Investigation of engineering issues in bridge widening

A common practice of widening bridges is to construct a new bridge deck by the side of the existing bridge deck and cast an in situ concrete stitch (also called stitching slab) between the existing and the new decks to provide a monolithic connection and a continuous riding surface. In this paper, engineering issues concerning bridge widening are addressed. Finite element method related grillage theory is used to investigate the effect of shrinkage and creep differences between existing and news bridge decks on the internal forces of the structures. The influence of settlement in the substructure of new bridges on widening structures is also investigated. Possible improvement of concrete materials used for connection of existing and new bridge decks is discussed. As a result, it is suggested that the connection time interval between existing and new bridge decks should be as long as possible to minimize the shrinkage and creep effect. Some feasible measures to enhance the integrity of the widened bridge are also proposed.