This paper reviews and demonstrates the age-adjusted concrete modulus approach to the time-dependent analysis of spliced precast concrete girder composite bridges. The method is illustrated by example of one of the post-tensioned spliced girder bridges built during the recently completed 1-15 Reconstruction Project in Salt Lake City, Utah.Sixteen simple-span bridges up to 67 m (220 ft) in span length were constructed using a 2400 mm (94.5 in.) deep modified girder developed by the Washington State Department of Transportation. With a more accurate method for prestress loss calculations for such bridges, designers can take advantage of the higher concrete age at time of post-tensioning and the resultant reduction in creep and shrinkage strains.
