Damage Based Seismic Design And Global Seismic Capacity Analysis Of Reinforced Concrete Structures

With the development of social economy and increasing living level, seismic performance of buildings has been more and more requested by people. Performace-based seismic design (PBSD) theory is then put forwaR_D, and meets the development of times. The performance of buildings is clear accoR_Ding to PBSD theory. The main characteristic of this theory is that seismic design method is refered to one or more definite performance indices offered by the users of buildings, and then the performance of buildings is very definite after being designed. This idea changes the traditional one, i.e."little earthquake should not damage, middle earthquake can be repaired, and large earthquake could not collapse". Therefore, how to choose a reasonable performance index is a key problem in PBSD theory. Double-parameter damage model proposed by Park & Ang is widely used in the world because this model both consider the effect of maximum displacement response and the effect of cumulative hysteretic energy of buildings. In this paper, direct damage-based seismic design method is proposed on the basis of Park & Ang damage model. Also, nonlinear earthquake reponse spectra—damage spectra and its application are presented. Due to damaged characteristics of structural components (beams and columns) and nonconstructural components (infill walls), and combining with Wenchuan earthquake investigation, the analysis of infill walls affecting the global seismic capacity is carried out. A method of improving global seismic capacity based on failure of infill walls is also provided.The main research contents of this dissertation are as follows:Firstly, it is difficult to compute the maximum deformation response and hystertic energy of structure as concerned in Park & Ang damage model, especially for hystertic energy. The relationship between hysteretic energy and maximum deformation response is found on the basis of energy theory. Then, simplifed method of computing both parameters of Park & Ang damage model is presented. Furthermore, the former design mode as"designed by code and checked by damage index"is changed, which changed the check of the maximum deformation into damage index. Then, direct damage-based seismic design theory is advocated accoR_Ding to this damage theory, and indeed makes damage index functional during the seismic design.Secondly, inelastic damage spectra based on Park & Ang damage model is researched, called"R_D spectra". AccoR_Ding to the matlab program and a large amount of computing, the formula and regressive parameters of four kinds of R_D spectra are obtained. R_D spectra can consider both the effect of maximum displacement response and the effect of cumulative hysteretic energy of buildings. It is more advanced than the former response spectra which either considers effect of the maximum deformation (ductility) or energy effect, and more suitable for the inelastic behavior of buildings subjected to rare earthquake action. It is very important to consider the duration of ground motion by comparing R_D spectra with R_μspectra. Furthermore, inelastic response spectra can be used to estimate the deformation performance of buildings combining with the pushover analysis. Therefore, R_D spectra can be conveniently used to estimate the ultimate deformation (ductility) capacity of buildings with pushover analysis in the PBSD theroy, referred as collapse performance.ThiR_Dly, accoR_Ding to 5.12 Wenchuan earthquake investigation and combining with typical damaged characteristics of structural components (beams and columns) and nonconstructural components (infill walls), the analysis of infill walls affecting the global seismic capacity is carried out. Simplified FE analytical model of infill walls is also presented. After that, collapse process is simulated by Ansys/Lsdyna software as for out-of-plane problems of infilled frame. The results show that it is very important to consider the construction measures of infill walls to prevent from collapse. Furthermore, as for in-plane cracking problems, FE method is also conducted and the curves of cracking width of different kinds of masonry infills vs. storey drift angle of frame are obtained. The obtained results can be applied toPBSD for infilled frames in the future. Finally, the concept of allowed failure of infills (AFIs) is provided accoR_Ding to the fragile material character of infill walls and the function of buildings. AFIs are damaged and absort the earthquake energy first to protect the important structural components, and then increase the seismic fortification capacity of buildings. Hence, a method of improving the global seismic capacity of buildings is advocated by considering the function of AFIs. Also, damage control measure is researched in oR_Der to avoid the bad function of buildings due to damage of AFIs, i.e. Lead shearing damper is used to protect AFIs. After putting lead dampers, not only AFIs are protected, but also the global seismic capacity of buildings is improved.