SECTION I : FABRICATION & TRANSPORTATION

STRUCTURAL STEELWORK

SECTION I : FABRICATION & TRANSPORTATION

1. GENERAL

The members and bracing shall be of structural steel fabricated by electric arc welding processes and connected in the field by means of bolts, welding and connecting links. All workmanship shall be of first class quality in every respect, the greatest accuracy being observed to ensure that all parts will fit together properly on erection.

2. MATERIALS AND TESTING

All steel used shall be in accordance to BS EN 10025, BS EN 10210 or equivalent. Sections rolled from mild steel shall conform to BS 4, BS EN 10056, BS EN 10210, BS EN 10219 or equivalent. Electrodes shall conform to the requirements of BS EN 440, BS EN ISO 2560, BS EN 756, BS EN 1668. All black bolts, screws, nuts and washers shall conform to B.S. 3692, B.S. 4190 & B.S. 4320. High strength Friction Grip Bolts, nuts and washers shall be of approved manufacturer and shall comply with the requirements of B.S. 4395. Manufacturer's Test Certificates for all steel used for fabrication and for bolts for the work shall be supplied. These shall include all the mechanical tests described in the appropriate specification and also a chemical analysis. No materials shall be used in the steel work until it has been identified with the tests and inspected or otherwise approved by the Engineer, except in the case of minor parts or materials for which this requirement may be waived by permission in writing from the

Engineer. All steel shall be new and shall be free from cracks surface flaws, laminations, rough

jagged or imperfect edges and faces, slag inclusions and all defects.

3. SHOP DRAWINGS

The Contractor shall be responsible for the preparation of shop drawings which shall give complete information necessary for the fabrication of the component parts of the structure including the location, type, size and extent of all bolt holes and welds and the electrodes to be used and the sequence of welding which shall be controlled to minimize contraction stresses and distortion. The drawings shall be submitted to the Engineer for approval not less than twenty one (21) days before the fabrication of the steelwork is due to be commenced and no

fabrication shall be carried out until such approval is given. The instructions and directions given on the drawings shall not be varied without further approval in writing. - SS 1 - Approval by the Engineers of shop drawings shall indicate that the general requirements of the structural design have been satisfied. Approval shall not be taken to imply that the dimensions or the correct matching and design of connections or joints have been checked and this will remain the responsibility of the Contractor. Drawings submitted for approval shall be of good standard and any drawing which clearly requires considerable amendment will be returned for alteration without a detailed review of all the corrections which may be required. The Contractor shall supply to the Engineer two complete sets of shop drawings. After drawings have been submitted to the Engineer for approval one (1) complete set shall be return to the contractor, each drawing having been given one of the following classifications. Approved In this case the drawing is satisfactory and fabrication may proceed. Approved Subject In this case the drawing is to Amendment substantially satisfactory except for small changes required. The drawing shall be amended by the Contractor and submitted again for approval. However, fabrication need not be held up pending final approval. Rejected In this case a drawing is considered by the Engineer to require major alteration and must be re-submitted. Fabrication shall not commence until the re-submitted drawing has been returned marked "Approved" or "approved Subjected to Amendment". 4. WEIGHT OF STEELWORK All sizes shown on the drawings are not sizes after machining and the Contractor shall allow for the difference between this weight and the actual gross weight required. 5. MEASUREMENT All measurement shall be made by means of an approved steel tape. Dimensions of all steelwork given on the drawings are to be assumed to obtain at a temperature of 720F/220 Celsius. 6. UNIVERSAL PLATES AND FLATS Universal  lates or flats with reasonable square and true rolled edges will be accepted as a substitute for plates of flats with sheared flame cut or machined edges except that such plates or flats shall not be used if the main stresses to which they are subjected are other than in the direction of rolling. Where universal plate or flat is to be fillet welded along its edges, the radius at the edge

shall not exceed forty (40) per cent of the nominal fillet weld. -SS 2 - 7. STRAIGHTENING Before any other work is done on them all plates shall be flattened and all bars and sections straightened and made free from twist so that, when assembled, adjacent surfaces shall be in close contact throughout. The method adopted for the above work shall be such as not to injure or mark the material. Lateral Variation of compression members shall be not greater than one thousandth (1/1000) of the axial length between points of lateral support. For other members lateral variation shall not exceed two thousandth (2/1000) of the axial between supports. 8. CUTTING Unless otherwise specified, steelwork may be cut by shearing, cropping, sawing or flame cutting. Surfaces produced by such cutting shall be finished square (unless a beveled edge is called for) true and smooth to the required dimensions. Finishing of surfaces shall generally be by machining and/or grinding. In the case of flame cutting, surfaces having  only slight irregularities may be lightly ground only and allowance need not be made in  accordance with other relevant clauses provided that the finished edges are substantially as straight, true, smooth and regular as those produced by the finishing cut of a planning machine. Shearing will not be permitted on plates in the main girder sections. Gusset plates and splice plates may, however, be sheared in a direction perpendicular to the direction of their main stresses. Ends of stiffeners shall be cut and finished to fit tightly to the girder flanges after the flanges have been welded to the web plates and in accordance with relevant clauses. The butting ends of the compression flanges which are required to be part of the moment splice for erection or the butting ends of other compression parts shall be faced after fabrication so as to be in close contact.

