Experimental investigation of the effect of high strain rate loading on the compressive behaviour of the steel fibre-reinforced concrete

Abstract

This research investigates the effect of loading rate on the compressive behaviour of steel fibre reinforced concrete (SFRC) designed to be used in prefabricated urban protective furniture. Although SFRC is known as a rate sensitive material and its dynamic and static compressive behaviour can be significantly different, the experimental studies on the loading rate sensitivity of SFRC in the range of impact have been rarely done compared to quasi-static. In the present study, the inertia effect in the range of impact as an important parameter for dynamic analysis of SFRC is considered. For this purpose, the SFRC mixture developed includes 1% hooked end steel fibres with length of 30 mm and aspect ratio of 80. The drop-weight impact tests were performed with three different drop heights, corresponding to maximum strain rates that range from 1 to 50 s-1. Using a servo-hydraulic testing machine, the quasi-static tests with four different loading rates were also performed with strain rates ranging from 10-6 to 10-2 s-1. The impact forces on top (impact force) and bottom (reaction force) of specimens were recorded in order to evaluate the inertia force and the stress wave propagation in the direction of the applied load. The strain and the strain rates were directly measured by three strain gauges installed on the specimens’ mid height and also indirectly measured using a high-speed video camera during the impact loading. The results show that, by increasing the strain rates, compressive strength, modulus of elasticity and energy absorption capacity of SFRC were increased. The dynamic to static ratios established for SFRC main properties are discussed and compared with those proposed by other researchers and recommended by CEB-FIP 2010. The models proposed by CEB-FIP describe quite well the dynamic increasing factor for the compressive strength of SFRC, at the measured strain rate range. The CEB-FIP models seemed to underestimate the increase in the modulus of elasticity experimentally measured for SFRC under impact loading.