OVERVIEW

Flexible cables have been used to form structural systems for many centuries. Some of the earliest man-made structures of any size were hanging bridges constructed from jungle vines and creepers, and spanning ravines and rivers. In European literature the earliest description of an iron suspension bridge was published by Verantius in 1607, while ropes have been used in military bridging from at least 1600. In modern times, cables formed by binding a large number of steel wires together are employed in bridge construction where the bridge deck is suspended on hangers from the cables themselves. The cables in turn pass over the tops of towers and are fixed to anchor blocks embedded in the ground; in this manner large, clear spans are achieved. Cables are also used in cable-stayed bridges, as part of roof support systems, for prestressing in concrete beams and for guyed structures such as pylons and television masts.

Structurally, cables are extremely efficient because they make the most effective use of structural material in that their loads are carried solely through tension. Therefore, there is no tendency for buckling to occur either from bending or from compressive axial loads (see Chapter 21). However, many of the structures mentioned above are statically indeterminate to a high degree. In other situations, particularly in guyed towers and cable-stayed bridges, the extension of the cables affects the internal force system and the analysis becomes non-linear. Such considerations are outside the scope of this book so that we shall concentrate on...