Theoretical Study On Bending Performance Of Polyvinyl Alcohol Fiber Reinforced Cementitious Composite Beams

PVA fiber reinforced cementitious composite material is a composite material made by mixing cement,fly ash,sand,PVA fiber and water in a certain proportion.This material has the advantages of strain hardening and multiple cracks under uniaxial tensile load,which can solve the problems of low tensile strength and difficult control of crack width of ordinary concrete materials.PVA fibers are randomly dispersed reinforcements in the cement base.It can partially replace the tensile steel bars to optimize the reinforcement.Drawing on the existing research results of our research group,this paper carried out a theoretical study on the flexural deformation properties of PVA fiber reinforced cementitious composite beams.Based on the actual force of the PVA fiber reinforced cementitious composite beam,a force and deformation model of the test beam was established.The deflection,crack width and curvature ductility coefficient calculation method are also proposed.The research work done in this paper is as follows:(1)Considering the change of the neutral axis position of the test beam in different working stages,a calculation method for the deflection was established.(2)Based on the bond-slip theory,a calculation model for the tensile stress of the reinforcement layer between cracks,and an average crack spacing calculation model considering the change in the neutral axis position before and after cracking were established.Finally,the calculation method of crack width was obtained.(3)Starting from the definition of the curvature ductility coefficient,the calculation formulas of the curvature of the PVA fiber reinforced cementitious composite beam at the time of yielding and the limit were derived.Finally,the calculation method of curvature ductility coefficient was established.(4)The effect of different volume ratios of PVA fibers on the load-deflection relationship curve,bending moment-curvature relationship curve and crack morphology of the test beam was studied.The results show that the PVA fiber reinforced cementitious composite beams exhibit excellent load-bearing deformation ability.And the number of cracks increased with the increase of PVA fiber volume ratio;the crack height and crack spacing decreased with the increase of PVA fiber volume ratio.