SPECIFICATION FOR PRECAST/ COMPOSITE CONCRETE FLOORS/ ROOF DECKS SECTION E60

Transcription

1 SPECIFICATION FOR SECTION E60 A S.W. Revision Date Issue Authorised By Approved for Issue SW Date clarkebond Page 1 of 6

2 To be read with Preliminaries/ General Conditions. GENERAL 10 B SCOPE OF WORKS This sub-section applies to structural floor and roof slabs and stairs, partly or wholly of precast concrete, as indicated on the project drawings. 15 B MEASUREMENT The rates for floor units shall include for all insitu make up strips required including those around holes and along side walls which run parallel with the units. The Precast Contractor shall include for all of these items. 20 B PRECAST/ COMPOSITE CONCRETE SYSTEMS All reinforced or prestressed pre-cast composite concrete floor and roof slab systems are to be supplied under the British Standards Institution Scheme for Registered Firms of assessed capability for the manufacture of pre-cast concrete elements and floor units, except only those types to which the scheme is not currently applicable. The use of such systems is subject to the following conditions: 1. Both the Firm and the Product to be registered by the BSI. 2. The design and detailing of the system is the responsibility of the Contractor not withstanding any acceptance or approval by the CA and is to be in accordance with BS , particularly the serviceability, tying and pre-cast concrete requirements. Prestressed Units shall be regarded as Class 2 elements. 3. Drawings and calculations are to be submitted to the requirements of this sub-section. Tables of design values that have been independently assessed and authorised under Part B of the Technical Schedule of the Registered Firms Scheme may be accepted as part of the calculations. 4. The Contractor shall always submit details of his proposed concrete mix and of all its constituents for approval. 5. The specification requirements of the Registered Firms Scheme for Materials, Workmanship and routine testing during manufacture supersede any corresponding requirements elsewhere in this subsection. All other aspects of the work including provision of off-site inspection facilities, transportation and erection of units on site remain subject to the requirements of this specification. 25 B REINFORCEMENT AND PRESTRESSING STEEL Standard: To BS 4449 or BS B TOLERANCES The Contractor shall advise of the probable camber expected in the floor units. Where deviations from the stated camber cause additional expenses to be incurred in finishing trades, the Contractor shall reimburse such extra costs. Dimensional tolerances on the units, however, shall be in accordance with BS Clause Tolerance on the length of units, however, shall be ±12mm. 35 B LIFTING FIXINGS AND ATTACHMENTS Lifting eyes, bolts, cast-in sockets or other lifting or handling devices shall be provided by the manufacturer and shall be designed to carry the maximum load which could occur at the point of attachment during lifting, handling or erection plus an impact allowance of 100%. The manufacturer or Contractor shall ensure that all such devices are located and embedded in the units in accordance with the makers' specification or where these do not exist, with established engineering principles. The use of the reinforcement projecting from the unit will not be permitted for lifting, handling or erection purposes. 40 B BEARING End bearing of floor units to be in accordance with BS , Clause clarkebond Page 2 of 6

