Seismic Performance of Degraded Shear Walls for Long-Term Compliance Periods
Luis Ibarra*, Biswajit Dasgupta**, and Kuang-Tsan Chiang**
*University of Utah, Department of Civil Engineering, 110 Central Campus Drive. Salt Lake City, UT 84112, USA
**Center for Nuclear Waste Regulatory Analyses, Southwest Research Institute®, 6220 Culebra Road, San Antonio, TX 78238, USA
Seismic performance evaluations of nuclear facilities are usually based on seismic probabilistic risk analyses that do not include the effects of concrete aging, which may decrease the capacity of reinforced concrete (RC) components with time. This study relates the physical mechanisms that take place during aging of concrete (e.g., cracking, and rebar corrosion) and the deterioration of mechanical properties that affect the system capacity under seismic events. The seismic performance evaluation uses available experimental data of steel reinforcement corrosion and variability of concrete parameters as a function of time. To obtain the variation in the system capacity caused by concrete aging, detailed numerical models of RC components and models of the selected structural systems are developed. The probability of unacceptable performance, or seismic failure, is computed by convolving the fragility data and selected hazard curves. The calculation includes the gain of concrete compressive strength with time. However, this gain in strength does not overcome the degradation of seismic performance caused by concrete cracking and corrosion of steel rebars. The results indicate that aging effects on RC components are largely influenced by seismic hazard at the site.
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