Recommendations for Design of Concentrically Pretensioned, Precast Concrete Bent Caps

Abstract

Precast, prestressed bent caps are an attractive design option because they permit accelerated bridge construction and can extend the service life of bridges by reducing or eliminating the service-level cracking observed in RC bent caps. A design procedure is recommended for the flexural design of pretensioned bent caps in which the amount of prestressing is selected to ensure zero tension at service, with service- and strength-limit states serving as checks on the design. Recommendations include how to account for openings for connections that may influence the bent cap performance. Using the recommended flexural design procedure and AASHTO shear design provisions, pretensioned bent caps were designed for a suite of multicolumn bridges. The flexural design procedure is shown to be efficient for the design of most bridges, and many bent caps are expected to have only minor cracking, if any, at ultimate demands. The minimum area of transverse reinforcement was found to govern most bridge designs, leading to recommendations to use the general, noniterative sectional shear design method. The resulting designs lead to recommendations for how designers and contractors can use precast, pretensioned bent caps not only to enable accelerated construction and extend bridge service life but also to increase design and construction efficiency.