Eiffel anticipated skyscraper construction when he designed the Statue of Liberty's supporting frame. He produced a 94-ft-high wrought-iron square skeleton whose chief structural members are four posts that work in compression.

The skeleton supports a secondary iron frame that, in turn, carries a system of flat wrought iron bars. These members carry the copper plates that form the statue's exterior skin. Extending from the main frame are a smaller frame supporting the head and a slim 47-ft, 7-in. skeleton carrying the arm that holds the torch.

The frame is braced with diagonal members and was designed to withstand a wind load of 58 psf. In a 50-mph wind, the monument moves 3 in.

The sheathing of the statue is made up of 3/32-in. copper plates. In Paris, Bartholdi constructed full-scale plaster models of all parts of the statue. From these, large wooden molds were made of the statue's surface. Using the repousse method, copper sheets were hammered within these molds to reproduce the statue's contours on the the plates.

In all, 350 plates make up the statue's surface. Two-in.-wide straps of iron were forged to fit inside each plate. Although the copper plates overlap and are riveted to each other, they are supported entirely by these iron bars. The bars are angled upward at about 60° and act like springs. The design allows the skin to bend without being damaged by high winds or extreme fluctuations in temperature.

Bartholdi assembled the statue in Paris, using temporary rivets to link the copper plates. Then it was disassembled and shipped in 210 crates to New York in 1885.

On Bedloe's (now Liberty) Island in New York Bay, an 89-ft-high granite-faced reinforced concrete pedestal was built--one of the first instances of the large-scale use of reinforced concrete.

The statue was reassembled on the pedestal without any exterior scaffolding. As the framework rose, the workmen attached the copper skin with 300,000 copper rivets in precisely drilled holes.

The Statue of Liberty was dedicated in October 1886.

1890
The Glorious Forth

The Forth Railway Bridge over the firth (mouth) of the Forth River at Queensferry, Scotland, was the world's first all-steel long-span bridge and the world's longest bridge. It ushered in the age of great cantilevers.

The bridge has three towers supporting two cantilevers and two main spans, each 1,710 ft long. Because of navigational requirements and the river's route between steep banks in two deep channels, a rail crossing 157 ft above high water was deemed necessary. The use of balanced cantilever method enabled the bridge to be built without falsework.

Each tower rests on four 70-ft-dia masonry piers based on bedrock. The piers were formed by sinking 70-ft-dia wrought iron caissons in place at depths ranging to 90 ft below water level.

The tubular section construction and the unusual configuration of the trusses give the Forth Bridge its distinctive appearance. Each of the 331-ft-high towers consists of two trusses that slope inward. The trusses are separated by 120 ft at the piers, narrowing to 33 ft at the top.

The trusses were built of steel tubes fitted with internal stiffeners. The heaviest compression members are 12 ft in diameter and are made from 11/4-in. steel plates that are 16 ft long and 41/2 ft wide. The tension members are lattice girders (Eng. News 10/22/1887 p. 582). The cross-sectional and plan shapes of the principle girders are tapered, complicating fabrication.

The bridge was designed to withstand a wind force of 56 psf. Scotland's Tay Bridge, which failed in 1879 in high winds, killing 75, was designed for a force of only 10 psf.

The Forth Bridge's cantilever portion measures 5,300 ft from pier to pier. Still in use today, the Forth Bridge held the world's cantilever record until 1917.