Parametric investigation on the response of suspended piping systems to tri-directional seismic excitation

The evaluation of the seismic performance of piping networks is often difficult due to several parameters involved in the process, such as complex geometry, modelling uncertainties and earthquake properties. Despite several studies have been conducted on this topic, driven by the importance of piping networks from a building serviceability standpoint, generalized guidelines to achieve defined performance criteria are still difficult to develop. The hardships in analysing the seismic response of piping networks are mainly due to their peculiar configuration, which leads to interaction between local vibration modes and the seismic acceleration. Additional issues are also caused by great variability in piping systems' design and quality. The scope of this study is to investigate several aspects of the dynamic response of different types of piping networks, considering tridirectional floor seismic input. A numerical model was developed, accounting for the non-linear behaviour of piping restraint installations and pipe joints. The numerical model was used to perform nonlinear time-history analyses aimed at assessing the seismic vulnerability in a performance-based design framework. The influence of the geometric configuration and the mass of the system was investigated by analysing the accelerations and displacements, alongside damage on pipe joints and suspended piping restraints due to earthquake. Additionally, the response obtained considering and neglecting the vertical component of the floor acceleration were compared. The results of the analysis were employed to compute fragility functions at different limit states, considering the parameters investigated. A clear influence of the geometry and the mass of the system on the seismic vulnerability is observed, while the effects of the vertical acceleration seem to be generally negligible.