GENERAL
Cross-reference
General: Read with A90 General technical requirements.
DESIGN
Completion of design
Alternative design standards:
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Structural use of steelwork in building: To BS 5950-1, -2, -3.1, -4, -5 and -8.•
Design of steel structures. General rules and rules for buildings: To BS EN 1993-1-1 Eurocode 3 (together with United Kingdom National Application Document).Loading
Dead and imposed loads: To BS 6399-1. Wind loads: To BS 6399-2.
PRODUCTS
Steel Sections
Hot rolled sections:
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Material: To BS EN 10025.•
Dimensions and mass: To BS 4-1.Hot finished structural hollow sections: To BS EN 10210. Cold formed structural hollow sections: To BS EN 10219. Galvanized structural steel strip and sheet: To BS EN 10326.
Galvanized structural steel strip and sheet for cold forming: To BS EN 10327.
Fasteners
ISO metric black hexagon bolts, screws and nuts: To BS 4190.
High strength friction grip (HSFG) bolts, associated nuts and washers – General grade: To BS 4395-1. High strength friction grip (HSFG) bolts, associated nuts and washers – Higher grade: To BS 4395-2. Direct tension indicators:
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Compressible washers: To BS 7644-1.•
Nut face and bolt face washers: To BS 7644-2. Coatings on metal fasteners:•
Hot dip galvanized: To BS 7371-6.•
Sherardized: To BS 7371-8.Coatings
Cleaning and preparation of metal surfaces: To BS 7773.
Hot dip galvanized coatings on fabricated iron and steel: To BS EN ISO 1461.
Corrosion protection of steel structures by protective paint systems: To BS EN ISO 12944-1 to -8.
Fire resistance testing
General requirements: To BS EN 1363-1. Loadbearing elements:
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Floors and roofs: To BS EN 1365-2.•
Beams: To BS EN 1365-3.•
Columns: To BS EN 1365-4.Filling/ bedding of column bases
Portland cement: To BS EN 197-1.
Sand: To BS EN 12620, grade 0/4 or 0/2 (MP).
EXECUTION
Notification of commencement
Give notice: Before fabrication is due to start.
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Minimum period of notice: Five working days.Faying surfaces for high-strength friction grip (HSFG) joints
Steel 25 mm thick or more: Check faying surfaces for deformities that may reduce slip factor to below design limit. Remedial measures: Submit proposals.
Protection: Immediately after blast cleaning and before coating surrounding areas, mask faying surfaces to protect from contamination and deterioration.
Applying coatings: Step each coat 30 mm back from edge of preceding coat and away from masked areas.
Removal of protection: Immediately before bolting, remove masking. Check faying surfaces are free from adhesive. Clean with solvent if necessary.
Preparation for galvanizing
Cutting, welding and drilling: Complete before galvanizing. Vent and drain holes: Provide as necessary. Seal after galvanizing.
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Locations: Submit proposals.•
Method of sealing: Submit proposals.Offsite preparation and painting
Working area: Covered and properly lit, heated and ventilated. Sequence of working: Select from the following and submit proposals:
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Fabricate, blast clean, prime.•
Blast clean, fabricate, remove flash rust with a light overall sweep blast, prime.•
Blast clean, apply weldable prefabrication primer, fabricate, prime.Prefabrication primer: Type recommended by manufacturer of post fabrication primer.
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Thickness of post fabrication primer coat: May be reduced if and as recommended by manufacturer.Surfaces inaccessible after assembly: Apply full treatment and coating system including, if necessary, local application of site coatings.
Manual cleaning of new steelwork
Preparation: Remove fins, burrs, sharp edges, weld spatter, loose rust and loose scale. Surface finish: Clean but unpolished to BS EN ISO 8501-1, grade St 2.
Finishing: Thoroughly degrease and clean down. Remove any consequent rusting back to grade St 2. Prime without delay.
Site welding
Use: Permitted only where indicated on drawings.
Working conditions: Suitable and safe. Do not weld when surfaces are wet or when ambient temperature is below 0°C. Finished welds: Carefully dressed to remove slag without deforming surface of weld.
Sealed hollow sections
Bolt holes: Sealed to prevent access of moisture.
Pre-erection checks
Scope: At least 7 days before proposed erection start date, check the following:
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Foundations and other structures to which steelwork will be attached: Accuracy of setting out.•
Holding down bolts: Position, protruding length, slackness and condition. Inaccuracies and defects: Report without delay.Permission to commence erection: Obtain.
Modifications
Steelwork: Do not modify without approval.
Direct tension indicators
Grade: Appropriate for grade of bolt and nut assembly.
Ancillary components: Used as recommended in BS 7644-1, Annex A.
Post installation and inspection treatment: Where no further protective coating is specified, apply a butyl rubber sealing compound to seal measuring gap around indicators.
Column bases
Levels: Adjust with steel shims or folding wedges no larger than necessary.
Location of shims/ wedges: Symmetrically around perimeter of base plate. Do not use a single central pack. Give notice: If space beneath any column base is less than, or over 25 mm greater than, the specified dimension.
Accuracy of erection: Check, and correct errors before filling and bedding beneath bases and carrying out other adjacent work.
Mortar filling/ bedding of column bases
Bolt pockets: Completely filled with neat cement slurry. Spaces beneath base plates: Completely filled:
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Spaces 25–50 mm deep: 1:1 cement:sand mortar, just fluid enough to pour, well tamped as filling proceeds.•
Spaces 50–80 mm deep: 1:2 cement:sand mortar, just damp, well tamped against properly fixed supports as filling proceeds.Bonded anchors
Holes: Clean and free from dust at time of installing anchor.
Permeable sleeves: Use in conditions where otherwise the loss of bonding agent would be unacceptably high.
Fixing profiled sheet for floor slabs
Standard: To BS 5950-4.
Preparation of fasteners for site painting
Uncoated fasteners: After steelwork erection and before applying site coatings, thoroughly degrease and clean. Without delay, coat to match adjacent shop painted areas.
Site painting
Environmental conditions prior to starting coating work:
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Surfaces: Unaffected by moisture or frost.•
Steel temperature: At least 3°C above dew point, with conditions stable or improving, and not high enough to cause blistering or wrinkling of the coating.•
Relative humidity: Below 85%. Coatings:•
Surfaces to be coated: Clean, dust free and suitably dry. Previous coats to be adequately cured.•
Multiple coats of same material: Use different tints to assist checking of complete coverage.•
Penultimate coat: Colour recommended by paint manufacturer to suit top coat colour.•
Finish required: Smooth and even, of uniform thickness and colour, free from defects.External angles, nuts, bolt heads, rough weld seams, and areas difficult to coat: Apply an additional stripe coat.
Exposed steelwork partially embedded or encased in concrete: Apply two coats of bituminous coating locally to the steel/ concrete junction.