Modeling Progressive Collapse by Plastic Analysis Andrew Coughlin
Modeling Progressive Collapse by Plastic Analysis Andrew Coughlin Graduate Research Assistant The Pennsylvania State University Ashutosh Srivastava Graduate Research Assistant The Pennsylvania State University Progressive Collapse Resistance Competition (PCRC) ASCE Structures Congress April 25, 2008 Vancouver, BC
Motivation Images are public domain distributed by wikipedia. org
Problem
Dynamic Testing
Static Testing
Approach Cross Section Fiber Analysis XTRACT TM Nonlinear Pushover Analysis CAPP TM Screenshots from XTRACT TM and CAPPTM, a collaborative effort between Imbsen and Associates and Charles Chadwell, Ph. D. , P. E.
Outline o Assumptions o Cross Sectional Fiber Analysis o Nonlinear Pushover Analysis o Results o Discussion
Assumptions o Similitude: 1/8 scale model n 1/8 th all lengths n 1/64 th all forces n Same stress o Plastic hinge length d/2 o Axial deflections not considered o Fixed support conditions
Outline o Assumptions o Cross Sectional Fiber Analysis o Nonlinear Pushover Analysis o Results o Discussion
Cross Sectional Fiber Analysis o Material Models Cover Concrete Confined Concrete 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 Reinforcing Steel
Cross Sectional Fiber Analysis Cover concrete Beam at joint Column Reinforcing steel Beam at cutoff Roof beam Confined concrete XTRACTTM Screenshots from XTRACT TM, a collaborative effort between Imbsen and Associates and Charles Chadwell, Ph. D. , P. E.
Moment Curvature Screenshots from XTRACT TM, a collaborative effort between Imbsen and Associates and Charles Chadwell, Ph. D. , P. E.
Outline o Assumptions o Cross Sectional Fiber Analysis o Nonlinear Pushover Analysis o Results o Discussion
Nonlinear Springs Screenshots from CAPP TM, a collaborative effort between Imbsen and Associates and Charles Chadwell, Ph. D. , P. E.
Model 1. Elastic Beam Elements 2. Nonlinear Hinges o Where could they form? 1. Joints 2. Load points 3. Section changes (due to bar cutoff)
Dynamic Test
Static Test
5 5 3 4 4 1 6 6 2 Plastic Hinge Formation
Predicted Bar Fracture
Predicted Bar Fracture Location
Outline o Assumptions o Cross Sectional Fiber Analysis o Nonlinear Pushover Analysis o Results o Discussion
Dynamic Results o Structure did not collapse o Max Deflection n Predicted = 0. 96” n Actual = 0. 21” o Permanent Deflection n Predicted = 0. 87” n Actual = 0. 20” o Sources of Error n Dynamic effects were not considered n Large change in deflection for little change in load n Material overstrength
Static Results o Maximum Load n Predicted = 1800 lb n Actual = 1800 lb (before catenary action) o Displacement at bar fracture n Predicted = 3. 9” n Actual = 3. 48”
Actual Predicted
Actual Bar Fracture Predicted Bar Fracture
The rest of the story… Prediction Cutoff Catenary Action
Outline o Assumptions o Cross Sectional Fiber Analysis o Nonlinear Pushover Analysis o Results o Discussion
Acknowledgements o Yang Thao of Imbsen and Associates n Educational Software Licenses o Prof. Charles Chadwell, Cal Poly n Modeling advice o Prof. Jeffrey Laman, Penn State n Review of submission o Prof. Mehrdad Sasani, Northeastern n Competition organization
Questions? “And the structure stands…”
- Slides: 33