Application of Equilibrium Truss Models to Continuous Reinforced Concrete Solid Webbed Deep beams and with web Openings

Abstract

The purpose of the current research is to investigate the possibility of applying the so called 'Equilibrium Truss Models' to the design of continuous reinforced concrete deep beams with or without web openings. The proposed method provides a simple and easy-to-apply technique to analyze such beams as compared to more complicatcd numerical methods such as the Non-Linear Finite Elements'. The power of the method lies in the fact that it is a design method, where the designer can decide the force path (truss) and consequently provides the necessary dimensions and reinforcement to enable the suggested truss, while other numerical methods can only check the stresses in an already designed element where the concrete dimensions and steel reinforcement are already known. In the first chapter of this thesis, 'Strut-and-Tie Models', or 'Truss Model' are reviewd, with special attention paid to the application to disturbed regions in the structure. Elements of truss models including struts, ties, and nodal zones are introduced and discussed. In the second chapter, a literature survey of the design of deep beams is introduced. Some important experimental tests on such elements are discussed, with special emphasis on the difference in behavior between deep and shallow beam elements. The proposed truss modeling technique was used to analyze 12 deep beams (3 simply supported and 9 continuous beams). In chapter three, the experimental program is introduced, where 4 quarter scale continuous deep beams were tested to failure. Details of the test set-up, loading devices and specimen instrumentation can be found in this chapter. Special strut reinforcement were used in the tested beams to increase the strut capacity, and to enhance the overall beam ductility by preventing brittle modes of failure. It was found that all tested beams failed al a load higher than that predicted using truss models. The calculated truss capacity was about 90% of the recorded failure load in all tested beams, indicating that the method provides a consistent lower-bound solution. In chapter four, 16 deep bcams, including the four tested beams were analyzed using a non-linear finite element program (NLFEA90) and the program results were compared to the experimental data.