REMOTE MONITORING AND REPLACEMENT OF NORFOLK SOUTHERN BRIDGE CF-35.40 OVER COTTON RUN, SEVEN MILE, OH

摘要

A storm event on May 24th, 2017 resulted in extreme flooding of Cotton Run that nearly overtopped the existing rails of the Norfolk Southern Bridge CF-35.40 in Seven Mile, OH. The existing structure was 92 years old and comprised of three (3) 22'-6" concrete slab beam spans supported on concrete piers and concrete gravity abutments carrying one main line track. This flood exceeded the 100-year flood elevation by several feet and created a scour condition at the base of the East Pier. The East Pier settled more than one foot, with a corresponding distortion of the superstructure resulting in loss of support at track level. Norfolk Southern immediately installed timber cribbing and rip rap around the pier to restore service under reduced speeds. A remote-monitored structure monitoring system was installed on the bridge while permanent improvements were developed. The remote monitoring system worked as a warning system if the bridge were to experience further loss of support and was in service until the superstructure could be replaced. The replacement span is a 52'-0", single span, through-girder bridge supported on precast concrete abutment seats and 5'-0" diameter drilled shafts. The design accommodated construction of drilled shaft foundations outside the footprint of the existing bridge to allow uninterrupted track service during foundation installation. The superstructure was replaced within a 24-hr planned outage on May 21, 2018, nearly one year after the storm event. This paper outlines the benefits and lessons learned from the structure monitoring system and accelerated bridge construction approach.