Section 2408. Steel Structures.
The provisions of this section shall apply to fabrication and erection of all types of bridge structures in which the main members spanning the various supports are composed of steel and of other structures or parts of structures where the design or intended use of steel is based on physical or chemical properties of the steel. Unless modified elsewhere in the contract documents, all fabrication to which this section applies shall be done in the states, territories, and possessions of the United States and in other locations within the geographic limits of North America and only in steel fabrication shops and plants that are approved as per Materials I.M. 557 prior to the letting. All main member fabrication, except bearing devices, shall be fabricated by plants certified as Category III, Major Steel Bridges, under the provisions of AISC's Quality Certification Program. The steel superstructure will be placed on a substructure constructed as provided in Section 2405. The requirements of Sections 2403, 2404, 2410, 2411, 2412, 2413, and 2508 shall apply to the various types of construction. The various types of structures shall be built in conformance with the contract documents.
2408.02 WORKING DRAWINGS, SHOP DRAWINGS, CHANGES, AND SUBSTITUTIONS.
The Contractor shall submit detailed shop drawings in accordance with Article 1105.03. Welding procedures shall be considered an integral part of shop drawings and shall be reviewed for each contract.
A. All material ordered or work done prior to review of the shop drawings shall be at the Contractor's risk. Shop drawings for steel structures shall give detailed dimensions and sizes of component parts of the structure and details of all miscellaneous parts, such as pins, nuts, bolts, drains, etc.B. Shop drawings shall identify each piece that is to be made of steel required to be other than ASTM A 709/A 709M Grade 36 (Grade 250) steel. Pieces made of different grades of steel shall not be given the same assembling or erecting mark, even though they are of identical dimensions and detail.
C. Sections other than those shown on shop drawings reviewed by the Engineer may be used under the following provisions:
1. That the substitute section is equal in strength and stiffness to the section originally shown.
2. That the substitution is approved by the Engineer.
3. That the substitution is made at no additional cost to the Contracting Authority.
D. 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 and drain connecting holes.
2408.03 QUALITY OF WORK AND FINISH.
Quality of work and finish shall be equal to the best practice in modern bridge shops. Shearing and chipping shall be neatly and accurately done, and all portions of the work exposed to view shall be neatly finished.
2408.04 MATERIAL AND MATERIAL IDENTIFICATION.
The following base materials required in steel structures shall meet requirements of Division 41.
A. Rolled Plates, Shapes, and Eyebars.
Section 4152 shall apply.
B. Forgings and Castings.
Section 4153 shall apply.
C. Bronze Metal (rolled or cast).
Article 4190.03 shall apply.
D. Bolts, Nuts, and Washers.
Article 4153.06 shall apply.
E. Bearing Pads.
Article 4195.02 shall apply.
Article 4100.07 shall apply.
G. Identification of Steel During Fabrication.
1. 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 and cross frames 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.
2. Before steel, as received, is cut for fabrication, the Engineer shall be furnished two copies of certified mill test reports showing chemical and physical test results for the steel involved.
3. For all steels, the Contractor's system of record keeping for individual pieces and the issuance of cutting instructions to the shop (generally by cross referencing of the assembly marks shown on the shop drawings with the corresponding item, covered on the mill purchase order) shall be such as to maintain identity of the mill test report number. A copy of the cutting instructions shall be furnished to the inspector.
4. The Contractor may furnish from stock material which can be identified by heat number and mill test report.
5. Main members and component parts thereof, unless excepted by the Engineer, shall be identified by heat number; also, each piece of steel, other than ASTM A 709/A 709M Grade 36 (Grade 250) steel, shall show clearly and legibly its proper color code. These identifications shall be maintained until steel is cleaned for painting.
6. Individually marked pieces of steel, which are used in furnished size or reduced from furnished size only by end or edge trim that does not disturb the heat number or color code or leave any usable piece, may be used without further color coding providing the heat number of color code remains legible.
7. Pieces of steel, other than ASTM A 709/A 709M Grade 36 (Grade 250) steel, which are to be cut to smaller size pieces shall, before cutting, be legibly marked with the proper color code.
8. Individual pieces of steel, other than ASTM A 709/A 709M Grade 36 (Grade 250) steel, which are furnished in tagged lifts or bundles shall be marked with the proper color code immediately upon being removed from the bundle or lift.
9. Pieces of steel other than ASTM A 709/A 709M Grade 36 (Grade 250) steel, which prior to assembling into members will be subject to fabricating operations, such as blast cleaning, galvanizing, heating for forming, or painting, which might obliterate paint color code marking, shall be marked for grade by steel die stamping or by a substantial tag, firmly attached.
10. During fabrication, up to the point of assembling members, each piece of steel, other than ASTM A 709/A 709M Grade 36 (Grade 250) steel, shall show clearly and legibly its specification identification color code as shown in the following table:
Section Steel Grade Color Code ASTM A 709/A 709M
ASTM A 709/A 709M
ASTM A 709/A 709M
ASTM A 709/A 709M
Red and Orange
Green and Yellow
Blue and Yellow
11. Other steels not covered above and not included in ASTM A 6/A 6M shall have an individual color code which shall be established and on record for the Engineer.
12. The Contractor 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 this specification.
Where indicated in the contract documents, "rough bolted connections" may be used. In these connections, bolts may be hex-head bolts meeting requirements of ASTM A 307. Ribbed bolts may be used only when specified in the contract documents. Each ASTM A 307 hex-head bolt shall be fitted under the nut with one ANSI B18.21.1 helical spring lock washer, except that expansion joint bolts that are to be removed after the expansion joint is installed or anchor bolts through slotted holes where a cut washer is provided shall not require helical spring lock washers.
When rough bolts or ribbed bolts are to be used, the number of each size and length furnished shall be 5% greater than the number shown in the contract documents. When turned bolts or high strength bolts are to be used, the number of bolts of each size and length and the corresponding number of washers and nuts furnished shall be 2% greater than the number shown in the contract documents.
2408.06 PINS AND ROLLERS.
Pins and rollers shall be turned to the specified dimensions and shall be smooth, straight, and free from flaws.
Pins and rollers more than 9 inches (225 mm) in diameter shall be forged and annealed.
Forgings for pins larger than 9 inches (225 mm) in diameter shall have a 2 inches (50 mm) diameter hole bored longitudinally through the center after the forging has cooled below the critical range and before the forging is annealed. Pins showing a defective interior condition shall be rejected.
2408.07 SHOP STORAGE OF MATERIAL.
Structural material, either plain or fabricated, shall be stored above ground upon platforms, skids, or other supports. It shall be kept free from dirt, grease, and other foreign material.
2408.08 STRAIGHTENING MATERIAL AND PLACING MEMBERS.
All rolled material must be straight when it is laid out for work. If straightening is necessary, it shall be done by means which will not damage the metal. Sharp kinks or bends will be sufficient cause for rejection of the material. Heat correction shall be done only when approved by the Engineer. Unless otherwise shown in the contract documents or ordered by the Engineer, members which deviate from a straight line by an amount within the tolerance specified in ASTM A 6/A 6M shall be placed in the structure so that the stress to be imposed will tend to straighten the member. Heat straightening of ASTM A 709/A 709M Grade 100/100W (Grade 690/690W) steel will not be permitted.
2408.09 BARS AND PLATES.
Unless otherwise noted on the plans, and as excepted below, all main stress carrying members composed of plates and all steel material designated on plans as "bar" or "UM plate" shall have rolled edges or may be thermal cut, provided that with thermal cut plates a smooth surface is secured by the use of a mechanical guide approved by the Engineer in accordance with Article 2408.13. Web splice plates and bearing stiffeners 5/8 inch (16 mm) or less in thickness may be made of sheared plates.
Unless otherwise noted in the contract documents, secondary stress members may be made of sheared plates. If sheared plates are used, their exposed sharp corners shall be dulled by grinding.
Plates shall be cut so the direction of stress in main members is in the direction of rolling, except web splice plates.
Main stress carrying members shall be those members defined in Article 2408.04 as main members.
