Study On The Influences Of Different Adjustment Schemes Of Bearing Capacity And Stiffness On The Seismic Performance Of Frame Structures

The performance-based seismic design is a subject worthy of further study and there are many systematic work to do. It will be of great significance to select the appropriate and effective performance-regulated measures to improve seismic performance of the structure by performance-based seismic design. And the first thing we need to know is the specific influences of several common performance-regulated measures on the seismic performance of a structure. So as to make clear the corresponding schemes which can be taken to improve the seismic performance of a structure by performance-based seismic design.Under this background, a series of analysis on the different adjustment schemes of bearing capacity and stiffness and both of them at the same time to a regular frame structure located in region 0.15 g of intensity 7 were carried in this thesis. By comparing the results of their inelastic dynamic analysis and IDA and vulnerability analysis in detail, the influences of changes of the component bearing capacity and stiffness and both of them at the same time on the seismic performance of the frame structure were explored. The targeted plan and the possible relatively optimized combination of the measures were proposed which can be taken to improve the specific seismic performance of the frame structure.The main innovations of this thesis are as follows. The first is the direct comparison of the seismic performance of different bearing capacity and stiffness adjustment schemes to achieve the purpose of testing the effectiveness of the relevant performance-regulated measures. The second is the overall consideration of four different seismic intensity level such as frequent earthquake and fortification earthquake and rare earthquake and 1.5 times the rare earthquake, and a detailed comparison of the drifts and floor shears and inelastic energy consumption ratio and plastic damage of the component. The third is the comprehensive comparison of different adjustment schemes of a seismic structure in the process of the gradually increasing in ground motion intensity based on the IDA and vulnerability analysis.Conclusions gained from above research work are as follows:(1) The increase of bearing capacity delayed the frame structure to get into the inelastic stage, and reduced the plastic damage of components and the maximal inelastic drifts under strong earthquake obviously. The collapse resistant capacity and the bearing safety reserves had been increased significantly. So that the seismic safety of the structure was improved. On the other hand the deformation of the structure during service was not improved.(2) By increasing section size of the components to enhance stiffness of the frame structure without significantly adding the amount of reinforcement improved the deformation of the structure during service. But did not obviously reduce the plastic damage of components and the maximal inelastic drifts of structure under strong earthquake due to the rapidly degraded of the stiffness. The collapse resistant capacity and the bearing safety reserves had not been improved significantly. So the seismic safety of the structure was not improved under strong earthquake.(3) The proper increase of the structural stiffness and the bearing capacity at the same time improved seismic performance of the frame structure all the way in the process of the gradually increasing in ground motion intensity. It improved both the deformation of the structure during service and the seismic safety under strong earthquake. And the corresponding improvement effect were significantly superior to the schemes of only adjusted the same range of stiffness or bearing capacity. To a certain extent, it combined the beneficial effects of increasing the stiffness and the bearing capacity individually, and overcomed their problems at the same time. It was the best way to improve the seismic performance of the frame structure, and the relatively favorable degree would be more obvious with the increasing of ground motion intensity.The revelations gained from above analysis are as follows. The different performance-regulated measures taken by performance-based seismic design would lead to quite different performance optimization effect. The same regulated measures might have different effects on different performance parameters, and the optimization effects of the same performance parameters achieved by the same control measures could relate to the ground motion intensity. Designers shoud pay more attention to this phenomenon, and need to conduct further analysis and demonstration on the seismic performance of the structure after taking a certain performance-regulated measure.First of all, we need to make clear the expected target is to focus on improving the seismic safety or to meet the special deformation function during service when the seismic performance of the structure needed to be improved. Then we can make a choice of the targeted plan which is mainly to increase the bearing capacity or to improve the stiffness or to make a reasonable combination of them at the same time. According to the results of this thesis, the best performance-regulated scheme to a simple regular frame structure is a reasonable combination of both improving the structure stiffness and increasing the component bearing capacity at the same time. So as to optimize the seismic performance of a structure in a comprehensive and balanced manner.