The section which comes on top of this one has 5-in. angles, in order to use standard spacing in these angles, therefore, the spac ing in splice plates has to be on a special gauge and this place is beveled to give a neater appearance when the two sections are riveted together. Fig. 218 gives the bill of material.
Fig. 219 gives the detail of an angle over an opening resting in a wall at one end and framing to a beam at the other. The holes in the horizontal leg are for securing the frame of the window. As this angle has framing on one end only it is not reversible and there fore for the wall on opposite side of the building the angle must be made "opposite hand" or reversed.
Fig. 220 gives the detail of a spandrel girder and shows in out line the relation of the stone facing to the girder. This wall section is a pier and the width of it is indicated by the length of the S-in. channel at the right-hand end. At the opposite end the wall is only a covering for the column and is carried on the column. This channel supports the block surrounding it, which in turn supports the mass of stone above; the course below is hung by anchors, to the S-in. chan nel. The channel is supported by brackets from the beams which are detailed separately for clearness, although they are shipped riveted to the beam. The connection A runs back to the column. There are two floor beams framed to the girder, but as the space between center of beams is 11 in. there is sufficient room to drive rivets passing through only one beam, and this is preferable, there fore, to using through bolts.
Note the specification "Ship ". This means that the two beams are not bolted together for shipment.
Fig. 221 gives the detail of a cast iron base for a plate and angle column having a 12-in. web. The outlines of the members of the column shaft should be carried down by similar outlines in the cast iron base. In this case the box of the base is H-shaped and the centers correspond to the centers of the shaft members. The thick ness of this box under the column must be sufficient to early the whole load of the column without exceeding the safe compressive strength of cast iron. The size of the base depends upon the area
required to distribute the load on the footing. The purpose of the ribs and base is to resist the tendency to break, due to this uniformly distributed load on the footing. Failure would generally occur through the bending action of the of the base projecting beyond the box. The moment on this may be figured as for a beam fixed at one end and free at the other and loaded uniformly with the load per unit of bearing surface.
Taking one rib and the base half way on each side between the next rib would give a section at the box, which may be taken as the fixed end, similar to Fig. 222. Calculate then the position of the neutral axis and figure the moment of inertia of the section about this axis. Having determined the bending moment for the width between the ribs, the fiber stress in tension and compression can be 1\ I I found by the formulas used in calculation of beams. / - where M is the bending moment in inch pounds, f/ the distance from the neutral axis to the extreme fiber, and I the amount of inertia.
A section must of course be assumed at the outset and it may be necessary to modify this to come within the requirements. It is necessary also to calculate the stresses at the most unfavorable sec tion, and to see that there is sufficient metal across the corners to prevent cracking diagonally between the foot of the ribs on adjacent sides.
Different sections of columns require, as previously stated, different sections of box under the column, and this would affect the arrangement of the ribs more or less. These ribs in general should be at an angle of 45 or GO degrees. In some cases lower bases can be used, but these are of course subject to greater bending strains.
1. Given a 12-in., 311-lb. beam framed to a column at each end, the distance between faces being 12 ft. 21 in. The beam has two 7-in., 15-lb. I-beams framed on one side and opposite these in each case is a 12-in., 311-1b. I-beam. The distance from center of con nections to the face of the column at each end is 3 ft. 5:1 in. 'Make a shop detail of the 12-in. girder, all beams being flush on top.