2408.10 BENT PLATES.
Unwelded, cold bent, load carrying, rolled steel plates shall conform to the following:
1. They shall be so taken from the stock plates that the bend line will be at right angles to the direction of rolling.
2. Bending shall be performed such that no cracking of the plate occurs. Minimum bend radii, measured to the concave face of the metal, are shown in the following table for all grades of structural steel in this specification.
Thickness in Inches (millimeters) Up to 1/2 (12) Over 1/2 to 1
(12 to 25)
Over 1 to 1 1/2
(25 to 40)
Over 1 1/2 to 2 1/2
(40 to 60)
Over 2 1/2 to 4
Radii for Metal
2 t 2.5 t 3 t 3.5 t 4 t NOTE: Low alloy steel in thicknesses over 1/2 inch (12 mm) may require hot bending for small radii.
Allowance for springback of ASTM A 709/A 709M Grade 100/100W (Grade 690/690W) steel should be about three times that for structural carbon steel. For brake press forming, the lower die span should be at least 16 times the plate thickness. Multiple hits are advisable.
If a shorter radius is essential, plates shall be bent hot at a temperature not greater than 1,200°F (650°C), except for ASTM A 709/A 709M Grade 100/100W (Grade 690/690W) steel. If ASTM A 709/A 709M Grade 100/100W (Grade 690/690W) steel plates are bent at temperatures greater than 1,125°F (610°C), they must be requenched and tempered in accordance with the producing mill's practice. Hot bent plates shall conform to Requirement 1 above.
3. Before bending, the corners of the plate shall be rounded to a radius of 1/16 inch (1.6 mm) throughout that portion of the plate at which the bending is to occur.
2408.11 SHEARED EDGE FINISH.
Sheared edges of plates more than 5/8 inch (16 mm) in thickness and carrying calculated stress shall be planed to a depth of 1/4 inch (6 mm) and ground, if necessary, to secure a finish equivalent to an ANSI 1,000 (25 µm) surface roughness. Re-entrant corners shall be filleted to a minimum radius of 1 inch (25 mm) before cutting.
2408.12 THERMAL CUTTING.
Article 2408.13 shall apply. Thermal cutting of main stress carrying members shall be done only when the steel in the area of the cut is above 40°F (4°C) and in a dry surface condition.
Welding procedures and requirements for the following items shall conform to the ANSI/AWS D1.1 Structural Welding Code, except that filler metal and welder qualification requirements shall be according to AASHTO/AWS D1.5M/D1.5-02 as modified below.
A. Bridge Components and Miscellaneous Items.
This includes bearing assemblies, sole plates, expansion joint devices, pile and appurtenances, drainage system components, guardrail connections, metal railing, chain link enclosures and wire fence components, conduit systems, and tread plates.
B. Traffic Signal Components.
C. Sign Support Components.
D. Lighting Structure Components.
E. Pre-Engineered Pedestrian Bridges.
Welding and fabrication of steel structures shall conform to AASHTO/AWS D1.5M/D1.5-02, as modified by this Specification.
Each of the modifications in this Article is referenced by the appropriate paragraph number in AASHTO/AWS D1.5M/D1.5-02, to which it is a modification.
Table of Contents
Modifications to AASHTO/AWS D1.5M/D1.5-02 Bridge Welding Code
SECTION 1, GENERAL PROVISIONS
1.3 Welding Processes
SECTION 3, WORKMANSHIP
3.2 Preparation of Base Metal
3.5 DIMENSIONAL TOLERANCES
SECTION 5, QUALIFICATION
Part A, General Requirements
5.2 Qualification Responsibility
Part B, Welding Operator, and Tack Welder Qualification
5.21 General Requirements
5.23 Qualification Tests Required
SECTION 6, INSPECTION
Part A, General Requirements
6.7 Nondestructive Testing
Part B, Radiograph Testing of Groove
Welds in Butt Joints
6.10 Radiograph Procedure
6.12 Examination, Report and Disposition of Radiographs
SECTION 1. General Provisions
1.3 Welding Processes
ADD the following new Paragraph 188.8.131.52 after the existing 1.3.1:
184.108.40.206 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 Engineer, all welding of butt splices and flange to web welds and stiffeners 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.
220.127.116.11 The WPS shall be initialed by the welder and posted at the welder's workstation at all times during welding operations.
REPLACE Paragraph 1.3.2 with the following:
1.3.2 Electroslag (ESW) and electrogas (EGW) welding are specifically disapproved for use.
SECTION 3. Workmanship
3.2 Preparation of Base Metal
ADD the following paragraph before the existing first Paragraph 3.2.2:
For main members, thermal cutting is limited to oxygen cutting except that plasma arc cutting of web and stiffeners may be used when approved by the Engineer.
DELETE the last sentence of Paragraph 3.2.7 which reads "Excess Camber may be corrected by heating without the engineer's approval."
3.5 Dimensional Tolerances
REPLACE all of the text and tables of Paragraph 18.104.22.168 with the following:
Camber of main members of continuous or simple span bridges with lines composed of rolled beams, beams and girders, or girders, shall be fabricated so that when the members are assembled in laydown with bearing points accurately positioned as shown on the erection diagram, points on any member shall not vary in the offset position from that indicated in the erection diagram by more than ± 1/2 inch (13 mm).
The erection diagram on the shop drawings shall show camber offsets at bearing points and splice points, and at midpoints of individually cambered beams or girders.
REPLACE Paragraph 22.214.171.124 with the following:
Permissible variation in specified sweep for horizontally curved welded beams or girders is
± 1/8 in. x No. of ft of total length
(± 1 mm/m of the total length)
provided the member has sufficient lateral flexibility to permit the attachment of diaphragms, cross-frames, lateral bracing, etc., without damaging the structural member or its attachments.
REPLACEParagraph 126.96.36.199 with the following:
188.8.131.52 Mechanically connected joints and splices of main members with surfaces intended to be parallel planes shall be nearly parallel after connection, and the surfaces to be in contact shall have an offset no greater than 1/16 inch (1.6 mm). after all filler plates have been added, if any. The accuracy of the angle of connecting stiffeners, angles, or plates shall be ± 0.5 degrees, when measured at the hole locations.
REPLACE Paragraph 3.7.4 with the following:
Prior approval of the Engineer shall be obtained for repairs to base metal, repair of major or delayed cracks, or for a revised design to compensate for deficiencies.
ADD the following new first paragraph ahead of existing Paragraph 3.7.7 as follows:
3.7.7 The approval of the Engineer is required for all corrections of mislocated holes.
ADD a new Paragraph 3.7.8 after the existing 3.7.7 as follows:
3.7.8 The maximum number of repairs to unacceptable defects in a butt splice shall be three, i.e., the times a butt splice may be opened, welded closed, and resubmitted for NDT inspection, unless otherwise approved by the Engineer.
SECTION 5. Qualifications
Part A. General Requirements
5.2 Qualification Responsibility
REPLACE Paragraph 5.2 with the following:
To qualify welding procedures, the Contractor shall produce test weldments, perform nondestructive testing and machine specimens for mechanical testing in accordance with this code. The Contracting Authority shall witness the production of test weldments and conduct mechanical tests.
Part B. Welder, Welding Operator, and Tack Welder Qualification
5.21 General Requirements
5.21.4 Period of Effectiveness
REPLACE Paragraph 5.21.4 with the following:
Shop welder's, welding operator's, or tack welders qualification herein specified shall be considered as remaining in effect from the end of the month in which the tests were taken, for a period of 1 year. The qualification for the above may be extended annually, based on a letter from the fabricator/Contractor certifying that they have been engaged in the process(es) for which they qualified without interruption of more than 6 months during the preceding twelve months, or by requalification. The field welder's qualification herein specified will be considered as remaining in effect from the end of the month in which the test was taken, for a period of 1 year. For field welders who have successfully passed their qualification tests without failure for 3 consecutive years, requalification will only be required every 2 years. Requalification may be required at any time there is a specific reason to question a welder's ability to make sound welds.
REPLACE Paragraph 184.108.40.206 with the following:
220.127.116.11 To qualify welders, welding operators, and tackers, the Contractor shall furnish test weldments, and perform nondestructive testing in accordance with this code. The Contracting Authority shall witness the production of test weldments and conduct mechanical tests. The Contractor may, at no additional cost to the Contracting Authority, engage an outside firm or agency to witness production of test weldments and conduct mechanical tests. The acceptance of work performed by an outside firm or agency is the prerogative of the Contracting Authority.
