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Title: UHPC Repair of Steel Columns in the Walnut Tunnel

Author(s): McDonagh

Publication: Web Session

Volume: ws_S22_McDonagh1.pdf


Appears on pages(s):



Date: 3/28/2022

In 2020 the Pennsylvania Department of Transportation (PennDOT) District 6-0 in conjunction with Southeastern Pennsylvania Transportation Authority (SEPTA) rehabilitated the PennDOT bridge structure located within SEPTA’s Walnut Tunnel, which carries the airport regional rail line. The bridge/tunnel includes a series of steel columns supporting the tunnel ceiling that were experiencing advanced corrosion and section loss. PennDOT and their designer, Alfred Benesch & Company, decided to replace the existing concrete pedestals and encase the deteriorated steel columns with ultra-high-performance concrete (UHPC), in the first use of UHPC for steel column repair in North American transportation infrastructure. The UHPC provides additional compressive and buckling resistance to compensate for the columns’ section loss and protects the steel columns against any future corrosion due to its extremely low permeability. The contractor selected Steelike® UHPC, which provided several unique placement advantages. Steelike’s standard practice of mixing in ready-mix trucks allowed the UHPC to be mixed above the tunnel and away from work areas. The material was then discharged directly from the trucks above the repair locations into a tremie line. The large mixing capacity of the trucks provided a continuous flow of material, enough to fill multiple column repair forms per batch.