placed against the beam so as to fill up the space between the strap and the beam. 8. Templates. Where iron wall girders rest on masonry templates are provided under the ends of such girders to uniformly distribute the pressure. The sizes of templates required by the Code are as follows: For girders over 12 ft. span, stone templates 10 inches thick. For girders under 12 ft. span, stone templates 5 inches thick. For lintels over 6 ft. span, stone templates 5 inches thick. For lintels under 6 ft. span no template is required, but each end must bear 5 inches on the wall. Steel plates of equal strength may be used instead of stone templates. In addition all wall bearing beams must have iron or stone templates and wall anchors, except beams less than 6 inches in depth when spaced not over 30 inches centre to centre. Steel templates should be well grouted, so as to bind well to the masonry. The sizes generally used are as follows: For 3, 4, 5 and 6 inch beams, 6x6x38. For 7 and 8 inch beams, 8x8x2. For 9, 10 and 12 inch beams, IOXI0x58. For 15, 18, 20 and 24 inch beams, 12x12x34. Where larger size templates are required, grillage beams with separators may be used instead of templates to distribute the load on the masonry. All templates must be placed flush on edge with the inner face of the wall, as in Fig. 17a. Where the plate is placed too far in, the iron beam upon deflecting may crush the wall at the inner edge. See Fig. 17b. When the templates are rectangular and of sufficient thickness, they should be placed with their longer edge along the inner edge of the wall. In some cases box girders with a wide bottom plate are used. These plates can not be considered as equivalent to templates, no matter how much they bear on the wall. A template when well set forms part of the wall and sticks to it, thus tending to uniformly distribute the load over the pier area. This template does not deflect with the girder, as shown in Fig. 17c, which represents the side elevation of a box girder made of two 10 inch beams and two 1⁄2 inch plates. On the other hand, if the template is omitted the bottom plate of the girder will deflect with the girder and will bring a concentrated load along the very edge of the wall, as in Fig. 17b. 9. Usual Defects in Templates: Omitting templates. Using stone templates of less thickness than required by the Code. Placing the templates inside the wall and beyond the inner edge of the wall. Placing templates too low and raising the end of the girder to the proper level by means of wood or slate wedges. Using small templates and thus overloading the masonry. Using thin templates, which tend to bend under the super-imposed load. Using cracked and otherwise defective stone templates or cast iron. plates. When the templates are too low the difference should be made up by using thin steel plates on top of the original low plates, and of the same length and width as the main template. Or the template may be raised to the proper elevation by means of small wooden wedges forced underneath and the space under the template filled in with good cement mortar. When this has set sufficiently the wedges are pulled out and the openings thus left are filled in with grout. No load should be placed upon the steel template until the mortar underneath it has completely set. 10. Wall Anchors. The main purpose of wall anchors is to secure greater stability for the walls. There is a large variety of anchors used for the purpose and some are shown in Fig. 17. A good anchor must have a large area in contact with the mortar, hence the round anchor shown in Fig 17d is commonly used. This anchor is made of a 34-inch round bar and should be about 12 inches long. It is often specified in government work and is also known as a government anchor. The plain bolt anchor, Fig. 17e, is easily obtainable. The bolt anchor and riveted anchor have the advantage that, being once put in place, they can not be removed by other mechanics. as easily as the so-called government anchor before the masons brick these anchors in. Anchors which are not put in ahead of time by the iron setters are liable to be left out by the masons. Fig. 17f shows a 34-inch round anchor sometimes employed in connection with beams used in pairs. The riveted two-angle anchor shown in Fig 17g is especially good for sidewalk beams; they tie the street retaining wall to the main building and can not be removed before bricking in. The common wall anchor, Fig. 17h, should be used in all cases when the iron work is about 12 inches or more from the outside face of the wall. Not less than 4 inches should be allowed between the anchor and the face of the wall. This is the anchor commonly