this will also help keeping the columns plumb. In case of fire, however, the wood joists may burn and the beam straps may become useless. For this reason in good work 3/4 in. round anchors are used, passing through each column every 4 feet or so in height, and then into the side or party wall, as in Fig. 18b. All spaces around these anchors are then filled in with a good cement mortar. One more type of store front construction will be considered. Fig. 19 shows the side and front elevation and the top view of a common show window extending two stories above the ground. The steel frames for such show windows. must be well anchored to the main building. The uprights are usually made of steel angles, which are tied to the main structure by channels or angles. Whenever possible such ties should be bolted to the ironwork of the main building. In the figure, however, is shown a case where no iron work was within reach, and the whole window frame is tied to the front brick wall. The 4 inch channels carry the roof and intermediate floor construction. They are provided with anchors made of 34 inch round bars passing through the wall and through 6x6 steel plates on the inner face of the wall. The other end of the anchor is welded to a 12x3% flat piece, through which two 1⁄2-inch bolts are passed into the 4 inch channels. Or the whole anchor may be made in one piece from a 1 inch round bar. In either case a thread is cut into the anchor and a nut is provided, as shown in the side elevation. As the 4 inch channels carry the roof and floor, steel templates have been provided under their wall-bearing ends. See Fig. 19 Plan. The 3x3 inch angles carry no load except, perhaps, the weight of some window panes. The purpose of these angles is to break up the unsupported length of the main angle uprights and to stiffen the whole frame. These angles form a continuous band all around the steel frame and should be anchored to the wall with clip angles as shown. The main uprights must be properly bolted and provided with a suitable shoe and plate at the bottom. The common defects encountered in this kind of work are as follows: Anchors through wall are omitted, and the floorcarrying channels simply rest a few inches on the brick work. This must not be allowed. Where the anchor strikes into a partition or an interior brick wall the anchor may be placed on a slant, or it may be bent to avoid the partition, if necessary. 2. Omitting templates under floor-carrying beams. 3. Omitting intermediate bracing angles. 4. Defective bolting. 5. Providing no shoe at the bottom of the main uprights. Omitting plate under the main uprights. 6. 7. Using lighter material than called for in the approved plans. 8. Erecting unpainted iron or omitting a second coat of field paint. CHAPTER VIII. Hoisting Iron Work. KINDS OF HOISTS. Before any columns are set in their final position one or more derricks are installed on the premises for hoisting the iron. A hoist is any machine used for raising and lowering weights. There are several kinds of hoists: I. Cranes. A crane is a hoist which in addition to raising the load can also be made to move it in a horizontal direction. (See Fig. 20.) A crane consist chiefly in a revolving vertical post or mast, a projecting jib or boom, and a stay for sustaining the outer end of the jib. The stay may be either a tie or a strut. The post, jib and stay do not change their relative positions. 2. Derricks. A derrick (Fig. 21) differs from a crane chiefly in the fact that the stay is always a tie, consisting of a rope or chain, which may be shortened or lengthened at will, thus raising or lowering the free end of the jib or boom. This in turn revolves about an axis passing through its lower end and attached near the foot of the mast. In a derrick the post, boom and stay change their relative positions. The boom can be made to raise loads vertically at higher elevations than in the case of cranes. For this reason derricks are generally used in hoisting iron in constructions. 3. Shear-poles with guys consist of two masts brought together at the top, and tied at the top with one or more guys (Fig. 22). This device is used for hoisting small loads only. On large jobs steel derricks, with mast and boom made of several sections of angles and lattice work, are generally used. Steel masts and booms are usually over 100 feet long. Wooden masts and booms are of all sizes, generally less than 100 feet in length. A large boom reaches far out into the street and covers a greater range of the building at the same time. The first time a derrick is set on a job the erector will drive five or six iron bars or hooks around the edges of the lot. These hooks are called the dead men, and are used to |
