In 1998, KCA provided engineering services to the FDOT for the repair of the high level bridge which carries SR A1A over the Intracoastal Waterway. Located in the highly corrosive environment near the Atlantic Ocean, the piers had begun to exhibit distress and large cracks had formed in the pier walls within a few years after the bridge was constructed.

The bridge had been constructed in two phases in order to facilitate the maintenance of traffic on the existing adjacent bridge. The piers typically consist of three columns supported by a wall which sits atop a pile footer. In most of these piers, the portion of the pier which was constructed in Phase I was exhibiting numerous large vertical and diagonal cracks in the wall. One pier had a spall in the wall that threatened to undermine the integrity of the outer column.

KCA was retained to inspect and analyze the piers and to determine the cause of the cracks in the wall. In addition, KCA was to determine how to prevent additional cracking and protect the structure from further deterioration. Using strut-and-tie methods as well as finite modeling, differential settlement and phased construction loads were examined. Based on these analysis, it was calculated that the wall was overstressed during the Phase I construction.

KCA’s design to repair the wall used post-tensioned tendons protected by a newly constructed reinforced concrete shell. KCA also designed a complex steel shoring structure to stabilize the pier while the spall was repaired near the exterior column. KCA continued to provide post-design services throughout construction by reviewing shop drawings, repair materials, jacking operations, and proposed design changes.

Eight piers were specified to be post tensioned at an estimated construction cost of over $1.2 million.

Eight piers were specified to be post tensioned at an estimated construction cost of over $1.2 million.