When designing a compact section in steel beam design according to the American Institute of Steel Construction (AISC) specifications, there are several requirements that need to be considered. Here are the key requirements for a compact section design:
- Compactness Criteria: A compact section is defined as one in which the stress distribution is approximately fully plastic. This means that the shape of the cross-section should be such that it can develop its full plastic moment capacity without significant local buckling or distortion.
- Flange Local Buckling: The compact section should be able to resist local buckling of its flanges. The AISC specification provides specific limits on the width-to-thickness ratios (b/t) for the flanges to ensure they remain compact. For rolled sections, the flange width-to-thickness ratio (bf/tf) and the flange slenderness ratio (bf/√(E/Fy)) are considered.
- Web Local Buckling: The compact section should be able to resist local buckling of its web. The AISC specification provides limits on the web height-to-thickness ratios (h/tw) to ensure that the web remains compact. The web slenderness ratio (h/√(E/Fy)) is considered for rolled sections.
- Compactness Classifications: The AISC specification provides three compactness classifications for rolled sections: Compact (C), Non-compact (NC), and Slender (S). The classification depends on the values of the flange width-to-thickness ratios (bf/tf) and the web height-to-thickness ratios (h/tw) for the given section.
- Lateral-Torsional Buckling: The compact section should also be able to resist lateral-torsional buckling, which is a combination of lateral bending and torsion. The AISC specification provides guidelines for calculating the unbraced length of the beam and the required moment capacity to resist lateral-torsional buckling.
It is important to consult the latest version of the AISC specification and design codes for detailed requirements and design procedures, as they may be updated over time.
