Gee & Jenson West Palm Beach, Florida A hazard poses the threat that an unwanted event, possibly a catastrophe, may occur. Risk is the probability that the event will occur. Inasmuch as all buildings are subject to hazards such as hurricanes, earthquakes, flood, fire, and lightning strikes, both during and after construction, building designers and contractors have the responsibility of estimating the risks of these hazards and the magnitudes of the consequences should the events be realized. After the risk of a hazard has been assessed, the building designers and contractors, guided by building-code, design standards, zoning-code, and health-agency specifications and exercising their best judgment, should decide on an acceptable level for the risk. With this done, they should then select a cost-effective way of avoiding the hazard, if possible, or protecting against it so as to reduce the risk of the hazards occurring to within the acceptable level. Studies of building failures provide information that building designers should use to prevent similar catastrophes. Many of the lessons learned from failures have led to establishment of safety rules in building codes. These rules, however, generally are minimum requirements and apply to ordinary structures. Building designers, therefore, should use judgment in applying code requirements and should adopt more stringent design criteria where conditions dictate. Such conditions are especially likely to exist for buildings in extreme climates or in areas exposed to natural hazards, such as high winds, earthquakes, floods, landslides, and lightning. Stricter criteria should also be used for buildings that are *Revised and updated from Sec. 3, Protection Against Hazards by the late Frederick S. Merritt, Consulting Engineer. tall and narrow, are low but very large, have irregular or unusual shapes, house hazardous material or critical functions, or are of novel construction. Furthermore, building codes may not contain provisions for some hazards against which building designers nevertheless should provide protection. Examples of such hazards are vandalism, trespass, and burglary. In addition, designers should anticipate conditions that may exist in buildings in emergencies and provide refuge for occupants or safe

Slope of pipe, in / ft Pipe diameter, in 1/16 1/8 1/4 1/2 *Maximum number of fixture units that may be connected to any portion of a building drain or building sewer. Consult the administrative authority for public sewers for sizing of on-site sewers that serve more than one building. A maximum of three water closets or three bathroom groups (water closet, lavatory, and bathtub or shower, or both) may be installed in single-family dwellings and two water closets or bathroom groups, in other types of construction. Where maximum rainfall is either more than, or less than, 1 in/hr, refer to the plumbing code for suitable correction factors. Drains for building yards, subsoil drainage systems, and exterior areaways may also be connected to the storm drainage system. Where this is not possible, these drains may be run to a dry well. When a dry well is used, only the discharge from these devices may be run to the dry well. There are two ways of specifying the pipe size required for a particular class of plumbing service: (1) directly in terms of area served, as in roof-draining service (Table 14.9) and (2) in terms of fixture units (Table 14.11). As can be seen from these tables, the capacity of a leader or drain varies with the pitch of the installed pipe. The greater the pitch per running foot of pipe, the larger the capacity allowed, in terms of either the area served or the number of fixture units. The reason for this is that the steeper the pitch the larger is the static head available and hence the larger is the amount of liquid that the pipe can handle. The steps in determination of pipe sizes by means of fixture units (Art. 19.8) are: (1) list all fixtures served by one stack or branch; (2) alongside each fixture list its fixture unit (Table 14.4, p. 14.22); (3) add the fixture units and enter the proper table (Tables 14.4, 14.11, or 14.13) to determine the pipe size required for the stack or the branch. Fixture branches connecting one or more fixtures with a soil or waste stack are usually sized on the basis of the maximum number of fixture units for a given size of pipe or trap (Table 14.4). Where a large volume of water or other liquid may be contained in a fixture, such as in bathtubs or slop sinks, an oversize branch drain may be provided to secure more rapid emptying. TABLE 14.12 Size and Length of Vents Required vent diameter, in Size of soil or waste stack, in Fixture units connected Maximum length of vent, ft TABLE 14.13 Horizontal Fixture Branches and Stacks

Tapping screws are an alternative means of attaching steel roof deck to structural support members, which should be at least 1/16 in thick. All edge ribs and a sufficient number of interior ribs should be connected to supporting members at intervals not exceeding 18 in. When standard steel roof deck spans 5 ft or more, adjacent sheets should be fastened together at midspan with either welds or screws. 8.21.5 Roof Deck Insulation and Fire Resistance Although insulation is not ordinarily supplied by the roof-deck manufacturer, it is standard practice to install 3/4- or 1-in-thick mineral fiberboard between roof deck and roofing. SDI further recommends that all steel decks be covered with a material of sufficient insulating value to prevent condensation under normal occupancy conditions. Insulation should be adequately attached to the steel deck by means of adhesives or mechanical fasteners. Insulation materials should be protected from the elements at all times during storage and installation. FIGURE 8.16 Roof-deck details. The UL Fire Resistance Directory, Underwriters Laboratories, Inc., 333 Pfingsten Rd., Northbrook, IL 60062, lists fire-resistance ratings for steel roof-deck construction. Some systems with fire ratings up to 2 h are listed in Table 8.14. Several different designs of cellular steel panels and fluted steel panels for floor and roof construction are available. Sections of some of these panels are illustrated