General remarks - The ideal column - The practical column - Variation of modulus of elasticity - Transverse stress : examples - Conditions of end connections : flat ended, round ended, pin ended - Experiments on columns of wrought iron and steel - Wrought-iron rectangular bars and hollow tubes, flat ended - Wrought-iron rectangular bars, pin ended - Influence of size of pins - Tests of wrought-iron riveted columns, flat and pin ended - Table of results - Analysis and remarks - Mode of failure - Weakness at ends of columns - Weakness of component parts of columns - Buckling between rivets - Maximum pitch of rivets compared with plate thickness - Lattice members of columns - Minimum scantlings - Experiments on compressive resistance of various sections - Angles and tees, flat ended - Angles and tees, hinged and round ended - Channels, joists, welded tubes/and Zed columns, flat ended - Channels, joists, and tubes, hinge ended - Wrought-iron latticed columns, pin ended - Mild steel angles, flat ended - Hard steel angles, flat ended - Diagrams of results of formulse proposed by various authorities - Practical sections of columns and struts - Elementary forms - Flat bars - Angles - Tees - Channels - Channels in combination - Rolled joists - Rolled joists in combination - Built-up sections of various types - Zed-iron sections in combinations - Combinations of channels and joists - Special sections - Phoenix columns - Secondary attachments - Comparison of sections - Relative economy and efficiency - Relative amount of riveting - Relative accessibility for painting - Caution in the preparation of working drawings for columns - Check on proportion of length to diameter - Practical examples of riveted mild steel columns - Procedure with respect to the continuity or otherwise of columns in various floor lengths - Buildings of several stories - Theatre auditorium - Skeleton steel construction in very lofty buildings - Massive columns for engine-house construction carrying travellers and tanks - Variations in type - Columns for machine-shops and engineering works - Complex columns of this type carrying traveller roads and roofing - Foundations to columns - Holding-down bolts - Lateral stability - Special cases for concrete foundations of lofty buildings - Precautions to be observed in the fixing of foundation bolts.

Consistently with the principle adopted throughout these notes, the theory of the strength of columns, as viewed from a mathematical standpoint, will not be entered upon. This subject has been frequently dealt with by numerous and able writers, and the student is referred to their works for further information on this branch of the subject.

The ideal column or strut is perfectly straight, is subjected to a purely compressive stress in the direction of its length, while the compressing force is usually assumed to be truly axial; the modulus of elasticity of the material of which the column is composed is also supposed to be uniform not only in every cross-section, but in every part of a cross-section.

The practical column of everyday experience falls short, however, in a considerable degree from all these ideal conditions, notwithstanding the care with which the designer may have striven to realize them. His column is, it is true, as straight, perhaps, as ordinary workmanship can ensure, but the modulus of elasticity of his material may vary slightly not only in every separate cross-section, but even in different portions of the same cross-section, a physical fact which may, in the life history of the column, determine incipient flexure and perhaps the direction in which that flexure may extend towards the goal of ultimate resistance and failure if the loading be carried to this extent.

So far, again, as the axial direction of loading is concerned, the practical column is often, from the very conditions of the design, exposed to transverse stresses arising either from the bending moment set up by eccentric loading, or even from its own weight, as in the case of inclined struts, such as sheer legs or the jibs of cranes. Vertical columns may also be subject to severe transverse stress where exposed to wind pressure, as, for example, in columns supporting large roofs, or forming the supports of lofty sheds or other buildings. The cast-iron piles of a marine jetty may be instanced as an example where the transverse stresses set up by the force of waves may perhaps be more important than the vertical loading they are called upon to endure. In many cases these transverse stresses have, as far as possible, to be foreseen and allowed for, and the absence of such a provision may, as in the case of crane jibs of considerable radius, have serious results arising from cross strains imposed upon them, let us suppose, by the exigencies of erection or repair.

In addition to the above may be stated the risks of transverse shock, as in the case of columns exposed to wheeled traffic, or to loads piled up against them in such manner as to cause bending stresses in addition to the vertical loading to which they are subjected. In short, it is not too much to assert that the possibilities of transverse stress in any column should be always present to the mind of the designer, and will go far in guiding his judgment in the determination of that always important point, viz. the ratio of diameter or least dimension to length, and to which further reference will be made.

The ideal column may further be supposed to be either flat ended, round ended, or pin ended, and theoretical deductions have been drawn as to the mode of failure of columns of a certain length under each of these conditions.

But in practice it is not always easy in many cases to assert with confidence under which of the above heads a column or strut should be classed, and, as we shall see in the experiments about to be described, neither pin-ended nor flat-ended columns invariably fail in the mode in which it might be reasoned that they should do.