No abstract

A simpli"ed model is presented to predict the strength variations of brittle matrix composites, reinforced by steel "bres, with the variations of "bre parameters*length, diameter and volume fraction. This model predicts that its tensile and #exural strength increase non-linearly with the "bre volume fraction. It also predicts that similar non-linear behaviour should be observed with the reduction of the "bre diameter when other parameters are kept constant. The experimental results support both these theoretical predictions. It is also explained why an increase in the "bre length does not always signi"cantly increase the fracture toughness. The objective of this paper is not to explain and understand in great detail the science of all phenomena responsible for the strength increase of "bre reinforced brittle matrix composites, but to provide a simple engineering explanation as to why its strength increases with the "bre addition, and how this increase can be quantitatively related to the variations in "bre parameters*"bre volume fraction, "bre length and diameter. These simplifying steps are needed to provide a tool that the practicing engineers can use to predict the brittle matrix strength variation with the "bre parameters. In the area of geomechanics, the results presented here can be used to assess and predict the behaviour of "bre-reinforced earth.

In this paper, to intend anticorrosive effect and weight reduction of conventional reinforced concrete slab, lightweight concrete slab reinforced with glass fiber reinforced polymer(GFRP) bar was considered and some basic behaviour of the slab were investigated. Measurement of splitting tensile strength and fracture energy of the concrete, a number of flexural experiment of the slab, numerical analysis using nonlinear finite element analysis, and comparison of the experimental results to the numerical analysis, were conducted. As a result, even the weight of the lightweight concrete slab could be reduced by about 28% than the normal concrete slab, failure load of the lightweight concrete slab was 36% smaller than the normal concrete slab. Such a thing can be attributed to the lower axial stiffness and lower bond strength of GFRP bar. In the numerical analysis, to consider decreasing property of bond strength of the lightweight concrete, interface element was used between the concrete and the GFRP bar elements and this method was shown to be a better way for the numerical analysis to approach the experimental results.