This procedure describes the minimum requirements that shall be observed at site for handling and storing materials, erection of hot dip galvanized primary and secondary steel structure to be installed.
It also covers the tests and inspections that are to be carried out during the execution of the fabrication, erection and assembly works.
This procedure cover’s Steel Structures, Steel from Building, Supporting Steel, Steel Pipe Rack, and Miscellaneous Structure Steel.
The objective is to ensure that all the activities are carried out:
- In accordance with approved procedures, specifications and drawings,
- Using special working and control process which have been previously qualified;
- employing qualified and, when required, certified personnel;
- using material which are kept under control from receiving throughout entire working cycle;
- Performing all tests, measurements and inspection required by contract.
Applicable Codes and Standards
AISC (9 th edition): The American Institute of Steel Construction
AWS D1.1: Structural Steel Welding Code
(BS) British Standards
(ISO) International Standard Organization
ANSI American National Standard Institute
ASTM American Society for Testing and Materials
Minimum Quality Requirements for Site Activity
Steel Structural Works Technical Specification
Steel Structure Standard Drawings and Details
Project Quality Plan
Roles and Responsibilities
Construction Manager is responsible for the implementation of this procedure for the over all direction and coordination with the site team and QA/QC engineer for monitoring, coordinating and control of all the erection activities.
QA/QC team is responsible to verify the proper implementation of the quality systems and to implement quality control activities related to fabrication and erection of steel structures.
Materials and Equipment’s
The Steel Structures shall mainly consist of the following:
- Steel Building and Shelter
- Pipe Racks / Steel Structure
- Equipment Platform, Stair and Walkways / Handrails/Cross over /Shatters
- Minor Steel Structure / Supports / Ladders / Grouting /Beams etc.
WELDING FILLER METAL
When required for any modification Welding filler metal shall conform now to BS 5135, BS 639 and ISO 5182 /E7018 welders and welding WPS as per BS4871 & BS 4872
EQUIPMENT AND TOOLS
All tools and equipment’s to be used for erection shall be standard (not allow any fabricated or hand made fouls) in good order, safe condition and sufficient quantity.
Examples of tools and equipment are:
- Cranes
- Lifting gear including sling wires, belts, shackle
- Plastic Ropes to be used as guide only during lifting not for any lift
- Standard tools such as spanners, Torque Wrenches etc.
- Transportation Trucks
PLANNING OF ACTIVITIES AND MONITORING OF PROGRESS
Project Planner is responsible to plan the sequence of erection of steel structure according to the “Construction Master Schedule”, he is also responsible to monitor the progress of the work and to keep informed the Construction Manager and Project Manager for any deviation from the original schedule.
Planning of steel structure erection shall be made according to erection’s priority and material availability.
ERECTION DRAWINGS
Technical Office (TO) shall receive the steel structure drawings from engineering department.
Based on the availability of drawings, material after fabrication, specifications and in congruence with planning, TO shall issue detailed drawings for erection and copy to all the concerned departments.
The following information shall be provided in the detailed drawings:
- Identification of each item, part or assembly number with match mark and other information as necessary for easy identification and erection;
- Specific instruction, as necessary for erection;
MATERIAL RECEIVING, HANDLING AND STORAGE
Material Control Manager (MCM) shall receive all steel structure components in accordance with the applicable procedure and shall be responsible for checking quantity and type of materials indicated in the packing list. QC inspector shall check as per the quality requirements and checklists etc.
The damages shall be immediately notified to take the required measures.
All the materials shall be stored, handled and preserved in accordance with the procedure.
CHECK FOR FOUNDATIONS
Before commencing work, center lines, locations, orientation, chipping and elevations of foundations shall be checked for prescribed tolerances.
Support shims shall be located after marking the centre lines on the plinths.
At least 3/4 shims packs with levelling mortar shall be provided for the base plates of each column.
Centre lines marked on plinths shall have a tolerance of ± 1 mm and elevation of ± 1 mm.
The foundation bolt surface that will come in contact with concrete shall be free from dirty and oily matters or points. Foundation surface shall be chipped prior to erection activity.
PRELIMINARY CHECKS
According to the sequence and schedule of erection, the following preliminary checks shall be carried out before erection activities begin, in order to verify:
The availability of experienced, qualified personnel and equipment necessary to carry out the works;
Availability of fabricated steel structure and its status of acceptance.
The status and availability of approved for Construction drawings and /or specifications.
All tools and equipment’s used for erection are calibrated as per Calibration of Inspection and Testing Equipment procedure.
The status of torque wrench calibration the above preliminary checks shall be jointly made by all the concerned as in responsibility matrix.
MATERIAL WITHDRAWAL
According to the erection sequence, priority and on basis of the availability of approved for Construction drawing and material, the fabrication supervisor retrieves the material from warehouse and handles it in accordance with the procedure and with specific care to avoid damage to surface preparation.
