Creosote and creosote solutions have low volatility. They are practically insoluble in water, and thus are most suitable for severe exposure, contact with ground or water, and where painting is not a requirement or a creosote odor is not objectionable. Oilborne chemicals are organic compounds dissolved in an approved petroleum carrier oil, and are suitable for outdoor exposure or where leaching may be a factor, or where painting is not required. Depending on the type of oil used, they may result in relatively clean surfaces. While there is a slight odor from such treatment, it is usually not objectionable. Waterborne inorganic salts are dissolved in water or aqua ammonia, which evaporates after treatment and leaves the chemicals in the wood. The strength of solutions varies to provide net retention of dry salt required. These salts are suitable where clean and odorless surfaces are required. The surfaces are paintable after proper seasoning. See also Art. 4.36. (Design of Wood-Frame Structures for Permanence, WCD No. 6, American Forest & Paper Association, Washington, D.C.) Fire-retardant treatment with approved chemicals can make wood highly resistant to the spread of fire. Although wood will char where exposed to fire or high temperatures, even if it is treated with a fire retardant, chemicals will retard transmission of heat and rate of destruction. Treated with adequate quantities of an approved chemical, wood will not support combustion nor contribute fuel to a fire and will cease to burn after the ignition source is removed. The fire retardant may be applied as a paint or by impregnation under pressure. The latter is more effective. It may be considered permanent if the wood is used where it will be protected from

Bumper. A device other than a buffer for stopping a descending car or counterweight beyond its bottom terminal by absorbing the impact. Car. The load-carrying element of an elevator, including platform, car frame, enclosure, and car door or gate. Car-Door Electric Contact. An electrical device for preventing normal operation of the driving machine unless the car door or gate is closed. Car Frame. The supporting frame to which the car platform, guide shoes, car safety, and hoisting ropes or hoisting-rope sheaves, or the plunger of a hydraulic elevator are attached. Car Platform. The structure on which the car and its floor are mounted. Car Switch. A manual operating device in a car by which an operator actuates the control. Control. The system governing the starting, stopping, direction of motion, acceleration, speed, and retardation of the car. VVVF Control. A method of controlling the smooth starting and stopping of alternating-current motors, utilizing solid-state, variable-voltage, variablefrequency controls. This system is displacing dc motors for medium and highspeed

p Lag screws Wood screws Nails or spikes For full design value 8D 7D 12D Minimum p 4D 4D 6D Cd p/8D p/7D p/12D *D
fastener diameter. TABLE 10.33(a) Metal-Side-Plate Factors for Shear-Plate Connectors* Species group Cst 10.14.7 End-Grain Factor Woods screws, lag screws, nails, and spikes are used in two types of connections, withdrawal and lateral load. In withdrawal connections, the load is applied parallel to the length of the fastener. In laterally loaded connections, the load is applied perpendicular to the length of the fastener. Either type of connection is weaker when fasteners are inserted in the ends of a member, parallel to the grain, rather than in the side grain. Withdrawal Design Value. Wood screws, nails, and spikes should not be loaded in withdrawal from end grain. Tests show that splitting of the wood member causes erratic results relative to those for withdrawal from side grain. When lag screws are loaded in withdrawal from end grain, the nominal withdrawal design value should be multiplied by the end-grain factor Ccg
0.75. Lateral Design Value. When lag screws, wood screws, nails, or spikes are inserted, with the axis in the direction of the wood grain, into the end grain of a main member, the nominal design value for lateral loading should be multiplied by the end-grain factor Ccg
0.67. 10.14.8 Metal-Side-Plate Factor For timber rivets and 4
shear plates, larger design values are permitted when metal side plates are used in lieu of wood plates. For 4-in shear-plate connectors, the nominal design value for load parallel to grain P should be multiplied by the appropriate Cst given in Table 10.33(a). The values depend on the species of wood used in the connection, such as group A, B, C, or D listed in the NDS. Table 10.33(b) outlines metal side plate factors for timber rivet connections. *For 4-in shear plates loaded parallel to grain. For components of each species group, see the groupings in the NDS. 10.14.9 Diaphragm Factor A diaphragm is a large, thin structural element that is loaded in its plane. When nails or spikes are used in a diaphragm connection, the nominal lateral design value should be multiplied by the diaphragm factor Cdi
1.1. 10.14.10 Toenail Factor For such connections as stud to plate, beam to plate, and blocking to plate, toenailing is generally used. The NDS recommends that toenails be driven at an angle of about 30
with the face of the stud, beam, or blocking and started about onethird the length of the nail from the end of the member. For toenailed connections, the nominal lateral design values for connections with nails driven into side grain should be multiplied by the toenail factor Ctn
0.83. 10.14.11 Adjustments for Fire-Retardant Treatment For connections made with lumber or other wood products pressure-treated with fire-retardant chemicals, design values should be obtained from the company providing the treatment and redrying service. The load-duration factor for impact does not apply to such connections. The National Design Specification for Wood Construction, American Forest & Paper Association, contains design provisions and design values for bolts with diameters up to 1 in conforming to the ANSI/ASME Standard B18.2.1. Bolt design values in the NDS apply to connections that have been snugly tightened and to connections that have loosened due to shrinkage of the wood components. Following are some important NDS requirements for bolts: Bolt holes should have a diameter from 1/32 to 1/16 in larger than the bolt diameter. In establishment of design values, careful centering of holes in main members is assumed. Tight fit of bolts in the holes, requiring forced insertion, is not recommended. A metal plate, strap, or washer (not smaller than a standard cut washer) should be placed between the wood and bolt head and between the wood and the nut. The length of bolt threads subject to bearing on the wood should be kept to a practical minimum. Two or more bolts placed in a line parallel to the direction of the load constitute a row. End distance is the minimum distance from the end of a member to the center of the bolt hole that is nearest to the end. Edge distance is the minimum distance from the edge of a member to the center of the nearest bolt hole. Figure 10.12 illustrates these distances, the spacing between rows, and the spacing of bolts in a row. NDS requirements are listed for minimum end distance in Table 10.34, for minimum edge distance in Table 10.35, and for minimum spacing between rows and between bolts in a row in Table 10.36. The geometry factor C discussed in Art. 10.14.5 is applied to the design value for a bolted connection when the end distance or spacing between bolts is less than that given in these tables for full