Bituminous saturated cotton fabric is stronger and is more extensible than bituminous saturated felt but is more expensive and more difficult to lay. At least one or two of the plies in a membrane should be of saturated cotton fabric to provide strength, ductility, and extensibility to the membrane. Where vibration, temperature changes, and other conditions conducive to displacement and volume changes in the basement are to be expected, the relative number of fabric plies may be increased. The minimum weight of bituminous saturated felt used in a membrane should be 13 lb per 100 ft2. The minimum weight of bituminous saturated woven cotton fabric should be 10 oz/yd2. Although a membrane is held rigidly in place, it is advisable to apply a suitable primer over the surfaces receiving the membrane and to aid in the application of the first mopped-on coat of hot asphalt or coal-tar pitch. Materials used in the hot-applied system should meet the requirements of the following current ASTM standards: Creosote primer for coal-tar pitchD43 Primer for asphaltD41 Coal-tar pitchD450, Type II AsphaltD449, Type A Cotton fabric, bituminous saturatedD173 Woven burlap fabric, bituminous saturatedD1327 Treated glass fabricD1668 Coal-tar saturated feltD227 Asphalt saturated organic feltD226 The number of plies of saturated felt or fabric should be increased with increase in the hydrostatic head to which the membrane is to be subjected. Five plies is the maximum commonly used in building construction, but 10 or more plies have been recommended for pressure heads of 35 ft or greater. The thickness of the membrane crossing the wall footings at the base of the wall should be no greater than necessary, to keep very small the possible settlement of the wall due to plastic flow in the membrane materials. The amount of primer to be used may be about 1 gal per 100 ft2. The amount of bitumen per mopping should be at least 41/2 gal per 100 ft2. The thickness of the first and last moppings is usually slightly greater than the thickness of the moppings between the plies. The surfaces to which the membrane is to be applied should be smooth, dry, and at a temperature above freezing. Air temperature should be not less than 50
F. The temperature of coal-tar pitch should not exceed 300
F and asphalt, 350
F. If the concrete and masonry surfaces are not sufficiently dry, they will not readily absorb the priming coat, and the first mopping of bitumen will be accompanied by bubbling and escape of steam. Should this occur, application of the membrane should be stopped and the bitumen already applied to damp surfaces should be

44,000 k 234
k/F(h/ t)2 F yw y Web Stiffeners. Transverse stiffeners are required if the web shear strength without stiffeners is inadequate, if h/ t  418/
F , or if h/ t does not meet the re- yw quirements of Eqs. (7.30) and (7.31). Where stiffeners are required, the spacing of stiffeners should be close enough to maintain the shear within allowable limits. Also, the moment of inertia Ist, in4, of a transverse stiffener should be at least that computed from I  at3j (7.42) st where j  2.5/(a/h)2  2. The moment of inertia for a pair of stiffeners should be taken about an axis through the center of the web. For a single stiffener, Ist should be taken about the web face in contact with the stiffener. In addition, for design for tension-field action, the stiffener area Ast, in2, should be at least that computed from Fyw Vu A  0.15Dht(1  C )  18t2  0 (7.43) st F v  V ys u n where Fys  specified yield stress of stiffener, ksi Vu  required shear strength at stiffener, kips, calculated for the factored

* Current criteria typically requires higher levels of ventilation air. Lights may be assumed to average 4 W/ ft2. Assume 50 persons will be in the store, 2 in the first-floor office, 10 in the second-floor office No. 1, and 5 in secondfloor office No. 2. Cooling Measured in Tons. Once we obtain the cooling load in Btu per hour, we convert the load to tons of refrigeration by Eq. (13.15). Cooling Requirements for First-Floor Store (Table 13.15a). Load in tons 7.25 tons If supply air is provided at 18
F differential, with fresh air entering the unit through an outside duct, the dehumidified air flow required for sensible heat is [from Eq. (13.30)]: TABLE 13.15b First-Floor Office Load Btu/hr Heat gain through enclosures: North wall, 102  0.25  15 382 North glass, 18  1.04  15 281 Partition, 30  0.39  10 117 Floor, 79  0.25  10 198 2 occupants (sensible load) at 255 510 Lights, 79  4  3.42 1080 Fan hp 4% 103 Total internal sensible load 2671 Fresh air (sensible load) at 2 changes per hour, 32  1.08  15 518 Total sensible load 3189 Occupants (latent load), 2 at 255 510 Fresh air (latent load), 32  0.67(99
77) 473 Total latent load 983