Numerical Analysis of Strengthening R.C Slabs with Opening using Ferrocement Laminates Mahmoud Elsayed Assistant Professor, Civil Engineering Department, Faculty of Engineering Fayoum University Fayoum, Egypt Abstract—in this paper the structural behavior of reinforced concrete slab with a centered square opening strengthened with ferrocement laminates were investigated with nonlinear finite element analysis. The 3-dimensional feature available in the commercial analysis package ANSYS was used to model the specimens. The model accommodates the material non- linearities cracking and crushing of concrete and yielding of steel. Verification of study was calibrated with strengthened and unstrengthened numerical model by available experimental data. The studied parameters were; thickness of ferrocement layer, percentage of expanded wire mesh reinforcement in the ferrocement cover layer, compressive strength of mortar. Based on the results and observations of the numerical investigations presented in this research regarding the effectiveness of ferrocement laminates in strengthening slab with opening, it can be seen that ferrocement laminates can be successfully used for increasing the ultimate carrying capacity, strength, and energy absorption. The results showed that use of ferrocement enable the slabs to restore its full load capacity and increased its ultimate load carrying capacity up to 2 times. Keywords— Ferrocement, R.C. slab, Opening, Finite Element and strengthening. I. INTRODUCTION Reinforced concrete (RC) solid slab are quite common structural systems, and has been widely used for the multi- story building. Openings in floor slabs of buildings are required for many purposes like stairs, air conditioning ducts and elevators. Introducing openings in slabs can severely weaken the slabs due to the cut-out of both concrete and reinforcing steel. Several strengthening techniques have been developed in the past and used with some popularity including steel plate bonding, and non-corrosive innovative strengthening systems, such as fiber-reinforced polymers (FRPs), that have the potential for extending service lives of RC structures and reducing maintenance costs, are required to replace old strengthening systems. Ferrocement is one of the strengthening techniques, which is widely used in the last years to increase the structural capacity of the structural members or in case of damaged slabs, to restore the original capacity of the section. Hence, the aim of this study was to investigate the effect of using ferrocement laminates strengthening alternatives to restore the flexural capacity of the RC slabs with cut out at middle. The ferrocement laminates was externally bonded to the tension face of the slabs to strengthen reinforced concrete slabs with cut-out against flexural failure. Strengthening by ferrocement laminates is a popular method due to its availability, cheapness, and easy to work. II. FINITE ELEMENT ANALYSIS A. Finite Element Modeling The general-purpose finite element program ANSYS is used in the present study to investigate the flexural behavior of strengthened RC slabs with opening previously studied experimentally. An extensive use of the finite element method for the numerical modelling for all R.C. slabs with cut-out. The three-dimensional, eight-node solid element (SOLID65), available in the ANSYS library, was used to model both concrete and ferrocement mortar. SOLID65 element is an eight-node solid element used to model the concrete with or without reinforcing bars, as shown in Figure 1. The element has capability to model the concrete while the rebar capability is available for modelling the reinforcement behavior. The solid element has eight nodes with three degrees of freedom at each node translations in the nodal x, y, and z directions. The element is capable of plastic deformation, cracking in three orthogonal directions, and crushing. The most important feature of this element is that it can represent both linear and nonlinear behavior of concert. The rebar reinforcement feature of this element was used to model the mesh reinforcement of ferrocement while 2-noded element was used to model the descrete steel bars used to reinforce the original specimens. The reinforcing steel bars were adopted using (LINK8) element. B. Numerical Modeling of Slab The test specimens were simply supported along the four edges. The dimensions of slab specimens were 1000x800x100 mm with (200*200 mm) square central opening. Each slab was reinforced with Ф10 @200mm in two directions, to simulate the actual case in nature all slabs has no additional reinforcement along the opening sides. A displacement control incremental loading was applied at four symmetrical points at 200 mm from corner of opening in two directions. Small initial load steps were used for detecting the first crack in the connections. Then, automatic time stepping (deltim=0.01) was used to control the load step. C. Boundary Conditions In this study, making advantage of the symmetry in geometry and loading, the simulated model is constructed in the form of one quarter of the slabs due to the two axes of symmetry (500*400*100 mm). Thus, the boundary condition of these International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 www.ijert.org IJERTV4IS060487 (This work is licensed under a Creative Commons Attribution 4.0 International License.) Vol. 4 Issue 06, June-2015 412