An experimental study on joint performance of steel I-girders connected to inverted-T bent cap in fatigue testing

Abstract

Traditional steel girder bridges are perceived to detract from the aesthetics of urban design because of the excessive volume of the bent cap. These bridges have additional construction and maintenance costs associated with the installation of supports. In this paper, a new bridge system is proposed to overcome these disadvantages. In this system, the composite behavior of the joint is key to ensuring proper structural performance. The main feature of the proposed bridge system is the construction of steel I-girders and inverted-T bent caps at the same elevation. Two methods for connecting steel girders and bent caps were investigated, namely, the introduction of pre-stressing forces and the installation of steel plates. To assess the composite performance of the proposed methods, up to two million fatigue test cycles were performed on full-scale test girders. The key parameters examined were the girder displacement; the relative joint displacement; the strain in the girder, steel plate, and reinforcement; and the crack patterns in the concrete. The test girders behaved stably, without a significant decline in performance at the joint, after elimination of the prestressing bar. However, use of a pre-stressing bar reduced tensile stress during fatigue testing and was highly effective in controlling cracks.