A Dynamic Approach for the Generalised Beam Theory

This thesis investigates the behaviour of steel and composite members in the framework of the Generalised Beam Theory. The proposed GBT approach falls within a category of cross-sectional analyses available in the literature for which a suitable set of deformation modes, including conventional, extension and shear, is determined from dynamic analyses. In particular, the deformation modes are obtained from the free dynamics of a planar frame model representing the cross-section with its plate segments placed at their midlines. This model is applied to the linear-elastic analysis of stiffened and unstiffened thin-walled members. The GBT formulation is extended to study the linear-elastic partial interaction behaviour of two-layered composite beams (e.g. steel-concrete composite beams). The novelty of this approach is to account for the relative movement of the slab with respect to the steel joist during the determination of the cross-sectional deformation modes. Several numerical examples are presented to highlight the ability of the proposed approach to capture the partial interaction behaviour of composite members. The accuracy of the results are validated against those obtained from shell finite elements models developed in ABAQUS. The instability behaviour of thin-walled members is studied in the context of GBT. The member analysis is carried out in two stages, firstly a pre-buckling analysis is performed to determine the stress distribution in the pre-buckled configuration followed by a bifurcation analysis conducted to determine the buckling loads and modes. The composite beam formulation with partial interaction is extended to study the time-dependent behaviour of composite steel-concrete beams accounting for creep and shrinkage of the concrete. The time analysis, implemented using the Step-by-Step Method (SSM) with a new set of deformation modes calculated at each time step, is carried out to determine the short- and long-term response of the composite beams

A GBT Model for the Analysis of Composite Steel-Concrete Beams with Partial Shear Interaction

Composite steel\u2013concrete beams represent an efficient form of construction for building and bridge applications. In this structural arrangement, the composite action is provided by means of a shear connection placed at the interface between the steel beam and the concrete slab, and this is commonly specified in the form of shear connectors. In this system, the structural rigidity is dependent on the deformability of the shear connection and this kinematic condition is usually referred to as partial shear interaction. In this context, this paper presents a theoretical model to study the partial shear interaction behaviour of composite steel\u2013concrete beams in the framework of GBT. The effects of longitudinal slip between the concrete slab and steel beam are accounted for by taking into account the deformability of shear connectors during the evaluation of the warping components of the deformation modes. The proposed approach falls within a category of cross-sectional analyses available in the literature for which a suitable set of deformation modes, including conventional, extension and shear modes, is chosen from dynamic analyses. This method is applicable to open, closed and partially-closed cross-sections with one or more shear connections. A numerical example of a composite bridge is presented, with the results validated against those obtained from a shell finite element model developed in ABAQUS/Standard. The effect of different finite elements used in the GBT cross-sectional analysis is considered, in particularly highlighting how they influence the stress distributions induced in the composite section