Bison Precast Flooring Specification

Transcription

1 Page: 1 of SCOPE OF THE SPECIFICATION 1.01 Floor types: This specification covers the design, manufacture and associated site work for the following floor types; Hollow core floors Composite hollow core floors Solid composite floors 1.02 Description of floors Precast concrete floors are designed and manufactured as prestressed precast units whichh when assembled and joints filled with concrete provide a one-way spanning floor plate. Hollow core units are nominally 1200mm wide, of rectangular cross section with a series of longitudinal cores through the section to provide a weight saving to improve structural performance. Composite Hollow Core floors consist of the same units but the load capacity of the finished floor is enhanced by the provision of a structural concrete topping which is cast on site. Solid Composite floors consist of solid prestressed planks without cores and with a structural topping which is cast on site. 2.0 MATERIALS 2.01 Standards: All materials and finished products are to be designed to approved standards set down in the contract, the appropriate British Standards, and this specification Concrete: The compressive strength classes generally used in the design and manufacture of the units are as follows:- The compressive strength at 28 days is C45/55 The concrete strength at transfer is C25/ Admixture: Only an admixture complying with BS EN may be included in the concrete Reinforcement: Reinforcement is generally 5mm diameter high strand complying with the requirements of BS tensile wire or 12.5mm 3.0 DESIGN 3.01 Code: Unless otherwise agreed the design of Bison units is in accordance with the requirements and recommendations of BS 8110:1997 The Structural Use of Concrete 3.02 Service Class: The design of Bison units is to BS 8110 Serviceability classification, Class 3 with a limiting crack width of 0.1mm. Design to other classifications is as agreed in the contract Durability: The standard requirements of BS Bison hollow core slab is designed to comply with the durability

2 Page: 2 of 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 additionall finishes. These periods of fire resistance may be further enhanced by the application of appropriate finishes Sound: The requirements of the Building Regulations and details of compliance are contained in a separate data sheet, which can be supplied on request 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. Tying details achievable with our hollow core units are contained in a data sheet which is available on request 3.07 Composite design: Wheree Bison hollow core/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 Insitu Floor make-up areas: Strips between units We shall provide precast units in combination of standard 1200 mm widths, and standard part-width units. To make up the complete floor area it may be necessary where unavoidable to supplement these with insitu strips between units inclusive of reinforcement. These are to be provided and placed by others to our recommendation. Miscellaneous Areas Floor areas or plan shapes which are small and irregular occasionally fall outside the manufacturing capability for Hollowcore and require an insitu make-up slab. These will be identified on Approval drawings for validation of design by the Structural Engineer Thermal insulation: Our hollow core units can be supplied with polystyrenee insulation glued to their bottom soffit. This is to provide the necessary thermal transmittance (u-value) in accordance with the Building Regulations, Part L. 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 and cured on steel beds within an enclosed factory environment Ends of units: Bison units are sawn to length on the manufacturing bed and are supplied as standard with plain sawn ends, with open cores or reduced ends Dimensions: Bison units are manufactured in nominal widths of 1200mm Solid planks: Depths 60 mm, 75 mm and 100 mm Hollow core: Depths 150, 200, 250, 260, 300, 350, 400 and 450 mm 4.04 Permitted deviations: Tolerances are set out in clause of BS 8110:1997. Length tolerances are + 20mm Camber: Bison units will have an upward camber due to the prestressing force 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. The

3 Page: 3 of 4 camber will vary between adjacent units and can give rise to a piano key effect. It maybe possible to reduce the camber between units by loading prior to the joint between the units being grouted Finishes: Unless stated in Bison s quotation, concrete surface finish to soffit is a Type A finish as described in clause of BS8110:1997. The standard of finish referred to is as per the sample panels located at our production facilities. The soffit is suitable for the direct application of a textured (high build) 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 instructionss 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 8110:1997. To achieve a reasonably level surface to accept the resilient layer, it may be necessary to use a local levelling to accommodate the manufacturing and construction tolerances 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 100 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 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. Requirements for temporary propping will be identified on our drawings Holes and Cut-outs: All factory formed holes and cut-outs will be of rough appearance and are formed subject to the design capacity of the slabs. Due to manufacturing techniques, holes and cut- hole sizes will be outs may be larger in the transverse width of the slab than specified. Manufactured shown on the drawings. Holes may be either rectangular or circular depending on the manufacturing techniques employed. 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 Drainage Points: Water may accumulate within the cores due to exposuree during the construction programme. Unless otherwise instructed Bison will provide drainage points in slabs with factory formed reduced / troughed / solid / capped ends only. Water may seep out of the unit for a considerable time after installation and the drain holes may not be neatly formed. The Customer is responsible for opening out drainage points, keeping them clear during construction and for subsequent infilling / making good as required. Water trapped in the cores may present a risk to operatives from the alkaline state of the water.

4 Page: 4 of Notching: Where slabs are notched around stanchions or similar obstructions, these will be of rough appearance (see also clause 4.10). Unless expressly stated in Bison s quotation, any resultant infilling between slab and stanchions, columns or similar obstructions within the depth of the slab is to be carried out by others Anti-Crack Provision: It is the insitu screed over all cracking in finishes. recommended that a light mesh reinforcement be provided by others in supporting steel beams, in order to minimise the possibility of latent 5.05 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 steell angle provided by Bison to trim large openings is i to be fire protected by others Bearings: Level and structurally adequate bearings for Bison precast units are to be provided by others. Bearings should generally be 100mm for masonry or 75mm for concrete or steelwork, but may be reduced in accordance with clause of BS 8110:1997 or after consultation with our design office. It is Bison s Customers responsibility to ensure that all bearings have been designed appropriately to take into account of temporary loads during erection Shelf Angles: In cases where the Bison slabs fit under the top flange of steel beams or columns, it is assumed that the dimension from the top of the slab down to the flanges will not exceed 25 mm. If Bison slabs are supported on shelf angles, the bearing legs of these should be 100 mm wide or a dimension of half the flange width plus 25 mm for 600 mm wide slabs and plus 50 mm for 1200 mm 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 BS 8110: Temporary Bearings/Propping: Where propping is required, unless expressly stated in Bison s quotation, Bison s Customer is responsible and liable for the temporary works design and the provision of necessary labour, plant and equipment in respect of such propping. Such temporary works design is to be undertaken by a competent technical authority and is to be made available to Bison. 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. Permission must also be obtained from Bison s Holes and Cut-outs: 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. Requests for larger holes to be referred to Bison s Engineering Department for design verification Grouting of Joints: Joints between units should be grouted with 30N/mmm 2 concrete using a 6-10 mm nominal aggregate size. These joints should be double brushed and tampered down to ensure good compaction. Deferential settlement of the grout in the joint may occur due to shrinkage and movement of the floor area during the grouting operation Lifting sockets: All socketss formed for lifting purposes or any raised areas of displaced concrete are to be filled and made good / removed by others, when erection is complete.

5 Page: 5 of 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 Quality Assurance. Reference: All Bison manufacturing facilities are members of the B.S.I. Registered Firm Scheme for Quality Assurance to BS EN ISO 9001:2008 for the design, manufacture and erection of precast hollow core floors Quality Assurance. Scope: Membership of the scheme ensures that all procedures and disciplines relevant to the design and manufacturing processes are subject to independent approval and periodic review by the British Standards Institution Quality Assurance. Manufacture: All Bison manufacturing facilities have been assessed by the British Standards Institution (BSI) and awarded certificates of Assessed Capability under the scheme covering Quality Assurance for the manufacture of precast concrete floors.