Patent GB-467489-A (GB)
Title: Reinforced concrete ribbed flooring, and process for the production of the same
IPC: E04B5/18
Filed: 1935-10-15
Abstract: 467,489. Floors; girders. NAVRATIL, L. Oct. 15, 1935, No. 28448. [Class 20 (iv)] Each rib of a reinforced-concrete floor is formed with a cross-section which varies along the length of the rib, the cross-section in the region of the zero point O of longitudinal stress being of an intermediate or transitional profile relatively to the cross - sections of the ribs in the regions of positive and negative bending moments where the ribs are of a maximum cross-sectional area and a crosssectional profile corresponding to these moments. The intermediate profile is of a less width than the sections on each side of it. In the region of positive moments, the ribs shown in Fig. 2 are of T-shape, with the flange of a width I and the web of a width III; in the region between the point O and support T, where the moments are negative, the ribs are of inverted T-shape having the flange of width I<1> and the web of width III ; and in the region of the points O, the cross-section of the rib is of I, T, inverted-T or other shape having width II. The ribs B may be formed by casting concrete between hollow filler blocks, the T-shaped ribs being formed as shown in Fig. 3, and the inverted T-shaped ribs as shown in Fig. 4. In the vicinity of the points O, the desired shape of the ribs is obtained by means of filler blocks of suitable shape. The filler blocks may be so shaped that a rib B is cast on each side of a block, or there may be two blocks c<1>, c<2> between adjacent ribs B so that an intermediate concrete rib b, which may be reinforced, is provided between the ribs B. In the region of positive moments, the blocks c<1>, c<2> are arranged, as shown in Fig. 3, so that the ribs are of T-shape and have reinforcement v in the lower part ; in the region of negative moments, the blocks are arranged, as shown in Fig. 4, in inverted position relatively to those shown in Fig. 3, so that the ribs are of inverted T-shape, and plates f are provided between the blocks to form a flush undersurface for the floor. The depth of the blocks used to form the T-shaped ribs is less than that of the blocks used for forming the inverted-T ribs. The blocks are provided with ledges e, r which in the arrangement shown in Fig. 3 provide a flush undersurface to the floor, and, in .the arrangement shown in Fig. 4, are cut away to permit the concrete to be cast between the blocks. The intermediate ribs b may be previously cast between adjacent pairs of blocks so as to provide preformed members which are adapted to be positioned side by side to permit the main girders B to be cast between them ; in this arrangement, the blocks may be provided with lips u, and the concrete forming the ribs b may then be rammed in from the ends of the blocks. In order to increase the depth of the compression flange of the ribs B, the wall m and one or more partition walls k of chambers formed at the sides of the blocks may be broken away to provide a larger recess g for the concrete, notches n being formed in the blocks to permit this breaking away of the walls. The depth of the compression flange of the rib B can in this way be varied along the length of the rib according to the strength desired. The upper parts of the block may also be so shaped as to provide a plurality of steps on each side.