Norfolk Southern (NS) Railway operates an east/west line through suburban Philadelphia, Pennsylvania. Bridge MV 25.13 is a seven-cell stone arch structure that has been in service for approximately 150 years. Several different rehabilitation efforts have been employed over the life of the bridge. The latest project, reline/reinforcement of the arches, resulted from field observations by the site contractor W.M. Brode Company of Newcomerstown, Ohio, who was employed to perform conventional repairs on the bridge. The contractor observed some severely deteriorated areas that included fractures in the load carrying stone. They advised NS that the conditions were beyond the scope of the proposed repair methods they were asked to use on the bridge.
NS retained Jacobs Engineer’s Chicago, Illinois office to further investigate the conditions. Jacobs agreed with the contractor and recommended a more robust repair procedure be investigated. Jacobs then conducted a feasibility study. The challenge in this case, was to find a method and/or product that would be able to repair and reinforce the 50’ span, single radius arches yet allow the rail line to remain in operation while the repairs were made.
Jacobs concluded that 4 of the 7 cells would require the additional work to avoid further deterioration and possible track closure. The feasibility study found the most cost-effective method was to slip line the arches with corrugated structural plate.
Contech Engineered Solutions was approached by Jacobs, due to the success Contech has had with similar applications. After evaluating the existing conditions, Contech recommended its BridgeCor® structural plate product for the reline of the existing culvert arches. BridgeCor is a deep corrugation (15” x 5 ½”) high performance product that was developed to meet the requirements of this type of application (large span and heavy loading). The design method allows for the full transfer of the railroad live loads to the new arch and subsequently to the grouted annulus and the reinforced concrete footings.
Contech provided technical support to the NS/Jacobs design team, as well as field services including plate assembly. Each BridgeCor arch was assembled at the site. The base channel was placed in a C-channel that was mounted to new footing extensions with exterior anchors. Once each arch was completely assembled, a flowable cementitious grout mixture was pumped into the existing void between the two structures. After the curing process, the result was a completely rehabilitated structure. The reline of the four arches was completed in December 2014 without any interruption to rail operations. The entire project is scheduled to be completed by February 2015.
Chief Engineer of Norfolk Southern Corporation, James Carter, commented, "The BridgeCor structural plate was an excellent product that allowed the rehabilitation of this stone arch bridge without interruption to service."