ASIAN INSTITUTE OF TECHNOLOGY

SCHOOL OF ENGINEERING TECHNOLOGY

DESIGN OF STEEL STRUCTURES

TERM PROJECT

Sai Than Lwin (20000251)

Ni Ni Aung (20000238)

Nway Nandar Win (20000241)

May Hnin Ou (20000231)

Introduction

This project is about the design and analyze of a steel building which consists of four stores with

one story below grade.

i. LOCATION

Williamsport, Pennsylvania

41 N latitude and 77 W longitude.

ii. ARRANGEMENT OF THE STRUCTURE

Floor Area for each floor = 25 500 ft2

Floor total area =102 000 ft2

Bays

East west direction 30ft bays throughout

North south direction 45ft, 30ft and 45ft

14 6

6 13

13 6

15 6

4 th story

3 rd story

2 nd story

1 st story - Below grade

Figure Schematic plan

Figure Complete 3 dimensional computer model

iii. LATERAL LOAD RESISTING SYSTEM

East west direction Moment frames

North south direction Braced frames

iv. OTHER FEATURES

Faade is a lightweight metal curtain wall that extends above the roof surface.

6 ft screen wall around the middle bay of the roof to conceal mechanical equipment and roof access.

A two story atrium in the first floor

An opening in the second floor (An area bounded by A C 4 5)

Figure Lateral load resisting system

1) LOADS ON COLUMNS BASED ON TRIBUTARY AREAS

Figure - Arrangement of columns in the 1 st , 3 rd and 4 th floors

Figure - Arrangement of columns in

the 2nd floor

RC

Column Tributary

area

(ft2)

Dead load

(D)

(psf)

Live load

(Live

roof)(psf)

Snow load

(psf)

1.2D+0.5S

(ksf)

Load

(Kips)

Total

load

(kips)

RC1 168.75 20 20 102 75 12.65 12.65

RC2 675 20 20 102 75 50.62 50.62

RC3 562.5 20 20 102 75 42.18 42.18

RC4 337.5 20 20 102 75 25.3 25.3

RC5 1380 20 20 102 75 103.5 103.5

TC

Column Tributary

area

(ft2)

Dead load

(D)

(psf)

Live load

(Live

roof)(psf)

Reduced

live load

(Lred)(psf)

1.2D+1.6Lred

(ksf)

Load

(Kips)

Total

load

(kips)

TC1 168.75 80 80 66.46 202.39 34.15 46.80

TC2 675 80 80 43.1 164.96 111.35 161.97

TC3 562.5 80 80 45.3 168.48 94.77 136.95

TC4 337.5 80 80 52.66 180.256 60.86 86.16

TC5 1380 80 80 36.15 153.84 212.3 315.8

RC

TC

SC

BC

SC

Column Tributary

area

(ft2)

Dead load

(D)

(psf)

Live load

(Live

roof)(psf)

Reduced

live load

(Lred)(psf)

1.2D+1.6Lred

(ksf)

Load

(Kips)

Total

load

(kips)

SC1 168.75 80 80 66.46 202.39 34.15 80.95

SC2 675 80 80 43.1 164.96 111.35 273.32

SC3 562.5 80 80 45.3 168.48 94.77 231.72

SC4 337.5 80 80 52.66 180.256 60.86 147.02

SC5 1380 80 80 36.15 153.84 212.30 528.10

FC

Column Tributary

area

(ft2)

Dead load

(D)

(psf)

Live load

(Live

roof)(psf)

Reduced

live load

(Lred)(psf)

1.2D+1.6Lred

(ksf)

Load

(Kips)

Total

load

(kips)

