Effective Length Factor for Restrained Beam‐Column

Abstract

A development was undertaken to demonstrate the feasibility of using computer methods to calculate the effective length factors of elastically restrained beam‐columns. Three theoretical models for elastically restrained beamcolumns were derived to characterize the structural behavior of various types of elements used in offshore structures, such as jacket legs, piles, X‐braces, diagonal braces, K‐braces, etc. These beam‐columns are restrained by elastic rotational springs at the ends and an elastic translational spring at any given location along the beam‐columns. The expressions for the rotational and translational stiffness coefficients for the constraining elements and the characteristic equations for determination of the effective length factors for the restrained beam‐columns were derived by utilizing Livesley's stability functions. These expressions together with representative curves of effective length factors of beam‐columns in terms of constraining elastic spring constants, and calculated effective length factors for elements in example offshore structures are presented.