link and the nonreduced sections of the Yield-Link shall utilize a 1031
smooth radius, R, as shown in Figure 12.2(a), where R equals the thickness of the link 1032 stem, tstem. 1033
Cutting tolerance at the reduced section shall be plus or minus 1/16 in. (2 mm) from 1034 the theoretical cut line. 1035
1036
1037
(a) Yield-Link plan view 1038
1039
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
1040
(b) Yield-Link elevation view 1041
1042
1043
(c) Yield-Link flange view 1044
Fig. 12.2. Yield-Link geometries. 1045
1046
12.8. CONNECTION DETAILING 1047
1. Beam Coping 1048
Beams shall be coped in accordance with Figure 12.3(a). 1049
2. Yield-Links 1050
Yield-Links shall conform to the requirements of Figures 12.2 and 12.3, and shall be 1051 fabricated using ASTM A572 Grade 50 material or rolled sections conforming to the 1052 ASTM A992 or ASTM A913 Grade 50 specification. Each pair of Yield-Link stems 1053 at a connection shall be cut from the same heat of material. Minimum Yield-Link 1054 stem thickness shall be 0.50 in. (13 mm) and maximum Yield-Link stem thickness 1055 shall be 1.0 in. (25 mm), with a thickness tolerance in accordance with ASTM A6. 1056 Yield-Link flange edge distances, Lv and Lh, shall conform to AISC Specification 1057
Tables J3.4 or J3.4M. 1058
3. Shear-Plate Connection Bolts 1059
The shear-plate connection bolts shall be designed to resist the required axial and 1060 shear forces, see Figure 12.1 and Section 12.9, Step 15. 1061
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4. Shear-Plate Shear Connection Welds 1062
The single-shear plate connection shall be welded to the column flange or end plate 1063 using double-sided fillet welds, PJP welds, or CJP welds, sized in accordance with 1064 Section 12.9, Step 15.4. 1065
5. Bolt Hole Requirements 1066
(a) Standard bolt holes shall be provided in the beam flanges and beam webs. 1067 Oversized holes or vertical slots are permitted in the column flanges with T-stub 1068
Yield-Links. Standard size bolt holes shall be used in the end plate and column 1069 flanges when using end-plate Yield-Links. 1070
(b) The central bolt hole in the shear plate shall be a standard hole. Remaining bolt 1071 holes for bolts resisting shear and axial forces shall be slotted to accommodate a 1072 connection rotation of at least 0.07 rad. 1073
6. Buckling Restraint Assembly 1074
The buckling restraint assembly consists of the buckling restraint plate, the buckling 1075 restraint spacer plate, and the buckling restraint bolts, and shall conform to the 1076 requirements of Figure 12.3. Design of the buckling restraint plate assembly shall be 1077
in accordance with Section 12.9, Step 10. The buckling restraint plate shall be a 1078 minimum of 0.875-in. (22 mm) thick, with a specified minimum yield stress Fy ≥ 50 1079 ksi (345 MPa). The buckling restraint plate shall extend from the centerline of the 1080 vertical shear bolt holes to the end of the cut region of the Yield-Link plate. The 1081 buckling restraint spacer plate shall have the same thickness as the Yield-Link stem, 1082 with a specified minimum yield stress Fy ≥ 36 ksi (250 MPa). Buckling restraint bolts 1083 shall have a minimum diameter of 0.625 in. (16 mm). 1084
7. Shims 1085
The use of finger shims at the T-stub or end-plate Yield-Link flange-to-column flange 1086
is permitted, subjected to the limitations of the RCSC Specification. 1087
1088
1089
(a) Beam coping 1090
1091
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
12.9. DESIGN PROCEDURE 1101
Step 1. Choose trial values for the beam sections and column sections subject to the 1102
prequalification limits of Section 12.3 assuming fully restrained beam-to-column 1103 connections and all load combinations specified by the applicable building code. 1104 Estimate the design story drift for compliance with the applicable limits specified by 1105 the applicable building code as 1.2 times larger than the value calculated assuming 1106 fully restrained connections. 1107
Step 2. Check the strength and deflection of the beam assuming the beam is simply 1108 supported between shear-plate connections. Check the beam strength for the 1109 applicable vertical load combinations of the applicable building code. Check that the 1110 deflection of the beam under dead and live loads is less than Lh/360, where Lh is the 1111 length of the beam between the center of the shear-plate shear bolts at each end of the 1112 beam. 1113
User Note: The deflection check serves to estimate beam stiffness needed to limit 1114 member end rotations. Other values may be acceptable. 1115
Step 3. Estimate the required Yield-Link yield strength from Step 1. 1116
y link u bP M d (12.9-1) 1117
y link y link y linkA P F (12.9-2) 1118
1119
where 1120
y linkA = estimated required Yield-Link yield area, in.2 (mm2) 1121
y linkF = specified minimum yield stress of Yield-Link stem material, ksi (MPa) 1122
Mu = moment demand from elastic analysis assuming fully restrained 1123 connections, kip-in. (N-mm) 1124
User Note: Try setting bcol-side and bbm-side equal to the minimum of beam flange 1132 width and column flange width, respectively. 1133
Step 4.2. Nonreduced Yield-Link stem length at column side, Lcol-side, shall 1134 have a maximum length equal to 5 in. (127 mm) and a minimum length equal 1135 to a − tflange + 1 in. (a − tflange + 25 mm). See Figure 12.3(c). 1136
Step 5. Determine the width of the yielding section of the Yield-Link stem, 1137 byield, where the thickness of the Yield-Link stem, tstem, shall be taken as 1/2 in. (13 1138 mm) minimum and 1 in. (25 mm) maximum. 1139
byield,req’d ≥ y link stemA t (12.9-3) 1140
The value of byield,req’d shall not exceed the least of 0.5bcol-side, 0.5bbm-side, or 6 in. (150 1141 mm). 1142
Step 6. Determine the minimum yielding length of the Yield-Link stem, Ly-link, such 1143 that the axial strain in the straight portion of the Yield-Link is less than or equal to 1144 0.085 in./in. at 0.05 rad of connection rotation. 1145
0.05
20.085 2
stemy link
d tL R
(12.9-4) 1146
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Step 7. Compute the expected yield strength and probable maximum tensile strength 1147 of the Yield-Link. 1148
Pye-link = Ay-link Ry Fy-link (12.9-5) 1149
Pr-link = Ay-link Rt Fu-link (12.9-6) 1150
where 1151
Ay-link = area of reduced Yield-Link section (byield)(tstem ), in.2 (mm2) 1152
Rt = ratio of expected tensile strength to specified minimum tensile strength, 1154 Fu, as related to overstrength in material yield stress, Ry; taken as 1.2 for 1155 Yield-Link stem material 1156
Ry = ratio of the expected yield stress to specified minimum yield stress, Fy; 1157 taken as 1.1 for Yield-Link stem material 1158
Step 8. Determine the nonreduced width, bbm-side, and length, Lbm-side, at beam side of 1159
the Yield-Link using Pr-link from Step 7. 1160
Step 8.1. Design bolts for shear transfer between the Yield-Link stem and the 1161 beam flange according to the AISC Specification and determine the bolt 1162 diameter, db-stem. 1163
Step 8.2. Determine the nonreduced width of the Yield-Link stem on the beam 1164 side, bbm-side. 1165
User Note: Try setting bbm-side equal to bcol-side from Step 4.1. 1166
Step 8.3. Determine the nonreduced length of the Yield-Link stem at beam 1167
side, Lbm-side. 1168
1bm side c rows stem bL s n s s (12.9-7) 1169
where 1170 nrows= number of rows of bolts from Step 8.1. 1171
sb = distance from center of last row of bolts to beam-side end of Yield-1172 Link stem, from Table J3.4 of the AISC Specification, in. (mm) 1173
sc = distance from center of first row of bolts to reduced section of 1174 Yield-Link, from Table J3.4 of the AISC Specification, in. (mm) 1175
sstem = spacing between rows of bolts for Yield-Link stem-to-beam flange 1176 connection, minimum 2⅔db-stem, in. (mm) 1177
Step 8.4. Check the Yield-Link stem at the beam side for tensile yielding, 1178 tensile rupture, block shear rupture, and bolt bearing (where deformation at the 1179 hole is a design consideration) according to the AISC Specification. Check the 1180 beam flange for bolt bearing (where deformation at the bolt hole is a design 1181 consideration) and block shear rupture according to the AISC Specification. 1182
1183
Step 9. Design the Yield-Link flange-to-column flange or end-plate connection using 1184 Pr-link from Step 7. 1185
Step 9.1. Design bolts for tension force transfer between the Yield-Link flange 1186 or end plate and the column flange according to the AISC Specification and 1187 determine the diameter of the flange bolts, db-flange. The required tension force 1188 per bolt in the Yield-Link flange-to-column flange connection, rt, is: 1189
For T-stub Yield-Link: 1190
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
4
r linkt
Pr
(12.9-8) 1191
For end-plate Yield-Link: 1192
1 12 2
pr ut
o
M v ar
h h h
(12.9-9) 1193
1194
where ho and h1 are defined in Table 6.2 of Chapter 6 Bolted Unstiffened and 1195 Stiffened Extended End-Plate Moment Connections, 1196
1197
Step 9.1a: For end-plate Yield-Link connections, check bolt shear rupture 1198 strength of the connection provided by bolts at the compression flange only 1199
using Equation 6.8-11 in Chapter 6. 1200
1201
Step 9.2. Determine the thickness of the Yield-Link flange, tflange, required to 1202 prevent prying action. 1203
4 t
flanged u
r bt
p F
(12.9-10) 1204
- 2b flangeb b d (12.9-11) 1205
where 1206
b = vertical distance from centerline of bolts in Yield-Link flange to 1207 face of Yield-Link stem, in. (mm) 1208
db-flange= diameter of bolt connecting Yield-Link flange and column flange, 1209 in. (mm) 1210
p = minimum of bflange/2 or sflange, in. (mm) 1211 1212
Step 9.3. Check the thickness of the Yield-Link flange, tflange, for shear yielding 1213 and shear rupture according to the AISC Specification. 1214
1215
Step 9.3a. For end-plate Yield-Link connections, check shear yielding and 1216 shear rupture of the extended portion of the end plate using Equations 6.8-7 and 1217 6.8-8 in Chapter 6. 1218
1219
Step 9.3b. For end-plate Yield-Link connections, check bolt bearing/tearout 1220 failure of the end plate and column flange using Equation 6.8-12 in Chapter 6. 1221
1222
Step 9.4. Design the stem-to-flange weld of the Yield-Link as either a CJP 1223 weld or a double-sided fillet weld that will develop the tensile strength of the 1224 Yield-Link at the column side, Pr-weld: 1225
r weld col side stem t u linkP b t R F (12.9-12) 1226
Step 10. Design the buckling restraint assembly 1227
Step 10.1. Determine the minimum thickness of the buckling restraint plate 1228 (BRP) to prevent yielding during compression of the link stem. BRP thickness 1229 shall not be less than 0.875in.: 1230
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
0.51
cant r linkBRP min
y BRP y BRP n
L Pt
F R b
(12.9-13) 1231
where 1232 Fy-BRP = specified minimum yield strength of BRP material, ksi (MPa) 1233
Lcant = lever arm from start of reduced region to edge of spacer plate bolt 1234
hole, plus plate stretch from 0.05 rad of rotation, in. (mm). See 1235
Figure 12.4(a). 1236
Ry-BRP = ratio of the expected yield stress to specified minimum yield stress, 1237
Fy-BRP, taken as 1.1 for BRP material 1238
bn = net width of BRP, in. (mm) 1239
Step 10.2. Determine minimum beam flange thickness to prevent yielding and 1240 BRP bolt induced prying. Minimum flange thickness shall not be less than 0.4 1241 in. 1242
4 uxbf min
d e ub
b Tt
p F
(12.9-14) 1243
where 1244
Fub = specified minimum tensile strength of the beam material, ksi (MPa) 1245
Tux = vertical thrust force transferred by one restraint bolt, kips (kN) 1246
= BRP bolts
Q
n
(12.9-15) 1247
b = the distance from the bolt centerline to the beam centerline, in. (mm) 1248
pe = effective (tributary) length per bolt from the yield line pattern, in. 1249 (mm) 1250
1251
where 1252
Q = total vertical thrust force on the beam flange, kips (kN) 1253
=NdesignQi (12.9-15) 1254
nBRP-bolts = total number of BRP bolts 1255
Ndesign = the number of contact points between the reduced region of the link 1256
stem and the BRP or beam flange (rounded to the nearest integer) 1257
Iy = weak axis moment of inertia of reduced link stem region, in.4 (mm4) 1261
g = gap increase due to transverse shortening of the Yield-Link thickness, in. 1262 (mm) 1263
= 0.25 target stemt (12.9-18) 1264
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
0.042
2
stem
targety link
d t
L R
(12.9-19) 1265
4 r linki
o
gPQ
l
(12.9-20) 1266
Step 10.3. Determine the BRP bolt size and quantity 1267
Design BRP bolts for tension + shear interaction for out-of-plane thrust 1268 according to the AISC Specification, where Tux is from Step 10.2 and the shear 1269
is: 1270
ux k uxV T (12.9-21) 1271
where kis the coefficient of dry kinetic friction, taken as 0.3. 1272
Check the BRP bolts for the in-plane shear thrust force exerted on each spacer 1273 plate, Vuy, in the strong axis direction: 1274
1275
1
0.5
19001 4 1.013
r linkuy
xstem
r link
PV
It
P
(12.9-22) 1276
where 1277
Ix = strong axis moment of inertia of reduced link stem region, in.4 (mm4) 1278
Step 11. Verify the elastic frame drift and connection moment demand by accounting 1285 for actual connection stiffness. 1286
Step 11.1. Model the connection using a pair of nonlinear axial links or a 1287 nonlinear rotational spring at each connection determined from the following 1288 properties: 1289
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
K1 = elastic axial stiffness contribution due to bending stiffness in 1290 Yield-Link flange, kip/in. (N/mm) 1291
=
3
3
0.75 19212
col side flange
flange
w tE
g
(12.9-23) 1292
1293 K2 = elastic axial stiffness contribution due to non-yielding section of 1294
Yield-Link, kip/in. (N/mm) 1295
= stem col side
col side c v
t b E
L s l
(12.9-24) 1296
where 1297
lv = 0 when four or fewer bolts are used at Yield-Link-to-beam 1298 connection 1299
= sstem/2 when more than four bolts are used at Yield-Link-to-1300 beam connection 1301
1302 K3 = elastic axial stiffness contribution due to yielding section of Yield-1303
1309 Mpr = probable maximum moment capacity of Yield-Link pair, kip-in. 1310
(N-mm) 1311
= ( )r link stemP d t (12.9-27) 1312
1313
Mye-link = expected yield moment of Yield-Link pair, kip-in. (N-mm) 1314
= ( )ye link stemP d t (12.9-28) 1315
1316 nbolt = number of bolts in Yield-Link stem-to-beam flange connection 1317 1318
0.04 = axial deformation in Yield-Link at a connection rotation of 0.04 1319
rad 1320
= 0.04( )
2
stemd t (12.9-29) 1321
1322
0.07 = axial deformation in Yield-Link at a connection rotation of 0.07 1323
rad 1324
= 0.07( )
2
stemd t (12.9-30) 1325
1326
y = axial deformation in Yield-Link at expected yield, in. (mm) 1327
= ye link
eff
P
K
(12.9-31) 1328
1329 1330
y = connection rotation at expected yield of Yield-Link, rad 1331
= 0.5
y
stemd t
(12.9-32) 1332
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All other terms were previously defined or shown in Figure 12.2. Refer to 1333 Figure 12.5(a) for a plot of Yield-Link axial force versus Yield-Link axial 1334 deformation. Refer to Figure 12.5(b) for the moment versus rotation 1335 relationship required for the analysis and modeling of the SST moment 1336 connection. 1337
Step 11.2. Considering the applicable drift limit and all applicable load 1338 combinations specified by the applicable building code, but not including the 1339 overstrength seismic load, verify that: 1340
(a) The connection moment demand, Mu, is less than or equal to the 1341
connection available flexural strength, Mn, taking as 0.90 and Mn as 1342
Mye-link/Ry. 1343
(b) The drift complies with applicable limits. 1344
Adjust connection stiffness and/or number of connections as needed to comply. 1345
Step 12. Determine the required shear strength, Vu, of the beam and beam web-to-1346 column flange connection using: 1347
2 pr
u gravityh
MV V
L (12.9-33) 1348
where 1349 Lh = horizontal distance between centerlines of the shear bolts in shear plate at 1350
each end of beam, in. (mm) 1351 Vgravity = shear force in the beam, kips (N), resulting from 1.2D + f1L + 0.2S (where 1352
f1 is the load factor determined by the applicable building code for live 1353 loads, but not less than 0.5). The shear force at the shear plate connection 1354 shall be determined from a free-body diagram of the portion of the beam 1355 between the shear plate connections. 1356
User Note: The load combination of 1.2D + f1L + 0.2S is in conformance with 1357 ASCE/SEI 7-16. When using the International Building Code, a factor of 0.7 must be 1358 used in lieu of the factor of 0.2 for S (snow) when the roof configuration is such that 1359
it does not shed snow off the structure. 1360
