Performance of two-way hinges in reinforced concrete structures

Two-way hinges are frequently practiced in bridge columns aiming to avoid the transfer of bending moment to the foundation. The reduction of the concrete column section over a very small height portion is mainly sufficient to create a hinge like behavior. Currently, ACI Code proposes an amplification factor, limited to two, to account for the increasing of the hinge axial capacity due to the column confinement effect. The shear capacity of two-way hinges is defined as well by the shear friction theory imposed by the code. This paper presents a finite element analysis of two-way hinges to evaluate their behaviors. The experimental data were taken from a recent experimental investigation of two way hinges specimens subjected to axial load only. A numerical analysis was done using ABAQUS software. Based on the good convergence between the numerical and experimental results, a further analysis was conducted to investigate the hinge behavior under the simultaneous effect of axial and lateral loads. It was observed that the tri-axial stresses and confinement provided by the larger area strengthen the throat region, and the axial capacity of the hinge is amplified by a confinement factor equal to three. Furthermore, the confining stress produced by the column on the throat increased the hinge shear capacity more than what the code indicates.