Fragility of Piping Systems and Reliability of Piping Components

Probabilistic frameworks are proposed to address the problem of evaluating seismic fragility for building-piping systems and the minimum reliability levels associated with piping design equation (9) in the ASME Boiler and Pressure Vessel Code, Section III, Division 1, NC/ND-3600 (ASME, 2007) in nuclear power plants. The main objective of the framework is to evaluate piping fragility in building-piping systems. To do so, a system level analytical piping model and a component level analytical model were developed based on experimental data. A methodology to reconcile experimental and analytical results for piping systems is presented. The damage to a piping system is characterized using the alternative form of the ASME criterion in terms of "First Leakage" as observed in laboratory tests. A nonlinear finite element model for the T-joint connection is formulated and validated with experimental results. Seismic fragility of a large-scale piping system in representative high-rise, mid-rise, and low-rise buildings is evaluated using nonlinear time history analyses. The emphasis is on evaluating the effects of piping interaction with building performance on piping fragility. The building models include the effects of building nonlinearity due to nonlinear behaviors of beams and columns which are characterized by a plastic hinge fiber model as well as a linear frame model. The main objective of the framework in the reliability-based design of piping systems is to evaluate the minimum reliability levels of the piping design equation. The design equation defined by the ASME B 2 equation or the modified B2 equation is calibrated using the Advanced First Order Reliability Method (AFORM) and Monte Carlo simulation for straight pipes and piping elbows.