Dynamic response of piping system on rack structure with gaps and frictions

In the seismic design of a piping system on a rack structure, the interaction between the piping system and the rack structure must be evaluated under the condition that the rack structure is not stiff and heavy enough compared with the piping system. Moreover, there are local nonlinearities due to the gap and friction between the piping system and the rack structure. This paper presents the influence of the interaction and the local nonlinearities upon the seismic response by numerical study and a vibration test using a shaking table. In the numerical study, the piping system and the rack structure were represented by the three degrees of freedom mass-spring model taking a vibration mode of the piping system into account. The nonlinearities due to gap and friction were defined as a function of motion and treated as the pseudo force vector (additional applied force) in an equation of motion. From the results of the numerical study and the vibration test, it was clarified that seismic response of both the rack structure and the piping system is reduced by gap and friction. Moreover, the piping system and rack structure can be represented by the three degrees of freedom mass spring model. And the local nonlinearities can be treated by the pseudo force in an equation of motion.