applied architectural structures: …faculty.arch.tamu.edu/media/cms_page_media/4350/notes16...“to...

1

F2009abn

sixteen

seismic design

Seismic Design 1Lecture 17

Applied Architectural StructuresARCH 631

lecture

© Reuters 2004

APPLIED ARCHITECTURAL STRUCTURES:

STRUCTURAL ANALYSIS AND SYSTEMS

ARCH 631

DR. ANNE NICHOLS

FALL 2015

Seismic Design 2

Lecture 16

Architectural Structures III

ARCH 631

F2007abn

Earthquake Design

• dynamic vs. static loading

– amplification of static affect

– time duration

– acceleration & velocity

F2009abn

Earthquake Design

• hazard types

– surface fault ruptures

– ground failures

– tsunamis (sea waves)


Architectural Structures IIIARCH 631

http://nisee.berkeley.edu/godden

Seismic Design 4

Lecture 16


ARCH 631

F2007abn

Earthquake Design

• hazard types: ground shaking

2

F2007abnSeismic Design 5Lecture 16


Earthquake Design

• fundamental considerations

– building configuration

• symmetry with respect to mass

– stiffness or vibration control

• symmetry with respect to lateral resistance mechanisms

• member sizes, rigidity, braces, dampers

– anchorage of parts and components

• seismic joints

– “tie the building together”

Seismic Design 6

Lecture 16


ARCH 631

F2007abn

Earthquake Design

• building response

Seismic Design 7

Lecture 16


ARCH 631

F2007abn

Earthquake Design


– seismic joints

– L, T, H

shapes bad



F2008abn

Earthquake Design


– center of mass

• ex.:

– center of rigidity

• ex. (R = 1/ δ):

– torsion (eccentricity)

NS

NS

WxW

xΣ

Σ=

y

yE R

xRr

Σ

Σ=

3

Seismic Design 8

Lecture 16


ARCH 631

F2007abn

• lateral ground movement

• drift

Low-Rise Response



F2007abn

Frequency and Period

• natural period of vibration

– avoid resonance

– hard to predict seismic period

– affected by soil

– short period• high stiffness

– long period• low stiffness

“To ring the bell, the sexton must pull on the downswing of the bell in time

with the natural frequency of the bell.”

F2007abnSeismic Design 10

Lecture 16


ARCH 631

Earthquake Design

• codes

– purpose is to provide a simple uniform

method of determining potential

earthquake forces in any location with

enough accuracy to ensure a safe and

economical building design

– National Earthquake Hazards

Reduction Program (NEHRP)

– evaluate structural response (spectrum) to

earthquake (motion vs. time)



F2007abn

Earthquake Design Loads

• derived from W & amplification factors

• at base of structure:

– Z, zone

– I, importance (1.0 – 1.5)

– C, stiffness related to period of vibration

– RW, response modifications

for building type (1.25 – 8)

• distribution per floor

– simple vs. tall -

WRZICWV =

Wh

hWxx

∑

4

F2012abn

Earthquake Design Loads (ASCE-7)

• at base of structure:

– W, usually dead load but can include some live load

– Cs, seismic design coefficient

– SDS, short period design spectral response acceleration

– SD1, one second design spectral response acceleration

– R, response modification factor

– I, importance factor

– T, building period

– S1, mapped one-second spectral acceleration Seismic Design 13Lecture 16


WCVS

=

)I/R(

SC DS

S=

)I/R(T

SD1

but not greater than

F2012abn

Earthquake Design Loads (ASCE-7)



F2009abn

Earthquake-Resistant Structures

• absorb energy input from ground motion

• pins can’t, rigid frames can– energy goes into forming

plastic hinges (ductility)

– continuous

– steel, timber or reinforced concrete

• redundancy helpful

• use rigid diaphragms

• horizontal members fail before verticalsSeismic Design 13Lecture 17


http://nisee.berkeley.edu/godden



F2007abn

Earthquake Design

• soft first stories

– problematic

– ground level story weaker than those above

• usually higher

• reduced strength in vertical elements

• significantly increased mass above

5



F2007abn

Earthquake Design

• want horizontal elements to fail before vertical elements do



F2007abn

Earthquake Design

• passive base isolation

– low stiffness layer

between foundation

and structure



F2007abn

Earthquake Design

• tuned mass damping systems



F2007abn

Earthquake Design

• dampers

• elastomer bearings

– neoprene or rubber

• sliding systems

• friction pendulum systems

6

F2011abn

Sendai Mediatheque, Japan, 2011



© Wizneko 2011

F2013abn

Damage Levels – FEMA



• Operational

– minimal or no damage to structure

– extremely low risk to life safety

• Immediate Occupancy

– minimal to no damage to structure, minor damage to non-structural,

– very low risk to life safety

F2013abn

Damage Levels – FEMA (cont.)



• Life Safety

– may have extensive damage to structure, some repair may be economically impractical

– low risk to life safety

• Collapse Prevention

– not suffered complete or partial collapse, may have severe internal damage to structure, likely complete economic loss

– damage that poses risk to life safety



F2007abn

Architectural Considerations

Video – Buildings at Risk

applied architectural structures: …faculty.arch.tamu.edu/media/cms_page_media/4350/notes16...“to...

Documents