An Experimental Study on Seismic Performance Evaluation of Multi-Ply Bellows Type Expansion Joint for Piping Systems

Piping systems are a representative social infrastructure to provide oil, gas, and water. Damage to piping systems may cause serious consequences, such as fire, water outage, and environmental pollution. Therefore, piping systems need to be protected from natural disasters, such as earthquakes. Earthquakes may cause deformation that exceeds piping design criteria. For example, large relative displacements and liquefaction of the ground resulting in loss of strength and ground subsidence, and the side-sway of primary structures subjected to a strong ground motion may cause critical damage to piping systems. Therefore, expansion joints to maintain flexibility can be applied to locations where excessive deformation is expected to improve the seismic performance of piping systems. Metal bellows, a type of expansion joints, are flexible, so they are highly durable against deformation and fatigue loads. This indicates that metal bellows can be used as seismic separation joints for piping. In this study, experimental research was conducted to analyze the seismic performance of multi-ply bellows type expansion joints, a type of metal bellows. Monotonic loading tests and cyclic loading tests were conducted on 2-ply bellows and 3-ply bellows, and the results were compared. In the cyclic loading tests, multi-step increasing amplitude cyclic loading, which used the displacement history amplified in stages, and constant amplitude cycling loading with various magnitudes were considered. The test results showed no significant difference in bending performance for monotonic loading between the two types of multi-ply bellows. The 3-ply bellows, however, showed higher performance for low-cycle fatigue than 2-ply bellows.