Structural Steel.
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, d e i p o c , d e c u d o r p e r e b t o n l l i w y e h t t a h t t n e m e e r g a s s e r p x e s ' r e w o r r o b e h t n o d . e e n s a u o d l e y d l e r n e e t n i m e e r h a t y r o e f h r T e . w E r o R r T o N b E e C h t o G t N r I e R d E n e E l N e I h t G N y E b R n e A i v S g S t E n f e o s y n t r o c e p n e o t r t p i r e w h t a e y r b a t d e a t t i m r m o r f e s i p h t y a n w o n d e e i t v i m g i l s e l i a h t t e n d i t d p n e a c x n e g , i s d e e d s , u g r n o i w d a t e r i d i b e h h x T e
DATE 23-04-07 29-08-07
DETAILS OF REVISION
REV NO
ORIGINAL ISSUE CHANGE IN FORMAT OF TEMPLATE
SPECIFICATION FOR SUPPLY,FABRICATION AND ERECTION OF STRUCTURAL STEEL WORK ESSAR ESS AR ENGINEERING CENTRE , MUMBA I
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, d e i p o c , d e c u d o r p e r e b t o n l l i w y e h t t a h t t n e m e e r g a s s e r p x e s ' r e w o r r o b e h t n o d . e e n s a u o d l e y d l e r n e e t n i m e e r h a t y r o e f h r T e . w E r o R r T o N b E e C h t o G t N r I e R d E n e E l N e I h t G N y E b R n e A i v S g S t E n f e o s y n t r o c e p n e o t r t p i r e w h t a e y r b a t d e a t t i m r m o r f e s i p h t y a n w o n d e e i t v i m g i l s e l i a h t t e n d i t d p n e a c x n e g , i s d e e d s , u g r n o i w d a t e r i d i b e h h x T e
INDEX
CLAUSE
DESCRIPTION
PAGE
1.0
SCOPE
4
2.0
APPLICABLE CODES
4
3.0
GENERAL
5
4.0
MATERIALS
5
5.0
DESIGN OF CONNECTIONS AND PREPARATION OF FABRICATION
7
DRAWINGS 6.0
FABRICATION
9
7.0
ERECTION
11
8.0
INSPECTION
15
9.0
TOLERANCES
16
10.0
STORAGE AND HANDLING
17
SPECIFICATION FOR SUPPLY,FABRICATION AND ERECTION OF STRUCTURAL STEEL WORK ESSAR ESS AR ENGINEERING CENTRE , MUMBA I
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, d e i p o c , d e c u d o r p e r e b t o n l l i w y e h t t a h t t n e m e e r g a s s e r p x e s ' r e w o r r o b e h t n o d . e e n s a u o d l e y d l e r n e e t n i m e e r h a t y r o e f h r T e . w E r o R r T o N b E e C h t o G t N r I e R d E n e E l N e I h t G N y E b R n e A i v S g S t E n f e o s y n t r o c e p n e o t r t p i r e w h t a e y r b a t d e a t t i m r m o r f e s i p h t y a n w o n d e e i t v i m g i l s e l i a h t t e n d i t d p n e a c x n e g , i s d e e d s , u g r n o i w d a t e r i d i b e h h x T e
1.0
SCOPE This Specification defines the basic requirements for the supply, fabrication and erection of structural
steel work, design of connections and preparation of fabrication drawings for buildings, plant and equipment supports, stairways, access platforms, steel flooring, ladders, painting and fire proofing. -Engineer’s representative means EEC’S representative -Contractor’s representative means ECL’s representative
2.0
APPLICABLE CODES The following Indian Standards including all amendments and revisions shall be considered as part of
this Specification. Alternative equivalent National Specifications to suit the Country of Origin of the Material, or the country in which the works are constructed may be used but only with the written approval of the Engineer. IS: 800
Code of Practice for General Construction in Steel
IS: 802 Part 2
Code of Practice for use of Structural Steel in Overhead Transmission Line Towers Fabrication, Galvanizing, Inspection and Packing.
IS: 806
Code of Practice for use of Steel Tubes in General Building Construction
IS: 808
Dimensions for Hot Rolled Steel Beam, Column, Channel and Angle Sections
IS: 814
Covered Electrodes for Manual Metal Arc Welding of Carbon and carbon Manganese Steel – Specification
IS: 816
Code of Practice for use of Metal Arc Welding for General Construction in Mild Steel
IS: 817
Code of practice for Training & Testing of Metal Arc Welder
IS: 822
Code of practice for Inspection of Weld
IS: 919(Part 1)
Recommendations for Limit and Fits for Engineering.
IS: 1024
Code of Practice for use of Weldings for Bridges & Structures subjected to Dynamic Loading
IS: 1161
Specification for Steel Tubes for Structural Purposes.
