73. In which One of the following classes of steel section premature buckling is occurred before yield is reached.1 pointClass IClass IIClass IIIClass IV

The question pertains to the classification of steel cross-sections based on their buckling and yield behavior.

Classification of Steel Sections

1. Class I: These sections can achieve their plastic moment capacity before buckling occurs. They are capable of undergoing full plastic deformation.

2. Class II: These sections reach the yield stress but do not reach the plastic moment capacity due to the risk of local buckling. However, they can still be used effectively.

3. Class III: These sections attain yield strength but are limited by buckling. Thus, while they can carry a load, they do not achieve the full plastic moment capacity.

4. Class IV: In these sections, local buckling occurs before reaching the yield strength, which is the focus of the question.

Final Answer

The correct answer is Class IV, as premature buckling occurs before yield is reached in this class of steel sections.