Study On Probability-based Seismic Damage Mechanism Control Methodology For RC Frames

A reasonable structural damage mechanism is one of the key factor in achieving the seismic fortification goal of building structures under rare earthquakes.According to post-earthquake survey and a large number of related research results,the method by adjusting the elastic inner force for RC frames designed by Chinese seismic design code can not give a gurrantee to achieve the expected strong column-weak beam damage mechanism.Moreover,it is difficult to ensure the seismic performance of structures only by using the strong column-weak beam ratio.Based on the existing research results,this paper took reinforced concrete(RC)frame structure as the object,and used the failure probability as the evaluation criterion and control index to deeply study the control method of structural damage mechanism.Major contents and results are as follows:(1)Analysis of the influence of component correlation on the probability of structural damage mechanisms.Based on the existing research results,7 typical damage mechanisms are selected.According to the current Chinese Code,5 typical RC frames with different layers are designed in the regions with SFI=8(SFI:seismic fortification intensity,PGA=0.2g).The frames are modeled by using OpenSees program,and failure probability of the typical damage mechanisms are calculated considering component demand correlation.The change rule of damage mechanisms'occurrence probability is analyzed,and the influence of the different correlation between components on the failure probability evaluation of the structural system is verified.(2)A probability-based damage mechanism control design flow is proposed.Aimed at the strong column-weak beam damage mechanisms,the components are divided into the expected damage part and the non-damage part.The structure is designed based on the real response under rare earthquake obtained by static elastoplastic analysis.The relationship between the component's failure probability and structural failure probability is established.The model is adjusted and evaluated by probability.A design flow based on probability is proposed to design the damage mechanism of RC frame structure.The analysis of the example shows that the method can control the main damage mechanism and the overall failure probability of the structure under rare earthquakes.(3)Comparative analysis of seismic performance.According to the current code,frequent earthquake+gravity,and design flow of this paper,two sets of examples are designed respectively,and the elastoplastic time-history analysis of each model is carried out.The time-history analysis results of the models obtained by different design methods are compared and analyzed in deformation ability,damage distribution and failure probability.The effectiveness of the design flow in this paper is verified in terms of failure probability of structure and damage mechanism control.(4)Study on strong column-weak beam ratio?_c.The strong column-weak beam ratio?_c is taken as the parameter variable,and the failure probability and main damage mechanism of the structure are taken as the control indexes.The structure is designed according to the current design code and compared with the structure designed according to the flow of this paper.The proposed value?_c is given,and then its effectiveness on damage mechanism control is verified through several examples.