Application Study On Retrofitting Of Concrete Frame Structure

With the economic development and population growth in China,the land resource available for new buildings decreases significantly,which brings about an urgent demand for retrofitting of existing structures.Particularly,the adding-story design has been applied extensively in building retrofitting since it is a cost-effective approach to considerably increase the usable area and the functions of the buildings.Evidently,the loads carried by the structural elements are also increased in the adding-story design and may well exceed the original load-carrying capacities of the elements.Therefore,it is necessary to analyze the mechanical performance of the retrofitted buildings and to strengthen the critical structural members.However,there is a paucity of systematical research efforts on the inspection,evaluation,strengthening design and seismic performance analysis of the retrofitted structures with added stories.In this study,a practical retrofitting project of a reinforced concrete(RC)frame plant was conducted,the content and the method for the structure reliability assessment involved in retrofitting process was summarized,and the seismic performance of the structure before and after retrofitting was analyzed.The structural elements with insufficient bearing capacities were strengthened,and meanwhile,the effects of the second load on the element strengths were investigated using finite element method.Three different strengthening methods were compared in terms of the effects on structure mechanical performance and the economic efficiency,and the research results can provide the theoretical foundation and decision supports for strengthening structural components without meeting the design requirements on the bearing capacity.The main research contents are summarized as follows:(1)Survey and detect the engineering parameters of the actual structure,conduct the structure reliability assessment,and get the basic modeling data for retrofitting and strengthening.(2)Check the load-carrying capacities of the ground base and foundation,RC columns and beams of the structure,build up the finite element model and analyze the seismic performance of the structure,and check the vibration mode,period,lateral stiffness ratio,inter-story drift ratios,stiffness-weight ratio and shear-weight ratio.(3)Propose three strengthening schemes and analyze the seismic performance of retrofitted structures based on ABAQUS platform,summarize the merits and disadvances of different strengthening schemes and provide decision supports for similar retrofitting projects in the future.