P-Δ Effects on Single-Degree-of-Freedom Structures in Earthquakes
- 1 August 1994
- journal article
- Published by SAGE Publications in Earthquake Spectra
- Vol. 10 (3) , 539-568
- https://doi.org/10.1193/1.1585788
Abstract
A vertical force, P, moving through a lateral displacement, Δ, causes extra “ P-Δ” forces on a structure that are not accounted for in analyses based on the undeformed structural geometry. If the effect of these P-Δ forces are large, then displacements during an earthquake may be greater than those when the P-Δ effect is not considered and the likelihood of overturning increases. This paper discusses previous studies to understand the problem of P-Δ. The likely change in response of bilinear oscillators is found from knowledge of the behaviour of simple single degree of freedom bilinear oscillators and the effect of P-Δ on a hysteresis loop. Using the “hysteresis centre curve” (HCC) concept, recommendations are made for the design of single degree of freedom structures with general shape hysteresis curves considering the P-Δ effect.Keywords
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