EVALUATION AND REPAIR OF IMPACT-DAMAGED PRESTRESSED CONCRETE BRIDGE GIRDERS

Impact damage of prestressed concrete bridge girders was studied through field inspections and laboratory tests of a damaged girder. Nondestructive techniques for evaluating the extent of damage and the quality of repairs were examined. Various materials and procedures for repairing damage to the concrete and the strands were considered. A prestressed concrete bridge girder, damaged by impact from an overheight vehicle, was removed from a bridge in Austin, Texas. The damaged girder was transported to the laboratory for evaluation and repair. Several nondestructive methods were studied to evaluate the effectiveness of each in assessing the extent of concrete damage resulting from overheight vehicle impact. The surface hardness of the damaged girder was measured using a rebound hammer. Impact echo and spectral analysis of surface waves techniques were used to assess the extent of damage. All three methods were also used to evaluate the effectiveness of the concrete repairs that were undertaken. Several classes of premanufactured patch materials were used to repair the damaged concrete girder. Materials consisted of cast-in-place concrete and hand-applied mortars. Cast-in-place materials were either magnesium-phosphate based or portland-cement based. The mortars were either latex-modified or fiber-reinforced, silica fume modified. Preload was applied to the girder, the damaged concrete was replaced and allowed to cure, and the preload was removed. Static loads were applied to investigate the flexural characteristics of the repaired girder. Internal prestressing strand splice techniques were used to repair intentionally damaged strands of the same prestressed girder. Four different types of splice hardware were installed and evaluated. Each splice was tested to failure separately in a test machine to evaluate the strength and critical components of each assembly. Finally, the results were used to suggest a procedure for rapid initial assessment of damage. The procedure should allow field personnel to distinguish between various types and locations of impact damage and to determine the course of action to be taken regarding the evaluation, repair, or replacement of an impact-damaged girder.