Study On Seismic Damage Control-based Design Methodology For RC Frames

Controlled ductility damage is permitted for building structures subjecting to rare earthquakes. One of the key factors in ensuring the seismic performance of structures under rare earthquakes is the reasonable structure damage. The structure damage is consist of damage mechanism, degree of damage and distribution of damage. The capacity design method is a traditional structure damage mechanism-control procedure. However, there are some limitations existing in this method. The adjusting relative capacity between columns and beams is based on elastic internal forces of structures under minor earthquake and the internal force redistribution of structures subjecting to rare earthquake, which is critical for ensuring the structure damage mechanism, is not directly considered. Earthquake damage investigation and preliminary analysis show that the effective degree of the traditional method is limited. It is important to develop an effective seismic design method to control the structure damage mechanism. Structure damage rationality evaluating is the foundation of damage mechanism selecting and controlling the degree of damage. However, there is lack of scientific method for designing building structures with reasonable structure damage. The damage mechanism, the degree of damage and evaluating the rationality of structure damage for reinforced concrete(RC) frames are three major research aspects in the dissertation. Major contents and achievements are as follows:① After analyzing the experimental results published previously, a modified ParkAng seismic damage model is proposed based on low-cycle fatigue theory and Miner’s rule to consider the load path effects. Then the modified model is verified by the cyclic test results of RC columns from the database arranged by the Pacific Earthquake Engineering Research Center(PEER). The relevant parameters of the modified model are derived by nonlinear regression analysis. The damage indexes for each characteristic damage state of structure components are recommended.② One 4-story-3-span RC frame specimen of 1/3 scale is tested under pseudostatic loading. The damage development process and damage mechanism are carefully studied.③ 20 RC frames with different fortification intensities and storeys are designed according to the current Chinese seismic design code. And then these structures are modeled using OpenSees. The failure probability of typical damage mechanisms are calculated with the reliability theory. The main typical damage mechanisms subjecting to different intensities of earthquake are identified.④ The generalized demand-to-capacity ratio method is proposed to control the damage mechanism of RC frames. The global state of the structure is expressed as a function of its components’ states according to the cut-sets concept in reliability theory. The columns and beams connecting to the same node are taken as the smallest design unit. Then, the control of damage mechanism is achieved through the expected damage component and not damage components based on adjusting the internal force under the rare earthquake. A seismic design procedure is proposed to design the preseted structure damage of RC frames based on the substitute structure analysis. The performance of the proposed design method in controlling structure damage is proved effectively through several case studies.⑤ The substitute structure analysis is extended to predict structure components hysteretic energy demand and peak floor acceleration of RC frames. The adequate and high computational efficiency of the proposed method are verified by case studies.⑥ The process of PEER-PBEE methodology for calculating earthquake loss is simplified based on the extended substitute structure analysis. Then a procedure for evaluating the rationality of structure damage is put forward as comprehensively considering the effect of economic and safety. The procedure is proved reasonably and effectively through case studies.⑦ Based on the generalized demand-to-capacity ratio method, preseted structure damage design method and the structure damage rationality evaluating procedure, the seismic damage control-based design methodology for RC frames is suggested. A practical example is used to illustrate the design procedure, and it is validated by time history analysis. Results show that the expected objectives are achieved by using the suggested design method.