Flexural characteristics of an extruded polystyrene slab with truss system reinforcement

Abstract

Concrete is an extremely important construction material, yet when we design flexural elements much of the concrete used is under-utilised because it is placed in tension in order to provide the necessary binding and cover to the lower reinforcement. On the other hand, the steel reinforcement in reinforced concrete beams is used to handle the bending and shear stresses that develop within the beam, whereby the longitudinal bars take the bending stresses and the vertical bars take the shear forces. In this dissertation this reinforcement was altered by changing the orthogonal reinforcement to truss reinforcement; ergo changes in behaviour and performance were noted. This was also taken a step further by removing the sacrificial concrete in the tension zone and replacing the strut action that used to be provided by the concrete by the truss reinforcement itself, in order to provide the necessary mechanical shear transfer required for flexural behaviour to occur. The beam managed to attain an adequate load-displacement ratio when compared to the local construction requirements as well as when compared to the L/250 and L/360 deflection criteria, showing that there is still an amount of inherent safety in the system. The beam experienced a deflection of over 105mm and still managed to retain the load imposed on it, even if at a lesser stiffness than the linear elastic region. This dissertation aims at providing the reader with an overview of the relevant literature and the methodological process adopted in testing the beams, as well as some further insight into how this system could be made a viable structural solution.