Numerical Modelling of Tensile Membrane Action in Reinforced Concrete Beams

Abstract

Conventional design practices for reinforced concrete (RC) beams primarily focus on ensuring adequate flexural capacity. However, the ultimate load-carrying capacity and deformation limits of these beams can be significantly enhanced through the development of membrane actions if sufficient lateral restraints are provided. Membrane actions include two distinct mechanisms: compressive membrane action (CMA) and tensile membrane action (TMA) or catenary action. CMA is activated sequentially after the flexural action, as deformations continue to increase. In this stage, the beam's lateral expansion is restrained, inducing compressive membrane forces that enhance the beam's load-bearing capacity. As the RC beams undergo large deformations, the compressive forces shift to tensile forces. At this certain point, TMA is activated, and the reinforcement bars become the loadcarrying mechanism for the RC beams. This thesis investigates the numerical modelling of TMA in RC beams subjected to increasing load at the middle joint of the beam under a static loading condition. An extensive literature review and analysis of previous experimental works were studied to gain insights into TMA. One of the prior experiments was selected to verify the results obtained from the Finite Element program ABAQUS and ensure its capability to accurately capture the TMA behaviour. In ABAQUS, beam and truss elements were used to model the concrete and reinforcing steel, respectively. Full interaction between concrete and reinforcement bars was assumed. Concrete damaged plasticity model was applied for the concrete, on the other hand, plasticity model was applied for the reinforcing steel. The results obtained from ABAQUS were compared with the reference experiment before performing a parametric study to explore various factors that could influence the development and behaviour of TMA, including horizontal stiffness, span-depth ratio, and other relevant parameters. In general, the numerical models demonstrated good agreement with the reference experiment in terms of the load-midspan deflection relationship. Once the numerical models were validated, parametric studies were conducted.