Theoretical and numerical approach of ultimate capacity of transversely prestressed concrete deck

Abstract

Introduction Many researchers have been discovered that bridge deck slabs which were designed to fail in bending, mostly fail under punching shear mode at a higher load than the expected for bending, because of the effect of in-plane compressive membrane forces, induced by the lateral restrained boundary conditions. Punching and bending failure modes are going to be analysed taken into account the enhancement due to compressive membrane action in the transverse prestressed concrete slab. Problem definition The objective of this thesis is to investigate the effect of compressive membrane action (CMA) in combination with the transversely prestress under a static point load applied at the midspan of the bridge’s slab. Research The aim of this thesis is to investigate the effect of the compressive membrane action and transversely prestress of the ultimate punching and bending capacity of a concrete deck slab. To develop the analysis of this scientific topic, research questions have been posed giving an orientation into the research and indicating the guiding components of the investigation. 1. Develop an analytical model to predict the ultimate capacity of a transversely prestressed slab accounting for the CMA and TPL. 2. To what extent can the CMA and the TPL contribute to the punching shear and bending capacity of the slab? 3. Comparative Study: Theoretical approach versus Experimental results Results – Conclusions Simulating the transverse prestress as an imposed strain, the punching capacity is hardly affected by the different prestress levels (1% deviation) and the compressive membrane force slightly changes, leading to the conclusion that the theoretical approach underestimates the prestress. In flexural mode the bending capacity is higher than the punching shear leading to the conclusion that the slab will fail in punching shear. The ultimate capacity of the interior panel is higher than the exterior but the displacement is smaller because the higher stiffness of the interior makes it stiffer and less ductile. Recommendations 1. Prestress should be simulated as a progressing action until the failure stage, not as a constant effect. 2. Effective stiffness in punching shear has to account for the boundary conditions. 3. Compressive membrane action should be defined separately from the ultimate punching shear capacity.