Evaluation of a Highway Bridge Constructed Using High Strength Lightweight Concrete Bridge Girders

Evaluation of a Highway Bridge Constructed Using High

Strength Lightweight Concrete Bridge Girders   
 Executive Summary
The use of high performance concretes to provide longer bridge spans has been limited due
to the capacity of existing infrastructure to handle the load of the girders during transportation.
The use of High Strength Lightweight Concrete (HSLW) can provide the same spans at a 20%
reduction in weight. This paper presents the findings from an ongoing performance evaluation
of HSLW concrete bridge girders used for the I-85 Ramp “B” Bridge crossing SR-34 in Coweta
County, Georgia,. The girders are AASHTO BT-54 cross-sections with a 107 feet 11½ inch
(32.9 m) length cast with a 10,000 psi (68.9 MPa) design strength HSLW mix and an actual
average unit weight of 120 lb/ft3
(1922 kg/m3
). The prestressing losses measured experimentally
by embedded vibrating wire strain gauges have been compared to the AASHTO LRFD loss
equations, as well as the proposed methods by Tadros (2003) and Shams (2000). The
investigation also included camber measurements and the effect of temperature changes. A load
test was performed on the girders at 56-days of age and on the bridge after completion of
construction to determine a stiffness estimator for use with the girders and to determine their
performance as a completed system. The girders are the first use of HSLW girders in the state of
Georgia, and they have proven to perform well for use in highway bridges.