ABSTRACT
Many structural members are subjected to longitudinal compression, including columns and walls in buildings, bridge piers, foundation piles, poles, towers, shafts and web and chord members in trusses. The idea of applying prestress to a compression member may at first seem unnecessary or even unwise. In addition to axial compression, however, these members are often subjected to significant bending moments. Bending in compression members can result from a variety of load types. Moments are induced in the columns in framed structures by the gravity loads on the floor systems. Lateral loads on buildings and bridges cause bending in columns and piers and lateral earth pressures bend foundation piles. Even members that are intended to be axially loaded may be subjected to unintentional bending caused by eccentric external loading or by initial crookedness of the member itself. Most codes of practice specify a minimum eccentricity for use in design. All compression members must therefore be designed for combined bending and compression.