Step 13. Verify the beam and column sizes selected in Step 1. 1361
Step 13.1. Beams shall satisfy the AISC Specification considering: 1362
(a) Vertical load from all applicable load combinations. 1363
(b) Axial force due to seismic effects determined as the minimum of the 1364
maximum the system can deliver or as determined from the overstrength 1365
seismic load. 1366
(c) The application of Mpr at each end of the beam as required. 1367
Step 13.2. Column strength shall satisfy the AISC Specification considering 1368 loads from all applicable load combinations in the applicable building code, 1369 where the seismic effects are determined from the minimum of either the 1370 maximum the system can deliver or the overstrength seismic loads. According 1371 to Section 12.3.2(7), if column bracing is only provided at the level of the top 1372
flange of the beam, in addition to the requirements of the AISC Specification, 1373 the maximum available flexural strength of the column outside the panel zone, 1374
bMn, shall be taken as bMn ≤ bFySx, where b = 0.90. 1375
1376
1377
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1378 1379
1380
(a) Yield-Link axial force vs. Yield-Link axial deformation 1381
1382
1383
1384
(b) Connection moment vs. rotation 1385
Fig. 12.5. Simpson Strong-Tie moment connection modeling parameters. 1386 1387
Step 14. Check the column-beam relationship limitations according to Section 12.4. 1388
Step 15. Design the beam web-to-column flange connection for the following 1389
required strengths: 1390
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Mu-sp = moment in shear plate at column face, kip-in. (N-mm) 1391
= unV a 1392
Pu-sp = required axial strength of the connection, taken as the minimum of the 1393
following: 1394
(1) The maximum axial force the system can deliver. 1395
(2) The axial force calculated using the load combinations of the 1396
applicable building code, including the overstrength seismic load. 1397
1398
Vu = Vu from Step 12. 1399
a = horizontal distance from centerline of the shear bolt holes in shear plate to 1400 face of the column, in. (mm). See Figure 12.3(c). 1401
Step 15.1. 1402
(a) Calculate the maximum shear plate bolt shear, Vu-bolt,, by sizing the shear 1403
plate central bolt to take the required axial and shear load from the beam. 1404
1405
2 2
u sp uu bolt
bolt sp horz bolt sp vert
P VV
n n
(12.9-34) 1406
where 1407
nbolt-sp-horz = total number of horizontal bolts resisting axial force in the 1408
shear plate in line with the central bolt. 1409
nbolt-sp-vert = total number of vertical bolts resisting shear force in the 1410 shear plate 1411
(b) Select a bolt diameter, db-sp, that satisfies the AISC Specification. 1412
Step 15.2. Determine the shear-plate geometry required to accommodate a 1413 connection rotation of ±0.07 rad. 1414
1415
1 in. 0.14
2
bolt sp vertslot horz b sp vert
nL d s
8 (12.9-35) 1416
13 mm 0.14
2
bolt sp vertslot horz b sp vert
nL d s
(12.9-35M) 1417
in. 0.14 1slot vert b sp horz bolt sp horzL d s n 8 (12.9-36) 1418
3 mm 0.14 1slot vert b sp horz bolt sp horzL d s n (12.9-36M) 1419
where 1420 db-sp = diameter of bolts in shear plate, in. (mm) 1421 shorz = horizontal bolt spacing, in. (mm) 1422 svert = vertical bolt spacing, in. (mm) 1423 1424
Step 15.3. Check the shear plate for tension and shear yielding, tension and 1425
shear rupture, block shear, combined tension and flexural yielding at the 1426 column face, and bolt bearing, where deformation at the bolt hole is a design 1427 consideration, according to the AISC Specification. 1428
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Step 15.4. Size the weld at the shear plate-to-column flange or end-plate joint 1429 to develop the plate in shear, tension, and bending. For double fillet welds, the 1430 minimum leg size shall be 5/8tp. 1431
Step 15.5. Check the beam web for tension and shear yielding, tension and 1432 shear rupture, block shear, and bolt bearing, where deformation at the bolt hole 1433
is a design consideration, according to the AISC Specification. 1434
Step 15.6. Detail the beam flange and web cope such that the flange begins at a 1435 point aligned with the centerline of the shear-plate shear bolts. Check entering 1436 and tightening clearances as appropriate. See Figure 12.3(a). 1437
User Note: Checking the beam web for flexure at the cope is not required because the 1438 flange copes do not extend beyond the centerline of the shear bolts in the beam shear-1439 plate connection. 1440
Step 16. Check the column panel zone shear strength in accordance with the AISC 1441
Specification. The required shear strength shall be determined from the summation of 1442 the probable maximum axial strengths of the Yield-Link. Doubler plates shall be used 1443 as required. 1444
Step 17. Check the column web for the concentrated force(s) of Pr-link according to the 1445 AISC Specification. 1446
Step 18. Check the minimum column flange thickness for flexural yielding. 1447
1.11
min
prcf
d yc c
Mt
F Y
(12.9-37) 1448
where 1449 Fyc = specified minimum yield strength of column flange material, ksi (MPa) 1450 Yc = column flange yield line mechanism parameter from Table 6.5 or 6.3. For 1451
connections away from column ends, Table 6.5 shall be used. For connections 1452 at column ends, Table 6.3 shall be used. An unstiffened column flange 1453 connection at the end of a column may be used where a rational analysis 1454
demonstrates that the unstiffened column flange design flexural strength, as 1455 controlled by flexural yielding of the column flange, meets or exceeds the 1456 connection moment demand, Mpr-link. 1457
Step 19. If a continuity plate or stiffener plate is required for any of the column limit 1458 states in Steps 17 and 18, the required strength, Fsu, is 1459
Fsu = Pr-link – minimum (Rn) (12.9-38) 1460
where 1461
Rn = design strengths from Step 17, kips (N) 1462
Step 19.1. Design the continuity plate or stiffener plate according to the AISC 1463 Specification. 1464
Step 19.2. Design the stiffener-to-column web weld and the stiffener to-column 1465
flange weld according to the AISC Specification. 1466
The continuity plate or stiffener shall conform to AISC Specification Section J10.8 1467 and shall have a minimum thickness of 1/4 in. (6 mm). 1468
1469
1470
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1471
COMMENTARY 1472
On Prequalified Connections for 1473
Special and Intermediate 1474
Steel Moment Frames for 1475
Seismic Applications 1476
Supplement No. 2 1477
1478
Draft dated August 2, 2019 1479
1480
1481
1482
This Commentary is not part of ANSI/AISC 358-16, Prequalified Connections for 1483
Special and Intermediate Steel Moment Frames for Seismic Applications or AISC 358s2-1484
20, Supplement No. 2. It is included for informational purposes only. 1485
INTRODUCTION 1486
This Standard is intended to be complete for normal design usage. 1487
1488
The Commentary furnishes background information and references for the benefit of the 1489
design professional seeking further understanding of the basis, derivations, and limits of 1490
the Standard. 1491
1492
The Standard and Commentary are intended for use by design professionals with 1493
demonstrated engineering competence. 1494
1495
1496
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
CHAPTER 11 1497
SIDEPLATE MOMENT CONNECTION 1498
11.1. GENERAL 1499
The SidePlate® moment connection is a post-Northridge connection system that 1500
uses a configuration of redundant interconnecting structural plates, fillet weld 1501
groups, and high-strength pretensioned bolts (as applicable), which act as 1502
positive and discrete load transfer mechanisms to resist and transfer applied 1503
moment, shear and axial load from the connecting beam(s) to the column. This 1504
load transfer minimizes highly restrained conditions and triaxial strain 1505
concentrations that typically occur in flange-welded moment connection 1506
geometries. The connection system is used for both new and retrofit construction 1507
and for a multitude of design hazards such as earthquakes, extreme winds, and 1508
blast and progressive collapse mitigation. 1509
The wide range of applications for SidePlate connection technology, including 1510
the methodologies used in the fabrication and erection shown herein, are 1511
protected by one or more U.S. and foreign patents identified at the bottom of the 1512
first page of Chapter 11. Information on the SidePlate moment connection can 1513
be found at www.sideplate.com. SidePlate moment connections not specifically 1514
designed by SidePlate Systems Inc. shall be considered unauthorized and not 1515
prequalified and shall not be manufactured. 1516
SidePlate moment connections are designed and detailed in two types: 1517
1. Field-welded connection 1518
2. Field-bolted connection 1519
Both types are fully restrained connections of beams to columns conforming to 1520
AISC 358-16, Section 2.2. Figures 11.1 and 11.2 show the field-welded and 1521
field-bolted connections’ various configurations, respectively. The field-bolted 1522
connection is available in three configurations as shown in Figure 11.3: 1523
configuration A (standard), configuration B (narrow), and configuration C 1524
(tuck). The field-bolted connection is also referred to as the SidePlate Plus 1525
Connection. 1526
Moment frames that utilize the SidePlate connection system may be constructed 1527
using one of three methods. The most common construction method uses a full-1528
length beam for erection, namely SidePlate FRAME® configuration, as shown in 1529
Figure C-11.1(a) and (b). This method employs a full-length beam assembly 1530
consisting of the beam with shop-installed cover plates {B}/angles {H} (if 1531
required) and vertical shear elements (as applicable), which are either fillet-1532
welded or bolted near the ends of the beam depending on the type of the 1533
connection. 1534
Column assemblies are typically delivered to the job site with the horizontal 1535
shear plates {D} (as applicable) and side plates {A} shop welded to the column 1536
at the proper floor framing locations. Where built-up box columns or HSS 1537
columns are used, horizontal shear plates {D} are not required nor applicable. 1538
For the field-welded option: During frame erection, the full-length beam 1539
assemblies are lifted up in between the side plates {A} that are kept spread apart 1540
at the top edge of the side plates {A} with a temporary shop-installed spreader 1541
[Figure C-11.1(a)]. A few bolts connecting the beam’s vertical shear plates {C} 1542
(shear elements as applicable) to adjacent free ends of the side plates {A} are 1543
initially inserted to provide temporary shoring of the full-length beam assembly, 1544
after which the temporary spreader is removed. The remaining erection bolts (as 1545
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many as can be installed) are then inserted and installed to a snug-tight 1546
condition. These erection bolts can also act as a clamp to effectively close or 1547
minimize potential root gaps that might have existed between the interior face of 1548
the side plates {A} and the longitudinal edges of the top cover plate {B} while 1549
bringing the top face of the wider bottom cover plate {B} into a snug fit with the 1550
bottom edges of the side plates {A}. To complete the field assembly, four 1551
horizontal fillet welds joining the side plates {A} to the cover plates {B} are 1552
then deposited in the horizontal welding position (position 2F per AWS 1553
D1.1/D1.1M), and, when applicable, two vertical single-pass field fillet welds 1554
joining the side plates {A} to the vertical shear elements (VSE) are deposited in 1555
the vertical welding position (position 3F per AWS D1.1/D1.1M). Alternately, 1556
this can be configured such that the width of bottom cover plate {B} is equal to 1557
the width of the top cover plate {B} (i.e., both cover plates {B} fit within the 1558
separation of the side plates {A}, which would also be slightly deeper in their 1559
lengths to accommodate), in lieu of the bottom cover plate {B} being wider than 1560
the distance between side plates {A}. Note that when this option is selected by 1561
the engineer, the two bottom fillet welds connecting the bottom cover plates {B} 1562
to the side plates {A} will be deposited in the overhead welding position 1563
(position 4F per AWS D1.1/D1.1M). 1564
For the field-bolted option: During frame erection, the full-length beam 1565
assemblies are typically dropped down in between the side plates {A} that are 1566
kept spread apart at the bottom edge of the side plates {A} with a temporary 1567
shop-installed spreader [Figure C-11.1(b)]. A few bolts/fasteners assemblies 1568
connecting the beam’s top cover plate {B} (or vertical shear plates {C} as 1569
applicable) to adjacent free ends of the longitudinal angles on the side plates 1570
{A} (or the side plates {A} themselves) are initially inserted to provide 1571
temporary shoring of the full-length beam assembly, after which the temporary 1572
spreader is removed. Shim plates may be installed between the side plates {A} 1573
and the cover plate {B} or longitudinal angles if required. The remaining 1574
bolts/fastener assemblies are then inserted to a snug-tight specification in a 1575
systematic assembly within the joint, progressing from the most rigid part of the 1576
joint until the connected plies are in as firm as contact as practicable. These 1577
bolts should clamp and effectively minimize any gaps that might have existed 1578
between the interior face of the side plates {A} and the longitudinal edges of the 1579
angles and that of the interface between the bottom face of the top cover plate 1580
{B} and the top longitudinal angles {G} on the exterior face of the side plates 1581
{A} (configuration A and configuration C). If the gaps are not closed during this 1582
process, it is acceptable to use a full length shim plate up to ¼” without penalty. 1583
Gaps that cannot be closed that are greater than ¼” should be documented, and 1584
SidePlate Systems, Inc., should be contacted for further consultation. Note that 1585
the standard and tuck configurations (configuration A and configuration C) have 1586
a pair of angles attached to the bottom flange of the beam, and the narrow 1587
configuration (configuration B) consists of pairs of angles attached to both the 1588
top and bottom flanges of the beam. To complete the field assembly, the second 1589
step of the pretensioning methodology is the subsequent systematic 1590
pretensioning of all bolt/fastener assemblies; they shall progress in a similar 1591
manner as was done for the snug-tight condition, from the most rigid part of the 1592
joint that will minimize relaxation of previously pretensioned bolts. 1593
Where the full-length beam erection method (SidePlate FRAME configuration) 1594
is not used, the original SidePlate moment configuration may be used (second 1595
method). The original SidePlate moment configuration utilizes the link-beam 1596
erection method, which connects a link beam assembly to the beam stubs of two 1597
opposite column tree assemblies with field complete-joint-penetration (CJP) 1598
groove welds [Figures C-11.1(c) and 11.1(d)]. As a third method, in cases where 1599
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moment frames can be shop prefabricated and shipped to the site in one piece, 1600
no field bolting or welding is required [Figure C-11.1(e)]. 1601
The SidePlate moment connection is proportioned to develop the probable 1602
maximum flexural strength of the connected beam. Beam flexural, axial and 1603
shear forces are typically transferred to the top and bottom rectangular cover 1604
plates {B} via four shop horizontal fillet welds that connect the edges of the 1605
beam flange tips to the corresponding face of each cover plate {B} (two welds 1606
for each beam flange). When the U-shaped cover plates {B} or angles {H} are 1607
used, the same load transfer occurs via four shop horizontal fillet welds that 1608
connect the edge of the beam flange tips to the corresponding face of each cover 1609
plate {B}/angles {H} (two welds for each beam flange), as well as two shop 1610
horizontal fillet welds that connect the outside faces of the beams top and 1611
bottom flanges to the corresponding inside edge of each U-shaped cover plate 1612
{B} (for the conditions with pairs of angles {H}, there are two welds that will 1613
connect each angle to the corresponding beam flange face). These same forces 1614
are then transferred from the cover plates {B} or pairs of angles {H} to the side 1615
