International Journal of Civil and Structural Engineering Research ISSN 2348-7607 (Online) Vol. 6, Issue 2, pp: (15-21), Month: October 2018 - March 2019, Available at: www.researchpublish.com
Experimental Study on the Effect of Horizontal Reinforcement on the Shear Strength of Concrete Masonry Walls Ahmed Faisal Oan1, Nigel Shrive2 1
Assistant Professor, Egyptian Russian University, Cairo, Egypt 2 Professor, University of Calgary, Calgary, AB, Canada
Abstract: The vulnerability of unreinforced masonry walls (UMW) to seismic forces led to the use of horizontal reinforcement to improve the performance of the masonry walls and to increase (as thought) the resistance of the walls to horizontal forces. There is no doubt that the use of horizontal reinforcement enhances the post crack performance of the walls, but there has been a debate of whether the use of horizontal reinforcement increases or does not affect the overall shear resistance of the masonry walls. An experimental program was designed to examine the effect of horizontal reinforcement in bond beams and its distribution on the shear resistance of the walls. The results showed that the use of reinforcing rebars in bond beams had no significant effect on the maximum shear resistance of the walls. Also, distributing the same area of reinforcement over the height of the walls did not affect the maximum resistance of the walls but affected the crack pattern. Statistical analysis methods were used to verify the obtained results. Keywords: Shear resistance, masonry, bond beams.
1. INTRODUCTION The effect of using horizontal reinforcement in masonry walls has been extensively studied by many researchers in order to explore its benefits and advantages on the shear behavior of masonry walls. The investigations was divided in two main groups, where some researches focused on studying the effect of bed joint reinforcement e.g. Schultz et al. 1998, Jasinski 2010 and Oan and Shrive 2010.While the other group of researchers investigated the effect of horizontal reinforcement embedded in bond beams e.g. Scrivener 1969, Matsumura 1987, khattab and Drysdale 1993 and Nolph and ElGawady 2012 In both cases, the reinforcement has proven to improve the post crack behavior of the masonry walls, but the effect of the shear reinforcement on the maximum shear resistance of the walls has been a point of debate of whether it increases or does not affect the shear resistance. For example Voon and Ingham 2006 showed that the horizontal reinforcement increases the shear resistance of the walls, while other researchers showed that adding the horizontal reinforcement does not affect the maximum shear resistance e.g. Oan and Shrive 2014. Also, Shing et al. 1989 showed that the initiation of diagonal cracks depends on the applied axial load and the tensile strength of the masonry units and does not depend on the amount of reinforcement which supports that the resistance of horizontally reinforced walls is independent of the steel content of the wall. Grouting the masonry walls can increase the shear resistance of the walls as have been proved in many studies e.g. Voon and Ingham 2002. In the same way, if a grouted beam is added to the wall (i.e. bond beam) the shear resistance will increase and that is what some investigators ignore when studying the effect of horizontal reinforcement in bond beams and relate the increase in shear resistance to the shear reinforcement only and ignore the effect of adding another structural element (the bond beam) to the wall which divides it into two panels and increase the resistance e.g. Ghanem et al.1992 and Maleki et al. 2009. The masonry in not a homogeneous material and there should be some variation in results, for example the Canadian Code (CSA 2004) states that when testing five prisms to obtain the compressive strength of masonry if the variation in results is more than 15%, then ten prisms should be tested, which means inclusively that it allows for variation in results up to 15%, and hence one can argue about the significant effect of shear reinforcement where most of the researchers who showed that horizontal reinforcement increases the shear resistance of walls had results showing less than 10% increase in
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