1. Modeling Progressive Collapse by Plastic Analysis
Andrew Coughlin Ashutosh Srivastava
Graduate Research Assistant Graduate Research Assistant
The Pennsylvania State University The Pennsylvania State University
Progressive Collapse Resistance Competition (PCRC)
ASCE Structures Congress
April 25, 2008
Vancouver, BC

2. Images are public domain distributed by wikipedia.org
Motivation
Images are public domain distributed by wikipedia.org

3. Problem

5. Dynamic Testing

6. Static Testing

7. 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.

8. Outline Assumptions Cross Sectional Fiber Analysis
Nonlinear Pushover Analysis
Results
Discussion

9. Assumptions Similitude: 1/8 scale model Plastic hinge length d/2
1/8th all lengths
1/64th all forces
Same stress
Plastic hinge length d/2
Axial deflections not considered
Fixed support conditions

10. Outline Assumptions Cross Sectional Fiber Analysis
Nonlinear Pushover Analysis
Results
Discussion

11. Cross Sectional Fiber Analysis
Material Models
Cover Concrete
Confined Concrete
Reinforcing Steel
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

12. Cross Sectional Fiber Analysis
Cover concrete
Beam at joint
Column
Reinforcing steel
Beam at cutoff
Roof beam
Confined concrete
XTRACTTM
Screenshots from XTRACTTM, a collaborative effort between Imbsen and Associates and Charles Chadwell, Ph.D., P.E.

13. Moment Curvature
Screenshots from XTRACTTM, a collaborative effort between Imbsen and Associates and Charles Chadwell, Ph.D., P.E.

14. Outline Assumptions Cross Sectional Fiber Analysis
Nonlinear Pushover Analysis
Results
Discussion

15. Nonlinear Springs
Screenshots from CAPPTM, a collaborative effort between Imbsen and Associates and Charles Chadwell, Ph.D., P.E.

16. Model Elastic Beam Elements Nonlinear Hinges Where could they form?
Joints
Load points
Section changes (due to bar cutoff)

18. Dynamic Test

20. Static Test

21. Plastic Hinge Formation5 5 3 4 4 1 6 6 2
Plastic Hinge Formation

22. Predicted Bar Fracture

23. Predicted Bar Fracture Location

24. Outline Assumptions Cross Sectional Fiber Analysis
Nonlinear Pushover Analysis
Results
Discussion

25. 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

26. Static Results Maximum Load Displacement at bar fracture
Predicted = 1800 lb
Actual = 1800 lb
(before catenary action)
Displacement at bar fracture
Predicted = 3.9”
Actual = 3.48”

27. Actual
Predicted

28. Predicted Bar Fracture
Actual
Bar Fracture
Predicted Bar Fracture

29. The rest of the story…
Catenary Action
Prediction Cutoff

30. Outline Assumptions Cross Sectional Fiber Analysis
Nonlinear Pushover Analysis
Results
Discussion

32. 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

33. “And the structure stands…”
Questions?
“And the structure stands…”