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The degradation of the connection between shear studs and concrete is a complicated phenomenon that depends on many factors, including; interfacial properties, concrete crushing and steel yielding. The purpose of this paper is to outline the scope and methodology of the research project being undertaken to characterise the shear stud-concrete interface of a composite beam using finite element analysis. A mesoscopic model will be created for a section of the interface. With the use of a multi-scale approach, the mesoscopic model will be incorporated into a global model. The influence of steel roughness and mechanical properties will be included. Concrete is to be modelled as heterogeneous, comprising discrete regions of aggregate, cement matrix, and an interfacial transition zone (ITZ). The effect of the ITZ will be taken into account using a zero thickness cohesive element. Experimental testing using a push-up rig is to be conducted to verify the numerical models. The ultimate aim is to develop a simplified representation of the shear stud-concrete interface that can be used in a large scale finite element model of a composite member to correctly capture the behaviour of the shear stud-concrete interface in the elastic and inelastic state.

A combined analytical/experimental cost effective approach to prediction of tensile and shear strengths of three dimensionally reinforced carbon/carbon composites is developed. Experimental studies and analysis for prediction of fiber failure statistics from yarn tests are described. It is shown that cumulative weakening failure of impregnated fiber bundles is the most likely cause of 3-D composite tensile failure in the principal directions. The analytical tensile strength model considers matrix failure in shear near fiber breaks, extension of shear cracks parallel to the broken fibers with increasing load, and the effect of post-failure shear transfer at the fiber matrix interface. The ineffective length (the effective yarn length for tensile strength calculations) is found to be high for carbon/carbons. Yield stress of carbon/carbons in shear is also predicted based on failure of degraded regions which are created by processing. Good correlation with experimental data is obtained and the effectiveness of the approach demonstrated. Possible ways of improving tensile and shear strengths are suggested.