钢纤维高强混凝土的中应变率本构关系

采用分离式霍普金森压杆(SHPB)对纤维体积率为0～3%的钢纤维高强混凝土(SFRHSC)进行了中应变率的冲击压缩试验.试验表明,应变率从阀值提高到90 /s时,SFRHSC峰值应力增幅30%左右,弹性模量增幅50%左右,峰值应变增长幅度则是基体混凝土的2～3倍.集料-高强基体和钢纤维-高强基体的双重叠加效应,大大提高了基体的抗冲击强度和韧度,使SFRHSC试件在冲击荷载作用下呈现出"微裂而不散,裂而不断"的良好破坏形态,而在相近的冲击荷载下,基体混凝土试件成粉碎性破坏.根据试验结果建立了SFRHSC四参数率相关性本构方程,该方程同时考虑了应变率和应变对材料应力的影响.

Constitutive relation of SFRHSC at medium strain rate

Impact compression experiments for the steel fiber reinforced high strength concrete(SFRHSC) at medium strain rate were conducted using the split Hopkinson press bar(SHPB) testing method.The volume fractions of steel fibers of SFRHSC were between 0 and 3%.The experiment results show that,when the strain rate increases from threshold value to 90 /s,the maximum stress of SFRHSC increases about 30%,the elastic modulus of SFRHSC increases about 50%,and the increase in the peak strain of SFRHSC is 2-3 times of that in matrix specimen.The strength and toughness of the matrix can be improved remarkably because of the superposition effect of the aggregate-high strength matrix and steel fiber-high strength matrix.As a result,under impact loading,cracks may develop in the SFRHSC specimen however the overall shape of the specimen may remain virtually unchanged.As a contrast,under similar impact loading,the matrix specimens are broken almost into small pieces.On the basis of the experiments,the rate-dependent constitutive equations with four key parameters are established,which take both strain rate and strain effect on the material stress into account.