Question

HOW DO YOU DETERMINE IF A SECTION IS COMPACT OR NON COMPACT ACCORDING TO SLENDERNESS LIMITS

Answer 1

The cross sectional shape of the compression members are divided as compact, non-compact, or slender. It is done based on the ratio between the breadth and thickness of the plate members. All cross sections of the compression member can be divided solely based on the type of steel used and dimension of the cross section.

The slenderness ratio is major factor that influences the flexural capacity of the braced beams. If a beam has very small slenderness ratio, it is called as compact section. The section with small slenderness ratio can attain its plastic moment at the time of loading. This cross section is classified as compact.

For the members with larger slenderness ratio, the compression web or flange buckles before it attains the plastic moment capacity. The cross section is classified as noncompact. For the sufficiently larger slenderness ratio, the local buckling cause the failure before the yield stress of the material is reached. The cross section is classified as slender.

The strength compact section is limited by the material strength, which is compressive and it is based on the yielding in limit state. If the member has lateral support continuously and is compact, or if the length of unbraced section is short, the nominal strength of moment, Mn is equal to the full plastic capacity of moment Mp.

The compact shapes cross sections satisfy the following width-to-thickness ratio requirements for the web and the flange.



Here, the term bf is flange width, tf is thickness of the flange, h is total depth, tw is web thickness, E is modulus of elasticity, and Fy is yield strength