Wesley Vanlaere

Influence of plasticity on lateral–torsional buckling behaviour of cellular beams

Abstract The use of steel beams with large circular web openings along the length of the beam has increased steadily during the last decades. However, not all aspects of the design of these cellular beams have been studied extensively, such as lateral–torsional buckling (LTB). In previous work, an existing design rule for this failure mode was investigated for purely elastic beams. Even though this rule was shown to be quite accurate for most cases, it could sometimes give unsafe results for certain short length geometries. In reality, however, the steel will display elastic–plastic behaviour, causing these geometries to fail by plasticity of the cross‐section rather than elastic instability. In this work, the design rule will be further examined by performing numerical simulations, taking into account these effects of plasticity, as well as imperfections and geometric nonlinearity. It will be shown that the existing design rule always gives safe results for the examined geometries.

Plastic collapse of steel water towers

The aim of this contribution is to verify an existing design rule for steel liquid-filled conical shells by performing numerical simulations. Questions were raised regarding the reliability of the design rule as early yielding comes into play if an axisymmetric imperfection is located near the lower rim where the stresses are elevated. In our study, full nonlinear numerical simulations are performed with a realistic weld depression as imperfection shape. This weld depression is placed at the most detrimental location near the lower rim. The results of the simulations show that for cones with a moderate relative slenderness the design rule indeed overestimates the buckling strength, but that the error is not pronounced and that the design rule may be considered as still acceptable.

EARLY YIELDING OF LIQUID-FILLED CONICAL SHELLS

In liquid-filled conical shells, the combination of compressive meridional stresses and tensile hoop stresses can lead to instability. The present design rule for these structures is verified in this contribution by means of numerical simulations. Large axisymmetric imperfections are detrimental and may lead to failure by plastic buckling. For these shapes the design rule may be unconservative. The realism of the proposed shape deviations is questioned. However, partially or completely axisymmetric weld depressions cant be excluded from the simulations. This means that an elaborated study is needed and that the design rule must be checked even further.