Study On Design Method For RC Frame Structures To Resist Progressive Collapse

Progressive collapse (PC) resistance design provides an efficient measure forintegrity and robustness of building structures under accidental loading. The designmethods for Reinforced Concrete (RC) frame structures in resisting PC aresystematically investigated in this study. The main achievements are as follows:1. Analysis and evaluation of PC resistance of RC frame structures. Themechanisms of PC resistance and characteristics of load-redistribution of typical RCframes, designed by the Chinese codes, are analyzed by the nonlinear dynamic alternatepath method and nonlinear static Pushdown method. A PC probability index (PI) and acollapse resistance capacity index (CI) are suggested and used to evaluate the PCresistance of the typical RC frames. The computational results indicate that theproposed two indices, PI and CI, are able to comprehensively evaluate the PC resistancefrom the perspectives of overall capacity and local weakness of RC frame structures,respectively.2. Analysis of PC resistance demand of RC frame structures based on the energyconservation principle. A theoretical framework of the collapse resistance demandanalysis for RC frame structures is established. In this framework, two conciserelationships between the nonlinear dynamic and linear (or nonlinear) static collapseresistance demands are derived based on the energy conservation principle. Uponvalidation through numerical examples, the proposed framework has helped to providetheoretical foundation and calculation method for engineering application.3. Development of engineering design methods for RC frame structures in resistingprogressive collapse. The establishment of the collapse resistance demand relationshipshas fundamentally improved the empirical calculation methods as specified in thecurrent linear static alternate load path design method. The deficiencies of thecalculation model in the existing tie force method are discussed, and an improvedmethod taking into account the load pattern, support stiffness, spatial ties and nonlineardynamic effect is suggested. The reliability of the two proposed methods are verifiedthrough numerical examples. 4. Development of the numerical models for fire-induced PC analysis of RC framestructures. The models are established based on the coupled thermo-mechanicalconstitutive laws and the fiber-beam and multilayer-shell finite element theories. Theaccuracy and efficiency of the models are validated through a series of tests under fire.5. Provision of recommendations for fire-induced PC analysis and design of RCframe structures. The effect of integrated cast-in-situ slabs and concrete spalling underelevated temperature on the PC resistance of RC frame structures is studied in somedetail. An real fire-induced PC accident is simulated and analyzed. Based on theoutcome of the numerical investigations, recommendations are provided forfire-induced PC analysis and design of RC frame structures.