Performance Based Strengthening Reconstruction And Optimum Study For Existing Masonry Structures

Chinese construction industry has entered a development of period paying equal attention to both newly-built structures and existing structures. Especially after the Wenchuan earthquake, a large number of old masonry buildings which do not meet current seismic fortification criterion are urgently needed to be strengthened and reconstructed. Meanwhile, the academic research on the seismic design of buildings has targeted the performance-based seismic design and there still exists an initial stage about using performance-based seismic design concept to study strengthening reconstruction of existing houses in China . Therefore, the problem of performance-based of existing masonry structures reinforcement and structural optimization is worth studying further.In this paper, the main administration building of Dalian university of technology is considered as the basic object of the research. On a basis of assessing the reliability of the targeted masonry structure and the seismic performance evaluation and using performance-based seismic design concept, the beneficial effects about isolation reinforcement measures to upgrade the level of the main building's and it's jacket frame structure's seismic performance are studied; Meanwhile, structural optimization of the isolation jacket frame using cost-effectiveness criterion is also performed. The main research contents are summarized as follows:(1) This part has carried out the study of the integral seismic performance evaluation of the targeted building. On the basis of structural tests, reliability assessment and seismic performance evaluation for the existing masonry structure, using the performance index of deformation and energy for masonry structures, the integral seismic performance evaluation method is studied and a conclusion that the structure needs seismic reinforcement is drown.(2) This part has carried out the study of performance-based isolation reinforcement and seismic performance evaluation for the targeted building. the building is strengthened by using the method of performance-based isolation reinforcement, which includes determination of fortification target, determination of macroscopical performance objectives and quantified performance objectives, the characteristics of the restoring force in the isolation layers, determination of isolation devices and isolation parameters, the arrangement of isolation devices, the design of energy dissipation structures, the analysis of seismic response and seismic performance evaluation.(3) Based on the performance, the research has been made to assess the improved outer frame's story-adding methods and vibration mitigation properties which are used in the masonry structure vibration isolation of the targeted building. The masonry structure of the building have been analyzed and made some reconstruction of story-adding based on the performance of vibration reduction and strengthening. Using the performance of seismic design concepts, the performance objectives of story-adding transformation have been proposed. Specifically through the comparison and analysis of the two kinds of seismic responses of the storey-adding improved constructions, which are including the non-isolation outer framework and the base-isolation ones, the conclusion has been drown that outer framework's "high chicken-leg" structure is not conducive to the overall structure of the seismic performance, but the earthquake damage of the structure can be reduced by using the base-isolation methods, the established performance objectives of story-adding transformation can be satisfied and the seismic performance of the overall structure can be improved.(4) A structural optimization research has been made on the masonry structure's story-adding transformation of the vibration isolation outer frame in the targeted building. Based on investment-benefit criterion, the total cost of the outer framework in its whole life is defined as the objective function. The design parameters and constraints of the optimization model have been determined after considering the optimization characteristics of civil engineering structure and the use of the PKPM software. Furthermore, the outer framework structure of the targeted building has been calculated and analyzed optimally, and a number of important conclusions for storey-adding transformation of the optimization model has been drown.