PREFABRICATION MEETING
The intent of this appendix is to serve as a guide in conducting prefabrication meetings for structural steel.
A. Bridge Welding Code (AASHTO/AWS D1.5).
B. Standard Specifications, Supplemental Specifications, Special Provisions, Instruction Memorandums (IMs) and any other special requirements specified in the contract documents.
A. Designed by Engineer/Company
B. Status and Distributions of Shop Drawings, approved shop drawings shall be required.
C. Approved shop drawings shall be required prior to the start of any fabrication work.
D. Weld procedures are in integral part of the shop drawings, and shall be submitted for approval by Central Materials.
E. Prepayment of Structural Steel
F. Tentative Starting Date
G. Tentative Completion Date
H. Plant Working Hours; Number of Shifts
I. Work on Iowa’s projects shall not be interrupted due to scheduling conflict or due to change of priorities by the fabrication shop. Note: When and/ or if work stopped for more than four hours and the inspector has departed. He will be re-assigned, scheduling the return of the inspector will be at the discretion of the Structural Materials Engineer.
J. Iowa Department of Transportation Scheduled Holidays (Work or No Work).
A. Certified NDT & CWI Inspector Required (Current Approved List)
CWI – QC Inspectors who are assigned to production cannot perform the CWI-QC duties on Iowa DOT projects.
B. Copy of AWS Certification Required
C. Quality Control Specified Duties (AASHTO/AWS 6.5)
D. Discuss Quality Control Record Keeping System (Description by Plant Personnel).
E. Quality Control Manager is responsible to whom?
F. How many CWI Inspectors does the plant have? Any assigned to 2nd and 3rd shifts?
NON-DESTRUCTIVE TESTING
A. Type of Magnetic Particle Inspection to be used (yoke or prod). Current (AC-DC-DC Rectified).
B. County name and design number must be shown on the radiographs.
C. Marking tension and compression flanges on radiographs
D. Additional radiographs of compression flanges
E. Edge blocks are required to show both top and bottom edges in radiographs. The maximum gap between the edge block and the plate shall not exceed 1/16 in.
F. Two (2) sets of radiographs are required
G. The maximum number of weld joint repairs is three, unless otherwise approved by the Structural Materials Engineer.
All steel, iron, and coating products shall be of a domestic origin, melted, and manufactured in the USA. The fabricator shall certify to the State of Iowa that the materials used are of a domestic origin.
A. Submit copies of the purchase order to DOT inspector.
B. Mill Test Certifications and Charpy V-Notch Tests - 3 copies are required (1 copy for prepayment, 2 copies at start of fabrication).
C. Material supplied from stock
D. Paint - Top coat Fed. Color 20045 (Semi-gloss)
E. Structural Steel Assurance Sample (Sample from tension flange as first choice, 4” x 4” for Charpy V-Notch Impact Testing second choice from the web plate third choice from splice plate. Rolling direction must be marked on the sample.)
F. Bearings – Fabricated by:
G. Bolts and Bolting
1. Source – Approved Sources
2. Sampling for Approval (shop and field bolts, extra number are required)
3. Rotational Capacity Testing
4. Turn of the Nut Method of Installation (marking bolts)
5. Bolt tension Testing Device - calibrated within the last six months
H. Non-compliance material, shall require repair procedure submitted for approval, and a detailed description of the corrective action taken to correct the problem.