9. ALLOWANCE FOR MACHINING AND GRINDING

Where plates are to be sheared or flame cut, the cutting shall permit of at least 3mm of metal being removed from plates 12mm or less in thickness, and at least 6mm of metal being removed from plates over 12mm in thickness.

10. SURFACE FINISH OF MACHINED PARTS

The surfaces to be finished by machining are indicated on the drawings. The machining shall be of the highest quality workmanship and surfaces shall bear to within 0.05 of a mm. Bearing surfaces shall, in addition, be flat to within 0.12 of 1mm. The bearing surfaces at each end of a girder shall be at right angles to the vertical axis of the girder. - SS 3 -

11. HOLING

Finished holes for bolts shall be not more than 2mm in diameter larger than the nominal diameter of the bolt passing through them. Holes shall be drilled. Punching may be permitted provided the holes are punched 2mm less in diameter than the required size and reamed after assembly to the full diameter. The thickness of material punched shall not exceed 15mm.

12. ASSEMBLY

The component parts shall be assembled in such a manner that they are neither twisted  or otherwise damaged. All hollow sections shall be sealed so as to prevent the access of moisture to the interior of the members.

13. INSPECTION OF MEMBERS DURING FABRICATION & UPON COMPLETION

The contractor shall make all necessary arrangements and meet all costs incurred by the Engineer for the purpose of inspecting work and no work shall be erected until it has been inspected and passed. Any work found defective or which is not in accordance with the drawings or this specification may be rejected and shall at once be made good. The Contractor shall supply free of charge all labour, tools etc. required in connection with the inspection of the work.

14. MARKING FOR ERECTION

Each part shall be marked with approved destination marks and stamped with durable markings. Two (2) copies of drawings correctly showing these markings shall be supplied free of charge to the Engineer when the steelwork is despatched.

15. SUPPLY OF BOLTS

(a) Black Bolts

The Contractor shall supply the full number of nuts, bolts washers, etc. required to complete the work in the field. These shall have been dipped into hot boiled linseed oil before delivery. All bolts and nuts shall have heads forged out of the solid truly concentric and square with the shank, with hexagonal heads and nuts of the sized set out in BS 916. Bolts shall be carefully screwed to BS 84 (using medium fit tolerances) and all nuts shall fit hand-tight to the bolts. The bolt shanks shall be straight and true.

(b) High Tensile steel Bolts

All high tensile steel bolts, nuts and washers shall conform to BS EN 14399. Bolts and nuts shall be washer-faced on the bearing surfaces of the head and nut. They shall have been suitably protected before delivery. - SS 4 –

16. PACKING AND MARKING OF FABRICATED STEELWORK

All bolts, nuts, washers, plates under 30cm square, and small articles generally, shall be packed separately to the satisfaction of the Engineer. Marking shall be carefully stencilled on each piece in a conspicuous position.

17. TRANSPORT AND HANDLING

Special care shall be taken in the lifting, handling and transporting of structural steelwork assembled before delivery to ensure protection from damage. In particular, all open joints, gussets and other projecting parts shall be protected to the satisfaction of the Engineer. The methods of transporting and of handling the metalwork shall be subjected to the approval of the Engineer. Any special precaution, safety measures or escorts which may be required for the handling and transporting of large pieces shall be at the cost of the Contractor.

18. DELIVERY AND CUSTODY OF STEELWORK

The Contractor shall ensure the safe delivery of the whole of the steelwork. When making delivery of the metalwork he shall bring immediately to the notice of the Engineer any damage or defects therein and shall make good any such or subsequent damage or defects at his own expense, to the entire satisfaction of the Engineer.

19. BOLTING

Where necessary washers shall be tapered or otherwise suitably shaped to give the heads and nuts of bolts a satisfactory bearing. The threaded portion of each bolt shall project through the nut at least one thread. In all cases where the full bearing area of the bolt is to be developed, the bolt shall be provided with a washer of sufficient thickness under the nut to avoid any threaded portion of the bolt being within the thickness of the parts bolted together. Where a hollow section is drilled to take bolts or studs, provision shall be made to prevent the access of moisture to the interior of the section. For example, a transverse sleeve can be inserted where a bolt passes through a hollow section, or grommets can be used under heads and nuts.

