The detail of connection of floor beams to girder is made special because of the awkward relation of beams to girder flanges, which relation could not he changed; only a single angle could be used for the connection if this was to be riveted on, and this had to be shipped riveted to girder rather than beam. It would have been possible to have a double-angle connection by using an intermediate plate and two side plates; but this would have added to the expense of erection, and sufficient rivets for the reaction were obtained by the single angle.
It will be noted that some rivets near these connections are shown flattened in the bottom flange to clear the flange of beams; also, in the elevation, some rivets are shown countersunk to clear the angle con nection. Rivets are also shown countersunk where the cover-plates are left off, because there is not room to extend the plate beyond the last rivet without interfering with the next rivet. All such cases of countersinking or flattening rivets to avoid stiffeners or ends of flange plates, are to be avoided wherever possible, as they are objectionable and expensive. They can generally be avoided by changing the rivet spacing somewhat at such points. In the case shown in Fig. 260, the girder is such a heavy one, and the rivet spacing so close, that it was better to countersink rather than have the wide spacing otherwise necessary.
The end view shows open holes for riveting angles to the main column angles as shown in Fig. 261. This practice is objectionable for light girders, as previously noted in Part II, and where it is possible to properly brace the girder and column connection in any other way. In the case of a heavy girder such as this, where the deflection would be slight, it ,is not so objectionable, especially if these rivets are not driven until after the columns are carried up and the dead weight of construction is put upon the girder.
The bill of material should be carefully followed through as illustrating points previously mentioned.
Fig. 263 shows a single web-plate girder which carries the wall section over an entrance doorway, and also a column line on its canti lever end.
The center lines of the supporting column and of the column above, are shown on the plan of bottom flange. Fig. 264 shows the girder in its relation to the stonework, and the method of securing same to the girder.
The stiffeners G are arranged to come directly over the line mem bers, and the shear angles on column below. The stiffeners A, E, and F are similarly arranged with respect to the column above carried on the end of the girder. It will be noted that this girder is not sym
metrical about its center line, and therefore the detail of the whole girder is shown. It should be noted also that the concentration of loading at one end makes it necessary to increase the web greatly to provide for the shear. For this reason a 1-inch plate is riveted on each side over the flange angles and carried to a point beyond the cen ter of column bearing where the area of the web alone is sufficient for the shear. This end being the point of maximum moment, also, is the reason for the increased flange area here.
Floor beams frame to this girder in the same relation as in the case of the three-web girder shown in Fig. 260; but as this is only a single web, the connection angles can be riveted to the beam. As the beam must be cut to clear the bottom flange angle, this necessi tates a filler between the web and the connection angles on beam.
Note that where brackets or similar riveted members °cot,' on a girder, it is better to give a separate section for the details of riveting of these members. The end view, and sections A, B, C, and D, show the details for these brackets supporting the stonework, and show the various details necessary to conform to the position and spacing of stiffeners on the girder.
In a girder loaded as this is, there should be sufficient area in each set of stiffeners coming under the column above and over the supporting column, to provide for the shear; and these stiffeners should be fitted to top and bottom flanges.
Make a complete shop detail, at a scale of inch to 1 foot, of a single-web plate girder 30 feet long clear span, resting on a brick wall at each end and carrying a load of 60 tons distributed as shown in Fig. 255 T:le web-plate is 30 inches by *, inch; both flanges have the same section, and each is made up of two angles 5 x x inch (long leg horizontal), and two cover-plates 12 inches by inch. A 15-inch 42-pound beam frames to the girder on each side in the position indi cated by loads. The top of the beams is 11 inches below the back of the flange angles. The beams are to rest on suitable shelf angles, with shear angles beneath, and have side connection angles riveted through web of girder to brace them laterally. Determine proper number of rivets and character of these connections. Determine number and spacing of stiffeners required. Use in addition stiffeners just one side of each beam connection.