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| PS Hollowcore Plank Floors |
Technical Data
Hollowcore floor planks are precast concrete elements with continuous longitudinal voids providing an efficient lightweight section.
When grouted, the effective shear key between adjacent Milbank Hollowcore planks ensures that the individual planks behave similarly to a monolithic slab.
Hollowcore planks may be used to produce a diaphragm to resist horizontal forces, either with or without a structural topping.
Hollowcore planks, supported on masonry or steel structures can be used in domestic, commercial and industrial applications.
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Installation
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Camber
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Finishes
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| Design |
All the precast concrete units are designed to the requirements of BS 8110 1997.
The standard Milbank prestressed sections are designed for moderate exposure conditions and to meet the serviceability criteria of Class 2 members.
High tensile steel wire or strand is used for the prestressing tendons, in various configurations to suit particular spans and design loadings.
Standard Milbank prestressed planks have a minimum fire resistance of 1 hour. Modified sections are available for greater periods of fire resistance.
Milbank are able to offer a variety of economical design solutions by combining their full range of prestressed and precast concrete products.
| Manufacture |
Milbank prestressed planks are manufactured in an enclosed factory environment, on steel beds to a standard width using a slipforming process.
All materials used in the manufacturing process conform to the requirements of the relevant British Standard for that material.
An air-entraining agent and a water-reducing admixture are used to achieve the correct workability.
The floor planks are sawn to the required length on the manufacturing bed. They are supplied to site with plain sawn open ends as standard. (Other details such as solid ends, shelf ends and open topped cores can be provided).
Holes can also be formed during manufacture, the size and position depending upon the design criteria. Steel trimmers can be provided to form large openings up to 1200mm wide.
| Dimensions |
All units are manufactured to comply with the cross sectional tolerances set out in BS8110 1997. Length tolerances are ± 20mm.
Units are manufactured to the following nominal depths: 250mm, 200mm, 150mm and 100mm. (Any depth section can be manufactured as a solid slab).
The standard nominal width for all units is 1200mm. Non-standard width units are formed by cutting the planks longitudinally on the beds, before the concrete has hardened.
Where units are built into flank walls, the bottom nib of the profiled edge is removed during manufacture.
Floor layout drawings are based upon normal tolerances, and adjustment to joint widths may be required to complete the floor area.
In situ make-up strips can be minimised by using reduced width units, Milbank prestressed beams or concrete block infill.
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| Layout Drawings |
Milbank will provide layout drawings for the floor units prior to manufacture. These drawings show the structure supporting the precast units, position of service entries etc, typical sections and the loads for which the floor is designed.
| Installation |
Installation of Hollowcore floor planks is straightforward. The units are hoisted into position on the supporting structure by crane and the joints grouted up to form a monolithic floor.
The completed floor provides an immediate working platform for following trades.
Where required a structural concrete topping can be laid together with the joint infill to form a composite concrete floor to increase the strength of the flooring system.
| Grouting |
The joints between the units should be grouted with 20N/mm² concrete using a maximum aggregate size of 20mm.
| Camber |
All prestressed floor units will have an upward camber. The degree of camber is dependant upon the span and the prestressing force, but will not exceed span/300 for spans up to 7 metres.
Variations in camber between adjacent units will be within the tolerances specified in BS8110, except in areas where the adjacent spans are of different lengths, or where large holes are formed within the middle third of the units.
| Finishes |
The soffit finish of Milbank prestressed planks is Type A, other surfaces are "as extruded".
Water may accumulate within the cores during the building construction, and Weep Holes may need to be drilled by the contractor to release this entrapped water. Where weep-holes are provided during manufacture, these must be kept clear by the contractor.
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