TABLE OF CONTENTS Anchors are primarily designed and constructed to resist outwardly- directed loads imposed on the foundation of a structure. These outwardly-directed loads are transmitted to the soil at a greater depth by the anchors.
Buried anchors have been used for thousands of years to stabilize structures. Tents are the oldest structures which were stabilized by using anchors or stakes. Until the middle of the nineteenth century, anchors were primarily used for stabilizing fairly lightweight structures. With the design and construction of large suspension bridges, very large loads were transmitted to the bridge foundation. In order to support these loads, permanent anchoring systems in rock medium were gradually developed and constructed.
With the development and construction of special lightweight structures such as lattice transmission towers and radar towers, design of special tension anchoring systems for foundations became necessary, primarily because the wind load created reactions which were greater than the self-weight of the structures.
Earth anchors of various types are now used for uplift resistance of transmission towers, utility poles, aircraft moorings, submerged pipelines, and tunnels. Anchors are also used for tieback resistance of earth-retaining structures, waterfront structures, at bends in pressure pipelines, and when it is necessary to control thermal stress.
The earlier forms of anchors used in soil for resisting vertically-directed uplifting loads were screw anchors. Figure 1-1 shows two different configurations of screw anchors. These anchors were simply twisted into the ground up to a pre-estimated depth, and then tied to the foundation. They were either used...
