2002 PEER Annual Meeting P P E E E E R R Seismic Performance Modeling of Reinforced Concrete Bridges Stephen Mahin Byron and Elvira Nishkian Professor of Structural Engineering Mahmoud Hachem, Brian Buckman and Colin Cook Graduate Student Reseachers University of California at Berkeley
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PEER 2002 PEER Annual Meeting Seismic Performance Modeling of Reinforced Concrete Bridges Stephen Mahin Byron and Elvira Nishkian Professor of Structural.
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2002 PEER Annual Meeting
PPEEEERR Seismic Performance Modeling
of Reinforced Concrete Bridges
Stephen MahinByron and Elvira Nishkian Professor of Structural Engineering
Mahmoud Hachem, Brian Buckman and Colin Cook Graduate Student Reseachers
University of California at Berkeley
2002 PEER Annual Meeting
PEER Bridge Program
Focus on:• Monolithic reinforced
concrete bridge construction
• New rather than older construction detailing
• Representative of:– Viaducts
– Overcrossings
– Major interchanges
2002 PEER Annual Meeting
Many Elements Involved
• Approaches• Abutments• Foundations• Movement Joints• Columns/Piers• Superstructure• Nonstructural Features
Objectives:• Data to validate analytical models• Compare performance for near-fault
and long-duration excitations• Assess effects of multiple components
of ground motion• Assess cumulative damage models• Effect of cross-sectional geometry
•Circular sections with spirals•Noncircular with interlocking spirals
2002 PEER Annual Meeting
Column Performance
After Design Level Event (R=4) After First Maximum Level Event (=6)
2002 PEER Annual Meeting
Condition at end of tests
Fractured Spiral Fractured Bar
Buckled Bars
After sixth repetition of Maximum Run - Olive View
2002 PEER Annual Meeting
Long Duration Excitations
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1985 Llolleo, Chile Record
2002 PEER Annual Meeting
Peak Displacement Response
Maximum Bottom and Top Disp. in Long and Lat directions, Test A2
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A2-Run1Yield
A2-Run2Design 1
A2-Run3Max 1
A2-Run4Design 2
A2-Run5Max 2
A2-Run6Max 3
A2-Run7Design 3
A2-Run8Max 4
A2-Run9Max 5
A2-Run10Max6
Displacement [in]
Long. Column Disp Lat. Column Disp Long. Peak Ground Disp Lat. Peak Ground Disp
First Bar
Buckling
Bar
Fracture
Bi-directional input has limited effect and in the cases considered extends life of column
2002 PEER Annual Meeting
Bi-directional Response
- 8 - 6 - 4 - 2 0 2
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- 5
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- 3
- 2
- 1
0
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2
Δl a t
( i n )
Δ
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g
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Dis
pla
cem
ent
, in
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Displacement, in.
Ground motion characteristics have a large effect on:
• Nature of bi-directional response• Sensitivity of maximum
displacements to intensity• Residual displacements
Currently design criteria, for ideal conditions and without significant P-Δ effects or eccentric gravity loads, result in well-performing columns with significant reserve capacity
• Analytical models involve significant levels of judgement to get adequate prediction of performance
• Nearly all models with reasonable stiffness estimates can predict max. displacements– Small diameter, low aspect ratio (low periods), high loads, P-Δ
effects and gravity load eccentricities potential problems – Fiber models provide best fidelity, but need further assessment
and refinement
• Residual displacements and local deformations (spalling, bar buckling, steel fracture, etc.) sensitive to modeling
2002 PEER Annual Meeting
Summary
• Parametric and fragility analyses provide useful basis for understanding behavior, but integration into overall PEER assessment methodology essential
• Additional shaking table tests will be carried out along with analytical studies to:– get data on more complex bridge systems requiring
significant redistribution of load once yielding occurs