FLORIANOPOLIS SUSPENSION BRIDGE. The Flo rianopolis bridge, Brazil, with a main span of 1113ft. 9in., is the largest bridge in South America and the longest eye-bar suspen sion span in the world. It was constructed (5923-26) for the State of Santa Catharina, Brazil, to carry a highway, electric rail way and water-supply to the capital city Florianopolis situated on an island off the Atlantic coast.
The structure, designed by Robinson and Steinman, consulting engineers, is the first example of a new form of suspension bridge whereby greatly increased economy and rigidity are secured simultaneously.
Its distinctive feature is the utilization of the cable to replace the middle half of the top chord of the stiffening truss and the consequent change from the conventional parallel chord truss to a stiffening truss of more effective outline, namely, with maximum depth near the quarter-points of the span. These features com bined yielded a structure four times as rigid as the previous con ventional design, together with a saving of one-third of the steel work.
Another departure from conventional practice was the adoption of rocker towers, which, eliminating the customary bending stresses, contributed a saving of 20% of the steelwork in the towers and permitted the main piers to be reduced to concrete cylinders 16f t. in diam. The steel towers are 2 2 5f t. high. Instead of wire for the cables, eye-bars were adopted ; these were made of the newly developed, high-tension, heat-treated carbon steel, having a yield point exceeding 75,o00 lb. per sq.in. and used with a working stress of 50,000 lb. per square inch.
In the foundation work for the main piers, novel construction methods had to be devised. By excavating and concreting suc cessive test pits, the entire foundation area of one pier was carried down 2oft. below the bottom of the coffer dam to bed rock at elevation —6o. The concrete anchorages are of novel design, U-form in plan, for maximum efficiency. The island anchorage is on rock, the continent anchorage on piles. An entirely new method was developed for the erection of the eye-bar cables and the suspended stiffening trusses, using overhead trolley, thus eliminat ing wooden falsework and working platforms. The bridge, which was over three years in building, provides a 28ft. roadway, a meter-gauge electric railway, a 24in. water main and a 9f t. side walk. Its over-all length is 2,69of t.; it contains 4,400 tons of steel and 14,5oocu.yd. of concrete.
Three other bridges of the Florianopolis type have since been built : the Point Pleasant and the St. Mary's (each of 7ooft. span) over the Ohio river (U.S.), and the Indoroopilly (hoof t. span) over the Brisbane river (Australia). (D. B. S.)