Nonlinear finite element analysis of deep reinforced concrete coupling beams

A finite element method for analysing the nonlinear behaviour of reinforced concrete structures that accounts for cracking and compression-softening of the concrete and dowel action and confining effect of the reinforcing bars has been developed by the second and third authors. It was applied in this project to study the load–deflection behaviour and failure characteristics of deep reinforced concrete coupling beams by analysing the models previously tested by the first and second authors and using it to conduct a parametric study on the effects of varying the shear reinforcement and restraining the axial elongation of the coupling beams. The analysis showed good agreement between the theoretical and experimental results and revealed that deep coupling beams behave quite differently from ordinary beams; after cracking, a deep coupling beam behaves more like a truss with a diagonal concrete strut which rotates and causes axial elongation. On the other hand, the parametric study revealed that although adding more shear reinforcement could suppress shear-tension failure, it would cause shear-sliding failure at the beam–wall joints and that although restraining the axial elongation could increase the shear capacity, it would at the end lead to a more brittle failure.