Investigation On Global Collapse Resistance Of RC Frame Subjected To Severe Earthquake Considering Deterioration Characteristic

The earthquake disaster is one of the biggest threats to humanity. Earthquakesor mega-earthquakes can cause serious damage on engineering structures and theworst case is that engineering structures are collapsed totally or partially. It also cancause great number of casualties and incalculable loss of social property. Therefore,the study on global collapse resistance capacity of building structure under seismicexcitations has become the focus of the earthquake engineering, which becomes oneof the hottest branches of performance-based earthquake engineering research. Atpresent, seismic analysis and design based on collapse probability under greatearthquakes is the main trend in the field of earthquake engineering. Accurateevaluation of collapse resistance capacity is the key issue to achieve this target.Firstly, in this paper, research on collapse resistance capacity of structures athome and abroad is summarized first. The main research progress on progressivecollapse resistance and global collapse resistance of structures are briefly introduced.Based on this brief introduction, assessment approaches on collapse resistancecapacity and the fundamental theory of nonlinear analysis are also reviewed.Thecharacteristics of three kinds of nonlinear analysis models and their applicableconditions are introduced respectively. Then, the characteristics of hysteristicmodels, micro-and macro-constitutive models for analysis of reinforced concretestructures and the effect of structure component deterioration characteristics onglobal collapse resistance are mainly discussed. Based on the discussion, it isproposed that the deterioration characteristics should be considered in numericalanalysis model for collapse resistance capacity evaluation of RC framestructures.Nonlinear time history analysis is necessary tool to evaluate the collapseresistance capacity of structures. In this paper nonlinear time history analysis ismainly introduced, and nonlinear time history analysis theory is introduced in detailand the problems which may arise during nonlinear time history analysis and thecorresponding solutions are discussed. Besides, features and application methods ofOpenSees nonlinear analysis software are briefly introduced. And a cantilevercolumn is simulated by static pushover analysis, low cycle Quasi-static analysis andground motion time history analysis.It is proposed that considering the degradationcharacteristics of structural numerical model and P-Δ effects are the key issues to achieve accurate evaluation of structural collapse resistance capacity. Furthermore,it is also proposed that static push-over analysis and incremental dynamic analysis(IDA) are the best tools for structural static elastic-plastic analysis and dynamicelastic-plastic analysis respectively at present. How to get global collapse resistancefragility curve by means of IDA and how to determine the global collapse resistancelimit state are expounded. Secondly, in this paper, the adopted numerical model isassessed by comparing with the results between numerical simulation andexperiment. It is found that the model based on the degradation characteristics offiber cross-section element can provide good agreement with the nonlinear behaviorof RC structures or components.Finally, two numerical analysis models are established via OpenSees analysissoftware for global collapse resistance capacity evaluation. One is a RC one-baysingle-storey planar frame structure model and another is a RC three-bay six-storeyplanar frame structure model. RC one-bay single-storey planar frame structuremodel is taken as a case study to investigate the effect of the reinforcing steel poststrength degradation for evaluating the structural collapse resistance capacity, andanalytical results show that global collapse resistance capacity will be significantlyoverestimated without considering the post strength degradation of reinforcing bars.RC three-bay six-storey planar frame structure model is taken as a case study toinvestigate the global collapse resistance of multi-storey RC frame structures, inwhich both reinforcing steel post strength degradation and P-Δ effect are considered.It showed that the earthquake discrete function of multi-storey RC frame was morecomplex than single-storey, and multi-storey RC frame strengthening phenomenonmore apparent.