استحکام ستون های فولادی تقویت شده توسط crossarmsهای باقی مانده و چندگانه Stability of steel columns stiffened by stays and multiple crossarms

1. Introduction Global buckling tends to occur in compressed steel columns when they are slender. However, the buckling resistance can be drastically improved by introducing stays and crossarms. The compressed steel column, which is equipped with stays and crossarms, has been named prestressed stayed steel columns (PSSC). In the PSSC shown in Fig. 1, an additional restraint can be placed on the main column by the crossarms in conjunction with pre-tensioned stays. Research on PSSC has been conducted since the 1960s, in which Chu and Berge first investigated the critical buckling loads in PSSCs [1]. Following the work of Chu and Berge, Hafez quantitatively examined the effect of pretension on the buckling load by theoretical derivation based on the assumption of small deformations [2]. With the development of computer technology, particularly over the last twenty years, nonlinear buckling analysis in PSSCs by finite element (FE) software became possible. Thus, geometric imperfections governing nonlinear buckling [3–5], evaluate the post-buckling behaviour [6,7], and investigate the optimum design method can be conducted numerically [8,9]. Experimental studies have also been conducted in parallel with FE analyses on PSSCs [10–14]. For practical application of PSSCs, the compressed steel columns are generally stiffened by spatial crossarm systems (see Fig. 2) around the main column and multiple crossarms along the main column length (see Fig. 2(b)). Unfortunately, most of the previous studies concentrated on investigating PSSCs with crossarms only set at the mid-span of the main column (see Fig. 2(a)), which are not typically found in practice. As far as the authors are aware, references [15, 16] are the only studies aimed at investigating the stability of PSSCs with multiple crossarms. However, the interactive buckling behaviour of PSSCs with multiple crossarms has not been investigated. In fact, research on PSSCs with single-bay crossarms shows that interactive buckling may become dominant when determining the actual buckling strength. Based on the background information introduced above, this current work focuses on investigating the stability of PSSCs stiffened with multiple crossarms along the main column length. First, pretension was derived by geometric analysis, which corresponds to the maximum critical buckling load. This pretension level was used as the benchmark pretension value in the FE simulation. Subsequently, critical and nonlinear buckling analyses were conducted to explore the buckling strength of PSSCs stiffened with multiple crossarms. In addition, a discussion based on parametric analysis results was presented to quantitatively examine the effect of cross-sectional area of the stays and pretension in stays.