Experimental Study on Pre-stressed Concrete Box Beams from a Decommissioned Bridge Strengthened with Carbon Fiber Reinforced Polymer Anchors and Laminates

Graduate Student: Sina Yousefian

Principal Investigator: Andreas Stavridis

Project Completion Date: 2023

Three 57-ft long beams were obtained during the demolition of a bridge in Buffalo, NY. The bottom surface of the beams was prepared for the application of the CFRP retrofit. Besides cleaning, the surface preparation involved patching of cavities with epoxy, and grinding to increase the roughness according to Technical Guideline No 310.2 of the International Concrete Repair Institute. Holes were also drilled to allow the installation of the CFRP anchors. The anchor layout, as well as the laminate thickness, varied between the three specimens to investigate their effect on the structural performance. All beams were tested under service loads before being retrofitted to evaluate their structural condition prior to the retrofit application. Once strengthened, they were tested to failure with a four-point bending test set up using two 440-kip actuators.

This research provided much needed data for the behavior of deteriorated beams retrofitted with CFRP laminates and anchors. The tests on the beams obtained from an actual bridge after 37 years of service indicate the feasibility and effectiveness of the retrofit scheme. They also demonstrate that differences in the retrofit, i.e. the laminate thickness and the anchor distribution can lead to drastically different failure patterns. However, in all cases the retrofit scheme increased the stiffness, and mainly the strength and ductility of the beams. The increase in strength and ductility was larger after the application of smaller thickness of FRP laminates.

This project was sponsored by the New York State Department of Transportation.