Uniform Collapse Risk Targeted Seismic Design Methodology For Reinforced Concrete Frame Structures

This thesis focuses on the collapse safety of reinforced concrete frame structures and aims to achieve uniform collapse risk for RC frame structure within its desigh service life. To this end, the main research work of this thesis are as follows:(1) The collapse capacities of 40 RC frame structures designed in accordance with China’s current seismic desigh code are quantitatively evaluated, with collapse fragility analysis, which is based on incremental dynamic analysis(IDA). The collapse margin ratios(CMRs) of the 40 RC frame structures mainly range between 2.0 and 3.5; the record-to-record uncertainties mainly range between 0.40 and 0.55.(2) The collapse modes of the 40 RC frame structures, each subjected to 44 ground motion records, are observed. The vertical progressive collapse mode trigerred by the direct loss of gravity load carrying capacity in frame columns of lower stories is the dominent collapse mode for RC frame strucutres. In addition, the collapse of multi-storey RC frame structures usually begins in the lower stories, and is controlled by the first-mode response.(3) The source of uncertainties in structural collapse capacity is categoried and the modelling uncertainy in collapse capacity is assessed by center point method.(4) The risk of earthquake-induced collapse that a building structure may experience during its design service life is proposed to assess the collapse safety of building strucutres, which comprehensively accounts for the seismic hazard. The fundamental concept of uniform-risk-targeted seismic design and its relevant assessment process are presented. Based on the next-generation China’s seismic nozation map, the minimum collapse capacity of building structures is suggested with the collapse safety target that the conditional collapse probability sugjected to the collapse-prevention-level earthquake is less than 10% and that the total collapse probability within 50 years is less than 1.0%.(5) The seismic collapse capacity of SDOF systems is evaluated via an incremental dynamic analysis, based on which the fundamental concept of the collapse capacity spectrum is proposed. The influence of various structural properties and the influence of ground motion features on the collapse resistance of SDOF structural systems are comprehensively discussed by using the proposed collapse capacity spectrum.(6) A simplified seismic collapse capacity evaluation method for multiple-story RC frames based on equivalent SDOF system is proposed and demonstrated step by step. the collapse capacities of 40 multiple-story RC frames obtained from the proposed method are compared against those from the rigorous IDA-based method. The result shows that the SDOF-based method proposed in this paper is capable of predicting the collapse capacity of multiple-story RC frames with sufficient reliability and considerable low computational cost.