Modified Fiber Reinforced Concrete Repairs for Corroded Steel Beam Ends

About the report:

One common form of costly bridge maintenance is repairing corroded steel beam ends under leaking joints. Recently, the University of Connecticut and the Connecticut Department of Transportation have developed a practical repair strategy in which shear studs are welded to undamaged sections of the corroded steel beam and then ultra-high-performance concrete (UHPC) is cast around the corroded steel beam end. The purpose of this project was to evaluate how UHPC repairs on steel beam ends can be modified to make the beam ends easier to construct in the field, either by Virginia Department of Transportation (VDOT) work crews or by contractors. The two modifications that this project focused on included using other types of fiber reinforced concretes (FRCs) in place of UHPC and using threaded rods instead of shear studs to transfer load from the steel beam to the FRC panels.

A literature review showed that very high-performance concrete and engineered cementitious composite have the necessary strengths for FRC beam end repairs and offer convenience, availability, and cost savings advantages compared with UHPC. Threaded rods were also found to have sufficient strength, ductility, and fatigue resistance to be used in FRC beam end repairs. They offer ease of installation, worker and environmental safety, and cost savings advantages compared with welded shear studs.

Small-scale durability testing showed that applying a caulking or epoxy coating to the edge interface between the steel and hardened FRC can prevent saltwater moisture penetration into this edge interface, increasing the durability of this repair type. Existing chlorides should still be removed from the steel surface before casting FRC.

Two VDOT districts conducted a mockup and initial implementation of these repairs. These field trials displayed the importance of viscosity, fiber dispersion, and aggregate gradation on the pumpability and workability of the FRC mixture, ensuring durability and structural integrity of the repair. Partial-depth FRC repairs can eliminate the need for coring through the bridge deck and using polyvinyl chloride, or PVC, distribution systems to deliver FRC to the formwork. Pumps can be necessary if hand delivering FRC to the partial-depth repairs is not feasible. Therefore, the decision to use partial- versus full-depth repairs is application specific.

A cost analysis showed that if FRC beam end repairs are widely implemented, they can save VDOT approximately $39 million per year on steel beam end repairs. These cost savings could be reallocated to other bridge repair or maintenance actions.

The study concluded that other FRCs, such as very high-performance concrete and engineered cementitious composite, and threaded rods can be used in FRC beam end repairs as a modification to the UHPC repair method the University of Connecticut and Connecticut DOT developed. Based on this conclusion, the Virginia Transportation Research Council recommends that the VDOT Structure and Bridge Division implement guidance for using FRC beam end repairs into the VDOT Manual of the Structure and Bridge Division. The benefits to using FRC repairs include cost savings, easier installation for VDOT work crews and contractors, and better durability than traditional repairs.

Supplemental materials can be found at https://library.vdot.virginia.gov/vtrc/supplements

_{Disclaimer Statement:The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.}

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