5.23 Qualification Tests Required
ADD a new Subparagraph 5.23.1 (5) after the existing 5.23.1 (4) as follows:
(5) Plate weld tests may also be accepted for qualification of welding pipe piling of any diameter.
REPLACE Paragraph 5.23.3 with the following:
Tack Welder Qualification. A tack welder shall be qualified by fillet-weld-break specimen made using the same criteria as listed for plate-fillet welder qualification in Table 5.6. The tack welder shall make a 1/4 inch (6 mm) maximum size tack weld approximately 2 inches (50 mm) long on the fillet-weld-break specimen, as shown in Fig. 5.28.
SECTION 6. Inspection
Part A. General Requirements
6.7 Nondestructive Testing
REPLACE Subparagraph 18.104.22.168(1) with the following:
22.214.171.124(1) 100% of each joint subject to tension or reversals of stress, except that on vertical butt weld splices in beam or girder webs, only 1/3 of the web depth beginning at the point, or points, or maximum tension need be tested. If unacceptable discontinuities are found in the first 1/3, the remainder of the weld shall be tested.
REPLACE Subparagraph 126.96.36.199(2) with the following:
188.8.131.52(2) 50% of each joint subject to compression or shear in each main member as specified, except that longitudinal butt weld splices in beam or girder webs need not be tested by radiographic or ultrasonic testing unless so specified in contract document. If unacceptable discontinuities are found the first 50% of joint, the entire length shall be tested.
Part B. Radiographic Testing of Groove Welds in Butt Joints
6.10 Radiographic Procedure
ADD the following new Paragraph 184.108.40.206 after existing 220.127.116.11:
18.104.22.168 Where areas being radiographed are adjacent to the edge of the plate, edge block shall be used.
6.12 Examination, Report, and Disposition of Radiographs
REPLACE Paragraph 6.12.3 with the following:
6.12.3 Two sets of radiographs shall be taken for welds subject to radiographic testing, including any that show unacceptable quality prior to repair. One radiograph of each test shall, upon completion of Q.C. and Q. A. interpretation, be forwarded to the Office of Materials, Ames, Iowa. The second set of radiographs shall be retained by the Contractor as part of on-site inspection records. Upon completion of the project, this second set will become the property of the Contractor.
2408.14 STRESS RELIEF HEAT TREATMENT.
Structural members which are indicated in the contract documents to be stress relieved, shall have finished machining, boring, and straightening done subsequent to heat treatment. Stress relief heat treatment shall be done in accordance with Section 4.4 of AASHTO/AWS D1.5M/D1.5-02.
Members of ASTM A 709/A 709M Grade 100/100W (Grade 690/690W) steel shall not be annealed or normalized and shall be stress relieved only with approval of the Engineer.
A record of each furnace charge shall identify pieces in the charge and show the temperatures and schedule actually used. Instruments such as recording pyrometers shall be provided for determining at any time the temperature of members in the furnace. Records of the treatment operation shall be submitted to the Engineer for approval.
All members, such as bridge shoes, pedestals, rockers, or other parts, which are built up by welding sections of plate together, shall be stress relieved, unless otherwise stated in the contract documents.
2408.15 PLATE GIRDERS.
Plate girders shall be fabricated in accordance with the following requirements:
A. Welded Girders.
1. Web Plates.
Edges of a girder web shall be cut true and straight or to camber and other detailed curvatures with the accuracy necessary that will serve a correct fit up to the flange plate. Web plates shall be completely shop welded separately before assembly with the flange plates as shown in the contract documents.
2. Web Stiffeners.
(a) Bearing Stiffeners.
End stiffeners of girders and stiffeners intended as supports for concentrated loads shall have full bearing on the flanges to which they transmit load or from which they receive load. These surfaces shall be milled or ground, or, on weldable steel in compression areas of flanges, welded as shown in the contract documents.
(b) Intermediate Stiffeners.
Intermediate stiffeners (not intended to support concentrated loads) shall, unless shown or specified otherwise, fit sufficiently tight to be in close contact with the flanges.
(c) Stiffener Welding.
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. Before welding, there shall be no gap between the web and the intermediate stiffeners, bearing stiffener or connection plates in excess of 3/32 inch (2.4 mm).
3. Flange Plates.
Flange plates shall be made of universal mill plates or thermal cut plates which are cut in accordance with Article 2408.12. Flange plates for welded girders shall be completely shop welded separately before assembly with the web plate as shown in the contract documents.
4. Tack Welding.
Tack welding and fit up procedures shall be submitted to the Engineer for review and approval.
2408.16 CAMBER OF ROLLED BEAM AND PLATE GIRDER SPANS.
Rolled beams and plate girders constituting the main supporting members of a span shall be cambered in accordance with the following: When specified in the contract documents, rolled beams and plate girders shall be cambered. Unless otherwise specified in the contract documents, this camber shall be a uniform, approximately circular curve for the entire length of the beam or between designated points. Compound or reverse curves may be required on special designs as shown on the plans.
Camber of beam spans may be produced either in the rolling mill or in the fabricating shop by gagging. Camber of beam spans may also be induced or corrected by local heating. In all cases, beams shall conform to the specified shape within tolerance limits. Beams shall be free from kinks, buckles, or other local imperfections. Improper heating or cooling which might affect grain structure, strength, or ductility of the metal shall be cause for rejection.
Rolled beams may be cambered by heating in the following manner: Welding of cover plates shall be completed before commencing final heating operations. The beam shall be supported near its ends in such a manner that the side to be made concave faces upward. An oxyacetylene, butane, natural gas, or other approved gas flame shall be applied to areas so selected that distortion other than the required camber will not occur. Heat shall be applied by playing the flame over the section to be heated until the metal attains a maximum temperature of 1,000°F to 1,200°F (540°C to 650°C). Procedures used for controlling the temperature shall include the use of temperature indicating crayons, liquids, or bimetal thermometers. The Engineer shall be notified before any heating is done.
The heated areas shall be wedge or triangular shaped with an included angle between 20 and 45 degrees. The vertex of the angle shall be located approximately 1 inch (25 mm) above the point on the web midway between flanges. The flame from the torch, or torches, shall be slowly played over the area to be heated, commencing at the vertex of the angle and finishing at the widest part of the heated wedge, which shall extend across the width of the flange on the side to be made concave. The torch, or torches, shall be so manipulated that the total area of the heated zone shall rapidly be brought to the proper temperature at the same time, as nearly as practicable.
The heated sections shall be uniformly spaced at short intervals to produce uniform curvature. Not less than three sections shall be heated, and heating of additional sections may be required in the case of unusually long or heavily cambered beams. The metal shall be air cooled, slowly and away from wind or drafts. In no case shall water be used to cool the metal, nor shall any area be heated more than once.
Plate girders shall be cambered by cutting the web plate to the proper curvature to produce a camber within the allowable tolerance. Cutting of the web plate shall include an allowance to compensate for the effect of the heat of welding operations to be performed on the girder during fabrication.
Camber in plate girders shall not be induced or corrected by local heating unless prior approval is obtained from the Engineer. Heating of ASTM A 709/A 709M Grade 100/100W (Grade 690/690W) steels will not be permitted.
2408.17 BOLT HOLES.
All holes for bolts shall be made by punching or drilling. Holes in all metal thicker than 3/4 inch (19 mm) for carbon steel and 5/8 inch (16 mm) for alloy steel shall not be made by punching, but shall be subdrilled and reamed or shall be drilled full size. Holes in main stress carrying members shall be subpunched and reamed, subdrilled and reamed, or drilled full size. Holes in other than a main stress carrying member in metal not thicker than 3/4 inch (19 mm) for carbon steel and 5/8 inch (16 mm) for alloy steel shall be punched or drilled full size.
When reaming is required all holes shall be subpunched or subdrilled. Subdrilling will be required if thickness limitations govern. The subpunching or subdrilling shall be 3/16 inch (5 mm) smaller and, after assembling, reamed 1/16 inch (2 mm) larger or drilled full size to 1/16 (2 mm) larger than the nominal diameter of the bolts.