plates {A} via either four field horizontal fillet welds (in the field-welded 1616
connection) or four lines of bolts (in the field-bolted connection) that connect 1617
the cover plates {B} or pairs of angles {H} to the side plates {A}. The side 1618
plates {A} transfer all of the forces from the beam (including that portion of 1619
shear in the beam that is transferred from the beam’s web via vertical shear 1620
elements, as applicable, or via the cover plate {B} and pairs of angles {H}, as 1621
applicable) across the physical gap to the column via shop fillet welding (or 1622
flare bevel welding, as required) of the side plates {A} to the column flange tips 1623
(a total of four shop fillet welds; two for each side plate {A}), and to complete 1624
the weld group, there are two horizontally placed shop fillet welds at the top and 1625
bottom of each side plates {A}. These welds may attach directly to the face of a 1626
box or HSS column, or they may attach to horizontal shear plates {D} as 1627
applicable (a total of four shop fillet welds two for each side plate {A}). The 1628
horizontal shear plates {D} are, in turn, shop fillet welded to the column web 1629
and under certain conditions, also to the inside face of column flanges. 1630
1631
(a)
(b)
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Fig. C-11.1. SidePlate moment connection construction methods: (a) full-length beam 1632 erection method (SidePlate FRAME configuration, field welded); (b) full-length beam 1633 erection method (SidePlate moment standard configuration, field bolted); (c) link-beam 1634 erection method (original SidePlate moment configuration, field welded); (d) link beam-1635 to-beam stub splice detail; and (e) all shop-prefabricated single-story moment frame (no 1636
field welding); multistory frames dependent on transportation capabilities. 1637
SidePlate Systems developed, tested, and validated the SidePlate moment 1638
connection design methodology, design controls, critical design variables and 1639
analysis procedures. The development of the SidePlate FRAME configuration 1640
that employs the full-length beam erection method builds off the research and 1641
testing history of its proven predecessor—the original configuration and its 1642
subsequent refinements. Moreover, in 2015–2017, the uniaxial field-bolted 1643
connection was developed and successfully tested and validated. In 2018, the 1644
biaxial version of the SidePlate connection with HSS and built-up box columns 1645
was developed and tested. It resulted in further performance enhancements: 1646
optimizing the use of connection component materials with advanced analysis 1647
methods and maximizing the efficiency, simplicity and quality control of its 1648
fabrication and erection processes. Following the guidance of the AISC Seismic 1649
Provisions, the validation of the field-welded and field-bolted SidePlate 1650
FRAME configuration consists of: 1651
(a) Analytical testing conducted by SidePlate Systems Inc. using nonlinear 1652
finite element analysis (FEA) for built-up and rolled shapes, plates, bolts, 1653
and welds and validated inelastic material properties by physical testing. 1654
(b) In addition to the tests conducted between 1994 and 2006 utilizing the 1655
original configuration, SidePlate Systems conducted physical validation 1656
testing with full-length beam assembly (SidePlate FRAME configuration) at 1657
(c) (d)
(e)
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the Lehigh University Center for Advanced Technology for Large 1658
Structural Systems (ATLSS) in 2010 (Hodgson et al., 2010a, 2010b, and 1659
2010c; a total of six cyclic tests) and at the University of California, San 1660
Diego (UCSD), Charles Lee Powell Laboratories, in 2012 and 2013 (Minh 1661
Huynh and Uang, 2012; a total of two cyclic tests; and Minh Huynh and 1662
Uang, 2013; a total of one biaxial cyclic test). The biaxial moment 1663
connection test subjected the framing in the orthogonal plane to a constant 1664
shear, creating a moment across the column-beam joint equivalent to that 1665
created by the probable maximum moment at the plastic hinge of the 1666
primary beam, while the framing in the primary plane was simultaneously 1667
subjected to the qualifying cycle loading specified by the AISC Seismic 1668
Provisions (AISC, 2016a). Also, a physical testing program was conducted 1669
at the UCSD (Mashayekh and Uang, 2016; Reynolds and Uang, 2017) to 1670
validate the performance of the field-bolted SidePlate moment connection. 1671
A total of seven cyclic tests—two of which utilized HSS columns and one 1672
of which utilized built-up box column—were conducted. The purpose of 1673
these tests was to confirm adequate global inelastic rotational behavior of 1674
either field-welded or field-bolted SidePlate moment connections with 1675
parametrically selected member sizes, corroborated by analytical testing, 1676
and to identify, confirm and accurately quantify important limit state 1677
thresholds for critical connection components to objectively set critical 1678
design controls. The 2015–2017 testing program at UCSD additionally 1679
aimed to verify the satisfactory performance of HSS columns with a “width 1680
to thickness” ratio of up to 21 in SidePlate moment connections through the 1681
application of a significant axial load on the column in addition to the AISC 1682
Seismic Provisions loading protocol. The testing program also attempted to 1683
verify the satisfactory performance of SidePlate moment connections with 1684
built-up box columns without any internal horizontal shear plates {D} or 1685
stiffener (continuity plates), where flange and web plates of built-up box 1686
columns are continuously connected by either fillet welds or PJP groove 1687
welds along the length of the column. It implies that no CJP welds will be 1688
required within a zone extending from 12 in. (300 mm) above the upper 1689
beam flange to 12 in. (300 mm) below the lower beam flange, flange, and 1690
web plates of boxed wide-flange columns in SidePlate moment connections. 1691
More recently, a full-scale testing program including four biaxial tests and 1692
one uniaxial test with HSS and built-up box columns was successfully 1693
conducted at the University of California, San Diego (Reynolds and Uang, 1694
2018). Two of the biaxial tests utilized the newly developed tuck 1695
configuration (configuration C) with a built-up wide-flange beam with no 1696
vertical shear element. The width-to-thickness ratio of the HSS column was 1697
19.9, confirming the satisfactory performance of HSS columns with a 1698
width-to-thickness ratio of up to 21 once again. 1699
(c) Tests on SidePlate moment connections, both uniaxial and biaxial 1700
applications, show that yielding is generally concentrated within the beam 1701
section just outside the ends of the two side plates {A}. Peak strength of 1702
specimens is usually achieved at an interstory drift angle of approximately 1703
0.03 to 0.05 rad. Specimen strength then gradually reduces due to local and 1704
lateral-torsional buckling of the beam. Ultimate failure typically occurs at 1705
interstory drift angles of approximately 0.04 to 0.06 rad for the field-welded 1706
and 0.06 to 0.08 rad for the field-bolted connection by low-cycle fatigue 1707
fracture from local buckling of the beam flanges and web. 1708
To ensure predictable, reliable, and safe performance of the SidePlate FRAME 1709
configuration when subjected to severe load applications, the inelastic material 1710
properties, finite element modeling (FEM) techniques, and analysis 1711
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methodologies that were used in its analytical testing were initially developed, 1712
corroborated, and honed based on nonlinear analysis of prior full-scale physical 1713
testing of the original SidePlate configuration. The finite element techniques and 1714
design methodologies have been further refined and polished as a result of the 1715
testing program with field-bolted connections at UCSD in 2015–2017. 1716
The earliest physical testing of SidePlate connections consisted of a series of 1717
eight uniaxial cyclic tests, one biaxial cyclic test conducted at UCSD, and a 1718
separate series of large-scale arena blast tests. The blast tests consisted of an 1719
explosion followed by monotonic loading using the following configurations: 1720
two blast tests (one with and one without a concrete slab present), two blast-1721
damaged progressive collapse tests, and one non-blast damaged test—all 1722
conducted by the Defense Threat Reduction Agency (DTRA) of the U.S. 1723
Department of Defense (DoD), at Kirtland Air Force Base, Albuquerque, N.M. 1724
These extensive testing efforts have resulted in the ability of SidePlate Systems 1725
to: 1726
(a) Reliably replicate and predict the global behavior of the SidePlate FRAME 1727
configurations compared to actual tests. 1728
(b) Explore, evaluate, and determine the behavioral characteristics, 1729
redundancies, and critical limit state thresholds of its connection 1730
components. 1731
(c) Establish and calibrate design controls and critical design variables of the 1732
SidePlate FRAME configurations, as validated by physical testing. 1733
Connection prequalification is based on the completion of several carefully 1734
prescribed validation testing programs, the development of a safe and reliable 1735
plastic capacity design methodology that is derived from ample performance 1736
data from 36 full-scale tests, of which six were biaxial, and the judgment of the 1737
CPRP. The connection prequalification objectives have been successfully 1738
completed; the rudiments are summarized below: 1739
(a) System-critical limit states have been identified and captured by physical 1740
full-scale cyclic testing and corroborated through nonlinear FEA. 1741
(b) The effectiveness of identified primary and secondary component 1742
redundancies of the connection system has been demonstrated and validated 1743
through parametric performance testing—both physical and analytical. 1744
(c) Critical behavioral characteristics and performance nuances of the 1745
connection system and its components have been identified, captured, and 1746
validated. 1747
(d) Material submodels of inelastic stress/strain behavior and fracture 1748
thresholds of weld consumables and base metals have been calibrated to 1749
simulate actual behavior. 1750
(e) Sufficient experimental and analytical data on the performance of the 1751
connection system have been collected and assessed to establish the likely 1752
yield mechanisms and failure modes. 1753
(f) Rational nonlinear FEA models for predicting the resistance associated with 1754
each mechanism and failure mode have been employed and validated 1755
through physical testing. 1756
(g) Based on the technical merit of the preceding accomplishments, a rational 1757
ultimate strength design procedure has been developed based on physical 1758
testing, providing confidence that sufficient critical design controls have 1759
been established to preclude the initiation of undesirable mechanisms and 1760
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failure modes and to secure expected safe levels of cyclic rotational 1761
behavior and deformation capacity of the connection system for a given 1762
design condition. 1763
11.2. SYSTEMS 1764
The SidePlate moment connection meets the prequalification requirements for 1765
special and intermediate moment frames in both traditional in-plane frame 1766
applications (one or two beams framing into a column) as well as orthogonal 1767
intersecting moment-resisting frames (corner conditions with two beams 1768
orthogonal to one another, as well as three or four orthogonal beams framing 1769
into the same column). 1770
The SidePlate moment connection has been used in moment-resisting frames 1771
with skewed and/or sloped beams with or without skewed side plates {A}, 1772
although such usage is outside of the scope of this standard. 1773
The unique geometry of the SidePlate moment connection allows its use in other 1774
design applications where in-plane diagonal braces or diagonal dampers are 1775
attached to the side plates {A} at the same beam-to-column joint as the moment-1776
resisting frame, while maintaining the intended SMF or IMF level of 1777
performance. When such dual systems are used, supplemental calculations must 1778
be provided to ensure that the connection elements (plates and welds) have not 1779
only been designed for the intended SMF or IMF connection in accordance with 1780
the prequalification limits set herein, but also for the additional axial, shear, and 1781
moment demands due to the diagonal brace or damper. 1782
11.3. PREQUALIFICATION LIMITS 1783
1. Beam Limitations 1784
A wide range of beam sizes, including both rolled and built-up wide-flange and 1785
HSS beams, has been tested with the SidePlate moment connection, in both 1786
uniaxial and biaxial conditions. For the field-welded connection, the smallest 1787
beam size was a W18×35 (W460×52) and the heaviest a W40×297 1788
(W1000×443). For the field-bolted connection, the smallest beam size was 1789
W21×73 (W530×109) and the largest beam size was W40×397 (W1000×591). 1790
The deepest beam tested was W44×290 (W1100×433) with the depth of 43.6 in. 1791
(1107 mm). Beam compactness ratios have varied from that of a W18×35 1792
(W460×52) with bf/2tf = 7.06 to a W40×294 (W1000×438) with bf/2tf = 3.11. 1793
For HSS beam members, tests have focused on small members such as the HSS 1794
7×4×1/2 (HSS177.8×101.6×12.7) having ratios of b/t = 5.60 and h/t = 12.1. As 1795
a result of these testing programs, critical ultimate strength design parameters 1796
for the design and detailing of the SidePlate moment connection systems have 1797
been developed for general project use. These requirements and design limits are 1798
the result of a detailed assessment of actual performance data coupled with 1799
independent physical validation testing and/or corroborative analytical testing of 1800
full-scale test specimens using nonlinear FEA. It was the judgment of the CPRP 1801
that the maximum beam depth and weight of the SidePlate moment connection 1802
would be limited to the nominal beam depth and approximate weight of the 1803
sections tested, as has been the case for most other connections. 1804
Because the behavior and overall ductility of the SidePlate moment connection 1805
systems is defined by the plastic rotational capacity of the beam, the limit state 1806
for the SidePlate moment connection system is ultimately the failure of the beam 1807
flange, away from the connection. Therefore, the limit of the beam’s hinge-to-1808
hinge span-to-depth ratio of the beam, Lh/d, is based on the demonstrated 1809
rotational capacity of the beam. 1810
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As an example, for test specimen 3 tested at Lehigh University (Hodgson et al., 1811
2010c), the W40×294 (W1000×438) beam connected to the W36×395 1812
(W920×588) column reached two full cycles at 0.06 rad of rotation (measured at 1813
the centerline of the column), which is significantly higher than the performance 1814
threshold of one cycle at 0.04 rad of rotation required for successful 1815
qualification testing by the AISC Seismic Provisions. Most of the rotation at that 1816
amplitude came from the beam rotation at the plastic hinge. At this same 0.06 1817
rad measured at the column centerline, the measured rotation at the beam hinge 1818
was between 0.085 and 0.09 rad [see Figure C-11.2(a)]. The tested half-span 1819
was 14.5 ft (4.42 m), which represents a frame span of 29 ft (8.84 m) and an 1820
Lh/d ratio of 5.5. Assuming that 100% of the frame system’s rotation comes 1821
from the beam’s hinge rotation (a conservative assumption because it ignores 1822
the rotational contributions of the column and connection elements), it is 1823
possible to calculate a minimum span at which the frame drift requirement of 1824
one cycle at 0.04 rad is maintained, while the beam reaches a maximum of 0.085 1825
rad of rotation. Making this calculation gives a minimum span of 20 ft (6.1 m) 1826
and an Lh/d ratio of 3. Making this same calculation for the tests of the 1827
using an average maximum beam rotation of 0.08 rad of rotation, gives a 1829
minimum span of 18 ft, 10 in. (5.74 m) and an Lh/d ratio of 3.2. Given that there 1830
will be variations in the performance of wide-flange beams due to local effects 1831
such as flange buckling, it is reasonable to set the lower bound Lh/d ratio for the 1832
