EXPERIMENTAL AND RESTORING FORCE MODEL RESEARCH ON THE SEISMIC BEHAVIOR OF CORRODED STEEL FRAME BEAMS IN OFFSHORE ATMOSPHERIC ENVIRONMENT

To study the seismic behavior of corroded steel frame beams in offshore atmosphere environment, accelerated corrosion test of offshore atmosphere environment and low cyclic loading test on 5 steel frame beams were implemented. The effects of corrosion degrees on the failure mode, strength, deformation capacity and energy-dissipating capacity of the samples were analyzed. The test results show that as the corrosion degree increases, the lateral displacements corresponding to flange buckling, web buckling and plastic hinge formation at the beam-bottom reduced gradually; the load bearing capacity and ductility decrease significantly; the strength and stiffness degenerate obviously and the energy dissipation capacity degrades. On this basis, a restoring force model of corroded steel frame beams was established by introducing the cycle degradation indices, which can reflect the mechanical properties such as strength attenuation and stiffness degradation. The calculation results of hysteretic curves are consistent with the test results, which verifies the applicability of the proposed model. This study may provide experimental and theoretic basis for anti-seismic evaluation of existing steel structures in offshore atmospheric environment.