Buckling assessment of cylindrical steel silos under wind loading

Thin-walled cylindrical steel silos are susceptible to instability under wind pressure when they are empty or only partially filled. This paper investigates numerically the wind buckling behavior of three steel silos. They are composed of flat sheets with stepped walls with multiple discrete steps in thickness.
The vertical and circumferential distributions of wind loading were adopted from Eurocode. Two proposed circumferential pressure distributions for an isolated silo and a silo in a group were taken into consideration. Where the silo does not have a closed roof, an additional uniform value of internal underpressure coefficient should be considered, thus increasing the net stagnation inward pressure on the silo walls. The effects of additional inward pressure on a vented silo with a small opening were specially explored through the paper. Therefore, a total of four different load cases were examined in this paper: isolated load case and grouped load case, each of them for silos with closed roof and for vented silos.
Two types of analyses were undertaken for the wind buckling assessment of the silos: the linear elastic bifurcation analysis and the geometrically and materially non-linear analysis. According to non-linear load-deflection curves, the buckling in all load cases was of snap-through type. The curves showed more non-linear charecteristics in group load case. Moreover, in general, the wind buckling resistance of silos under grouped load case was less than isolated load case. Finally, silos with closed roof compared with vented silos with a small opening, exhibited about 40% more wind buckling resistance.