Shear behaviour of continuous fibre-reinforced lightweight aggregate concrete beams

Abstract

A series of shear tests on six fibre-reinforced lightweight aggregate concrete (FRLWAC) beams containing both steel and polypropylene fibres are presented in this paper. These beams were designed and cast with different boundary conditions, steel fibre contents, and shear-span-to-depth ratios (a/d). From the test programme, it was found that an addition of 0.5 % of steel fibre by volume significantly improved the shear behaviour of continuous FRLWAC beams and mitigated the concern of low shear resistance associated with lightweight concrete. The addition of steel fibre enhanced the direct strut strength of FRLWAC beams in shear and improved the efficacy of stirrups in transferring shear forces. The test results also suggested that continuity effect prevented sudden and complete loss of load-carrying capacity in FRLWAC beams failing in shear, although it did not significantly increase the shear-carrying capacity. A strut-and-tie model was proposed to predict the shear resistance of continuous FRLWAC beams. The contribution of steel fibre in enhancing the efficacy of compression struts and stirrups was considered in this model. This model was shown to be accurate in predicting the shear resistance of FRLWAC beams and was more accurate and reliable compared to available shear strength prediction provisions in different design codes. It also presents a viable alternative to a three-dimensional finite-element model for predicting the shear resistance of continuous FRLWAC beams.