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Longitudinal shear flow in the connection of a bridge steel truss upper chord and a concrete bridge slab is studied both in elastic and plastic stages of loading up to the shear connection collapse. First the distribution of the shear flow with an increasing level of loading is shown as resulted from 3D MNA (materially nonlinear analysis) using ANSYS software package and a former experimental verification. Nevertheless, the flow peaks in elastic stages above truss nodes due to local transfer of forces are crucial for design of the shear connection in bridges. Therefore a simple approximate 2D elastic frame modelling was suggested for subsequent extensive parametric studies. The study covers various loadings including the design loading of bridges and demonstrates importance of rigidity of the shear connec­tion, rigidity of an upper steel truss chord and rigidity of a concrete deck. Temperature effects and a creep of concrete are also studied. The substantial part of the study deals also with concentration of shear connectors in the area of steel truss nodes and influence of the connector densification on distribution of the longitudinal shear along an interface of the steel truss chord and the concrete deck. Eurocode 4 approach and quest to find an optimum design of the shear connection in composite bridge trusses are discussed. Finally the resulting recommendations for a practical design are presented.

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Design of composite steel and concrete truss girders is discussed, with an emphasis on longitudinal connection of the steel truss and a concrete slab. While a strongly non-uniform distribution of longitudinal shear due to localized force transfer in truss nodes occurs in elastic stages of early loadings, the plastic redistribution follows up to collapse. The former is of primary interest in the design of bridges, class 3 and 4 cross sections, non-ductile shear connection, and serviceability limit states in general. This research clears up the distribution in elastic phases and the process of plastic redistribution by using data of real bridge structures. Wide parametric studies provide insight into important parameters influencing the distribution, such as rigidities of shear connection, rigidities of steel chord and concrete slab, concentration of shear connectors above truss nodes, influence of temperature effects, shrinkage and creep. Design according to Eurocode 4 is discussed together with common procedures used by designers, referring to rather improper/conservative solutions. The necessity of densification of shear connectors above truss nodes is discussed in detail and suggestions for an iteration analysis for reasonable connection design is proposed.