Seismic Performance Analysis Of Two Concrete Frames Reinforced With Different Types Of FRP Bars

Corrosion of steel bars is one of the main diseases of concrete structure,and this problem can be solved by replacing steel bars with FRP bars.At present,considerable study has been conducted to research the behavior of FRP reinforced concrete members at home and abroad,while research on the seismic performance of FRP reinforced concrete frame structure is far from enough.Based on the results of FRP reinforced concrete members,further study has been conducted to investigate the seismic capacity of FRP reinforced concrete frame structure in this paper.Firstly,two quarter scale concrete frame structures reinforced with CFRP bars and GFRP bars respectively were designed,and shaking table test design was completed.Then,dynamic elastic-plastic time history analysis was carried out on two model structures.According to the simulation results,the seismic performance of two FRP reinforced concrete frame structures was analyzed and compared.Finally,the seismic performance of two test model structures was analyzed and evaluated by performance-based seismic design and evaluation theory.The main works of this paper are as follows:Firstly,model design and shaking table test design of two FRP reinforced concrete frame structures were finished.The mechanical property test was carried out on CFRP and GFRP bars,and the stress-strain constitutive model was established.Then,two 1/4 scale model structures,whose reinforcements were CFRP bars and GFRP bars respectively,were designed using dimensional analysis method;and the reinforcement calculation of model structures obeyed equivalent principle of bending and shearing ability.Next,the acceleration sensors,concrete and FRP bar strain gauges were arranged;and four earthquake excitations which were El Centro wave,Taft wave,Wenchuan wave and Lanzhou artificial wave,were selected considering factors such as site classification and seismic fortification intensity.Moreover,in total thirty test cases were designed,including seventh degree frequent earthquake,seventh degree basic earthquake,seventh degree rare earthquake and eighth degree rare earthquake.The effects of single,double and three directions seismic action were considered.Secondly,dynamic elastoplastic time history analysis was conducted on two model structures using SAP2000 finite element analysis software,from which to gain dynamic characteristics such as vibration modes and natural period and dynamic responses such as acceleration and displacement response of two model structures.The analysis results showed that the change rate of natural period of GFRP model was greater than that of CFRP model,indicating that the damage degree and stiffness degradation of the GFRP model were more serious.Besides,the acceleration and displacement response of CFRP model were smaller than those of GFRP model,which implied that CFRP model owned greater lateral stiffness and carrying capacity.Two model structures both met the seismic fortification goal and had enough security reserve.In addition,the dynamic response was not only related to the peak value of acceleration,but also to the spectrum characteristics of seismic waves.The seismic response of two model structures was largest when excited by Wenchuan wave,and it was suggested to input earthquake waves in the order of Taft wave,El Centro wave,Lanzhou artificial wave and Wenchuan wave when conducting shaking table test.Finally,the seismic performance of two model structures was analyzed and evaluated by performance-based seismic design and evaluation theory.The ground peak acceleration was selected as the intensity measure,and the maximum story-drift angle was used as the damage measure.Then the incremental dynamic analysis(IDA)was carried out on two models,and many IDA curves were obtained through interpolation fitting of discrete points using Origin software.After that,the IDA curves were aggregated into 50%,16% and 84% quantile curves,and the ability values of three different quantiles under different performance points were statistically determined.The IDA curves showed that two model structures both behaved good deformability and anti collapse capacity.The deformability of GFRP model was superior to that of CFRP model,while the anti collapse ability of CFRP model was stronger than that of GFRP model.Furthermore,the IDA curves did not become flat when the peak ground acceleration reached 0.788 g,implying that two model structures did not collapse and had better seismic capacity and larger safety reserve.