Loop-Free Tie-Down Node with an Anchor Rod-Dowel for a Hollow-Core Floor Slab of Formwork-Free Shaping
Authors:   Professor at the Department of “Building Structures” of the Faculty of “Construction of Buildings and Structures” of the Tashkent Institute of Architecture and Construction, Tashkent, Uzbekistan., Pulat* Mirzaev , Kadir Umarov ,   Chief Engineer of the “GEO BETON TRUST” Reinforced Concrete Products Plant, Tashkent, Uzbekistan., Shavkat Mirzaev ,   Director of the Innovation Center at the Tashkent Institute of Architecture and Construction, Tashkent, Uzbekistan.
Published: August 2020

When designing buildings and structures for various purposes, the specialists should find new decisions for the possibility of using structures made using the long-line formwork-free technology, including hollow-core floor slabs, namely: installation without free lengths of reinforcement, lifting without the tie-down loops, joint units with other structure elements, configuration of sections with new geometrical parameters. As the hollow-core slabs of formwork-free shaping are produced without tie-down loops, the problems of installation and transportation of these slabs are discussed. Examples of tie-down nodes installation in the slabs produced by the formwork-free shaping technology were considered in the paper, with the justification of the complexity of their installation in such slabs and the increased metal consumption. The aim is to reduce the laboriousness of rigging work and to provide a gripping device for a hollow-core slab of formwork-free shaping when removing it from a long-line pallet, storing, loading and installing this slab during the construction process. A constructive-technological decision was proposed for a tie-down node installed in the slab body without the use of a tie-down loop and having only an anchor rod-dowel through which the tie-down of a slab could be directly done without the use of traditional tie-down loops. The node was designed with reduced metal consumption and does not change the technology of manufacturing hollow-core slabs of formwork-free shaping. The theoretical basis for calculating the bearing capacity of the proposed tie-down node, installed in a hollow-core slab of formwork-free shaping was determined and summarized. It was revealed that the bearing capacity of the proposed tie-down node installed in the body of a hollow-core slab, under the action of lifting loads, depends on the splitting force of concrete protective layer located above the anchor rod-dowel of this node (all things being equal). The theoretical data of the study were validated by full-scale tests of slabs with tie-down nodes installed in their body, carried out in accordance with the proposed structural-technological development. The operational suitability of the proposed tie-down nodes with an anchor rod-dowel for the hollow-core slabs of formwork-free shaping and the possibility of their implementation at other enterprises of the country having production lines for long-line formwork-free shaping were stated. A tie-down node with an anchor rod-dowel, proposed to be installed in a hollow-core slab of formwork-free shaping, can be used in other reinforced concrete structures produced by the technology of long-line formwork-free shaping. A patent for a utility model has been received for the development of a loop-free tie-down node for a hollow-core slab of formwork-free shaping.