IS: 1182
Recommended practice for radiographic examination of fusion welded butt joints in steel plates
IS: 1363 (Part 1 & 3)
Hexagon Head Bolts, Screws and Nuts of Product Grade C- Hexagon Head Bolts (M5 M64)
IS: 1367 Part 1, 2, 3, 5 Technical Supply Conditions for Threaded Steel Fasteners 6 and 7 IS: 1395
Specification for Low & Medium Alloy Steel Covered Electrodes for manual metal arc welding
IS: 1977
Specification for Structural Steel (Ordinary Quality)
IS: 1852
Rolling and Cutting Tolerances for Hot Rolled Steel Products
IS: 2062
Steel for General Structural Purposes - Specification
IS: 2074
Ready Mixed Paints, Red Oxide, Zinc Chromate Priming
IS: 3502
Specification for Steel Chequered Plates
IS: 3658
Code of Practice for Liquid Penetrant Flaw Detection
SPECIFICATION FOR SUPPLY,FABRICATION AND ERECTION OF STRUCTURAL STEEL WORK ESSAR ESS AR ENGINEERING CENTRE , MUMBA I
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IS: 3757
Specification for High Strength Structural Bolts
IS: 4000
High Strength Bolts in Steel Structure Code of Practice
IS: 4260
Recommended Practice for Ultrasonic Testing of Butt Welds in Ferritic Steel
IS: 5334
Code of Practice for Magnetic Flaw Detection of Welds.
IS: 5369
General Requirements for Plain Washers and Lock Washers.
IS: 5372
Specification for Taper Washers for Channels (MC).
IS: 5374
Specification for Taper Washers for I Beams (ISMB)
IS: 6610
Heavy Washers for Steel Structure.
IS: 6639
Specification for Hexagon Bolts for Steel Structures.
IS: 7205
Safety Code for Erection of Structural Steel Work
IS: 7215
Tolerances for Fabrication of Steel Structures
IS: 7307 Part 1
Approval tests for Welding Procedures Part 1 - Fusion welding of steel.
IS: 7310 Part 1
Approval tests for Welders working to approved welding procedures Part: 1 - Fusion welding of steel
IS: 7318 Part 1
Approval tests for Welders when welding procedure approval is not required. Part 1 Fusion Welding of Steel
IS 8500
Structural Steel-Micro Alloyed (Medium & High Strength Qualities)
IS 9595
Recommendation for Metal Arc Welding of Carbon and Carbon Manganese Steels.
IS 12843
Tolerances for Erection of Steel Structures
3.0
GENERAL
3.1
RELATED DOCUMENTS In the event of conflict, between this specification and related specifications, standards and documents
the most stringent condition/requirement shall apply.
3.2
UNITS
3.2.1
Design calculations shall be carried out using the SI system of units.
3.2.2
On shop shop fabrication drawings, levels shall be quoted in in metres and dimensions in millimeters.
4.0
MATERIALS
4.1
GENERAL All materials used in the Works shall be new, first quality steel, free from laminations, seams, blisters
and other harmful defects and shall comply with the appropriate Indian Standards. Substitution of material shall not be allowed without written approval of the engineer. Test certificates in accordance with the requirements of the relevant Indian Standards, shall be supplied to the Engineer in respect of all materials to be used in the Works, prior to commencement of fabrication.
4.2
STRUCTURAL STEEL
SPECIFICATION FOR SUPPLY,FABRICATION AND ERECTION OF STRUCTURAL STEEL WORK ESSAR ESS AR ENGINEERING CENTRE , MUMBA I
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Unless specified otherwise, all structural steel plates (including open grating & chequered plates),shapes, bars & hollow sections shall be weldable steel, Standard Quality”(Fe 410 W A ) confirm to IS 2062.Hot rolled sections shall be Indian Standard Sections in accordance with IS 808.The thickness tolerances for plates and flats shall be as specified in IS 1852. The deviation over or under the nominal thickness shall be equal to half the total thickness tolerance. Steel shall be marked in accordance with IS 2062. Members in steel grades other than Grade A shall have additional marks of a form and in positions to be agreed with the Engineer. Steel tubes for structural purposes shall be in accordance with IS: 1161, Yst 240 Steel material shall be supplied with Charpy V Notch test requirement when: 1) The steel design temperature is very low (0ºC or lower) 2) Thickness is large (50 mm or greater) and subjected to tensile stresses. The Charpy V Notch test is specified to ensure adequate notch toughness so as to avoid brittle failure. In such cases, it is recommended to use Fe410W B or C as required. Plates greater than 40 mm in thickness could have internal discontinuities/laminations and hence shall be ultrasonically tested to ensure that their structural integrity and internal soundness meet prescribed quality levels. Ultrasonic Testing of plates shall be carried out in accordance with BS EN 10160 Class So. Since ultrasonic testing is a supplementary (not mandatory on the supplier) requirement, it is preferable to specify the test at the time ordering/procuring the steel.
