| In recent years, the method of capacity spectrum attracted much more attention in the field of structural engineering than ever before. The nonlinear characters of struc-tures may be developed to higher degree, when they are loaded the forces of earthquake. How can we make the intersection between the spectrums express the same nonlinear character with nonlinear spectrum? The intersection has the ability to express the top of structure's displacement exactly? The concept of demand region constructs a new idea of capacity-demand curve method. In order to make better use of this idea, this the-sis is intended to use large universal finite element software SAP2000 to achieve de-mand region, and to propose improvement measures.First, the simplified capacity-curves have not enough precision and we can't give right parameters for the program. For example, the intersection between the capacity curve and demand curve can't represent the same kind of nonlinear state exactly. The excessively simplified capacity curves will reduce the precision of calculation using the method of capacity-demand curves. Some developed countries have their own elas-tic-plastic displacement spectrum, our country have not the spectrum yet. Then how can we calculate maximum top displacement of the refined member based nonlinear dy-namic time-history analysis of frame structures when the demand curves are to be cal-culated by the design response spectrum?The second, how to delete the discrepancy between the method of pushover analy-sis and the method of dynamic time-history analysis of structure? For example, the pushover curve analysis has no way to consider the hysteretic energy and the energy dissipation in other ways, and to consider the material fatigue and the scathe in the structures'to-and-fro motion.The work done in this thesis is mainly as follows for trying to make better of the capacity-demand curve in existence: 1. describe the related concepts and the develop-ment history of pushover analysis; introduce the principle and the analysis steps of ca-pacity-demand curve method, which is the basis of pushover analysis function in SAP2000. 2. Find the rules of structural response resulted from pushover analysis and dynamic elastoplastic analysis; the method of conversion relationship between the re-sults of the pushover analysis method and the results of structural dynamic time-history analysis is found. The main conclusions reached in this paper are: we can get two pushover (capacity) curves in SAP2000 through acceleration loading and mode loading instead of rectangu-lar loading and inverted triangle loading; we can get two demand curves through changing the constitutive relationship of steel bar and concrete, and through finding both the upper and lower limits of the constitutive relations, we can get the demand curve envelope; analyze the irregular structure examples by SAP2000 in both the posi-tive and negative direction ,the structural response is of little difference; the analysis of the selected examples confirms that envelope from the change of the demand region re-sulted from the change of demand and the capacity curves can more accurately deter-mine the results of the pushover analysis; summarize and verify the correlation law be-tween the pushover analysis and the dynamic time-history analysis preliminarily ; deal-ing with the results of the capacity-demand curve method according to this laws can re-duce the calculation error between the two methods.
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