The Easton-Phillipsburg Toll Bridge carries U.S. Route 22 traffic over the Delaware River. The first of the seven toll bridges constructed and operated by the Delaware River Joint Toll Bridge Commission (DRJTBC), it was opened to traffic on January 14, 1938. The main river bridge consists of a 540-foot Petit through-truss span over the river, a 430-foot five-span plate-girder viaduct at the New Jersey approach, and a 40 foot pre-stressed concrete box beam span over Pennsylvania Route 611 on the Pennsylvania approach.
In 2010, the DRJTBC engaged Intelligent Infrastructure Systems to evaluate the condition, vulnerabilities and performance of the bridge through a comprehensive approach that merged conventional engineering practices with advanced sensing and simulation technologies.
Intelligent Infrastructure Systems led the implementation of technology applications, including the use of high-speed strain gages to capture live load response, vibrating wire gages to capture temperature induced response, and a suite of accelerometers to capture ambient vibration response. Each of these sensing applications were developed to inform the most uncertain aspects of the bridge’s performance and were designed based on the results of a series of simulations from a detailed 3D finite element model. The model itself was constructed and error-screened by Intelligent Infrastructure Systems and was verified through document reviewing and site visits and calibrated based on the results from the sensing applications.
These sensing and simulation studies were able to demonstrate that the live load stresses in the critical tension members were quite small and that the bridge (under current operating conditions) could be expected to have infinite fatigue life. Additionally, it was demonstrated that the floor system and wind braces were acting redundantly with the bottom chord, and therefore significant reserve capacity was available. Given the desirable performance observed, no major retrofit was required, however, to ensure that the bottom chord redundancy was maintained, some repairs to deteriorated connections within the wind-bracing system were recommended.