Generalized Beam Theory deformation modes for steel–concrete composite bridge decks including shear connection flexibility

This paper proposes a procedure to calculate cross-section deformation modes for steel–concrete composite bridge cross-sections, including shear connection flexibility, within the framework of the Generalized Beam Theory (GBT). The proposed procedure is computationally efficient and makes it possible to (i) handle arbitrary (flat-walled) composite cross-sections, including complex configurations with several closed cells, (ii) consider the geometric offset between the steel and concrete mid-lines, which is essential in steel–concrete composite members, and (iii) automatically identify, separate, and hierarchize the deformation modes into physically meaningful sets, including a set of shear connection slip deformation modes. For illustrative purposes, the various deformation mode sets are determined for two representative cross-sections, namely a twin-girder and a box-girder with closed longitudinal stiffeners. These deformation modes are then employed to perform the structural analysis of simply supported decks, showing that very accurate results are obtained with a small number of deformation modes and that the modal decomposition of the solution provides in-depth insight regarding the bridge structural behavior.