Reinforced Concrete Shear Wall Capacity Advances

Seismic PRAs have become more common in the nuclear power industry following the Fukushima accident caused by the 2011 earthquake and tsunami. In order to provide best estimates of the risk, the seismic fragilities should be as realistic as possible. Nuclear plant reinforced concrete (RC) structures have traditionally exhibited high seismic capacities within seismic probabilistic risk assessments (SPRAs). For the existing fleet of nuclear power plants (NPPs), RC walls and slabs were commonly constructed without out-of-plane (OOP) or transverse shear reinforcement. The capacity for these RC elements has typically been empirically derived based on code equations for the concrete shear strength of RC beams. Research of a broader set of beam shear test data is now showing that beams with little or no transverse reinforcing may not have the shear capacities predicted by current American Concrete Institute (ACI) codes. The Electric Power and Research Institute (EPRI) has begun a study to research the basis of these proposed reductions, and if appropriate, develop new equations to assess the OOP shear capacity of walls and slabs. The goal is to assess what a realistic median capacity and variability would be for use in fragility analyses and to consider how that updated fragility could affect SPRAs.

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