4.3
BOLTS, NUTS AND WASHERS Bolts and nuts shall comply with IS 1363, IS 1367, IS 3757 and IS 6639 as appropriate with isometric
coarse pitch threads. Nuts shall be of at least the strength grade appropriate to the grade of bolts or other threaded elements with which they are used. Plain washers for use with ordinary bolts and nuts shall comply with IS 5369.Tapered washers shall comply with IS 5372 or IS 5374 as applicable. One assembly shall consist of one hexagon structural bolt and one washer to be used under the nut, where the surface of bolted parts, which are in contact with the bolt head or nut have a slope more than 1:20 with respect to plane normal to the bolt axis (e.g. Channels, I-sections) a smooth taper washer shall be used under the nut.
4.4
WELDING CONSUMABLES Welding consumables, used for metal arc welding of steels complying with IS: 2062, shall comply with
IS: 814. Welding consumables and procedures shall be such that the mechanical properties of deposited weld metal are not less than the respective minimum values for the parent metal being welded.
4.5
STEEL GRATING AND STAIR TREADS Steel grating and stair treads shall be open grid rectangular pattern complying with Standard drawings 2
and shall be galvanized all as per IS 4759.Minimum water weight shall be 610 g/m
4.6
CHEQUERED PLATES Steel chequered plates shall conform to IS 3502.
SPECIFICATION FOR SUPPLY,FABRICATION AND ERECTION OF STRUCTURAL STEEL WORK ESSAR ESS AR ENGINEERING CENTRE , MUMBA I
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5.0
DESIGN OF CONNECTIONS AND PREPARATION OF FABRICATION DRAWINGS
5.1
GENERAL Fabrication shall be in accordance with IS: 1161 and IS: 2062. The size of members indicated on
engineering drawings shall be strictly followed. However, in case of lack of specified material, Engineer’s approval in writing is required before substitution. All welding shall be in accordance with the requirements of IS :816, IS: 1024 and IS: 9595 and welders shall be qualified according IS: 7318.Edge preparation (beveling) for "V", "X", "K" or "U" welds, shall be conform to IS: 9595.Punching of holes in structural members transmitting forces is not allowed. Contractor’s approval, in writing, is required for punching holes in other members than mentioned above.
5.2
WORKMANSHIP The workmanship and finish shall be equal to the best in modern shop practice and shall be in
accordance with regulatory requirements. Only new material shall be used, which shall be thoroughly straightened in the shop by methods that will not cause damage before it is laid off or worked in any way. All cutting and shearing shall be neatly done and all surfaces/edges exposed to view shall have a neat and workmanlike finish. Sharp edges shall be removed and rounded off with a minimum radius of 1 mm minimum. Structural-steel elements shall be fabricated in accordance with tolerances of IS: 7215.Horizontal beams placed in such a way that they form rain pockets shall be provided with drain holes of 30 mm diameter, center to center 1000 mm, with a minimum of two (2) holes. It shall be subcontractor's responsibility to ensure that any excessive warp or distortion of structural steel shall be corrected by means of straightening prior to shipment. Stairways, ladders and hand railing shall be in accordance with the standard drawings. For standard drawings, see appendix II of specification 08000-J-601.
5.3
INSPECTION AND TESTING All structural-steel materials and fabrication shall be subject to inspection by contractor. Contractor’s
inspector shall have free access to the materials and to all parts of the steel structure which is being fabricated. Material which is found to be defective or contrary to this specification and requirements of the purchase order shall be rejected. At least a three-day notice will be given when the material is ready for inspection. Where preerection is specified, the members of the structure or parts thereof shall be laid out on the shop floor for inspection. Welds shall be inspected by the subcontractor according to the provisions of regulatory requirements IS: 822, with respect to technique, equipment, acceptance criteria and personnel qualifications. All welds shall be subject to random visual inspection .In addition, the following special requirements shall apply to welding inspection. All critical butt welds (full penetration) shall have a full visual inspection and shall also be inspected by either radiographic or ultrasonic methods as follows:
Radiographic:
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Make one (1) spot radiograph per 500 mm of butt weld. Take the radiographs on the flange sections of the beam with a minimum of one (1) radiograph per welded connection, in accordance with regulatory requirements. Ultrasonic: Entire length of butt weld, including the webs, shall be tested. The ultrasonic examination shall be done in accordance with regulatory requirements. All full penetration corner and T-joint welds, used in beam column connections shall have full visual inspection and shall also be inspected by ultrasonic methods in accordance with the thickness schedule below: All fillets welds 25 mm or over in size shall be inspected by magnetic particle testing or liquid penetrant inspection for 10% of their length. Thickness of Thinnest Section Being Welded Less than 25 mm 25 mm to 50 mm Over 50 m Surface Protection Structural Steel All steelwork shall be adequately prepared and protected. Surface preparation and surface protection (painting), shall be in accordance with EECS-62-100-005, "Surface Preparation and Painting”. If a coating is damaged, repair shall be done in accordance with EECS-62-100-005,"Surface Preparation and Painting".