All steel templates shall have hardened steel bushings in holes accurately dimensioned from the centerline of the connections as inscribed on the template. The centerline shall be used in accurately locating the template from the milled or scribed ends of the members.
A. Punched Holes.
The diameter of the die shall not exceed the diameter of the punch by more than 1/16 inch (2 mm). If any holes must be enlarged to admit the bolts, such holes shall be reamed. Holes must be clean cut without torn or ragged edges. The slightly conical hole that naturally results from punching operations is considered acceptable with the approval of the Engineer.
B. Reamed or Drilled Holes.
Reamed or drilled holes shall be cylindrical and perpendicular to the member. Where practical, reamers shall be directed by mechanical means. Reaming and drilling shall be done with twist drills, twist reamers or rotobroach cutters. Connecting parts requiring reamed or drilled holes shall be assembled and securely held while being reamed or drilled and shall be match marked before disassembling.
C. Accuracy of Holes.
Holes not more than 1/32 inch (1 mm) larger in diameter than the true decimal equivalent of the nominal diameter that may result from a drill or reamer of the nominal diameter are considered acceptable. The width of slotted holes, which are produced by flame cutting or a combination of drilling or punching and flame cutting, shall generally be not more than 1/32 inch (1 mm) greater than the nominal width. The flame cut surface shall be ground smooth.
D. Accuracy Before Reaming.
All holes subpunched or subdrilled shall be so accurate that after assembling (before any reaming is done) a cylindrical pin 1/8 inch (3 mm) smaller in diameter than the nominal size of the hole may be entered perpendicular to the face of the member, without drifting, in at least 75% of the contiguous holes in the same plane. If the requirement is not fulfilled, the badly subpunched/subdrilled pieces will be rejected. If any hole does not allow a pin 3/16 inch (5 mm) smaller in diameter than the nominal size of the subpunched/subdrilled hole to pass, it will be cause for rejection.
E. Accuracy After Reaming or Drilling.
When holes are reamed or drilled, 85% of the holes in any contiguous group shall, after reaming or drilling, show no offset greater than 1/32 inch (1 mm) between adjacent thicknesses of metal.
F. Misplaced Holes.
Misplaced holes may be a basis for rejection and shall be repaired only with the approval of the Engineer.
G. Removal of Burrs.
Burrs on outside or faying surfaces shall be removed. If required by the Engineer, assembled parts shall be taken apart for removal of burrs.
2408.18 REAMING SUBPUNCHED FIELD CONNECTIONS.
When subpunched and reamed holes are required for field connections, main members of the structure shall be fully assembled and firmly bolted together, and their members adjusted to line and fit before holes in connecting joints are reamed. Before the parts are disassembled for shipping and handling, the respective pieces shall be matchmarked with a low stress riser steel stamp so that they can be reassembled in the same position when the structure is erected in the field. Steel stamping on the edges of plates will not be permitted.
In lieu of subpunching and reaming holes, it is permissible, at the option of the fabricator, to drill holes full size while members are assembled by any of the following procedures:
A. By laying out the location of the holes on the outside plate with center punch marks and drilling full size, or
B. By subpunching holes in the outside plate and enlarging subpunched holes by drilling full size, and drilling full size through the remaining plates, or
C. By predrilling splice plates or plates full size and using these as a template to drill full size through the remaining plates.
The accuracy of drilled holes shall be as specified in Article 2408.17, Paragraph C.
Reamed parts shall not be interchanged. Connecting joints, such as floor beam and stringer connections not assembled as provided above, shall be reamed to a metal template.
2408.19 SHOP ASSEMBLY.
The various parts of the structure which are to be fastened together in the shop shall be assembled in accordance with the following:
If zinc silicate primer is to be used, surfaces which will be in contact shall be cleaned and shop painted before assembly, in accordance with the contract documents. If zinc silicate primer is not to be used, surfaces which will be in contact shall be carefully cleaned, free from loose mill scale, dirt, or other foreign material, but shall not be painted before assembly.
After assembly, all surfaces, except those against which plastic concrete will be placed, shall be painted and protected as provided in Article 2408.44 and the contract documents.
The members shall be free from objectionable twists, bends, or other deformations.
Members to be welded shall be brought into correct alignment and held in position by bolts, clamps, wedges, guylines, struts, tack welds, or other suitable devices, until welding has been completed. The use of jigs and fixtures is recommended where practicable. Suitable allowances shall be made for warpage and shrinkage.
2408.20 DRIFTING OF BOLT HOLES.
The drifting done during assembling shall be only to bring the parts into position and not sufficient to enlarge the holes or distort the metal.
2408.21 FACING BEARING SURFACES.
Ends of columns and pedestals shall be milled to true surfaces and correct bevels. Warped or deformed base and cap plates shall be planed to fit accurately.
Connection angles for base and cap plates shall be attached to columns before ends are faced. Milling shall be done only after the member has been fully assembled.
Bearing surfaces of warped or deformed base and cap plates that are not to be placed in contact with concrete shall be milled after the plates are attached to the column. Surfaces of base plates that are to be placed in contact with concrete shall be free from warps and other deformations.
Sole plates of beams, girders, and trusses shall have full contact with the flanges, and the bearing surface shall be smooth and true and shall be truly perpendicular to the web of the member. Curved sole plates shall make full line bearing with masonry plates, which line, unless otherwise shown in the contract documents, shall be at right angles to the axis of the beam, girder, or truss, and with the web of the member. Bottom surfaces of masonry plates shall be free from warps and projections. All bearing surfaces of castings are to be machined flat.
The tolerance for flatness for all bearing material in contact with all other material, except as otherwise indicated, shall be 1/32 inch in 12 inches and 1/16 inch (1 mm in 400 mm and 2 mm) tolerance overall.
The degree of surface finish required will be indicated in the contract documents. The surface finish of bearing and base plates and other bearing surfaces that are to come into contact with each other or with concrete shall meet the surface roughness requirements as defined in ANSI B46.1, Surface Roughness, Waviness and Lay, Part 1. Unless otherwise indicated on the plans, the following parts shall be finished to the degree indicated below:
Steel slabs including masonry plates and cast shoes in contact with concrete ANSI 2,000 (50 µm) Heavy plates in contact in shoes to be welded ANSI 1,000 (25 µm) Milled ends of compression members, stiffeners, and fillers ANSI 500 (12.5 µm) Bridge rollers, rockers, and top surfaces of masonry plates in contact with rollers and rockers ANSI 250 (6.25 µm) Pins and pinholes ANSI 125 (3.125 µm) Sliding bearings ANSI 125 (3.125 µm)
Surfaces of bronze bearing plates intended for sliding bearings shall be smooth and free from surface projections.
In machining sliding bearing surfaces, the cut of the tool shall be in the direction of movement. In machining nonsliding bearing surfaces, the cut of the tool shall be either parallel or normal to the direction of movement.
2408.22 ABUTTING JOINTS.
A. Ends of Compression Members.
Abutting ends of compression members shall be accurately faced after the members are assembled, to secure an even bearing when assembled in the structure.
B. Ends of Tension Members.
Ends of tension members shall be neatly sheared or cut at splices with openings not exceeding 1/4 inch (6 mm).
C. Splices of Continuous Beams and Girders.
Ends of beams and girders to be spliced shall be neatly sheared or cut, with a minimum opening of 1/8 inch (3 mm) and a maximum opening not exceeding 1/4 inch (6 mm) for rolled beam spans and 1/2 inch (13 mm) for plate girder spans. This dimension shall be detailed on the shop drawings.
2408.23 END CONNECTION ANGLES.
End connection angles of floor beams and stringers shall be flush with each other and accurately set to position and length of member. In general, end connection angles shall not be machined unless indicated in the contract documents. However, faulty assembling may be cause for requiring them to be milled, in which case their thickness shall not be reduced by more than 1/16 inch (2 mm) and their bolt bearing value shall not be reduced below the design requirements.
