Waffle flat plates behave like solid flat slabs with drop panels. Somewhat higherstrength concrete, to avoid the need of stirrups in the joists immediately around the solid head, is usually desirable. If required, however, such stirrups can be made in one piece as a longitudinal assembly, to extend the width of one dome between the 9.91 TABLE 9.21 Commonly Used Sizes of Two-Way Joist Forms Depth, in Volume, ft3 per dome Weight of displaced concrete, lb per dome 3-in top slab Equiv. slab thickness, in Weight* psf 41/2-in top slab Equiv. slab thickness, in Weight* psf 30-in-wide domes 19-in wide domes 3-in top slab 41/2-in top slab Types and Sizes of Forms for Two-Way Concrete-Joist Construction * Basis: unit weight of concrete, w
150 pcf. FIGURE 9.31 Reinforcing bar details for column strips of flat slabs. Details of middle strips are the same as for middle strips of flat plates (Fig. 9.30). FIGURE 9.32 Reinforcing details for column strips of two-way waffle flat plates. B
24 bar diameters or 12 in minimum. Details for middle strips are the same as for middle strips of flat plates (Fig. 9.30). drop head and the first transverse joist. For exceptional cases, such stirrups can be used between the second row of domes also. See Fig. 9.32 for reinforcement details. The ACI 318 Building Code provides for use of beams on the sides of panels, on column centerlines. (A system of slabs and beams supported by girders, however, usually forms rectangular panels. In that case, the slabs are designed as one-way

panel edges At intermediate supports Panel siding APA MDO Exterior APA Rated Siding Exterior 11/32 and 3/8 15/32 and thicker 16e 6d for siding 1/2 in thick or less; 8d for thicker siding. 6e 12 Lap siding APA Rating Siding Lap Exterior 6d for siding 1/2 in thick or less; 8d for thicker siding. 16 along bottom edge 24 along bottom edge a Recommendations apply to all species groups for veneered APA Rated Siding, including APA 303 siding. bNext regular size nailing should be used if panel siding is applied over foam-insulation sheathing. If lap siding is installed over such sheathing up to 1 in thick, 10d (3-in) nails should be used for 3/8- or 7/16-in siding, 12d (31/4-in) nails for 16/32- or 1/2-siding, and 16d (31/2-in) nails for 19/32-in or thicker siding. Nonstaining box nails should be used for siding installed over foam-insulation sheathing. c Hot-dipped or hot-tumbled galvanized steel nails are recommended for most siding applications, but electrically or mechanically galvanized nails are acceptable if the plating meets or exceeds thickness requirements of ASTM A641 Class 2 coatings and is protected by a yellow chromate coating. For best performance, stainless steel or aluminum nails are an alternative. Galvanized nails may react adversely under wet conditions with some wood species and cause staining if left unfinished. Such staining can be minimized if the siding is finished in accordance with APA recommendations or if the siding is protected by a roof overhang from direct exposure to moisture and weathering. d Recommendations of siding manufacturers may vary. e Nails should be spaced 3 in c to c along panel edges for a braced wall section with 11/32- or 3/8-in panel siding applied horizontally over studs spaced 24 in c to c. Where wind velocity exceeds 80 mph, nails attaching siding to intermediate studs within 10% of the width of the narrow side from wall corners should be spaced 6 in c to c. g Stud spacing may be 24 in for veneer-faced siding panels. FIGURE 10.9 Application of structural panels as sheathing. Building paper is not required over the sheathing, except under stucco and brick veneer. TABLE 10.21 Recommended Installation of APA Panel Wall Sheathinga

3. Loading and unloading time (hand truck 25 s, power truck 15 s). Wherever practical, a study should be made of the loading and unloading operations for a similar elevator in the same type of plant. Operation of Freight Elevators. The most useful and flexible type of operation for freight elevators is selective-collective with fully automatic doors. Attendant operation requires an annunciator. When operated with an attendant, the car automatically answers the down calls as approached when moving down and similarly answers up calls when moving up. The elevator attendant, when present, has complete control of the car and can answer calls indicated by the annunciator by pressing the corresponding car button. The addition of fully automatic power-operated doors means the elevator is always available for use, unless taken out of service by the attendant. The standard hoistway door is the vertical biparting, metal-clad wood type. For active elevators and openings wider than 8 ft, doors should be power-operated. Automatic freight elevators can be integrated into material-handling systems for multistory warehouse or production facilities. On each floor, infeed and outfeed horizontal conveyers may be provided to deliver and remove loads, usually palletized, to and from the freight elevator. The elevator may be loaded, transported to another floor, and unloadedall automatically. These may be used in multistory buildings to transport small loads between levels. Generally too small to carry an operator or passenger, dumbwaiters are cars that are raised or lowered like elevators. They may be poweredcontrolled by push buttonsor manually operated by pulling on ropes. Powered dumbwaiters can automatically handle from 100 to 500 lb at speeds from 45 to 150 ft /min. They are available with special equipment for automatic loading and unloading. They also are designed for floor-level loading suitable with cart-type conveyances. The American National Standard Safety Code for Elevators, Dumbwaiters, Escalators and Moving Walks, ANSI A17. 