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This paper investigated the progressive collapse resistance of exterior reinforced concrete frames under middle column removal scenarios. Five half-scale exterior frames comprising of a double-span beam, a middle beam-column joint and two side columns were tested under a concentrated point load on the middle joint. Different joint links and reinforcement ratios in beams and column sizes were used in frames. The resistances, deformation capacities and failure modes of frames were experimentally obtained. Test results showed that catenary action in bridging beams resulted in flexural failure of side columns, and thus the load capacity of frames depended highly on the moment capacity of column sections. A simplified method was also proposed based on the moment capacity of column sections and the axial force-bending moment interaction diagram of beams. The axial tension force in beams and the associated catenary action capacity were calculated by using the proposed method. Comparisons with test data suggest that the simplified method could predict the load capacity and tension force in beams under catenary action with reasonably good accuracy.

In this paper, a damping isolation system is developed for vibration control of steel jacket offshore platform structures. At first, a damping isolation system composed of rubber bearings and viscous dampers is proposed for vibration mitigation of JZ20-2MUQ jacket platform located in Bohai Sea. The influence of key parameters of the damping isolation system on the vibration suppression of the offshore structure is studied in detail. In order to examine the vibration control effectiveness of the damping isolation system for the jacket platform, a comprehensive experimental and numerical study is carried out. The experimental investigation is conducted on a shaking table for a 1/10-scale JZ20-2MUQ platform model subjected to four different earthquake ground motions. The performance of the controlled structure under the actions of ice and seismic-induced forces is then studied by numerical simulations. The experimental results are found to be in good agreement with those from the numerical simulations. It is shown from the combined experimental and numerical study that the damping isolation system is effective in mitigating the dynamic responses of the offshore platform structure.