Engineering Transactions, 57, 1, pp. 3–15, 2009

Dynamic buckling of non-sway imperfect rectangular steel frames

I. G. RAFTOYIANNIS
National Technical University of Athens Department of Civil Engineering

A. N. KOUNADIS
Academy of Athens Biomedical Research Foundation

A nonlinear stability analysis is performed on non-sway rectangular two-bar steel frames
subjected to a concentrated, suddenly applied joint load with constant magnitude and infinite
duration. Using energy and geometric considerations, the dynamic buckling load is determined
by considering the frame, being a continuous system, as a discrete 2 degrees-of-freedom system
with corresponding coordinates of the two bar axial forces. The effect of imperfection sensitivity
due to loading eccentricity is also addressed. A qualitative and quantitative analysis
of these autonomous systems yields a substantial reduction of the computational work. The
efficiency and reliability of the nonlinear stability analysis proposed herein is illustrated by
several examples, which are also solved using finite element nonlinear analysis.
Keywords: nonlinear dynamic stability, imperfect frames, suddenly applied load, loading eccentricity, FEM
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