Optimization And Assessment On Seismic Performance Of Reinforced Concrete Structure

This study is organized to assess the seismic performance of a high-rise reinforced concrete (RC) frame-core using the comprehensive nonlinear finite-element analyses. For that purpose, the following contents are included:(1) A multi-objective optimization method based on damage control function of story group and failure probability is proposed. Two performance indices, the damage control function of story group and failure probability, are defined, and through incremental dynamic analysis, the peak ground acceleration corresponding to the structural failure probability of 50% is selected as the objective earthquake intensity, and the section dimension of components is used as the variables to conduct the structural optimization analysis. A 30-story reinforced concrete frame-core structure is optimized. It is indicated that the inter-story drift angle distribution of optimized structure is more uniform than that of the original structure, and the damage gradually decreases from the top to the bottom. Collapse Margin Ratio (CMR) is increased by 29.8%, and the working coordination between the wall and the frame is strengthened, and the seismic performance of structure after optimization has been significantly improved.(2) The structural seismic performance assessment method is proposed based on Performance Analysis Cost Tool (PACT) and cost-benefit criteria. The method used fragility curve based on incremental dynamic analysis (IDA) to calculate the probability of different damage states, and further to calculate the whole economic loss assessment index. Taking a 30-story reinforced concrete frame-core structure as an example, the method is used to assess the structural seismic performance. Results indicate that the damage loss of interior walls after optimization is reduced by about 20% under medium earthquakes, and the seismic performance of walls is enhanced. The repair costs of outer frame are decreased by about 25%, the whole economic loss is decreased by 35%, and the structural seismic performance is enhanced under strong earthquakes. The method can effectively assess the structural seismic performance before and after optimization, and the validity of the optimization method based on damage control function and fragility is further verified.(3) Taking the increase material costs of structure after optimization by the method based on damage control function and failure probability as the constraint, braces are installed on a 30-story reinforced concrete frame-core structure, and the seismic performance of structure with different optimization methods is compared. Results indicate that the repair costs of all the performance groups of structure with braces are decreased by 40% under medium earthquakes, and 19% under strong earthquakes compared with that of the structure optimized by the method based on damage control function and failure probability. The later economic loss of structure is effectively reduced by adding braces, but the failure probability of structure after optimization based on damage control function and failure probability is 5% to 10% smaller and the Collapse Margin Ratio is about 18% higher than that of structure with braces, and the whole seismic performance is better than that of the structure with braces.