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DOE‐NRC NPH 2018
Numerical Modeling of Concrete Building Pounding During Seismic Events ‐ A Case Study
Asa Bassam, PhD, SE, PEBenjamin Kosbab, PhD
Payman Tehrani, PhD, PE
October 23, 2018
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Prepared for the DOE‐NRC Meeting on Natural Phenomena Hazards
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INTRODUCTION
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• Structural Damage– Local structural failure– Consequence of local failure– Global structural failure
• Non‐Structural Damage– High‐frequency spectral acceleration due to impact/pounding– Chatter‐sensitive components– Cosmetic or non‐load bearing failures.
Potential Consequence of Seismic Impact
Typically addressed by sizing the gaps to eliminate impact at SSE level earthquake altogether.
Jankowski, Engineering Structures, 2009
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Wolf and Skrikerud (Nuclear Engineering and Design 1980)
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Background
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Kasai, Jeng, & Maison (Earthquake Engineering 1992)
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Background
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Motivation
Reactor Building U1 U2 U3
Turbine Building
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Motivation
Reactor Buildings
slab‐to‐slab impact
slab‐to‐slab impact
slab‐to‐slab impact
slab‐to‐wall impact
Turbine Building
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METHODOLOGY
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Modeling of Impact
Modified (Hybrid) Contact Laws:
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Impact Stiffness
Goldsmith, W., (1960) Impact: the theory and physical behavior of colliding solids,
≅ 10 / .
Kawashima, K., and Penzien, J., EERC Report 76‐26, 1976
Contact stiffness approximated as the stiffness of impact neighboring FE elements
≅ 10 / .
van Mier, J. G. M., et al., ASCE Journal of Structural Engineering, 1991
≅ 10 / .
, , , ,
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Impact StiffnessImpact Stiffness
Impact Damping
Jankowski, R., Key Engineering Materials., 2005
Jankowski, R., Theoretical and Applied Mechanics, 2007
, , , ,
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MODELING DETAILS
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Detailed Modeling Strategy
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3D FEM
3D FEM LMSM
1D Impact elements
Five spectrally matched ground motions
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3D Finite Element Models
Reactor Building
Turbine Building Part 1
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RB
TB Part 1
TB Part 3
TB Part 2
TB Foundation Pile Springs
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Combined Finite Element Model
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Combined Finite Element Model
Location of impact elements at RB‐TB Part 1 at a typical elevation
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FE Model Including Soil
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• The soil medium explicitly modeled with solid finite elements.
• A hysteretic viscoelastic material model used for modeling both soil and structure to achieve nearly frequency independent viscoelastic behavior.
• Analyses were performed using the explicit time domain in LS‐DYNA
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INVESTIGATION OF IMPACT BEHAVIOR
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Impact Forces
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0.25 ≅
∆ 1.8 ≅
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Variation of Impact Forces with Impact Stiffness
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• No specific trend due to impact element stiffness. The impact force results vary by +20% depending on the choice of impact stiffness.
• The impact forces are highly dependent on the local building stiffness
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Selected Areas for ISRS Generation at RB EL 617’ and 621’ Slabs
Variation of ISRS with Impact Stiffness
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TB ISRS
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ISRS Results From SDOF Model
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RB TB
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CONCLUSION AND SUMMARY
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• The effect of building impact between two concrete structures with fairly different flexibilities was investigated in this studies.
• The effect of impact on the ISRS in the more flexible structure was found significant while it was found insignificant in the stiffer structure.
• The impact forces were highly dependent on the local structural stiffness of the impacting buildings but not very sensitive to the selection of the impact stiffness in the realistic range.
• The ISRS results from simplified SDOF model show consistent behavior with the detailed model.
Conclusion and Summary
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THANK YOU! QUESTIONS ?
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