Columns summary - Columns Columns can be roughly devided...

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Columns Columns can be roughly devided into the following three categories : 1-Short compression blocks or pedestrals : If the height of an upright compression member is less than three times its least lateral dimensions,it may be considered to be a pedestral. 2-Short reinforced concrete columns : Should a reinforced concrete column fail due to initial material failure,it is classified as a short column.we think of a short column as being a rather stocky member with little flexibility. 3-Long or slender reinforced concrete columns : As slenderness ratios are increased, bending deformations will increase , as will the resulting secondary moments . if these moments are of such magnitude as to significantly reduce the axial load capacities of columns, those columns will be referred to as being long or slender.When a column is subjected to primary moments, the axis of the member will deflect laterally, with the result that additional moments equal to the column load times the lateral deflection will be applied to the column. These latter moments are called secondary moments. Types of columns: A plain concrete column can support very little load, but its load-carrying capacity will be greatly increased if longitudinal bars are added. When providing lateral restraint for these longitudinal bars further substantial strength increases may be made. Under compressive loads, columns tend not only to shorten length wise but also to expand laterally due to the Poisson effect. The capacity of these members can be greatly increased by providing lateral restraint in the form of closely spaced ties or helical spirals wrapped around the longitudinal reinforcing. Reinforced concrete columns are referred to as tied or spiral columns, depending on the method used for laterally bracing or holding the bars in place.
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If the column has a series of closed ties, it is referred to as a tied column , these ties are effective in increasing the column strength by preventing the longitudinal bars from being displaced during construction, they also resist buckling outward under load. Tied columns are ordinary square or rectangular. If a continuous helical spiral made from bars or heavy wire is wrapped around the longitudinal bars, the column is referred to as spiral column . Spirals are even more effective than ties in increasing a column’s strength. Composite columns are concrete columns that are reinforced longitudinally by structural steel shapes, which may or may not be surrounded by structural steel bars, or that may consist of structural steel tubing filled with concrete( Lally columns). Axial load capacity of columns: In actual practice there are no perfect axially load columns. It has been known for several decades that the stresses in the concrete and the reinforcing bars of
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Columns summary - Columns Columns can be roughly devided...

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