SidePlate field-welded moment connection system at 4.5 for SMF and 3.0 for 1833
IMF, regardless of beam compactness. It should be noted that the minimum Lh 1834
/d ratio of 4.5 (where Lh is measured from the centerline of the beam’s plastic 1835
hinges) typically equates to 6.7 as measured from the face of column to face of 1836
column when the typical side plate {A} extension (shown as “Side plate {A} 1837
extension” in Figure 11.9) from face of column is used. The 6.7 ratio, which is 1838
slightly less than the 7.0 for other SMF moment connections, allows the 1839
potential for a deeper beam to be used in a shorter bay than other SMF moment 1840
connections. The field-bolted testing program at UCSD (Mashayekh and Uang, 1841
2016; Reynolds and Uang, 2017) showed that the field-bolted connections 1842
sustained approximately 2% more story drift, so it is reasonable to set the lower 1843
bound Lh/d ratio for the SidePlate field-bolted moment connection at 4.0 for 1844
SMF and 3 for IMF regardless of beam compactness [see Figure C-11.2(c) for 1845
the measured rotation of the field-bolted W40×211 beam and Figure C-11.2(d) 1846
for the measured rotation of the field-bolted W40×397 beam at the hinge 1847
location]. All moment-connected beams are required to satisfy the width-to-1848
thickness requirements of AISC Seismic Provisions Sections E2 and E3. 1849
Required lateral bracing of the beam follows the AISC Seismic Provisions. 1850
However, due to the significant lateral and torsional restraint provided by the 1851
side plates {A} as observed in all full-scale tests, for calculation purposes, the 1852
unbraced length of the beam is taken as the distance between the respective ends 1853
of each side plate {A} extension (see Figures 11.14 through 11.21 for depictions 1854
of the alphabetical designations). As determined by the full-scale tests, no 1855
additional lateral bracing is required at or near the plastic beam hinge location. 1856
Lateral bracing of columns in accordance with AISC Seismic Provisions Section 1857
E3.4c.1 is not a requirement if the beam is sufficiently braced at the top beam 1858
flange (e.g. with a deck or slab). Sufficient bracing of the beam can be attained 1859
by either continuous bracing of the beam top flange by slab/deck or by meeting 1860
the requirements of AISC Seismic Provisions Section D1.2b. The substantiation 1861
for not using direct bracing is twofold. One is that none of the qualifying tests 1862
had any additional direct column bracing at the level of the top or bottom beam 1863
flanges, and the column tree did not exhibit any sign of torsional twisting, even 1864
for deep columns. This was due to the significant lateral and torsional restraint 1865
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provided by side plates {A} that indirectly braced the column. This is in 1866
accordance with AISC Seismic Provisions Section E3.4c.1, where the indirect 1867
stability bracing is permitted if substantiated. Second, an internal numerical 1868
study was conducted by SidePlate Systems to demonstrate that the side plates 1869
{A} provide adequate indirect stability bracing and that the connection does not 1870
need additional lateral bracing for column stability. 1871
The protected zone is defined as shown in Figures 11.10 and 11.11 and extends 1872
from the end of the side plate {A} to half the beam depth beyond the plastic 1873
hinge location, which is located at one-third the beam depth in the field-welded 1874
connection and one-sixth the beam depth in the field-bolted connection beyond 1875
the end of the side plate {A} due to the cover plate {B} or angle {H} extensions. 1876
This definition is based on test observations that indicate yielding typically does 1877
not extend past 83% and 67% of the depth of the beam from the end of the side 1878
plate {A} in the field-welded and field-bolted connections, respectively. 1879
1880
1881
(a) 1882
1883
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1884
(b) 1885
1886
(c) 1887
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1888
(d) 1889
Fig. C-11.2. SidePlate moment frame tests—backbone curves for (a) W40×294 1890
box sections of 30×30×2 (750×750×50) and 27×27×2-1/2 (680×680×65) , and 1897
hollow structural sections (HSS) including HSS14×14×7/8, HSS18×18×3/4, 1898
and HSS20×20×7/8. Note that when using HSS and built-up box columns, the 1899
side plates {A} transfer the loads to the column in the same way as with wide-1900
flange columns. The only difference is that the horizontal shear component at 1901
the top and bottom of the side plates {A} now transfer that horizontal shear 1902
directly into the faces of the HSS and built-up box column using a shop fillet 1903
weld; thus, an internal horizontal shear plate {D} or stiffener plate is not 1904
required. This was verified with the execution of various tests, including a test 1905
with a W40×397 beam and a 30×30×2 built-up box column, as well as a 1906
W27×102 beam and HSS20×20×7/8 column, both without internal horizontal 1907
shear plates {D} or stiffeners (continuity plates). As such, built-up box columns 1908
are prequalified as long as they meet all applicable requirements of the AISC 1909
Seismic Provisions, with the exceptions mentioned here. There are no internal 1910
stiffener or continuity plates within the column, and there are no requirements 1911
that the columns be filled with concrete for either SMF or IMF applications. 1912
Also no CJP welds will be required within a zone extending from 12 in. (300 1913
mm) above the upper beam flange to 12 in. (300 mm) below the lower beam 1914
flange, flange, and web plates of boxed wide-flange columns in SidePlate 1915
moment connections with built-up box columns. Note: In some blast or other 1916
seismic loading applications, there may be advantages to filling the HSS or 1917
built-box columns with concrete to strengthen the column. 1918
In 2015, SidePlate Systems conducted two tests with HSS columns as part of the 1919
testing program for expanding its prequalification to field-bolted connections 1920
(Mashayekh and Uang, 2016). This configuration is also referred to as the 1921
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SidePlate PLUS Connection. The secondary purpose of these tests was the 1922
inclusion of HSS columns with the width-to-thickness ratio of up to 21-in. 1923
SidePlate moment connections. It was believed that the width-to-thickness ratio 1924
of the walls of HSS columns is a function of local buckling of the walls of the 1925
HSS shape in addition to the connection itself. Therefore, it was decided to 1926
apply a substantial axial load on the columns (40% nominal axial strength of the 1927
column) to test and relax the width-to-thickness limit for SidePlate moment 1928
connections. The columns performed very well, and there was no 1929
yielding/buckling on the face of HSS columns. As a result of two full-scale 1930
physical tests and numerous numerical studies, it was confirmed that the width-1931
to-thickness limit of HSS columns in SidePlate moment connections can be 1932
increased to 21 as long as the axial load in the column stays below 40% of the 1933
nominal axial strength of the column—that is, 0.40AgFy. The HSS column in the 1934
tests complied with ASTM A500 Grade C. The columns performed very well; 1935
there were no issues regarding the performance of the column. However, it was 1936
decided to limit the HSS column to ASTM A1085 per the CPRP’s 1937
recommendation. 1938
The behavior of SidePlate moment connections with cruciform columns is 1939
similar to uniaxial one- and two-sided moment connection configurations 1940
because the ultimate failure mechanism remains in the beam. Successful tests 1941
have been conducted on SidePlate moment connections with cruciform columns 1942
using W36 (W920) shapes with rolled or built-up structural tees. 1943
In 2018, cyclic testing of five full-scale field-bolted SidePlate steel moment 1944
connections was conducted at the University of California, San Diego (Reynolds 1945
and Uang, 2018) to evaluate their performance. Four of the specimens (B1, B2, 1946
B3, and B4) were biaxially loaded, while Specimen B1a was uniaxially loaded. 1947
Each of the biaxially loaded specimens underwent two stages of loading. The 1948
first stage of loading was the monotonic loading of the transverse beams to a 1949
predefined load to develop the probable maximum moment at the column face in 1950
these beams. The second stage of loading consisted of the standard cyclic 1951
loading sequence as specified in the 2016 AISC Seismic Provisions applied to 1952
the primary beam. The uniaxially loaded specimen was only subjected to the 1953
AISC Seismic Provisions cyclic loading protocol. Specimen B2 was the first 1954
specimen tested and consisted of a built-up box column 27×27×2½ 1955
(680×680×65) with W36×282 transverse beams and a W36×210 primary beam. 1956
Specimen B1 was the second specimen tested and consisted of an HSS column 1957
20×20×7/8 with W27×146 transverse beams and a W27×102 primary beam. 1958
The remaining tests reused the same side plates {A}, column, and transverse 1959
beams from Specimen B1. Specimens B3 and B4 used a built-up I section 33-in. 1960
deep with a nominal weight of 105 lb/ft. The newly developed tuck 1961
configuration (configuration C) was used for tests B3 and B4 where the bottom 1962
angles were inverted in comparison with the standard configuration and 1963
connected to the interior face of the beam’s bottom flange. Specimens B1a, B3, 1964
and B4 did not use vertical shear elements. These specimens utilized ASTM 1965
A992, ASTM A572/A572M Grade 50, and ASTM A500 Grade C steel for the 1966
W-shapes, plates, and HSS sections, respectively. ASTM F3148 and ASTM 1967
F2280 high-strength bolts were used in the connections. Specimen B2 1968
ultimately failed by fracture of the beam bottom flange after completing the 5% 1969
drift cycles. Testing of Specimens B1 and B1a was stopped after achieving 7% 1970
and 6% drift, respectively, to preserve the column for future tests. The primary 1971
beams of specimens B1 and B1a were identical except that Specimen B1a did 1972
not utilize vertical shear elements. The performance of the two beams was 1973
comparable and no degradation in the performance was observed due to the 1974
elimination of the vertical shear element. 1975
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For SMF systems, the column bracing requirements of AISC Seismic Provisions 1976
Section E3.4c.1 are satisfied when a lateral brace is located at or near the 1977
intersection of the frame beams and the column. Note: Full-scale tests have 1978
demonstrated that without any additional lateral bracing the full-depth side 1979
plates {A} provide the required indirect lateral bracing of the column flanges 1980
through the side plate {A}-to-column flange welds and the connection elements 1981
that connect the column web to the side plates {A}. Therefore, no additional 1982
direct lateral bracing of the column flanges is required. 1983
3. Connection Limitations 1984
All test specimens have used ASTM A572/A572M Grade 50 plate material. 1985
Nonlinear finite element parametric modeling of side plate {A} extensions in the 1986
range of 0.65d to 1.7d have demonstrated similar overall connection and beam 1987
behavior when compared to the results of full-scale tests. 1988
Because there is a controlled level of plasticity within the design of the two side 1989
plates {A}, the side plate {A} protected zones have been designated based upon 1990
test observations as indicated in Figures 11.10 and 11.11, respectively. It should 1991
be noted that a more conservative design methodology is used for the design of 1992
the side plates {A} of the field-bolted configuration, which results in even less 1993
yielding in the critical section of the side plates {A}. However, it was decided 1994
for consistency to assign similar protected zones for both the field-welded and 1995
the field-bolted connections. 1996
11.4. COLUMN-BEAM RELATIONSHIP LIMITATIONS 1997
See Figures 11.14 through 11.21 for depictions of the alphabetical and 1998
numerical designations. The beams and columns selected must satisfy physical 1999
geometric compatibility requirements between the beam flange and column 2000
flange to allow sufficient lateral space for depositing fillet welds {5} along the 2001
longitudinal edges of the beam flanges that connect to the top and bottom cover 2002
plates {B}. Equations 11.4-1a/11.4-1aM and 11.4-1b/11.4-1bM assist designers 2003
in selecting appropriate final beam and column size combinations prior to the 2004
SidePlate moment connection actually being designed for a specific project. 2005
Note: One of the field-bolted connection tests utilized a PJP weld for weld {5}, 2006
which allows for a tighter tolerance in the geometric compatibility checks. The 2007
test performed similar to others with fillet welds for weld {5}; thus weld {5} 2008
may be deposited as a PJP weld or fillet weld as needed. 2009
Unlike more conventional moment frame designs that typically rely on the 2010
deformation of the column panel zone to achieve the required rotational 2011
capacity, SidePlate moment connection technology instead stiffens and 2012
strengthens the column panel zone by providing a minimum of three panel zones 2013
(the column web plus the two full-depth side plates {A}). This configuration 2014
forces the vast majority of plastic deformation to occur through flange local 2015
buckling of the beam. 2016
The column web must be capable of resisting the panel zone shear loads 2017
transferred from the horizontal shear plates {D} through the pair of shop fillet 2018
welds {3}. The strength of the column web is thereby calculated and compared 2019
to the ultimate strength of the welds {3} on both sides of the web. To be 2020
acceptable, the panel zone shear strength of the column must be greater than the 2021
strength of the two welds. This ensures that the limit state will be failure of the 2022
welds as opposed to failure of the column web. The two side plates {A} may be 2023
used as doubler plates to check the overall panel zone strength. The following 2024
calculation and check is built into the SidePlate moment connection design 2025
software: 2026
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1.0u
n
R
R (C-11.4-1) 2027
where 2028
Ru = ultimate strength of fillet welds {3} from horizontal shear plates {D} to 2029
column web, kips (N) 2030
Rn = nominal strength of column web panel zone in accordance with AISC 2031
Specification Section J10.6b, kips (N) 2032
230.60 1
fc fcn y c cw
sp c cw
b tR F d t
d d t (from Spec. Eq. J10-11) 2033
where 2034
bfc = width of column flange, in. (mm) 2035
dc = depth of column, in. (mm) 2036
dsp = depth of side plate {A}, in. (mm) 2037
tcw = thickness of column web, in. (mm) 2038
tfc = thickness of column flange, in. (mm) 2039
In determining the SMF column-beam moment ratio to satisfy strong 2040
column/weak beam design criteria, the beam-imposed moment, M*pb, is 2041
calculated at the column centerline using statics (i.e., accounting for the increase 2042
in moment due to shear amplification from the location of the plastic hinge to 2043
the center of the column as a result of the development of the probable 2044
maximum moment of the beam, Mpr, at the plastic hinge location), and then 2045
linearly decreased to one-quarter the column depth above and below the extreme 2046
top and bottom fibers of the side plates {A}. This location is used for 2047
determination of the column strength because the column is unlikely to form a 2048
hinge within the panel zone due to the presence and strengthening effects of the 2049
two side plates {A}. 2050
In calculating the biaxial column-beam moment ratio, it is permitted to take the 2051
actual yield strength of the column material as the specified yield strength in lieu 2052
of the specified minimum yield stress, Fy, and to consider the full composite 2053
behavior of the column for axial and flexural loading action (story drift analysis) 2054
if it is filled with concrete. The column strength formula, Equation 11.4-6, 2055
assumes equal column properties about both axes. For column sections with 2056
unequal properties about both axes, interaction equations based on rational 2057
analysis should be used. Guidance for checking columns subject to biaxial 2058
bending and axial force is provided in AISC Seismic Provisions Section E3 2059
Commentary. 2060
This requirement need not apply if any of the exceptions articulated in AISC 2061
Seismic Provisions Section E3.4a are satisfied. The calculation and check are 2062
