Numerical assessment of effective width in steel-concrete composite box girder bridges with partial interaction

Abstract This present paper aims to analyze numerically, through the Abaqus® software, the influence of the interaction degree (partial or total) on the effective width of steel-concrete composite box girder bridges. These structures present advantages such as greater torsional rigidity, construction and maintenance benefits, durability and aesthetic appeal. In the case of steel-concrete composite beams for buildings, the use of partial interaction design is a common practice. However, dimensioning of bridges with partial interaction is a less used method and is not even recommended by some regulations. Due to this reason, the influence of the steel-concrete interaction degree is investigated to evaluate the behavior of the composite section with partial interaction, since the dimensioning in such conditions would offer economic advantages. For this purpose, the effective numerical width of 120 models of steel-concrete composite box girder bridges was determined, the study variables being the degree of steel-concrete interaction, configuration of the cross section, height of the concrete slab, length of the longitudinal span and arrangement of elements in the cross section. It was verified that the effective numerical width is directly proportional to the slab height and the longitudinal span’s length. Furthermore, the greater the steel-concrete interaction degree, the higher is the effective width observed. However, in most models, the interaction degree no longer significantly influenced the effective width from the 60% interaction, at which the numerical effective width remained practically constant. Based on the analyses performed, an expression was proposed to calculate an effective width adjustment coefficient depending on the interaction degree in the design of steel-concrete composite box girder bridges with partial interaction, in order to compensate for the non-consideration of the steel-concrete interaction’s degree in the standard procedures and adjust the recommendations of I-girders for box girders.