4_Pushover.pdf

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Diseo Ssmico por DesempeoDr. Jos Restrepo, Dr. Mario Rodrguez

INSTITUTO DE LA CONSTRUCCION Y GERENCIA - ICGTelefax: (01) 4217896 / [email protected] / www.construccion.org

Curso Internacional Pre IV Congreso de Estructuras

Diseo SsmicoDiseo Ssmico

por Desempeopor Desempeo

Lima, 21 al 23 de Junio 2010Lima, 21 al 23 de Junio 2010

Dr. Jos RestrepoDr. Jos Restrepo

Curso Internacional: Diseo Ssmico por Desempeo, Junio 2010

Pushover AnalysisPushover Analysis


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Classification

Force-basedat each step force increments are assigned,

Displacement-basedat each step displacement increments are assigned,system is solved for force increments

CONTROLLEDPARAMETER

Fixed-vector

vary during analysis

Adaptiverelative magnitude of increments varies step by step,increments are proportional to an instantaneous mode shape

VECTORSHAPE

Force-Based Fixed-Vector

Pushover Typical of building codes

Force increments prop. to a fixed approx. mode shape

en nver e - r angu ar s ape s assume or s mo e

i(3)i(2)i(1)

Vb(3)

Vb(2)

Fi(1)Fi(2)Fi(3)

Vb,maxVb

analysis stopswhen peak load

calculated=KT

-1Fr(3)

Vb(1)

r(1) r(2)

Vb(1)

givenfixed

Vb(2)Vb(3)

r

s near y reac e


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Force-Based Fixed-Vector

Pushover Typical of building codes

Force increments ro . to a fixed a rox. mode sha e

Often inverted-triangular shape is assumed for 1st mode

Advantages Easy implementation

Low computational effort

Drawbacks Cannot determine full-mechanism response (KT=0) Does not account for significant changes in the mode

shape (e.g. intermediate soft-story mechanism)

Force-Based Adaptive Pushover

Force increments prop. to an instantaneous mode shape

Eigenvalue solution required when KT changes

i(3)i(2)i(1)Fi(1)Fi(2)Fi(3)

Vb(3)

Vb(2)

Vb,maxVb

analysis stopswhen peak load

calculated=KT

-1F

Vb(1)

given byinstantaneouseigenvalue

Vb(2)Vb(3)

r(3)

Vb(1)

r(1) r(2)

r

s near y reac e


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Force-Based Adaptive Pushover Force increments prop. to an instantaneous mode shape


Advantages Changes in the mode shapes can be included

Drawbacks Cannot determine full-mechanism response (KT=0) High computational effort (repeated eigenvalue solutions)

Displacement-Based

Adaptive Pushover Opposite to force-based

Displ. increments prop. to instantaneous mode shape


i(3)i(2)i(1)Fi(2) Fi(1)Fi(3) i(4)

Vb(3)

Vb(2)

Vb,maxVb

analysis does not

given byinstantaneouseigenvalue

Vb(2)

calculatedF=KT

Vb(1)Vb(3)

r(3)

Vb(1)

r(1)r(2)

r

load is reached

r(4)


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Displacement-Based

Adaptive Pushover Dual to force-based

Displ. increments prop. to instantaneous mode shape

genva ue so u on requ re w en T c anges

Advantages Changes in the mode shapes can be included

Full-mechanism response can be evaluated

Drawbacks High computational effort (repeated eigenvalue solutions)

Simplified Pushover for Hw #1

Suitable for cantilever walls (only one plastic hinge at the

base)

orce s r u on s assume xe as an nver e

triangle

Vb Mb = Vb * heff

VbVb

Mb

Mb

V Mp.h.

eff


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Simplified Pushover for Hw #1

Base moments at

significative stages of M-

M

re a ons p or e ase

section are taken

Corresponding base shears and moment profiles are

calculated based on the assumed force distribution

Curvature profiles are determined knowing moment and

-

Curvatures are integrated to find the roof displacementat each stage

Roof displacements are associated to the corresponding

base shears and the pushover curve is found

Documents

4_Pushover.pdf