Low‐Cycle Fatigue Performance of Steel Beam with Weld Access Holes Under Small‐Amplitude Cyclic Loading

The potential for low‐cycle fatigue damage in steel beams of tall steel buildings subjected to long‐duration ground motions has been a significant concern in structural engineering. Previous research has primarily evaluated the low‐cycle fatigue performance of steel beams through cyclic loading tests, focusing on the amplitude–life relationship for various parameters, such as beam geometry and connection details, predominantly under large‐deformation amplitudes. However, studies addressing smaller amplitude ranges—particularly those encompassing both elastic and slightly plastic regimes—remain limited. The scarcity of experimental data and variability in beam parameters across existing studies have hindered the development of a unified low‐cycle fatigue assessment method that spans both elastic and plastic ranges. In this study, cyclic loading tests with small, constant deformation amplitudes were conducted on four full–scale steel cantilever beam specimens featuring weld access holes. The primary test variable was the loading amplitude, corresponding to deformation within the elastic and slightly plastic ranges, to address the current gap in available data. The low‐cycle fatigue performance of steel beams with weld access holes was evaluated across both elastic and plastic regimes, and a comprehensive amplitude–life relationship encompassing these ranges was established. This relationship provides valuable insights for the seismic design assessment of structures exposed to long–duration ground motions, where small amplitude and long‐duration cyclic demands are crucial.