Abstract
Overpass bridge girders are susceptible to impact damage of over-height vehicles, creating a traffic hazard and structural deficiency. The repair for a damaged girder has to meet adequate criteria for the safety, repair time and economy. This paper presents a case study for the repair of such an impact damaged concrete girder on the Lyndon B. Johnson Express construction project, located on I-635 and I-35 freeways in Dallas, Texas. The impact caused concrete loss and exposed several restressing strands on the exterior girder. The overpass had been completed while the old route was open below, causing a temporary vertical lower clearance than the final design, leading to the impact. The novel and innovative repair process involved fiber glass (GFRP) rebars, bonding epoxy and repair mortar. These rebars enhanced the flexural capacity of the repaired section and supplemented the mortar strength. Onsite load testing was employed to verify the performance of the repaired structure. Theoretical model of the composite girder before and after repair was employed. The strain data from the model compared well with the load testing data. The repair scheme drastically increased the stiffness of the damaged girder, resulting in about 50% reduction in the bottom strains. The beneficial effect of the repair resulted in large increases in the net compressive stresses (200–300%) at the girder bottom through the increase of the section stiffness and reduction of the gravity load stresses. Stresses remained well below the elastic range for concrete and the GFRP rebars.
Highlights
Damaged or under-strength concrete bridge repair and strengthening is an important issue, especially with the current poor state of the bridge infrastructure (ASCE 2013)
The use of GFRP rebars was motivated by its high resistance to corrosion and to reduce the aesthetic impact that could be caused by an external FRP wrapping on a new bridge
To compare the FINITE ELEMENT MODELING (FEM) strains to the average strains measured from load testing, the FEM strains from the closest nodes to each strain gage were used
Summary
Damaged or under-strength concrete bridge repair and strengthening is an important issue, especially with the current poor state of the bridge infrastructure (ASCE 2013). The deficiency could be due to fire, poor design or construction, time dependent deterioration, corrosion or impact of vehicles. One of the most common problems is the impact caused by over-height vehicles that exceed the posted clearance for a bridge. Johnson (LBJ) Express construction project in the greater Dallas, Texas, area experienced such a vehicle impact event. In 2011, a remodeling of 21 km length of the LBJ Freeway between I-35 and US-75 was initiated with a large number of bridges and overpasses. The overpass had been completed, while the old route was open below, causing a temporary vertical lower clearance than the final design leading to the impact and damage. The bridge has three spans in the north-south direction with different number of girders. The damaged girder was situated on the western edge on the middle span in the southbound direction, as shown
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
