Zp. Bazant et Yy. Xiang, POSTCRITICAL IMPERFECTION-SENSITIVE BUCKLING AND OPTIMAL BRACING OF LARGE REGULAR FRAMES, Journal of structural engineering, 123(4), 1997, pp. 513-522
Citations number
27
Categorie Soggetti
Engineering, Civil","Construcion & Building Technology
Periodic interior buckling of regular multistory and multibay rectangu
lar elastic frames with elastic bracing is analyzed. It is shown that
there exists a certain critical bracing stiffness for which the critic
al loads for the nonsway (symmetric) and sway (antisymmetric) buckling
modes coincide. Simple formulae for the critical stiffness are given.
For the critical and softer bracing, the type of postcritical bucklin
g behavior is the unstable symmetric bifurcation, exhibiting imperfect
ion sensitivity according to Koiter's 2/3-power law. For stiffer braci
ng, there is no imperfection sensitivity. The critical bracing, howeve
r, represents a naive optimal design which should be avoided because t
he imperfection sensitivity is the strongest. It is recommended that t
he truly optimal bracing should be significantly stiffer (perhaps 1.1
to 2 times as stiff). The buckling behavior, including the postcritica
l imperfection sensitivity, is similar to that of a portal frame analy
zed before. The solution also provides a demonstration of a simple met
hod for the initial postcritical analysis of frames recently proposed
by Bazant and Cedolin, which is based on energy minimization. In this
method, the distribution of cross section rotations is assumed to be t
he same as in the classical linearized theory. The curvatures and defl
ections are obtained from the rotations by integration with at least a
second-order accuracy (in terms of the rotations), and the axial shor
tening with at least a fourth-order accuracy.