6. Conclusions
The stability behaviour of the two-bay prestressed stayed steel column was geometrically and numerically investigated in this study. Both linear and nonlinear buckling analyses were performed. The influence of the crossarm length and pretension in the stays were studied. Conclusions drawn from this study are as follows:
(1) According to the geometric analysis, it has been demonstrated that the relationship between pretension in stays and the linear buckling load can be described by a single equation. Moreover, the equation used to determine pretension in stays which corresponds to the maximum buckling load has been proposed.
(2) The critical buckling modes of two-bay PSSCs are more complicated than the single-bay PSSCs. The critical buckling mode in this structure can be observed to have a shape that is similar of three halves of a sine curve. However, this buckling mode cannot be observed as the lowest buckling mode in single-bay PSSCs.
(3) Based on the nonlinear buckling analysis results, it has been found that the effect of interactive buckling can be ignored when determining the actual buckling load of two-bay PSSCs. In other words, it is safe enough to introduce geometric imperfections following the lowest buckling mode when designing this structure. In contrast, an asymmetric imperfection must be constructed to determine the actual buckling strength of singlebay PSSCs in some cases.
(4) The effects of stay diameter and pretension in stays on the buckling strength of PSSCs have been investigated. It has been found that a stay without pretension can effectively improve the loadcarrying capacity of ordinary steel columns, because the stay stiffness can be automatically activated by deformation of the steel column. Thus, the effect is limited when adopting high pretensions to increase the buckling strength of PSSCs.
