Team UCDSESMYihai Bao, YeongAe Heo, Zhiyu Zong

University of California, DavisApril 4th, 2008

Prediction for Progressive Collapse Resistance of a 2D RC frame

Outline

• Background• Methodology

– the alternate path method by General Services Administration (GSA, revised June 2003)

– nonlinear static, nonlinear dynamic • Models

– Macroscopic modeling approach– Beam column modeling: beam-column fiber model– Joint modeling: macro joint model

• Results– Dynamic response after removing first floor center column

– Response from static pushdown • Summary

Background

Glass Column

Testing frame at Northeastern University

Methodology: GSA Criterion

GSA criterion utilizes the alternate path method to ensure that progressive collapse does not occurScenario: instantaneous removal of a column in the

first storyStructural analysis for prescribed set of load

combinations and material strength factors Linear/Nonlinear Static Nonlinear Dynamic

Evaluating the potential for progressive collapse Strength requirements (DCR, Demand Capacity Ratio) Reinforcement detailing and ductility requirements

Methodology: Two Step Test

• First step– Dynamic loading: breaking the glass column with sudden impact

• Second step– Static loading: displacement controlled pull down if frame dose not

collapse during first step

Testing frame with dynamic loading

Northeastern University

Testing frame under pull down loading

Northeastern University

Models: Macroscopic Modeling

Macroscopic modeling approach– Using simplified models to predict a specific overall behavior

Advantages: computational efficiency; compatibility with traditional structural analysis models.

Disadvantages: complexities involved in development of an objective and transparent calibration procedures.

Finite element model

Beam fiber model

Macro joint model

Models: Materials

sk

bsk

Panel Shear Spring Property

Reference: Vecchio & Collins (1986)

Interface Shear Spring Property

Reference: Walraven (1981)

Concrete Property

Reference: Mander et al (1988)

Bond-Slip Property

Reference: Lowes & Altoontash (2003)

Bond-Slip

b

hy

ysb

y

y

ysb

e

y

ll

lhb

ebyyl

b

be

ll

dE

ffd

E

fffd

E

f

dxEA

lxd

E

fdx

A

xddsdss

ye

e

e

ye

22

0

8

1

4

1

8

1

)(ys ff

be

bse d

Afl

by

bysy d

Affl

ys ff

be

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b

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f

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xddxEA

Fdx

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8

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be

bse d

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For

For

With,

With,

Table: Average bond strengths as a function of steel stress state

and

Bond and bar stress distribution for a reinforcing bar anchored in a joint

From Lowes, L.N. & Altoontash, A. (2003) PEER Report

Interface shear

0

250

500

750

1000

1250

1500

1750

2000

2250

2500

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

Shear Displacement (in)

Sh

ear

Str

ess

(psi

)

w=0.0039 in / 0.1 mm

w=0.0079 in / 0.2 mm

w=0.0236 in / 0.6 mm

w=0.0394 in / 1.0 mm

w=0.0787 in / 2.0 mm

Walraven J.C. (1981)

Results

-0.4

-0.3

-0.2

-0.1

0

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Time (sec)

Vert

ical D

isp

lacem

en

t (i

n) test

prediction

Observed position of first bar fracture

Predicted position, “top bar”, of first bar

fracture

0

500

1000

1500

2000

2500

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Vertical Displacement (in)

Vert

ical

Loa

d (lb

)

test

prediction

Summary

• Both simulation results and test results show the frame dose not collapse and no wire fractures after removal of first floor center column.

• Simulation results and test results indicate the same location of first wire fracture which is close to steel cutting region in second floor middle bay beams.

• No shear failure (joint shear failure or beam shear failure) is observed.

• Simulation responses give a good prediction for the tested frame although minor disparity exists.

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