TimberTimber andand SteelSteel DesignDesign

LectureLecture 1166 LateralLateral ResistingResisting SystemSystem

 Basic of Bracing  Braced Panels Arrangements  Trussing to Reduce Story Drift  Tabular Frame Concept

Mongkol JIRAVACHARADET S U R A N A R E E INSTITUTE OF ENGINEERING UNIVERSITY OF TECHNOLOGY SCHOOL OF CIVIL ENGINEERING Wind & Building Pressure

windward leeward Windward columns in tension (+) (-) elevatorshaft

Leeward columns in compression

Wind pressure “pushes” outdoor air into the windward side of the building and “pulls” indoor air from the leeward side Sidesway of Buildings Basic of Bracing Story Drift: ∆ H H

h

H n H io n s io s s e n r e p Dual-functioning Bracing: m T o C

H H T n e io n s s X-bracing: n io e n T Single-story Multi-bay Bracing:

Bracing multistory buildings: Bracing Around Floor Opening

Vertical bracing

Opening Vertical bracing Vertical Vertical bracing Vertical

Vertical bracing Bracing to Resist Wind Load

4,480 kg 4,480 C H1

T 4.0 m 6

0 3 ,3 6

6,000 kg 10,480 C C 4,480 H2 T 1 4.0 m 2 ,8 4 1 14,960 T 14,960 3,400 kg 13,880 C C 14,960 H3

T 2 9 4.5 m ,8 0 2 14,960 T 14,960 30,575 C 30,575

13,880

4.0 m 30,575 30,575 Building Frame to Resist Lateral Loads To dissipate energy in the moment-frame beams and to avoid soft story mechanisms

“Soft-story” failure mode

Earthquake Earthquake

Beam-sway mechanism Column-sway mechanism 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 the remainder of the frame from inelastic action. e e e e

D-Braced EBF Split-K-Braced EBF V-Braced EBF

Split-K is the best because large moments are avoided near the column Forces in EBF

D-Braced EBF Split-K-Braced EBF e e

M M

V V

P P EBF with W-Shape Bracing

Stiffener plates both Intermediate stiffener sides with continuous plate both sides for fillet welds to web link length e > 62.5 cm e and flange Link length

CL of brace must intersect CL of beam at edge or inside link 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 (b) Hat Truss (c) Belt Truss Elevator Shaft 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 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 1380 421 88 **5 Citic Plaza China 1,283 391 80 6 China 1,260 384 69

7 Empire State New York USA 1250 381 102

8 Central Plaza China 1227 374 78 9 Bank Of China Hong Kong China 1209 369 70 10 Hong Kong China 1148 350 79 11 T & C Tower Kaohsiung Taiwan 1140 348 85 12 Chicago USA 1136 346 80 13 John Hancock Chicago USA 1127 344 100 14 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. Typical Framing Plan

3 @ 23 m = 69 m 4.6 m typ. 3 @ 23 m = 69 m   

The Petronas Twin Towers were the tallest buildings in the world from April 15th, 1996 until October 17th, 2003 when (Financial Center) was topped out at 508m (1676ft). FUTURE TALLEST? Planned may rise 500 meters.

MEGAFRAME Perimeter tube has columns, belt trusses, bracing.