The representation of P-Δ effects using Yield Point Spectra

Yield Point Spectra are used to indicate the influence of P-Δ effects on the lateral strengths associated with constant ductility demands. The intensity of P-Δ effects is represented by a new index, termed the effective height, heff. This representation is useful for performance-based seismic design, because the effective height may be estimated accurately using information that is available early in the design process, and varies little as the initial design is further refined. This index is also useful for the evaluation of structures having known properties. An example illustrates design to limit peak displacement response in the presence of P-Δ effects when the initial stiffness is unknown. The design is based on an estimate of the yield displacement and uses heff to represent the intensity of P-Δ effects.