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Simply supported beam P-δ

P-δ is a local effect associated with axial load on displacement relative to element chord extending between end nodes. Figure 1 illustrates the influence of P-δ on a simply supported beam. Here, a longitudinal distributed load ω correlates with elastic bending-stiffness properties K_E to induce vertical displacement δ. An additional flexural contribution comes from the relationship between this deformed configuration and axial load P. The geometric stiffness properties K_G which dictate this relationship are discussed further in Dr. Edward L. Wilson's text, Static and Dynamic Analysis of Structures.

Values for the maximum flexural response which occurs at element midspan are shown in Figure 1:

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