A research program on thinned wall piping systems under seismic events

An experimental and analytical research program on piping systems with wall thinning has been conducted to clarify the effect of degradation on the dynamic behavior and the failure mode of the piping system. The degradation conditions considered in the program was wall thinning. From the results of cyclic bending tests on the pipe elements and the shake table tests on the simply-designed piping system models with wall thinning, it is shown that the failure mode of the degraded piping system is mainly fatigue failure with ratchet deformation. Finite element method (FEM) analyses were also conducted to reproduce the experimental results. The analytical results show that the failure mode and the lives of the thinned wall pipes subjected to cyclic load would be estimated reasonably based on the analyses. The experimental results show that the effect of wall thinning on the dynamic characteristics and the failure mode of piping system should be clarified quantitatively to estimate the seismic safety of the thinned wall piping systems through the experimental and analytical survey. (authors)