20. WELDING - GENERAL

Welding shall be in accordance with BS 5950, BS EN 1011, all appropriate clauses of these standards shall be taken as being incorporated herein with details of the proposed welding procedure. The tests of welding shall be carried out to BS EN 875, BS 709. All welding shall be carried out under the immediate and continuous supervision of a person who, in the opinion of the Engineer, has had suitable training and practical experience in the execution of this form of construction.

- SS 5 -

Plates and sections shall be reasonably free from slag, oil, grease, paints, rust or heavy scale or any substance which might affect the quality of the weld. A light film of linseed oil may be disregarded. Where a weld is to be deposited on a flame out surface, the surface shall be rendered reasonably free of scale before welding. Portions of plates or sections which are to be welded by a machine welding process shall be completely free of scale and rust for a width of at least 13mm on each side of the weld edge. The landing edges of plate sections to be welded shall be closed by service bolting, cramping, jigs or tack welds. When the work is liable to distortion during the welding, it shall be held in approved frames or jigs. The completed work shall be straight, square and free from twists, bends and open joints, particular care being taken to secure the correct dimensions. Due allowance shall be made for loss of dimensions by shrinkage of welded parts. Wherever possible, or considered to be necessary by the Engineer, the welding shall be carried cut in a manner to minimize distortion and contraction stresses by applying the welding in intermittent stretches and by back-step welding. Where members are cut or machined to finished length after welding, welding shall proceed from the centre towards the ends or outside edge. No member at any time during fabrication shall depart from the straight by more than one in five hundred (1/500) of its length nor shall the longitudinal profile of any girder

vary from that shown on the drawings by more than 3mm. All slag shall be removed and the weld thoroughly cleaned before a run of welding may be superimposed on a previous run. The welding shall be deposited in runs of good clean metal free from slag inclusions and porosity. Tamping or hammering of the metal shall be prohibited, but the slag may be chipped from the metal with a light hammer. The weld shall show a good even contour, and on a cut specimen shall indicate a good fusion with the parent metal. Slag inclusions or welds showing porosity shall be cut out and re-welded. When the V of single V or the first V of double V butt welds is filled with weld metal the plates shall be turned over and any slag remaining on the back of the first run removed before a welding is undertaken on the other side. All butt welds shall be reinforced so that the section at the weld is ten (10) per cent greater in thickness than the adjacent metal. Flange butt welds shall be subjected to full X-ray examination where required by the Engineer, and the Contractor shall allow for the cost of such examination on at least 50% of flange butt welds. Such cost or the portion thereof shall be deducted from the monies due to the Contractor if all or some of the tests have not been carried out. - SS 6 - The Engineer shall require examination by X-ray, fluorescent links and penetrant dyes of the weld between flange and web until such times as a uniform and satisfactory procedure is established. The cost of these shall be borne by the Contractor.

21. FILLET WELDS

The throat thickness of fillet shall be not less than seventy percent (70%) of the nominal size of the weld and each surface of contact shall be not less than the nominal size of the weld. Surfaces of fillet welds shall junction as smoothly as practicable with the parent metal and welds showing excessive bulging shall be cut out and re-welded. Where shown on the Drawings or directed by the Engineer, fillet welds shall be ground to a smooth, slightly concave finish. 22.

22.WELDING DETAILS

Particular care shall be taken that in connection the leg of a stiffener to the flange plate, no welding transverse to the tension flange shall take place. In the case of bearing stiffeners over the piers, these shall be carefully fitted to bear against the bottom flange and welded direct thereto.

23. PROTECTION OF STEELWORK AND PAINTING

All steelwork shall be thoroughly cleaned of all loose scale, rust, oil and grease etc. and then be painted with

• one coat alkyd-based anti-corrosion primer

• one coat alkyd enamel undercoat (SS34)

• two coats alkyd enamel gloss topcoat (SS7)

or equivalent prior to delivery to the site. Steelwork shall be mechanically wired brushed. Any coat that has become damaged or defective in any way shall be made good before application of the subsequent coat. Contact surfaces of High Strength Friction Grip (H.S.F.G.) bolted connections shall be unpainted except that the first shop priming coats may extend onto the interface a maximum distance of 13mm. Subsequent coats shall be thoroughly cleaned by hand wire brushing before assembly. Painting shall be carried out by brush or roller generally in accordance with Singapore Standard SS 542. Surfaces to be welded shall not be painted or metal coated within a reasonable distance of any edges to be welded. if the paint or metal coating specified will impair the quality of the weld. Welds and adjacent parent material shall not be painted prior to de-slagging inspection and approval.  Parts to be encased in concrete shall not be painted or oiled. - SS 7 –