Page 39 - ZSi-Foster Product Catalog

Column - Design Fundamentals

Columns are structural members that are loaded parallel to their length. Support Conditions - Pinned Top –
Most columns are vertical and are used to carry loads from a higher level to
a lower level. However, any member subjected to compression loads, such Fixed Bottom Introduction
as a diagonal or prop brace, is a column. The top is restrained against lateral movement (translation)
A column fails by “buckling”, which is a sudden loss of straightness and but is allowed to rotate. The bottom is restrained against
subsequent collapse. Allowable column load is dependent on: rotation and lateral movement.
(a) The length of column This is a common support condition and is used to K=0.80 Channel
construct the allowable column load applied at the Slot
(b) The type of loading
Face tables.
(c) The support conditions
(d) The column’s cross-sectional shape and material.
Column Length Channel Nuts & Hardware
The column length is measured from braced point to braced point. A braced
point is where the column is restrained from lateral movement (translation) Support Conditions - Pinned Top –
in all directions. Pinned Bottom
Column Loading – Concentric Loading Both ends are restrained against lateral movement
Loads applied to the center of gravity of the column cross-section are (translation) but, are allowed to rotate. General Fittings
considered concentric. A beam that passes over and rests on the top of a
column is an example of concentric loading. K=1.00
Column Loading – Eccentric Loading
Any load which is not concentric is eccentric. The amount of eccentricity (in Brackets
inches) has a major effect on the load-carrying capacity of any particular
column. A load that is transmitted to a column using a standard fitting bolted
to the slot face, is considered eccentric.
The load tables give allowable loads for both concentric (loaded at C G ) Beam Clamps
and certain eccentric (loaded at slot face) loading. Allowable loads for other Support Conditions - Fixed / Free Top –
eccentric loading must be determined by a qualified design professional. Fixed Bottom
Support Conditions The top is restrained against rotation, but is allowed to move
laterally. The bottom is restrained against rotation and lateral
Based on the support conditions, an appropriate "K" value is selected. This Pipe & Conduit Supports
“K” value, which mathematically describes the column end conditions, is movement (translation).
used in the column design equations. The most common support condition K=1.2
combinations are as follows:
Support Conditions - Fixed Top –
Fixed Bottom Electrical Fittings
Both ends are restrained against rotation and lateral Cross-Sectional Shape
movement (translation).
The cross-sectional shape of a column member determines the value of its
“Radius of Gyration” or "r". In general, a member with a large "r" makes a
K=0.65
better column than a member with a small "r". Each axis of a column has Spring Steel
a different "r". Typically the axis with the smallest "r" determines the final
design.
Concrete Inserts

Rooftop Supports

Technical Data

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