Repair and Rehabilitation of Cracked Concrete Piers Using Post-Tensioned CFRP Rods: 8th Avenue Viaduct Case Study

摘要

8th Avenue Viaduct is located in Denver, CO and is 2372 feet long. It has multiple vertical and horizontal curves. Combined with the temperature effects, this has resulted in cracking both vertically and horizontally on all 18 of the concrete hammerhead piers supporting the bridge. Inspections revealed that the cracks have expanded over the years. A 3D Finite Element Model of the bridge using ANSYS Mechanical APDL was built and calibrated using strain gages and thermo sensors installed on the bridge in order to understand its behavior under dead, live and temperature loads. Using the same software, a separate model of one of the piers was also constructed, which included the pier reinforcement, as well as the non-linear properties of concrete, allowing for accurate cracking simulation. The forces obtained from the general bridge model were applied onto the pier model and the resulting cracks were compared and found to match favorably with the cracking that had physically occurred on the pier. A rehabilitation system of post-tensioned CFRP rods was proposed and tested on the model, and was found to be very effective. After analyzing several different methods of applying the CFRP rods to the piers and comparing them in terms of cost, constructability and maintenance, the best and most effective method of application was determined to be grouting the rods into the concrete surface of the piers, using epoxy to transfer the post-tension force. The author recommends this repair be used for all the piers of the Viaduct.