# Validation of Seismic Performance of Stainless Press-to-Connect Piping System under Cyclic Loadings
## 6 Conclusions  
The piping system is an essential nonstructural component that provides or maintains sustainable energy distribution in critical/noncritical facilities. The joint system, reported as one of the most vulnerable parts during and after earthquakes, consists of various non-welding connections, such as threaded, grooved, and press-to-connect joint systems, in the piping system. This study focused on experimentally and analytically evaluating the seismic performance of an elbow joint and a large-scale piping system with a press-to-connect joint system, an O-ring seal, and a compressed seal for leak-free operating conditions. More specifically, based on an experimental test of the piping system, a high-fidelity FE model of the press-to-connect piping system was validated and verified. The conclusions corresponding to the seismic requirements and engineering demands of the piping system in this study are as follows:  
To evaluate the dynamic characteristics of the press-to-connect elbow system, an in-plane cyclic loading test was performed, and a force-displacement curve of the elbow system was obtained. Subsequently, a high-fidelity FE model of the elbow system was constructed using the ABAQUS platform [11]. However, because the O-ring seal and compressed seal for permanent leak-free press-to-connect were extremely complicated in the FE model, a simplified 3D elbow joint model using a spring element in the ABAQUS platform [11] was generated in this study. In comparison with the results of the experimental test and analytical model, the high-fidelity FE model was slightly more conservative than the data obtained from the test, which is attributed to errors by the springback phenomenon and Bauschinger effect of the constitutive material model on the press-to-connect elbow system. Consequently, notwithstanding the insignificant error, the press-to-connect elbow FE model developed in this study was reliable. Next, to understand the field application value and seismic performance of a large-scale piping system containing a press-to-connect elbow, T-joint, and flexible coupling associated with NFPA 13 [10], a cyclic loading test using a sinusoidal wave was applied to the large-scale piping system. The velocity and displacement for the tests were 20 mm/min and \(\pm\)60 mm, respectively. Regarding the elbow component level FE model, a high-fidelity simulation FE model of the large-scale piping system was constructed in this study using the ABAQUS platform [11]. The von Mises stress was relatively small at the lower and upper elbows of the large-scale piping FE model in comparison to the experimental test results. Despite this issue, the interference error was not considerable because it was less than 9%. In addition, the deformation angles at the lower and upper elbows were in good agreement with the experimental test results. The error and change in the stress and deformation in the high-fidelity simulation FE model may be caused by the effect of the slip and spring-back phenomenon in the piping system. However, because the interference error at the elbow and large-scale piping system applied to the press-to-connect type condition was relatively trivial, the application value of the large-scale piping FE model may be extremely high. In addition, the press-to-connect large-scale piping system may satisfy the condition of ASME B and PV section III [17] for service level D, both experimentally and numerically. Finally, this study explored the dynamic characteristics and seismic performance of the press-to-connect elbow and large-scale piping system under in-plane cyclic loading conditions, and the design requirements and engineering demands of the piping system were mostly satisfied.