BISON PRECAST FLOORING SPECIFICATION

Transcription

1 BISON PRECAST FLOORING SPECIFICATION 1.0 SCOPE OF THE SPECIFICATION 1.01 Relates to: This specification covers the design, manufacture and associated site work of the following types of floors:- Hollowcore floors Composite Hollowcore floors Solid Composite floors 1.02 Description of floors The precast floors are designed and manufactured as prestressed precast floors. Hollowcore floors are prestressed precast floors with a series of holes through the section. Composite Hollowcore floors consist of prestressed precast floors with a series of holes through the section. The load capacities of the floors are enhanced by the provision of a structural topping on site. Solid Composite floors consist of solid prestressed precast floors with a structural topping on site. 2.0 MATERIALS 2.01 Standards: All materials are to be in accordance with the appropriate British Standard and this specification Concrete: The design strengths of concrete used in the design and manufacture of Bison units is as follows:- Ultimate Concrete Strength is to be a minimum of 55 N/sq.mm Concrete Strength at transfer is to be 30 N/sq.mm 2.03 Admixture: An air entraining agent complying with BS EN 934-2:2001 is included in the concrete mix to improve workability Reinforcement: Reinforcement is generally 5mm diameter high tensile wire or 12.5mm strand complying with the requirements of BS 5896: DESIGN 3.01 Code: The design of Bison units is in accordance with the requirements and recommendations of BS 8110:1997 The Structural Use of Concrete. 1

2 3.02 Service Class: The design of Bison units is to Serviceability classification, Class 3 with a limiting crack width of 0.1mm. Other classifications can be provided if requested Durability: The standard Bison hollowcore floor slab is designed to comply with the durability requirements of BS8500: Fire: Fire resistance is based upon the tabulated data contained within BS 8110 : Part 2 Section 4. Sections are available for fire periods of 1 hour or 2 hours without the addition of further finishes. This period of fire resistance may be further enhanced by the application of appropriate finishes Sound: The requirements of the Building Regulation for multiple occupancy dwellings state that precast concrete units used within a floor should have a minimum mass of 300kg/m². Where requirements state a directly bonded screed, the floor construction should have a minimum mass of 365kg/m² (precast unit and directly bonded screed finish, Floor Type 1). Requirements for separating floors, walls, floor finishes and separating layers are as laid down in Building Regulations Part E. Slabs used in compliance with the Building Regulations require Pre-Completion Testing (PCT). Slabs used in compliance with approved Robust Standard Details (RSD s) require no on site Pre- Completion Testing. For buildings other than residential, it may be necessary to obtain advice from an acoustic engineer for the suitability of Bison floors. The mass of Bison unit sections are given below and are net weights of standard hollow sections. Type Depth(mm) Mass(kg/m 2 ) T T T2S This information is to assist you in your overall floor design compliance with the sound insulation requirements of the Building Regulations 1991 (Approved Document E) Horizontal and Vertical Ties: Ties necessary to satisfy the requirements for accidental damage should be specified by the Engineer with the responsibility for the design of the overall structure in accordance with the relevant Codes of Practice. 2

3 3.07 Composite: Where Bison hollowcore/solid plank units are designed to form part of a composite floor construction, the completed composite floor requires a structural concrete topping. The structural topping, grouting between precast units and distribution reinforcement to be provided and placed by others to our recommendation. We shall provide precast units in our standard widths, and to make up the complete floor area it may be necessary for full depth insitu strips to be used. Such insitu strips inclusive of reinforcement to be provided and place by others to our recommendation. 4.0 MANUFACTURE 4.01 Method of Manufacture: Bison floors are manufactured by the long line prestressed method using slip form or extrusion techniques. The units are cast on heated steel or steam cured beds within an enclosed factory environment Ends of Unit: Bison units are sawn to length on the manufacturing bed and are supplied as standard with plain sawn ends with open cores Dimensions: Bison Units are manufactured in nominal widths of 1200mm Solid: Depths 75mm 100mm Hollow: Depths 150mm 200mm 250mm 260mm 300mm 350mm 400mm 450mm 4.04 Permitted Deviations: Cross-sectional tolerances are within the limits set out in clause of BS 8110:1997. Length tolerances are + 20mm Camber: Bison units will have an upward camber due to prestressing as described in clause of BS 8110:1997. Due allowance should be taken when specifying screeds, finishes, partitions etc for upward camber together with differential camber between adjacent units Finishes: Concrete surface finish to soffit is a Type A finish as described in clause of BS8110:1997. The soffit is suitable for the direct application of a textured paint finish where this is applied in accordance with the manufacturer s instructions. A Caulking layer to the soffit may be required for other types of paint finish. Where a plaster finish is intended it may be necessary to use a bonding agent in accordance with the instructions of the plaster manufacturer. Plaster finishes are not recommended on longer spans. Sides and top surfaces are as extruded as described in Table 5.5 of BS 8110: Infill Strips: Except where noted otherwise, our quotation allows for the design and provision of the floor areas indicated. We shall maximise the use of our standard flooring products, but to achieve complete areas it may be necessary, in certain instances, to use in isolation or in combination special cut width units or insitu strips. The width of such cut width units or insitu strips shall be at Bison s discretion. With hollow core or solid plank units 75 or 150 mm, nominal wide strips of Bison special precast infill pieces may also be used. To achieve complete areas it may also be necessary, in certain instances, for us to design full slab depth insitu strips to be reinforced and provided by yourselves. Such insitu strips will be shown on our working drawings Edge of Unit: Edges are shaped to form a grout joint, giving a shear key to distribute load to adjacent units. Where special cut width units are provided, the edge will be rough cut from a standard unit. 3

