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A new type of slim floor
ELGEVIER
J. Construct. Steel Res. Vol. 46, Nos. I-3, pp. 213-214,papernumber 111, 1998 01998 ElsevierScience Ltd. All rights reserved Printedin Great Britain 0143-974x198 $19.00 + 0.00 PII: SO143.974X(98)00121-1
A New Type of Slim Floor G. Queiroz’, R.J. Pimenta2, J.M. Calixto’ and L.A.C. da Mata’ ‘Departamento de Estruturas, Universidade Federal de Minas Gerais, 30110-060, BeloHorizonte, MG, Brazil TODEME Engenharia, 32662-000, Betim, MG, Brazil Paper Number 111 Full paper on enclosed CD-ROM
A new type of slim steel-concrete composite floor is presented. It consists basically of steel beams, 200 to 250 mm deep, a 75 mm deep steel deck supported on the beam bottom flanges and a concrete slab levelled with the upper flanges of the beams. The steel deck serves as tension reinforcement of the concrete slab for positive bending moment. Additional reinforcement bars can be used if necessary. The main beams are spaced 5000 to 8000 mm apart and rigidly connected to the column flanges and web. Their spacing is limited by the final depth of the slab. The directions of the steel deck ribs are alternated from panel to panel, in order to get approximately the same loading on all beams. The shoring during construction is positioned in such a way that the depth of the beams can economically be kept constant and small. The continuity of the upper reinforcement bars, through the beam webs, is provided by special details. Stud-type shear connectors are installed on the steel deck to bottom flange connections. The composite action between the concrete slab and the steel beams is provided by the reinforcement bars passing through the beam webs and by the stud connectors installed on the bottom flange. Stud connectors are also welded to the webs of the spandrel beams. Because of the complete integration of their components, this new type of slim floor works basically as a flat slab supported on columns. The resulting advantages are: easy construction, low depth, low steel consumption and adequate strength and stiffness. A full scale slim floor system, with dimensions 15 m x 15 m x 0.2 m, was built and tested for three different loading conditions. Vertical displacements were measured on several points during each load step of every test. No significant cracks were observed on the top surface of the concrete slab. Since more tests will be run on this slim floor system, its ultimate load was never achieved. A new test is being carried out on a small model, to determine the ultimate load.
214
G. Queiroz et al
The simplified FEM model used for the analyses has been reliable in predicting the general behaviour of the slim floor system. The employed model is currently being improved in a way which will include the concrete microcracking. Its results will be compared with the already available test results and with results from future tests including the one corresponding to the floor ultimate load. The FEM modelling will be also extended to floor systems with different geometrical properties in terms of beam spacing and slab height. The results of these analyses will provide the basis for a simple design guide similar to the ECCS-Design Guide for Slim Floors with Builtin Beams. 0 1998 Elsevier Science Ltd. All rights reserved
KEYWORDS
Slim floors, composite floors, floor systems, composite structures, composite slabs, composite beams, steel decks.
J. Construct. Steel Res. Vol. 46, Nos. I-3, pp. 213-214,papernumber 111, 1998 01998 ElsevierScience Ltd. All rights reserved Printedin Great Britain 0143-974x198 $19.00 + 0.00 PII: SO143.974X(98)00121-1
A New Type of Slim Floor G. Queiroz’, R.J. Pimenta2, J.M. Calixto’ and L.A.C. da Mata’ ‘Departamento de Estruturas, Universidade Federal de Minas Gerais, 30110-060, BeloHorizonte, MG, Brazil TODEME Engenharia, 32662-000, Betim, MG, Brazil Paper Number 111 Full paper on enclosed CD-ROM
A new type of slim steel-concrete composite floor is presented. It consists basically of steel beams, 200 to 250 mm deep, a 75 mm deep steel deck supported on the beam bottom flanges and a concrete slab levelled with the upper flanges of the beams. The steel deck serves as tension reinforcement of the concrete slab for positive bending moment. Additional reinforcement bars can be used if necessary. The main beams are spaced 5000 to 8000 mm apart and rigidly connected to the column flanges and web. Their spacing is limited by the final depth of the slab. The directions of the steel deck ribs are alternated from panel to panel, in order to get approximately the same loading on all beams. The shoring during construction is positioned in such a way that the depth of the beams can economically be kept constant and small. The continuity of the upper reinforcement bars, through the beam webs, is provided by special details. Stud-type shear connectors are installed on the steel deck to bottom flange connections. The composite action between the concrete slab and the steel beams is provided by the reinforcement bars passing through the beam webs and by the stud connectors installed on the bottom flange. Stud connectors are also welded to the webs of the spandrel beams. Because of the complete integration of their components, this new type of slim floor works basically as a flat slab supported on columns. The resulting advantages are: easy construction, low depth, low steel consumption and adequate strength and stiffness. A full scale slim floor system, with dimensions 15 m x 15 m x 0.2 m, was built and tested for three different loading conditions. Vertical displacements were measured on several points during each load step of every test. No significant cracks were observed on the top surface of the concrete slab. Since more tests will be run on this slim floor system, its ultimate load was never achieved. A new test is being carried out on a small model, to determine the ultimate load.
214
G. Queiroz et al
The simplified FEM model used for the analyses has been reliable in predicting the general behaviour of the slim floor system. The employed model is currently being improved in a way which will include the concrete microcracking. Its results will be compared with the already available test results and with results from future tests including the one corresponding to the floor ultimate load. The FEM modelling will be also extended to floor systems with different geometrical properties in terms of beam spacing and slab height. The results of these analyses will provide the basis for a simple design guide similar to the ECCS-Design Guide for Slim Floors with Builtin Beams. 0 1998 Elsevier Science Ltd. All rights reserved
KEYWORDS
Slim floors, composite floors, floor systems, composite structures, composite slabs, composite beams, steel decks.