included in the SidePlate connection design software. 2063
11.5. CONNECTION WELDING LIMITATIONS 2064
Fillet welds joining the connection plates to the beam and column provided on 2065
all of the SidePlate test specimens have been made by either of the self-shielded 2066
flux cored arc welding processes (FCAW-S or FCAW-G), with a few specimens 2067
using the submerged arc welding process (SAW) for certain shop fillet welds. 2068
Other than the original three prototype tests in 1994 and 1995 that used a non-2069
toughness as required by the 2010 AISC Seismic Provisions. Also, it should be 2071
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noted that typically the test specimens were fitted and tacked together using an 2072
E7018 stick electrode and then welded with an FCAW process (implying that 2073
the intermixing of FCAW and E7018 has been tested and is not of concern). 2074
Test specimens that included either a field complete-joint-penetration groove-2075
welded beam-to-beam splice or field fillet welds specifically utilized E70T-6 for 2076
the horizontal position and E71T-8 for the vertical position. 2077
11.6. CONNECTION DETAILING 2078
Figures 11.14 through 11.16 show typical one- and two-sided moment 2079
connection details used for shop fabrication of the column with fillet welds. 2080
Tests have shown that the horizontal shear plate {D} need not be welded to the 2081
column flanges for successful performance of the connection. However, if there 2082
are orthogonal forces being transferred through the connection from collector, 2083
chord, or cantilever beams, then fillet welds connecting the horizontal shear 2084
plates {D} and the column flanges may be required. 2085
In the field-welded connection, tests have shown that the use of oversized bolt 2086
holes in the side plates {A}, located near their free end (see Figure C-11.3), do 2087
not affect the performance of the connection because beam moments and shears 2088
are transferred through fillet welds. Bolts from the side plate {A} to the vertical 2089
shear element are only required for erection of the full-length beam assembly 2090
prior to field welding of the connection and may be removed, at the contractor’s 2091
discretion after the field fillet welds have been applied (also implying that if all 2092
the erection bolts cannot be placed, it is acceptable as it relates to the 2093
connections performance). 2094
Figure 11.17 and 11.18 show the typical full-length beam detail used for shop 2095
fabrication of the beam with fillet welds. Multiple options can be used to create 2096
the vertical shear element (if needed), such as a combination of angles and plates 2097
or simply bent plates. 2098
Figure 11.19(a) and 11.19(b) show the typical full-length beam-to-side plate 2099
{A} detail used for field erection of the beam with fillet welds and bolts, 2100
respectively. In the field-bolted connection, either longitudinal angles {G} 2101
(rolled or built-up) or horizontal plates {T} that are welded to the side plates 2102
{A} may be used to transfer the load from the beam to the side plates {A}, as 2103
shown in Figure 11.19(b). 2104
Figures 11.20 and 11.21 show shop weld {9} connecting side plate {A} to 2105
column face as well as shop weld {10} that connects the intersecting orthogonal 2106
side plates to construct the side plate interlock assembly in biaxial connections. 2107
11.7. DESIGN PROCEDURE 2108
The design procedure for the SidePlate moment connection system is based on 2109
results from both physical testing and detailed nonlinear finite element 2110
modeling. The procedure uses an ultimate strength design approach to size the 2111
plates and welds in the connection, incorporating strength, plasticity, and 2112
fracture limits. For welds, an ultimate strength analysis incorporating the 2113
instantaneous center of rotation is used (as described in AISC Steel Construction 2114
Manual Part 8). For bolts, an ultimate strength analysis incorporating eccentric 2115
bolt group design methodology and instantaneous center of rotation is used (as 2116
described in AISC Specification Section J2.4b). Overall, the design process is 2117
consistent with the expected seismic behavior of an SMF system: Lateral drifts 2118
due to seismic loads induce moments and shear forces in the columns and 2119
beams. Where these moments exceed the yield strength of the beam, a plastic 2120
hinge will form. While the primary yield mechanism is plastic bending in the 2121
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beam, in the field-welded connection, a balanced design approach allows for 2122
secondary plastic bending to occur within the side plates {A} (hence the 2123
reasoning for the protected zones on the side plates {A} for this option). In the 2124
field-bolted connection, more conservative side plate {A} design methodology 2125
has been developed so that secondary plastic hinging within the side plates {A} 2126
does not occur (hence the protected zones on the side plates {A} in this option 2127
are not required). Ultimately, the location of the hinge in the beam directly 2128
affects the amplification of load (i.e., moment and shear from both seismic and 2129
gravity loads) that is resisted by the components of the connection, the column 2130
panel zone, and the column, as shown in Figure C-11.3. Each connection 2131
component can then be designed to resist its respective load demands induced by 2132
the seismic drift (including any increases due to shear amplification as measured 2133
from the beams plastic hinge location). 2134
For the SidePlate moment connection, all of the connection details—including 2135
the sizing of connection plates, angles, fillet welds, and bolts—are designed and 2136
provided by engineers at SidePlate Systems. The design of these details is based 2137
on basic engineering principles, plastic capacities validated by full-scale testing, 2138
and nonlinear finite element analysis. A description of the design methods is 2139
presented in Step 7. The initial design procedure for the engineer of record in 2140
designing a project with SidePlate moment connections largely involves: 2141
Sizing the frame’s beams and columns, shown in Steps 1 and 2. 2142
Checking applicable building code requirements and performing a 2143
preliminary compliance check with all prequalification limitations, shown 2144
in Steps 3 and 4. 2145
Verifying that the SidePlate moment connections have been designed with 2146
the correct project data as outlined in Step 5 and are compliant with all 2147
prequalification limits, including final column-beam relationship limitations 2148
as shown in Steps 6, 7, and 8. 2149
Step 1. Equations 11.4-1a/11.4-1aM and 11.4-1b/11.4-1bM should be used as a 2150
guide in selecting beam and column section combinations during design 2151
iterations. 2152
2153
Fig. C-11.3. Amplification of maximum probable plastic hinge moment, Mpr, 2154 to the column face. 2155
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Satisfying these equations minimizes the possibility of incompatible beam and 2156
column combinations that cannot be fabricated and erected or that may not 2157
ultimately satisfy column-beam moment ratio requirements. 2158
Step 2. The SidePlate moment connection design forces a plastic hinge to form 2159
in the beam beyond the extension of the side plates {A} from the face of the 2160
column (side plate {A} extension in Figure 11.9). Because inelastic behavior is 2161
forced into the beam at the hinge, the effective span of the beam is reduced, thus 2162
increasing the lateral stiffness and strength of the frame (see Figure C-11.4). 2163
This increase in stiffness and strength provided by the two parallel side plates 2164
{A} must be simulated when creating elastic models of the steel frame. Many 2165
commercial structural analysis software programs have a built-in feature for 2166
modeling the stiffness and strength of the SidePlate moment connection. 2167
Step 5. Some structural engineers design moment-frame buildings with a lateral-2168
only computer analysis. The results are then superimposed with results from 2169
additional lateral and vertical load analysis to check beam and column stresses. 2170
Because these additional lateral and vertical loads can affect the design of the 2171
SidePlate moment connection, they must also be submitted with the lateral-only 2172
model forces. Such additional lateral and vertical loads include drag and chord 2173
forces, factored shear loads at the plastic hinge location due to gravity loads on 2174
the moment frame beam itself, loads from gravity beams framing into the face of 2175
the side plates {A}, and gravity loads from cantilever beams (including vertical 2176
loads due to earthquakes) framing into the face of the side plates {A}. 2177
There are instances where an in-plane lateral drag or chord axial force needs to 2178
transfer through the SidePlate moment connection, as well as instances where it 2179
is necessary to transfer lateral drag or chord axial forces from the orthogonal 2180
direction through the SidePlate moment connection. In such instances, these 2181
loads must be submitted in order to properly design the SidePlate moment 2182
connection for these conditions. 2183
Step 6 of the procedure requires SidePlate Systems to review the information 2184
received from the structural engineer, including the assumptions used in the 2185
generation of final beam and column sizes to ensure compliance with all 2186
applicable building code requirements and prequalification limitations contained 2187
herein. Upon reaching concurrence with the structural engineer of record that 2188
beam and column sizes are acceptable and final, SidePlate Systems creates a 2189
load matrix of the entire structure with these member sizes, including all 2190
submitted applicable loads and forces, and designs and details all of the 2191
SidePlate moment connections for a specific project in accordance with Step 7. 2192
Any changes in member sizes, loads, or forces need to be coordinated with 2193
SidePlate Systems because such changes will typically require this step to be 2194
repeated. 2195
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2196
Fig. C-11.4. Increased frame stiffness with reduction in effective span of the beam. 2197
The SidePlate moment connection design procedure is based on the idealized 2198
primary behavior of an SMF system—the formation of a plastic hinge in the 2199
beam outside of the connection. In the field-welded connection, although the 2200
primary yield mechanism is the development of a plastic hinge in the beam near 2201
the end of the side plate {A}, secondary plastic behavior (plastic moment 2202
capacity) is developed within the side plates {A} themselves, at the face of the 2203
column (this is not the case for the field-bolted connections). Overall, a balanced 2204
design is used for the connection components to ensure that the plastic hinge 2205
will form at the predetermined location. The demands on the connection 2206
components are a function of the strain-hardened flexural strength of the beam, 2207
the gravity loads carried by the beam, and the relative locations of each 2208
component and the beam’s plastic hinge. Connection components closer to the 2209
column centerline are subjected to increased moment amplification compared to 2210
components located closer to the beam’s plastic hinge as illustrated in Figure C-2211
11.3. 2212
Step 7 of the process requires that SidePlate Systems design and detail the 2213
connection components for the actions and loads determined in Step 6. The 2214
procedure uses an ultimate strength design approach to size plates, bolts, and 2215
welds, thus incorporating strength, plasticity, and fracture limits. For welds, an 2216
ultimate strength analysis incorporating the instantaneous center of rotation is 2217
used (as described in AISC Steel Construction Manual Part 8). For bolts, an 2218
ultimate strength analysis incorporating eccentric bolt group design 2219
methodology and instantaneous center of rotation is used (as described in AISC 2220
Specification Section J2.4b). Overall, the design process is consistent with the 2221
expected seismic behavior of an SMF system as described previously. 2222
The SidePlate moment connection components are divided into four distinct 2223
design groups: 2224
(a) Load transfer out of the beam 2225
(b) Load transfer into the side plates {A} 2226
(c) Design of the side plates {A} at the column face 2227
(d) Load transfer into the column 2228
The transfer of load out of the beam is achieved through welds {4} and {5}. The 2229
loads are in turn transferred through the vertical shear elements {E} and cover 2230
plates {B} into the side plates {A} by either welds {6} and {7} (field-welded) or 2231
bolt group (field-bolted). The load at the column face (gap region) is resisted 2232
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solely by the side plates {A}, which transfers the load directly into the column 2233
through weld {2} and weld {1} in a box or HSS section. In a wide-flange 2234
column, the load is transferred through weld {2} and indirectly through weld 2235
{3} through the combination of weld {1} and the horizontal shear plates {D}. At 2236
each of the four design locations, the elements are designed for the combination 2237
of moment, Mgroup, and shear, Vu. 2238
Connection Design 2239
Side Plate {A}, Field-Welded. To achieve the balanced design for the 2240
connection—the primary yield mechanism developing in the beam outside of the 2241
connection with secondary plastic behavior within the side plates {A}—the 2242
required minimum thickness of the side plate {A} is calculated using an 2243
effective side plate {A} plastic section modulus, Zeff, generated from actual side 2244
plate {A} behavior obtained from stress and strain profiles along the depth of 2245
the side plate {A}, as recorded in test data and nonlinear analysis (see Figure C-2246
11.5). The flexural strength of the plates, Mn,sp, is then calculated using the 2247
simplified Zeff and an effective plastic stress, Fye, of the plate. Allowing for 2248
yielding of the plate as observed in testing and analyses (see Figure C-11.6) and 2249
comparing to the design demand, Mgroup, calculated at the face of column gives: 2250
,
1.0group
n sp
M
M (C-11.7-1) 2251
where 2252
,n sp ye effM F Z 2253
Side Plate {A}, Field-Bolted. The required minimum thickness of the side plate 2254
{A} is calculated based on the engineering principals of fully yielded section at 2255
either column face or at the location of the first bolt as shown in Figures C-2256
11.7(a) and C-11.7(b). The section of the side plate {A} at the column face has 2257
larger design demand in comparison with that of the net section at the location 2258
of the first bolt so the required minimum thickness will be the greater of the two 2259
design checks. 2260
To ensure the proper behavior of the side plate {A} and to preclude undesirable 2261
limit states, such as buckling or rupture of the side plate {A}, the ratio of the gap 2262
distance between the end of the beam and the face of the column to the side 2263
plate {A} thickness is kept within a range for all connection designs. The 2264
optimum gap-to-thickness ratio has been derived based upon the results of full-2265
scale testing and parametric nonlinear analysis. 2266
2267
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2268
Fig. C-11.5. Stress profile along depth of side plate {A} at the column face at maximum load cycle. 2269
2270
2271
Fig. C-11.6. Idealized plastic stress distribution for computation of the effective plastic modulus, 2272 Zeff, of the side plate. 2273
2274
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2275
(a) 2276
2277
(b) 2278
Fig. C-11.7. (a) Side plate {A} elevation view and stress diagram at the net section; (b) 2279 side plate {A} elevation view and stress diagram at the column face for configuration A 2280
(standard). 2281
2282
Cover Plate {B}. The thickness of the cover plates {B} is determined by 2283
calculating the resultant shear force demand, Ru, from the beam moment couple 2284
as: 2285
u groupR M d (C-11.7-2) 2286
and by calculating the vertical shear loads, resisted through the critical shear 2287
plane of the cover plates {B}. 2288
The critical shear plane for the field-welded connection is defined as a section 2289
cut through the cover plate {B} adjacent to the boundary of weld {7}, as shown 2290
in Figure C-11.8(a). Hence, the thickness, tcp, of the cover plate {B} is: 2291
2 0.6
ucp
ye crit
Rt
F L (C-11.7-3) 2292
