Abstract
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.
Highlights
Composite steel and concrete bridges of medium spans with steel part constructed as a truss proved to be both economic and aesthetic
The elastic distribution of the longitudinal shear due to local effect of a concentrated longitudinal force introduced into concrete slab of a composite continuous girder due to prestressing was investigated in the late ninetieth (Johnson 1997; Johnson, Ivanov 2001)
The shear connectors were modelled as cantilevers sticking out from a member representing steel truss chord and pin connected at mid-plane of concrete slab substituted by a concrete strut (neglecting slab tension zone as recommended by Eurocode 4 (EN 1994-1-1 2004) for a shear connection analysis)
Summary
Composite steel and concrete bridges of medium spans with steel part constructed as a truss proved to be both economic and aesthetic. Concerning design of the shear connection between a steel truss and a concrete slab the common plastic redistribution as in standard plate girders was suggested, provided the shear connectors were sufficiently ductile. Detailed investigations of elastic distribution of the shear flow in the shear connection between a bridge steel truss and a concrete slab require vast parametric studies for which simplified 2D LA (linear elastic analysis) was proposed, verified and used. The shear connectors were modelled as cantilevers sticking out from a member representing steel truss chord and pin connected at mid-plane of concrete slab substituted by a concrete strut (neglecting slab tension zone as recommended by Eurocode 4 (EN 1994-1-1 2004) for a shear connection analysis) The verification of such simplification was studied for the first bridge shown in photos of Figure 1 with geometry according to Figure 6.
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