2408.24 BORING PIN HOLES.
Pin holes shall be bored true to detailed dimensions, smooth and straight at right angles with the axis of the member and parallel with each other, unless otherwise required. A finishing cut shall always be made, and the finish shall be in accordance with Article 2408.21.
The length outside to outside of holes in tension members and inside to inside of holes in compression members shall not vary from detailed dimensions more than 1/32 inch (1 mm). Boring of holes in built up members shall be done after the bolting or welding is completed.
2408.25 PIN CLEARANCE.
The diameter of the pin hole shall not exceed that of the pin by more than 1/50 inch (0.5 mm) for pins 5 inches (125 mm) or less in diameter, or 1/32 inch (0.8 mm) for larger pins.
2408.26 FINISHED MEMBERS.
The several pieces forming one built up member shall be straight and close fitting. Finished members shall be true to detailed dimensions and free from twists, bends, open joints, or other defects resulting from faulty fabrication or defective work.
2408.27 SHOP ERECTION.
The main members of trusses, arches, continuous beam spans, bents, towers (each face), plate girders, and rigid frames shall be completely assembled for inspection in the shop when complete assembly is feasible. In lieu of complete assembly, at the option of the Contractor, progressive truss or girder assembly will be permissible, as follows:
A. Initially for each truss, arch rib, bent, tower face, or rigid frame, at least three contiguous shop sections shall be assembled, or all members in at least three contiguous panels, but not less than the number of panels associated with three contiguous chord lengths (i.e., length between field splices) and not less than 150 feet (45 m), shall be assembled in the case of structures longer than 150 feet (45 m). In order that the assembled portion of the structure is never less than that specified above, each laydown shall be composed of a sufficient number of sections or chord lengths so that the assembled portion will remain long enough when the rearward section or chord is removed after inspection of the laydown. At the option of the Contractor, the portion of the structure which is retained may be disassembled and reassembled in a new location for the new laydown.
B. Initially for each continuous beam or plate girder line, at least three contiguous shop sections shall be assembled, but in the case of structures larger than 150 feet (45 m), not less than 150 feet (45 m) of structure shall be assembled. Each succeeding laydown shall be accomplished in such a manner that at least one contiguous section shall be retained from the previous laydown and not less than 150 feet (45 m) of structure shall be assembled, except that the last laydown in a line may be less than 150 feet (45 m) long. At the option of the Contractor, the portion of the structure which is retained may be disassembled and reassembled in a new location for the new laydown.
As the shop sections are progressively assembled and removed, each retained section shall be placed in the new laydown with the same relative orientation to the erection base line as it was found to have in the previous laydown.
As the shop sections are progressively assembled and removed, suitable marks shall be scribed on the sections remaining so that accurate center to center of bearing dimensions and overall length can be achieved.
2408.28 PILOT AND DRIVING NUTS.
On pin connected spans, pilot and driving nuts shall be furnished for each size pin unless otherwise provided in the contract documents.
2408.29 MILL AND SHOP INSPECTION.
The Contractor shall give the Engineer ample notice of the beginning of work at the mill and shop so that inspection may be provided. Mill inspection of rolling will not be required unless requested by the Engineer. If inspection of rolling is not requested, the Engineer shall be furnished with complete test reports of mill inspections, showing chemical and physical tests for each heat of all structural steel sections as specified in Articles 2408.04 and 4152.02.
Material shall not be fabricated before the Engineer has been notified.
A. Inspector's Authority.
The inspector shall have the authority to reject material or work which does not fulfill the requirements of these specifications; but, in cases of dispute, the Contractor may appeal to the Engineer, whose decision shall be final.
Inspection at the mill and shop is intended as a means of facilitating the work and avoiding errors, and it is expressly understood that it will not relieve the Contractor from any responsibility in regard to imperfect material or quality of work and the necessity for replacing the same.
B. Facilities for Inspection.
Facilities for inspection shall be furnished by the Contractor for inspection of material and workmanship in the mill and shop, and inspectors shall be allowed free access to necessary parts of the premises.
C. Mill Orders and Shipping Statements.
The Contractor shall furnish the Engineer with as many copies of mill orders and shipping statements as may be requested. The weights (mass) of individual members shall be shown.
Approval of any material or finished members will not be a bar to their subsequent rejection, if found defective. Rejected material and work shall be replaced or made good by the Contractor promptly.
2408.30 SHOP PAINTING.
This specification describes surface preparation and shop painting of weathering and non-weathering structural steel and incidental parts. The work includes preparation of all surfaces to be painted, application of paint, protection, drying of paint coatings, and repairing and repainting of coating damaged in the shop and/or after erection. This specification also includes requirements for water washing of weathering structural steel.
A. Surface Preparation.
All steel surfaces to be painted shall be given a near white metal blast cleaning in accordance with SSPC-SP10. Bearing assemblies shall be cleaned of any surface contamination using suitable solvents in accordance with SSPC-SP1 and then given a near white metal blast cleaning in accordance with SSPC-SP10. SSPC-VIS 1, Visual Standard for Abrasive Blast Cleaned Steel, will be used as the standard for acceptance of the surface preparation.
Machined surfaces designated in the contract documents to have a surface roughness of ANSI 125 (3.125 µm) or less shall not be blast cleaned. Masking or other protection will be required if these parts are subjected to the blast cleaning process.
The abrasive used shall be clean, dry, and free from organic contamination. After blasting, the surface to be painted shall be thoroughly cleaned with dry, oil free, compressed air to remove all blast residue.
A sharp, angular blast profile of a minimum 1 mil (25 µm) and maximum 3 mils (75 µm) shall be achieved on all surfaces including thermal cut edges. When shot is used for blasting, the blast media shall contain at least 10% steel grit.
1. Non-weathering Structural Steel Applications.
All oily or greasy residues shall be removed with solvent in accordance with SSPC-SP1, Solvent Cleaning, before the top coat is applied. All surfaces to be top coated shall in accordance with the specification requirements and dry.
2. Weathering Structural Steel Applications.
For weathering structural steel applications, surfaces not requiring painting shall be given a Commercial Blast in accordance with specification SSPC-SP6.
To ensure uniform weathering all unpainted areas of outside surfaces of the facia girders shall receive, after blasting, at least three uniform applications of water mist at 24 hour interval between applications. Each application shall be applied on dry surfaces. The water mist application shall be performed within 48 hours after the painted surfaces have been properly cured. All water mist application shall be witnessed by a representative of the Contracting Authority.
Shop painting shall be done only in a facility approved by AISC, SSPC, or the Engineer and only painters who are trained and certified by an independent outside agency for the type of work performed shall apply the paint.
The paint manufacturer's application recommendations shall be followed regarding mixing, thinning, application, pot life, steel temperature, and weather conditions. The painted areas shall have a smooth uniform, adhering coat; free of over-spray, dry spray, mud cracking, runs, sags, cracks, holidays, or other defects. Prior to painting, all surfaces shall be free of all moisture, dirt, oxidation products, oil, and other detrimental material, and shall be of a suitable temperature in accordance with the manufacturer's recommendations.
Machined surfaces with small clearances between moving components, such as full circle pins and pin holes, partial circle pins and pin recesses in castings, and similar surfaces, shall not be painted. These surfaces shall be shop coated with an application of waterproof multipurpose grease, complying with National Lubricating Grease Institute No. 3 or other approved protective coating. The protective coating shall be applied as soon as practical after component parts have been machined, welded if required, and blasted. Machined surfaces shall be thoroughly cleaned before applying the grease.
Before erection machined surfaces shall be wiped clean and given another application of grease.
1. Non-weathering Structural Steel Applications.
The prime coat and topcoat paints shall be manufactured by the same company. All painted surfaces shall be protected to prevent soiling during painting and through the tack-free stage. Care shall be taken to not damage the paint system during handling, delivery, storage, and erection of the structural steel. Damage to the prime coat attributable to shop activities shall be repaired in accordance with the paint manufacturer's recommendations before shipment to the field. Damage to the topcoat shall be repaired in accordance with manufacturer's recommendations.
All structural steel surfaces including faying surfaces of high strength bolt connections shall receive a shop applied prime coat. Also all bearing assemblies, except galvanized masonry plates and galvanized swedged bolts unless otherwise specified in the plans, shall receive a shop applied prime coat.
a. Shear Studs.
