Study on analogy between dynamic load and displacement-controlled load

Difficulties in handling dynamic load with elastic–plastic analysis and/or structural component test significantly exist in the field of R&D for seismic resistive nuclear pipe systems. In previous studies, the analyses and the structural tests were conducted statically. Many of them have been suggesting conservativeness included in the current seismic criterion of the nuclear design code. Therefore, if analogy between the earthquake load and static displacement are proved, it should bring possibility of more reasonable criterion. The author studied analogy between dynamic load and static displacement using FEM analysis with elastic beam model and elastic–plastic shell model of an elbow. First, the dynamic load equivalent to 160% of ASME/JSME Code’s Level D limit was defined using the elastic beam model. Next, the defined dynamic load was given to the elastic–plastic shell model to acquire the non-linear behaviors such as the relative displacement trend and the plastic strain accumulation at crown of the elbow. Then, three cases of cyclic displacement trends, Case 1, 2 and 3, were defined base on the dynamic analysis results and given to the elastic–plastic shell model statically. Comparison between the dynamic analysis and the static analysis of Case 1 showed clear analogy between the dynamic load and the static displacement. Case 2, however, was found to be difficult to be judged at this moment. Case 3 was conservative throughout the loaded time and suggested possibility of the conservative displacement trend for static structural test without conducting the elastic–plastic analysis.