Experimental Study On The Mechanical Performance Of ECC Square Section Shortcolumns Confined By Stirrups

Engineered fiber reinforced Cementitious Composite is a kind of material with high strength,high toughness,high ductility and well control crack ability,which can improve significantly the mechanical properties and durability of the concrete structure.Previous,studies mainly focused on the mechanical properties of the unconfined ECC,while the confined ECC was less studies.In this contribution,the uniaxial compressive experiments of ECC square short columns were conducted.The influence of the stirrup spacing and configuration,ECC strength and section size on the confined ECC stress-strain curve were analyzed.The results show that:1.By direct tension test of PVA-ECC dumbbell specimens,the ultimate tensile strain of PVA-ECC can exceed 3%,many micro cracks appeared in the specimen and the specimens showed the strain hardening characteristics.By the uniaxial compression test on PVA-ECC cube specimens and cylinder specimens,the relationship between PVA-ECC cube compressive strength and unaxial compressive strength was established.2.Based on the uniaxial compressive experiments on ECC square section short columns,the influence of stirrup spacing and configuration,ECC strength and section size on mechanical property of confine ECC were studied,and the influence of various factors on stress-strain curve of confine ECC were studied,the results indicate that the decreased section of stress-strain curve become more gently and the effect of confine is better with the smaller stirrup spacing,lower ECC strength and compound stirrup.3.On the basis of the theoretical analysis on constraint mechanism of the stirrup,the calculation formula of restraint stress of stirrup applying to ECC square section short columns was set up.Based on test results and theoretical analysis,the calculation formula between peak stress,peak strain,ductility ratio of ECC constrained by stirrups and effective constraint index were proposed.The results of the study can provide basic data to the following application of ECC.4.By comparing the existing calculation model of stress-strain curve of confined concrete,the calculation model of ECC square section short columns was set up.The results of the study can provide basic data to the practical engineering applications of ECC.