Timber and Steel Design Lecture 16 Lateral Resisting...
Transcript of Timber and Steel Design Lecture 16 Lateral Resisting...
� Basic of Bracing
� Braced Panels Arrangements
� Trussing to Reduce Story Drift
� Tabular Frame Concept
Timber and Steel DesignTimber and Steel Design
Mongkol JIRAVACHARADET
S U R A N A R E E INSTITUTE OF ENGINEERING
UNIVERSITY OF TECHNOLOGY SCHOOL OF CIVIL ENGINEERING
Lecture Lecture 1166 Lateral Resisting SystemLateral Resisting System
Wind & Building Pressure
windward
(+)
leeward
(-)elevator shaft
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
Basic of Bracing
H H
∆
h
Story Drift:
H
Tens
ion
H
Com
pres
sion
HTe
nsion
H
Tension
Dual-functioning Bracing:
X-bracing:
Opening
Vertical bracing
Vertical bracing
Vertic
al bra
cin
g
Vertic
al bra
cin
g
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
20,892
T
13,880 C
14,821
T
14,9
60 T
14,9
60 C
10,480 C
6,33
6 T
0
4,4
80 C
4,480 C
Bracing to Resist Wind Load
Building Frame to Resist Lateral Loads
To 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
Eccentrically Braced Frames (EBF)
To dissipate energy in the shear or moment links and protect the
remainder 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
EBF with W-Shape Bracing
Link length e
C of brace
must intersect
C of beam at
edge or inside
link
L
L
Stiffener plates both
sides with continuous
fillet welds to web
and flange
Intermediate stiffener
plate both sides for
link 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
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 Center
The central core is designed to carry part of
the vertical loads only.
The closely spaced tabular perimeter columns
act like a hollow tube supporting part of vertical
loads and all the horizontal loads.
Sears Tower - Chicago
World'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 Buildings
Rank Name City Country Feet Metres Stories
1 Petronas Tower 1 Kuala Lumpur Malaysia 1483 452 88
2 Petronas Tower 2 Kuala Lumpur Malaysia 1483 452 88
3 Sears Tower Chicago USA 1450 442 110
4 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 designed
to withstand wind.
The Petronas Twin
Towers were the
tallest buildings in the
world from April 15th,
1996 until October
17th, 2003 when
Taipei 101 (Financial
Center) was topped
out at 508m (1676ft).
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