Evaluation of Repair Techniques for Impact-Damaged Prestressed Beams

About the report:

Collisions between over-height vehicles and bridges occur about 1,000 times per year in the United States. Collision damage to bridges can range from minor to catastrophic, potentially requiring repair or replacement of a bridge beam. For prestressed concrete beams, the traditional repair methods are prestressed strand splices and fiber-reinforced polymer (FRP) wraps. A new material, fabric-reinforced cementitious matrix (FRCM), has been developed as an alternative to traditional FRP wrap.

The first objective of this study was to damage, repair, and test four beams retrieved during the replacement of the overpass of Arcadia Road over I-81 at Arcadia, Virginia. The repair techniques evaluated were strand splices, FRP, FRCM, and a combination of FRCM and strand splices. The beams were tested in the lab in a simple-span configuration such that each repaired section was subject to uniform moment. Loads were monotonically increased to the point of beam failure. One beam was tested in an undamaged condition as a control.

Several methods were used to calculate strength and flexural behavior. Simple methods from AASHTO and ACI were used for hand-calculations of flexural strength. Conventional strain compatibility was also used. Non-linear beam models and non-linear three-dimensional finite element models were also investigated as tools to evaluate repaired beams. Material characterization was performed on the concrete, prestressing steel, splice chucks, FRP, and FRCM. The material characterization was used to develop the material models for the analyses.

It was found that the greatest percentage of original strength was returned by the FRP repair and the repair with the combination of FRCM and splice chucks. The lowest percent was returned by only splice chucks when 8 of 48 strands were severed and spliced. The FRCM proved to be a viable repair technique but should be tested in fatigue before deployment on a bridge with high volumes of truck traffic. The analysis methods were shown to provide good estimates of strength and load-deflection behavior.

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