Patent GB-512867-A (GB)
Title: Improvements in the construction of roofs of buildings and the like
IPC: E04B7/12
Filed: 1938-03-23
Abstract: 512,867. Roofs; storage bins; constructional metal work. PANDYA A. H. March 23 1938, No. 8959. [Classes 20 (i), 20 (ii) and 20 (iv)] A ridged roof or other ridged structure, such as the floor of,a storage bin, adapted to carry loads distributed over a large horizontal area without intermediate supports, comprises a plurality of continuous beams 2b, Fig. 1, which are disposed substantially perpendicular to the ridge line 4, are cranked at the ridge line so as to lie in the planes of the structure, and are supported by columns or equivalent means 1 at their ends only; three boom members 3, 5a, 5b are disposed, respectively, along the ridge line and along cave or valley or other fold lines of the structures, and co-operate with the continuous beams to form two girders which lie at an angle to the horizontal and provide virtual support for the beams at the cranking points therein, and a gable tie 6 is provided at each end of this pair of girders for the purpose of taking up the horizontal components of the girder reactions. The cranked portion of each continuous beam is rigid enough to transmit substantial bending moment from one straight portion of the beam to the adjoining portion. If desired, the end cranked beams need not be continuous at the ridge points 4<1>, which are then supported by an additional column 1<1>. The inclined girders forming the structure may be provided with diagonal bracing. The structure shown in Fig. 2 is provided with continuous beams which are each cranked at three points to provide four inclined portions 2a, 2b, 2c, 2d, the cranking points coinciding with the ridge and valley members 3a, 3b, 7 of the structure. A gable tie 6a, 6b is provided at each end of each bay, and an additional column 11 is placed at each end of each valley member 7. The continuous beams may be provided with more than three cranking points, in which case, additional ridge and valley members, gable ties, and supporting columns for the valley members are provided. The roof structure may be of the north-light type in which the girders on opposite sides of the ridge members lie at different angles to the horizontal. The roof structure may also be provided with one or more raised portions to accommodate skylights or ventilators; as shown in Fig. 5, each continuous beam is cranked at five points which coincide with boom members 12a, 13a, 3, 13b, 12b so as to provide a raised middle portion, and gable ties 6a, 6b, 6c, take up the end reactions of the girders The structure may be constructed of structural steel or reinforced concrete. The joint between the members 2a, 2b of the cranked beam and a ridge member may be formed by bevelling the ridge ends of the members 2a, 2b, as shown in Fig. 7, and welding these ends to the opposite sides of a flat plate 20 ; the ridge member comprises two purlins 21a, 21b welded to the top flange of the cranked beam and an angle-bar 22 welded to the bottom flange of the cranked beam and to the plate 20. The joint between the members 2b, 2c, of the cranked beam and a valley member may be formed as shown in Fig. 8 by butt-welding the ends of the members 2b, 2c to a filling plate 24. The ends of the upper flanges of members 2b, 2d are buttwelded together, and the lower flanges are buttwelded to a bent strap 25 which is welded to the plate 24. The valley member comprises two channels 26 welded to the web of the cranked beam at the cranking point.