Piping systems are crucial components in both industry and society. Earthquakes can damage these systems through low-cycle fatigue or excessive displacement caused by large cyclic loads. Such damage can lead to gas and water leaks, resulting in fires, explosions, and flooding. Therefore, piping systems must be designed to withstand earthquakes, necessitating the use of seismic separation joints or devices. One effective countermeasure against earthquakes is the bellows expansion joint, which is a type of seismic separation joint. In this study, a 3-ply bellow expansion joint was developed to respond to earthquakes. The displacement-load curve was assessed using compression-tensile and bending cyclic loading tests to evaluate the seismic performance and limit state of the developed 3-ply bellows expansion joint. In the compression-tensile cyclic load test, leakage occurred at a displacement of 57.680 mm after 33 repetitions. In the cyclic bending load test, leakage was observed at a displacement of 132.070 mm after 36 repetitions. Additionally, a simplified numerical model for the 3-ply bellow expansion joints was constructed based on the experimental result. The model coincides well with the cyclic loading test results of the 3-ply bellows expansion joint, achieving fitness values of 85.29% for compression–tensile loading and 79.02% for bending. Consequently, the numerical model can be effectively used to understand and design the behavior characteristics of 3-ply bellows expansion joints.
