The societies that lived in South America, Africa and Asia thousands of years ago strung twisted vines attached to trees to cross over rivers. They added branches to create a flat surface to walk upon.
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The Incas would tie rafts across a stream together so that the rafts would not get carried away by the fast current. Then they used vines and rope woven together to make the ropes, then they strung them together across the gorge. They did this all while standing on the rafts. Hope this helps :)
The Inca's used vines, grasses (which were braided together) and boulders for the bridge to be put in place.
Wood, mostly...
wood and hot metal
Cables .
The longest bridges in the world are viaducts or trestle bridges. It is easier to design a high, elevated roadway by directly supporting it with many towers or piers (as in a viaduct or trestle bridges). It is more difficult to design an elevated roadway with a large unobstructed span (as in a suspension bridge or arch bridge). However, the bridges with the longest unobstructed spans in the world are invariably suspension bridges, because ...
i dont know but its strong
Bridge towers are used in suspension bridges or cable stayed bridges. cables, what hold roadway, are fixed there.
tension :D
tension :D
steel cable suspension
Steel is the most common, especially for suspension bridges. Concrete is used for lower bridges (and where little shifting will occur) because it is more resistant to the elements.
Steel
Truss Bridges=Trusses have been used extensively in bridges since the early 19th Century. Early truss bridges were made of wood.==in additon the classic American covered bridges are all trusses, though the wooden truss members are covered by walls and a roof, for protection from the elements. Later truss bridges were made of cast iron and wrought iron. Most modern trusses are made of structural steel.=
John Roebling