1, contains safety requirements for dumbwaiters. Powered dumbwaiters may be constructed like electric elevators with winding-drum or traction driving machines or like hydraulic elevators. Many of the safety requirements for elevators, however, are waived for dumbwaiters. Standard heights for a dumbwaiter are 3, 31/2, and 4 ft. ANSI A17.1 restricts platform area to a maximum of 9 ft2. Rated load capacity usually ranges from 20 to 500 lb. Like elevators, hoistways should have fire-resistant enclosures. When there is a continuous flow of materials, such as mail or other documents to be distributed throughout a multistory building, conveyer systems may provide an economical supplement to elevators. In some installations, 200 lb or more of paper work and light supplies are circulated per minute. Two types of conveyer systems are employed in commercial buildings. The selective vertical conveyer moves plastic tubs from one floor to another, automatically loading and unloading at preselected floors. The tubs typically are made to carry mail and small supplies and have payloads of up to 50 lb each. A typical selective vertical conveyer installation is similar to an escalator (Art. 16.4). A continuous roller chain is driven by an electric motor. Engaging sprockets at top and bottom, the chain extends the height of the building, or to the uppermost floor to be served. Carriers spaced at intervals along it transport trays from floor to floor at a speed of about 70 ft /min. Another conveyer type, the tracked conveyer system, permits both vertical and horizontal document distribution. This system employs self-powered cars, which travel over a track system that allows switching off at selected station locations (Fig. 16.18). Where a specific floor may have a high volume of traffic, the track may be routed around the floor to one or more remote stations. The destination is programmed at the dispatching station, and the car is automatically switched onto the main track to begin its journey. Cars for this type of conveyer are generally limited to a maximum payload of 20 lb, although some are modified to carry up to 25 lb. The cars travel at about 100 ft /min. FIGURE 16.18 Electric track vehicle system (developed by Translogic Corporation). For vertical track sections, a gear engages a continuous rack on the track for positive control in both the up and down directions. A friction-drive system is employed on horizontal track sections. Shaft-mounted machinery is minimized with the tracked conveyer system. Like elevators, however, vertical conveyers must be enclosed in fire-resistant shafts. Generally, the only visual evidences of the existence of the installation are the wall cutouts for receiving and dispatching runoffs at each floor. In event of fire, vertical sliding doors, released by fusible links, should snap down over the openings, sealing off the conveyer shaft at each floor. Vertical Conveyers. Operation of vertical conveyers is simple. When the tray or car is ready for dispatch, the attendant sets the floor-selector dial or presses a button alongside the dispatch cutout. For the selective vertical conveyer, trays are placed on the loading station, where they are automatically moved into the path of the traveling carriers. Each tray rides up and around the top sprocket and is automatically discharged on the downward trip at the preselected floor. The best place to install a vertical conveyer is in a central location, next to other vertical shafts, to minimize horizontal runs in collecting and distributing correspondence at each level. The choice of conveyer types should be based on the needs of the user. The selective vertical conveyer is appropriate where the required movement is entirely vertical, while the tracked conveyer system lends itself to both horizontal and vertical layouts. Pneumatic Tubes. These are also used to transport small loads within buildings. Units are moved through tubes under air pressure or suction, or both. Items to be transported are carried inside cylinders slightly smaller in diameter than the tubes. In choosing between vertical conveyers and pneumatic tubes, the designers first consideration should be the size of the load to be carried. The traveling cylinder is limited as to the size and weight of the material to be moved. Aside from that, an arterial system of pneumatic tubes may satisfy the requirements of a predominantly horizontal building, whereas a vertical conveyer is generally more advantageous in