Structural Column Base Plates Engineering Design

Related Resources: civil engineering

Structural Column Base Plates Engineering Design

A column or pillar in architecture and structural engineering is an structural element that transmits, through compression, the weight of the structure above to other structural elements below. For the purpose of wind or earthquake engineering, columns may be designed to resist lateral forces. Other compression members are often termed "columns" because of the similar stress conditions. Columns are frequently used to support beams or arches on which the upper parts of walls or ceilings rest. In architecture, "column" refers to such a structural element that also has certain proportional and decorative features. A column might also be a decorative element not needed for structural purposes; many columns are "engaged with", that is to say form part of a wall.

The area A1, in2 (mm2), required for a base plate under a column supported by concrete should be taken as the larger of the values calculated from the equation cited earlier, with R taken as the total column load, kip (kN), or

Unless the projections of the plate beyond the column are small, the plate may be designed as a cantilever assumed to be fixed at the edges of a rectangle with sides equal to 0.80 b and 0.95d, where b is the column flange width, in (mm), and d is the column depth, in (mm).

To minimize material requirements, the plate projections should be nearly equal. For this purpose, the plate length N, in (mm) (in the direction of d), may be taken as

The width B, in (mm), of the plate then may be calculated y dividing A1 by N. Both B and N may be selected in full inches (millimeters) so that BN > or = A1. In that case, the bearing pressure fp, ksi (MPa), may be determined from the preceding equation. Thickness of plate, determined by cantilever bending, is given by:

where: Fy minimum specified yield strength, ksi (MPa), of plate; and p larger of:

0.5 (N - 0.95d) and 0.5(B - 0.80b).

When the plate projections are small, the area A2 should be taken as the maximum area of the portion of the supporting surface that is geometrically similar to and concentric with the loaded area. Thus, for an H-shaped column, the column load may be assumed distributed to the concrete over an H-shaped area with flange thickness L, in (mm), and web thickness 2L:

where: Fp allowable bearing pressure, ksi (MPa), on support. (If L is an imaginary number, the loaded portion of the supporting surface may be assumed rectangular as discussed earlier.) Thickness of the base plate should be taken as the larger of the values calculated from the preceding equation and