STORAGE, COLOR CODING, & HEAT NUMBERS
A. Steel must be properly supported during storage.
B. Heat numbers must be painted on main members.
C. Steel with Charpy Test requirements are to be identified separately (marked CVN).
D. Steel from stock shall be identified by heat numbers and ASTM Grade.
E. The Fabricator shall furnish an affidavit in the form of a cutting list, listing heat numbers and grade of steel, and a statement certifying that throughout the fabrication operation the identification of steel has been maintained in accordance with the specification. (Article 2408.02, B, 12)
F. On all State of Iowa contracts, specifically involving Federal-aid, all products of iron, steel, and/or coating of steel, which are incorporated into the work, must have been from a domestic origin melted and manufactured in the USA. The Fabricator shall certify by a letter to the Iowa DOT and to the Contractor that all materials used are of domestic origin. (Article 1107.06B)
MAIN STRESS-CARRYING MEMBERS (Article 2408.02B)
The main members of steel structures are defined to include rolled sections or flange and web plates in main beams and girders, floor beams, stringers, abutment diaphragms, cross frames carrying direct live loads, lateral bracing in horizontally curved bridges, cover plates, bearing stiffeners, bearing devices, splice plates, gusset plates, and stiffeners connecting live load carrying members to main beam or girder webs. The contract documents may also designate other members as main members.
For members that require Charpy V-Notch tests, see Article 4152.02.
All of the above require Mill Test Certifications and heat number identification.
All of the above members have restrictive specifications governing shearing and hole punching (Articles 2408.02L).
SECONDARY MEMBERS & MISCELLANEOUS ITEMS
Only approved fabricator shall fabricate secondary members and miscellaneous items. See IM 557, Appendix A and B.
SHEARING VS. FLAME CUTTING (Article 2408.02G (Shearing Edge Finish), 2408.02H (Thermal Cutting), & 2408.03B(Welding)
A. All main members shall be oxygen cut, unless otherwise authorized by the engineer (Structural Materials Engineer).
B. Web splice plates and bearing stiffeners 5/8 in. or less may be sheared.
C. Secondary members may be sheared, but sharp corners must be dulled by grinding.
D. Plates shall be cut in the direction of stress in main members except web splice plates may be cut in either direction.
E. Shearing of flange splice plates is not permitted.
HOLE PUNCHING (Article 2408.02, L2)
A. Holes in main stress carrying members shall be subpunched and reamed, subdrilled and reamed or drilled full size.
B. Holes in secondary members may be punched but with restrictions:
1. Thickness of 3/4 in. and less for carbon steel and 5/8 in. and less for alloy steel.
2. Any other restrictions are defined in Article 2408.02L.
C. Concerning misplaced or damaged holes, DO NOT WELD CLOSED without the approval of the Structural Materials Engineer
D. Deburring of all holes is required.
BENT PLATES (Article 2408.02F)
A. The bend line shall be at a right angle to the direction of rolling.
B. Before bending, corners shall be rounded to a 1/16 in. radius in the bend area.
C. No cracking of the plate is permitted.
D. Bend radii shall be measured to the concave face (See table - 2408.02F).
Note: Low alloy steel in thickness over ˝” may require hot bending for small radii.
OXYGEN CUTTING (Article 2408.02H)
A. Oxygen cutting for main members shall be done only when the temperature is above 40°F in the area of the cut, and in a surface-dry condition.
NOTE: Special preheat requirement may be required in Special Provisions for a specific project.
B. Cut surface shall meet the ANSI value of 1000.
C. Repair of oxygen cut defects by welding is prohibited without approval of the Structural Materials Engineer (AASHTO/AWS 3.2.2.1).
D. Mechanical guided radius cuts of 1 in. minimum radius are required unless waived by the engineer (AASHTO/AWS 3.2.2 and 3.2.4).
HEATING OF STEEL (Article 2408.02K)
A. Steel heating procedures shall be submitted to Central Materials Structural Materials Engineer prior to fabrication.
B. Heating procedures are required for the following:
1. Camber correction
2. Horizontal curving of beams and girders
3. Correcting of flange tiltage
4. Web flatness correction
C. A heating log shall be maintained by the fabricator detailing the piece number with location, date, time, temperature, and the reason for any heat adjustment. The DOT inspector must be notified prior to the start of the heating process and / or an heat adjustment and the QC Inspector shall be present.
D. Heat shall not exceed 1150°F.
E. Personnel heating steel shall check temperature frequently, using two (2) different temperature indicators (one higher than the other) suggest 1050°F and 1150°F.
