Classification of Failure Modes in Tee Pipe Joints Under Seismic Loads by Literature Survey

Abstract It is well known that the failure mode of piping systems subjected to excessive seismic input would be a fatigue-ratcheting failure at pipe fittings, such as elbow or tees. However, the exact crack location on tee has not been well understood. To enhance the understanding of failure locations of tee pipe joints, a literature survey of experiments on tee was conducted. As a result of the literature survey, 36 types of failure results were extracted from ten references for pipe component tests. Of the 36 specimens, 30 were equal tees, and six were reducing tees. Regarding piping system tests, two types of results were extracted from two references. Various patterns of crack locations were confirmed in these experiments. By reviewing the results of previous studies, it appears that the failure location can primarily be classified based on the loading direction, namely, in-plane bending or out-of-plane bending. Based on the analysis of the collected information, the crack locations were summarized in a chart. The chart shows where a crack would penetrate in the tee pipe joint depending on the loading direction and some other conditions. Although some uncertainties remain regarding the exact crack initiation points, this study provides a better perspective on understanding the failure locations of tee pipe joints.