| Currently in China, the general specification of seismic design method is known as “three seismic fortification levels and two-stage design methods”. i.e. In order to make the structure meet the requirements for seismic resistance, the reinforcement of the structure is based on the calculation results of microseismic elastic, as well as combining with other demanded anti-seismic measures. This current method lacks the calculation of structure’s performance under major earthquake, thus it is impossible to examine the structure’s damage status and overall performance during the rare and severe earthquakes. But performance –based seismic design theory effectively made up for the inadequacy of the current design method. We sought to apply the seismic design method based on evaluating structural components’ performance in this study directly to get the damage degree of the structure under strong earthquakes and to judge the overall safety of the RC frame-core wall structure. Hence, we were able to examine if the structures under current design measures could meet the seismic fortification requirements, in order to provide a new constructive reference to future engineering practice. The concrete research content is as follows:(1) According to the current structure design specifications, we designed and developed eighteen RC frame-core wall structures with different structural heights, fortification intensities and site categories. We specifically chose twenty seismic waves time histories that met with the current standards for each model, and performed the analyzes of structural elastic-plastic time-history of a severe earthquake. All the analyzes were performed in Perform-3D and PPP(Perform-3D Pre/Post Program). We found that the majority of the designed models did not exceed the limit value of macroscopic deformation standards. Additionally, there were significantly different distributions of shear force and moment among framework and core wall, i.e. the shear force was mainly directed to core wall, while moment was distributed by both core wall and frame.(2) We additionally combined the elastic-plastic analysis results with component deformation index, using PPP to complete the evaluations for structural components’ performance. The results showed the frame beam’s performance was positively correlated with the story drift at that frame beam’s layer. Damage to the core wall was all concentrated at the first story. Core wall’s performance was only associated with the drift of the first story, and no association was found with the largest inter-story drift. Frame columns could maintain high performance without getting any severe damage by the strong earthquake. Other findings included the seismic waves could lead to severe structural damage had a response spectrum curve greater than the standard spectrum during the long period(3)Through this study, we clearly identified the overall safety specification for structures,and suggest completing the evaluation for structures’ safety under severe earthquake by utilizing structure safety assurance as the control index in the future.We concluded that the structure with seismic fortification of 7 degree had a better safety, and safety assurance rate achieved 100%. Some models under 7.5 degree or 8 degree seismic fortification failed to meet the safety requirements. Further comparison with the evaluation based on structural deformation showed current specification has a loose standard in deformation control among weak layer. The current specification also uses largest story drift as the safety evaluation index, which cannot intuitively show the actual damage of the structure and the results of the assessment will be conservative. |
PDF Full Text Request