F. Cooling shall be normal air-cooling above 600°F.
WELD PROCEDURES (AASHTO/AWS 5.1)
A. All welding procedures must be approved before use.
B. Sequence of welding cover plates is a part of welding procedure.
WELDING (Article 2408.03B)
A. Welding of main members and welding of attachments thereto shall be performed using only shielded metal arc, flux-cored arc, submerged arc, and/or stud welding processes. Unless otherwise approved by the Structural Materials Engineer, all welding of butt splices, stiffener bars to web and flange to web welds shall be done using the submerged arc process. Shielded metal arc welding may be used for repairs to butt splices and flange to web welds.
B. QC Inspector shall make sure that welding personnel read, understand, and initial the weld procedures.
C. Weld procedures shall be posted by the welding station and shall be initialed by the welders.
D. Weld procedures shall be sent directly to Central Materials for approval.
E. Preheat and interpass temperature (other than A709 Grade 70W, 100, 100W, HPS 70W steel)
F. Filler Metal shall comply with the requirements of AWS Code. A certificate of compliance from the manufacturer for each consumable to be used shall be attached to the weld procedures.
Thickness in. Temperature °F
Through 3/4 in. 50°F
Over 3/4 in. through 1 1/2 in. 70°F
Over 1 1/2 in. through 2 1/2 in. 150°F
Over 2 1/2 in. 225°F
G. Use of approved electrodes for all welding – certificate of conformance shall be required and must be submitted for acceptance and approval.
H. Proper storage of low hydrogen electrodes (AASHTO/AWS 4.5.2).
I. Proper storage of sub arc flux and wire (AASHTO/AWS 4.8.3).
J. Welding size, profile and undercut (AASHTO/AWS 3.6).
K. Preparation of web to flange weld areas (AASHTO/AWS 3.2.1).
L. No intersection welds (refer to design drawings).
M. The fillet welds connecting the stiffener or connection plate to the web shall be started at the end of the stiffener that is adjacent to the tension flange and progress toward the compression flange, with an option to start at both flanges and end near the center of the web
N. Gouging – Arc gouging, backgouging, and oxygen gouging: a proper gouging repair procedure shall be used to avoid the retention of carbon deposits. Gouged surfaces shall be ground to bright metal.
The intent of these requirements is to avoid crater cracks at the end of the stiffener weld in a tension area.
TACK WELDING (AASHTO/AWS 3.3.7)
A. Tack welds are subject to the same quality requirements as final welds.
B. Tackers are to be qualified per the revised AWS paragraph 5.23.3 and as found in Article 2408.03, 5.23 of the Standard Specifications.
C. Tack welds outside of weld areas must be authorized, that is, shown on the approved shop drawings.
D. Tacking of fill plates or splice plates is not permitted.
E. Proper positioning as per the tack welder's qualification is required.
F. Arc strikes will be repaired by grinding and NDT tested by acid etching. The QA Inspector must witness these procedures.
STUD WELDING (AASHTO/AWS Section 7)
A. Materials Certification for Studs (AASHTO/AWS 7.3). Approved sources of shear connector studs – see IM 453.10, Appendix A.
