Tampa Bay, FL
As one of the most renowned structures in America, the Sunshine Skyway Bridge has caught the attention of many. Former New York Times architecture critic, Paul Goldberger, has described the bridge as “from an aesthetic standpoint that may well rank as the most impressive piece of large-scale bridge design in this country in half a century.”
Unfortunately, the bridge has a bit of a cursed history that has plagued the structure for years. The signature bright yellow stay cables and the towers holding up the triangular sails give the appearance of a sailboat that coasts across Tampa Bay but the existing bridge is a replacement from the steel, cantilevered truss structure that previously held these sails afloat. On May 8, 1980, a freighter lost control during a foggy morning and crashed into the bridge resulting in the collapse of a 1,200 ft span of the bridge and the death of 35 people. This horrific tragedy took its toll on the community and in addition took seven years to rebuild the structure.
Problems That Led To Repair
The Sunshine Skyway Bridge is just as remarkable from an engineering standpoint as an aesthetic one. When constructed, the bridge was the longest in the world that had a cable-stay main span. With an overall length of 5 ½ miles, a main span of 1,200 ft and the vertical clearance of 190 ft the bridge soars high above the rest.
Costing $244 million after reopening to traffic in 1987, the bridge has a total of 650 precast concrete girders that support the northbound trestle spans and another 650 girders to support the southbound span. During routine inspections, shear cracking was observed on the trestle span girders and the number of cracked beams appeared to increase over time. Inclined shear cracking was much more prevalent on the exterior girders than the interior ones showing 97.7% on the southbound bridge with 1% cracking on the interior and 93.1% on the northbound bridge with 1.3% cracking on the interior. Additionally, cracks were observed on the pier caps with some large and prominent exhibiting visible signs of water penetration and deterioration.
Sika Product Solution
In order to address the shear cracks in the AASHTO girders and pile caps, all cracks wider than 0.012 inches had to be injected with epoxy. Then, all spalls had to be repaired and leveled using a polymer-modified cementitious mortar with an integral corrosion inhibitor. Finally, all bug holes and small cavities were restored using an epoxy paste.
In addition, it was determined that the deficient girders needed to be structurally strengthened by the use of a carbon fiber system. SikaWrap® Hex 115C conformed to the geometry of the AASHTO girders very easily and was used with Sikadur® 330 and Sikadur® 300 epoxy to ensure no corrosion from the marine environment would penetrate the durable exterior.
Sika Repair Then & Now
After evaluating the repairs that were executed over ten years ago, it is clear to see that the bridge looks the same as the day the products were applied. This bridge has endured numerous tropical storms and hurricanes including Irma in 2017. The goal set forth 10 years ago for these repairs is to maintain the 75-year service life of the bridge and to provide a durable waterproof protection against the salt water exposure. All the CFRP repairs along with their protective coatings are holding up exceptionally well with the inspection in May 2018, even the test areas appear the same as they were the day they were applied! It is clear that the Sunshine Skyway Bridge will be able to withstand the next ten years and beyond.