When shear studs are welded to the top of the top flange of a beam or girder after the paint system is applied, the paint shall be ground off in the areas of the weld to facilitate welding. After welding, touch-up on the top flange is not required, however, paint damage on the underside of the top flange shall be repaired.
b. Prime Coat.
All the surfaces to be painted shall be given a coat of zinc silicate paint as soon as possible after blasting before formation of any surface rust and not later than 16 hours after blasting the surface. Approved paints are shown in Materials I.M. 482.02, Appendix A. The target average dry film thickness shall be 4 mils (100 µm) with no spot measurement below 3 mils (75 µm) or above 6 mils (150 µm). Any repairs or build-up of the paint film shall be done as soon as possible and not later than 24 hours from the initial application. Steel members with coating areas measuring less than 3 mils (75 µm) that have not been corrected within 24 hours shall be completely reblasted and repainted. All defects in application such as runs, sags, mud cracking, over spray, and dry spray shall be corrected to the satisfaction of the Engineer.
Excessive coating thickness is as equally undesirable as unacceptably thin coating thickness, and both will be sufficient cause for rejection. Excessive thickness will be evaluated on a case-by-case basis in consultation with the coating manufacturer.
The inorganic zinc silicate paint film will be considered cured and ready for shipment after achieving a resistance rating of 4 as verified by 50 Methyl Ethyl Ketone (MEK) rubs as per ASTM D 4752. Moisture misting and plastic tenting maybe required during cold application temperatures and low relative humidity conditions to aid in prime coat curing.
c. Top Coat.
When designated by the contract documents, a topcoat of waterborne acrylic paint shall be shop applied to all primed surfaces. The galvanized fasteners shall be painted in accordance with Article 2408.30, B, 1, d after bolting. It is recommended that application be initiated with a mist coat applied prior to full coat application. To avoid moisture condensation, top coat shall be kept under a roof, protected from dirt, dust, and moisture, in an area where the temperature is maintained above 40°F (5°C) for a minimum 24 hours after painting is completed.
Concrete at all junction points of concrete and steel shall be shielded so that application of paint on steel is complete without over-spray on the concrete.
Approved paints are listed in Materials I.M. 482.05, Appendix A. The dry film thickness of the top coat shall be a minimum of 2 mils (50 µm). The topcoat color shall be Iowa standard foliage green Federal Color Standard Number 14223 unless otherwise specified in the contract documents.
d. Field Repair and Painting.
Paint damage due to transportation, handling, or construction activities shall be repaired and repainted by the Contractor after erection. An approved zinc rich epoxy paint, listed in Materials I.M. 482.02, Appendix C, shall be used for repair of the primer, priming un-galvanized fasteners, and any coating damage to galvanized fasteners.
Areas to be repaired and repainted shall be clean, dry, and free from grease, oil, corrosion products, and other detrimental materials. Paint shall not be applied to surfaces unless they are free from moisture or frost. The paint manufacturer's recommendations shall be followed for all aspects of repair.
When designated by the contract documents a field applied waterborne acrylic topcoat will be included.
e. Cleaning of Paint Surfaces.
Upon completion of concrete placement, exposed structural steel surfaces shall be cleaned to remove all concrete and latence before the concrete sets-up.
2. Weathering Structural Steel Applications.
All the surfaces to be painted shall be given a coat of zinc silicate paint as soon as possible after blasting before formation of any surface rust and not later than 16 hours after blasting the surface. Approved paints are shown in Materials I.M. 482.02, Appendix A. The minimum average dry film thickness shall be 4 mils (100 µm) with no spot measurement below 3 mils (75 µm) or above 6 mils (150 µm). Any repairs or build up to the applied prime coat shall be done as soon as possible and not later than 24 hours from the initial application. After the primer has cured to a resistance rating of 4 as verified by 50 MEK rubs as per ASTM D 4752 the primed surfaces shall be given a top coat of waterborne acrylic paint from the approved list shown in Materials I.M. 482.05, Appendix A. The top coat color shall match Federal Color Standard Number 20045. The top coat shall cover all the primed surfaces except faying surfaces of bolted joints with a uniform film of paint. The top coat shall be applied in the shop unless permitted in writing by the Engineer.
The following areas shall be painted:
a. All the weathering steel for a distance of 1.5 times the girder depth on each side of the expansion joints.
b. All the bearing assemblies except galvanized masonry plates and galvanized swedged bolts unless otherwise specified in the plans.
c. Embedded girder ends over the entire embedment length plus an additional distance of 1.0 foot (300 mm). The crevice between the embedded steel and concrete shall be sealed by caulking with a neutral cure and non-sag silicone. Two products meeting these criteria are Dow 888 or CSL 342 joint seal.
d. 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 as noted in this specification.
After erection of the bridge, all fasteners in the painted areas shall be prepared using suitable hand tools, mechanical tools, or blasting equipment, and primed with a zinc rich epoxy paint from the approved list shown in Materials I.M. 482.02, Appendix C. The primed surfaces shall be cleaned and given a top coat of waterborne acrylic paint from the approved list shown in Materials I.M. 482.05, Appendix A. The color of the top coat shall match Federal Color Standard Number 30045.
Any defect or damage to the paint system after completing construction shall be prepared and repainted.
All steel surfaces shall be free of contaminants including dirt or concrete.
2408.31 MARKING AND SHIPPING.
Bolts of one length and diameter and loose nuts or washers of each size shall be packed separately. Items from different manufacturers or from different lots shall also be packaged separately. Pins, small parts, and small packages of bolts, washers, and nuts shall be shipped in boxes, crates, kegs, or barrels, but the gross weight (mass) of any package shall not exceed 300 pounds (135 kg). A list and description of the contained material shall be plainly marked on the outside of the shipping container.
2408.32 FIELD HANDLING AND STORAGE.
Loading, transportation, unloading, and piling of structural members shall be conducted so that the metal will be kept clean and free from damage by rough handling. Shipping supports, lifting devices, and deck form support points shall be padded to minimize paint damage.
All material shall be stored in a manner to prevent deterioration by rust or loss of minor parts. Material shall not be piled to rest upon the ground or in water, but must be placed on suitable skids or platforms. Girders and beams shall be placed upright and shored. Skids beneath long members, such as columns or chords, shall be close enough to prevent damaging the members by deflection.
Detailed plans for falsework or centering shall be supplied in accordance with Article 1105.03. In no case shall the Contractor be relieved of responsibility for results obtained by use of these plans or safety of workers on the project. Adequacy of falsework shall be subject to checking and review by the Engineer before erection of the structure which the falsework is to carry. Falsework for supporting steel during erection shall be designed to carry, without appreciable settlement or deformation, the full load coming upon it. It shall consist of either full length pile bents or framed bents supported by piles or spread footings. Bearing values of piles shall be determined as provided in Article 2501.14 and shall be at least equal to the loads imposed upon them during construction. The number and size of spread footings or mudsills used shall be determined by the load to be supported and the bearing value of the soil on which they rest, due consideration being given to the softening of soils during high water, thawing of frozen ground, etc. Mudsills shall not be used on soils or in situations where scour is likely to occur.
The safe bearing value of sand, gravel, firm clay, and other similar confined materials in beds thicker than the falsework footing width shall be considered 1,500 pounds per square foot (70 kPa).
If necessary to extend falsework above the elevation to which piles are driven, at least the majority of all piles in any bent shall be cut off at the same elevation and capped, and a framed bent shall be constructed to the required height. Each falsework bent shall be capped transversely at the proper elevation with material of adequate size securely fastened to each pile or post in the bent. All bents shall be securely braced longitudinally and transversely with diagonal bracing.
2408.34 PREPARATION OF BEARING AREA.
Column bases, truss and girder pedestals, and shoes shall have a full uniform bearing upon the concrete of the substructure. Bridge seats of piers or abutments which are improperly finished, deformed, or irregular within the bearing area of masonry plates shall be corrected before the plates are placed. Pedestals and shoes for truss and girder spans and columns for steel viaducts shall be bedded on the bearing area so as to have full and even bearing. Unless otherwise required, the bedding shall be a single layer of 1/8 inch (3 mm) sheet lead meeting requirements in Article 4195.01.
