Experimental Study On Seismic Performance Of Reinforced ECC Columns Under Torque

Engineered Cementitious Composite(ECC)is an Engineered Cementitious Composite with high ductility,quasi-strain hardening and multi-crack development,and its ultimate tensile strain energy is stable and up to 3%.Due to its excellent durability and tensile properties,ECC materials can be used to significantly improve the seismic performance of structures.Therefore,in recent years,there have been more and more researches and applications on ECC materials.This paper systematically studies the seismic performance of ECC structural specimens through methods of experimental research and theoretical analysis.In this paper,six ECC specimen with different axial compression ratio,torsional flexural ratio and shear span ratio and one RC specimen are used as the comparative test to conduct the seismic performance test under the action of low cyclic reciprocating torque.The author observed and described the crack development and failure characteristics of specimens during the test.The failure morphology,torsional hysteresis curve,skeleton curve,torsional ductility,energy dissipation performance,strength degradation and stiffness degradation of specimens were studied,and the influences of axial compression ratio,torsional bending ratio and shear span ratio on the torsional performance of specimens were analyzed.The test results show that the ECC column has obvious characteristics of multi-crack cracking and torsional ductility.Compared with ordinary concrete specimens,the cracking torque,yield torque,ultimate torque and ultimate torsional rate of ECC specimens are obviously improved.The axial compression ratio is reduced,the torsional torsional ratio curve is relatively full,the limit torque is improved,the limit torsional ratio is improved obviously,the torsional ductility is improved,the torsional stiffness degrades relatively quickly,and the strength degrades slowly.The shear span ratio of specimens was improved,the specimens cracked earlier,the torsion ductility was improved significantly,the degradation rate of torsion strength was accelerated,and the energy dissipation capacity of torsion was slightly reduced.Improving the torsional flexural ratio of specimens is conducive to improving the torsional deformation and ductility of specimens.The degradation rate of torsional stiffness is relatively fast and the degradation of torsional strength is accelerated.This paper deduces the calculation formula of cracking torque and ultimate torque of ECC specimens under the action of bending shear.It compares calculated results with the test results,concluding that the calculation formula can precisely calculate cracking torque and ultimate torque of the ECC specimens.The test results can provide reference for developping relative standard and engineering design.