Concrete insulation serves well for column protection, in that it gives additional stability to the steel section. Also, it is useful where abrasion resistance is needed. Concrete, however, is not an efficient insulating medium compared with fireresistant plasters. Normally, it is placed completely around the columns, beams, or girders, with all reentrant spaces filled solid (Fig. 7.64a). Although this procedure contributes to the stability of columns and effects composite action in beams and slabs, it has the disadvantage of imposing great weight on the steel frame and foundations. For instance, full protection of a W12 column with stone concrete weighs about 355 psf, whereas plaster protection weighs about 40 psf, and lightweight concretes made with such aggregates as perlite, vermiculite, expanded shale, expanded slag, pumice, pumicite and sintered flyash weigh less than 100 psf. Considerable progress has been made in the use of lightweight plasters with aggregates possessing good insulating properties. Two aggregates used extensively are perlite and vermiculite. They replace sand in the sanded-gypsum plaster mix. A 1-in thickness weighs about 4 psf, whereas the same thickness of sanded-gypsum plaster weighs about 10 psf. Typical details of lightweight plaster protection for columns are shown in Fig. 7.64b and c. Generally, vermiculite and perlite plastic thicknesses of 1 to 13/4 in afford protection of 3 and 4 h, depending on construction details. Good alternatives include gypsum board (Fig. 7.64d and e) or gypsum block (Fig. 7.64). For buildings where rough usage is expected, a hard, dense insulating material such as concrete, brick, or tile would be the logical selection for fire protection. For many buildings, finished ceilings are mandatory. It is therefore logical to employ the ceiling for protecting roof and floor framing. All types of gypsum plasters are used extensively for this dual purpose. Figure 7.65 illustrates typical installations. For 2-h floors, ordinary sand-gypsum plaster 3/4 in thick is sufficient. Three- and four-hour floors may be obtained with perlite gypsum and vermiculite gypsum in the thickness range of 3/4 to 1 in. Instead of plastered ceilings, use may be made of fire-rated dry ceilings, acoustic tiles, or drop (lay-in) panels (Fig. 7.65d and e). Another alternative is to spray the structural steel mechanically (where it is not protected with concrete) with plasters of gypsum, perlite, or vermiculite, proprietary cementitious mixtures, or mineral fibers not deemed a health hazard during spraying (Fig. 7.66). In such cases, the fire-resistance rating of the structural system is independent of the ceiling. Therefore, the ceiling need not be of fire-rated construction. Drop panels, if used, need not be secured to their suspended supports. Still another sprayed-on material is the intumescent fire-retardant coating, essentially a paint. Tested in conformance with ASTM Specification E119, a 3/16-inthick coat applied to a steel column has been rated 1 h, a 1/2-in-thick coating 2 h. As applied, the coating has a hard, durable finish, but at high temperatures, it puffs to many times its original thickness, thus forming an effective insulating blanket. Thus, it serves the dual need for excellent appearance and fire protection. Aside from dual functioning of ceiling materials, the partitions, walls, etc., being of incombustible material, also protect the structural steel, often with no additional assistance. Fireproofing costs, therefore, may be made a relatively minor expense in the overall costs of a building through dual use of materials. Some buildings require recessed light fixtures and air-conditioning ducts, thus interrupting the continuity of fire-resistive ceilings. A rule that evolved from early standard fire tests permitted 100 in2 of openings for noncombustible pipes, ducts, and electrical fixtures in each 100 ft2 of ceiling area. It has since been demonstrated, with over 100 fire tests that included electrical fixtures and ducts, that the fire-resistance integrity of ceilings is not impaired when,

Table 9 Brick estimator Brick Dimensions Number of Bricks 230 x 110 x 76 48.5 230 x 110 x 119 32.3 230 x 110 x 162 24.3 290 x 90 x76 38.8 290 x 90 x 90 33.3 290 x 90 x119 25.8 290 x 90 x162 19.4 305 x 90 x 76 36.9 305 x 90 x 162 18.5 Design Considerations Brick Technical Manual 77 5.7 Brick Coursing Heights 3000mm 2700mm 2400mm 2100mm 1800mm 1500mm 1200mm 900mm 600mm 300mm 3000mm 2700mm 2400mm 2100mm 1800mm 1500mm 1200mm 900mm 600mm 300mm 50mm 76mm 90mm 119mm 162mm Design Considerations Brick Technical Manual 78 5.8 Brick Gauge 5.8.1 230mm Long Bricks No. of Length Opening Bricks (mm) (mm) No. of Length Opening No. of Length Opening No. of Length Opening Bricks (mm) (mm) Bricks (mm) (mm) Bricks (mm) (mm) Design Considerations Brick Technical Manual 79 5.8.2 290mm Long Bricks No. of Length Opening Bricks (mm) (mm) No. of Length Opening No. of Length Opening No. of Length Opening Bricks (mm) (mm) Bricks (mm) (mm) Bricks (mm) (mm)

Cold-formed shapes invariably cost more per pound than hot-rolled sections. They will be found to be more economical under the following circumstances: 1. Where their use permits a substantial reduction in weight compared to hotrolled sections. This occurs where relatively light loads are to be supported over short spans, or where stiffness rather than strength is the controlling factor in the design. 2. In special cases where a suitable combination of standard hot-rolled shapes would be heavy and uneconomical. 3. Where quantities required are too small to justify the investment necessary to produce a suitable hot-rolled section. 4. In dual-purpose panel work, where both strength and coverage are desired. Cold-formed shapes are usually made from hot-rolled sheet or strip steel, which costs less per pound than cold-rolled steel. The latter, which has been cold-rolled to desired thickness, is used for thinner gages or where, for any reason, the surface finish, mechanical properties, or closer tolerances that result from cold-reducing is desired. Manufacture of cold-formed shapes from plates for use in building construction is possible but is done infrequently. 8.1.1 Plate, Sheet, or Strip The commercial distinction between steel plates, sheet, and strip is principally a matter of thickness and width of material. In some sizes, however, classification depends on whether the material is furnished in flat form or in coils, whether it is carbon or alloy steel, and, particularly for cold-rolled material, on surface finish, type of edge, temper or heat treatment, chemical composition, and method of production. Although the manufacturers classification of flat-rolled steel products by size is subject to change from time to time, that given in Table 8.1 for carbon steel