5.4
Documents to be submitted by Contractor General arrangement and detail drawings and their associated calculations shall be submitted to the
Engineer for review in accordance with the requirements of the Works Specification. 5.5.2 Shop fabrication drawings and their associated calculations shall be fully checked and approved by the Contractor. They shall be submitted to the Engineer for review, when required, not less than three weeks prior to fabrication of the item to which they relate. Details of welding procedures shall be fully checked and approved by the Contractor. They ` shall be submitted to the Engineer for review when required, not less than three weeks prior to fabrication of the item to which they relate. Welder qualification test certificates in accordance with the requirements of the relevant Indian Standards shall be submitted at the same time for all personnel who will be engaged on the work. A list of all drawings, calculations and other documents shall be submitted for each structure with the first batch of drawings relating to that structure. If in the opinion of the Engineer any design, drawing, welding procedure or welder test certificate is unsatisfactory in any way whatsoever, the Contractor shall make such amendments as required by the Engineer. Supply or fabrication of any item shall not commence until all calculations and drawings relating to the item have been reviewed and either accepted or accepted with comments. No variations from the reviewed drawings shall be carried out without the prior written approval of the Engineer. Notwithstanding any absence of comment by the Engineer, the Contractor shall remain fully responsible for the adequacy, safety, strength, serviceability, durability and accuracy of the work.
SPECIFICATION FOR SUPPLY,FABRICATION AND ERECTION OF STRUCTURAL STEEL WORK ESSAR ESS AR ENGINEERING CENTRE , MUMBA I
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6.0
FABRICATION
6.1
GENERAL Fabrication shall be carried out in accordance with the requirements of IS 800. Fabricated structural
steel work shall be within the tolerances specified in IS 7215. The size of members indicated on Engineering Drawings shall be strictly followed. In case of lack of specification member/material, prior approval of engineer in writing shall be required before substitution. Punching of holes in structural members transmitting forces shall not be altered without written approval of engineer.
6.2
IDENTIFICATION At all stages of fabrication, structural steel members shall be positively identified by a suitable marking
scheme. All structural-steel members, grating, hand railing, stairways, stringers, stair treads, etc., shall be marked with identification marks and such other marks as may be required to facilitate erection in accordance with the marking diagram to be supplied by contractor. Marking paint must be compatible with primer or finish coat. Erection marks shall be clearly painted with a white weather-resistant paint on all structural members and loose parts (except grating) in symbols at least 50 mm high. In addition, they shall be stamped on all structural members, in symbols at least 12 mm high and 1 mm deep. Painted marking shall not be supplied until the final shop coat is thoroughly dry. Marks will have references to the relevant mark and erection drawings and to the relevant bolt-nut-washer shim lists. Marking will be done on the same location of the mark corresponding with the mark and erection drawing(s). All members to be marked "TOP" where possibility of erecting the member inverted exists. All columns to have the mark "painted" on the outside face of the flange and marked "North" or "East". Column marks shall carry a tier suffix for spliced columns. Grating shall be tagged with a metal plate having raised letters so that the mark shall be visible after painting. This metal plate shall be tack welded to grating prior to painting.
6.3
STRAIGHTENING All materials shall be straight, and if necessary, before being worked, shall be straightened and/or
flattened (unless required to be of curvilinear form) and shall be free from twists.
6.4
CLEARANCES The erection clearance for ends of members with web cleats or end plates shall be not greater than 2
mm at each end. The erection clearance at ends of beams without web cleats and end plates shall be not more than 3 mm at each end but where for practical reasons, greater clearance is necessary, suitably designed seatings approved by the Engineer shall be provided.
6.5
CUTTING Prior to cutting, all members shall be properly marked showing the requisite cut length/width,
connection provisions e.g. location and dimensions of holes, welds, cleats, etc. Marking for cutting shall be done judiciously so as to avoid wastages or joints as far as possible. Cutting shall be by sawing, shearing, SPECIFICATION FOR SUPPLY,FABRICATION AND ERECTION OF STRUCTURAL STEEL WORK ESSAR ESS AR ENGINEERING CENTRE , MUMBA I
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cropping or machine or hand flame cutting. Hand flame cutting shall be used only where it is impractical to use machine flame cutting and for notching, or for the completion of the formation of slotted holes. Electric metal arc cutting shall not be permitted. Cut edges shall be true to profile and be free from major notches and sharp edges and shall be dressed immediately by grinding. Where members are notched to fit other members, the notches shall be as small as practicable and rounded off at re-entrant corners with a minimum radius of 6 mm.
