(9) Detail the bed (masonry) plate separately, never show it in connection with the base plate.
At least two sheets are necessary to complete the detail draw ings of any girder span, viz, (1) the Floor, Masonry, and Erection Plan, Plate VII, and (2) the Girders and Bracing, Plate VIII, although in many cases the information on this sheet is put on two sheets, the girder on one and the bracing on the other. The first sheet should show: (1) A cross-section of the floor.
(2) A longitudinal view of the floor.
(3) A side elevation of the floor.
(4) The angle of skew and the width of the bridge seat.
(5) The elevation of the bridge seats and the grade of base of rail.
(6) The marking diagram.
(7) All clearances.
(8) Other essential information.
In the marking diagram all members which are entirely alike should be given the same mark. It may be, and usually is a fact, that all marks can not be put on the marking diagram until the detail drawing is done since then and only then is it possible, especially with the plates, to determine all members which are alike. Only those members which are shipped loose are given a mark. Thus it is seen that while each connection plate has a mark, only the entire cross-frames are given one mark since the members which compose them are all shop-riveted together. "Other essential information" is seldom required. In this special case there is shown another track which it is proposed will be put in in the future. Another case is where each end of the span has a different height from the base of rail to the masonry. In such cases this should be shown.
On this sheet should be shown the masonry plates, and if the ends are supported on cast-steel bases the height of these and also the dimensions of the base should be given.
The following general rules apply to the second sheet, Plate VIII.
(1) At the top of the sheet show a top view of the span with cross-frames, laterals, and their connections complete, the girders being placed at their proper distances apart.
(2) Below this show the elevation of the far girder from the inside, with all field holes in the flanges and stiffeners indicated and blackened in.
(3) If the span has lower lateral bracing, show below the elevation a horizontal section of the span just above the tops of the lower flange angles. On this drawing show the lower lateral bracing.
(4) Cross-frames shall, whenever possible, be detailed on the right hand of the sheet in line with the elevation. The frame shall be of such a depth as to permit it being swung into place without interfering with the heads of the flange-rivets in 1 he girders.
(5) Always use a plate, not a washer, at the intersection of the diagonals of cross-frame.
The various parts of Sheet 2, Plate VIII, will now be taken up in detail and described and commented upon.
The Webs. As a usual thing webs are never specified in frac tions of an inch. If so, the next inch in width must be ordered and then after the flange angles are riveted on, the projecting portion is cut off—an expensive operation. Webs are ordered in even inch widths and the distance back to back of angles is made 4 inch or inch greater than the width of the web plate. This is sufficient to prevent any irregularities in rolling from projecting above the flange angles. Some engineers favor the web planed down from the greater width and claim that the of the web on the sole or base plate thus obtained is a great advantage. The advantage is slight, however, and unless specially instructed to detail it that way, it should not be done. The web splices should, as before men tioned, be at a panel point of the lateral system. In some cases the web plates butt up against each other, being planed to an even bear ing. In most cases, however, the ends of the webs are sheared off and the customary 1-inch clearance is allowed. In this case the sum of the lengths of the webs as given is 2 (25'4")+23'-51"= 75'-91", while the "overall" distance is 73'-10" or 4 inch less, which is taken up by the distance between webs at the splice and by the small amount, 8 inch, which web is below the backs of the angles at the ends. This shows the webs to be 4 inch apart at the splices. It is unnecessary to place any dimensions or notes on the drawing calling attention to this fact since the shop will make this allowance unless instructed otherwise. In case the webs are to be close together, a note must be placed on the drawing at the splice, reading "Webs planed to even bearing." Web Splices. Web splices may be of two forms, viz, that as indicated on Plate VIII which takes shear only, and the moment web splice. The proper manner to detail a moment web splice is as shown in Fig. 71. In the simple shear splice both the splice stiffeners and the splice plates may and should have the same spacing as the intermediate stiffeners, and the rivet lines should be spaced so as to correspond to the spacing in the flange angles. In the moment splice this should be done if possible, but this is seldom the case. However, in case of more than one splice occurring in half of the girder, they should all be made alike, being figured for the one with the greater stress. Since a splice plate is a species of filler, it should be given a mark so that in case of other splices occurring the mark and not all the dimensions should be placed upon it.