Cracking control technique for continuous steel-concrete composite girders under negative bending moment

Abstract

Continuous steel-concrete composite girder can fully utilize material strength and possess large spanning ability for bridge constructions. However, the weak cracking resistance at the negative bending moment region of the girder seriously harms its durability and serviceability. This paper investigates practical techniques to improve the cracking performance of continuous steel-concrete composite girders subjected to hogging moment. A real continuous girder was selected as the background bridge and introduced for numerical analysis. Modeling results show that under the serviceability limit state, the principle stress of concrete slabs near the middle piers of the bridge was far beyond the allowable material strength, producing a maximum tensile stress of 10.0 MPa. Approaches for strengthening concrete decks at the negative moment region were developed and the effectiveness of each approach was assessed by examing the tensile stress in the slabs. Results indicate that the temporary counterweight approach decreased the maximum tensile stress in concrete slabs by 22%. Due to concrete shrinkage and creep, more than 65% of the prestressed compressive stresses in concrete slabs were finally dispersed to the steel beams. A thin ultra-high performance concrete (UHPC) overlay at the hogging moment region effectively increased the cracking resistance of the slabs, and practical engineering results convicted the applicability of the UHPC technique.

Mechanical behavior improving study of concrete deck of main beam at pylon root of composite beam cable-stayed bridge

“…A steel-concrete composite beam bridge is composed of steel beams and concrete bridge deck, which are combined by shear connectors. This kind of structure makes full use of the tensile properties of steel and the compressive performance of concrete, and it is more suitable for large-span bridge structures because it has many advantages such as high stiffness, short construction period, and good economic benefits [1,2]. However, in the negative bending moment zone, the concrete bridge deck is subjected to tensile stress, and the steel beam is subjected to compressive stress, which is an unfavorable stress state for the steel-concrete composite beam structure.…”