Abstract: This study focuses on how the interaction between piping and the supporting pipe-ways can affect the seismic behavior of the whole system. For this purpose, the considered pipe-way structures have been assumed to support multiple pipes so that the weight of the piping can be either about 25% of the pipe-way structure, or in some cases more and some cases less than that amount to evaluate how the ASCE code recommendation for analyzing the combination structures, such as piping and pipe-way, separately or as a whole system is valid. The effects of various combinations of different dimensions pipes, pipes end-conditions and stiffness of connecting links of on pipe-way piping on the system responses have been also discussed. Analytical results show that not only the weight percentage of piping, but also the stiffness of connection links and the dimensions of supported pipes and their end-conditions are also important factors affecting the whole system behavior and may cause the system conditions to be different from the code assumptions.