Full-Depth Shear-Key Performance in Adjacent Prestressed-Beam Bridges

摘要

Bridge decks supported by adjacent precast/prestressed-concrete beams have becomeincreasingly popular in recent years due to their ease of consruction, shallow superstructure, and aesthetic appeal. In New York, such structures are built by placing a number of precast beams alongside one another and connecting them through grouted keyways called 'shear keys.' After the grout hardens, the beams are transversely post-tensioned and a composite, cast-in-place deck is poured over them. Before 1992, field inspection personnel frequently reported the appearance of longitudinal deck cracking over these partial-depth shear keys soon after construction. In response, a new system using full-depth shear keys with more transverse tendons was adopted in 1992. Since then, more than 100 such bridges have been built statewide. To evaluate their performance, a followup inspection survey was conducted in 1996 on 91 such bridges. Results indicate that frequency of shear-key-related deck cracking had been reduced significantly.