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.
After all the spacing in the cover plates has been determined, it may be necessary to change it slightly in order to allow for better spacing in the connection plates, but it is common practice to make the connection plates conform to the spacing in the cover plates since by so doing the additional cost of templets for the horizontal legs of angles is saved; and although a few additional templets for connection plates may be required the saving is considerable.
Cover Plates. The actual lengths required are given on the stress sheet, but when the preliminary layout is made and the material ordered, the plates are ordered longer in order that they will at least be the required length when they are on the girder. The cover plates should be stopped so that the last rivet is 1 1/2 inches from the end, and in the case of double-gauge angles this rivet must be on the outer gauge, see Fig. 76. The single gauge is to be recommended, providing sufficient rivets can be gotten in. At the ends of the cover plates it is not necessary to give the distances to the edges. The dimensions should go on as in Plate VIII and Fig. 76. The material notation should be put on as shown, all cover plates on both top and bottom, which are of the same section and length, being listed at the top. Any plate which is special to the bottom, is listed there.
The beginner should be careful to note that the bottom cover plate next to the flange angles does not run the entire length of the girder, and accordingly he should not run his rivet spacing in the bottom flange through to the end but should stop at the end of the cover plate. This is a common error for beginners.
Cross Frames. The cross frames may be detailed as shown in Plate VIII or as shown in Fig. 77. A layout of the plates must be made; the working point being taken at the intersection of the angle gauges, as in Fig. 77, or at some point which is approximately in the line connecting these points, see Plate VIII. The latter method has the advantage in that it allows the point to be so chosen that the ends of the diagonals will be about 1/4 inch from both the stiffener and the top angle, thus making a smaller plate. The bevels are not stated on the diagonals since the dimensions are given directly.
The end distances should be given or, if not, a note stating their value should be on the sheet. The distance, intersection to intersection and end hole to end hole, should always be given, likewise the distance to the center of any group of holes. The rivet spacing may then be measured from these points. It was formerly customary to give the distance a, Fig. 77, but it is unnecessary and it is not now put on the drawing. Attention is called to the detailing of the diagonals in C. F. 1, the center line being half way between the gauges and a rivet placed on it at the ends.
Fig. 77. Detailing of Cross Frames.
Rivet clearances should receive close attention. The first rivet in the horizontal leg of the top and bottom struts should be at least 1 1/4 inches away from the edge of the cover plate, and it and all others should so stagger with those in the vertical flange that the field rivets may be driven. In case the frames are as in Plate VIII, the clearances of the rivets should be looked after and the spacing in the cover plates be so arranged as to have one rivet on the gauge of the angle.
In cases where there is not a cover plate or where the cover plate is thin, the tie may, on account of its being notched 1/2 inch, press down on the rivet heads of the cross frames. This may be avoided either by cutting out the tie or by placing fillers as shown in Fig. 77. Since the tie is notched at 1/2 inch and the head of a 7/8-inch rivet is | inch, then the cover plate thickness added to that of the angle must be at least (1/2+5/8) = 1 1/8 inches before a filler is required; and the thickness of the filler required in any case is t = 1 1/8"-8 where s is the sum of the thicknesses of the cover plate and flange angle, or flange angle alone in case there is no cover plate. Of course no filler is required at the bottom. All intermediate cross frames should be alike, and the end cross frames should be like each other. In Plate VIII, the angles are 7/8 inch and the first cover plate 9/16 inch, the sum being (7/8 + 9/16) = 1 7/16 inches, which is greater than 1 1/8, no filler is required.
The top angles should have their horizontal leg detailed with the cross frame. This will save many dimensions on the lateral systems when they are detailed.
Lateral Systems. The lateral systems should be detailed in place whenever possible.
All the panels of the lateral systems should be of the same length. If this is not possible, the shortest panels should be at the ends. It is seldom possible to make all the panels equal when a rolled-steel masonry plate is used. In case of the cast-steel pedestals, the dimensions of the top may be so chosen as to have all the panels of the lateral system equal. This will make the lengths of all angles with the same sized legs on connection plates equal.
The angles may be detailed as shown in Plate VIII or as in Fig. 78. In either case the distance between intersections and between end holes must be given. The rivet spacing is measured back from these reference points, being determined from the layout of the plate. The distance from the working point out to the first hole should be given. The end distance should be given or else noted somewhere else. The plate should, when a double-gauge line is used, be made to take in both rows of rivets; however, as mentioned before, the double-gauge line should only be used when unavoidable.
The working point should be in the center of the web and on the gauge line of the stiffener angle when the method used in Fig. 78 is used, except in cases where a splice is used in the center of the girder, and then the intersection or working point should be at the center of the girder, see Fig. 73. All of the methods, Plate VIII and Figs. 78a and 78b, are in common use. The author prefers those shown in 78b or Plate VIII. Sufficient clearance should be between the cross frame and stiffener, see Fig. 78b.