| In recent years,due to the sudden and destructive nature of the earthquake,it has brought huge casualties and economic losses to countries around the world.Concrete column is the most important load-bearing component in building structure.If it is damaged in the earthquake,it will cause the overall collapse of the building structure.Therefore,how to improve its seismic performance is the research and attention of relevant scholars.As a new type of cement-based reinforcement material,Textile Reinforced Concrete(TRC)is suitable for use in humid environments,and does not entrain moisture to cause freeze-thaw cycles after reinforcement.At the same time,cracks formed in the matrix are usually also It will appear in the reinforcement layer,which is convenient for visual inspection after reinforcement.It has attracted extensive attention from scholars at home and abroad and carried out a series of research.However,there are few related studies on the seismic performance of TRC-reinforced RC columns.Therefore,it is of great theoretical and practical significance to further study the seismic performance of TRC-reinforced RC columns.In this paper,the seismic performance of TRC-reinforced reinforced concrete columns is analyzed by numerical simulation.Five factors,including textile layers,axial compression ratio,shear span ratio,stirrup ratio and core concrete strength,are considered to influence the seismic performance of reinforced concrete columns strengthened by TRC.According to the numerical results,the variation laws of stress and strain clouds,hysteresis curves,skeleton curves,stiffness degradation and energy dissipation capacity of TRC columns were analyzed.Finally,based on the grey system theory,the gray correlation degree analysis of each influencing factor is carried out.The main influencing factors are selected and the BP neural network model is established.The displacement ductility coefficient prediction of the reinforcement column is studied.The main conclusions are as follows:(1)When building TRC reinforced RC column model in ABAQUS,the damage plastic constitutive model of concrete is adopted in the concrete constitutive model,which can effectively simulate the tension cracking,compression crushing and stiffness degradation of core concrete of TRC reinforced column under low cyclic reciprocating load.The linear reinforced elastic-plastic constitutive model can not only simplify the constitutive relationship of reinforcing bars,but also better reflect the real stress-strain curve of reinforcing bars,and avoid the difficulty of convergence in calculation ofABAQUS in yield stage of ideal elastic-plastic model.The textile reinforced concrete(TRC)can be divided into a textile grid and fine-grained concrete to simulate the performance of TRC material.The warp fibre bundle and the zonal fibre bundle of textile are assumed to be ideal linear elastic material;when the fibre bundle reaches the ultimate strength,the fibre bundle is judged to be broken.Fine grained concrete is assumed to be a concrete material using the constitutive relation of concrete.(2)The numerical calculation results in ABAQUS are compared with the experimental results.the load-displacement hysteresis curves and keleton curves obtained by finite element analysis is more consistent with the overall trend of the test curve.However,there is a certain gap between the calculated curve and the actual curve of TRC-constrained concrete.This is because the numerical model established in this paper does not produce experimental errors during loading process.For example there is no negative slip in the model during loading process.However,the actual test in the negative loading process,due to the reasons of test equipment and the inaccuracy of physical alignment before the beginning of the test,the negative slip occurs during negative loading.Moreover,the damage degree of material in the numerical model under low cyclic reciprocating load is smaller than that in the actual test.At the same time,in the finite element analysis of this paper,the uniaxial stress and strain are adopted in the constitutive relation of concrete,and the bond slip between the reinforcement and the concrete is neglected.However,the actual test is a low-frequency cyclic loading test,in which the stiffness and strength of concrete are reduced by different degrees under the action of reciprocating load,and small bond slip between the steel and concrete will also appear.This shows the rationality and feasibility of the finite element analysis model established in this paper.(3)For TRC strengthened columns,the peak load,displacement ductility coefficient and cumulative energy dissipation capacity of strengthened columns increase with the increase of the number of textile layers.However,when the number of strengthened layers exceeds three layers,the increase of the number of textile layers is limited.With the increase of the number of textile layers,the energy dissipation rate of strengthened columns also increases slightly.With the increase of axial compression ratio,the yield load and peak load of TRC strengthened columns also increase,but the displacement ductility coefficient and energy dissipation capacity of RC columns decrease with the increase of axial compression ratio.With the increase of shear-span ratio,the yield load,peak load and ultimate load of reinforced columns decreasegradually,but the ultimate displacement increases accordingly.With the increase of stirrup spacing,the yield load,peak load and ultimate load of reinforced columns do not change significantly,but with the decrease of stirrup spacing,the ductility coefficient and energy dissipation capacity of reinforced columns will increase.With the improvement of core concrete strength,the fullness of the hysteresis curve of the reinforcement column is continuously reduced,the pinching effect is more and more obvious,and the peak bearing capacity is also continuously improved.However,when the concrete strength of reinforced columns is between C30 and C40,the displacement ductility coefficient and cumulative energy consumption increase with the increase of core concrete strength,but the concrete strength increases again its change is not obvious even has the reduction.(4)In this paper,grey relational analysis in grey system theory is used to analyze displacement ductility coefficient of TRC reinforced columns.The correlative values of layers,axial compression ratio,shear span ratio,stirrup ratio,concrete strength and displacement ductility coefficient of TRC reinforced columns are obtained.The BP neural network model of five-storey structure is established to predict the displacement ductility coefficient of TRC strengthened columns.The prediction results show that the model is suitable for predicting displacement ductility coefficient of TRC strengthened columns.Based on the test results and finite element simulation results,the ductility calculation formulas considering the layers of fiber braided nets,axial compression ratio,shear span ratio,stirrup ratio and concrete strength characteristic value are proposed. |
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