Study On The Flexural Performance Of Textile Reinforced ECC-RC Composite Beams

In order to effectively solve the problems of low crack resistance and poor durability of reinforced concrete structure,fiber reinforced concrete has attracted wide attention.Engineered Cementitious Composites（ECC）is one of them,which has the advantages of high ductility,multi crack steady cracking and high durability.The ECC-RC composite beam formed by replacing the concrete in tension zone of ordinary RC beam with ECC has obvious advantages in crack resistance and crack limit.Compared with ordinary RC beams,the bearing capacity of ECC-RC composite beams increases slightly with the increase of ECC layer thickness.However,due to the distribution of chopped fiber in ECC,ECC-RC does not significantly improve the bearing capacity;and ECC is expensive,the thicker the ECC layer,the higher the cost of the composite beam.In order to further improve the bearing capacity of ECC-RC composite beam and reduce the cost,this paper adopts textile reinforced ECC-RC composite beam（TRECC-RC beam）and studies the flexural performance of the composite beam through four point bending test.In this paper,the influence of textile ratio and ECC height on the crack development,bearing capacity and load displacement curve of TRECC-RC composite beam is studied.The test results show that when TRECC-RC composite beams are damaged,the steel bars yield first,the concrete in the compression zone is crushed,and the textile is partially or completely broken.The failure mode is typical reinforced beam failure.The cracks of TRECC-RC composite beam are "fine and dense".Compared with ECC-RC beam,the application of textile can further increase the number of cracks and reduce the width of cracks.However,the number of textile layers has little effect on the number of cracks.When the ECC thickness is the same,the cracking load,yield load and ultimate load of TRECC-RC composite beam increase nonlinearly with the increase of the number of layers of textile;when the textile ratio is the same,the cracking load of TRECC-RC composite beam first increases and then decreases with the increase of ECC thickness,and the yield load and ultimate load increase with the increase of ECC thickness.The thickness of ECC has little effect on the stress sharing of TRECC-RC composite beam,and the textile has an obvious effect on the stress sharing of TRECC-RC composite beam.The more layers of textile,the better the effect of stress sharing.Based on the above research and test results,the bending process of TRECC-RC composite beam is divided into three stages: pre cracking stage,post cracking to steel yield stage and yield to failure stage.On the basis of plane section assumption and material constitutive model,the bending process formula of TRECC-RC composite beam in each stage is deduced.The results show that the formula can accurately predict the cracking moment,yield moment and ultimate moment of TRECC-RC composite beams.The derivation of the formula lays a foundation for further study on the flexural design method of TRECC-RC composite beams.There are 10 tables,30 pictures and 111 references in this paper.