SECTION 15 STRUCTURAL STEEL

Transcription

1 SECTION 15 STRUCTURAL STEEL 1 GENERAL 1.1 SCOPE Outline description This section applies to the provision, fabrication, treatment, erection and connection of structural steelwork. 1.2 CROSS REFERENCES General Conform to the General requirements worksection. 1.3 STANDARDS Site copy Supply and keep on site a copy of AS/NZS 1554, AS ADJOINING ELEMENTS General Provide for the fixing of adjoining building elements to be fixed to or supported on the structural steel. 2 QUALITY 2.1 INSPECTION Notice Give sufficient notice so that inspection may be made at the following stages: - Commencement of shop fabrication; - Commencement of welding procedure tests; - Commencement of welding; - Prior to the placement of the root runs of complete penetration butt welds; - Completion of fabrication prior to surface preparation; - Commencement of surface preparation prior to protective coating; - Completion of protective coating prior to delivery to site; - Steelwork on site prior to erection; - Completion of erection prior to encasing or fixing cladding; - Encasing. Fabrication may proceed In the absence of any directions to the contrary, after the notice, the Contractor may proceed with his obligations under the terms of the Contract, but this shall not be construed as implying any approval or negating the responsibility of the Contractor to complete the work in accordance with all the requirements of the Contract. 2.2 IDENTIFICATION Marks Provide suitable and sufficient marks or other means for identifying each member, including bolts and loose items, and for the correct setting out, location, erection and connection of the steelwork. Steel grade identification To AS 4100, clause November 2007 Page 15/1 Project No /43485 PROJECT SERVICES

2 Connections Mark connections to distinguish those requiring high-strength bolts from others. Deliver bolts of each size and type in separate containers suitably identified. 2.3 HANDLING AND STORAGE Generally To AS 4100, clause Handle and store steelwork so as to protect it from damage, including overstress, distortion, damage to surfaces and applied finishes, contamination by foreign matter, and the like. Rejection Steel not handled or stored in an appropriate manner is liable to rejection. 3 MATERIALS 3.1 STEEL TYPE AND GRADE Standards Steel shall be of the types and grades shown on the Drawings, to the appropriate material standard, and to AS 4100, Section 2, or AS/NZS 4600 clause 1.5 in the case of cold-formed sections. Compliance with standard For each batch of steel supplied to the Works, provide the manufacturer's Certificate of compliance and Test certificates. Independent tests Alternatively, have the steel independently tested to AS/NZS 3678 or AS/NZS 3679, for compliance with the chemical composition and mechanical test requirements of the appropriate material standard. Testing certification Use NATA registered bodies for testing and certificates unless approved otherwise. In this Section understand that the word 'certificate' means certificate by NATA registered body, unless approved otherwise. Rejection Steel which cannot be shown to comply with the appropriate material standard is liable to rejection. 3.2 BOLTS High strength bolts, nuts and washers To AS/NZS Lengths and washers for high-strength bolts: Use bolts threaded with length sufficient to prevent threads in section at interfaces of connected parts of the work. Use washers, flat or tapered as necessary, for each nut and for each head which is to be rotated. Commercial mild steel bolts To AS Particular requirements, commercial bolts: Unless otherwise shown or directed, use mild steel drop forged bolts with hexagon heads and nuts and ISO metric coarse pitch threads. Use bolts threaded length sufficient to prevent threads in section at interfaces of connected parts of the work. Use washers, circular, clipped, flat or tapered as necessary, for each nut and for each head which is to be rotated. Mild steel nuts To AS Mild steel washers To AS Coatings, bolts Coat bolts, nuts and washers as follows: - For steelwork to be hot dipped galvanised (GALV) - Hot dipped galvanised. Project No /43485 Page 15/2 November 2007 P:\28369\43485\Worddata\AD\spec\ UPDATED SPECIF\15 Structural steel.doc

