Study On Concrete Stitch Of Widening Bridge Under Traffic Load

With the development of economy of our country in recent years, many highways need to be widened and reconstructed to satisfy the traffic increase. In the widening of highway bridge projects, traffic flow has to be maintained on the existing bridges, avoiding the widening brings the inconvenience to economy and society. As a result, the existing bridge deck needs to endure the continuous traffic loads. The existing and the new bridge decks are often connected by concrete stitches. The traffic-induced vibration transfers to the fresh concrete stitch and may destroy the concrete stitch. It is generally believed that the damage is mainly caused by contraflexural curvature as a result of the vertical deflection. If we do not take measures to reduce the contraflexural curvature, the contraflexural curvature will exceed the threshold curvature which causing the concrete stitch damage and infecting the comfort and safety of the bridge.This paper reviews practice and methods of bridge widening in our country and foreign countries, mainly studies the concrete stitches under traffic loads.Based on the widening projects of Beijing-Tianjin freeway, this paper analyze the prestressed concrete T girder bridge using the grillage analysis method, mainly focuses on the deformation of the concrete stitch in the highway bridges widening. Several methods to mitigate the traffic loads effect on concrete stitches are studied, and some recommendations are suggested. Those recommendations include traffic restriction, provision of temporary shear connection, provision of temporary bracing, segmental construction of concrete stitching and their different combinations.