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Title: Section 704  •  Size: 9950

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SECTION 704 - PROTECTION OF STRUCTURAL MEMBERS

704.1 General. Structural members having the fire-resistive protection set forth in Table 7-A shall be assumed to have the fire-resistance ratings set forth therein.

704.2 Protective Coverings.

704.2.1 Thickness of protection. The thickness of fire-resistive materials required for protection of structural members shall be not less than set forth in Table 7-A, except as modified in this section. The figures shown shall be the net thickness of the protecting materials and shall not include any hollow space back of the protection.

704.2.2 Unit masonry protection. Where required, metal ties shall be embedded in transverse joints of unit masonry for protection of steel columns. Such ties shall be as set forth in Table 7-A or be equivalent thereto.

704.2.3 Reinforcement for cast-in-place concrete column protection. Cast-in-place concrete protection for steel columns shall be reinforced at the edges of such members with wire ties of not less than 0.18 inch (4.6 mm) in diameter wound spirally around the columns on a pitch of not more than 8 inches (203 mm) or by equivalent reinforcement.

704.2.4 Embedment of pipes. Conduits and pipes shall not be embedded in required fire protection of structural members.

704.2.5 Column jacketing. Where the fire-resistive covering on columns is exposed to injury from moving vehicles, the handling of merchandise or other means, it shall be protected in an approved manner.

704.2.6 Ceiling membrane protection. When a ceiling forms the protective membrane for fire-resistive assemblies, the assemblies and their supporting horizontal structural members need not be individually fire protected except where such members support directly applied loads from a floor and roof or more than one floor. The required fire resistance shall not be less than that required for individual protection of members.

704.2.7 Plaster application. Plaster protective coatings may be applied with the finish coat omitted when they comply with the design mix and thickness requirements of Tables 7-A, 7-B and 7-C.

704.2.8 Truss protection. Where trusses are used as all or part of the structural frame and protection is required by Table 6-A, such protection may be provided by fire-resistive materials enclosing the entire truss assembly on all sides for its entire length and height. The required thickness and construction of fire-resistive assemblies enclosing trusses shall be based on the results of full-scale tests or combinations of tests on truss components or on approved calculations based on such tests which satisfactorily demonstrate that the assembly has the required fire resistance.

704.3 Protected Members.

704.3.1 Attached metal members. The edges of lugs, brackets, rivets and bolt heads attached to structural members may extend to within 1 inch (25 mm) of the surface of the fire protection.

704.3.2 Reinforcing. Thickness of protection for concrete or masonry reinforcement shall be measured to the outside of the reinforcement except that stirrups and spiral reinforcement ties may project not more than 1/2 inch (12.7 mm) into the protection.

704.3.3 Bonded prestressed concrete tendons. For members having a single tendon or more than one tendon installed with equal concrete cover measured from the nearest surface, the cover shall not be less than that set forth in Table 7-A.

For members having multiple tendons installed with variable concrete cover, the average tendon cover shall not be less than that set forth in Table 7-A, provided:

1. The clearance from each tendon to the nearest exposed surface is used to determine the average cover.

2. In no case can the clear cover for individual tendons be less than one half of that set forth in Table 7-A. A minimum cover of 3/4 inch (19.1 mm) for slabs and 1 inch (25.4 mm) for beams is required for any aggregate concrete.

3. For the purpose of establishing a fire-resistive rating, tendons having a clear covering less than that set forth in Table 7-A shall not contribute more than 50 percent of the required ultimate moment capacity for members less than 350 square inches (0.226 m²) in cross-sectional area and 65 percent for larger members. For structural design purposes, however, tendons having a reduced cover are assumed to be fully effective.

704.4 Members Carrying Masonry or Concrete. All members carrying masonry or concrete walls in buildings over one story in height shall be fire protected with one-hour fire protection or the fire-resistive requirement of the wall, whichever is greater.

704.5 Fire Protection Omitted. Fire protection may be omitted from the bottom flange of lintels spanning not over 6 feet (1829 mm), shelf angles, or plates that are not a part of the structural frame.

704.6 Spray-applied Fireproofing. The density and thickness of spray-applied fireproofing shall be determined following the procedures set forth in U.B.C. Standard 7-6.

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