Imperfection sensitivity of thin-walled I-section struts susceptible to cellular buckling

Abstract

A variational model that describes the nonlinear interaction between global and local buckling of an imperfect thin-walled I-section strut under pure compression is developed. An initial out-of-straightness of the entire strut and an initial local out-of-plane displacement in the flanges are introduced as a global and a local type of imperfection respectively. A system of differential and integral equilibrium equations is derived for the structural component from variational principles, an approach that was previously validated. Imperfection sensitivity studies focus on cases where the global and local critical loads are similar. Numerical results reveal that the strut exhibiting cellular buckling (or 'snaking') is highly sensitive to both types of imperfections. The worst forms of local imperfection are identified in terms of the initial wavelength, amplitude and degree of localization and these change with the generic imperfection size and highlight the potential dangers of unsafe predictions of actual load-carrying capacity.

Imperfection sensitivity of thin-walled rectangular hollow section struts susceptible to interactive buckling

“…where z ∈ [0, L] and the imperfection is symmetric about z/L = η. Since previous work on sandwich panels [22], I-section struts [23], stiffened plates [24] and functionally graded carbon nanotube-reinforced composite beams [52] have demonstrated that the worst case occurs when the local imperfection is symmetric about midspan, the value of η is selected to be 1/2. The quantity A 0 controls the amplitude of the imperfection component.…”

“…Even though the possible individual buckling modes taken in isolation are stable or neutral in terms of their post-buckling behaviour, the triggering of various combinations of modes simultaneously can lead to a violent destabilization after the ultimate load is reached [13,14,15,16,17]. More importantly, such structural components tend to be highly sensitive to imperfections [18,19,20,21,22,23,24,25]; a tiny imperfection may lead to a significant erosion in the load-carrying capacity.…”

“…Wadee and his collaborators have developed a series of analytical models to study the imperfection sensitivity of sandwich panels [22], stiffened plates [24] and I-section struts [23,25] that exhibit mode interaction. It has been determined that these compression members are sensitive to both local and global geometric imperfections.…”

Slenderness effects in thin-walled I-section struts susceptible to local–global mode interaction

“…This expression is derived from a leading-order solution to a multiple scale perturbation analysis of a strut on a nonlinear softening foundation, which matches the least stable localized buckling mode shape closely [22]. The quantities α and β control the degree of localization and the periodic frequency of the imperfection shape respectively and are currently chosen to match the initial local buckling eigenmode found in earlier work [23].…”

Interactive buckling in long thin-walled rectangular hollow section struts

“…The interaction between individual modes can lead to a profound change in the post-buckling behaviour, even though these modes may be stable when triggered in isolation. In particular, such systems can exhibit a violent destabilization after the peak load is reached [9,10,11] and, in certain parametric ranges, have been demonstrated to be highly sensitive to initial geometric imperfections [12,13,14,15,16,17,18,19].…”