Joint stiffness and design bending moment of composite deck slabs in highway bridges

In the construction of composite deck slabs, it is necessary to join two adjacent blocked bottom plates to form one united plate in the longitudinal direction. In this paper, three types of longitudinal joint for Robinson-type composite deck slabs are proposed, and static and fatigue tests carried out by using beam specimens are described. The paper also reports the design bending moment for jointed slabs with span length of 2 to 8 m by using FEM analysis. The results of the tests and analysis are summarized as follows: The joint stiffness of the reinforced joint structures El and E2 is clearly improved. The separation at the joint between two plates considerably decreases, thus reducing the stress in the bolts of the joint. The failure mode of test beams is fatigue failure of the steel plate or high-strength bolts. This is in contrast to the bending crush of concrete in the compressive zone for static tests. New design bending moments which consider the orthotropic plate of the slab with joint are proposed on the basis of three-dimensional FEM analysis.