Seismic response evaluation of medical gas and fire-protection pipelines’ Tee-Joints

The seismic vulnerability of non-structural components has become an issue of paramount interest in the field of earthquake engineering, as demonstrated by the increasing number of studies which started to deal with the item. As reported by different authors, the economic losses related to the failure of non-structural components are by far the highest rate of the total loss in a building. Furthermore, in most of the cases, the collapse of these elements significantly affects the operation of the building and can play a key role for the life safety too. Piping systems have been widely analysed in previous studies because of their high vulnerability to seismic actions as well as their importance in the immediate post-seismic emergency. A comprehensive analysis of the seismic behaviour of the main components characterizing a piping system layout is fundamental to understand the influence of the mechanical properties as well as the geometrical configuration of the single component on the seismic behaviour, since the wide range of materials adopted leads to a high variability of the response and the studies conducted so far do not cover all the possible configurations. In a life-safety view, medical gas and fire-protection piping systems are supposed to be the categories which require a special attention, since their functionality is often fundamental even in case of earthquake. The seismic behaviour of fire- protection and medical gas piping systems is analysed in the present work through experimental tests on T-joint connections, which are the most vulnerable components in case of earthquake. Quasi-Static cyclic tests were performed to define the hysteretic response of cast-iron and copper joints, in terms of Force-displacement and Moment-rotation behaviour. To the best of the author's knowledge no studies have been conducted yet on copper joints, while the results obtained from the tests on steel joints were compared with results available in literature. Furthermore, the influence of the fitting on the response in case of threaded connection was investigated. The results obtained have been adopted to calibrate simplified numerical models aimed at simulating the cyclic response of the components analysed. The proposed models would be useful in numerical analyses for the vulnerability assessment of piping systems layouts.