Cable-Stayed Bridges - Sunshine Skyway Bridge (3)

A single plane of cables supports the main and side spans of the Sunshine Skyway Bridge along the center of the deck. Twenty one cables in a fan arrangement descend from each 240 ft tower (above the deck). The cables vary from 38 to 80 strands and are housed in nine inch diameter steel pipes.

The deck is 94 ft wide and so the precast single cell box girder superstructure must be pretty rigid to be supported only at the center. The main span is 1200 ft long, which is only 1/3 the length of the Sutong Bridge in China.

I can see a lot of cracking on the bridge deck. Hopefully the reinforcement remains in good shape in this marine environment. Deck replacement remains a big issue for cable-stayed bridges. Since the cables put the deck into compression, replacing the deck is difficult. Even when corrosion is not an issue, the deck is the most critical element since it is quickly worn down over time. It seems a shame if the bridge has to be replaced when the deck wears out.

Cable-Stayed Bridges - Sunshine Skyway Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - Sunshine Skyway Bridge (2)

I like the shape of the piers below the bridge deck but I have trouble with the stick-like appearance of the towers above the deck. Of course, they couldn't continue that shape above the deck without blocking the roadway. Still, they could have made the transition a little more attractive (there was no architect).

This is a completely concrete bridge and the superstructure is state-of-the-art (for the 1980s). This is one of the first bridges that used match cast construction of precast girders. The girders were gantry-launched and post tensioned after they were in place. The stiff concrete box girder main and side spans helps to stabilize the bridge against wind loads up to 240 mph and gusts up to 290 mph.

We'll take a closer look at this interesting bridge tomorrow.

Cable-Stayed Bridges - Sunshine Skyway Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - Sunshine Skyway Bridge

Florida is a good place to begin a study of cable-stayed bridges. The Sunshine Skyway is the world's longest bridge (5.5 miles) with a cable-stayed main span. It was built in 1987, replacing two steel cantilever bridges that were damaged by enough deadly ship collisions until a decision was made to replace them with a safer structure.

The center spans were later demolished with dynamite, which can be seen on a beautiful YouTube video. One of the damaged bridges is in the foreground of today's photo still in use as a fishing pier (for people and pelicans).

The new bridge was designed by Jean Muller and Eugene Figg. It was built to be extremely tall for it's time (193 ft) to allow the passage of container ships into Tampa Bay. The dolphins that surround the two towers were designed to resist the impact of a ship bigger than the ones that damaged the older bridges.

There's a lot of good information available on this handsome bridge and so we'll take another look at it tomorrow.

Cable-Stayed Bridges - Sunshine Skyway Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.