6.6
HOLING All holes for fasteners or pins shall be drilled except as permitted otherwise herein. All matching holes
for fasteners or pins shall register with each other so that fasteners can be inserted freely through the assembled members in a direction at right angles to the faces in contact. Holes for ordinary bolts of property class below 8.8 in light roof members or other light framing and in connecting angles and plates other than splices may be punched full size through material not thicker than the diameter of the hole, provided that the punching does not unduly distort the material. Slotted holes shall either be punched in one operation or formed by drilling two holes and completed by cutting, grinding or filing the surface smooth. Burrs shall be removed from holes before assembly except that where holes are drilled in one operation through parts clamped together which would not otherwise be separated after drilling; they need not be separated to remove the burrs. For bolts not exceeding 24 mm diameter, holes shall be not more than 1.5 mm greater in diameter than the bolt and for bolts over 24 mm diameter, holes shall be not more than 2 mm greater in diameter than the bolts, except in steel base plates and where otherwise specified on the Drawings.
6.7
JOINTS IN COMPRESSION Abutting surfaces dependent on contact for the transmission of load shall be within the tolerances
specified in Clause 9.
6.8
SPLICING Splicing of built up/compound/latticed sections shall be done in such a fashion that each component of
the section is jointed in staggered manner. Where no butt weld is used for splicing, the meeting ends of two pieces of joint/channel/built up section shall be ground flush for bearing on each other and suitable flange and web splice plates shall be designed and provided for the full strength of the flange/web of the section and bolts/welds designed accordingly. Where full strength butt weld is used for splicing (after proper edge preparation of the web and flange plates) of members fabricated out of joist/channel/built up section, additional flange and web plates shall be provided over and above the full strength butt welds, to have 40% strength of the flange and web. Where a cover plate is used over a joist/channel/section the splicing of the cover plate and channel/joist/section shall be staggered by minimum 500 mm. Extra splice plate shall be used for the cover plate and joist/channel/section as per Clause 6.8.2 or 6.8.3.
7.0
ERECTION SPECIFICATION FOR SUPPLY,FABRICATION AND ERECTION OF STRUCTURAL STEEL WORK ESSAR ESS AR ENGINEERING CENTRE , MUMBA I
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7.1
ASSEMBLY Erection shall be carried out in accordance with the requirements of IS 800. Prior to erection, the
Contractor shall carry out an inspection of the location and level of the prepared foundations and anchor bolts, and advise the Engineer of his findings. Corrective action required shall have the approval of engineer. 7.2.3 All components shall be erected within the tolerances specified in Clause 9 and in such a manner so that they are not bent, twisted or otherwise damaged and the specified cambers are provided when required.Drifting. to align holes shall not enlarge the holes or distort the metal. Holes which cannot be aligned without distortion shall be a cause for rejection unless enlargement by reaming is specifically approved by the Engineer. Holes shall not be made by gas cutting. Throughout the erection of the structure, the steel work shall be securely bolted or fastened in order to ensure that it can adequately withstand all loadings liable to be encountered during erection, including where necessary, those from erection plant and its operation. Any temporary bracing or temporary restraint shall be left in position until such time as erection is sufficiently advanced so as to allow its safe removal. Contractor should apprise himself of the daily conditions so as to be fore warned in case of expected high velocity winds. All connections for temporary bracings, members, etc. to be provided for erection purposes shall be so made that they do not weaken the permanent structure or impair serviceability during their removal. On removal of such temporary members, the surface of permanent steel work shall be ground flush and re-painted if necessary. No permanent bolting or welding shall take place until the steelwork has been properly aligned and the erection has been approved by the Engineer.
7.2
WELDING
7.2.1
GENERAL Welding of structural steel shall be in accordance with IS 9595 and IS 816. For welded parts, all mating
surfaces shall be sealed by welding against the ingress of moisture. Welding shall be carried out by suitably qualified welders who have satisfactorily completed the appropriate tests laid down in IS 7318. All welding shall be carried out under the direction of a competent Welding Technologist. The minimum size of shop fillet weld shall be 6 mm and of field fillet weld shall be 8 mm. The Contractor shall make necessary arrangement for providing sufficient number of welding sets of the required capacity, all consumables, cutting and grinding equipment with requisite accessories/auxiliaries, equipment and materials required for carrying out various tests such as dye penetration, magnetic particle, ultrasonic and the like. Adequate protection against rain and strong winds shall be provided to the welding personnel and the structural members during welding operation. Welding shall not be carried out in the absence of such protection. It shall be the responsibility of the Contractor to ensure that all welding is carried out in accordance with this specification and relevant IS Codes. The Contractor shall provide all the supervision to fulfill this requirement.