2408.35 HANDLING MEMBERS.
Component parts of a structure shall be handled by methods and appliances not likely to produce damage to the member by twisting, bending, or otherwise deforming the metal. Any member that is slightly bent or twisted shall not be put into its place until its defects are corrected. Members that have been seriously damaged in handling may be rejected.
2408.36 STRAIGHTENING BENT MATERIAL.
Straightening of plates, angles, other shapes, and built up members, when permitted by the Engineer, shall be done by methods that will not produce fracture or other injury. Distorted members shall be straightened by mechanical means, or if approved by the Engineer, by the carefully planned and supervised application of a limited amount of localized heat, except that heat straightening of ASTM A 709/A 709M Grade 100/100W (Grade 690/690W) steel members shall be done only under rigidly controlled procedures, each application subject to approval of the Engineer. In no case shall the maximum temperature of ASTM A 709/A 709M Grade 100/100W (Grade 690/690W) steel exceed 1,125°F (610°C), nor shall the temperature exceed 950°F (510°C) at the weld metal or within 6 inches (150 mm) of weld metal. Heat shall not be applied directly on weld metal. In all other steels, the temperature of the heated area shall not exceed 1,200°F (610°C) (a dull red) as controlled by use of temperature indicating crayons, liquids, or bimetal thermometers.
Parts to be heat straightened shall be substantially free of stress and from external forces, except stresses resulting from mechanical means used in conjunction with the application of heat.
Following straightening of a bend or buckle, the metal surface shall be carefully inspected for evidence of fracture. Members showing fracture shall be repaired or replaced.
2408.37 ASSEMBLING STEEL.
Parts shall be accurately assembled as shown in the contract documents and a match marking system shall be followed. Material shall be carefully handled so that parts will not be bent, broken, or otherwise damaged. Hammering which will damage or distort the members shall not be done. Bearing surfaces and surfaces to be in permanent contact shall be cleaned before the members are assembled.
Important connections in trusses, girders, floor systems, etc., shall have at least 25% of the holes on each side of the connection filled with drift pins, and another 25% of the holes on each side of the connection filled with temporary fitting up bolts drawn up snugly before the temporary support is removed. If the ultimate connection is to be made with high strength bolts, these bolts may be used as fitting up bolts. At milled connections of compression chords of truss spans, except the hip connection, the number of drift pins may be reduced to not less than 10% of the number of holes.
Before placing permanent bolts in field connections, the structure shall be adjusted to correct grade and alignment. For truss spans, the elevation of each panel point (ends of floor beams) shall be blocked up on the falsework to the correct camber as shown in the contract documents and shop drawings. This blocking shall remain in place until all tension chord splices are fully bolted and all other truss connections are pinned and bolted.
Splice joints of continuous beams and girders shall be supported by adequate falsework or other approved means as directed by the Engineer, and adjusted as closely as possible to the required position before bolting is started.
Main connections shall be made with high strength bolts, nuts, and washers meeting requirements of Article 4153.06. All other fasteners will be considered non-high strength fasteners and may be used only where shown on the plans.
A. Length of Bolts.
The length of high strength bolts shall be such that, when properly installed in a snug tight condition, the end of the bolt will be flush with or outside the face of the nut.
The length of non-high strength bolts shall be such that, when tightened, there will be not less than 1/4 inch (6 mm) of bolt protruding from the nut.
The length of turned bolts shall be such that when the nut is fully threaded there will not be more than 1/8 inch (3 mm) of thread within the thickness of metal to be gripped and not more than 1/4 inch (6 mm) of thread protruding from the nut.
Ribbed bolts shall be furnished in a variety of diameters and lengths that, when installed, will result in a drive tight fit and when tightened, will fill the nut and protrude not more than 3/16 inch (5 mm).
B. Bolt Holes.
Holes for non-high strength and high strength bolts shall permit free entry of the bolt without driving. Holes for ribbed bolts shall be carefully reamed to provide for a driving fit. Holes shall be cylindrical and shall permit entry of the bolts at right angles to the faying surfaces.
C. Storage of High Strength Fasteners.
Special care shall be taken to ensure that bolts, nuts, and washers are properly protected from the elements.
D. Fastener Acceptance Testing.
Prior to steel erection the Contractor shall test, in the presence of the Engineer, two representative fastener assemblies from each rotational-capacity test lot as described in Materials I.M. 453.06B. A fastener assembly shall consist of a bolt, nut, and washer from the same rotational-city lot as furnished by the supplier. Additional rotational-capacity tests may be ordered by the Engineer if there is reason to suspect any change in fastener condition or level of lubrication. Failure of rotational-capacity tests will be cause for rejection of that fastener lot.
E. Installing High Strength Fasteners.
High strength fasteners shall be assembled, tensioned, and inspected as described below. In special cases other methods may be used with prior approval of the Engineer.
Surfaces of bolted parts adjacent to the bolt head and nuts shall be parallel. Bolted parts shall fit solidly together when assembled, without containing gaskets or any other flexible material. Holes shall not be more than 1/16 inch (2 mm) in diameter greater than the nominal bolt diameter. For slotted holes, the dimensions will be shown on the plans or shop drawings.
For painted applications, the faying surfaces shall be cleaned and primed with zinc silicate paint. For unpainted applications, faying surfaces shall be blast cleaned to remove mill scale, and be free from paint, lacquer, dirt, oil, burrs, pits, or other defects which would prevent the solid seating of parts or would interfere with the development of friction between parts.
The fastener assembly installed in the field shall be made up of bolts, nuts, and washers from the same rotational-capacity lot number. Fasteners shall be assembled with one hardened washer under the turned element (either bolt head or nut). When fasteners are specified to be galvanized, the nuts shall be furnished pre-lubricated with a dyed lubricant in accordance with ASTM A 563, or fastener threads shall be field lubricated with beeswax or other approved wax based lubricant.
For weathering structural steel, high strength weathering fasteners shall be used. For non-weathering structural steel, with or without a specified field top coat, galvanized high strength fasteners shall be used.
Each fastener, when properly tightened, shall have at least the following minimum bolt tension:
MINIMUM BOLT TENSION Bolt Dia.
1 1/8 (28.6)
1 1/4 (31.8)
1 3/8 (34.9)
1 1/2 (38.1)
* Equal to the proof load (length measurement method) given in ASTM A 325.
High strength bolts shall be tightened by the turn-of-nut method.
Impact wrenches, if used, shall be of adequate capacity and sufficiently supplied with air to develop the minimum tension of each bolt in approximately 10 seconds.
2. Turn-of-Nut Method.
The turn-of-nut method shall be used to provide the minimum bolt tension specified above.
Bolts shall be installed in all holes of the connection and brought to a "snug tight" condition. Bolts shall be considered "snug tight" when tensioned to approximately 20% of the minimum bolt tension listed above and faying surfaces are in full contact. If full contact of faying surfaces is not achieved after all bolts have been tensioned to 20% of minimum tension, the Contractor shall submit a corrective procedure to the Engineer for approval.
Snug tightening shall progress systematically from the center of the connection to the free edges. The fasteners of the connection shall be checked in similar systematic manner and retightened as necessary until all fasteners are simultaneously in a "snug tight" condition and the faying surfaces are in full and continuous contact.
When all fasteners in the connection are "snug tight", the face of the connecting part, the nut, and the bolt point shall be match-marked using paint, crayon, or other approved means to provide a reference for determining the relative rotation of the parts during final tightening.
Following this operation, all fasteners in the connection shall be tightened further by the applicable amount of rotation specified in the following table. Tightening shall progress systematically from the center of the joint to the free edges. During this operation, there shall be no rotation of the part not turned by the wrench.
