The Structural Engineer > Archive > Volume 6 (1928) > Issues > Issue 4 > NOTES ON RECENT DEVELOPMENTS IN BRIDGE ENGINEERING - III
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NOTES ON RECENT DEVELOPMENTS IN BRIDGE ENGINEERING - III

The Florianopolis Suspension Bridge, having a main span of 1,113 ft. 9 ins., and a versed sine of 120 ft., in addition to being the longest suspension .span in the world with eye-bar or link chains, is also of special interest as being the first executed example of a novel type of stiffened suspension construction, by means of which greatly increased rigidity and economy of material are realised. A further departure from usual practice is the employment of rocker towers, this being the first suspension bridge in the Americas to be so built. The only large bridges previously built with hinged towers are the Elizabeth Bridge at Budapest (1903) and the suspension bridge at Cologne (1915). Still further interest attaches to the employment for the eye-bars, of high tension, heat treated carbon steel having to satisfy a specification of minimum ultimate tensile strength of 105,000 lbs. per sq. in., minimum elastic limit of 75,000 lbs. per sq. in., and minimum elongation of 5 per cent. In 18 ft., the tests being made on full-sized bars. The intended working stress in these bars is 50,000 lbs. per sq. in. Further reference will be made h the tests of this material, but it may here be noted that the average results of thirteen tests of full sized bars gave an ultimate strength of 123,000 lbs. elastic limit,, 84,500 lbs. per sq. in. and percentage elongation of 6.8 in 18 ft. The tender for the eye-bar chains in this instance reduced the total cost to the lowest estimated cost of the bridge if constructed with wire cables. Finally, a new method was employed for the erection of the eye-bar chains and stiffening girders, using an overhead trolley line, thereby eliminating falsework and working platforms. The erection occupied one year and was accomplished without loss of life. J Husband