SHEAR DOMAIN OF FIBER-REINFORCED HIGH-STRENGTH CONCRETE BEAMS

This paper concerns the incorporation of steel fibres in singly reinfo rced high strength concrete beams without stirrups Tailing under the c ombined effect of flexure and shear. An analytical model was developed and published for predicting the relative flexural capacity of steel fibre high strength concrete beams (M-u/M-fl) i.e. the ratio of moment with shear interaction to pure flexural moment, This paper investigat es the significant role of steel fibres in increasing the beam strengt h up to its full flexural capacity. An equation is derived for the cri tical shear span-to-depth ratio (a/d)(c) at which there is a maximum r eduction of the flexural strength due to shear influence, An analytica l approach is developed to determine the domain of shear effect, by wh ich it becomes possible to predict whether shear compression, diagonal tension, or flexural failure will occur for a given beam, The interac tion between steel fibres and longitudinal reinforcement bars is studi ed, and a nonlinear expression is derived for the optimum percentage o f fibres by which a singly rein-forced beam without stirrups reaches i ts full flexural capacity and does not fail in shear regardless of she ar span-to-depth ratio (a/d). (C) 1997 Elsevier Science Ltd.