B. Operator Qualification (AASHTO/AWS 7.7.4), and IM 558.
C. Quality Control (AASHTO/AWS 7.7), and IM 558.
D. Inspection Requirements (AASHTO/AWS 7.8), and IM 558.
A. Camber tolerance at bearing is ±0.
B. Camber tolerance at midpoints is ±1/2 in.
C. No points shall vary more than ±1/2 in. from that indicated on erection drawing.
D. Camber is to be shown on erection drawings at bearing points, splice points and at midpoints of beams or girders.
E. Camber may be checked with wire, transit, level, or laser.
F. Maximum 1/2 in. minimum 1/8 in. opening between girders. (2408.03F3) for plate girder.
G. Maximum 1/4 in. minimum 1/8 in. opening between beams. (2408.03F3) for rolled beam.
H. Shop drawings for steel structures shall show accumulated dimensions for each line of beams or girders in laydown. The accumulated dimensions shall be shown at the locations of the following details: bearings, welded or bolted splices, stiffeners, gusset plates, flange defector holes, drain connecting holes, cover plate ends, and holes for abutment, reinforcing bars when required. (2408.03A)
I. The tolerance for the angles of connecting angles or stiffeners, which connect main members, is ±1/2° from specified angle. Refer to Article 2408.03 of the standard specifications modification to AASHTO / AWS D1.5 paragraph 3.5.1.14
SURFACE PREPARATION, CLEANING OF PAINT SURFACES, AND PAINTING(2408.02Q)
(Specifications Article 2408.02Q.1)
A. All steel surfaces to be painted shall be given a near white (SSPC – SP10)
B. Blast cleaning with grit when specified or with any other means to achieve the required surface profile.
C. Abrasive blast cleaning – surface preparation requirements:
1. SSPC-SP6 Commercial blast for non-painted surfaces
2. SSPC-SP10 Near white blast for painted surfaces. A minimum of 1.0 mil and a maximum of 3.0 mils shall be achieved on surfaces including the thermal cut edges.
D. All oily or greasy residues shall be removed with solvent in accordance with SSPC-SP1.
E. All surfaces to be coated shall be clean and dry.
F. All surfaces to be painted shall be coated as soon as possible after blasting and before formation of any surface rust and not later than 16 hours after blasting the surface.
G. Approved paints are listed in IMs 482.02, 482.04, 482.05, 482.06, 482.07
H. The inorganic zinc – silicate paint film shall be considered cured and ready for shipment (top coat) after achieving a resistance rating of “4” as verified by 50 MEK rubs as per ASTM D 4752. (Article 2408.02)
I. Certified painters are required to perform the required painting. Certification shall be renewed on an annual basis.
J. Water mist – all unpainted area of outside surfaces of the fascia girders shall receive after blasting three uniform water mist applications at 24-hour interval between applications.
· Each succeeding water mist application shall be applied only on a dry surface.
· The water mist application shall be performed 48-hours after the painted surfaces have been properly and completely cured.
· All water mist applications shall be witnessed by the Q.A. inspector.
· Definition of water mist: The water mist would be in the form of water particles in the form of particles floating or falling at or near the surface. A spray stream of water will not be acceptable.
K. The following areas shall be painted:
1. All of the weathering steel for a distance of 1.5 times the girder depth on each side of the expansion joints
2. All weathering steel embedded into an abutment shall be painted, with top of the top flange to be prime coated only.
3. All bearing assemblies except the galvanized masonry plates and galvanized swedged anchor bolts, unless otherwise specified in the plans.
4. Embedded girder ends over the entire embedment length, plus an additional distance of 1.0 foot.
5. Exterior surfaces of all galvanized components which are indicated in the plans to be painted and all galvanized floor drains shall be prepared according to the written recommendations of the paint manufacturer and painted with the same type of waterborne acrylic paint used for top coat.
· Final inspection of welding, grinding and general workmanship will be done after blast cleaning and prior to painting.
· All fabricated items shall be stamped with approval stamp prior to shipping.
· Fabricator cannot release any fabricated items for shipping without a signed “Fabrication Inspection Shipment Release Form” by the DOT QA Inspector. This form is labeled as “The Fabrication Inspection Shipment Release Form” - Appendix B of this IM.
The QA Inspector is present at the plant to assure the Iowa Department of Transportation that the structure is fabricated in accordance with the applicable specifications. The QA Inspector does not assume the responsibility of quality control for the fabricator.
The QC Inspector shall be present at all times during fabrication and shall be knowledgeable of the specification requirements to ensure that fabrication performance is in accordance with the drawings.
When any phase of the work occurs beyond the normal schedule, it is the fabricator's responsibility to give the QA Inspector sufficient advance notice so he/she may arrange their schedule accordingly.