The Effect of Transverse Strand Extensions on the Behavior of Precast Prestressed Panel Bridges

A series of static and dynamic loading tests was conducted on a full-scale bridge specimen constructed using prestressed precast panels placed on top of prestressed precast girders and covered with a cast-in-place bridge deck. The north half had panels with transverse prestressing strands extending beyond the panel edges, and the south half had smooth-sided panels.

The major objective was to determine if the absence of strand extensions would cause significant deterioration in performance under fatigue and static loading. The bridge was subjected to four static tests (three at levels high enough to cause girder cracking) and two fatigue tests. In addition, ten concentrated load tests were made. All loadings were applied equally to each half of the bridge.

Four major conclusions are apparent from this study:
(1) The overall and local behavior of bridges without extensions is as satisfactory as that of bridges with extensions;
(2) In some cases, prestressed girders can be cracked flexurally and subjected to extensive fatigue cycling without strand fracture;
(3)Bridge deck capacity under concentrated loads should be investigated using yield-line models as well as punching shear models, particularly in overhang areas; and
(4) Construction details were not observed to affect overall performance.
However, they can habe significant effects of local behavior.