دانلود رایگان مقاله در بهبود کمانش ستون پیش پیچ خورده های فولادی جهانی

ABSTRACT

This paper investigates the improvement in elastic buckling capacity of pretwisted columns using Linear Perturbation Approach. Three different Universal Column (UC) sections of various lengths were considered in the proposed study assuming fixed–fixed and pinned–pinned end conditions. Linear perturbation analysis was first verified by comparing the critical loads of the simulated straight columns with analytical results. Numerical analysis was then extended to simulate the buckling improvement of pretwisted columns considering four different lengths of 4 m, 5 m, 6 m and 7 m, and a range of twisting angles between 0° and 180°. The results showed that the initial twisting has positively impacted the axial capacity of the pretwisted columns. This noticeable improvement is supported by the significant increase in the buckling capacity for the three UC sections, particularly at angles of twists between 120° and 150°.

6. Conclusions

Elastic buckling of pretwisted fixed-ended steel columns was studied using linear perturbation analysis through finite element modeling. Universal columns with three different cross-sections of various lengths, initially twisted at angles from 0°–180°, were analyzed in this study. The expected effect of pretwisting was to improve the buckling capacity of the compression members. Consequently, permanent pretwisting is to be perceived as an effective technique to increase the strength of any steel compression member. Results showed that there is a significant improvement in the critical buckling capacity for different slenderness ratios. A sharp increase in buckling capacity up to 90% improvement as compared with non-twisted sections was demonstrated in most sections. However, the effect of various column lengths on the buckling improvement for a given UC section was insignificant. The present FE analysis was examined by comparison with the results predicted by the earlier proposed equation by Abed et al. [1] and good agreement was achieved. Buckling capacity of pretwisted UC sections with pinned–pinned end conditions was also investigated. The improvement in the axial capacity was found to be very small as compared with its fixed-ended counterparts. Only 20% maximum increase in the buckling capacity was achieved for the three UC sections used in this study.