Research on the Fatigue Performance of Hinge-Type Seismic Connectors for Seismic Bracing Supports in Buildings

Seismic bracing systems are securely connected to the main building structure and are a very common type of building mechanical and electrical equipment. In addition to providing support and fixation， they also offer essential protection to pipelines and equipment during earthquakes， helping to mitigate secondary disasters caused by seismic events. However， due to their relatively short history of large-scale application， research on their mechanical properties and structural behavior remains limited， and the underlying mechanisms have not yet been fully understood. As a critical component of seismic bracing systems， hinge-type seismic connectors are subjected to concentrated forces during use and are prone to damage under alternating loads. Given the unique stress characteristics of hinge-type seismic connectors， studying their mechanical performance—particularly their fatigue performance—holds significant practical importance. Based on tensile bearing capacity specimens of hinge-type seismic connectors with identical materials and dimensional specifications， this study employed mathematical statistical methods to determine the tensile capacity values under corresponding confidence conditions. According to the statistical results of tensile capacity， the stress levels for the fatigue test were determined using the up-and-down method， which yielded the median fatigue limit stress of the hinge-type seismic connectors. For fatigue life evaluation， the group method was applied to measure performance at different stress levels. The S-N curve was then established by integrating the relevant data points obtained from both the up-and-down method and the group method. A detailed analysis of the tensile capacity test results revealed that due to the notched structure of seismic connector part 2， stress concentration readily occurred during loading， leading to crack initiation and rapid propagation， ultimately resulting in component failure. In the ultimate load-bearing tests： at a 0.9 confidence level， the failure load confidence interval was 31571 N to 39480 N； at a 0.95 confidence level， the corresponding interval ranged from 30718 N to 40333 N. The S-N curve analysis indicated a median fatigue strength of 19.56 MPa at one million cycles. This study concluded that when the applied force on seismic connectors remains below 2900 N during design or installation， the entire seismic bracing system maintains a high safety margin.