7.2.2
PREPARATION OF MEMBER FOR WELDING.
7.2.2.1 EDGE PREPARATION Edge preparation/leveling of the fusion faces for welding shall be done strictly in accordance with the dimensions shown in the drawings. In case, the same are not indicated, edges shall be prepared (depending on SPECIFICATION FOR SUPPLY,FABRICATION AND ERECTION OF STRUCTURAL STEEL WORK ESSAR ESS AR ENGINEERING CENTRE , MUMBA I
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the type of weld indicated in the drawing) in accordance with the details given in IS 9595. Leveling of fusion faces shall be approved by the Engineer. The tolerance on limits of gap, root face and included angle shall be as stipulated in IS 9595.
7.2.2.2 CLEANING Welding edges and the adjacent areas of the members (extending upto 20 mm) shall be thoroughly cleaned of all oil, grease, scale and rust and made completely dry. Gaps between the members to be welded shall be kept free from all foreign matter.
7.2.2.3 PREHEATING Preheating of members shall be carried out as per IS 9595 when the base metal temperature is below the requisite temperature for the welding process being used. Preheating shall be done in such a manner that the parts, on which the weld metal is being deposited, are above the specified minimum temperature for a distance of not less than 75 mm on each side of the weld line. The temperature shall be measured on the face opposite to that being heated. However, when there is access to only one face, the heat source shall be removed to allow the temperature equalization (1 minute for each 25 mm of plate thickness) before measuring the temperature.
7.2.2.4 GRINDING Column splices and butt joints of struts and compression members (depending on contact for load transmission) shall be accurately ground and close-butt end over the whole section with a tolerance not exceeding 0.2 mm locally at anyplace. In column caps and bases, the ends of shafts together with the attached gussets, angles, channels etc. shall be accurately ground so that the parts connected butt over minimum 90% surface of contact. In case of connecting angles or channels, care shall be taken so that these are fixed with such accuracy that they are not reduced in thickness by grinding by more than 2 mm. Ends of all bearing stiffeners shall be ground to fit tightly at both top and bottom. Similarly the bottom of knife edge supports along with the top surface of column brackets shall be accurately ground to provide effective bearing with a tolerance not exceeding 0.2 mm locally at any place. Slab bases and caps shall be accurately ground over the bearing surfaces and shall have effective contact with the ends of stanchions. Bearing faces which are to be grouted need not be ground if such faces are true and parallel to the upper faces.
7.2.3
WELDING PROCESSES Welding of various materials under this specification shall be carried out using one or more of the
following processes. - Manual Metal Arc Welding Process (MMAW) - Submerged Arc Welding Process (SAW) - Gas Metal Arc Welding Process (GMAW) - Flux Cored Arc Welding Process (FCAW) The welding procedure adopted and consumables used shall be specifically approved by the Engineer.
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7.2.4
APPROVAL AND TESTING OF WELDERS The Contractor shall satisfy the Engineer that the welders are qualified. For this purpose the welders
shall have satisfied the relevant requirements of IS 7318. If the welders will be working to approved welding procedures, they shall have satisfied the relevant requirements of IS 7310.Adequate means of identification shall be provided to enable each weld to be traced to the welder by whom it was made. The Contractor shall intimate the Engineer sufficiently in advance, the commencement of tests, to enable him to witness the same.
7.2.5 .
APPROVAL AND TESTING OF WELDING PROCEDURES The Contractor shall carry out procedure tests in accordance with IS 7307 to demonstrate by means of
a specimen weld of adequate length on steel representative of that to be used, that he can make welds with the welding procedure to be used for the work to the complete satisfaction of the Engineer. The test weld shall include weld details from the actual construction and it shall be welded in a manner simulating the most unfavorable instances of fit-up, electrode condition etc. which are anticipated to occur on the particular fabrication. Where material analyses are available, the welding procedure shall be carried out on material with the highest carbon equivalent values. Before the relevant tests given in IS 7307 are carried out, the test weld shall be held as long as possible at room temperature, but in any case not less than 72 hours and shall then be examined for cracking. The examination procedure shall be sufficiently rigorous to be capable of revealing significant defects in both parent metal and weld metal. The Contractor shall submit the welding procedure in standard format given in IS 9595. The Contractor shall obtain the Contractor’s approval of the same prior to starting the fabrication.
