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The research presented in this thesis is concerned with the time-dependent creep and shrinkage behaviour of steel-concrete composite curved beams with partial interaction. The research program comprises both theoretical studies and experimental investigations. Firstly, an efficient numerical method is developed for the creep and shrinkage analysis of steel-concrete composite beams curved in-plan. The flexibility of the shear connection in the radial and tangential directions at the steel-concrete interface is taken into account in the developed method. The creep and shrinkage effects of the concrete deck are considered by using the analytic Age-adjusted Effective Modulus Method. The accuracy and efficiency of the proposed approach are validated by comparing its results with available experimental results reported in the literature and with those based on an ABAQUS shell finite element model. Parametric studies are also undertaken, which demonstrate that the initial curvature and partial interaction of the beam have significant influences on the time-dependent behaviour of composite beams curved in-plan. The geometrically nonlinear time-dependent creep and shrinkage behaviour of horizontally-curved steel-concrete composite beams with partial interaction is also investigated. In order to include the effects of geometric nonlinearity, a step-by-step iterative procedure is used for the creep and shrinkage analysis. The examples presented illustrate that the geometric nonlinearity should be considered for an accurate time-dependent analysis of composite beams curved in-plan. The experimental program, which involves testing the time-dependent behaviour of a simply-supported steel-concrete composite beam that is curved in-plan, is reported. The experimental results provide benchmark data to test the validity of the theoretical model developed for the time-dependent creep and shrinkage analysis of curved composite beams, and for subsequent studies by other researchers. Finally, a numerical formulation for the nonlinear time-dependent creep and shrinkage analysis of spatially-curved steel-concrete composite beams with partial interaction is also developed. The verifications indicate that the proposed formulation for the time-dependent analysis of composite beams curved in-space is accurate. The effects of partial interaction, initial curvature and the curvature components are also illustrated with chosen examples to elucidate this complex structural behaviour.

This thesis presents the nonlinear in-plane behaviour of circular fixed arches subjected to thermal loading only. Due to the nonlinear prebuckling behaviour of arches and its effects, classical buckling theory which is founded on geometric prebuckling linearity can not predict the in-plane buckling of arches accurately. Based on a nonlinear formulation of the strain and displacement relationship and considering constant thermal distributions only, virtual work formulations are used to establish the differential equations of in-plane equilibrium and the statical boundary conditions, from which the nonlinear equilibrium equations are derived in closed form and which are suitable to use in design. By considering the adjacent buckled configurations, the differential buckling equilibrium equations are formulated from the principle of virtual work as well, and the analytical solutions for the nonlinear buckling of fixed arches are obtained. It is shown that nonlinear elastic buckling of a fixed in the plane of it curvature can not occur when it is subjected to thermal loading only, except if the arch is as a straight column. By using the algebraic representation of nonlinear in-plane equilibrium derived in this thesis, the elastic response of fixed arches at elevated temperatures and the attainment of first yield are examined in detail. The arch deflects transversely without bound in the elastic range at elevated temperatures, whereas it will yield first at the top extreme fibre of the cross section at the supports when a critical temperature is reached. The influence of several parameters such as the included angle is also considered. Based on the models of stress distributions at cross sections, the spread of yield both through the cross section and along the length of the arch is studied. It is indicated that the progress of yielding causes the first two hinges to form at the supports of the fixed arches, and then moment redistribution leads to the generation of the third hinge at the crown with an increase of temperature. Thus nonlinear plastic hinge analysis can be applied to the arch analysis under thermal loading.