In order to illustrate the above principles in regard to spacing when double-gauge lines are used on both legs and the maximum spacing for any particular distance is shown by the rivet curve, an example will be given. Let the stiffeners and the rivet-spacing diagram be as in Fig. 75. This shows the allowable rivet spacing to be 21 inches at the second, 31 inches at the third, and 38 inches at the fourth stiffener, the distance between stiffeners being 6'-71". Let it be required to determine the rivet spacing between the second and fourth stiffeners Since the stiffener angles have a 3-inch leg on the web, the gauge of which is 1 inches, and no rivet can be driven closer to the edge of the leg on the web or to the outstanding leg than 1 inches, no rivets can he driven closer to the gauge than 3 inches and 2.1 inches on the sides of the outstanding leg and the edge of the other leg, respectively, see Fig. 76. Since 3 inches is the minimum distance it must be used at stiffener (2) notwithstanding the fact that the spacing diagram requires not less than inches. This leaves (W-71") —3"=6'41" from that rivet to the one in the gauge at the top of stiffener (3), no attention being paid to 3 inches, the minimum dis tance here, since it is less than the 31 inches required by the diagram.
An odd number of spaces must be used since the last rivet is on the other gauge line; and from the rivet-spacing diagram it is seen that the spacing can not exceed 21 inches until half way between the two stiffeners, and that a space or two of 31 inches would be allowed at stiffener (3).
By consulting Table X it is seen that 29 spaces at 24 inches are equal to W-04". Now (6'-4/")— (6'-01")=3.1" or 15 fourths ep, from which it is seen that if 1 'inch was added to 15 of the 29 @ 21", the result would be all that is desired; but this would leave the last space 21 inches and by Fig. 76 it is seen that it must be at least 3 inches. By making the last space 3 inches, which is 1 inch, or 1 greater than 21 inches, there remain 2S spaces between 15 2 13 rivet a and rivet b, Fig. 76, and only — - — = left. If, there 4 4 fore, 1 inch be added to 13 of the 21-inch spaces, making 13 of 21"+1"=31" each, the spacing will be correct. It is:
In a similar manner the second space between stiffeners has its rivet spacing determined. Here it is seen that the rivet spacing may start at 31 inches, can not exceed inches until past the middle, and can have a few spaces at 31 inches at the stiffener. By Table X it is seen that 24 spaces at 31 inches equal 6'-G". Now (6'71")— (6'-6")= 11" or and if one of the 24 spaces be increased 4 inch and two of them are increased 1 inch the entire a inch will be used up and the spacing will have been completed. It is.
Tn a similar manner almost any combination can be made to fill out any dimension.
The rivets in the horizontal flange of the angle and the cover plate are, when the spacing is greater than 2 inches, placed opposite those in the vertical flanges as is shown in Fig. 70, since according to Table IX, /. being (2r = no stagger is required, and where the spacing is less than 2: inches it is changed so as to he 3 inches or more. In such cases as this it is not necessary to give spac ing in the cover plates, a note, "Spacing same as in vertical legs" or "Spacing same as in web" being all that is required.
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 con nection plates may be required the saving is considerable.
Corer 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 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, pro viding 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. 7G. 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.