Comparison of Strands and Bars for Positive Moment Connection of Continuous Precast Concrete Bulb-Tee Girders

Abstract

There are a number of benefits associated with making single-span precast concrete girders behave as continuous members. A simple connection to cause this behavior uses the longitudinal steel in the deck to resist the negative moment in the girders at the support. Any positive moment at the support caused by secondary effects is resisted by either strand or bars extended from the ends of the girders and cast within a continuity diaphragm. This paper compares the performance of 2 different connections, used in the positive-moment region of full-depth, 45-inch-deep precast concrete bulb-tee (PCBT) girders. The 2 connections use extended, 1/2-in.-diameter prestressing strands bent at 90 deg. and extended No. 6 reinforcing bars bent at 180 deg., cast into a continuity diaphragm. A conventionally reinforced concrete deck was applied to the tops of the girders. Both 2-span systems were tested to determine their initial positive cracking moments, the integrity of the connections under cyclic loads, and their ultimate positive moment capacities. When subjected to similar loading conditions, the connection made with the mild reinforcing bars performed better than that made with prestressing strand.