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TitleSeismic-Design-for-Architects
PublisherArchitectural Press
ISBN 139780080888255
LanguageEnglish
File Size7.0 MB
Total Pages296
Table of Contents
                            Front cover
Seismic design for architects: outwitting the quake
Copyright page
Contents
Foreword
Preface
Acknowledgements
Chapter 1 Earthquakes and ground shaking
	Introduction
	Understanding earthquakes
	Earthquake magnitude and intensity
	The nature of earthquake shaking
	Importance of ground conditions
	References and notes
Chapter 2 How buildings resist earthquakes
	Introduction
	Nature of seismic forces
	Factors affecting the severity of seismic forces
	Resisting seismic forces
	Torsion
	Force paths
	Notes
Chapter 3 Seismic design approaches
	Introduction
	Historical overview
	Current seismic design philosophy
	References and notes
Chapter 4 Horizontal structure
	Introduction
	Diaphragms
	Transfer diaphragms
	Bond beams
	Collectors and ties
	Note
Chapter 5 Vertical structure
	Introduction
	Shear walls
	Braced frames
	Moment frames
	Mixed systems
	References
Chapter 6 Seismic design and architecture
	Introduction
	Integrating seismic resisting structure and architecture
	How much structure is needed?
	Special structures
	Contemporary architecture in seismic regions
	Case study: the Villa Savoye
	References and notes
Chapter 7 Foundations
	Introduction
	Seismic foundation problems and solutions
	Foundation types
	Foundation investigations
	Retaining structures
	References and notes
Chapter 8 Horizontal configuration
	Introduction
	Torsion
	Re-entrant corners
	Diaphragm discontinuities
	Non-parallel systems
	Pounding and separation
	Bridging between buildings
	References and notes
Chapter 9 Vertical configuration
	Introduction
	Soft storeys
	Short columns
	Discontinuous and off-set walls
	Setbacks
	Buildings on sloping sites
	References and notes
Chapter 10 Non-structural elements: those likely to cause structural damage
	Introduction
	Infill walls
	Staircases
	References
Chapter 11 Other non-structural elements
	Introduction
	Cladding
	Parapets and appendages
	Partition walls
	Suspended ceilings and raised floors
	Mechanical and electrical equipment
	Building contents
	References
Chapter 12 Retrofitting
	Introduction
	Why retrofit?
	Retrofit objectives
	Retrofit approaches
	Retrofit techniques
	Non-structural retrofit
	Historic buildings
	References
Chapter 13 Professional collaboration and communication
	Introduction
	Client
	Design team
	Contractor
	Post-earthquake
	References and notes
Chapter 14 New technologies
	Introduction
	Seismic isolation
	Dampers
	Damage avoidance
	Innovative structural configurations
	Structural design approaches
	Other developments
	References
Chapter 15 Urban planning
	Introduction
	Planning
	Tsunami
	Fire following earthquake
	Interdisciplinary interaction
	References and notes
Chapter 16 Issues in developing countries
	Introduction
	Design
	Construction
	Resources
	References
Chapter 17 Earthquake architecture
	Introduction
	Expression of seismic resistance
	Expression of structural principles and actions
	Seismic issues generating architecture
	References and notes
Chapter 18 Summary
Resources
	Introduction
	Institutions and organizations
	Publications
Index
	A
	B
	C
	D
	E
	F
	G
	H
	I
	J
	K
	L
	M
	N
	O
	P
	Q
	R
	S
	T
	U
	V
	W
                        
Document Text Contents
Page 2

SEISMIC DESIGN FOR ARCHITECTS
OU TW ITTING TH E QU A KE

Page 148

HORIZONTAL CONFIGURATION 133

torsional rotation about the stiffer and stronger left-hand area. Shaking
in the x direction highlights the same configuration problem.

The attitude of most codes towards re-entrant corners is to require
structural engineers to undertake a 3–D dynamic analysis where
the length of a projecting area of building causing a re-entrant cor-
ner exceeds approximately 15 per cent of the building plan dimension
(Fig. 8.12 ). An engineer will design the re-entrant structure to avoid
either diaphragm tearing or excessive horizontal deflections. This can
be achieved by fine-tuning the relative stiffness of the wings. However,
if they are long or their diaphragms weakened by penetrations for ver-
tical circulation or other reasons in the critical region where they join,
that approach may not be structurally sound. The building might best
be separated into two independent structures.

