seismic retrofit methods

Seismic Retrofit:

Criteria, Weakness & Methods

Seismic Retrofit:

Criteria, Weakness & Methods

byPaul W. McMullin, SE, PhD

CRSA Green Brains SeminarJune 26, 2008

Seismic RetrofitSeismic Retrofit

Outline

Performance

Weaknesses

Options

Performance

Weaknesses

Options

SDEDC (1994)


Life Safety Through the Eyes of an SE

GET PEOPLEOUT THE

DOOR ALIVE

GET PEOPLEGET PEOPLEOUT THE OUT THE

DOOR ALIVEDOOR ALIVE



The purpose of this code is to establish the minimum requirements to

safeguard the public health, safety and general welfare…

(IBC 2006, 101.3)

The purpose of this code is to establish the minimum requirements to

safeguard the public health, safety and general welfare…

(IBC 2006, 101.3)



Structural Code generally does not consider:

Building economics

Business interruption losses

Sustainability

Structural Code generally does not consider:

Building economics

Business interruption losses

Sustainability


Building State After a Major Earthquake

Northridge EarthquakeMagnitude 6.7Estimated Economic

Loss $49.3 billion

Northridge EarthquakeMagnitude 6.7Estimated Economic

Loss $49.3 billion

PEER (2000)


Building State After a Major Earthquake:

Northridge

SDEDC (1994)


Building State After a Major Earthquake:

Northridge

FEMA (2000)


Performance Based Seismic Design:

Basics

Next generation seismic design methodology

Originally developed by FEMA for existing buildings

Applicable for new design

Considers each element’s energy dissipation capacity

Next generation seismic design methodology

Originally developed by FEMA for existing buildings

Applicable for new design

Considers each element’s energy dissipation capacity



Pairing

Target Building Performance Levels

Ope

ratio

nal P

erfo

rman

ce

Leve

l (1-

A)

Imm

edia

te O

ccup

ancy

P

erfo

rman

ce L

evel

(1-

B)

Life

Saf

ety

Per

form

ance

Le

vel (

3-C

)

Col

laps

e P

reve

ntio

n P

erfo

rman

ce L

evel

(5-

E)

Ear

thqu

ake

Haz

ard

Leve

l

Once every 100 years Once every 250 years Once every 500 years Once every 2500 years

a e i

m

b f j n

c g k o

d h l p



Levels & Acceleration

Performance levelsOperationalImmediate OccupancyLife Safety (IBC)Collapse Prevention

Performance levelsOperationalImmediate OccupancyLife Safety (IBC)Collapse Prevention

Acceleration OptionsTypical

50%/50 (1/100 year)20%/50 (1/250 year)10%/50 (1/500 year)2/3 of 2%/50 (IBC)2%/50 (1/2500 year)

Any probability between those listed above

Acceleration OptionsTypical

50%/50 (1/100 year)20%/50 (1/250 year)10%/50 (1/500 year)2/3 of 2%/50 (IBC)2%/50 (1/2500 year)

Any probability between those listed above


Common Damage


Common Weaknesses: Masonry

Unreinforced Masonry:Everything

Reinforced Masonry:(generally perform well)

Under-reinforcedUngrouted cellsConnections

Unreinforced Masonry:Everything

Reinforced Masonry:(generally perform well)

Under-reinforcedUngrouted cellsConnections


Common Weaknesses: Concrete

Ductility is big issue:Continuous beam

reinforcingHoop spacingLap splices

Under-reinforced (primary)

Ductility is big issue:Continuous beam

reinforcingHoop spacingLap splices

Under-reinforced (primary)


Common Weaknesses: Concrete

EQE (1999 Taiwan)


Common Weaknesses: Timber

DETAILINGCross grain bendingContinuityShear transfer

Undersized Elements

Nail pattern too far apart

DETAILINGCross grain bendingContinuityShear transfer

Undersized Elements

Nail pattern too far apart


Common Weaknesses: Steel

ConstraintFull penetration welds

Redundancy

Material Over strength

ConstraintFull penetration welds

Redundancy

Material Over strength

FEMA (2000)


Retrofit Options: Masonry

Unreinforced MasonryPost TensioningAdding PerforationsVertical Wall CoringSlottingShotcreteFiber Reinforced

Plastics (FRP)

Reinforced MasonryShotcreteFRP

Unreinforced MasonryPost TensioningAdding PerforationsVertical Wall CoringSlottingShotcreteFiber Reinforced

Plastics (FRP)

Reinforced MasonryShotcreteFRP


Retrofit Options: Masonry


Retrofit Options: Concrete

Shear Walls

Grade Beams

Steel or FRP Wrap of columns/ beamsApplication to flatsurface

Concrete jacketing (steel fiber reinforced)

Shear Walls

Grade Beams

Steel or FRP Wrap of columns/ beamsApplication to flatsurface

Concrete jacketing (steel fiber reinforced)


Retrofit Options: Timber

Structural Panel overlay

Increased nailingSheet metal blocking

Steel Connectors (Simpson is our friend)

Structural Panel overlay

Increased nailingSheet metal blocking

Steel Connectors (Simpson is our friend)


Retrofit Options: Timber


Retrofit Options: Steel

Cover Plates

Shear Walls (steel or concrete)

Braced Frames out of Moment Frames

Cover Plates

Shear Walls (steel or concrete)

Braced Frames out of Moment Frames


Preguntas?

Questions?Questions?