Modeling%20Progressive%20Collapse%20by%20Plastic%20Analysis

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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

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Motivation
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Problem
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Dynamic Testing
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Static Testing
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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.
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Outline

• Assumptions
• Cross Sectional Fiber Analysis
• Nonlinear Pushover Analysis
• Results
• Discussion

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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

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Outline

• Assumptions
• Cross Sectional Fiber Analysis
• Nonlinear Pushover Analysis
• Results
• Discussion

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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. 1827-1849
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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.
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Moment Curvature
Screenshots from XTRACTTM, a collaborative effort
between Imbsen and Associates and Charles
Chadwell, Ph.D., P.E.
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Outline

• Assumptions
• Cross Sectional Fiber Analysis
• Nonlinear Pushover Analysis
• Results
• Discussion

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

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

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Dynamic Test
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Static Test
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5
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Plastic Hinge Formation
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Predicted Bar Fracture
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Predicted Bar Fracture Location
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Outline

• Assumptions
• Cross Sectional Fiber Analysis
• Nonlinear Pushover Analysis
• Results
• Discussion

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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

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Static Results

• Maximum Load
• Predicted 1800 lb
• Actual 1800 lb
• (before catenary action)
• Displacement at bar fracture
• Predicted 3.9
• Actual 3.48

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Actual
Predicted
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Actual Bar Fracture
Predicted Bar Fracture
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The rest of the story
Catenary Action
Prediction Cutoff
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Outline

• Assumptions
• Cross Sectional Fiber Analysis
• Nonlinear Pushover Analysis
• Results
• Discussion

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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

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Questions?
And the structure stands