seismic fragility of 3-span rc-slab overpass bridges...
TRANSCRIPT
Seismic Fragility of 3-span RC-slab Overpass Bridges According to Pushover and Response Spectra Analysis
Marian RALBOVSKY1, Alois VORWAGNER2, Maciej KWAPISZ3
1 AIT Austrian Institute of Technology GmbH, Vienna, [email protected]
2 AIT Austrian Institute of Technology GmbH, Vienna, Austria3 AIT Austrian Institute of Technology GmbH, Vienna, Austria
Paper ID: 10984
Problem statement
Paper ID: 10984
• Three-span RC-slab is very common structural type as highway overpass
• Highway operator needs network-wide indication of potential seismic vulnerability of bridges
• Simple analysis methods, engineering approach
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Parametric model
Paper ID: 10984
• 12 independent probabilistic parameters describe the bridge (geometry, reinforcement, soil)
• Ca. 20.000 parameter combinations (bridges) generated via Latin Hypercube Sampling
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Analysis methods
Paper ID: 10984
Linear response spectra
• 3D-Beam model• Linear soil springs• Multi-modal
,
,
,
,1
· , ·,
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Pushover analysis
• 2D-Beam model• Fibre-cross section• Single-mode (N2 method)
,0.3
,1
, ·,
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Results: whole bridge population
Paper ID: 10984
• Ground acceleration , at full utilization of limit states evaluated
• Response Spectra Analysis (RSA)• Single-mode Pushover Analysis (SPA)
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RSA ‐ bending
SPA ‐ bending
RSA vs. SPA
Paper ID: 10984
• SPA consistently less conservative in bending/rotation limit state• SPA predominantly less conservative in shear limit state
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Failure probability
Paper ID: 10984 7
Bending Whole bridge population Shear
ρ=1.0~1.5% Bending ρ=4.0~4.5%
Approximation formulas
Paper ID: 10984
• Empirical formula with coefficients fitted onto simulation results
•
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Conclusions
Paper ID: 10984
• In this analysis of 3-span RC slab bridges using simple beam models:• Bending / rotation limit state: pushover allowed always greater seismic
actions than RSA, especially at structures with low ρ• Shear limit state: pushover allowed greater seismic actions than RSA in
most cases
• Approximation formulas for estimation of PGA at full utilization of bending / rotation limit state had good accuracy for seismic actions relevant in Austria (PGA < 1,5 m/s²)
• Approximation formulas for estimation of PGA at full utilization of shear limit state showed low accuracy
• The results provided the highway operator a simple tool to identify potentially vulnerable structures in traffic network
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