where 2293
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Lcrit = length of critical shear plane through cover plate {B} as shown in 2294
Figure C-11.8(a), in. (mm) 2295
The top cover plate {B} in the field-bolted connection (standard configuration) 2296
is designed based on the block shear check in the critical shear plane which is 2297
defined as a section cut through the cover plate {B} through the bolt holes, as 2298
(2) dpl = depth of vertical shear element, in. (mm) 2320
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Horizontal Shear Plate (HSP) {D}. The thickness of the HSP {D}, if 2321
applicable, (see Figures 11.14–11.19) is determined as the thickness required to 2322
transfer the horizontal shear demand from the top (or bottom) of the side plates 2323
{A} into the column web. The shear demand on the HSP is calculated as the 2324
design load developed through the fillet weld connecting the top (or bottom) 2325
edge of the side plates {A} to the HSP (weld {1}). The demand force is 2326
determined using an ultimate strength analysis of the weld group at the column 2327
(weld {1} and weld {2}) as described in the following section. 2328
0.6
uhsp
y pl
Vt
F l (C-11.7-5) 2329
where 2330
uV = calculated horizontal shear demand delivered by weld {1} to the HSP, 2331
kips (N) 2332
lpl = effective length of horizontal shear plate {D}, in. (mm) 2333
Welds. Welds are categorized into three weld groups and sized using an 2334
ultimate strength analysis. 2335
The weld groups are categorized as follows (see Figures 11.14-11.21 and Figure 2336
C-11.9): 2337
Weld Group 1—Fillet welds from the beam flange to the cover plate {B}/angles 2338
{H} (weld {5} and weld {5a}) and the fillet welds from the beam web to the 2339
VSE (weld {4}). 2340
Weld Group 2—Fillet welds from the cover plate {B} to the side plate {A} 2341
(weld {7}) and fillet welds from the VSE to the side plate {A} (weld {6}) (only 2342
for field-welded connections). 2343
Weld Group 3—Fillet welds from the side plate {A} to the HSP {D} (weld 2344
{1}), fillet welds from the side plate {A} to the column flange tips (weld {2}), 2345
and fillet welds from the HSP {D} to the column web (weld {3}). 2346
2347
Fig. C-11.9. Location of design weld groups and associated moment demand, MG#. 2348
The ultimate strength design approach for the welds incorporates an 2349
instantaneous center of rotation method as shown in Figure C-11.10 and 2350
described in AISC Steel Construction Manual Part 8. 2351
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At each calculation iteration, the nominal shear strength, Rn, of each weld group 2352
for a determined eccentricity, e, is compared to the demand from the amplified 2353
moment to the instantaneous center of the group, Vpre. The process is continued 2354
until equilibrium is achieved. Because the process is iterative, SidePlate Systems 2355
engineers use design calculation software to compute the weld sizes required to 2356
achieve the flexural and shear strength needed for each weld group to resist the 2357
amplified flexural and vertical shear demand, Mgroup and Vu, respectively. 2358
Bolts (Field-Bolted Connection Only). The ultimate strength analysis 2359
incorporating eccentric bolt group design methodology and instantaneous center 2360
of rotation as shown in Figure C-11.11 and described in AISC Specification 2361
Section J2.4b is used to design the number of required bolts. An iterative 2362
process is required to find the solution. At each calculation iteration, the nominal 2363
shear strength, Rn, of the bolt group (comprising horizontal and vertical rows of 2364
bolts), for a determined eccentricity, e, is compared to the demand from the 2365
amplified moment and shear to the instantaneous center of the group, Vpre. The 2366
process is continued until equilibrium is achieved. 2367
Step 8 requires that the engineer of record review calculations and drawings 2368
supplied by SidePlate Systems engineers to ensure that all project-specific 2369
moment connection designs have been appropriately completed and that all 2370
applicable project-specific design loads, building code requirements, building 2371
geometry, and beam-to-column combinations have been satisfactorily addressed. 2372
The Connection Prequalification Review Panel (CPRP) has prequalified the 2373
SidePlate moment connection after reviewing the proprietary connection design 2374
procedure contained in the SidePlate moment connection design software 2375
(version 16 for welded and version 17 for bolted), as summarized here. In the 2376
event that SidePlate moment connection designs use a later software version to 2377
accommodate minor format changes in the software’s user input summary and 2378
output summary, the SidePlate moment connection designs will be accompanied 2379
by a SidePlate moment connection validation report that demonstrates that the 2380
design dimensions, lengths, and sizes of all plates and welds generated using the 2381
CPRP-reviewed connection design procedure remain unchanged from that 2382
obtained using the later version connection design software. Representative 2383
beam sizes to be included in the validation report are W36×150 (W920×223) 2384
and W40×294 (W1000×438) for the field-welded and W36×150, W40×211 and 2385
W40×397 for the field-bolted connection. 2386
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2387
Fig. C-11.10. Instantaneous center of rotation of a sample weld group. 2388
2389
2390
Fig. C-11.11. Instantaneous center of rotation of a sample bolt group. 2391
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CHAPTER 12 2392
SIMPSON STRONG-TIE STRONG FRAME 2393
MOMENT CONNECTION 2394
12.1. GENERAL 2395
The Simpson Strong-Tie® Strong Frame® moment connection uses patented 2396
Yield-Link® structural fuse technology to create a field-bolted, partially 2397
restrained (PR) moment connection for strong-axis wide-flange beam-to-2398
column connections. The Yield-Links are either configured as separate T-2399
stub elements connected to each beam flange, or they are connected to a 2400
common end plate for shallow beam connections. During seismic events, 2401
inelastic demand is absorbed in the Yield-Link elements of the beam-to-2402
column connection instead of requiring the formation of a plastic hinge in the 2403
beam adjacent to the column. The connection eliminates field welding, and 2404
the frame behavior afforded by the connection enables frames to be designed 2405
without the need for flange bracing on the beams. This is particularly useful 2406
in structures where providing flange bracing can be difficult (such as when 2407
integrated into wood structures) or is an undesirable architectural intrusion. 2408
Connection testing qualified the use of snug-tight bolts for typical field-2409
installed bolts, simplifying bolt installation, inspection, and frame erection. 2410
The connection centers around the Yield-Link (Link) structural fuse 2411
performance and a capacity-based design procedure that, under lateral 2412
loading, pushes inelastic demand into the Links rather than the members. 2413
Unlike other prequalified special moment frame (SMF) connections, little if 2414
any inelastic behavior is expected in the members. Whether configured as a 2415
modified T-stub or connected to a common end plate, the Link serves to 2416
transfer moment from the beam to the column. The connection bolts to the 2417
column flange with four snug-tight ASTM F3125 Grade A325 orA325M 2418
bolts at each link (pretensioned ASTM F3125 Grade A325, A325M or F1852 2419
bolt assemblies are also permitted). The stem of the Link bolts to the beam 2420
F1852, or F2280 bolt assemblies. In between the connection to the beam and 2422
column, the stem of the Link is elongated and contains a section with reduced 2423
area that defines the location of yielding in the Link. This reduced area 2424
controls the axial strength of the Link and provides for very reliable estimates 2425
of the yield and ultimate moment strength of the beam-to-column connection. 2426
To prevent buckling of the yielding section of the Link when in compression, 2427
a buckling restraint plate (BRP) is placed over the Link and bolted to the 2428
beam flange on either side of the reduced-area section of the Link. The BRP 2429
uses snug tight ASTM F3125 Grade A325 or A325M bolts that pass through 2430
a spacer plate that fills the gap between the bottom of the BRP and the near 2431
surface of the beam flange. The web of the beam connects to either the 2432
column or the common end plate via a single-plate shear connection. The 2433
connection uses an arrangement of bolts that permit transfer of shear and 2434
axial forces between the beam and column, while at the same time limiting 2435
the transfer of moment. This is accomplished by having a central pivot point 2436
defined by a central bolt passing through standard holes in both the beam 2437
web and the shear plate and by having the remaining bolts in the shear plate 2438
pass through either horizontal or vertical slots in the shear plate and standard 2439
holes in the beam web. This arrangement creates a hinge in the beam web-to-2440
column flange connection and defines the effective rotation point for the 2441
plastic hinge. Shear-plate bolts are permitted to be snug-tight ASTM F3125 2442
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Grade A325 or A325M or pretensioned ASTM F3125 Grade A325, A325M, 2443
or F1852. The hinge is used to transfer net axial force from the beam to the 2444
column, so in addition to shear- and moment-related design provisions found 2445
in other prequalified moment connections, this connection also contains 2446
design provisions for axial load transfer. 2447
Initial qualification testing consisted of a series of nine reversed cyclic tests 2448
according to the 2010 AISC Seismic Provisions, Section E3.6c (AISC, 2449
2010a) covering three configurations, each with three replications. Each test 2450
consisted of a single-story, single-bay frame with lateral loads (in-plane 2451
shear) introduced into the top flange of the beam through a wood nailer 2452
connected to the beam flange. Only one end of the beam used the Strong 2453
Frame connection, and the remaining beam-to-column and column-to-test 2454
bed connections were pinned. This configuration was chosen for testing the 2455
connection over the typical cantilever beam configuration for two primary 2456
reasons: It allowed beam axial loads to be driven through the joint to enable 2457
verification of both the axial and moment related design provisions, and it 2458
permitted observation of the beam flange response when flange bracing was 2459
omitted. The testing resulted in all frames reaching a drift level of 0.05 rad 2460
without a loss of strength greater than 20% of the nominal plastic moment 2461
strength, Mp, satisfying the requirements of the AISC Seismic Provisions, 2462
Section E3.6b. For this connection Mp is calculated using the yielding area of 2463
the links and the connection geometry rather than the beam properties. 2464
At the current time there are no other PR connections that have been 2465
prequalified as an SMF connection, and PR SMF connections were not 2466
directly addressed in the 2010 AISC Seismic Provisions. The 2016 AISC 2467
Seismic Provisions (AISC, 2016a) now address the potential use of PR SMF 2468
connections in Section E3.6b.(b). Accordingly, even though the initial testing 2469
met the SMF connection performance requirements of the 2010 AISC 2470
Seismic Provisions, additional requirements were created to demonstrate the 2471
suitability of the connection and the design procedure for use as SMF or IMF 2472
connections in high-seismic applications. 2473
The first additional requirement was to assess the connection performance 2474
through a component equivalency evaluation using the procedures found in 2475
FEMA P-795, Quantification of Building Seismic Performance Factors: 2476
Component Equivalency Methodology (FEMA, 2011). An independent study 2477
was commissioned to perform the FEMA P-795 evaluation, comparing the 2478
Strong Frame connection to the reduced beam section (RBS) connection, 2479
resulting in two changes to the design procedure. The Link flange-to-stem 2480
weld was required to develop the full strength of the unreduced portion of the 2481
stem at the column side (it had been previously designed for the probable 2482
maximum tensile strength of the reduced yielding area); and a single 2483
thickness of stem material, 1/2 in. (13 mm), was selected (initially different 2484
thicknesses were considered). Six additional tests similar to those described 2485
previously (three reversed cyclic tests according to the 2010 AISC Seismic 2486
Provisions and three monotonic tests) were then conducted to verify the 2487
performance with the amended design and detailing procedure. 2488
Although not required by the 2010 AISC Seismic Provisions, the monotonic 2489
tests were conducted to satisfy FEMA P-795 requirements. The purpose of 2490
the monotonic testing is to better understand the collapse behavior of 2491
buildings using the connection by investigating the interstory drift capacity 2492
afforded by the connection. The results of the cyclic tests again showed that 2493
the connection meets the performance requirements of the 2010 AISC 2494
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Seismic Provisions and that the ultimate limit state was as predicted: a net 2495
section fracture in the reduced portion of the Links. The results of the 2496
monotonic tests showed that the connection has tremendous displacement 2497
capacity, the tests being stopped at 9.5% interstory drift without failure or 2498
decreasing from peak capacity. The conclusion from the FEMA P-795 study 2499
was that the Strong Frame connection is equivalent to the prequalified RBS 2500
connection. It should be noted that for all the testsinitial and secondary, 2501
cyclic and monotonicyielding initiated from about 0.01 to 0.015 rad 2502
interstory drift angle as is typically expected of frames with SMF 2503
connections. 2504
Even with the successful FEMA P-795 evaluation, a second additional 2505
requirement was added to look more at system behavior rather than the 2506
individual connection behavior as was the focus of the FEMA P-795 2507
evaluation. To address this additional requirement, a series of nonlinear 2508
response history analyses were performed using a suite of ground motions 2509
and a suite of archetype buildings to compare the seismic response of 2510
buildings using the Strong Frame connection to buildings using a prequalified 2511
connection. The connection chosen for comparison was again the RBS 2512
connection. As before, an independent study was commissioned, with designs 2513
for both systems minimized to the extent allowed by the respective design 2514
procedures. The study included the development of archetype designs for 2515
representative steel moment frames for a two-story, four-story, and six-story 2516
building using ASCE/SEI 7-10 (ASCE, 2010), the 2010 AISC Specification 2517
(AISC, 2010b) and the 2010 AISC Seismic Provisions and was evaluated 2518
using seven scaled ground motion pairs. The study demonstrated that the 2519
performances of the Strong Frame and comparable RBS structures were very 2520
similar and within acceptable levels. No collapses were predicted by the 2521
analysis. The most severe response was recorded for the two-story RBS 2522
archetype, which exhibited a maximum story drift ratio for one record of 2523
nearly 5%. Mean story drift response for both the Strong Frame and RBS 2524
structures averaged approximately 2.3%, and the mean plus one standard 2525
deviation response averaged 3% for the Strong Frame structures and 2.8% for 2526
the RBS structures. 2527
In addition to the cyclic and monotonic testing specifically used to qualify the 2528
Strong Frame connection, other large-scale shake table test programs have 2529
employed the connection. Steel frames using the Strong Frame connection 2530
were part of the 2009 NEESWood Capstone tests at Japan’s E-Defense 2531
facility in Miki, Japan (van de Lindt et al., 2009). The full-scale seven-story 2532
structure consisted of first-story steel framing using the Strong Frame 2533
connection, which supported a six-story wood light-frame structure on top 2534
and had a plan dimension of 40 ft by 60 ft (12 m by 18 m). More recently, 2535
steel frames using the Strong Frame connection were employed as retrofit 2536
elements in the first story of a four-story full-scale light frame wood building 2537