SEQUENCE OF WORK FOR ERECTION & FABRICATION
Erection shall be in accordance with reference documents listed above and shall include the setting of all columns, beams, trusses, grating and handrails, the erection and complete installation of all other structural steel to true line, grade and plumbness.
Structural steel shall be plumbed with suitable guy wires and held in plumb during field erection.
Guy wires shall be placed so as not interfere with other necessary work.
The setting out of the works, the accurate positioning, plumbing, lining, and leveling of all steel works shall be in accordance with the drawings.
Steel shall not be placed or erected on concrete foundations or floor slabs until the concrete has cured.
Holes shall not be made or enlarged by thermal cutting to correct fabrication errors.
Minor rectification to holes as necessary for field installation shall be made by drilling and subsequent touch up by zinc rich paint such as galvofroid.
All work during erection shall be securely bolted and if required temporarily braced.
No permanent bolting shall be executed until correct position and alignment have been obtained.
No equipment shall be supported from the steelworks until the structure is securely bolted, grouted and inspected.
Every erected steel component shall be free from contamination, twist and distortion.
Correction of minor misfits and a reasonable amount of reaming and cutting shall be considered a legitimate part of erection.
Any error in shop work which prevents the proper assembling and fitting up to parts by the moderate use of drift pins, reaming or cutting shall be reported immediately and approval shall be obtained for the method of correction prior to connecting the error.
The contact surfaces of bolted elements shall be free from rust, mill scale, grease, etc.
Bolts already used and previously tightened shall not be re-used.
All site bolted connections shall be assembled and torque tightened in accordance with Appendix “A”.
After the torque tightening of bolts shall be identified by the paint on the bolt head.
All material, plant and equipment used shall be of sound construction and free from flaws.
Bolts designed for transmitting forces in structural member connections, shall have a minimum diameter as follows:
- For main members, bracing’s and struts 20mm Minimum diameter
- For secondary, i.e. bracings, purlins, Ladders, handrails, etc. ( Unless noted otherwise on standard drawings). 16mm Minimum diameter
Except otherwise noted on design drawing, hole diameter for bolts shall be as follows Diameter bolt, plus:
For steel-to steel connections: 2mm
For steel-to-concrete connections (anchor bolts):
- Up to 24 mm bolt diameter: 4mm
- 24 to 32 mm bolt diameter: 6mm
- 32 mm bolt diameter and over: 8mm
The spacing of bolts in the direction in which the force is applied shall be at least three bolt diameters (measured in the direction of the force).
Minimum distance from center of bolt edge of plate measured in the direction of force shall be two bolt diameters, and measured at right angles to the direction of force, one and a half bolt
diameters.
Slotted hole connections are to be executed in such a way, that these connections may perform their design function, as indicated on the design drawings, and shall be provided with washers.
High strength bolts shall be used for structural steel-to-steel connections.
High strength bolts shall be used for in bearing-type connections and not as friction grip bolts
MOUNTING GUIDELINES
If required, additional drilling of beams, columns or other components shall be made to remedy fabrication mismatch / faults. Magnetic base drills shall be used for such work.
Based on the defined priority, structural members shall be assembled prior to erection for ease of construction with due consideration to lifting capability and study.
The following sequence shall be followed:
- Clean the foundation pockets and anchor bolts and chipping.
- Prepare shim plate above concrete mortar and control the required bottom elevation of steel structure base plate;
- Ensure the correct gap between bottom of base plate and top of concrete For required Grout thickness;
- Mounting of first level of columns/beams or assembly;
- Splicing and diagonal measurement at various phases /Floors;
- Check verticality of columns in two directions and base plate elevation;
- Bolt tightening;
- Control of splicing (bolted) and diagonal measurement at various phases;
- Control of bolting.
Nuts and washers shall be as specified in the drawings.
Tightening of joints shall require first tightening of mid bolts and then of adjacent bolts.
Tightening of big joints shall be carried out in two steps using first a torque of approx. 60% of the prescribed value and then the prescribed torque.
Grouting of the column base plates can be executed after checking for diagonal splicing and bolting or after completed operations as specified above.
Nelson nails or equivalent for grating fastening shall be nailed; surfaces where the Nelson nails will be applied shall be previously cleaned to remove grease, oxides, etc.
Friction joints column to column:
- Contact end surfaces of the joints between the column sections shall be flat.
- Joint covers and their padding if any shall be mounted after checking for the contact.
- Each joint before tightening shall be checked for holes coaxiality.
Friction joining of the column beam to the butt flange:
End flanges shall be delivered to site already connected at manufacturer shop after checking at a pre-erection stage for correct distance of the connected column flanges to beam.