3 - For steelwork to be primed with Special Purpose Primer (IP2) - Hot dipped galvanised. 4 FABRICATION 4.1 FABRICATION Standard To AS 4100, Section 14. Fabrication Fabricate in an approved workshop unless otherwise specified or permitted. Cutting Saw cut ends of hot rolled steel sections, cold formed steel sections and steel tubes. Other sections may be cut by shearing, cropping or sawing. Do not use hand operated flame cutting tools. Machine flame cutting may be used for the preparation of edges for welding, but surfaces shall be smooth, uniform, free from fins, tears, loose scale, slag, rust, grease, paints, any other foreign material and other defects. Splices and joints Structural members shall be in single lengths unless otherwise required by the Contract or permitted. Welding of off-cuts Do not weld 'off-cuts' or short lengths to make up the required length of any member. Permission may be given by the Superintendent to join, by one weld, members of long final length, provided written request from the Contractor is so received. Fabrication tolerances To AS 4100 clause Straightness: To AS 4100 clause Straightening methods: Submit proposed methods for approval by the Superintendent. Beam camber: If beam members have a natural camber within the straightness tolerance, fabricate and erect them with the camber up. Machined surfaces: To AS 4100, clause Temporary connections Do not locate cleats other than as shown on the shop Drawings without prior permission. Remove temporary connections on completion and restore the permanent surface. Holes for bolts To AS 4100, clause Do not use flame cutting for any holes. 4.2 WELDING Standards To AS 4100, clause , and AS/NZS Stud welding To AS/NZS 1554 Part 2. Site welds Do not site weld without prior permission. Wherever possible locate site welds in positions for down hand welding. Weld categories Use SP (structural purpose) category welds to AS/NZS 1554, unless noted otherwise. Use GP (General Purpose) category welds to AS/NZS 1554 for purlin and girt cleats. Qualification of welding personnel Welding operators shall have passed the tests specified in AS 1796 and be in possession of the appropriate certificate issued by an examining authority specified therein. November 2007 Page 15/3 Project No /43485 PROJECT SERVICES

4 Weld testing If weld testing by radiographic, ultrasonic or visual examination is called for on the Drawings or specified, have the tests performed by an independent testing authority, and submit the relevant test report to the Superintendent, before the tested steelwork is delivered to the site. Visual inspection To AS/NZS Clause 7.2, 7.3. VISUALLY EXAMINE 10% of SP welds to Table of AS/NZS Radiographic examination: To AS/NZS , clause 6.3. Ultrasonic examination: To AS/NZS , clause 6.4. Weld test failure If a weld fails a required test, test a further sample of welds in the group at the same rate as the original test rate, up to a maximum of 100% of the group. If any welds in the second sample fail the test criteria, then test all the remaining welds in the group, up to 100% of the group, at the Contractor s expense. Correction of non conforming welds To AS/NZS , clause 5.8. After correcting a non-conforming weld revealed by a required test, retest it as specified above under WELD TESTING. 5 ERECTION 5.1 ERECTION Standard To AS 4100, Section 15. Erection tolerances To AS 4100, clause Beam clearances at each end, maximum: 2 mm for web cleated ends, 3 mm for ends without web cleats. Anchor bolt position tolerances: - Deviation of a bolt within a bolt group 3 mm; - Deviation between groups 6 mm; - Maximum accumulated deviation between groups 6 mm per 30 m; - Centre of bolt group off grid - not greater than 6 mm; - Projection of bolt end + 25 mm, - 5 mm. Grouting supports To AS 4100, clause Grout type and strength: Unless shown otherwise on the Drawings, 40 Mpa non-shrink cementitious proprietary grout. Bolting To AS 4100, clause FINISHES 6.1 SURFACE PREPARATION Preparation On completion of shop fabrication, and prior to erection on site and irrespective of any prior application of paint to the steelwork, clean steelwork as follows: Project No /43485 Page 15/4 November 2007 P:\28369\43485\Worddata\AD\spec\ UPDATED SPECIF\15 Structural steel.doc