3 45 B DRAWINGS AND CALCULATIONS A reasonable time, to be agreed with the CA (Leadbitter), prior to the commencement of manufacture the Contractor shall provide the CA with three copies of the following: (a) Drawings showing general arrangement and typical details of the pre-cast floors and stairs. (b) Calculations, pre-stressing data and manufacturing details verifying the structural capacity of the units to be provided. One copy will be forwarded to the Local Authority as an addendum to the Building Regulation Submission. In the event of any details not being to the satisfaction of the CA then these should be amended by the Contractor and further copies of the amended details provided. 55 B MODIFICATIONS Do not modify the details from the accepted drawings and specifications without written consent of CA. Arrange units as indicated on contract drawings. 56 B CUTTING Site cutting to reduce length, width or depth of units will only be allowed with the written permission of the manufacturer. Where cutting is allowed it shall be undertaken using methods which do not cause spalling of the concrete. 57 B HOLES AND CHASES Small holes not exceeding 50mm diameter and chases, either of which do not require cutting of reinforcement, may be formed on site, with agreement of the CA. Larger holes shall be formed at the time of manufacture. 60 B MARKING Units shall have identification marks on the top surface, relating to the marks shown on the layout drawings. Where necessary the word 'Top' shall also be marked on the top surface. 65 B SPECIAL UNITS Factory made to accommodate large holes, skews and narrow closers. 70 B REINFORCEMENT The manufacturer shall provide: 1. Principal reinforcement to satisfy the design requirement. 2. Continuity, tying and anti-crack reinforcement to satisfy the design requirements and typical contract drawing details. 3. Reinforcement in pre-cast units to resist stresses due to handling and transport as necessary or as directed by the CA. 4. Adequate supports to reinforcement to prevent its displacement during concreting. 71 B COVER Reinforcement cover to be not less than 15mm of concrete to both external surfaces or any surface adjacent to an internal void in any unit. The units forming the ground floor will be in an external environment. (The insulation and moisture control membranes being above the slab) Enhanced cover to achieve protection as defined by XC4 to BS 8500 part Refer also to clause Fire Resistance. 75 B VOIDED UNITS Minimum thickness of concrete to be 25mm or such greater thickness as the manufacturer may specify, or as may be necessary to comply with clause on concrete cover. 85 B CAMBER Differential camber of the pre-cast units immediately prior to grouting shall not exceed 15mm. Propping of units during grouting shall not be used to reduce differential camber. The ceiling finish is painting only, the differential camber shall not exceed 3mm and the soffit and joints between completed units shall b ea fairfaced finish. clarkebond Page 3 of 6

4 90 B RELATIVE DEFLECTION Longitudinal edges of pre-cast units shall be formed such that, after grouting of joints, relative deflection of the individual units is effectively prevented. 95 B UPPER SURFACE FINISH Upper surface of the units, joints and structural concrete toppings: Left flat in manufacture and suitable to receive a direct application of insulation and a floating sand: cement screed. PROPRIETARY FLOORS/ ROOF DECKS 130 PRECAST SLAB Manufacturer: To be approved - Product reference: To be approved Slab type: 1200mm wide hollow core Slab depth: As drawings but 150mm for upper floors and 260mm for ground floors. Finish: - Soffit: Upper floors: Exposed, smooth fair faced soffit. Ref E60/85B. Ground floor, exposed to the ground so suitable concrete cover needed re durability but no special visual requirements. - Top surface: Flat to receive membranes, insulation and floating screeds. In situ continuity reinforcement: Upper floors: H12x1200mm long reinforcing bars at 400mm centres in slots across all internal supports. Seal open / slot ends prior to placing concrete fill. Other requirements: Preform Builders work holes as required. Place hangers in joint to all corridor locations for supporting services. 180 PRECAST STAIRS AND LANDINGS Manufacturer: To be approved Product reference: To be approved Parameters: Live load to be a minimum of 4kN/square meter. Balustrade to be bolted to the side of stair treads. Dimensions to Architects requirements. Support details to be coordinated with steel frame. To be mechanically fixed to the steel frame at all support points. Span, as the drawings. Fire rating. 60 minutes. Finish: - Exposed faces: Fair faced suitable for painting. - Treads and risers: To receive nosings and vinyl finishes to Architects requirements. Other requirements: [ ] GENERAL/ PERFORMANCE 240 DETAILING OF PROPRIETARY SYSTEM Installation details: Submit location and assembly drawings showing every aspect of the construction, incorporated components and features, trimming for voids, holes for services and related work by others. - Purpose: To allow checking of compatibility with surrounding structure and coordination of services. Method statement and risk assessment for installation: Submit. Programme: Submit well in advance of construction. 250 CONTRACTOR DESIGN Standard: Complete the design in accordance with BS Composite construction: Not anticipated - Fully precast construction: Provide diaphragm and tie action to all upper levels. clarkebond Page 4 of 6

