Experimental Study And Numerical Simulation Of Composite Torsional Behavior Of Reinforced ECC Column

A large number of experimental studies show that ECC has good compressive,tensile and shear properties,and its ductility,toughness,and ability to control cracks are much better than reinforced concrete.ECC is a relatively mature subject and research object.Scholars at home and abroad have done a lot of research on it,but most of them still stay in the analysis of a single stress situation.In fact,a single force is almost non-existent in engineering.Therefore,it is meaningful and necessary to study the composite torsion performance of the reinforced ECCZ.In this paper,through the monotonic static test of five ECCZs and one RCZ under the combined action of compression,bending,shear and torsion,the composite torsional performance of ECCZ is studied with the parameters of axial compression ratio,shear span ratio,torsion bending ratio and stirrup ratio.At the same time,ABAQUS is used to establish its finite element model to further verify the test results and laws.The results show that the torque torsion curve and stress nephogram obtained by the simulation can be in good agreement with the test results and have a high degree of agreement.The following is the main research content and results of this paper:(1)Through the test results of five ECCZs and one RCZ,it is found that: compared with the RC column,the cracks are less but very different in width,and all the ECCZs are fine and multi cracks with good integrity when they are damaged.The data shows that the minimum peak torque of all ECCZs is also 50.48% higher than that of RCZ.It shows that ECC material has better integrity and crack control ability than ordinary concrete.(2)Although the numerical simulation of ABAQUS is less intuitive than the experimental phenomenon,the errors of the main characteristic values are less than 15%,and the composite torsional performance of the test piece can be accurately reflected within the controllable range,which indicates that the ECC simulation in this paper The results for composite torsion columns are reliable.(3)When comparing the finite element simulation value with the test value.It is concluded that the peak torque of the simulation curve is greater than the test value.This is caused by many reasons:The ECC compression constitutive model selected in the simulation is not exactly the same as the actual compression constitutive model.The value of fracture energy is an estimate,not an actual value;In the experiment,ECC damage is accumulating,while the value of damage factor in the simulation is fixed;the test device is simplified in the process of modeling,which results in the deviation of results.Because the first crack observed by human eyes is often not true and accurate,but the criterion of ABAQUS software is unified.Therefore,it is difficult to find the rule between the test value of cracking torque and the simulation value.(4)The parameters are axial compression ratio,torsion bending ratio,shear span ratio and stirrup ratio,and the range of parameters is enlarged.According to the analysis of the torque torsion rate diagram,the following rules are obtained: the axial compression ratio increases,the peak torque increases,but the ductility decreases;the shear span ratio increases,the peak torque decreases,but the ductility increases.When the torque to bending ratio is increased,the peak torque and ductility are not significantly improved.It shows that it is very important to choose the proper torsion bending ratio.The increase of stirrup ratio can effectively improve the peak torque and ductility of the specimen,and the stirrup spacing has a greater impact than the stirrup diameter.