The Application of Combination of Individual Modal Responses According to the Revised RG1.92

The U.S. Nuclear Regulatory Commission (NRC) issued the revised regulatory guide 1.92 as Rev. 2 on July 2006, which is believed to efficiently reduce the unnecessary conservative which is introduced by combination methods specified in RG1.92 Rev.1 and to be acceptable for combining modal responses and spatial components in seismic response analysis of nuclear power plant structures, systems, and components (SSCs). But it is still impossible to use this method to do the combination of spectrum response analysis, because most popular general finite element programs do not develop a reasonable command or macros according to RG1.92 Rev.2. In order to perform the combination of individual modal responses according to this new guide conveniently, this paper developed a macro file used the ANSYS Parametric Design Language (APDL) based on ANSYS program which is widely used in nuclear industry. This paper examined the macro file with an actual support pipe, and compared the results got from the new method with the results acquired from previously accepted method such as double sum method and grouped method. The comparison result shows that the revised combination method actually reduced the unnecessary conservative previously accepted by method in RG1.92, Rev.1, also the results prove that the macro file this paper established is reasonable.