Steel-concrete composite bridges with twin-I steel girders and prefabricated slabs constitute an economical and competitive solution for small and medium bridge spans. In recent years they have started to gain their share in the construction market. However, the current slab-to-girder connection with groups of headed shear stud connectors is not well adapted for prefabrication and fast erection, and does not respond successfully to the durability of the construction. New types of connections by adhesion, interlocking and friction constitute a conception that aims to answer these demands. The resistance of these connections is based on the development of longitudinal shear stresses in the interfaces which form the connection. The goals of this study are to complete the existing research in this field by proposing scientific tools in order to predict the connection's structural performance, i.e. prediction of the connection's ultimate resistance and deformation capacity, including the post-failure behaviour. In addition, the behaviour of the connection under cyclic loading is also investigated to assess the connection's resistance to fatigue and to propose a design method for composite bridges under fatigue loading. To fulfill theses goals a combinational methodology was applied which included: study of the state of the art: a) in composite bridges so as to define the requirements and b) in interface behaviour in order to emphasize the parameters which are responsible for the resistance and obtain information for the nature of cyclic loading damage mechanisms, experimental investigations: a) to reveal the laws describing the interfaces and the connection's behaviour for static and cyclic loading, and provide data for development of analytical expressions and model validation and b) demonstrate the capacity of a composite beam under cyclic loading and the extent of its remaining resistance at ultimate limit state, analytical studies: a) to produce the laws describing the interface behaviour under static and cyclic loading and b) to evaluate the impact of the cyclic loading to the slip in the interfaces and in the connection and thus propose a damage factor for cyclic loading, finite element analysis in order to enable an analytical description of the confinement effect, caused by the reinforced concrete slab, which contributes to the resistance, the development of a numerical model to predict the connection's structural performance and to propose a design method for composite bridges fabricated with the new connection. Application of the mentioned methodology resulted in several useful conclusions: The interface behaviour can be described by analytical laws. The post failure behaviour of the interfaces was explained by accounting for the kinematics of the failed surface and basic notions of fracture mechanics. The damage due to cyclic loading on the interfaces and on the connection is expressed by the accumulation of a residual slip. Provided that the shear stresses remain lower than an elastic limit and the accumulated slip does not exceed the failure slip for static loading, fatigue failure is avoided. The confinement effect was incorporated, analytically, together with the laws of the interface behaviour in a numerical model to predict the connection's structural performance and allow a parametrical study. A design method for the verification of composite beams under static and cyclic loading was developed.
EPFL2012
