| How to select the adequate procedure for seismic analysis and design of structures is an essential problem in earthquake engineering field. With the development of Performance-based Seismic Design, Pushover Analysis procedure has attracted many scientists'and engineers'attentions and been widely used for its conceptual simplicity and computational attractiveness. To overcome the limitation of Pushover Analysis procedure, some improvements on this procedure were performed in this paper, including the improvement on Modal Pushover Analysis, the revision of target displacement from the pushover analysis for reinforced concrete frame, the correlation of structural response parameters with different lateral load patterns, and the computation of the structural hysteretic energy based on Modal Pushover Analysis etc. The main contents of this dissertation are as follows.1. There is an important assumption that the pushover load patterns keep unchanged even after the structure yields in Modal Pushover Analysis procedure. Recognized the adoption of invariable lateral force distributions in the Modal Pushover Analysis procedure, an improved modal pushover analysis procedure is presented in this paper to estimate the seismic demands of structures, considering the redistribution of inertia forces. It is suggested that after establishing the idealized bilinear curve, a pushover analysis is once again conducted for the first mode in two phases: before and after the structure yields. For the two phases, the structural elastic natural mode and the floor displacement vector at the initial yielding point are used as the displacement shape vector, respectively.2. The approximately estimating method of displacement of reinforced concrete (RC) frame from static pushover analysis (POA) is developed with that from non-linear response history analysis (RHA). Based on the statistic analyses of the RHA and POA results for five RC frames with different height under 80 ground motions recorded at four site conditions, the revised formula of displacements from POA is presented from RHA. The results show that the site soil condition has an important effect on the relation between RHA and POA response results. And the POA results for I and IV site condition should be revised with the formula given in this study while the POA results for II and III site condition can be approximately considered as same to the RHA results.3. The RHA under 15 ground motions recorded on the medium site condition and POA with different lateral load patterns are performed for four RC structures with different height. Several important response quantities are obtained from the RHA and POA, including capacity curves, top displacement ratios and story drift ratios, and location of plastic hinges. The influence of different load patterns on the structural performance demands is discussed for the low- and the high-wise structures. And the rational load patterns for the low- and the high-wise structures are also suggested.4. A simple procedure is presented in this paper for estimating hysteretic energy demands of MDOF systems based on the modal pushover analysis (MPA). Firstly, the characteristic parameters of the modal SDOF systems of structures are computed, and the hysteretic energy is calculated for the modal SDOF systems, then the hysteretic energy demand of structures is obtained by combining these modal demands. In addition, with statistic results of nonlinear analysis of SDOF for 320 ground motions recorded at four site conditions, the equal-strength hysteretic energy design spectra are presented for different site condition and intensity regions.
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