SPECIFICATION AND STANDARD FOR STRUCTURAL STEELWORK: GENERAL PART 8 - BOLTING AND RIVETING

1.11.1       Ordinary Bolts and Nuts

1.11.1.1    Ordinary bolts and nuts shall comply with BS 3692, BS 4190 and BS 4933.

1.11.1.2    All ordinary bolts shall be fitted with washers and nuts complying with BS 4320.  Nut shall be of at least the strength grade appropriate to the grade of the bolt used. Tapered washers shall be used where necessary.

1.11.2       High Strength Friction Grip Bolts

1.11.2.1    The  use  of  high  strength  friction  grip  bolts  and  associated  nuts  and  washers complying with BS 4395 shall be in accordance with BS 4604.

1.11.2.2    Other types of friction grip fasteners may also be used subject to the approval of the Engineer provided they have mechanical properties not inferior to bolts complying with BS 4395 and provided they are capable of being reliably tightened to the minimum shank tensions specified in BS 4604.

1.11.3       Surface Finish

1.11.3.1    Bolt assemblies in externally exposed locations are to be galvanised in accordance with BS EN ISO 1461.

1.11.3.2    In  addition  to  all  other  testing  requirements,  galvanised  grade  8.8  bolts  and galvanised HSFG bolts shall be tested for head soundness according to Appendix 

D9 of BS 3692 and also subjected to supplementary tensile testing to confirm their mechanical properties. Each test is to be carried out on 1% of the total number in each batch of galvanised bolts.

1.11.4       Holes

1.11.4.1    All holes shall be drilled or sub-punched and reamed.

1.11.4.2    Holes for ordinary bolts shall not be more than 2mm greater in diameter than the bolt for bolts not exceeding 24mm diameter and not more than 3mm for bolts over 24mm diameter, unless otherwise specifically required by the design.

1.11.4.3    Holes for friction grip bolts shall be in accordance with BS 4604.

1.11.4.4    Holes for bolts shall be formed by drilling and all burrs shall be removed before assembly.

1.11.4.5    Holes for fitted bolts or pins shall have a diameter equal to or not more than 0.15mm of the nominal diameter of the bolt or pin.

1.11.5       Protection of Hollow Section

1.11.5.1    Where a sealed hollow member is holed by a fastener or pin, provision shall be made to prevent ingress of moisture to the interior of the member. If not shown on the Drawings, the Contractor is to propose the method on the Shop Drawings.

1.11.6       Limits to Length

1.10.6.1    The length of bolts is to be such that at least one clear thread shows above the nut after tightening, and at least one thread plus the thread run out is clear between the nut and the unthreaded shank of the bolt.

1.11.7       Foundation Bolts

1.11.7.1    Foundation bolts shall be cast in to the dimensions shown in the Drawings. The Contractor  shall ensure that  the projecting  ends of  the  bolts  are free  to  move horizontally. The projecting ends of bolts shall be well greased and wrapped in sacking that shall remain in position until the commencement of steelwork erection.

1.11.7.2    Prior to delivery of steelwork for erection, the Contractor shall check the concrete bases or seatings for level, setting out, projection and full degree of adjustment of the holding-down bolts.

1.11.7.3    The Contractor shall remedy any discrepancies or inaccuracies to the satisfaction of the Engineer. Modification to the steelwork, bending of the holding-down bolts or the use of excessive number of washers to accommodate errors in position and projection of bolts shall not be carried out except with the written permission of the Engineer.

1.11.8       Grouting

1.11.8.1    Grout around foundation bolts and under column base plates is to be supplied and placed by the Contractor and is to have a minimum compressive strength at 28 days of 60 N/mm2.

1.11.8.2    The grout mix shall be polymer based, prepared, mixed and placed in accordance with the manufacturer’s specifications approved by SCI.

1.11.8.3    Grouting under the column bases shall only be carried out after a sufficient portion of the steel structure has been aligned, levelled, plumbed and adequately braced by other structural components which have been levelled and are securely held by their permanent connections. Immediately before grouting, the space under the column base plates is to be clean and free of all extraneous matter.

1.11.9       Riveting

1.11.9.1    The use of rivets shall be in accordance with BS 4620.

SPECIFICATION AND STANDARD FOR STRUCTURAL STEELWORK: GENERAL PART 7 - WELDING

1.10.1       General

1.10.1.1    All metal on metal welding shall be done in accordance with BS EN1011 and AWS D1.1.    Spot  welding  of  cold-formed  steel  sections  shall  also  conform  to  the requirements outlined in the above standard.

1.10.1.2    All butt welds shall be full penetrations unless noted otherwise.  All fillet welds shall be 6mm continuous unless noted otherwise.  All welds shall be chipped free of slag.

1.10.2       Welding Electrodes

1.10.2.1    Electrodes shall be of approved types conforming to AWS D1.1 and shall be kept in a dry store in unbroken packets.

1.10.3       Details of Welding Procedures

1.10.3.1    The general procedures for shop and site welds and other details shall be submitted in writing, in accordance with AWS D1.1, to SCI for approval before fabrication.

1.10.4       Approval and Testing of Welding Procedure

1.10.4.1    The Contractor shall carry out welding procedure tests in accordance with AWS D1.1, to demonstrate by means of a specimen on a steel representative of that to be used that he can produce satisfactory welds with the proposed welding procedure.

1.10.5       Approval and Testing of Welders

1.10.5.1    The Contractor shall satisfy SCI that his welders are suitable for the work upon which they are employed.  Welders working to approved welding procedures shall satisfy the relevant requirements of AWS D1.1.

1.10.6       Measurement of Weld Sizes

1.10.6.1    The Contractor shall provide gauges necessary for the measurement of weld sizes.

1.10.7        Site Welding

1.10.7.1    No site welding shall take place unless shown in the Shop Drawings or otherwise approved. Where site welding is required or permitted the Contractor shall submit details of staging, platforms and weather protection for welders and materials. Site welding shall be subject to all the requirements of welding as defined in this section of the Specification.

1.10.8       Quality of Weld

1.10.8.1    All welds shall be visually inspected as per AWS D1.1. All non-destructive testing shall  be  as  per  AWS D1.1.  Any  weld  with  defects  greater  than  the  maximum permitted as in the Code shall be liable to rejection.

1.10.9       Frequency of Testing

1.10.9.1    Visual Inspection

All welds are to be visually inspected.

1.10.9.2    Selection of Welds to be Examined

1.10.9.3    Where  there  is  a  requirement  for  less  than  100%  examination,  the  method  of selection of welds to be examined is to be agreed with the Engineer before the commencement of work.

1.10.9.4    Where examination reveals unacceptable defects in a joint, two additional joints in the group represented by the joint are to be examined. If the results on these two additional joints are acceptable then the original weld may be repaired and re- examined by similar means.

1.10.9.5    If the non-destructive examination of the two additional joints reveals unacceptable defects, examine each joint in the group.

1.10.9.6    The cost of testing, examining and repair of welds that fail to meet the specified requirements shall be borne by the Contractor.

1.10.9.7    Welded connections made on circular hollow sections

The interface on steel plates, steel sections and steel hollow sections which are to be welded to circular hollow sections shall be machine reamed so that the reamed edges match perfectly with the curvature of the CHS at the connections. Thermal cutting of the steel plates, steel sections and steel hollow sections to produce the desired profile at the mating surfaces is not acceptable.

1.10.10     Inspection Authority

1.10.10.1  The examination of welds shall be carried out by approved personnel from the accredited laboratory engaged by the Contractor.