Composite beams : reliability and longitudinal shear resistance with profiled sheeting

Abstract

In this thesis, two problems have been studied: one is the reliability of design resistances of composite beams in bending, the other is the longitudinal shear resistances in concrete flanges of composite beams with profiled sheeting. For the first problem, a general theory is developed based on the concepts of safety-index and second-moment reliability, to analyse the reliability of a design resistance for composite structures. This theory consists of two basic parts: one is the determination of several distinct safety factors for a single resistance function, with respect to the specified safety level; the other is the assessment of safety level, corresponding to given safety factors. Application of this theory is related to the relevant test results. In the scope of Eurocode 4, this theory is particularly used to calibrate safety factors employed for design plastic bending resistances of composite beams. From the calculation based on 122 test results, the reliability of using the Eurocode provisions, including the recommended safety factors and the theoretical models, is judged for bending resistances of beams with full and partial shear connection. In studying the longitudinal shear resistances in concrete flanges of composite beams with and without profiled sheeting, a simple theory to determine the resistances is established. This theory is based on the "friction-cohesion" and "concrete strut" models for concrete in shear and takes the effect of profiled sheeting into account. Associated with the theoretical work, seven tests on three specimens for investigating the longitudinal shear resistances are reported. From both experimental results and theoretical calculation, the behaviour of the test specimens is studied, and, finally, new design recommendations are made to predict the longitudinal shear resistances of the composite beams