Handrails and toe plates shall be not welded to the columns; however they shall be adequately jointed in the vicinity of the columns.
When not provided in the design drawings, the tube passage through grating shall be admissible only in case grating is adequately reinforced at the pass hole.
A toe plate shall be provided around the pass hole.
INTERMEDIATE INSPECTION
Each framework floor shall be checked for verticality and diagonals before and after tightening of bolts.
Survey instrument shall be used for checking of verticality. When executing the tests, proper consideration shall be given to the deformation changes occurring in the steel structure during a day
on account of exposure to the sunlight.
Verticality:
- Verticality and levelness shall be checked by means of a Survey instrument.
- For verticality reference shall be made to points (flags) marked on columns;
Diagonals (in plan):
- Diagonals shall be checked using a metric roller;
- All structural framework / floors shall be checked;
FINAL INSPECTION
Check for steel structure framework verticality, horizontal alignment and height shall be carried out after mounting.
Splicing shall be executed in accordance with prescriptions listed above.
Bolt torque tightening shall be as mentioned in the Appendix Completeness check as per approved for construction drawings.
After checking of connection, the erection drawing shall be marked to indicate acceptance.
TOLERANCES
The deviation in overall dimensions, positions, alignments, plumpness and elevations shall not exceed the limits specified in specification.
REPAIR OF GALVANIZED STEEL
Any damage to galvanized steel shall be repaired in accordance with ASTM A780. Before repairing the damaged galvanized coating, the exposed substrate metal shall be cleaned to bright metal and free of all visual rust, oil or grease. Any none adhering galvanizing shall be removed to the extent that the surrounding galvanizing is integral and adherent.
TESTING AND INSPECTION
Inspection and test shall be carried out by qualified personnel, coordinated by quality team, according to the Inspection & Testing Plan (ITP).
All structural steel material and fabrication shall be subject to inspection by client.
Welds shall be inspected by contractor according to the previsions of regulatory requirements with respect to technique, equipment, and acceptance criteria and personnel qualifications.
All welds shall be subject to random visual inspection by client .in addition, the following special requirements shall apply to welding inspection.
Grating shall be tagged with metal plate having raised letters so that the mark shall be seal welded to the grating prior to galvanizing.
Contractor may submit alternate proposal for marking galvanized members, subject to client’s written approval.
Quality engineer shall manage all Witness and Hold Points shown on the ITP, including convocation to contractor.
The form worked out shall be used for issue of the certificates listed in the Inspection and Test Plan.
Inspection mentioned in the Inspection and Test Plan shall be carried out using the following calibrated instruments:
Optical levels, steel metric rollers, water levels, manual dial type torque wrench for torque read-out.
10% of all connections for each bolt size shall be randomly selected and inspected, of each joint shall show the tightening value of high strength bolts. Such test shall be conducted on minimum 2 bolts per each joint.
Tested bolts shall be clearly marked with paint.
Each high strength bolts assembly shall consists of one heavy semi-finished hexagon structure bolts one heavy semi-finished hexagon nuts and one hardened washer to be used the nut.
In presence offload indication Washers, turn-of nut tightening follow-up; one nut sample per each size of bolts shall be unscrewed by at least 1/6 turn and then to check whether the prescribed torque brings the nut back to its original position.
Galvanized bolts shall not be reused after unscrewed; bolts may be reused after repaint by galvanize spray.
GROUTING
All bearing plates, loose lintels, beams and columns shall be shimmed to proper grade and level before grouting.
Grout material as specified in the technical specification or on drawing shall be used.
The sand-cements mixture shall be combined with the least amount of water to produce a low slump, place able grout.
Prior to setting structure, the concrete surface to receive grout shall be chipped to a depth of 6 mm to obtain a roughened surface.
After the structure is a place, positioned and shimmed immediately before grouting, the surface to receive grout shall be cleaned and wetted. Excess water shall be removed.
Grout shall be placed and thoroughly worked to eliminate voids and provide a uniform bearing surface under the base plate.
When specified on drawings, epoxy grout shall be used for grouting under heavy equipment where large bearing and /or vibration stresses occur. Epoxy grout shall be mixed by mechanical mixer and placed in accordance with manufacturer instruction.
QUALITY RECORDS
The following records shall be provided:
- ITP and Procedure
- Certificates of materials supplied
- Dimensional reports
- Bolt torque tightening reports
- Surface treatment reports
- Grouting reports
- Final dossier containing the report of the test carried out
APPENDIX: TORQE TIGHTENING OF STEEL STRUCTURE
The tightening torque shall be in accordance with the following Table.
Nominal Diameter of Bolt in mm Tightening Torque in NM
12 94
14 148
16 234
18 320
20 456
22 616
24 787
27 1150
30 1562
33 2125
36 2729
39 3532