built to simulate a typical San Francisco-style wood structure with a 2538
soft/weak first story due to ground-level parking. Known as the NEESSoft 2539
project (Bahmani et al., 2016; Pryor et al., 2014; van de Lindt et al., 2016), 2540
the building was successfully tested at the NHERI @ UC San Diego 2541
(formerly NEES @ UCSD) outdoor shake table under a variety of different 2542
ground motions. 2543
In 2015 six additional cyclic tests (three each of two configurations) were 2544
conducted on small frames employing shallow beams and the end-plate 2545
Yield-Link connection, where the single plate shear connection and the 2546
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yielding stem of the Yield-Link are all welded to a common end plate, which 2547
is then bolted to the column flange. As before single story, single bay frames 2548
were tested. Column bases were hinged, and both beam-to-column 2549
connections were moment resisting. The smaller of the two frame specimens 2550
consisted of 6-in. deep welded H-section columns and an 8.5-in. deep welded 2551
H-section beam in a frame approximately 8-ft tall by 9.5-ft wide (to member 2552
centerlines). The larger of the frame specimens similarly consisted of 18-in. 2553
deep welded columns and an 8.5-in. deep welded beam in a frame 2554
approximately 8-ft tall by 12-ft wide. As before, in-plane lateral load was 2555
delivered through a wood nailer connected to the top flange of the beam, and 2556
the bottom flange remained unbraced. Bolts connecting the yielding stem of 2557
the Link to the beam were pretensioned, whereas the remaining bolts at the 2558
beam web-to-shear plate, the end plate-to-column flange, and the BRP bolts 2559
were all installed snug-tight. There were no observed failures in the smaller 2560
frame, and testing was stopped after two cycles of 0.08 rad interstory drift 2561
angle. For the larger frame, failure occurred in the Links, with fracture of the 2562
yielding area of the link occurring in the first cycle of 0.08 rad interstory drift 2563
angle for one test and in the second cycle of 0.08 rad for the other two tests. 2564
All tests met the connection performance requirements in the 2016 AISC 2565
Seismic Provisions Section E3.6b. For the smaller frames, yielding initiated 2566
at approximately 0.0125 rad interstory drift angle, whereas it was 2567
approximately 0.01 rad for the larger frame. 2568
In 2017 three additional cyclic tests and one monotonic test were conducted 2569
to support an expansion of both Yield-Link and member sizes. As before, 2570
single story, single bay frames were tested with one beam-to-column 2571
connection designed as moment resisting using T-stub Yield-Links, with the 2572
other beam-to-column connection and both column base connections 2573
designed as pins. In-plane lateral load was again delivered to the frame via a 2574
wood nailer connected to the top flange of the beam, and also as before the 2575
bottom flange was unbraced. Columns were braced out of plane at the cap 2576
plate (slightly above the level of the top flange of the beam) and the column 2577
base. Column sections were ( ), and the beam was2578
( ). The center-to-center distance between the two 2579
columns was 35 ft, and the beam centerline was 21.5 ft above the column 2580
base hinges. T-stub Yield-Links were designed for the new maximum size 2581
consisting of 1-in. thick stem material, with a 6-in. wide yield width in the 2582
reduced section, which for comparison corresponds to the remaining flange 2583
area of a 50% RBS cut on a . As expected, fracture of the yielding 2584
section of the Link was the failure mode in all three cyclic tests. Two of the 2585
test specimens completed one cycle of 0.05 rad interstory drift prior to 2586
failure, and one completed two cycles of 0.05 rad interstory drift angle before 2587
failure. No failures occurred in the monotonic test, and it was stopped at an 2588
approximately 0.09 rad interstory drift angle due to actuator limitations. For 2589
both cyclic and monotonic tests, initiation of yielding occurred at an 2590
approximately 0.01 rad interstory drift angle. The overall tested assembly is 2591
shown in Figure C-12.1, and a plot of moment at the face of the column 2592
versus story drift is shown in Figure C-12.2. 2593
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2594 Fig. C-12.1. Testing new largest Link size with 6 in.2 yield area. 2595
2596 Fig. C-12.2. Moment at face of column vs. story drift. 2597
In accordance with the design procedure, the length of the yielding section of 2598
the Links must increase with increasing beam depth. This leads to the need 2599
for more than one bolt on each side of the yielding area of the Link securing 2600
the BRP to the beam flange, and thicker Links mean more stress on the BRP, 2601
their bolts, and the beam flange. Whereas previously the BRP components 2602
were based on the empirical results of early testing, the buckling restraint 2603
assembly for the W36 tests previously discussed was designed according to a 2604
new set of requirements that add specific design provisions to the empirical 2605
minimum requirements. 2606
The inclusion of beams and columns of up to W36 profiles and Yield-Links 2607
of up to 6 in.2 yielding area opened up the connection to use in design space 2608
that had not been studied, specifically taller buildings. In accordance with 2609
the 2016 AISC Seismic Provisions, Section E3.6b.(b), additional analysis 2610
work complying with ASCE/SEI 7-16, Section 12.2.1.1 (ASCE, 2017), was 2611
requested by the CPRP committee. To meet this request, a FEMA P-695 2612
(FEMA, 2009) study was conducted to compare the performance of a steel 2613
SMF using both RBS connections and Strong-Frame connections. The basis 2614
of this comparison came from a previous FEMA P-695 study on 4-, 8-, 12-, 2615
and 20-story steel SMF using RBS connections and documented in a report 2616
by NIST (NIST, 2010). The NIST RBS frames were reanalyzed to verify the 2617
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new model was achieving similar results, and then the frames were 2618
redesigned for use with the Strong-Frame connection and evaluated using 2619
FEMA P-695 procedures. The results showed that for all building heights the 2620
buildings with the Strong-Frame connection had better resistance to collapse, 2621
and the calculated overstrength ranged from 3.00 to 3.63 for the Strong 2622
Frame buildings. Table C-12.1 shows the comparison between the computed 2623
A number of different beam sizes were used in the frame tests, with the 2632
largest being W36 (W920) profiles and the smallest being W8 (W200) 2633
profiles. End-plate Yield-Links are qualified for use on smaller beams in the 2634
W8 (W200) to W12 (W310) range (or equivalent built-up sections). Because 2635
the capacity-based design procedure forces inelastic behavior into the 2636
connection rather than the beam, in general, the width-to-thickness 2637
requirements of the AISC Specification (AISC, 2016b) apply. However, 2638
because the connection does rely on the beam flange and web to form part of 2639
the buckling restraint assembly for the yielding portion of the Link, the beam 2640
flange thickness is required to be checked according to the requirements in 2641
Section 12.9, Step 10, and also have a minimum thickness of 0.40 in. (10 2642
mm). Furthermore, the width-to-thickness value cannot exceed λr in AISC 2643
Specification Table B4.1a. Additionally, the capacity-based design procedure 2644
and connection performance (no plastic hinging in the beam) allows the beam 2645
stability bracing to be designed in accordance with the AISC Specification. 2646
The protected zone encompasses the shear connection and yielding portions 2647
of the connection, specifically the Yield-Links, and elements of the 2648
connection in contact with both. 2649
2. Column Limitations 2650
A number of different column sizes were used in the frame tests, with the 2651
largest being W36 (W920) profiles and the smallest being W6 (W150) 2652
profiles. Because only strong-axis connections were tested, beams are 2653
required to connect to column flanges. Where frames are detailed to create 2654
plastic hinging at the column base, the width-to-thickness requirements for 2655
highly ductile members apply in the first story. Otherwise, the requirements 2656
of the AISC Specification apply. Column lateral bracing requirements in the 2657
AISC Seismic Provisions (AISC, 2016a) are to be satisfied. An exception is 2658
provided to allow bracing the column at the level of the top flange of the 2659
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beam only if additional limits are placed on the column flexural design 2660
strength provisions of the AISC Specification to ensure the columns remain 2661
elastic outside the panel zones. The limits are noted in Step 13.2 of the 2662
Section 12.9 Design Procedure requirements. 2663
3. Bolting Limitations 2664
The connection testing specifically prequalified a number of bolts in the 2665
connection to be installed snug-tight. These include the Link flange-to-2666
column flange bolts, end plate-to-column flange bolts, and the shear-plate 2667
bolts. These same bolts may also be installed pretensioned if desired. The 2668
buckling restraint plate bolts are required to be installed only snug-tight. The 2669
Link stem-to-beam bolts are required to be installed pretensioned to prevent 2670
slip that would occur under design loads. In the prequalification testing, slip 2671
would typically start between 2 to 3% interstory drift, at which point the bolts 2672
went into bearing. No special preparation of either the Links or the beam 2673
flange surfaces in the test frames was done. The only prequalification 2674
requirement is that faying surfaces not be painted. 2675
12.4. COLUMN-BEAM RELATIONSHIP LIMITATIONS 2676
The requirements for the Strong Frame connection are similar to those of 2677
other prequalified SMF connections. Mpr, however, is calculated based on the 2678
probable maximum tensile strength of the Links, Mpr=Pr-link(d+tstem), where 2679
Pr-link is the probable maximum tensile strength of the Link calculated as the 2680
product of the yield area, the specified minimum tensile strength, Fu, and the 2681
ratio of the expected tensile strength to the specified minimum tensile 2682
strength, Rt. When Links are fabricated from ASTM A572/A572M Grade 50 2683
(345) plate material, this approach results in a 23% higher estimate of 2684
demand than what would be calculated if an approach equivalent to that of 2685
other SMF connections was used (Equation 2.4-1). Basing connection 2686
demand on the section properties and the expected tensile strength is used in 2687
numerous places in the design procedure and produces similarly higher 2688
demands when compared to typical SMF requirements. This is consistent 2689
with the overall goal of keeping nearly all inelastic demand in the replaceable 2690
Yield-Link elements and creating little if any inelastic demand in the 2691
members. Using this higher demand also applies to the evaluation of panel 2692
zone strength, which for the Strong Frame connection is done in accordance 2693
with the AISC Specification rather than the AISC Seismic Provisions. One 2694
effect of this requirement is the use of the AISC Specification = 0.90 rather 2695
than the AISC Seismic Provision v = 1.00 (AISC Seismic Provisions Section 2696
E3.6e), in conjunction with nominal resistance, Rn, calculated in accordance 2697
with AISC Specification Section J10.6. Adding to the differences in how Mpr 2698
is calculated results in panel zone shear demands approximately 26% higher 2699
than would be calculated if typical SMF design methodologies were used. 2700
12.5. CONTINUITY PLATES 2701
The need for continuity plates is determined in the design procedure by 2702
basing demand on the expected tensile strength of the Links as discussed in 2703
Commentary Section 12.4 and design strength as determined by the AISC 2704
Specification. As was used successfully in the qualification testing, fillet 2705
welds are permitted at the web and flanges of the column. 2706
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As discussed previously, initially the design demand for this weld was based 2708
on the expected tensile strength of the reduced portion of the Link. While this 2709
did permit the qualification testing to successfully meet the performance 2710
requirements of the AISC Seismic Provisions, the ultimate limit state for 2711
some of the tests was failure of this weld rather than the more desirable 2712
failure in the yielding area of the Link. As a result of the additional 2713
requirement to pass the FEMA P-795 component equivalency evaluation, 2714
which compared the Strong Frame connection performance to that of an RBS 2715
connection, this weld was changed to require either complete-joint-2716
penetration groove welds or double-sided fillet welds that develop the tensile 2717
strength of the unreduced portion of the Link. 2718
12.7. FABRICATION OF YIELD-LINK CUTS 2719
The fabrication requirements reflect production quality necessary to ensure 2720
the proper performance of the links. 2721
12.8. CONNECTION DETAILING 2722
The requirements of this section reflect the tested conditions and common 2723
allowances where appropriate. The connection is detailed to accommodate up 2724
to 0.07-rad rotation, which, along with frame flexibility, will accommodate 2725
the expected interstory drift without affecting any connection element other 2726
than the Yield-Links. Shear plate connection welds are required to develop 2727
the strength of the shear plate, and Yield-Link material thickness may vary 2728
from nominally 1/2-in. (13 mm) to 1-in. (25 mm) thick and fabricated from 2729
one of the three permitted steel grades. The previous specification of Link 2730
thickness tolerance was changed to reference ASTM A6. 2731
The stems of the pair of Yield-Links at each connection must be fabricated 2732
from the same heat of material to ensure minimum variability in actual Fy and 2733
Fu for the pair of Links in a connection. This is because imbalance of the 2734
Link strengths can drive additional force into the central pivot bolt of the 2735
connection. This force is parallel to and can be cumulative with the net axial 2736
connection force in the beam, which is also resisted by the central pivot bolt. 2737
Rather than include an explicit design procedure to accommodate unbalanced 2738
Link strength, it was decided at this time to simply use material from the 2739
same heat for the stems of each pair of Links at a given connection. 2740
In general, the topic of the potential adverse effects of unequal strength in the 2741
Links or flanges of a moment connection is not limited to just the Strong 2742
Frame connection. While the central pivot design of the Strong Frame 2743
connection in essence attempts to maintain the location of the plastic neutral 2744
axis at the centerline of the beam even if the Links are of different 2745
strengthsand thus create relatively even strain demands in each link for a 2746
given connection rotationthe same is not true for traditional built-up shapes 2747
that may have different flange strengths and form plastic hinges in the beam 2748
cross section. The neutral axis of the plastic section would shift toward the 2749
flange with higher strength, and uneven strain demands in the flanges would 2750
result. However, the effect on inelastic performance for this condition has not 2751
been studied, and currently there are no requirements to control flange 2752
strength in SMF connections using built-up sections subject to plastic 2753
hinging. 2754
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When using separate T-stub Yield Links, beam shear is transmitted directly 2755
to the column through the single plate shear connections and not through the 2756
Yield-Link, which affords the opportunity to use other than standard holes at 2757
the Link flange-to-column connection. When end-plate Yield-Links are 2758
used, shear is transferred from the beam to the column through the bolts that 2759
connect the end plate to the column. Because these bolts may be snug-tight, 2760
standard holes must be used in both the column and the end plate. Specific 2761
methods of fabricating bolt holes and the specification of surface roughness 2762
were removed because any approved method is acceptable, and surface 2763
roughness must already conform to the AISC Specification. 2764
Changes to the requirements for the buckling restraint assembly reflect the 2765
