Director

post-tensioned concrete segmental box girder bridges. The bridges, made of precast segments, were erected by the balanced cantilever method of con-struction using a launching truss sys-tern. ' This application of the launching truss for bridge erection was the first in the United States.2 In the balanced cantilever method of construction, bridge segments undergo different Stress conditions during and after construction. Therefore, the bridge design has to include every con-struction event that results in signifi-cant stress changes. In addition, the time-dependent effects of creep, shrinkage, and temperature must be taken into account. Verification of design assumptions using measured data is needed and is essential to the successful prediction of long-term bridge deformations. There-fore, an investigation to obtain field data on an existing bridge was made to verify analytical and design procedures for predicting time-dependent behavior of post-tensioned box girder bridges. The investigation comprised three parts: 1. Field measurements on Kishwau-kee River Bridge. 2. Laboratory measurements of con-crete used in the bridge. 3. Comparisons between field mea-surements and calculated defor-mations. Field measurements included lon-gitudinal concrete strains, vertical de-flections, and temperatures of three bridge segments. Initial readings were taken as soon as possible after place-ment of concrete. Readings presented a detailed record of bridge behavior over a period of5 years