Seismic Performance Analysis Of GFRP Reinforced Concrete Frame Structure Based On IDA Method

A large number of statistical data at home and abroad show that steel corrosion is one of the main reasons for the failure of reinforced concrete structure and the failure to complete its service life.The application of FRP(fiber reinforced polymer)bars in concrete structures can effectively solve the problem of steel corrosion,which has become a consensus in the field of civil engineering.However,a large number of earthquake damage events at home and abroad show that under the action of strong earthquakes,buildings are vulnerable to serious damage or even collapse,resulting in huge economic losses and casualties.Therefore,whether FRP bars can be widely used in concrete structures and whether they have good seismic performance is very critical.In recent years,the research on the application of FRP bars at home and abroad is mainly focused on beams,columns and other structural components,and the research on the overall seismic performance of FRP reinforced concrete frame structure is less.The shaking table test research on the seismic performance of FRP reinforced concrete structure is carried out.The IDA analysis and seismic vulnerability analysis of GFRP reinforced concrete frame structure are carried out by using the finite element method.On this basis,the recoverability analysis is carried out to further evaluate the seismic performance of the structure and provide the basis for the seismic design of the structure,which has important social significance and economic value.On the basis of shaking table test and finite element analysis,this paper uses incremental dynamic analysis(IDA)to analyze the seismic vulnerability and recoverability of GFRP reinforced concrete frame structure.The main conclusions are as follows:1.The simulation results show that the acceleration response and displacement response are consistent with the test law.At the same time,under the earthquake action of 30 working conditions,the model does not collapse,which shows that the structure can meet the anti-seismic fortification concept of "big earthquake does not fall".2.The peak ground acceleration(PGA)is selected as the index of ground motion intensity and the maximal story drift angle as the damage index of the structure.The results show that: on the whole,when PGA is small,IDA curve is basically a straight line,monotonous increase,indicating that the structure is in the elastic stage at this time;with the increasing of PGA,the maximal story drift angle also increases,IDA curve begins to fluctuate,structural damage intensifies,and enters the elastic-plastic stage,until the slope of IDA curve approaches 0,the maximal story drift angle tends to infinity,the deformation of the structure increases infinitely,and finally collapse occurs.3.Through the vulnerability analysis of the model structure,the seismic vulnerability curve of the structure is obtained.The results showed that when PGA=0.4g,= 96.12%,and the failure probability is about 1.At this time,the point of structure exceeding DS1 limit state is almost a certain event.With the increase of PGA,the damage degree of the structure increases and the slope of the curve decreases.When PGA=0.6g,the failure probability of DS2 and DS3 is 89.76% and 43.83% respectively,while the failure probability of DS4 is only1.61%.The results show that with the yield of members,the structure enters into plastic state,showing good seismic performance.4.According to the IDA results,the failure probability matrix of the structure is obtained,which can quantify the probability of different damage states of the structure under the seismic action of each intensity.The results show that: the probability of exceeding DS1 limit state point is the highest under each fortification intensity,which indicates that the structure will easily go beyond the elastic stage and enter the elastic-plastic stage under earthquake action,which is related to the mechanical properties of materials,that is,when the concrete exceeds the elastic limit and cracks appear on the surface,the GFRP Bars and steel bars do not yield,and the seismic performance cannot be fully evaluated develop.The probability of exceeding DS3 point is very small under each fortification intensity,and it is only 14.83%under 8 degree rare earthquake,which indicates that the bearing capacity of GFRP reinforced concrete frame structure still has large development space and high bearing capacity within the elastic-plastic range.5.The structural collapse safety reserve coefficient CMR proposed in ATC-63 report is introduced to calculate the CMR value of the model under each fortification intensity.Combined with the recommended value of CMR in ATC-63 report,the collapse safety reserve of the structure meets the requirements.6.The seismic recoverability of the structure is evaluated from two aspects: the overall and stage seismic recoverability indexes.The results show that the overall seismic recoverability index of the structure=0.531>0.500,which is in line with the characteristics of class a curve and the damage development trend of the ideal structure as a whole.Stage seismic restorability index decreases gradually in each damage stage,which reflects the situation that the restorability ability decreases with the development of damage.Combined with the above two indexes,the seismic recoverability grade of GFRP reinforced concrete frame structure is evaluated as grade C.Calculate the expected value of the seismic capacity ratio of the structure under the specific strength,check the safety of the structure under the seismic action of the specific strength,and get the corresponding seismic capacity safety reserve.7.The design idea based on seismic recoverability is initially established,and two methods are proposed to improve the seismic recoverability of the structure,including optimizing the structure and setting isolation and energy dissipation devices.