7.2.6
SEQUENCE OF WELDING As far as practicable, all welds shall be made in a sequence that will balance the applied heat of
welding while the welding progresses. The direction of the general progression in welding of a member shall be from points where the parts are relatively fixed in position with respect to each other towards points where they have a greater relative freedom of movement. All splices in each component part of a cover plated beam or plated beam or built up member shall be made before the component part is welded to other component parts of the member. Joints expected to have significant shrinkage shall be welded before joints expected to have lesser shrinkage. Welding shall be carried continuously to completion with correct number of runs. The Contractor shall choose the welding sequence after carefully studying each case such as to minimize distortion and shrinkage. The Contractor shall submit the same to the Engineer for comments and approval prior to welding.
7.2.7
WELDING TECHNIQUE After the fusion faces are carefully aligned and set with proper gaps, the root pass of butt joints shall be
executed properly so as to achieve full penetration with complete fusion of the root edges. On completion of each run, all slag and spatter shall be removed. The weld and the adjacent base metal shall be cleaned by wire brushing and light chipping. Visible defects such as cracks, cavities and other deposition faults, if any, shall be
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removed to sound metal before depositing subsequent run of weld. All full penetration butt welds shall be completed by chipping/gouging to sound metal and then depositing a sealing run of weld metal on the back of the joints. Where butt weld is practicable from one side only, suitable backing steel strip shall be use and joint shall be arranged in such a way as to ensure that complete fusion of all the parts is readily obtained. While welding is in progress, care shall be taken to avoid shocks, vibrations or any kind of movement of the components, in order to prevent occurrence of weld cracks. Any deviation desired from fr om the recommended welding technique and electrodes shall be adopted only after obtaining written approval of the Engineer.
7.3
BOLTING Bolts of property class 4.6 shall generally be used for all connections including bracing and column
splices. However, for connections resisting large moments and forces, bolts of property class 8.8 shall be used with the prior approval of the Engineer. Where necessary the connected parts shall be firmly drawn together. Steel packing plates shall be provided where necessary to ensure that the total remaining gap between adjacent surfaces does not exceed 2 mm. The length of bolt shall 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. The threaded length shall be clear of the joint mating surfaces. Washers shall be provided under the element (nut or bolt head) turned during tightening. Nuts used on connections subject to vibration shall be secured to prevent loosening. Self-locking nuts shall be used or else the nuts shall be secured by the use of locknuts or upsetting of the threads of the bolts after assembly and tightening. Bolts, nuts and washers used to connect metal-sprayed or galvanized steel work shall be spun galvanized. Where slotted holes are provided for movement connections, the joint shall be free to move. Areas of steel which will form the mating faces of a high strength friction grip joint or are to be concrete cased shall be unpainted and maintained in a clean condition and free from loose rust, oil, loose scale and other deleterious matter. High tensile bolts to IS 1367 property class 8.8 shall be tightened in accordance with the manufacturer’s recommendations using a torque wrench which shall be calibrated at least once each working day.
7.4
PROTECTIVE TREATMENT Steel shall be pre-treated and painted or galvanized in accordance with the relevant Specification. The
protective treatment shall be carried out after fabrication is complete. No welding, holing or other work which may damage the protective treatment shall be carried out following painting.
7.5
EQUIPMENT All equipment used in erection shall be provided by the Contractor, and shall be suitable for its purpose
and of adequate capacity. Equipment to be used shall include staging, ladders, and plant including temporary structures necessary to complete the erection .
7.6
ALIGNMENT Each part of the structure shall be aligned as soon as practicable after it has been erected. Packs,
shims and other supporting devices shall be flat, of adequate strength and rigidity and not larger than
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necessary. Where packing shall be left in position and subsequently grouted, they shall be placed such that they are totally enclosed by the grout.
7.7
CLEARING AWAY The Contractor shall periodically clean up as required by the Engineer to maintain a safe working
environment and on completion of the work remove all rubbish, plant and surplus materials from the site of work and storage areas, to the satisfaction of the Engineer.
7.8
SAFETY AND SECURITY DURING ERECTION The Contractor shall comply with IS 7205 for necessary safety, adhere to safe erection practice and
guard against hazardous as well as unsafe working conditions during all stages of erection. During erection, the steel work shall be securely bolted or otherwise fastened and when necessary, temporarily braced/guyed to provide for all loads including those due to wind, erection equipment and its operation to be carried by the structure till the completion of erection. (No permanent bolting or welding shall be done until proper alignment has been achieved) Access to structure under erection shall be permitted only to person involved to avoid accidents. Proper accesses, platforms and safety arrangements shall be provided for working and inspection whenever required. If required temporary planking and handrails shall be executed to avoid accidents.
8.0
INSPECTION
8.1
GENERAL All structural steel materials & fabrication shall be subject to inspection by the engineer. The Engineers
representative shall have free access to the materials and to all parts of the steel structure which is being fabricated. Prior to inspection, all slag, loose scale, dirt, grit, weld spatter, paint, oil or other foreign matter shall be removed from the steel work. Welded connections shall not be painted prior to inspection.
