Compression Members:

Structural members subjected to axial compression are called columns or struts. Columns are normally vertical load bearing members in buildings etc., while struts may be inclined or horizontal and usually form part of a roof or bridge truss. The axial compression in columns may be accompanied with bending moments, due to external loads or due to eccentricity of loading (load being not exactly axial). Steel columns might be made of single IS rolled section (simple column) or a combination of more than one such sections (compound or built up columns). Sometimes steel pipes or tubular structures (either hollow or filled up) may be used as columns or struts. Again columns may be short or long, depending upon the slenderness ratio. We have to take special care of failure because of buckling in case of columns. All these are elaborates briefly with special reference to the IS Code of Practice for General Construction in Steel (IS: 800 - 1984), that has been followed throughout as a sound practice.

Objectives

After studying this unit, you should be able to

• Know the behaviour of steel structural members subjected to axial compression,
• Learn about the several modes of failure of such members especially compression and buckling; and limits of permissible compressive stresses,
• Denote the effective length of a column taking into account the support conditions at its ends,
• Study a slenderness ratio of columns and its effect in modifying the permissible compressive stresses,
• Design the several types of compression members (both simple and built-up) and to check their load carrying capacity, and
• Design appropriate connections for these compression members.