IL41236A - Girder with pre-tensioned rigid reinforcement - Google Patents

Claims (4)

1. WHAT IS CLAIMED IS : 1. A method of manufacturing a girder comprising a pre-stressed rigid reinforcement which, even on its own, constitutes a girder capable of withstanding bending and which comprises a solid, perforated or lattice web and at least one flange, characterised in. that the said rigid reinforcement is submitted over at least a portion -of its length to a tension substantially parallel to its. longitudinal axis, said tension being obtained by applying two forces or two sets of forces whose resultants have the same magnitude with opposite signs, in that one maintains these forces or sets of forces whilst concrete is made integral with a least a portion of the rigid reinforcement which portion comprises at least some of the tensioned fibers of said reinforcement, in that after the concrete has hardened up and has been made integral on the rigid reinforcement one removes the said forces or sets of forces which causes at least some of the said concrete to be pre-compressed.

2. A method according to claim 1, wherein the resultants of said tensioning forces are positioned nearer to the extreme, fibers of the rigid reinforcement whose stresses from the working loads when the girder is in use are tensile stresses than to the extreme fibers whose load stresses in use are compressive stresses. 5«' A method according to claim 1, wherein the resultants of said tensioning forces are positioned eccentrically with respect to the centres of gravity of the cross-sections of the rigid reinforcement on the same side as the extreme fibers of the rigid reinforcement whose working load stresses in use are tensile .. A method, according to claim 1, characterised in that the tensioned flange of the rigid reinforcement is metallic, whereas its other parts are either wholly metallic or are composed of concrete and steel in combination. 5. A method according to either of the claims 1 to 4, characterised in that the tensioned zone of the girder is reinforced by additional non rigid rein orcement members tensioned before making the pre-compressed concrete. 6. A method according to any of the claims 1, 2 or 3, characterised in that the application zone of one at least of the resultants of the tensioning forces is spread over an area extending along the length of the rigid reinforcement. 7. method according to any of the claims 1. 2 or J, characterise in that the application zone of one at least of the resultants is concentrated within a localised area on the rigid reinforcement, 8. A method according to claim 1, characterised in that the pre-compressed concrete is made integral with the tensioned flange of the rigid reinforcement over at least a portion of the periphery of the said flange. 9. A method according to any of claims 1, , 8 characterised in that the girder comprising the rigid reinforcement and the pre-compressed concrete portion is completed by a further portion in concrete or in reinforced concrete constituting at least a part of a flange of the final girder which is subjected in use to compressive stresses. 10. A method according to any of the claims 1, - or 8, characterised in that the girder comprising the rigid reinforcement and the pre-compressed concrete portion is completed by a further portion in concrete or in reinforced concrete constituting at least characterised in that the tensioned zone of the girder is reinforced by non rigid reinforcement pre-tensioned after the pre-compressed concrete has hardened up. 12. A method according to any of claims 1, 4-, 8, 9, 10, 11, characterised in that the tensioned zone of the girder is reinforced by non rigid and non tensioned reinforcement members. 1

3. A method according to claims 5> H or 12, characterised in that the non-rigid reinforcements are composed of the same kind of steel as that of the rigid reinforcement. 1

4. A method according to claims 5> H or 12, characterised in that the non rigid reinforcements are composed of kinds of steel different from steel of which the rigid reinforcement is composed. 15* A method according to any of the preceding claims, characterised in that the rigid reinforcement is subjected both to said tensioning producecd by longitudinal forces and to a simultaneous bending produced by transverse forces. 16. A method according to claim 1, characterised in that pre-hardened concrete is made integral with the rigid reinforcement. 1 . A method according to any of the preceding claims, characterised in that the resultants of said tensioning forces are applied to two or more rigid reinforcements at the same time. 18. A method according to claim 17, characterised in that the rigid reinforcements are connected and placed one after another along the same axis. 19. A method of manufacturing a girder or beam formed by a rigid elongate reinforcement element embedded at least partially in concrete wherein the reinforcement element is subjected by length, before moulding the concrete upon said reinforcement element, and said tensioning by said external forces is maintained until the concrete has hardened and set. 20. Δ method of manufacturing a girder substantially as herein described and illustrated with reference to the accompanying drawings. 21. A girder made according to the method described i any of the preceding claims. COHEN ZEDEK & SPISBACH P. O. Box 33116-, Tel-Aviv iorneys for Applicant