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.
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.
Stiffeners. All stiffeners except the second from the end should have the outstanding leg on the side of the gauge line away from the center of the girder. As a rule, the end stiffeners should have enough rivets to take up the end shear, and the intermediate stiffeners should have sufficient to take up the shear at that point. This would, if carried out, require a different number of rivets in each stiffener. Common practice requires that the spacing in all stiffeners should be the same and that this spacing should be the same as in the end stiffeners. In some cases, such as in heavy girders, it is not possible to do this on account of the large number required in the end stiffeners, and the rivet spacing is then made the same in all the intermediate stiffeners.
The rivet spacing should not exceed 4 3/4 or 5 inches at the most and should be so placed that it should be symmetrical about the center. When the web plates are of even inch width, the 1/4 inch may be put into one odd space at the center in order to avoid § inch in the spacing. It may be necessary to put in a few more rivets than are computed as necessary, but the advantage gained by thus making the punching of the plate on the multiple punch possible, makes this advisable. Fig. 72 shows this method of detailing. In order to make the shear plate at the web splice efficient to some degree in withstanding the moment - for although it is not computed to take moment yet it does in reality
- the rivets near the flange are placed close together for a few spaces. If the space changes after that, it should increase towards the middle of the web, except in such a case as Fig. 72 where the center space may or may not be as great as those on either side of it.
In double-gauge flange angles the rivet in the stiffener should be in the inner guage line of the flange angle as shown, and no rivet should come closer than 1 1/2 inches to the end of a filler.
Each like stiffener should be given a mark and in case others of the same kind both in size and punching occur, the mark may be used instead of the material notation and dimension. Those crimped will be given different mark even if size and punching are the same. It should be noted that some of the stiffener angles differ only from the fact that they have holes in their outer leg to which the cross-frames are connected, hence a different mark.
Fig. 72. Method of Detailing Web Plate Stiffeners.
Fillers. Fillers are placed under angles that are crimped since the angles are only crimped 3/8 inch and not the entire 7/8 inch which is the thickness of the flange angles. The fillers are given marks for the same reasons and in accordance with the same rules that apply to stiffeners.
Flange Angles. In case of double gauge on the 6-inch flange angle it is better to put the 2 1/2-inch gauge on the inside, no matter what the thickness may be, since by this operation the rivets in the horizontal flange, providing that is a double-gauge line, may be more advantageously spaced on account of the fact that the required stagger will be less.
Fig. 73. Method of Detailing Rivet Spacing with Flange Angles.
The rivet spacing in the vertical leg of the flange angles should increase from the end towards the center and should remain the same, as far as possible, between any two stiffeners, any changes necessary being made near the stiffeners. Since a rivet must always be in the inner gauge line at a stiffener, an even number of spaces must be between any two stiffener gauge lines, since the rivets must stagger. This brings one rivet in the center of the girder, which can not occur in case there is a splice at the center of the girder. The stagger may then be broken as in Fig. 73, the stiffener angle being placed as shown and the rivet spacing being symmetrical on each side of the center of the girder.
Between the stiffeners at the end, the spacing should be the same as it is between the next two stiffeners.
The spacing at any point should never exceed the computed spacing unless constructive reasons require it. On account of rivet-driving clearances, a 7/8-inch rivet can not be driven any closer than 1 1/4 inches to another member. Therefore, rivets can not be driven any closer to the stiffener than 1 1/4 inches, see Fig. 74. For this particular sized stiffener, the minimum spacings next to it will be 3f inches and 2| inches as seen in Fig. 74. The rivet-spacing multiplication table, Table X, will be found very helpful in spacing the rivets here.