This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
The student should now become familiar with detailing from a framing or setting plan. Fig. 199 shows such a plan upon which is all the information necessary to detail the different members. The information given on such a plan is taken from the various general plans of the building. This framing is designed for a terra cotta arch except the portion having 6-in. beams which is under a sidewalk. These beams, therefore, are on a pitch indicated by the arrows and the figures .375 which is the pitch in inches per foot.
The detail of these 6-in. beams is given in Fig. 200. Note that at the right-hand end is shown in outline the girder to which they frame, to indicate that it copes on a level with this girder. Note also that as the web of this girder is vertical while the beams pitch, the framing angles have to set on a slope with reference to the axis of the 6-in. beam, which slope is given always by a triangle of measurements, one side of which is 12 in., and the other side inches or fractions. Never use decimals for this slope on the details as the men at the shop are used to working only to inches and the nearest sixteenth. On a plan it is well to give the slope in decimals, for if it is a fraction over or under a sixteenth, in a long slope some error might result in calculating the difference in grades unless the exact decimal was used.
The length of these beams is fixed by the measurement from the center of the girder to the face of the wall and the bearing of the beam on the wall. This bearing is generally 8 in. or more. The allowable pressures on masonry are given in Part I, and by computing the reaction on the wall, the proper bearing to give can be determined. For the smaller sizes of beams a method would give a result less than 8 in., but this should be used in such cases where possible.
The connection holes for beam No. 5 are on a pitch with reference to the axis of the beam, since the webs of beams No. 7 and No. 8 set vertically.
The tie rod holes are dimensioned on the detail but not on the plan. These holes are rarely spaced on the plan, but must be on the details. The measurements are such as to follow what is indicated by scale on the plan and avoid any other holes or connections such as connections for beam No. 7. Tie rod holes should be shown in groups of two, even if only one rod bolts to the beam, as in the case of channel No. 2.
Fig. 201 shows the detail of channel No. 9. This channel receives the ends of the terra cotta arch along the back and so it is necessary to rivet an angle on the bottom for the skewback of the arch to rest upon. Note that this stops a little short of each end in order to clear the connection angle at one end and the faces of the wall at the other. If the connection angle did not interfere, it would be well to run this as far as the flange of No. 15, and cut it to give, say 3/8 in. clearance from this flange. Note the connection holes at the left-hand end for a 9-in. channel have a standard connection. Where the beam or channel is set before the brick wall is carried up, this of course can be done; if the wall is already in, it would be necessary to use an angle on one side only.
There is 1 in. from the center of the holes for the connections to the upper edge of the 3 X 3-in. angles. The connection angles for these beams come on the inside of the 16-in. channel and clearance for driving the rivet on the back is all that is required here. If the beams were framed to the back of channel, this angle would have to be cut each side of the connection.
Fig. 202 shows the detail of beam No. 11 which frames to beam No. 9 at one end, and at the other end comes on a lintel at such a grade that the beam cannot be framed to the lintel, and owing to the small depth of the lintel, it is not possible to put a shelf angle on to receive the end of the 9-in. beam. The most practicable way, therefore, is to cut the 9-in. beam and rivet on angles which will bear directly on the top of the lintel beams. These angles have generally either a 6-in. leg or a 5-in. leg in order to contain sufficient rivets to take the reaction of the beam at this end. In this case, the cut being small as regards the depth of beam, there is sufficient web area along the inside edge of these angles to provide for the shear. If the beam had been a deeper one, and the end reaction much larger, this might not have been the case. The shear angles would then extend back to the uncut portion of the beam far enough to provide rivets to carry whole reaction to the angles, and the same number of rivets would be required in the portion over the bearing area. In general, this construction which is shown by Fig. 136, in Part II, should be followed. The holes in the horizontal legs of these angles must be spaced to agree with the holes in the flanges of the lintel beams, and are determined by the spacing of these beams and the standard gauge in the flanges. Note that 5/8-in. rivets are the maximum which can be used in the flange of a 7-in. beam, and that the holes for tie rods are not in the center of the beam. The position of such holes varies; sometimes they are specified to be near the bottom of the beam. At other times where different size beams are used, as in this case, the spacing is such as to approximate the centers of all.
Fig. 203 shows the detail of the lintel beams to which beam No. 11 connects. The table on page 44, Cambria Handbook, gives the standard spacing for double beams. These spacings cannot always be followed. In this case the beams are spread more so as to bring the flanges nearer to the outside faces of the wall which rests upon them. Separators are always placed at ends over the bearings and at varying distances, center to center, as noted in Part II.