DESIGNING. 193 



In the latter case column sections are straight between panel- 

 points, these being located upon the arc of a circle or at points 

 of a parabolic curve, according to the fancy of the designer. 

 Straight posts are somewhat cheaper, but the additional cost 

 of the curved outline may be warranted on account of the im- 

 proved appearance and more graceful lines. 



Several years since column sections and formulas of structural 

 engineering underwent careful investigation and analysis. This 

 sharp rivalry for supremacy has produced its natural result, 

 the survival of the fittest, until to-day all column sections are 

 practically eliminated that fail to include standard elements, 

 as I beams, angles, channels, and plates, and the standard- built 

 column of to-day consists of angles latticed, angles and plates, 

 and the latticed double channel, formed either of plates and 

 -angles or the latticed double-channel column. 



The seeming exception to this rule is the Z-bar column, but 

 as with the other discarded column sections, its popularity seems 

 somewhat on the wane judging from the following expression 

 of an experienced structural engineer: "These columns are 

 excellent from a structural point of view, but are somewhat more 

 difficult to use where bevelled connections are required. Further- 

 more, Zee-bar columns seem to be going out of use; just why I 

 do not know, but at the present time the demand for Zee bars 

 is comparatively light, and the result is that the mills do not 

 roll them very often, and there are likely to be serious delays 

 occasioned on work where Zee bars are specified. The quantity 

 of Zee bars required for a water-tower is not sufficient to w r arrant 

 a special rolling. In one case last year we were delayed three 

 or four months for this reason. If the Zee-bar shape is specified 

 for any reason, it can be built of an I beam and two channels. 

 Laced-channel columns are very satisfactory, especially so for 

 the rigid connection at the top referred to above. As all sizes 

 of channels are used in large quantities, there is usually no dif- 

 ficulty in procuring them within any reasonable time." 