8.2
TESTS ON WELDING The Contractor shall carry out the following non-destructive testing of welds at his own cost in the
presence of the Engineer’s Inspector:
8.2.1. BUTT WELDS Radiographic tests shall be carried out in accordance with IS 1182 or as appropriate, or ultrasonic tests in accordance with IS 4260 on a random 10% of the welds. Welds shall be accepted as satisfactory if the defects are within the limits stated in IS 7310.
8.2.2
FILLET WELDS Dye penetrate tests shall be carried out in accordance with IS 3658 or magnetic particle tests in
accordance with IS 5334 on a random 5% of the welds. Welds shall be accepted as satisfactory if the defects are within the limits stated in IS 7310. If the results of the weld tests are unsatisfactory, the defective welds shall SPECIFICATION FOR SUPPLY,FABRICATION AND ERECTION OF STRUCTURAL STEEL WORK ESSAR ESS AR ENGINEERING CENTRE , MUMBA I
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be repaired by methods approved by the Engineer. All repaired welds shall be re-tested. For each weld which is judged to be unsatisfactory a further test shall be carried out on a different randomly selected weld. In addition to the tests specified above the Contractor shall carry out such further tests as may be required by the Engineer. The Contractor will not be required to bear the costs of these further tests unless they reveal defective welds. Written welding procedures shall be prepared and tested in accordance with IS 7307(Part 1).The procedure shall identify material, weld geometry, tolerance, welding process, preheat temperatures and welding position to be used. Welders shall be tested to meet the requirement of IS 7310 (Part 1) and certificate shall be updated every six months, after due verification. Visual inspection shall be made in accordance with IS 822, over full length of weld NDT shall be carried out by qualified personnel. Magnetic particle inspection (MPI) shall be in accordance with is 5334 and Dye penetrant inspection shall be in accordance with IS 3658.Ultrasonic testing shall be in accordance with IS 4260. All welds shall be visually inspected along 100% of their length. NDT of welds for general steel structure is not required. In case of critical structure the following basic NDT requirements shall be considered in addition to a. Fillet welds with throat thickness >25mm shall be MPI tested. b. Fillet welds where connecting material is >20mm shall be MPI tested. c. Butt welds where connecting material is < 20mm shall be MPI tested. d. Butt welds where the connecting material is 20mm or greater, shall be electronically tested.
90
TOLERANCES
9.1
GENERAL Structural steel work shall be fabricated, and erected within the tolerances specified in IS 7215 and IS
12843 with the exception of those items specified below.
9.2
ERECTION TOLERANCES The position on plan of a steel column at the base shall not deviate from the specified position by more
than +5 mm along either of the principal setting out axes. The level of the underside of a steel base plate shall not deviate from the specified level by more than ± 5 mm. The deviation of the top of a single storey column from its specified position relative to the base shall not exceed the greater of ±5 mm or ±1/1000 of the height from base to cap in any direction, except in the case of deviation of the tops of the columns of a portal frame measured in the plane of the frame. The deviations of multi-storey columns at any level shall not exceed the greater of ±5 mm or ±1/1000 of the storey height over the actual positions of the columns at the level immediately below. The deviations of the columns at the topmost storey relative to required positions of the columns at the foundations shall not exceed the least of ±5mm per storey, ±1/1000 of the height from foundation to top or storey height of the column or ±25mm for columns upto 30m height. For columns over 30m height, these limits shall be ±1/1200 and ±35mm respectively. Members other than columns shall not deviate from their specified position, relative to the columns to which they are connected, by more than ±5 mm. The level of the top of the steel work at any storey shall be within ±5mm of the specified level and shall not vary by more than ±5mm within any distance of 5m measured at that level. The difference in level between the top of beams which are connected or frame into the same column shall not exceed 2mm. The lateral shift of the
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centre of the top chord shall be not exceed the lesser of ±1/250 of the truss height at centre or ±15mm with respect to the vertical plane passing through the centre of the bottom chord. The lateral shift of the centre of the top chord shall not exceed the lesser of ±1/1500 of the span of the truss in mm or ±10mm with respect to the vertical plane passing through the centre of the truss supports. The shift in the centerline of crane rail with respect to the centerline of the girder shall not exceed ±(1/2 of the web thickness in mm plus 2mm). The shift in plan of alignment of crane rail with respect to true axis of crane rail at any point shall not exceed ±5mm.
10.0
STORAGE AND HANDLING
10.1
Fabricated parts shall be handled and stacked in such a way that permanent damage is not caused to
the components. Means shall be provided to avoid damage to the protective treatment on the steel work. 10.2
All work shall be protected from damage in transit. Particular care shall be taken to stiffen free ends,
prevent permanent distortion and protect all machined surfaces adequately.
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