Cyclic Behavior of Steel Frame Joints in the Offshore Atmospheric Environment

The natural deterioration of mild steel elements exposed to offshore atmospheric environments compromises the long-term safety of existing steel buildings. An experimental study was conducted to investigate the effect of the offshore atmospheric environment on the seismic performance of steel frame joints. An indoor accelerated corrosion test was conducted to simulate the degradation of the mechanical properties of the materials and steel frame joints in the offshore atmospheric environment. After determining the corrosion rate by weighing after rust removal, the yield strength, ultimate strength, modulus of elasticity, and elongation of three test specimen with different thicknesses were obtained by regression of the tensile failure test, which demonstrated a linear decay relationship with the corrosion rate. Under four different corrosion degrees and three different low-cycle reciprocating loads, the failure modes of 12 steel frame joints were all plate-tearing at welded through holes. However, the difference is that the joints had ductile failure under equal-amplitude 90 mm loading and brittle failure under variable-amplitude loading. The effects of corrosion on the hysteresis behavior, deformation degradation, strength degradation, and energy dissipation capacity of steel frame joints were analyzed. The test results indicate that corrosion has significant effects on the seismic performance of steel frame joints. With the increase in corrosion degree, the energy dissipation capacity of steel frame joints declines more significantly than other performance indicators, and the yield platform of the steel frame joints is not evident.