FC1 168.75 80 80 66.46 202.39 34.15 115.10

FC2 675 80 80 43.1 164.96 111.35 384.67

FC3 562.5 80 80 45.3 168.48 94.77 326.49

FC4 337.5 80 80 52.66 180.256 60.86 207.88

FC5 1380 80 80 36.15 153.84 212.30 740.40

FC6 287.5 80 80 55.39 184.624 53.08 200.1

FC7 168.75 80 80 66.19 201.904 34.07 562.17

** Reduced live load Lred = Live load * (0.25 + 15/(A KLL))

K depends on the arrangement of the columns

Values for k can be obtained by tables in ASCE 7-10

2) Load on beams based on tributary areas

B1 B1 B1 B1 B1 B1 B1

B2 B2 B2 B2 B2 B2 B2

B3 B3 B3 B3 B3 B3 B3

B4 B4 B4 B4 B4 B4 B4

B6

B5

B7

ROOF

Joist/Column Tributary

area

(ft2)

Dead

load (D) (psf)

Live load (Live roof)(psf)

Snow load

(psf)

1.2D+0.5S

(psf)

Load

(Kips)

UDL

(kips/ft)

J1 270 20 20 102 75 20.25 0.45

J2 180 20 20 102 75 13.5

0.45

B5 135 20 20 102 75 10.125

0.225

B6 90 20 20 102 75 6.75

0.225

For beams B1, B2, B3 & B4

B4 10.125

For Floors 3,2,1

.

Joist Tributary

area (ft-sq)

Dead load

(D) (psf)

Live load

(psf)

Reduced

Live load

(psf)

1.2D+1.6L

(ksf)

Load

(kips)

UDL

(kips/ft)

J1 270 80 80 71.64 210.624 56.87 1.26

J2 180 80 80 83.25 229.2 41.26 1.38

B5 135 80 80 80 224 30.24 0.672

B6 90 80 80 80 224 20.16 0.672

Beam R

B1 28.35

B2 49.05

B3 49.05

B4 28.35

2. Design lateral bracing

L = 258 in Fy = 36 ksi Fu = 58 ksi A36 Steel

Ag (req) = PU / FY = 242.3/0.9(36) = 7.47 in2

Ae (req) = PU / FY = 242.3/0.75(58) = 5.57 in2

L/300 = 258/300 = 0.86 in

P U = 242.3 kips ( From Etabs )

2nd Floor

F = 88 kips h = 13 6

From similar triangles

PU = 1 x 88 x (21.57/15) = 126.54 kips

3rd Floor

F = 93 kips h = 14 6

From similar triangles

PU = 1 x 93 x (20.15/15) = 124.93 kips

4th Floor

F = 102 kips h = 15 6

From similar triangles

PU = 1 x 102 x (20.15/5) = 137.02 kips

Roof

F = 54 kips h = 14 6

From similar triangles

PU = 1 x 102 x (20.86/15) = 75.1 kips

Design brace frame for maximum PU

Ag (min) = PU / FY = 137.02/0.9(36) = 4.23 in2

Ae (min) = PU / FY = 137.02/0.75(58) = 3.15 in2

Select L-section: L5 x 5 x (Ag = 4.75 in2 , rx =1.53 )

Select C-section: C9 x 15 (Ag = 4.41 in2 , rx =3.40 )

Select I-section: W6 x 16 (Ag = 4.74 in2 , rx = 2.60 )

Ae / Ag = 0.745

By using maximum L = 21.57 ft.

L-section: L / rx = 169.18 300

C-section: L / rx = 76.13 300

W-section: L / rx = 99.55 300

4. Design of columns

As single columns

In order to carry out a conservative design all end conditions were considered as pin supports.

Hence the k value is taken as 1.

