100th anniversary earthquake conference commemorating the 1906

8/14/2019 100th Anniversary Earthquake Conference Commemorating the 1906

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Forell / Elsesser Engineers, Inc.

100th Anniversary

Earthquake ConferenceCommemorating the

1906 San Francisco Earthquake

Implementation of Base IsolationImplementation of Base Isolationin Retrofit Applicationsin Retrofit Applications

Presented bySimin Naaseh, SE, PrincipalMason Walters, SE, Principal

Forell/Elsesser Engineers, Inc.April 17th, 2006


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Impetus for Base Isolation of

Existing Buildings

Enhanced seismic protectionEnhanced seismic protection

Reduced extent ofReduced extent ofsuperstructure retrofitsuperstructure retrofit

Protection of historic fabricProtection of historic fabric

Protection of valuable contentsProtection of valuable contents

Cost advantageCost advantage


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Technical Issues Unique to

Base Isolation Retrofit

Isolation system is designedIsolation system is designedto meet certain thresholdsto meet certain thresholds

Limited existing structureLimited existing structure

capacitycapacity

Unique dynamic response ofUnique dynamic response ofthe structurethe structure

Limits on floor accelerationLimits on floor acceleration

Limits on moat dimensionLimits on moat dimension


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Planning and Design Challenges

Accommodating the isolatorAccommodating the isolatorspacespace

Accommodating the moatAccommodating the moat

Retrofitting the buildingRetrofitting the buildingappendages to accommodateappendages to accommodatefree movementfree movement

Retrofitting stairs and elevatorsRetrofitting stairs and elevatorsto accommodate largeto accommodate largedisplacementsdisplacements


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Construction Challenges

Minimize building vulnerabilityMinimize building vulnerabilityduring constructionduring construction

Minimize impact on brittleMinimize impact on brittle

elementselements

Isolator installation sequenceIsolator installation sequence


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Seismic Retrofit of San Francisco City Hall


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Historic Rotunda


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Major Earthquake Response Issues


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Fixed Base Response - Shear Walls


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Major Earthquake Response Issues


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Fixed Base Response


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Base Isolated Response


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Sequence of Construction


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New Foundation


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New Foundation


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New Foundation


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Column Jacking


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Column Cutting


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Installation of Base Isolators


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Perimeter Shoring


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Perimeter Side Beams


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Perimeter Side Beams


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Installed Isolators at Perimeter


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New Ground Floor


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New Shear Walls


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Berkeley Civic Center


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C

Isolators at Basement

Section Looking West


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C

Basement Wall / Jacking Pier

Construction Sequence


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C

Column Jacking / Isolator Installation

Construction Sequence


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Existing Condition


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Install Foundation Reinforcing


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New Foundation Built

I t ll F k f J ki Pi


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Install Formwork for Jacking Piers

Around Existing Columns


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Jacking Pier Construction


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Jacking Pier Built


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Temporary Jacks Installed


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Existing Column Cut


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Isolator Installed


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Isolator Installed


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Isolator Locking Plates Installed


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Steel Bracing Installed


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Locking Plates Removed

I l I ll d


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Isolators Installed

Base Isolation Response at


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Base Isolation Response at

Perimeter Wall


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Design an Construction

Problems and Solutions

Construction Problems and Solutions


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Construction Problems and Solutions

Sequence of operationsSequence of operations

Symmetry and balanceSymmetry and balance

Cutting and jackingCutting and jacking

PreloadingPreloading

Temporary lateral strengthTemporary lateral strength

Structure Types


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Structure Types

UnreinforcedUnreinforced masonry bearing wallmasonry bearing wall

Steel / masonry infillSteel / masonry infill

Reinforced concreteReinforced concrete


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Example:Unreinforced Masonry

Bearing Wall Building


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Bearing Wall Sequence


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Isolator Installedat Perimeter


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Example:Steel Framed Building

with Masonry Infill

Oakland City Hall


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Oakland City Hall

Identification of Existing


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g

Building Properties

Archaic materials and infill systemsArchaic materials and infill systems

Structures Modal frequenciesStructures Modal frequencies

Forced/Ambient Vibration TestsForced/Ambient Vibration Tests

Historic DataHistoric Data

OldOld AccelerogramsAccelerograms

Masonry infill exampleMasonry infill example

Identification of Existing


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g

Building Properties

Tests of Existing MasonryTests of Existing Masonry

InIn--situ cyclic testssitu cyclic tests

Obtain shear stressObtain shear stress--strain relation, Gstrain relation, G

Obtain diagonal cracking strain,Obtain diagonal cracking strain, ggcrcr

Use G for elastic modeling of structureUse G for elastic modeling of structure

UseUse ggcrcr to determine the limits ofto determine the limits ofacceptable interacceptable inter--story driftstory drift

In-Situ Masonry Test


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In Situ Masonry Test

Stress Versus Deflection


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Stress Versus Deflection

Local Wall Model


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Local Wall Model


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ETABS Model

(Non-Linear ANSR)


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Jacking of Existing Column


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g g

Column Cutting


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Example:Reinforced Concrete

Frame Buildings

Pasadena City Hall


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Building Section


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Showing Load Transfer

8

3

(E) Column

7

2

59

6

1(E) Footing

(to be Removed)

1

(E) Wall

(E) Basement

Grade

1 Shoring

2 Foundation

3

4

5

6

7

8

9

(E) Wall

Moat Cover

4

Grade Beam & S.O.G. Friction Pendulum Isolator PT Threadbar(Clamping Reinforcing)

Concrete Pedestal

Temporary Shoring

PT Conc. Transfer Girder

Concrete Slab

Installation of Isolators


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Utah State Capital Building


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OverallBasement

Plan


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Big Idea


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Rotunda base must be isolated withRotunda base must be isolated withremainder of buildingremainder of building

Main problemMain problem getting isolators beneathgetting isolators beneathrotunda footingrotunda footing

Below and Above approaches studiedBelow and Above approaches studied

Above approach safer to build, requiresAbove approach safer to build, requiresless excavationless excavation

Big Idea


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Existing concrete has relatively goodExisting concrete has relatively goodquality, strengthquality, strength

Maintain footingMaintain footing make it work as part ofmake it work as part ofnew transfer girdernew transfer girder

CompositeComposite

Allow new transfer structure to span toAllow new transfer structure to span toisolators on new foundations (fig)isolators on new foundations (fig)

New foundation can be built ahead ofNew foundation can be built ahead oftransfertransfer outside existing footingoutside existing footing

Existing Footing


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How to Achieve Composite Action and


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Transfer Load?

Stress Girders


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How to Achieve Composite Action and


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Locate andMark PT Ducts

on Flange

Transfer Load?

Rotunda Footing


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100th Anniversary


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Earthquake ConferenceCommemorating the

1906 San Francisco Earthquake

Implementation of Base IsolationImplementation of Base Isolation

in Retrofit Applicationsin Retrofit Applications

Presented bySimin Naaseh, SE, PrincipalMason Walters, SE, Principal

Forell/Elsesser Engineers, Inc.

April 17th

, 2006

100th anniversary earthquake conference commemorating the 1906

Documents