Experimental and theoretical studies on confined steel concrete composite beams under combined bending and torsion

Abstract

The thesis is concerned with the Ultimate Strength and Behaviour of a new type of composite beam called Confined Steel Concrete Composite Beam subjected to combined bending and torsion. A concrete beam with a small quantity of reinforcement is shuttered with cold formed steel sheet confines the concrete on three sides of the beam and acts as a formwork during construction and positive reinforcement after the concrete gets hardened. Shear connectors in the form of headed studs are provided to have bond between the concrete and the sheet. In addition, these beams are welded with braces in pure bending region at top face of the beam to avoid separation of sheet from concrete during loading. This type of beam is referred here as Confined Steel Concrete Composite Beam (CSCC BEAM). In the experimental phase, thirty two CSCC beams are tested and the entire behaviour of the beams are monitored to predict the physical response of the beams under three different types loading such as pure bending, pure torsion and combined bending and torsion. The deformation criteria (deflection, curvature, rotation and angle of twist) are also included in the investigation throughout the entire load history. Based on the physical response of the system, an analysis is carried out to formulate the ultimate strength of the beam under combined loading using the equilibrium and compatibility conditions in the analytical phase. The analysis permits the prediction of ultimate strength of the beam under combined loading. A comparison is made with the results obtained by the analysis and experimental values which are found to be in good agreement. Finite element models are also developed using ANSYS to compare the results from mathematical equations and laboratory results. Excellent similarity was also observed from the models. Further research areas are also identified and outlined in order to formulate a design methodology and design charts which contributes to add a practical significance of this research.