NUT ROTATION FROM "SNUG TIGHT" CONDITION (*)
Disposition of Outer Faces of Bolted Connections
Bolt Length (Under side of head to end of bolt) Both Faces normal to bolt axis One face normal to bolt axis and other slope not more than 1:20 (beveled washer not used) Both faces sloped not more than 1:20 from normal to the bolt axis (beveled washers not used) Up to and including 4 diameters 1/3 turn 1/2 turn 2/3 turn Over 4 diameters but not exceeding 8 diameters 1/2 turn 2/3 turn 5/6 turn Over 8 diameters but not exceeding 12 diameters ** 2/3 turn 5/6 turn 1 turn (*) Nut rotation shall be relative to the bolt, regardless of the element (nut or bolt) being turned. For bolts installed using 1/2 turn and less, the tolerance shall be ± 30 degrees. For bolts installed using 2/3 turn and more, the tolerance shall be ± 45 degrees. (**) For bolt lengths exceeding 12 diameters, the required rotation must be determined by actual field tests in a suitable tension measuring device which simulates conditions of solidly fitted steel.
The Contractor shall check the bolted connections, after tightening, in the presence of the Engineer for proper installation, applicable rotation, and general joint condition. The inspection of fasteners, with a torque wrench, at connections of steel diaphragms to concrete beams will not be required.
The Contractor shall furnish and use an inspecting wrench, which shall be calibrated and capable of measuring torque.
To calibrate the inspecting wrench, a representative sample of not less than three bolts and nuts of each diameter, length, grade, and turned element, to be tensioned that day, shall be checked prior to inspection in a device capable of indicating bolt tension. The element turned during testing shall be the same element turned during actual work. The inspecting wrench shall then be used to tension the bolt and determine the torque necessary to achieve a bolt tension 5% greater than the specified minimum bolt tension. The average of the three torque values shall be the job inspecting torque value(s). The job inspecting torque value(s) shall be established at least once prior to each day's inspection. The tension measuring device shall be calibrated by an approved testing agency at least every 6 months.
Installed and tightened fasteners represented by the above tests shall be inspected for acceptance by attempting to tighten the fastener using the inspection torque wrench and the predetermined inspection torque value(s). Acceptance will be based on the random checking of at least 10% of the fasteners in each connection, with a minimum of two fasteners checked per connection. If the faying surfaces are in full and continuous contact and no bolt or nut is turned at a torque value less than or equal to the inspection torque value(s), the connection will be accepted as properly tightened.
If any bolt or nut is turned at torque values below the inspection torque value(s), all fasteners in that connection shall be checked. All bolts or nuts which turn below inspection torque values shall be tightened and reinspected.
Bolts tightened by the turn-of-nut method may reach tensions substantially above the values specified, but this shall not be cause for rejection.
4. Reuse of Bolts.
High strength bolts and nuts shall not be reused. Construction bolts or fit-up bolts shall not be incorporated into the final connection. Tensioning of fasteners up to a snug-tight condition as described in Paragraph E, 2 above, will not be considered as reuse. Retightening (touching up) previously tightened bolts which may have been loosened by the tightening of adjacent bolts will not be considered as reuse.
2408.40 SWINGING THE SPAN.
After permanent bolting of truss spans has been inspected and accepted, the centering shall be removed and the span swung free on its permanent supports. All main connections shall be fully bolted before the span is swung, except that milled compression chord connections shall be permanently bolted after the span is swung.
2408.41 ADJUSTMENT OF PIN NUTS.
All nuts on pins shall be adjusted to the amount specified in the contract documents. The pins shall be located in the holes so that the members shall take full and even bearing upon them.
2408.42 SETTING ANCHOR BOLTS.
For setting anchor bolts for bridge bearings, see Article 2405.09.
Anchor bolts, other than those for bridge bearings, shall be set in concrete with a polymer grout, as described in Article 2405.09, or with a mechanical grip system. When the mechanical grip system is used, the diameter of the hole shall be suitable for the device used, the anchor shall be held firmly in place by an expanding metal device approved by the Engineer, and the annular space shall be filled with cement grout or other material approved by the Engineer.
2408.43 SETTING ROCKER BEARINGS.
Rocker bearings at expansion ends of spans shall be adjusted to provide for movement due to temperature, for elongation of bottom chord, and for probable substructure movement. The mean temperature assumed shall be 50°F (10°C), in determining temperature movements.
2408.44 FIELD PAINTING.
Field painting of steel structures or parts of structures shall be as required in the contract documents.
2408.45 METHOD OF MEASUREMENT.
The quantity of various items of structural concrete, steel reinforcement, structural steel, and incidental metal parts, involved in construction of steel structures will be computed by the Engineer as follows:
A. Structural Concrete.
Article 2403.22 shall apply.
B. Steel Reinforcement.
Article 2404.09 shall apply.
C. Structural Steel and Incidental Metal Parts.
1. Structural Steel.
The weight (mass) of structural steel measured for payment shall include the weight (mass) of all rolled shapes and plates, as fabricated, and the weight (mass) of incidental parts, such as castings, bearing plates, expansion devices, bolts, and incidental metal parts necessary for completion of the structure. Unless the contract contains a separate item for metal railings, material for such railings shall be included with structural steel. Incidental materials, such as bronze, wrought iron, lead, castings, etc., shall be classed as structural steel unless covered by a separate item in the contract.
Reinforcement for concrete is not included in this item.
2. Weight (Mass).
The weight (mass) of structural steel as defined above, for which payment will be made, shall be the weight (mass) in pounds (kilograms) computed by the Engineer as shown in the contract documents. In the case of a substitution, by the Contractor, of a heavier section than that shown, the weight (mass) of the section shown in the contract documents shall be the measured quantity.
The weight (mass) of structural steel, computed by the Engineer and shown in the contract documents, shall be presumed to be correct and shall provide the basis of payment; however, if the Contractor presents evidence that the weight (mass) computed by the Engineer is in error by more than 0.50%, the weight (mass) will be recomputed.
3. Variation in Weight (Mass).
If the weight (mass) of any member is less than 97.5% of the computed weight (mass), such member may be rejected.
4. Computed Weight (Mass).
The Engineer will compute the weight (mass) of structural steel on the basis of the following assumptions:
Steel 490 pounds per cubic foot (7850 kg/m3)
Cast Iron 450 pounds per cubic foot (7210 kg/m3)
The weight (mass) of rolled shapes and plates shall be computed on the basis of their nominal weights (mass) and dimensions as shown in the contract documents, deducting for copes and cuts.
The weight (mass) of welds shall be included in the computed weight (mass), assuming the weights (mass) of fillet welds to be used as follows:
WEIGHT (MASS) OF WELDS Size of Weld
Wt. Per Linear Ft., lb.
(Mass per Meter), (kg)
Size of Weld
Wt. Per Linear Ft., lb.
(Mass per Meter), (kg)
The weight (mass) of heads, nuts, single washers, and threaded stick through of all high strength shop bolts shall be included in the computed weight (mass) on the basis of the following weights (mass):
WEIGHT (MASS) OF BOLTS Dia. of Bolt
Wt. Per 100 Bolts, lb.
(Mass per 100 Bolts), (kg)
Dia. of Bolt
Wt. Per 100 Bolts, lb.
(Mass per 100 Bolts), (kg)
1 1/8 (28.6)
1 1/4 (31.8)
1 3/8 (34.9)
1 1/2 (38.1)
The computed weight (mass) shall include the total weight (mass) of field bolts as specified in Article 2408.05 and the total weight (mass) of all shims required to be furnished for incorporation into the structure.
The weight (mass) of castings shall be computed from the dimensions shown in the contract documents with an addition of 5% for fillets and overrun.
D. Surface Preparation and Painting Structural Steel.
Surface preparation and painting structural steel will not be measured.
2408.46 BASIS OF PAYMENT.
The Contractor will be paid for various items of Structural Concrete, Steel Reinforcement, Structural Steel, and Incidental Metal Parts as follows:
A. Structural Concrete
Article 2403.23 shall apply.
B. Steel Reinforcement
Article 2404.10 shall apply.
C. Structural Steel and Incidental Parts
Steel structures will be paid for at the contract unit price per pound (kilogram) or lump sum for metal railing and structural steel. These payments shall be full compensation for furnishing all materials; preparation, including fabrication, nondestructive testing and inspection required by the contract documents, transportation, and erection; furnishing all labor; equipment; incidentals to complete the structure including the surface preparation and painting of the completed structure; and the repair and cleaning of the paint at the shop and after erection.