| In recent years,a large number of Reinforced Concrete(RC)frame structures collapsed in the earthquakes,causing heavy casualties.The seismic risk analysis method describes the annual probability of collapse of building structures,providing an important basis for the prediction of the seismic collapse capacity of building structures.It can significantly improve the seismic performance of RC structures with fiber reinforced concrete(FRC)in the expected damage region instead of ordinary concrete,However,the seismic risk of FRC structures has not been evaluated.It is complicated and time-consuming to adopt incremental dynamic analysis(IDA)method to conduct the seismic risk analysis.Therefore,this paper intends to study a simple and effective method to evaluate the seismic risk.The main contents and achievements of the paper are presented as follows:(1)Static nonlinear analysis was conducted by means of pushover method based on the methodology of the equivalent single-degree-of-freedom(SDOF)model proposed by Adam,and a base shear-roof displacement curve was attained.Based on which,the relationship between the force and the lateral displacement of the structure was derived.According to the force-displacement relationship and the shape function of lateral displacement of the MDOF system,the relevant parameters of the equivalent SDOF model were determined.After which the seismic collapse capacity of the equivalent SDOF model was calculated,and the results were translated from the equivalent SDOF domain into the domain of the MDOF system.An 8 stories FRC frame structure and an 8 stories RC frame structure were analyzed respectively.The results show that it is feasible and conservative to use the coresponding equivalent SDOF model to assess the overall seismic collapse capacity of structure compare to the MDOF system;the seismic collapse capacity for the FRC frame structure is higher than that of the RC frame structure.(2)Simplified methodology was adopted to evaluate seismic risk of FRC frame structure and RC frame structure respectively.Firstly,dynamic history analysis was conducted by means of incremental dynamic analysis(IDA)method,and an IDA curve was attained.On the basis of this IDA curve,the seismic fragility curve was derived.According to the seismic fragility curve and the epistemic uncertainty,the seismic fragility curve considering epistemic uncertainty was determined.Combining the seismic fragility curve considering epistemic uncertainty with the seismic hazard curve,the seismic risk was then evaluated.Thereafter,an evaluation procedure of seismic risk of structures is presented in the paper,which is based on the simplified methodology proposed by Laura Eads.An 8 stories FRC frame structure and an 8 stories RC frame structure which were designed according to the current Chinese codes were analyzed.The results show that the seismic risk using the simplified method is higher than that of the existing methodology,and the errors were 7.826% and 9.633% for FRC frame structure and RC frame structure respectively,therefore it is feasible and conservative to use the simplified methodology to estimate the seismic risk.(3)Seismic fragility and seismic risk analysis considering concrete creep were conducted for RC frame structure and FRC frame structure respectively.The seismic risk of RC frame structure considering concrete creep was attained based on the existing calculation method considering concrete creep.The seismic risk was analyzed assumeing that the creep coefficient of FRC were 2.5 and 3.0,then verify the applicability of the simplified method.The results show that the creep has a great influence on seismic collapse capacity,the mean annual frequency of collapse increase 327.723%(RC frame structure),291.953%(FRC frame structure with creep coefficient 2.5)and 293.432%(FRC frame structure with creep coefficient 3.0)considering creep,and it is feasible to use the simplified methodology to estimate the seismic risk for both FRC frame structure and RC frame structure for considering creep. |
