In such a connection as girder No. 2 to girder No. 1, it is neces sary to use bolts, as there is no way of riveting. In the case of the connections of beams to girders Nos. 2 and 3, rivets might be used by separating the two beams forming each girder and sliding the framing of each outside bay over on the wall far enough to get in between the beams of girders to hold the rivets. After all the beams had been riveted up, the whole frame could then be moved back into position, and the girders bolted up. Such an operation would be expensive, as it would require considerable extra moving of the beams. In general, bolts through webs of both beams would be used. If the connection was very heavy or the greatest possible number of bolts barely sufficient for the load, turned bolts should be used. In this case, the holes should be punched in. smaller than the diameter of the rivet, and then reamed to a diameter in. larger than the rivet so as to remove all ragged edges; the bolts would be turned down to a true diameter, the exact size of holes, for their whole length.
Fig. 19S shows the detail of girder No. 1. This girder receives a terra cotta arch on each side and as the girder beams are deeper than the floor beams, angles must be used to receive the arch. These angles have to be cut to clear the connection angles on the beams framing in, however. The separators must be spaced so as not to interfere with the rivets in the shelf angles.
The student should carefully study every detail shown in the preceding cuts, and should thoroughly understand every feature of them and every note, and the reason for all the special features ap pearing in them. He should work out for himself all the measure ments given by the details so that he will understand these and know just how to proceed in other cases.
1. Make a shop detail of a 10-in., 25-lb. beam, 12 ft. long, resting S in. on a brick wall at each end and having holes for anchors at each end, and holes for tie rods in the center.
2. Make a shop detail of a 12-in., 40-lb. beam, 15 ft. long, framing into a 15-in., 42-lb. beam flush on bottom at one end and into an 1S-in., 55-lb. beam 1 in. below the top at the other end. The 12-in. beam has holes for three S-in., 18-lb. beams with standard connections spaced equally throughout the length, center to center, between girders.
3. Make a shop detail of a 9-in., 21-lb. beam with a 4 X 3 X t in. angle riveted to the beam the full length. This angle to be placed with the horizontal leg clown and as near the bottom of the 9-in. beam as possible, and the 4-in. leg to be out. The beam rests on a wall 8 in. at each end and it is 13 ft. 9 in. between walls.
4. Make a detail covering channels No. 7 and No. 8, shown in Fig. 199.
5. Make a detail of channel No. 17 in Fig. 199.
6. Make a detail of channel No. 10 in Fig. 199.
7. Make details covering the 5 to S-in. beams, and the 14 to 17-in. beams in Fig. 208.
There are five main features in the detailing of a column.
1. The base or foot of the column.
2. The shaft or the line members composing the column.
3. The cap or top of the column.
4. The connections for other members to the column.
5. The bill of material required to make up the completed column.
A column detail is of necessity more complicated than a beam detail and may at first appear so confused as to be unintelligible. If the student will bear in mind, however, these five features and take each by itself, it will soon become clear.
Details of Base. The character of the base or foot of the column depends upon what it rests. If this is the first section of the column, it will generally rest on a cast iron ribbed base, or a plain steel or cast iron plate. It is the duty of the designer and not of the draftsman to determine which one of these will be used.
Fig. 224 shows a detail of a foot of a column resting on cast iron ribbed base. The base is always designed so as to take the load of the column by direct bearing between the line members and the top of the base, and the angles which are riveted to the column are intended simply to hold it in position in the base.
If a plain cast iron plate is used, a connection similar to the above would generally be used, because in this case the load would be light and the plate thick enough to withstand the upward pressure without spreading the foot of the column. Such plates must be cal culated in the same way explained for bearing plates under beams. See Part page 96. The projection of the plate beyond the shaft is exposed to bending just as the plate under a beam is where it pro jects beyond the flange.
If a steel base plate is used, this is generally riveted to the col umn and the load then must be spread out beyond the lines of the shaft by vertical plates or angles, called shear plates or angles, so as to avoid an excessive bending moment. The size and shape of this plate are determined by the area required to properly distribute the load on the masonry and the direction in which the foot can be most readily spread by means of the shear plates and angles. The thickness of the plate is determined by the same formula as before used for cast iron and bearing plates; generally it is or 1 in. thick. The projection is the distance beyond the edge of the shear -plate, or the outstanding leg of the shear angle.