RC

Column Pu (Kips) KL(ft) Shape

RC1 12.65 14.5 W8x31 (230 kips)- least weight section

W10x33(233 kips)

W12x40(280 kips)

W14x48(332 kips)

RC2 50.02 14.5 W8x31 (230 kips)

RC3 42.18 14.5 W8x31 (230 kips)

RC4 25.3 14.5 W8x31 (230 kips)

RC5 103.5 14.5 W8x31 (230 kips)

RC

TC

SC

BC

6 14

6 13

13 6

15 6

TC

Column Pu (Kips) KL(ft) Shape

TC1 46.8 13.5 W8x31 (248 kips)- least weight section

W10x33(253 kips)

W12x40(304kips)

W14x48(361 kips)

TC2 161.97 13.5 W8x31 (248 kips

TC3 136.95 13.5 W8x31 (248 kips

TC4 86.16 13.5 W8x31 (248 kips

TC5 315.8 13.5 W8x40 (322 kips)- least weight

section w10x45(358 kips) w12x45

(343 kips)

W14x48(361 kips)

SC

Column Pu (Kips) KL(ft) Shape

SC1 80.95 13.5 W8x31 (248 kips)- least weight section

W10x33(253 kips)

W12x40(304kips)

W14x48(361 kips)

SC2 273.32 13.5 W8x35 (280 kips) least weight section

W10x39 (305 kips)

W12x40 (304 kips)

W14x 48 (361 kips)

SC3 231.72 13.5 W8x31 (248 kips)

SC4 147.02 13.5 W8x31 (248 kips)

SC5 528.10 13.5 W8x67 (560 kips)- least weight

section w10x60(581 kips) w12x58

(553 kips) W14x61(572 kips)

FC

Column Pu (Kips) KL(ft) Shape

FC1 115.10 15.5 W8x31 (212 kips)- least weight section

W10x33(213 kips)

W12x40(257 kips)

W14x48(304 kips)

FC2 384.67 15.5 W8x58 (417 kips)

W10x49(428 kips) - least weight section

W12x53(452 kips)

W14x61(515 kips)

FC3 326.49 15.5 W8x48 (340 kips)

W10x49(428 kips) - least weight section

W12x53(452 kips)

W14x53(338 kips)

FC4 207.88 15.5 W8x31 (212 kips) - least weight section

W10x33(213 kips)

W12x40(257 kips)

W14x48(304 kips)

FC5 740.4 15.5 W8 none

W10x88(789 kips)

W12x79(781 kips) - least weight section

W14x90(978 kips)

FC6 200.1 15.5 W8x31 (212 kips)

FC7 562.17 15.5 W8 none

W10x68(602 kips)

W12x65(639 kips) - least weight section

W14x68(576 kips)

Design of two story columns from 2nd floor to the 4th floor

Column Pu

(Kips)

KLx(ft) KLy(ft) Shape Checks

C1 (Braced

in both x

and y

direction)

80.95 13.5 13.5 W8x31 (248 kips)-

least weight section

W10x33(253 kips)

W12x40(304 kips)

W14x48(361 kips)

C2 (Braced

in both x

and y

direction)

273.32 13.5 13.5 W8x35 (280 kips)

W10x39(305 kips) -

least weight section

W12x40(304 kips)

W14x48(361 kips)

C3 (Braced

in both x

and y

direction)

231.72 13.5 13.5 W8x31 (248 kips)-

least weight section

W10x33(253 kips)

W12x40(304 kips)

W14x48(361 kips)

C4 (Braced

only in y

direction)

147.02 27 13.5 W8x31 (248 kips)-

least weight section

W10x33(253 kips)

W12x40(304 kips)

W14x48(361 kips)

KLx/[(rx/ry)]=27/1.72=15.69>kLy

Therefore use KL=16.69 and

W8x31to obtain Pn

Pn = 212 > Pu (147.02)

Therefore W8x31 is ok

C5 (Braced

in both x

and y

direction)

528.10 13.5 13.5 W8 x67 (560kips)

W10x60(581 kips)

W12x58(553 kips) -

least weight section

W14x61(572 kips)

5. Design of compression bracing members

Compression(max) force is equal to Tension(max) force which are indcued in section (3). It is

assumed, therefore, that the sections used to design the tension bracing will be same as

the section used for compression.

6. Design of Beams

If Wfloor is the floor load,

W = 6(Wfloor) / 1000 = 0.006 kips/ft.

