Experimental and analytical assessment of prestressed concrete bridges damaged by overheight vehicle impact.

摘要

Due to frequent accidental damage to prestressed concrete (P/C) bridges caused by impact from overheight vehicles, a project was initiated to evaluate the strength and load distribution characteristics of damaged P/C bridges. A comprehensive literature review was conducted. It was concluded that only a few references pertain to the assessment and repair of damaged P/C beams.; Structural testing of two bridges was conducted in the field. The first bridge tested was the westbound (WB) I-680 bridge in Beebeetown, Iowa. This bridge had significant damage to the first and second beams. The second bridge, the adjacent eastbound (EB) structure, was used as a reference. The testing concluded that load redistribution was occurring in the WB bridge. Subsequent to these tests, the damaged beams in the WB bridge were replaced and the bridge retested. The repaired WB bridge behaved like the undamaged EB bridge indicating that the beam replacement restored the original live load distribution patterns.; Four isolated P/C beams were tested, two removed from the Beebeetown bridge and two from a large-scale bridge model tested by others. For the Beebeetown beams, Beam 1W was tested in an “as-removed” condition and Beam 2W was retrofit with carbon fiber reinforced polymer (CFRP) longitudinal plates and transverse stirrups. Beam 2W was 12% stronger than Beam 1W. Beams 1 and 2 from the bridge model were also tested. Beam 1 was not damaged while Beam 2 was damaged and repaired, again using CFRP plates. The retrofit beam attained a capacity greater than a theoretically undamaged beam prior to plate debonding.; Analytical models were created for the undamaged and damaged center spans of the WB bridge; stiffened plate and grillage models were used. Both models were accurate at predicting the deflections in the tested bridges and should be similarly accurate in modeling other P/C bridges. The moment fractions per beam were computed using both models. The damaged model indicates a significant decrease in moment in the damaged beams and a redistribution of load to the adjacent curb and rail as well as to the undamaged beam lines.