bridge column strengthening

Pennsylvania Bridge Column Strengthening

In 1995, Fibrwrap Construction installed the Tyfo® Fibrwrap® FRP system on all of the columns of the Interstate 84 bridge overpass in Scranton, Pennsylvania.  The bridge is a 468-ft., 4-span, continuous structure internally supported by 3 piers with two 5-ft. diameter columns each. The columns needed to be upgraded to provide an increase in seismic capacity as well as to provide a long-term structural protection to mitigate concrete spalling.

The shear strength of the existing columns was sufficient to support the elastic shear forces, but the columns could experience some inelastic damage due to seismic moments. As a result, some ductility was required at the plastic hinge locations at the top and bottom of each column for a total of 5’-0” in both locations.  FRP was utilized along the full column height, however, to allow a uniform aesthetic finish.

The base of the columns for piers 1 and 3 required a level of confinement attained by a 0.5" thick casing of Tyfo® Fibrwrap® in the plastic hinge regions. The plastic hinge region extends 5 feet from the footing. The upper portion of the columns should remain elastic, hence, no structural wrap is required in this region. However, a thinner casing (0.12") was utilized on the bare column to protect against chloride intrusion as well as to lend an aesthetic finish to the columns. The columns of Pier 2 will experience plastic hinging both at the top and bottom of the columns. A 0.5" thick casing of Fibrwrap® at the top 5 feet and the bottom 5 feet was retrofitted with the 9-ft. center portion wrapped with a thinner casing (0.12") for protective and aesthetic reasons.

In 2012, 17 years after the initial installation, an inspection showed no evidence of material delamination or other type of failure. The only slight to the installation was that graffiti had retaken its place over the finish coat. 

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