R1 = R2 = 0.003 x 45W = 0.135 kips

For joist type 2,

If Wfloor is the floor load,

W = 6(Wfloor) / 1000 = 0.006 kips/ft.

R1 = R2 = 0.003 x 30W = 0.09 kips

For beams B1, B2, B3 and B4

Bending Moment Diagram,

Mmax = 18R

Bending Moment Diagram

Shear Force Diagram

Check for sections

W 16 x 31 :

Zx = 54.0 Lp = 4.13 Lr = 11.9 Lb = 6 ; Lp < Lb < Lr

Mp = 0.9 x 50 x 54/12

= 202.5 kips-ft

Mu =MpBF(Lb-Lp)

= 202.5 10.2 ( 6 4.13 )

= 183.43 kips-ft ; OK

Story Load (Psf) UDL (kips/ft) WL/2 (kips)

Roof 75 0.45 10.125 J1

75 0.45 6.75 J2

Beam R (kips) Mmax (kips-ft) Vmax (kips) Sections

RB1 10.125 182.25 20.25 W 16 x 31

RB2 16.875 303.75 33.75 W 21 x 44

RB3 16.875 303.75 33.75 W 21 x 44

RB4 10.125 182.25 20.25 W 16 x 31

Shear check

Vu = (1.0) (0.6Fy) (d) (tw) = 1.0 x 0.6 x 50 x 15.9 x 0.275 = 131.75 kips ; OK

W 21x 44 :

Zx = 95.4 Lp = 4.45 Lr = 13.0 Lb = 6 ; Lp < Lb < Lr

Mp = 0.9 x 50 x 95.4/12 = 357.75 kips.ft

Mu =MpBF(Lb-Lp) = 357.75 16.8 ( 6 4.45 ) = 331.71 kips.ft ; OK

Shear check

Vu = (1.0) (0.6Fy) (d) (tw) = 1.0 x 0.6 x 50 x 20.7 x 13 = 672.75 kips ; OK

For Floors 3,2,1

Bending Moment Diagram

10R 10R

Story Load (Psf) UDL (kips/ft)

WL/2 (kips)

Joist

3 to 1

210.624 1.26 28.35 J1

224 1.34 20.1 J2

Beam V(x) (kips)

M(x) (kips.ft)

Sections

B1 47.475 475.75 W 21 x 68

B2 33.6 336 W 21 x 48

B3 33.6 336

W 21 x 48

B4 47.475 475.75 W 21 x 68

Check for sections W 21 x 68 :

Zx = 160 Lp = 6.36

Mp = 0.9 x 160 x 50 /12= 600 kips.ft

Mu =MpBF(Lb-Lp)

= 600 18.8 ( 10 6.36 )

= 531.56 kips.ft ; OK

Lr = 18.7 Lb = 10 ; Lp < Lb < Lr

Shear check

Vu =273 kips ; OK

W 21x 48 :

Zx = 107, Lp = 6.09, Lr = 16.6, Lb =10 ; Lp < Lb < Lr

Mp = 0.9 x 50 x 107/12= 401.25 kips.ft

Mu =MpBF(Lb-Lp) = 401.25 14.7 (10 6.09) = 343.773 kips.ft ; OK

Story Beam Floor Load (Psf) UDL (kips/ft) Vx (kips)

Mx (kips.ft)

Sections

Roof

B5 75 0.225 2.53 14.24 W 8 x 28

B6 75 0.225

3.38

25.31

W 10 x 33

3 to 1

B5 210.624 1.05 11.81 66.44 W 8 x 31

B6 224 1.12

16.8

126

W 10 x 49

7. Redesign section with beams spanning in opposite direction in AC67 area

Dead load (D)

(psf)

Live load (L)

(psf)

Tributary area

(At) (ft2)

Lred (psf) 1.2D+1.6Lre

d

Wu (UDL)

(Kips/ft)

80 80 30 x 15 = 450 60 192 2.8

Dead load (D)

(psf)

Live load (L)

(psf)

Tributary area

(At) (ft2)

Lred (psf) 1.2D+1.6Lre

d

Wu (UDL)

(Kips/ft)

80 80 45 x 10 = 450 60 192 1.92

AC-6

Maximum bending moment Mu= moment due to the two point loads + moment due to

the uniform load = 43.2 x 15 + 0.96 x452/8

= 243 + 648 = 891 kip-ft

Unbraced length =15ft Shape = W 30 x 99 (Mn=918 kip-ft > Mu)

From the previous arrangement of joists the A67 =J1.