5 - For steelwork to be encased in concrete - to a finish equivalent to Class Sa 1 finish described in AS For steelwork to be hot dip galvanised - clean by suitable preliminary treatment and subsequent acid cleaning or pickling to produce a clean metallic surface suitable for galvanising. - For all other steelwork - by abrasive blast, to a standard of finish equal to or better than Class Sa 2-1/2 finish described in AS No free silica Any substance, including sand, containing free silica shall not be used as an abrasive in any blast cleaning operations. Reclean Prior to application of paint, re-clean as specified above any cleaned surfaces left unpainted longer than 4 hours after prior cleaning. Prior to encasement, re-clean as specified above any surface to be encased which does not have a standard of finish equal to or better than Class Sa 1 of AS PAINTING Coating systems Apply the paint coating systems (including both decorative and protective coatings) shown on the Drawings. Australian paint approval scheme The paint specification references stated below refer to Australian Paint Approval Scheme (APAS) published specifications. Priming Prime as follows: - Special Purpose Primer (IP2) - Paint steelwork (except where galvanised or to be encased in concrete) with a two-pack inorganic ethyl silicate zinc primer to APAS 2908 depositing a minimum of 75 microns dry film thickness on the substrate applied in one coat. Drying time Carryout painting, unless otherwise specified, within 4 hours of cleaning and allow 24 hour drying time before recoating and 72 hour drying time before commencing delivery to site. Unpainted areas Do not paint contact surfaces of high strength friction-grip bolted connections, surfaces against which concrete is to be poured, and surfaces within 50 mm of locations where "field welds" are required. Column bases Where steel columns have encased bases, extend the priming of the shaft 25 mm below the top of the encasing. After erection On completion of bolting or site welding, clean with a wire brush or other acceptable methods, bolts, damaged areas of paint and galvanising and areas previously specified to remain unpainted, to an equivalent standard specified, then treat as follows: - For prime painted steelwork - feather any existing paint to a fine edge. Repaint cleaned areas with primer specified above, overlapping existing paint by 25 mm minimum. - For galvanised work (GALV)- apply one coat of 50 microns dry film thickness of an approved single pack epoxy zinc rich paint to APAS 0014/1 made by a manufacturer approved by APAS to manufacture that product. Approved paint manufacturer Use paints made by a Manufacturer approved by the APAS to manufacture the paint. Use the same brand of paint for subsequent touch-up and additional coats. Paint gauge Upon request provide the Superintendent with an approved thickness gauge such as an 'Elcometer' for use in testing paint thicknesses. November 2007 Page 15/5 Project No /43485 PROJECT SERVICES

6 6.3 GALVANISING Structural sections To AS/NZS 4680 and HEAVY DUTY GALVANISED COATINGS worksection requirements. Threaded fasteners To AS Distortions If any member is distorted during the galvanising process, submit the proposed method of straightening to the Superintendent. Components in contact with concrete Passivate galvanised surfaces to be cast into or in contact with concrete by dipping in 0.2% sodium dichromate solution. Coating quality The zinc coating shall be free from lumps, blisters, gritty areas, uncoated spots, acid and black spots, dross, flux and other imperfections. Site welding Grinding of edges: Permitted. Weld areas: Reinstate coating. Site coating reinstatement Extent: Areas damaged by transport, site welding, site flame cutting, site handling, or erection. - Size of area to be repaired: Relevant to the size of the article and the conditions of service. Method: Wire brush or mechanically buff the surface. Apply zinc-rich primer to 150 µm dry film thickness. Stipple edges of the primed area. - Paint standard: To APAS-0014/1 or APAS Surface preparation: To AS and Grade St 2 to AS PERFORMANCE CRITERIA ELEMENTS 7.1 PERFORMANCE CRITERIA ELEMENTS Responsibility Take responsibility for the design and construction of all performance criteria elements specified or shown on the drawings, and comply with parameters specified. Supply to the Superintendent, a certificate from a practicing Structural Engineer to the effect that the design complies with the parameters specified and that the design has received an independent check for compliance with the structural provisions of the Standard Building By-laws. Supply to the Superintendent, on request, a copy of engineering calculations in support of the Structural Engineer's certificate. Incompatibility Include for the following where the design details of the performance criteria element(s) are incompatible with the rest of the structure: (i) (ii) (iii) Any redesign and/or redocumentation required to any or all parts of the structure. Amendment/alteration to any or all parts of the structure including amendment/alteration to associated internal and external finishes. Any delays occurred caused by redesign, redocumentation or amended/altered construction requirements or procedures. Satisfactory redocumentation: Any redesign and/or redocumentation necessary to comply with the foregoing shall be to the satisfaction of the Superintendent. A decision of the Superintendent in regard to the necessity for any redesign and/or redocumentation shall be binding in respect of this clause. Project No /43485 Page 15/6 November 2007 P:\28369\43485\Worddata\AD\spec\ UPDATED SPECIF\15 Structural steel.doc