The location and position of the main interior columns having thus been fixed, the next thing is to locate any columns whose position is dependent on special features.
?In this case, the corridor arrangement along the side E F at the end near D E makes it necessary to place this column out of the line of the others. On this account and to avoid excessive loads on the girder framing into this column, an extra column is put in the partition between toilet and vent at this end.
In the exterior walls, columns of course have to be placed at each corner and also at the angles in the side A B C D. The other exterior columns naturally are placed at the intersections of office partitions with exterior walls, because here the piers in the walls will be the widest. The distance from the ashlar line to the cen ter of wall columns will vary in accordance with the architectural details illore should never be less than four inches of masonry outside of the extreme corner of column, and, if possible, there should be more.
Better protection is given the steel if the web is parallel with the face of the wall. Where the spandrel beams and lintels are very eccentric, however, this position results in an uneconomical section, since the weakest axis of the column is thus exposed to the greatest bending. Some designers, however, prefer to sacrifice economy in this regard to more efficient protection of the metal.
The columns thus having been placed according to the arrange ment of the typical floor plan, the next step is to see if any changes are necessary to suit the conditions of the floors that differ from this plan, namely, the basement and the first floor. From a glance at the plan of the first floor, it will be seen that two of the columns conic down in the main entrance in such position as to obstruct the passageway. It would be possible to change the posi tion of these columns and make them conform to the first floor partitions. The results in the floors above, however, would not be so good, and therefore additional columns will be provided, sup porting girders at the second-floor level to carry the columns above. A similar provision must be made for the wall column over the entrance.
The position of the columns thus having been determined, the girders follow by joining the centers of columns. The spacing
of the beams will be determined largely by the system of floor arch to be used, except that, unless entirely impossible, a beam should come at each column in order to give lateral stiffness to the frame. If a terra cotta arch is to be used, the spacing should not be much over six feet at the maximum, and an arrangement such as shown would result. If a system of concrete arches is to be adopted, in which spans of eight or nine feet can be safely used, the beams between the two lines of girders on each side of the corridors may be omitted.
Certain other points should be noted in regard to this framing plan, as follows: Columns should not be put at the front of elevators, as they cannot be fireproofed without interfering with the clear space of shaft.
Beams, if possible, should always be fAmed at right angles to girders, as oblique connections are expensive.
Beams should not frame off center of column if a little change in either column or beam can obviate it.
Columns on adjacent and parallel lines should, as far as possible, be opposite each other; that is, a beam framed to the center of one column should also meet the center of the next line of columns.
Spacing and spans of beams should be such as to develop their full strength.
Fig. 45 shows the wall sections and the resulting spandrel sections and wall girders. Not all the points that arise in such a framing can here be brought out; but from the foregoing the gen eral method of treatment of such problems should be clear.
In buildings of a different character, many different and often. more complex conditions will arise. The student, however, must always bear in mind that it is the duty of the designer to grasp fully the architect's details, and so to arrange his framing as to conform in all respects thereto, unless such details can themselves be changed more readily and to better advantage. It is essential for the designer to see not only what has already been determined, but what details will result when certain features are fully worked out ; and in all his work the economy of design and framing, and the efficiency of the framework, should be kept constantly in mind.