addition of specific design requirements in Step 10 of the design procedure. 2766
The maximum BRP bolt diameter has also been removed because the bolts 2767
are now specifically designed in Step 10. 2768
12.9. DESIGN PROCEDURE 2769
The design procedure for the Strong Frame connection parallels the design 2770
concepts for frames with other moment connections but is adapted to the 2771
specific configuration of the connection. Connection flexural strength is 2772
controlled by the strength of the Yield-Links, and shear strength is controlled 2773
by the strength of the shear-plate connection. This allows beams to be 2774
designed, if desired, to be unbraced yet stable under the combined effects of 2775
resulting from lateral loading. Unlike some historical PR moment 2777
connections, the Strong Frame connection is proportioned to remain elastic 2778
under the combined effects of design lateral and vertical loads, with the 2779
Yield-Links only experiencing inelastic behavior during seismic events in 2780
which the real seismic forces are expected to exceed the unamplified design 2781
seismic forces (Rex and Goverdhan, 2000). This permits the use of typical 2782
elastic analysis procedures similar to other SMF connections. However, like 2783
some historical PR moment connections, the beams are designed as simple 2784
span for gravity loads (Geschwindner and Disque, 2005). This facilitates 2785
post-earthquake repairs, should they be needed, by ensuring the beam is 2786
proportioned to support its design gravity loads even if the Links are removed 2787
during replacement. In addition to the various strength checks for frame 2788
members and elements of the connection, the PR nature of the Strong Frame 2789
connection requires a detailed stiffness check using actual connection 2790
stiffness to ensure lateral drift limits are met. This means that the lateral 2791
stiffness-to-mass and lateral yield strength-to-mass ratios are required to be 2792
the same as any other frame using SMF connections. As such, the code 2793
equations for base shear and period estimation are equally applicable to 2794
frames using the Strong Frame connection as they are to frames using other 2795
SMF connections. This was verified as part of the nonlinear response history 2796
study comparing Strong Frame and RBS connections discussed previously. 2797
For each of the archetype structures, the periods of the RBS frames and 2798
Strong Frame frames were virtually identical. 2799
The design process can be iterative, and Step 1 begins with suggestions on 2800
how to create trial values for sizes of the frame members and provides an 2801
initial estimate of story drift which is explicitly checked later in the design 2802
procedure. In addition to designing the beam as simply supported, Step 2 also 2803
suggests a deflection limit on the beam to limit member end rotations that 2804
would affect the connection. 2805
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Step 5 determines the width of the yielding portion of the Link based on the 2806
permitted thicknesses ranging from 1/2 in. (13 mm) to 1 in. (25 mm) and 2807
subject to limitations that include a maximum width of 6 in. (152 mm), which 2808
corresponds to the strongest Yield-Link that has been qualified. Testing 2809
showed that for the approved steel grades, if the length of the straight portion 2810
of the yielding section of the Link is proportioned such that the strain demand 2811
in that section does not exceed 0.085 when the connection is subjected to a 2812
rotation of 0.05 rad, the Link will possess sufficient toughness to enable the 2813
connection to meet the cyclic test performance requirements of the AISC 2814
Seismic Provisions; this is reflected in Step 6. 2815
In Step 7, the Link expected yield strength and probable maximum tensile 2816
strength are computed. The value of Rt is specified as 1.2 to reflect the proper 2817
value from AISC Seismic Provisions Table A3.1 for ASTM A572/A572M 2818
Grade 50 (345) plates, strips, and sheets. If the Link is fabricated from hot-2819
rolled structural shapes of ASTM A992/A992M or A913/A913M Grade 50 2820
(345) as permitted, the tabulated value of Rt =1.1 is used. 2821
In Step 8, the Link-to-beam flange connection is designed. Both here and in 2822
the web shear-plate connection, bolt bearing is required to be designed using 2823
bearing values that limit deformation at the bolt hole. The purpose of this is 2824
to again drive the inelastic response into the reduced portion of the Link and 2825
to keep other areas of the connection outside of the link essentially damage 2826
free to facilitate Link replacement should it be desired after a seismic event. 2827
In Step 9, the Yield-Link connection to the column flange is designed. Step 2828
9.1 determines bolt tension demand from either T-stub Yield-Links or end-2829
plate Yield-Links, as appropriate, for design of the bolts. While the end-plate 2830
Yield-Link is similar to the prequalified 4-bolt extended, unstiffened end 2831
plate (4E), the yield line mechanism in the end-plate Yield-Link is slightly 2832
different. Conservatively, the T-section two yield line model reflected in 2833
Equation 12.9-10 is used to design the end-plate Yield-Link. In Equation 2834
12.9-9, the second term is additional tensile force assigned to the two bolts 2835
directly adjacent to the shear tab due to the moment that results from the 2836
eccentric application of shear to the shear tab. Shear transfer from the end-2837
plate Yield-Link to the column flange is accomplished through the bolts at 2838
the compression flange location of the end plate, which are checked in Step 2839
9.1a. In Step 9.2, the required Yield-Link flange thickness, for a no prying 2840
action condition with a force limited by the probable maximum tensile 2841
strength of the Link as reflected in the calculation of rt in Step 9.1, is 2842
determined. 2843
Step 10 has been expanded to include specific design provisions for checking 2844
the elements of the buckling restraint assembly, which include BRP 2845
thickness, beam flange thickness, and BRP bolts. Step 10.1 determines the 2846
required minimum thickness of the BRP. Lcant is the lever arm from the start 2847
of the reduced region of the Yield-Link to the edge of the first spacer plate 2848
bolt hole, plus plate stretch length due to 0.05 rad of joint rotation. It 2849
represents the bending leverage on the BRP from the angled reinsertion 2850
contact of a link after a large tension deformation has stretched the link (0.05-2851
rad joint rotation) and then the link begins to be reinserted under 2852
compression. This was shown through detailed nonlinear finite element 2853
analysis (FEA) to be the controlling action for determining BRP thickness. 2854
In Step 10.2, the beam flange is checked for prying action from BRP bolt 2855
forces developed during full compression insertion into the buckling restraint 2856
assembly. Equation 12.9-14 is the same as the AISC Steel Construction 2857
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Manual (AISC, 2017) prying equation (Equation 9-17a). The derivation of 2858
Tux is based on inelastic column buckling theory using the tangent modulus of 2859
elasticity. In comparison to FEA analysis, results predicted the yield lines 2860
from Dowswell (2011) provided the best correlation with the design 2861
procedure yielding conservative results. In Step 10.3, bolt size is determined 2862
from consideration of tension induced from constrained weak axis buckling 2863
plus shear due to friction associated with the constrained weak axis buckling, 2864
or from shear determined from in-plane buckling due to strong-axis buckling 2865
only. 2866
Step 11 is a procedure for calculating the actual connection stiffness for use 2867
in checking frame drift and connection behavior. The Link stiffness is 2868
calculated as three springs in series, where the springs represent the 2869
stiffnesses of the Link flange in bending, the yielding portion of the link stem 2870
under axial load, and the nonyielding portion of the Link stem under axial 2871
load. Once the axial stiffness of the Links is computed, the connection can 2872
either be modeled with appropriate geometry using discrete axial elements to 2873
represent the top and bottom links at a connection, or an equivalent rotational 2874
spring can be determined and used in the modeling. As seen in Figure C-12.1, 2875
this approach has been shown to be very effective for modeling both the 2876
elastic and inelastic behavior of the connection (Pryor and Murray, 2013). 2877
2878
Fig. C-12.1 Testing vs. FEA analysis for frame modeled with 2879
all material nonlinearity in the Yield-Link elements. 2880
Step 11.2 requires that the frame, using the actual Strong Frame connection 2881
properties, meets the required drift limit and that the connection response is 2882
elastic under design load combinations (not including amplified seismic load 2883
combinations). The calculation of required shear in Step 12 is analogous to 2884
that used in designing RBS connections. Because a plastic hinge is not 2885
formed in the beam in Strong Frame connections, the value of Lh is the 2886
distances between the rotational points in the shear-plate connections rather 2887
than between the centers of plastic hinges. The user is directed to the 2888
Commentary for Chapter 5, Reduced Beam Section (RBS) Moment 2889
Connection, for additional information. 2890
Required member checks are in Step 13. Step 13.1 requires the beams to be 2891
checked using the AISC Specification under combined demand that consists 2892
of the maximum probable end moments, axial forces considering either the 2893
maximum that the system can deliver, or amplified seismic loads and gravity 2894
loads. If the designer chooses, beam size can be selected to meet the 2895
requirements of the AISC Specification under this combined loading without 2896
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
lateral bracing. In Step 13.2, column design demand is determined from load 2897
combinations that include seismic effects derived from either the maximum 2898
that the system can deliver or the overstrength seismic loads for both axial 2899
force and moment [the exception in AISC Seismic Provisions Section 2900
D1.4a(b) allowing one to ignore overstrength level moments when checking 2901
the column is not permitted for designs using the Strong Frame connection.] 2902
The design strength of the column outside the panel zone is not permitted to 2903
exceed bFySx, where b =0.90 even if otherwise permitted by AISC 2904
Specification Section F2 when column bracing is only provided at the level of 2905
the top flange of the beam. 2906
In Step 15, the shear plate and beam web are designed in accordance with the 2907
AISC Specification to permit hinging about a central rotation point while 2908
resisting the beam shear and axial force demand determined from capacity-2909
based design principles. In Step 15.1, note that the bolt shear demand is 2910
controlled by the shear force on the central bolt in the connection because it 2911
takes its portion of the vertical shear reaction in combination with its portion 2912
of the axial loads being transferred from the beam to the column, combined 2913
using the square root of the sum of the squares (vector sum) rule. 2914
Analogous to a beam flange force, in Step 16 the maximum probable axial 2915
strength of the Yield-Link is used to calculate panel zone shear demand. As is 2916
the case for typical connections, Link strengths are summed for double-sided 2917
connections. 2918
Borrowing from the bolted unstiffened and stiffened extended end-plate 2919
moment connection provisions in Chapter 6, Step 18 provides an analogous 2920
design procedure for checking the column flanges for flexural yielding based 2921
on the maximum probable tensile strength of the Yield-Link. 2922
If the design strength of the column web or flange without continuity plates 2923
or stiffeners is insufficient to support the maximum probable tensile strength 2924
of the Yield-Links, the design requirements for the stiffeners or continuity 2925
plates are in Step 19. Fillet welds are permitted at both column web and 2926
flange connections to the continuity plates or stiffeners. 2927
2928
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
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2930
2931
CHAPTER 11 2932
SIDEPLATE MOMENT CONNECTION 2933
GSA (2008), “GSA Steel Frame Bomb Blast & Progressive Collapse Test Program 2934
(2004-2007) Summary Report,” January 10, prepared by MHP Structural Engineers 2935
for the U.S. General Services Administration (GSA), Office of the Chief Architect 2936
(OCA), Washington, D.C. 2937
Hodgson, I.C., Tahmasebi, E. and Ricles, J.M. (2010a), “Cyclic Testing of Beam-to-2938
Column Assembly Connected with SidePlate FRAME Special Moment Frame 2939
Latham, C.T., Baumann, M.A. and Seible, F. (2004), “Laboratory Manual,” Structural 2965
Systems Research Project Report No. TR-97/09, May, Charles Lee Powell 2966
Structural Research Laboratories, University of California, San Diego, La Jolla, 2967
Calif. 2968
Minh Huynh, Q. and Uang, C.M. (2012), “Cyclic Testing of SidePlate Steel Moment 2969
Frame for SMF Applications,” Structural Systems Research Project Report No. TR-2970
12-02, October, Charles Lee Powell Structural Research Laboratories, University of 2971
California, San Diego, La Jolla, Calif. 2972
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
Mashayekh, A. and Uang, C.M. (2016), “Cyclic Testing of Bolted SidePlate Steel 2973
Moment Frame Connections for SMF Applications: H and U Series,” Structural 2974
Systems Research Project Report No. TR-16-01, March, Charles Lee Powell 2975
Structural Research Laboratories, University of California, San Diego, La Jolla, 2976
Calif. 2977
Reynolds, M. and Uang, C.M. (2017), “Cyclic Testing of Bolted SidePlate Steel Moment 2978
Frame Connections for SMF Applications: Specimens U4 and U5,” Structural 2979
Systems Research Project Report No. TR-17-02, June, Charles Lee Powell Structural 2980
Research Laboratories, University of California, San Diego, La Jolla, Calif. 2981
Reynolds, M. and Uang, C.M. (2018), “Cyclic Testing of Bolted SidePlate Steel Moment 2982
Frame Connections for Biaxial SMF Applications: B Series Specimens,” Structural 2983
Systems Research Project Report No. TR-18-02, July, Charles Lee Powell Structural 2984
Research Laboratories, University of California, San Diego, La Jolla, Calif. 2985
Richards, P. and Uang, C.M. (2003), “Cyclic Testing of SidePlate Steel Frame Moment 2986
Connections for the Sharp Memorial Hospital,” Structural Systems Research Project 2987
Report No. TR-2003/02, March, Charles Lee Powell Structural Research 2988
Laboratories, University of California, San Diego, La Jolla, Calif. 2989
Richards, P. and Uang, C.M. (2003), “Cyclic Testing of SidePlate Steel Frame Moment 2990
Connections for Children’s Hospital Los Angeles,” Structural Systems Research 2991
Project Report No. TR-2003/03, May, Charles Lee Powell Structural Research 2992
Laboratories, University of California, San Diego, La Jolla, Calif. 2993
Trautner, J.J. (1995), “Three-Dimensional Non-Linear Finite-Element Analysis of MNH-2994
SMRF™ Prototype Moment Connection,” System Reliability of Steel Connections 2995
Research Report No. 1, Department of Civil Engineering, University of Utah, Salt 2996
Lake City, Utah. 2997
Uang, C.M. and Latham, C.T. (1995), “Cyclic Testing of Full-Scale MNH-SMR Moment 2998
Connections,” Structural Systems Research Project Report No. TR-95/01, March, 2999
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Diego, La Jolla, Calif. 3001
Uang, C.M., Bondad, D. and Noel, S. (1996), “Cyclic Testing of the MNH-SMR Dual 3002
Strong Axes Moment Connection with Cruciform Column,” Structural Systems 3003
Research Project Report No. TR-96/04, May, Charles Lee Powell Structural 3004
Research Laboratories, University of California, San Diego, La Jolla, Calif. 3005
3006
CHAPTER 12 3007
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AISC (2017), Steel Construction Manual, 15th Ed., American Institute of Steel 3009
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ASCE (2010), Minimum Design Loads for Buildings and Other Structures, ASCE/SEI 7-3011
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3013
ASCE (2016), Minimum Design Loads and Associated Criteria for Buildings and Other 3014
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AMERICAN INSTITUTE OF STEEL CONSTRUCTION
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