In cases of buildings of several stories, where the column is considerable height, in segments of the various floor spaciugs, and where the accumulation of load on the lower columns is heavy, a sound judgment would lead to the conclusion that the continuity of the column is of the first importance, and that all details of girder connections should be made to give way to it. Such a case might be conceived to arise in the columns supporting the various box and gallery tiers in a theatre auditorium, and where the safety of the audience demands that the utmost care be taken in the design of all column details. Even in this case the continuity of the column has not in practice always been preserved, although by the use of divided girders carrying the box tiers and forming the projecting cantilever portions, this desirable end could easily be secured.

Another illustration of the importance of column continuity is found in the very lofty structures erected on the principle known as skeleton steel construction, as commonly practised in the United States. Here the consideration of transverse stresses due to wind pressure, and the necessity of preventing lateral flexure or oscillation, leads to very careful consideration of the column connections, and the best practice demands as much continuity of the column members as can be practically attained, the girder seatings being as a rule bracketed off the columns.

We may have, then, two leading ideas which point to the desirability of column continuity, the accumulation of vertical loading, and the possibility of lateral flexure or oscillation in the building as a whole.

Figs. 187, 188 give details of the base of a column of similar type to the foregoing, i.e. of girder section, of the type shown in Fig. 162. In this case no cast-iron bed-plate is used, the base of the column being arranged to bear directly upon concrete or stonework.

We may next examine the details of a massive column of the type shown in Fig. 166, used in the interior of an engine-house, and supporting a heavy load arising from two lines of traveller girders, together with the load of girders and cast-iron tank above, the details of which are considered on pages 158 to 171.

It will be seen from Figs. 189 and 190 that at the level of the capping or bracketing supporting the traveller girder, the column is gathered in, and reduced in section to the dimensions shown on Fig. 191, which is a plan of the top of the traveller girder seatings looking down. The upper column is of the same type of section as the lower portion, and possesses great stiffness in all directions. Fig. 189 is a front section on the line E of Fig. 191, and Fig. 190 is a section on the line DD of Fig. 191.

It will be observed that the traveller girder seatings are borne, as it were, upon the shoulders of the lower portion of the column, while the continuity and rigidity of the column as a whole is well maintained.

The clearance between centre of traveller rail and face of column is 9 inches, less the projection of the rivet heads (see the remarks on this detail in Chap. III., p. 137), a clearance which is sufficient for the type of traveller used in this instance.

The normal section of the lower portion of the column below traveller girder seatings is shown in Fig. 192, and of the upper

Fig. 187. Scale ½ inch = 1 foot.

Fig. 188. Scale ½ inch a 1 foot.

Note

The holding-down bolts to this column are four in number, 1½" diameter, with flat bar washer plates 1" thick, and portion in Fig. 194, the side elevation and plan of cap to upper portion of column being shown in Figs. 195, 196.

3½" diameter washers, as shown in detail in Figs. 179, 180, p. 226.

In columns of this type, where the height is considerable, it is sometimes desirable to introduce plate and angle stiffeners, similar to the stiffeners in the web of an ordinary plate girder, for the purpose of preventing distortion or flexure in the outer corner angle irons. This detail is shown in Figs. 192, 193.

A column performing similar functions to the one last described, and of similar type, is shown in Figs. 197 to 205.