Experimental Seismic Fragility of Pressurized Fire Suppression Sprinkler Piping Joints

Pressurized fire suppression sprinkler piping is a critical nonstructural system that must remain operational after an earthquake, particularly in critical facilities. Observations from past earthquakes have demonstrated that the locations most susceptible to damage in sprinkler piping systems are the joints, sprinkler heads, support hangers, and bracing systems. However, field observations and previous experimentations are insufficient to fully characterize the response of sprinkler piping systems under seismic actions and to develop effective solutions to improve their performance. This paper presents the results of an experimental program designed to evaluate the seismic behavior of sprinkler piping joints. Forty‐eight tee joints made of various materials (black iron with threaded joints, thermoplastic (CPVC) with cement joints, and steel with groove‐fit connections) and nominal diameters (¾ in. to 6 in.) were tested under reverse cyclic loading to determine their rotational capacities at which leakage and/or fracture occur. The ATC‐58 framework is applied to develop a seismic fragility database for pressurized fire suppression sprinkler joints considering joint rotation as the demand parameter. Fragility functions in terms of more global demand parameters, such as floor accelerations, can be developed using data presented here combined with structural analysis models of sprinkler piping systems.