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Modeling Progressive Collapse by Plastic Analysis
Andrew Coughlin Ashutosh SrivastavaGraduate Research Assistant Graduate Research AssistantThe Pennsylvania State University The Pennsylvania State University
Progressive Collapse Resistance Competition (PCRC)ASCE Structures CongressApril 25, 2008Vancouver, BC
Motivation
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Problem
Dynamic Testing
Static Testing
Approach
Cross Section Fiber AnalysisXTRACTTM
Nonlinear Pushover AnalysisCAPPTM
Screenshots from XTRACTTM and CAPPTM, a collaborative effort between Imbsen and Associates and Charles Chadwell, Ph.D., P.E.
Outline Assumptions
Cross Sectional Fiber Analysis
Nonlinear Pushover Analysis
Results
Discussion
Assumptions Similitude: 1/8 scale model
1/8th all lengths 1/64th all forces Same stress
Plastic hinge length d/2 Axial deflections not considered Fixed support conditions
Outline Assumptions
Cross Sectional Fiber Analysis
Nonlinear Pushover Analysis
Results
Discussion
Cross Sectional Fiber Analysis Material Models
Mander, J.B., Priestley, M. J. N., "Observed Stress-Strain Behavior of Confined Concrete", Journal of Structural Engineering, ASCE, Vol. 114, No. 8, August 1988, pp. 1827-1849
Cover Concrete Confined Concrete Reinforcing Steel
Cross Sectional Fiber Analysis
Beam at joint
Beam at cutoff
Column
Roof beam
Confined concrete
Reinforcing steel
Cover concrete
Screenshots from XTRACTTM, a collaborative effort between Imbsen and Associates and Charles Chadwell, Ph.D., P.E.
XTRACTTM
Moment Curvature
Screenshots from XTRACTTM, a collaborative effort between Imbsen and Associates and Charles Chadwell, Ph.D., P.E.
Outline Assumptions
Cross Sectional Fiber Analysis
Nonlinear Pushover Analysis
Results
Discussion
Nonlinear Springs
Screenshots from CAPPTM, a collaborative effort between Imbsen and Associates and Charles Chadwell, Ph.D., P.E.
Model1. Elastic Beam Elements2. Nonlinear Hinges
Where could they form?1. Joints2. Load points3. Section changes (due to bar cutoff)
Dynamic Test
Static Test
Plastic Hinge Formation
6 62
1
3
4 4
55
Load Displacement Prediction of 1/8 Scale Model
0200400600800
100012001400160018002000
0 0.5 1 1.5 2 2.5 3 3.5 4Vertical Deflection (in)
Verti
cal L
oad (
lbs)
Predicted Bar Fracture
Predicted Bar Fracture Location
Outline Assumptions
Cross Sectional Fiber Analysis
Nonlinear Pushover Analysis
Results
Discussion
Dynamic Results Structure did not collapse Max Deflection
Predicted = 0.96” Actual = 0.21”
Permanent Deflection Predicted = 0.87” Actual = 0.20”
Sources of Error Dynamic effects were not considered Large change in deflection for little change in
load Material overstrength
Static Results Maximum Load
Predicted = 1800 lb Actual = 1800 lb
(before catenary action) Displacement at bar fracture
Predicted = 3.9” Actual = 3.48”
Load Displacement Prediction of 1/8 Scale Model
0200400600800
100012001400160018002000
0 0.5 1 1.5 2 2.5 3 3.5 4Vertical Deflection (in)
Verti
cal L
oad (
lbs)
Actual
Predicted
Predicted Bar Fracture
Actual Bar Fracture
The rest of the story…
Catenary ActionPrediction Cutoff
Outline Assumptions
Cross Sectional Fiber Analysis
Nonlinear Pushover Analysis
Results
Discussion
Acknowledgements Yang Thao of Imbsen and Associates
Educational Software Licenses
Prof. Charles Chadwell, Cal Poly Modeling advice
Prof. Jeffrey Laman, Penn State Review of submission
Prof. Mehrdad Sasani, Northeastern Competition organization
Questions?
“And the structure stands…”
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