Senior Engineer Hugh Ronald was recently published in Aspire, a quarterly magazine published by the Precast/Prestressed Concrete Institute (PCI) in cooperation with the associations of the National Concrete Bridge Council.
In his authored article, “Bearing Zone Tearing and Spalling in Precast, Prestressed Concrete Girders,” Hugh discusses a problem that develops during fabrication of highly stressed bulb tee girders. One of the challenges to girder fabrication has been the advent of tearing (cracking) and spalling of the concrete in the girder bearing zones, a phenomenon that occurs during prestress transfer.
The article outlines the nature of the problem and provides solutions that have been successful, but also encourages further industry work to better define the threshold conditions that trigger the problem.
He outlines the following variables that contribute to the problem:
- The initial prestress force applied to the girder, considering the effect of debonded strands
- The eccentricity of the prestress force
- The weight of the girders (or more precisely the bearing reaction and stress due to friction between soffit and girder in the bearing zone.