Theory And Methods Of Performance Based Seismic Design For Irregular Reinforced Concrete Frame Structures

Performance based seismic design (PBSD) theory is recognized step by step in earthquake engineering field, and the research about it is becoming a principal topic. PBSD is a seismic design innovation, which is on the basis of seismic performance analysis of structures and can exert the subjective ability of the engineer adequately. Therefore research on PBSD has important value for seismic design of practical structures. Centering round theory and methods of performance based seismic design for irregular reinforced concrete frame structures, this dissertation involves the following work.The gap in probability of exceedance between frequent earthquake and extremely rare earthquake is very large in china seismic design code, therefore, a new definition of occasional earthquake is bring forward to form a four level seismic fortification criterion. Based on the statistical data of seismic performance test of RC columns, two index of temporarily operational and reparably operational performance levels are put forward. Examples are presented to demonstrate that buildings satisfied the fully operational level under frequent earthquake is not ensure to be in temporarily operational level or reparably operational level under rare earthquake. If the frequent earthquake is substituted by the occasional earthquake, the problem above can be solved well.Based on the dynamical equation of single degree of freedom, a parameter of yield strength coefficientζ_y is introduced to deduce the dynamical equation of ductility coefficient. Then the ductility demand spectrum, which comprises a group of ductility coefficients or yield strength coefficient versus natural period curves for different yield strength coefficient or ductility coefficients are obtained. Based on the pushover analysis, a new performance-based seismic evaluation method, constantζ_y ductility spectrum method is established. Examples are presented to demonstrate the applicability and utility of the proposed methodology.Based on the summarization and research of conventional lateral load patterns for nonlinear static analysis, two methods based on the modes of MDOF, which are called 30% rule method, partial SRSS rule method, are established to calculate the lateral load for pushover analysis. Considering the story stiffness, a new improved lateral load distribution is established for vertically irregular building structures. Examples are presented to demonstrate the applicability and utility of the proposed methodology.The deformation of vertically irregular frame structures under earthquake is vary different to that of regular frame, thereby, a new method named Inter-Story Capacity Spectrum is put forward for the PBSD of vertically irregular frame structures. The new method can be used to design a vertically irregular frame considering different performance level under different earthquake hazard level, at the same time the modal of structures, the spectrum of seismic design code are taken into account. Also the Inter-Story Capacity Spectrum method can be used to evaluate the seismic performance of vertically irregular frame structures. Examples are presented to demonstrate the applicability and utility of the proposed methodology.Based on the research of the torsion effects caused by the earthquake load, four methods calculated the lateral load distribution for asymmetric structures are established. They are two-times distribution method, storied distribution method, dynamic eccentricity method and dynamic storied distribution method. Examples are presented to demonstrate that the pushover results including the distribution of hinges, inter-story drift ratio and inter-story torsion angle, used the four methods are coincidence well with that of nonlinear time history analysis.The relationship between inter-story torsion angle and torsion deformation ratio is deduced base on the rule of irregular plan structures in China tall building technical specification. Considering the inter-story ratio limitation of different performance levels under different earthquake hazard levels, a series of torsion angle demand curves are established and a new method named as Torsion Angle Capacity Spectrum is put forward for the PBSD of irregular plan frame structures. The method also can be used for the performance based seismic evaluation of irregular plan structures. Examples are presented to explain the method principle and to demonstrate the applicability and utility of the proposed methodology.Considering different unit model and different hysteretic model, selecting forty earthquake records, one hundred and twenty structure-earthquake system samples are obtained for RC irregular frame. Selecting the weakness story inter-story drift ratio and the maximum torsion angle respectively, through the nonlinear dynamic analysis and linear regress, a new fragility analysis method is put forward for vertically irregular frame and irregular plan structures. Examples are also presented to demonstrate the applicability and utility of the proposed methodology. It is concluded that fragility analysis can be used together with the performance based seismic evaluation method, which is conduced to realize the seismic performance of buildings accurately and systemically.