used in tall buildings, and is usually made of a 3/4-inch bolt with a 6x6x5/16 plate. Fig. 171 shows an excellent form of through wall anchor. The 3/4-inch bolt passes through the whole thickness of the wall and is provided on the outside with either an iron star or a large washer. In alteration work, whenever a wall is broken into for the purpose of resting an iron beam on same, it is good practice to disturb the old work as little as possible. Hence in such cases the double-angle anchor, either riveted or bolted, is preferable. Little advantage is gained, however, in such work with any kind of an anchor, as upon patching up the wall around the beam in general only the patchwork will stick to the beam and anchor, while the main wall will adhere very little to the new material unless unusual care and good workmanship are secured. Under such conditions, if the building is only a few stories in height, and when the wall is not an xterior wall, a straight beam end without an anchor, resting on the wall and surrounded with good Portland cement mortar and brickwork, may be found preferable... STORE FRONT ALTERATIONS INVOLVING This is a very common form of store front alteration. Instead of resting the front wall girders on party walls or on brick piers, the two ends of these girders rest on top of columns of iron or steel. The columns must be of the right weight and size, must be plumb and straight. They must rest on base plates of dimensions approved in the original plan. They must be bolted on top with not less than four 3/4-inch bolts in each column. The beams must agree in size and weight with the approved plans; must have separators not further apart than 5 feet centre to centre, and must be well strapped. All ironwork must be painted before and after erection. The common defects mentioned in relation to beams in the previous chapter are often found, also, in these alterations. In addition, we shall mention faults found in columns and their connections: 1. Lightweight iron. Iron heavier than called for in the approved plans, but the shapes and materials are contrary to approved- plans. For instance: Using built-up columns instead of Bethlehem columns. Using standard beams for columns instead of Bethlehem columns of equal weight. This is one of the most dangerous changes when made without first figuring out the load that can be safely carried by the new columns. To make this point clearer consider the following figures: An 8 inch Bethlehem column weighing 32 pounds per foot is good for 55 tons when 12 feet long. A 6 inch round cast iron column 3/4-inch metal, weighing 39.2 pounds per foot, is good for 66.4 tons when 12 feet long. A 5 inch round cast iron column 34-inch metal, weighing 31.7 pounds per foot, is good for 52 tons when 12 feet long. A 12 inch standard I-beam 31.5 pounds per foot is good for 32.1 tons when 12 feet long. It is easily seen what might happen when a 6 inch cast iron column is replaced by an 8 inch Bethlehem steel column, or when a 5 inch cast iron column is replaced by a 12 inch standard steel beam. 2. Steel plates and stone blocks under the bottom of the column are defective, of smaller area and less thickness than required in the approved plans. 3. Omitting plates on top of open back cast iron columns. These plates make the load more uniformly distributed and shall not be omitted. They are required by the Building Code. 4. Erecting unpainted columns and placing brickwork around same before painting. 5. Using bolts less than 34-inch diameter in the top flanges of columns in connections of beams to columns. Using less than four 3/4-inch diameter bolts in the top flanges of cast iron columns, same being contrary to the Code. 6. Using 5%-inch bolts in defective 13/16 holes instead of reaming out the holes and using 3/4-inch bolts. 7. Leaving out part or all the bolts. α Fig. 18-Columns and Straps. a, 8x10x1 in. cast iron column supporting two 12 8. In some cases second-hand cast iron columns without top flanges have been used. The lack of flanges can be remedied by an arrangement shown in Fig. 18a. A steel knee angle with one line of through bolts and one line of tap bolts may be used. A plate is put on top and then the beams are drilled to fit and are bolted with 3/4-inch bolts. The diagram shows a column next to an adjoining wall. Other columns may have one steel knee angle on each side. 9. The steel or iron columns may be out of plumb; the steel beams may project beyond the party line. All beams projecting beyond the party line should be cut short and all columns shall be plumb. The beams on top of the iron columns are strapped to the wood joists as before stated. If the work is done right |
