High Rise Building Column Design

The building column design procedure should take into account the effect of frame instability. This effect can be considered by use of the effective lengths of the columns or by application of P-Delta forces. For a selected class of frames and loadings, the effect of frame instability may be ignored. Use of the effective length of columns is a reliable procedure provided that satisfactory approximations of the effective lengths of the columns can be calculated. These calculations must consider any nonsymmetry of building properties and loads, material yielding, connection flexibility, and support conditions. Application of P-Delta forces is an approximate, direct, working stress design procedure applicable to both regular and irregular frames in combination with possible complimentary bracing systems. The approximation has been verfied for a limited class of structures and use of a conservative factor of safety is recommended. Selected frames and limitations for which instability effects can be ignored are summarized.