Separation is a common solution for re-entrant corner buildings ( Fig.
8.13 ). How it is achieved is explained later in this chapter. Although a
building might be perceived as a single mass if its blocks are seismically
separated, it actually consists of two or more structurally independ-
ent units, each able to resist its own inertia forces including torsion.
Where possible, separation gaps are provided adjacent to, or through,
areas where floor diaphragms are penetrated or discontinuous.

▲ 8.10 Typical re-entrant corner forms.

▲ 8.12 A typical
definition of an irregular
re-entrant configuration is
where A
0.15B.

▲ 8.13 Irregular plan configurations
improved by seismic separation gaps.

▲ 8.11 The dynamic response of a
re-entrant configuration and potential
floor diaphragm damage area.

Large horizontal
deflection. Possible
column damage

Potential area of
diaphragm damage

Direction of
shaking

Small deflection

y

x

Direction of
shaking

Page 149

134 SEISMIC DESIGN FOR ARCHITECTS

DIAPHRAGM DISCONTINUITIES

In the ideal world of the structural engineer, diaphragms in buildings
are not penetrated by anything larger than say a 300 mm diameter
pipe. Diaphragms are also planar and level over the whole floor plan.
However, the real world of architecture is quite different, because in
most buildings quite large penetrations are required for vertical circula-
tion such as stairways and elevators. Building services, including air ducts
and pipes also need to pass through floor slabs and in the process intro-
duce potential weaknesses into diaphragms.

Chapter 4 outlines the roles and requirements of diaphragms. It lik-
ens diaphragms to horizontal beams resisting and transferring hori-
zontal inertia forces to their supports which, in this case, consist of
vertical structural systems such as shear walls or moment frames. It
explains how penetrations are acceptable structurally, provided they
respect the shear force and bending moment diagrams of a diaphragm.
Recall that the web of a diaphragm resists shear forces, while perim-
eter diaphragm chords acting in tension or compression, resist bend-
ing moments.

The size of a penetration can be large enough to ruin the structural
integrity of a diaphragm altogether. Consider the case of a simple rec-
tangular diaphragm spanning between two shear walls that act in the
y direction ( Fig. 8.14 ). What are the structural options if a full-width
slot is required? The slot destroys the ability of the diaphragm to span
to the right-hand wall. If the purpose of the slot is to introduce light
or services through the diaphragm one option is to bridge the slot
by introducing a section of steel bracing ( Fig. 8.15(a) ). If designed and
connected strongly enough it restores the original spanning capability
of the diaphragm. Alternatively, if the geometry of diagonal members
isn’t acceptable aesthetically a horizontal vierendeel frame, with its far
larger member sizes, can be inserted to restore structural function
(Fig. 8.15(b) ). In both solutions, light and services can pass between
structural members.

If the intention of the penetration in Fig. 8.14 is to provide a staircase,
then both previous options are unacceptable. It is now impossible for
the diaphragm to transfer forces to the right-hand shear wall. The only
option is to no longer consider that wall as a shear wall but to pro-
vide a new shear wall to the left of the penetration. Now a shortened
diaphragm spans satisfactorily between shear walls. The force path has
been restored. All that remains to complete the design is to stabilize
the right-hand wall for x direction forces by tying it back to the newly

Shear wall

y

x

Slot in diaphragm

Diaphragm

Plan

Plan

▲ 8.14 A slot in the diaphragm destroys
its ability to span between shear walls for y
direction forces. (X direction structure not
shown.)

Vierendeel frame

Plan
(b)

y

x

Plan
(a)

Diagonal steel
bracing across slot

▲ 8.15 Plans of two diaphragms where
structural integrity across a slot is restored by
steel bracing and frame-action.

Page 295

280 INDEX

Restraints , 184
Retaining structures , 121–2

basements , 122
Retrofi tting , 18 , 37 , 187–205 , 235 , 252

adjacent buildings , 195
approaches , 192–5
assessment , 190–1
historic buildings , 203–4
non-structural elements , 202–3
objectives , 191–2
reasons for , 189–90
techniques , 195–203

Return period , 8
Richter scale , 9
Rocking , 119
Roof band see Bond beam
Russia , 238

San Fernando earthquake ,
179, 239

San Francisco , 8 , 34 , 138 , 188–9 , 234
International Airport , 221
Museum of Modern Art , 105–6