5 262 B UNITS Requirement: Designed as simply supported. 265 STRUCTURAL PERFORMANCE OF FLOOR Loads: The floors must safely support the maximum combination of dead and imposed loads both in the finished building and during construction. Dead loads: (unfactored) - Distributed load of finishes/ fixtures: 2.3 kn per square meter - Concentrated loads: Allow for a 140mm blockwork partition line load of 7.2 kn per m at any location on each unit. Imposed loads: - Distributed loads: 4.0 kn per square meter generally. (7.5 per square meter for plant rooms) - Concentrated loads: TBA Deflection (maximum): span / 300 max Diaphragm/ tie action: Required to all upper floors. 270 STRUCTURAL PERFORMANCE OF ROOF DECK Loads: The roof decks must safely support the maximum combination of dead, imposed and wind loads both in the finished building and during construction. Dead loads: - Distributed load of finishes: 2.5 kn per square meter - Concentrated loads: TBA Imposed loads: - Distributed loads for access/ maintenance: 1.5 kn per square meter - Concentrated loads: TBA - Basic snow load: 2.0 kn per square meter accidental drift load. Wind loads: Calculate to BS , Standard Method. - Basic wind speed (V b ): 24m/s - Altitude factor (S a ): 1 - Direction factor (S d ): 1 - Seasonal factor (S s ): 1 - Probability factor (S p ): 1 - Terrain and building factor (S b ): 1 - Size effect factor: 1 Deflection (maximum): span / 300 Diaphragm/ tie action: Required. 280 BASIC FIRE RESISTANCE Duration: 60 minutes to all floors and stairs Method of determination: To BS , section 4 or by testing to BS or BS EN Finishes: Determine fire resistance without regard to applied finishes. - Data: Submit certificates, tabulated data or calculations. INSTALLATION 300 B PROTECTION OF PRECAST UNITS Requirement: Adequately protect at all stages of manufacture, handling, storage and during erection on site. Units will be rejected when, in the opinion of the Engineer, they sustain any damage that will affect their structural performance. Examples of this damage are broken edges, whether the reinforcement is exposed or not, cracks other than hair cracks, repairs, misplaced reinforcement, honeycombing, airholes, winding, bowing or any other defects. Rejected units: Replace and any delay caused by the rejections will not relieve the Contractor s responsibility with regard to completion within the contract period. 305 B PROPPING Provide adequate propping to prevent construction loads causing excessive deflection or damage to the supporting structure. Props to be carried down to construction strong enough to clarkebond Page 5 of 6

6 provide adequate support. Provide horizontal and vertical bracing as necessary. Details of propping to be submitted to CA for approval. 310 B GENERAL REQUIREMENTS Storage: Store units clear of the ground on level bearers correctly positioned to prevent damage and induction of excessive stresses. Lifting: At designed lifting points, using special lifting devices and cradles as necessary. Bearings: Set on level bearings ensuring not less than the minimum seating recommended by precast unit manufacturer. Site formed openings and sinkings: As precast manufacturer s recommendations. Cutting/ drilling: Do not cut or drill units except as recommended or agreed by manufacturer. Refer also to clauses 56 B and 57 B. 320 A CONCRETE INFILL Designated concrete: To BS Designation: RC25/30 - Aggregate size (maximum): 10mm maximum generally but 6mm in shear keys between pre cast units. Preparation: Thoroughly clean and wet surfaces of precast units. Seal open ends of units/infill blocks with mortar or concrete before placing structural concrete. Conduits/ other services: Not to be placed in structural toppings, without approval of the CA. Placing: Avoid segregation and compact thoroughly to eliminate voids. - Extent: Fill troughs and other holes. - Finish: Flush with top of precast units. Protection: Prevent movement of units until concrete has gained sufficient strength. 325 A GROUTING Mix: 1:6 cement: sharp sand (1:4 in wet weather) Preparation: Thoroughly clean and wet surfaces of precast units. Fill all joints and surface irregularities. Method: Brush in grout, first in direction of joists, then across. 350 A LEVELS OF STRUCTURAL CONCRETE FLOORS Tolerances: As clause E20/311B. clarkebond Page 6 of 6