Experimental analysis for evaluation of shear properties of High Strength SFRC beams

The configuration of bond of high strength concrete is rather unlike to normal concrete and is a prime concern in this context. The behavior of sudden failure of high strength concrete under shear force is perhaps due to the aggregate interlocking mechanism and its failure plane. The incorporation of steel fibers acts as a crack arrester may overcome this problem and improves the ductility and yielding performance of high strength SFRC up to the great extent. The purpose of recent study is to investigate the influence of steel fiber contents, longitudinal reinforcement on the performance of high strength steel fiber reinforced concrete (HSSFRC) beams in shear. Beam specimens of high strength SFRC and conventional concrete were prepared for M60, M70 and M80 grades of concrete. The various parameters such as steel fibre volume (Vf) with varying percentage of 0%, 0.5%, 1%, 1.5% and 2%, longitudinal reinforcement ratio (ρ), web reinforcement ratio, deflection and ultimate shear strength were taken into account. The performance of beam specimens was checked in shear, deflection and failure plane when subjected to four point loadings.
Jagdish Chand, S.M. Gupta and Babita Saini Department of Civil Engineering, National Institute of Technology, Kurukshetra – 136119, Haryana, India

Introduction

Concrete as a construction material is used on large scale all over the world in view of its compressive strength, structural stability, high mouldabilty and economic considerations. Also, it is very strong in compression; but, its tensile strength is comparatively very weak [1]. Ordinary conventional concrete has been replaced with high strength concrete due to improvement in physical properties in the construction industry from the last few decades. The development of new water reducing admixtures and the mineral admixtures is making it possible to produce more reliable high strength concretes in the recent years [2]. The direct compression test method is used to determine its compressive strength. However, there is no direct method to determine the tensile and/or shear strength concrete. Therefore, attempts have been made to predict the indirect split tensile strength of concrete by casting and testing cylinders and prisms [1, 3]. Concrete being a non-homogeneous, heterogeneous material and have non-linearity in its material response [4, 5]. As a result of this, it is not feasible to apply a shearing action (direct shearing force) in a plane, as a common practice is done in case of metals. Steel bars generally provided along a direction perpendicular to shearing force, act to resist shearing force. The shear resistance due to these longitudinal steel bars is commonly referred as dowel effect [5, 6, 7]. However, incorporation of such steel bars does not contribute much in the tensile strength of concrete [8, 9, 10]. A small amounts of fibers introduced in concrete may improve the shear properties of high strength concrete. The concept of introducing the natural fibers in brittle building materials is not new and had been used from ancient civilizations to reinforce deteriorating adobe bricks [5, 6, 11, 12, 13]. Although different types of natural, synthetic and steel fibers are available; but, more research has been performed using steel fiber in concrete and further investigations about material properties and behavior are still required to be studied. The introduction of steel fibers in concrete significantly improves its ductility and thereby improves