Saunders, Mark , 138
Scawthorn, Charles , 239
Schools , 40 , 243
Seattle Public Library , 107
Seismic see Earthquake
Seismic design:

force , 23
history of , 33–8
philosophy of , 34–42

Seismic forces see Inertia forces
Seismic isolation , 218–24 , 255

retrofi tting , 202
Seismic joints see Separation gaps
Seismic map , 9

hazards , 234–5
vulnerability , 235

Seismic zone , 100
Seismograph , 9, 10 , 12 , 260
Separation gaps , 128, 133, 137–9,

146–7, 155, 159, 163, 177–80,
195, 203, 211, 214, 222, 252–5,
267

Separation of gravity and seismic
systems, 97–8 , 146

Services (see also Mechanical
systems ), 97, 115

Setbacks , 154–5
Shape memory alloys , 230
Shear failure:

reinforced concrete , 44 , 46
Shear forces , 25 , 32 , 51 , 257
Shear walls , 64–76 , 95 , 130 , 163 ,

198–200 , 246 , 256–8 , 267
coupled , 75–6
ductility , 73–5
materials , 66 , 69–73
mixed system , 90 , 267
penetrations , 68
sloped , 67
structural requirements , 68–73

Shell structures , 102–4
Shock absorbers see Dampers
Short columns , 148–51 , 191 ,

246, 265
Shotcrete , 198
Sinha and Adarsh , 244
Slicing , 259
Sliding , 260
Sliding joints , 140 , 169–70 , 254
Slope instability , 234
Sloping site , 149 , 155
Soft storey , 91 , 144–9 , 161 , 163 , 191 ,

246 , 254 , 265
Soil:

failure , 46
infl uence of , 10, 13, 23 , 101
natural frequency , 15
shaking amplifi cation , 13 , 114 , 220
soft , 10 , 14 , 93 , 234
Spandrel beams , 147–8

Spandrel panels , 147
Splitting , 260
Staggered wall , 153
Staircases , 168–70 , 203
Strapping , 256
Strengthening see Retrofi tting
Structural design approaches , 229–31
Structural footprint , 42 , 93 , 101 , 207
Structural fuse , see also Plastic hinge ,

24–5 , 38 , 41–6 , 53 , 78 , 86–7 , 99 ,
153 , 214 , 255 , 257

Page 296

INDEX 281

Structural principles and actions:
expression of , 255–8

Subduction , 4
Subsidence , 117
Sumatra earthquake , 237
Surface fault rupture , 118
Suspended ceilings , 3 , 182

Taiwan , 20
Teamwork , 208
Tectonic plates , 1 , 4–5

continental plate , 4
location , 5
movement , 4–7
oceanic plate , 4
Tension membranes , 102

Timing of structural design , 96 , 208 ,
211 , 266

Tokyo , 2 , 33 , 109 , 239
Imperial Hotel , 228 , 253

Torsion , 11, 16, 27–8 , 65 , 97 , 127 ,
128–32 , 152 , 162 , 169 , 193 , 246 ,
267

Torsionally unbalanced system , 131
Transfer diaphragms , 56–8 , 152 , 154
Trusses:

horizontal , 54
vierendeel , 55

Tsunami , 9 , 237–8
Turkey , 153 , 240 , 243

Underground structures , 122
Uniform Building Code , 35
Unreinforced masonry:

buildings , 51 , 187
parapets , 181
walls , 195–8

Upgrading see Retrofi tting

Urban planning , 233–40 , 253
USA , 38 , 163 , 180 , 191 , 193 , 213 , 218 ,

223 , 227 , 228 , 261
US Geological Survey , 271
Uzbekistan , 244

Veneer , 175–6
Venezuela , 127 , 246
Vernacular architecture , 33
Vertical accelerations:

need to design for , 18 , 218
Vertical confi guration:

discontinuous walls , 151–3
irregularities , 143–55 , 191 , 193 ,

246 , 267
off-set walls , 151–3
short columns , 148–51
sloping site , 149
soft storeys , 144–8

Vertical structure , 63–91 , 98–9 , 193 ,
267

how much is needed , 99–102
number of elements , 101 , 130

Vibrofl otation , 116
Vierendeel frame , 134–5
Villa Savoye , 108–11

Waffl e slabs , 84
Weight reduction , 18 , 194
Wellington , 189 , 192 ,

Victoria University library , 223–4
Whiplash accelerations , 20
Wind force , 17 , 51 , 93
Windows , 179–81
Woods, Lebbeus , 261
World Housing Encyclopaedia , 248 ,

271
Wright, Frank Lloyd , 228 , 253

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