Shoring Substitution of Loaded Plate Girders Using Wing Plates

This paper addresses the challenges of repairing plate girders of the bents supporting New York City Transit (NYCT) subway connecting Manhattan to Queens at the 61st street station in Woodside. These bents span above Roosevelt Ave. with no room for shoring. Repairs also cannot interrupt train operations on more than one track at a time. These conditions require a different way of performing repairs. In this paper, an innovative approach for repairing these girders is discussed. Traditional methods for railway bridge girder repairs, designed using ASD AREMA, often require jacking the structure to unload it before replacing its flanges. The proposed method involves the installation of temporary wing plates along the member web to receive the chord load from the girder top flange plates. These wing plates increase the girder section modulus and limit the stress increase in the girder when the top plates are temporarily removed. The girders are analyzed under all construction phases to ensure that the stress ratios in all elements comply with AREMA allowable stress limits at each stage of analysis. The load transfer to and from these plates is addressed at every stage of analysis. The deteriorated section is evaluated under temporary loads during track outages. Strengthening of bottom flanges, which does not require flange replacement, is performed first, followed by the addition of the temporary wing plates. Once the temporary wing plates are installed, deteriorated top cover plates are replaced. After ensuring that the structure is adequately reinforced, the wing plates are removed. Finally, the repaired section is assessed under the final load conditions with all tracks in operation. The process of replacing existing rivets with new bolts for top flange plates is covered in this paper. Fastener replacements are done in a manner that avoids buckling of top compression flange cover plates during the temporary removal of the fasteners. This paper also addresses the attachment of the bottom flange strengthening plates to existing girders and discusses the challenges of slip-critical connections to corroded steel. This paper provides insights into a practical and less disruptive method for structural repairs in active rail environments. This approach not only reduces downtime and maintains service continuity but also offers a robust solution that can be adapted to similar structural challenges. The innovative use of temporary wing plates instead of shoring girders enhances the experience of engineers, providing them with a new tool to tackle complex repair projects.