< Basic of Bracing
< Braced Panels Arrangements
< Trussing to Reduce Story Drift
< Tabular Frame Concept
Timber and Steel DesignTimber and Steel Design
Mongkol JIRAVACHARADETS U R A N A R E E INSTITUTE OF ENGINEERINGUNIVERSITY OF TECHNOLOGY SCHOOL OF CIVIL ENGINEERING
Lecture Lecture 1166 Lateral Resisting SystemLateral Resisting System
Wind & Building Pressure
windward(+)
leeward(-)
eleva
tor sh
aft
Wind pressure “pushes” outdoor air into the windward side of the building and “pulls” indoor air from the leeward side
Windward columns in tension
Leeward columns in compression
Sidesway of Buildings
Basic of BracingH H
∆
h
Story Drift:
H
Tens
ion
H
Compr
essio
n
H
Tens
ion
HTension
Dual-functioning Bracing:
X-bracing:
Single-story Multi-bay Bracing:
Bracing multistory buildings:
Opening
Vertical bracing
Vertical bracing
Ver
tical
bra
cing
Ver
tical
bra
cing
Bracing Around Floor Opening
H1
H2
H3
4.0 m
4.0 m
4.5 m
4.0 m
4,480 kg
6,000 kg
3,400 kg
13,880
30,575 30,575
14,9
60 T
30,5
75 C
20,89
2 T
13,880 C14
,821 T
14,9
60 T
14,9
60 C
10,480 C6,3
36 T
0
4,48
0 C
4,480 C
Bracing to Resist Wind Load
Building Frame to Resist Lateral LoadsTo dissipate energy in the moment-frame beams and to avoid soft story mechanisms
Earthquake
Beam-sway mechanism
Earthquake
Column-sway mechanism
“Soft-story”failure mode
Building Collapse in KOBE Earthquake (1995)
5th floor
Bracket-type Bracing:
Eccentrically Braced Frames (EBF)To dissipate energy in the shear or moment links and protect theremainder of the frame from inelastic action.
D-Braced EBF
e
Split-K-Braced EBF
e
V-Braced EBF
e e
Split-K is the best because large moments are avoided near the column
Forces in EBFD-Braced EBF Split-K-Braced EBF
e
M
V
P
e
M
V
P
EBF with W-Shape Bracing
Link length e
C of bracemust intersectC of beam at edge or insidelink
L
L
Stiffener plates bothsides with continuousfillet welds to weband flange
Intermediate stiffenerplate both sides forlink length e > 62.5 cm
Concentrically Braced Frames (CBF)To dissipate energy in yielding and buckling braces.
Diagonal braced CBF Inverted V-braced CBF V-braced CBF
X-braced CBF K-braced CBF
Braced Panels Arrangements
Trussing to Reduce Story Drift
(a) Bracing around Elevator Shaft
(b) Hat Truss (c) Belt Truss
Tabular Frame Concept Solid-wall tube
(a) (b)
World Trade Center - New York
Height: 417 and 415 meters
Ground Breaking: August 5, 1966
Opened: April 4, 1973 Terrorist attack: September 11, 2001
Typical Floor Plan of the World Trade CenterThe central core is designed to carry part ofthe vertical loads only.
The closely spaced tabular perimeter columnsact like a hollow tube supporting part of verticalloads and all the horizontal loads.
Sears Tower - ChicagoWorld's Tallest Building Until 1996
Height: 442 meters
Build: 1973
Terrorist attack: not yet
Actually nine 23-by-23 meters towers bundled together
World's Top 10 BuildingsRank Name City Country Feet Metres Stories
1 Petronas Tower 1 Kuala Lumpur Malaysia 1483 452 882 Petronas Tower 2 Kuala Lumpur Malaysia 1483 452 88
3 Sears Tower Chicago USA 1450 442 1104 Jin Mao Tower Shanghai China 1380 421 88
**5 Citic Plaza Guangzhou China 1,283 391 80
6 Shun Hing Square Shenzhen China 1,260 384 69
7 Empire State New York USA 1250 381 102
8 Central Plaza Hong Kong China 1227 374 78
9 Bank Of China Hong Kong China 1209 369 70
10 The Center Hong Kong China 1148 350 79
11 T & C Tower Kaohsiung Taiwan 1140 348 85
12 Aon Center Chicago USA 1136 346 80
13 John Hancock Chicago USA 1127 344 100
14 Burj al Arab Hotel Dubai UAE 1,053 321 60
15 Baiyoke Tower II Bangkok Thailand 1,050 320 90
Bundled Tube Structure
The Sears Tower is a bundled-tube structural design. The rigid outer walls act like the walls of a hollow tube. The Sears Tower is actually a bundle of nine tubes, and is considered one of the most efficient structures designedto withstand wind.
4.6 m typ.
3 @ 23 m = 69 m
3@
23m
=69
m
Typical Framing Plan
The Petronas TwinTowers were thetallest buildings in theworld from April 15th,1996 until October17th, 2003 whenTaipei 101 (FinancialCenter) was toppedout at 508m (1676ft).
ตึกที่สูงที่สุดในโลก
FUTURE TALLEST?Planned Shanghai tower may rise 500 meters.
MEGAFRAME Perimeter tube has columns,
belt trusses, bracing.