GB514267A - Improvements in or relating to fire-resisting casings for beams and columns in structures - Google Patents

Abstract

514,267. Beams, girders etc.; non-conducting coverings. LEFEBURE, V., DOUGLAS, A. H., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. April 28, 1938, No. 12783. [Class 20 (iv)] [Also in Group XIII] A fire-resisting casing for metal beams and columns in structures comprises an outer casing of gypsum, either in block form or cast in situ, not less than 1¢ ins. thick, firmly bonded to a backing layer of non-textile fibrous sheet material forming an inner casing, which is separately erected around the beam or column so as to provide substantial air spaces between the casing and portions of the structural member. The inner casing may consist of substantially rigid material such as plaster board consisting of a core of calcium sulphate plaster between liners of paper, pulp board, cardboard or the like. Alternatively, the inner casing may consist of flexible material such as paper, pulp board, cardboard or the like, in conjunction with wirenetting or other suitable reinforcement, such materials being treated with fireproofing agents such as ammonium phosphate. When rigid material is used for the inner casing, it may be shaped to fit around the beam or column 1, or used as long strips. The inner casing 2, Fig. 1, is formed by scoring on one side a sheet of plaster board enclosed in paper liners and bending such sheet along the cuts to form a box or channel section, the corners being strengthened, if desired, by textile strips. The plaster board may be provided with at least one liner comprising asbestos fibres as described in Specification 462,829, or one liner may be perforated so as to expose the plaster core at a number of places and provide a key for the subsequently-applied plaster cement. The strips or sections of the inner casing may be tied to the beam or column by metal wire or ribbon, or by metal clips; alternatively, the strips or sections may be secured by a fireproof adhesive such as a composition of cement, alkaline silicate and glue. The blocks 3, which may be of void or cellular structure, and constructed as described in Specifications 385,611, [Group V], and 484,166 are bonded to the inner casing and each other by a cement such as the fireproof adhesive referred to above, or a calcium sulphate plaster containing glue or urea-formaldehyde resin syrup, and this plaster may be reinforced by metal strips. The horizontal joints between the blocks may be reinforced by metal T-strips. The outer faces of the blocks may be coated with a cement wash and a coat of anhydrite plaster. If desired, the casing shown in Fig. 1 may be enclosed in an outer casing formed from a plaster board having at least one liner containing asbestos fibres. Instead of using the blocks 3, the inner casing 2 may be enclosed by plaster or the like cast in situ between the inner casing and a temporary or permanent outer plasterboard shuttering. As permanent outer shuttering, may be employed material similar to the inner casing and having at least its inner,liner comprising asbestos fibres. Fig. 2 shows a steel column 15, provided with wrappings 6, 7, 8 of wire netting, board and wire netting. respectively, and the blocks 9 are bonded to the wire netting 8. The blocks 9 may be finished. after erection, with a coat of anhydrite plaster. Specification 11150/01, [Class 20], also is referred to.