Improved Capacity-Demand-Diagram Methods For Estimating Seismic Deformation Of Inelastic Structures

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 structures may be developed to higher degree, when they are loaded the forces of earthquake. How can we make the intersection between the spectrum express the same nonlinear character with nonlinear spectrum. The intersection has the ability to express the top of structure's displacement exactly? The method of capacity-demand curves can solve the problem. There are still some defects in the method. The 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 elastic-plastic displacement spectrum, our country have not the spectrum yet. Then how can we calculate maximum top displacement of the refined member based nonlinear dynamic time-history analysis of frame structures when the demand curves are to be calculated by the design response spectrum? The second, how to delete the discrepancy between the method of capacity-demand curves 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. Confirm the factors those caused the discrepancy between the different capacity curves: the shape of lateral load distribution, assumption of member bars model, irregularity of the structures, P-Δeffects. The most important of them is found by some analysis of structure modal. 2. The order of the capacity curves' distribution and the data of the maximum base shear and the top displacement of the structures are founded. 3. The effect of nonlinear datum to the demand curves during the course ofmaking equivalent linear systems.4. Method of ATC-40 (Procedure-B) is improved; the improved method is more exactly in calculating the top displacement of the structure. The method of conversion relationship between the results of the capacity-demand curves method and the results of structural dynamic time-history analysis is found...