PRACTICES FOR PIER AND INTERMEDIATE DIAPHRAGMS OF PRECAST CONCRETE GIRDER BRIDGES

The objective of this study is to provide optimal standard pier and intermediate diaphragm details for the State of Maryland to make simple span pre-cast concrete girders continuous for live load and lateral stability. The study is based partially on a survey prepared and sent to the Departments of Transportation of all 50 states requesting their standard detail drawings of diaphragms over piers. Thirty-three states replied, sending their various approaches to continuity over piers. Based on the survey, a standard detail for a concrete diaphragm over pier is designed, accounting for the negative and positive moments. The choice of such a diaphragm type is based on factors such as economy, constructibility, and the use of the post-tensioned tendons and steel reinforcement to resist positive moment induced by creep, shrinkage, and elastic shortening. Also, along with the survey, some of the states replied with the type and placement of intermediate diaphragms. A spreadsheet was developed for all the types of AASHTO and Bulb-Tee girders with different span lengths that were cited in the states ’ replies