The cost of intumescent coatings increases as the

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The cost of intumescent coatings increases as the required fire rating increases. Therefore, their use is generally limited to exposed steel applications. It is not uncommon to see single members with a combination of systems; spray-applied fibrous systems on hidden portions and intumescent coatings on exposed portions. UNDERWRITERS LABORATORIES (UL) ASSEMBLIES A summary of UL assemblies that are commonly applicable in structural steel building design and construction is provided in Tables 6-10. These tables should be used in conjunction with the criteria and information con- tained in the latest UL Fire Resistance Directory. However, the inclusion of these assemblies in this Guide should not preclude the use of other UL assemblies or any other rational approach. The ratings for the assemblies discussed in Tables 6-10 are given for a minimum member size that can be relat- ed to other larger member sizes. For W-shapes and similar members, this relationship can be made by the ratio of the weight to the heated perimeter ( W/D ). For HSS and steel pipe, the ratio of the area to the heated perime- ter ( A/P ) defines the relation. W/D and A/P ratios are given in the Materials Section of this Guide. Note that certain UL assemblies can also be used with members with smaller W/D and A/P ratios, provided cer- tain criteria as outlined in the specific UL design are met. Also keep in mind that the equations for columns and braces are generally different because the heated perimeter of a beam differs from that for a column or brace. Table 6 lists some fire protection systems for roof-ceiling assemblies. Table 7 covers floor-ceiling assemblies. Table 8 lists protection systems for beam-only designs for the roof and Table 9 lists beam-only designs for the floor. Finally, Table 10 shows protection for some common column assemblies. These tables make reference to "restrained" and "unrestrained" ratings, discussed in the next section. RESTRAINED AND UNRESTRAINED CONSTRUCTION In the context of fire resistance, the use of the terms "restrained" or "unrestrained" construction refers to the abil- ity of the structural members and the surrounding construction to resist thermal expansion during elevated tem- peratures. This is often confused with structural restraint that has to do with the fixity or rigidity of supporting mem- bers at their connections. Thermal restraint is an important consideration because most materials tend to expand when heated. The restrained condition as defined by the codes applies when an assembly (floor system, roof system and its supporting members) is surrounded by construction that is capable of resisting substantial thermal expansion
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SYSTEMS PAGE 66 Table 6 Roof-Ceiling Assemblies Rigid
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PAGE 67 SYSTEMS Table 7 Floor-Ceiling Assemblies
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SYSTEMS PAGE 68 Table 8 Beam-Only Designs for Roofs Table 9 Beam-Only Designs for Floors
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PAGE 69 SYSTEMS throughout the range of anticipated elevated temperatures. Extensive research in the 1960s showed that restraint improves the fire resistance of many types of common floor system types of common floor systems. For example,
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  • Fall '19
  • Structural steel

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