4 4.09 Cantilevered Balconies: Where quoted, flooring behind cantilevered balconies is designed as composite construction using a combination of precast flooring and structural concrete topping. We shall provide the complete composite construction and we shall specify, on our working drawings, the detail and duration of any temporary propping that is required. Special insulation may be required to provide a thermal break. Bison can provide a suitable system where this is a requirement of the building specification Holes and Cutouts: All factory formed holes and cut outs are subject to the design capacity of the slabs. Due to manufacturing techniques, holes may be larger in the transverse width of the slab than specified. Manufactured hole sizes will be shown on the drawings. Holes may be either rectangular or circular, depending on the manufacturing techniques employed Factory formed lifting devices: Bison are able to provide machine inserted lifting devices within all flooring units. These may be proprietary lifting hooks or pins, dependent on the product type. 5.0 SITE WORK 5.01 Standard: All site work is to be undertaken in accordance with the best current practice and Health & Safety legislation. For further advice reference should be made to the "Code of Practice for the Safe Erection of Precast Concrete Flooring" Drainage Points: Units may accumulate water within the cores due to exposure during the construction programme. Unless otherwise instructed, Bison will provide drain points in slabs where, in the constructed state, water cannot find a free exit path. The General Contractor shall keep the drain points clear where they are provided. Water trapped in the cores may present a risk to operatives from the alkaline state of the water and is covered by risk assessments obtained from Bison Concrete Products Ltd Notching: Where slabs are notched around stanchions or similar obstructions, any resultant infilling between slab and steelwork within the depth of the slab, to be carried out by others Anti-Crack Provision: It is recommended that a light mesh reinforcement be provided by others in the insitu screed over all supporting steel beams, in order to minimise the possibility of latent cracking in finishes Thermal Insulation: It is recommended that thermal insulation should be provided on roof areas and the breaks should be made in plaster at junctions between our works and other materials Trimmer Angles: Any steel angle provided by Bison to trim large openings is to be fire protected by others Bearings: Level and structurally adequate bearings for Bison precast units are to be provided by others. These should generally be 100mm for concrete and masonry and a minimum of 75mm for steelwork, but subject to the requirements of clause of BS 8110:

5 5.08 Shelf Angles: If the Bison slab is supported on shelf angles, the bearing legs of these should be 100mm wide or a dimension of half the flange width plus 25mm for 600mm wide slabs and plus 50mm for 1200mm wide slabs, whichever is the greater. Special consideration may be required for plated or broad flange steel beams. Additional bearings will be required where slabs trim stanchions etc. and for providing the minimum bearing in accordance with BS8110: Temporary Bearings/Propping: Unless the design specifically allows for units to seat onto temporary bearings (i.e. head trees and bearers, etc.) this practice shall be avoided wherever possible. In cases where such measures are unavoidable, fixing must not progress until permission has been obtained from a competent technical authority within the Bison organisation. We shall specify, on our working drawings, details and duration of any temporary propping that may be required Holes and Cutouts: Small holes up to 60mm diameter may be drilled on site through the hollow cores, care being taken to avoid damage to the reinforced ribs. Larger holes may be cut subject to the design capacity of the slabs Grouting of Joints: Joints between units should be grouted with 30N/mm2 concrete using a 6mm nominal aggregate size Lifting sockets: All pockets formed where lifting devices are provided by Bison, are to be filled and made good by others, at no cost to Bison, when erection is complete Soffit fixings: We do not cast timber battens into the soffit of our units. Several fast and cost effective proprietary systems are available for direct fixing to concrete and we shall be pleased to provide details on request. 6.0 QUALITY MANAGEMENT SYSTEM 6.01 QMS Reference: Bison are members of the BSI Registered Firm Scheme for Quality Management Systems to BS EN ISO 9001:2000 for the design, manufacture and installation of precast products Scope: Membership of the scheme ensures that all processes relevant to the design, manufacture and installation of precast products, are subject to independent review and approval by the British Standards Institution. 5