It has a UDL of 1.26 kips/ft. Hence the maximum moment is 319 kip-ft.

Therefore a lesser moment occurs when the joist are arranged in the previous way.

A67

Dead load (D)

(psf)

Live load (L) (psf) Tributary area

(At) (ft2)

Lred (psf) 1.2D+1.6Lred Wu (UDL)

(Kips/ft)

80 80 30 x (45/6) = 225 76.56 218.5 1.64

Maximum Bending moment Mu =1.64 x 302/8 = 184.5 kips-ft

Unbraced length = 30ft Shape=12x58(Mn >Mu)

From the previous arrangement of beams the A67 beam =B2 W 21 x 48.

It requires a more light section.

C67

Dead load (D)

(psf)

Live load (L) (psf) Tributary area

(At) (ft2)

Lred (psf) 1.2D+1.6Lred Wu (UDL)

(Kips/ft)

80 80 30 x (45/6) = 225 76.56 218.5 1.64

Mu = moment due to the two point loads + moment due to the uniform load

= 28.8 x 10 + 1.64 x302/8

= 288 + 184.5 = 472.5 kip-ft

Unbraced length = 10 ft Shape=W18x97 (Mn =782kipft>Mu)

From the previous arrangement of beams the C67 beam =B1 W 21 x 68.

Hence, more heavy section is required.

8. JOIST SECTION (KCS)

Required moment for L = 45 ft. span 1366 kips.in 20kcs4 1371 kips.in

Bridging section no.10 Required moment for L = 30 ft. span 607.5 kips.in 14kcs3 642 kips.in

Bridging section no.6

Both joists for spacing 30

5 = 6 ft.

9. SHEAR CONNECTIONS FOR BEAMS

pply 34 449()

= v= 68 0.441 = 30 ips

Yield Failure

= 0.9 36 14.3 = 463.325 ips

Rupture Failure

= 0.75 58 14.03 = 610.3 ips

For Single Angle Bearing and Tearout For the edge

For the middle

lc = 2 (0.8125) = 1.19 n

Tearout governs

= 1.2 lctFu = 0.75 1.2 [1.2 + 1.19] 5/46 58

= 48.78 ips >

Block Shear

= 0.6 58 0.53 + 58 0.8 = 69.84 ips

= 0.6 36 0.53 + 58 0.8 = 66.70 ips

= 0.75 64.84 = 48.63 ips > K

The block shear & tear out was done for single angle however since > for both cases the L section passes.

Plate Design

We considered the plate to have similar bolt arrangement.

If yield governs

tw 6 n = 1.37 n2

tw = 0.23 n

If rupture governs

tw 6 n 0.875t = 1.02 n2

t= 0.20 n

From available thickness,

t=

Check For Tearout and

Bearing

lc (from center) = 2 (0.8125) = 1.1875 in < 2

Tearout governs

Therefore use a greater

thickness, consider t = 3/8

Block Shear Check

v = 3 7/16 = 1.3125 n2

v = 1.3125 1.5(0.875) 7/16 = 0.738 n2

t= 7/16 3 0.5(0.875)] 7/16 = 1.12 n2

= 0.6 58 0.738 + 58 1.12 = 90.64 ips

= 0.6 36 1.3125 + 58 1.12 = 93.31 ips = 0.75 90.64 = 67.98 ips > K

FINAL DESIGN

Double Angle: 2Lx6x6x5/16

Rectangular Plate: 4x6x7/8

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