Induced moments and lateral deflections in columns with initial imperfections and semirigid connections:

Abstract

Closed-form expressions that can be used to evaluate the induced elastic bending moments and second-order deflections in slender prismatic columns with initial geometric imperfections (i.e., initial curvature and out-of-plumbness) and semirigid connections when subjected to eccentric axial loads at both ends are derived in a classical manner. The proposed approach is based on the classical Euler-Bernoulli theory for columns with sidesway uninhibited, partially inhibited, and totally inhibited. The combined effects of initial imperfections, axial load eccentricities and semirigid connections are condensed into the proposed equations. The effects of shear and axial deformations along the member span are not included. Comparisons of the induced elastic moments, second-order deflections and critical loads obtained using the proposed approach and those available in the technical literature for classic column cases are presented in a companion paper. Also sensitivity studies and several examples are presented in detail that demonstrate the effectiveness and accuracy of the proposed closed-form equations and the importance of initial imperfections, semirigid connections and lateral bracing on the second-order behavior and stability of beam-columns. These effects must be taken into account in the analysis and design of imperfect slender columns subjected to high axial loads, particularly when sidesway between its ends is uninhibited or partially inhibited because of possible failure by lateral collapse.