Abstract
The pipes with diameter of 150mm, also called DN150, are often connected by grooved fit joints and employed as the stem pipelines, which are used to transport water vertically to different building stories and distribute it horizontally to different rooms. A large deformability is often required for the grooved fit joints to accommodate the deformation concentrated between adjacent stories during an earthquake. To this end, the grooved fit joint is often improved with a wider groove to achieve such a large deformability. However, its seismic performance has not been thoroughly studied yet. This study conducted quasi-static tests on twelve DN150 grooved fit joints, including four elbow joints and eight DN150-DN80 Tee joints. The mechanical behavior, rotational capacity and failure mode were examined and discussed. The test results indicate that the fracture of the grooved fitting and the pull-out of pipes from the grooved fitting are the major damage patterns at deformations larger than 0.1rad. At small deformations less than 0.06 rad, although slight abrasion and wear were observed on the contact surface between the galvanized steel pipe and the grooved fitting, they would not result in significant leakage. Three damage states are defined accordingly and the fragility models are developed for different grooved fit joints based on test results. Finally, seismic fragility analysis of DN150 stem pipeline system in a 10-story building was conducted. It is demonstrated that the improved joints survive under the maximum credible earthquake and the leakage is highly unlikely to occur.
Highlights
Recent earthquakes have demonstrated that the non-structural components of critical facilities such as power plants, hospitals, and industrial units suffered much more damage in comparison with structural components, which mitigated the functionality of these critical facilities (Filiatrault and Sullivan, 2014; Dhakal et al, 2016)
Slight wear at interface between pipes and joint can be observed at DN150 pipes and heavy wear can be observed at DN80 pipes but the wear didn’t cause any leakage and did no harm to the functionality of the pipes, which implies a good sealing performance of the improved joint
DS1 represents the case in which pressure in the pipe drops to 85%, DS2 represents massive leakage when the water pressure drops to 0 MPa, and DS3 represents complete damage of the joints, including the resistance force dropping to 85% of the peak force, visible cracks, and the pipe pull-out
Summary
Recent earthquakes have demonstrated that the non-structural components of critical facilities such as power plants, hospitals, and industrial units suffered much more damage in comparison with structural components, which mitigated the functionality of these critical facilities (Filiatrault and Sullivan, 2014; Dhakal et al, 2016). The piping system was reported to be one of the most vulnerable non-structural systems in past earthquake disasters. Leakage of fire sprinkler piping systems forced the temporary evacuation of several hospital buildings after the earthquake (OSHPD, 1995; Ayres and Ezer, 1996). Most losses were caused by damages to non-structural components such as suspended ceilings, light fixtures, and fire sprinkler piping systems. The two largest airports in Chile were closed as well because of non-structural damages and flooding from failed sprinkler piping systems (Ju, 2011; Miranda et al, 2012; Tian et al, 2014). It was reported that 42% of the piping systems with damaged components exhibited water leakage during this earthquake which caused great inconvenience to earthquake rescue efforts (Mizutani et al, 2012; Soroushian et al, 2015a)
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