modeling progressive collapse by plastic analysis andrew coughlinashutosh srivastavagraduate...
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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 Analysis
XTRACTTM
Nonlinear Pushover Analysis
CAPPTM
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.
Model
1. 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 6
2
1
3
4 4
55
Load Displacement Prediction of 1/8 Scale Model
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 0.5 1 1.5 2 2.5 3 3.5 4
Vertical Deflection (in)
Vert
ical
Loa
d (lb
s)
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
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 0.5 1 1.5 2 2.5 3 3.5 4
Vertical Deflection (in)
Vert
ical
Loa
d (lb
s)
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…”