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There are two main types of buckling, local and global buckling, in the elements under compressive for elements subjected to axial compression force.
Local Buckling
Local buckling occurs when some part or parts of the cross-section of a column are so slender that they buckle locally in compression. The However, the strength corresponding to any buckling mode cannot be developed , however, if the element of the cross-section is so thin that local buckling occurs.
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TABLE B4.1a | ||||||||
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Case | Element Description | Width-to-Thickness Ratio | Limiting Width-to-Thickness Ratio λr (nonslender/slender) | Examples | ||||
1 | Flanges of rolled I-shaped sections, plates projecting from rolled I-shaped sections, outstanding legs of pairs of angles connected with continuous contact, flanges of channels, and flanges of tees | b/t |
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2 | Flanges of built-up I-shaped sections and plates or angle legs projecting from built-up I-shaped sections | b/t |
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3 | Legs of single angles, legs of double angles with separators, and all other unstiffened elements | b/t |
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4 | Stems of tees | d/t |
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5 | Webs of doubly symmetric rolled and built-up I-shaped sections and channels. | h/tw |
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6 | Walls of rectangular HSS | b/t |
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7 | Flange cover plates and diaphragm plates between lines of fasteners or welds | b/t |
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8 | All other stiffened elements | b/t |
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9 | Round HSS | D/t |
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*Case Cases 1, 2, 3, and 4 are Unstiffened Elements. Cases 5, 6, 7, 8, and 9 are Stiffened Elements. |
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The limit state of flexural buckling is applicable for axially loaded columns with doubly symmetric sections, such as bars, HSS, and round HSS, and I-shapes, and singly symmetric sections, such as T- and U-shapes. Flexural buckling is the simplest type of buckling.
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The compressive strength of the elements is determined according to the axial force acting from the section center of gravity. According to the regulation, the flexural buckling limit state is considered in all compression elements, regardless of cross-section properties.
First of all, local buckling control should be done. The calculation is made to determine whether the elements are compact or non-compactnoncompact.
Torsional Buckling Limit State
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