achitectural structures: s analysis and systems arch...

F2018abnSeismic Design 1

Lecture 16

Applied Architectural Structures

ARCH 631

sixteen

seismic design

lecture

© Reuters 2004

APPLIED ACHITECTURAL STRUCTURES:

STRUCTURAL ANALYSIS AND SYSTEMS

ARCH 631

DR. ANNE NICHOLS

FALL 2018


Lecture 16


ARCH 631

Earthquake Design

• dynamic vs. static loading

– amplification of static affect

– time duration

– acceleration & velocity


Lecture 16


ARCH 631

Earthquake Design

• hazard types

– surface fault ruptures

– ground failures

– tsunamis (sea waves)

http://nisee.berkeley.edu/godden


Lecture 16


ARCH 631

Earthquake Design

• hazard types: ground shaking


Lecture 16


ARCH 631

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”


Lecture 16


ARCH 631

Earthquake Design

• building response

../animations/splitheight.mov


Lecture 16


ARCH 631

Earthquake Design


– seismic joints

– L, T, H

shapes bad

../animations/reentrant.mov


Lecture 16


ARCH 631

Earthquake Design


– center of mass

• ex.:

– center of rigidity

• ex. (R = 1/):

– torsion (eccentricity)

NS

NSW

xWx

y

yE R

xRr


Lecture 16


ARCH 631

• lateral ground movement

• drift

Low-Rise Response


Lecture 16


ARCH 631

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.”

F2018abn

• 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)

Seismic Design 11

Lecture 16


ARCH 631

Earthquake Design


Lecture 16


ARCH 631

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

WhhW xx


Lecture 16


ARCH 631

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

WCVS

)I/R(

SC DS

S

)I/R(T

SD1

but not greater than


Lecture 16


ARCH 631

Earthquake Design Loads (ASCE-7)


Lecture 16


ARCH 631

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 verticals

http://nisee.berkeley.edu/godden


Lecture 16


ARCH 631

Earthquake Design

• soft first stories

– problematic

– ground level story weaker than those above

• usually higher

• reduced strength in vertical elements

• significantly increased mass above

../animations/soft_story_n.mov


Lecture 16


ARCH 631

Earthquake Design

• want horizontal elements to fail before

vertical elements do


Lecture 16


ARCH 631

Earthquake Design

• passive base isolation

– low stiffness layer

between foundation

and structure


Lecture 16


ARCH 631

Earthquake Design

• tuned mass damping systems


Lecture 16


ARCH 631

Earthquake Design

• dampers

• elastomer bearings

– neoprene or rubber

• sliding systems

• friction pendulum

systems

F2018abn

Sendai Mediatheque, Japan, 2011

Seismic Design 21

Lecture 16


ARCH 631

© Wizneko 2011

http://www.youtube.com/embed/heh5ITmYbRs

F2018abn

Damage Levels – FEMA

Seismic Design 22

Lecture 16


ARCH 631

• 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

F2018abn

Damage Levels – FEMA (cont.)

Seismic Design 23

Lecture 16


ARCH 631

• 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


Lecture 16


ARCH 631

Architectural Considerations

Video – Buildings at Risk

../animations/buildings_at_risk.wmv

achitectural structures: s analysis and systems arch...

Documents