Seismic Design Margin of the Piping and Support System: Part 1—Static Loading Test of the Support

Abstract

On the evaluation of seismic design margin of the piping and support system in the nuclear power plant, the elasto-plastic behavior of support has played the important role in the seismic response analysis. It is desirable to establish the simple and effective non-linear modeling of the support in order to conduct the seismic response analysis considering each elasto-plastic characteristics of actual numerous supports in the piping system. On this point, this research project takes as its objectives to establish the simplified non-linear modeling of the support, in which the load-displacement characteristics are equivalent to the static loading test, in order to evaluate the seismic design margin. Static loading test of the support was designed to obtain the relationship between force and displacement characteristic at piping. The pipe support consists of a combination of a U-bolt, supporting elements such as a structural frame or a vibration actuator, a base plate and a concrete anchorage. Simulated seismic displacements were loaded into the piping to determine the failure mode and the limit load of support. The following were obtained as the static loading test. • The strength ratio of each test case is about 2.8 to 4.2, it turns out that limit load capacity of the support is much higher than the design allowable load. • The ductility ratio of the frame type support is higher than that of the oblique member type support. • Moreover, these test results are concurred well with the support failure modes of previous paper. Strength ratio = Tested failure capacity / Design allowable load. Ductility ratio = The displacement at the maximum load / The displacement at the start of yielding.