Intermediate Columns

Column

In structural engineering, column is a vertical structural element which transmits the weight of the structure above to the structural elements below through compression. For the purpose of earth quake engineering and wind, the column is designed to resist the lateral forces. It is used to support the beam in which the upper part of the wall or ceiling gets supported. In olden days, columns were constructed of stone some columns were made out of single piece of stone by turning on a lathe machine. Normally, single piece columns are among the heaviest stone that are used in architecture. The classical columns encompass the entasis (slight outward curves in the sides) and reduction in diameter along the height of the column. At present the columns are constructed out of steel, precast concrete, or brick, and then it will be clad in an architectural covering or left uncovered.  What is an intermediate column?

Intermediate columns

The compression members such as column are mainly subjected to the axial forces. Therefore the principle stress in the compression member is normal stress.

σ = F / A

The Euler formula describes the critical load for elastic buckling and is valid for long columns. The compression of the column material is not geometry related and is valid for short columns. The role of the geometry and stiffness becomes more and more important, when a compression member becomes longer. For the long column, before the stress reaches the strength of the column material, buckling occurs.  This kind of situation is called inelastic buckling. For example, pushing on the end of the bookmark can easily reproduce the buckling. Kneeling will occur for an intermediate column, before the buckling.

The failure of the compression member has to do with the strength and stiffness of the material and the geometry of the member. Depends on these factors compression member is considered short, intermediate, or long.

The design of intermediate columns

Until F.R. Shanley published his logically correct paper in 1946, both the tangent modulus theory and reduced modulus theory were the accepted theories of inelastic buckling. The critical load of the inelastic buckling is a function of the transverse displacement.  According to the shanley theory, the critical load is located between the critical loads predicted by the tangent modulus theory (the low bound) and the reduced modulus theory (the upper bound).The difference between shanley theory and the tangent modulus theory are  not significant enough to justify the much more complicated formula in practical applications. Thus the intermediate columns design deals with.

Questions:

• What does the classic column includes?
• What is intermediate column?