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.
Figs. 121 to 126 show types of connections of beams to girders and columns. Connections to girders are nearly always of these standard forms, which are the Carnegie standards. In certain cases, individual shops have forms that vary slightly from these, but not to any great degree. It is essential to use the standard form wherever possible because these connection angles are always kept in stock, and the shop work of laying out and punching the material is thereby much simplified. Conditions of framing sometimes arise requiring special connections, but these should always be avoided if possible. In the smaller shops, an extra charge is generally made for coping beams so that where practicable, without increasing the cost of other portions of the work, it is better to frame beams far enough below girders to avoid this coping. The larger shops, however, are so equipped that this coping does not involve an extra operation, and a beam that must be cut to exact length, and has framing angles, can be coped without extra charge.
Connections of beams to columns where they frame centrally with the columns are of the general type shown by Figs. 95 to 105. The exact size of angles varies somewhat with the column section, because the riveting in the framing angles must conform to the spacing required for punching the members of the column. If the beams frame into the column eccentrically, no standard forms can be followed, but each case must be treated individually. Plate and box girders framing into other girders are generally connected by angles riveted to the webs, because ordinarily the depths of the girders will not allow shelf angles underneath. Where such girders frame to columns, however, it is better to use shelf angles with stiffener angles, or shear angles as they are generally called, because this facilitates the erection by providing a seat upon which the girders can rest when swung into position, and also because side connections would cause bending stresses in the column, as noted on page 112.
Column Caps, Bases and Splices. Where heavy girders or a number of beams come over the top of a column, the column section should be made up of such shapes and of such size that the metal of the column comes as nearly as possible under the metal of the beams or girders. If the girder has stiffener angles over the bearing, as it generally does, shear angles should be put in the column directly underneath. The webs and stiffener angles of the girders or beams should not bear on an unsupported cap plate, but this cap plate should be well supported by shear plates or angles. The above is illustrated by Fig. 127.
5PECIAL C0NNECTION -3 BEAM GIRDER OVER TOP OF COLUMN.
Column splices are not ordinarily designed to carry the full load of the upper section through the splice to the lower section. Such design would result in splices of considerable length, which in some cases would be difficult to arrange and always expensive. The general practice is to have the top of the section below and the bottom of the section above the joint planed to a true surface so that there will be a perfect bearing between them. If this is done, the load is transmitted from section to section by direct compression just as in the body of the column. However, the splice should be designed to give the column the full strength of the uncut section as regards stiffness against lateral deflection. As the splice is near the floor beam connections, where the column is braced laterally, this can generally be easily accomplished. Types of column splices are shown by Figs. 128 and 129.
Fig. 129. TYPES OF COLUMN JOINTS.
Fig. 130 illustrates a connection to column of a beam located eccentrically with regard to the column.
Such connections require an extra number of rivets in addition to those required for the direct load in order to resist the tendency to rotation due to the eccentricity.
Some of the special types of framing which occur are shown by Figs. 131 to 140.
Where a beam comes below another beam, as shown in Figs. 131 and 132, a connection such as shown can be used. If the load coming on the hanger is such as to require something stronger than a channel, a simpler connection will result by using two channels spread far enough for the connection plate to be riveted between, as shown by Fig. 132, instead of a beam.
A three-beam girder framed to another beam is shown in Fig. 133. The inside beam can have angles on each side of the web. This beam must be placed before the outside beams in order to make this connection. Unless the three beams are spread a considerable distance apart, the outside beams can have an angle on only one side of the web; this angle therefore should be a 6"x6" angle in order to get the same number of field rivets as with two standard angles.
Fig. 134 shows a beam dropped below the the top of a 24-inch beam girder to which it is framed. With these large size girders it is often impossible to make a connection so that the beams will frame flush with the girder.
Figs. 135 and 139 show changes in the position of standard framing angles on the sides of webs of beams of different sizes framing on opposite sides of the same girder. These changes are necessary in order to use the same holds for both connections and to keep the connections standard.