Structural behavior of link-slabs connecting simple-span precast girders

Abstract

ink-slabs provide continuity at the intermediate supports of multiple-span bridges with precast, prestressed girders. Current practice recommends debonding the link-slab from the precast girder ends to reduce its stiffness. Consequently, the link-slab moments are calculated based on a simplified design method where the end rotations of two adjacent girders will cause bending of the link-slab. Steel rebar in the link-slab is provided to resist these induced moments which are determined based on its flexural rigidity using the gross section property of the link-slab. Survey of bridges in the US indicated that it is common for link-slabs to develop full depth cracks in the center portion and therefore section properties of the central portion of the link-slab should be based on the cracked and not the gross section. The scope of this paper is to examine the structural behavior of the link-slabs and accurately idealize its deformed shape when debonded. Closed form solutions for the link-slab and precast girder bending moments are derived for this purpose. Data from a previous experimental and analytical study is used to show applicability and accuracy of these equations and for comparisons with current design procedures. It is shown that the forces induced in the link-slab based on current simplified procedures are overestimated. A proposed design method for link-slabs is finally proposed.