4-54 Modified __" Prestressed Concrete Girders will be measured and paid as the number of linear
feet of Modified Bulb- Tee prestressed concrete girders estimated in the plan s as being necessary to complete the project. FIB __" Prestressed Concrete Girders will be measured and paid as the number of line ar feet of Florida I -Beam prestressed concrete girders estimated in the plan s as being necessary to complete the project. 3'-0" x __'-__" Prestressed Concrete Cored Slabs will be measured and paid as the number of linear feet of prestressed concrete cored slabs estimated in the plan s as being neces sary to complete the project. 3'-0" x __'-__" Prestressed Concrete Box Beams will be measured and paid as the number of linear feet of prestressed concrete box beams estimated in the plan s as being necessary to complete the project. Elastomeric Bearings will be paid at the contract lump sum price. These prices and payments will be full compensation for al l items required to erect prestressed concrete members, including , but not limited to, those items contained in Article 430-1. Payment will be made under: Pay Item Pay Unit __" Prestressed Concrete Girders Linear Foot Modified __" Prestressed Concrete G irders Linear Foot FIB __" Prestressed Concrete Girders Linear Foot 3'-0" x __'-__" Prestressed Concrete Cored Slabs Linear Foot 3'-0" x __ '-__" Prestressed Concrete Box Beams Linear Foot Elastomeric Bearings Lump Sum
440-1 Description
Construct steel structures and steel structure portions of composite structures in conformity with the lines, grades and dimensions shown in the plan s and as specified in the specification s. Furnish, fabricate, galvanize, deliver, place, erect, clean, shop paint and field paint structural metals and all other materials; furnish, erect and remove falsework; set bearings and anchorage; weld and furnish all materials for and assemble all structural joints. Structural metals include structural steels, metallic electrodes, steel forgings and castings, gray iron and malleable iron castings, drain pipes and any incidental metal construction. Before starting work, inform the Engineer as to the proposed method of erection.
440-2 Materials
Refer to Division 10. Item Section Anchor Bolts 1072 -4 Bearing Plate Assemblies 1072 -3 Elastomeric Bearings 1079 -2 High Strength Bolts, Nuts, Washers and Direct Tension Indicators 1072 -5 Organic Zinc Repair Paint 1080 -7 Preformed Bearing Pads 1079 -1 Steel Pipe 1074 -6 Structural Steel 1072 Welded Stud Shear Connectors 1072 -6
4-55 440-3 Handling and Storing Materials
Move, handle and store all structural steel, in the shop, in the field and while being transported in accordance with Article 1072 -9.
440-4 Bearings and Ancho Rages
Supply preformed bearing pads and elastomeric bearings, as required by the plans and in accordance with Section 1079. Set steel masonry plates level in exact position with full and even bearing on the preformed bearing pad. Accurately set anchor bolt s in accordance with Subarticle 420 -12(A). Make sure that the location of anchors and setting of bearings take into account any variation from mean temperature at time of setting and anticipated lengthening of bottom flange due to dead load after setting, so at mean temperature and under full dead load the bearings are in a vertical position and anchor bolts at expansion bearings center in their slots. Mean temperature is 60 °F unless otherwise stipulated in the plan s. Do not restrict full and free movemen t of the superstructure at the movable bearings by improperly setting or adjusting bearings or anchor bolts and nuts.
440-5 Straightening Bent Material, Heat Curving and Heat
CAMBERING Straighten bent material, heat curve and heat camber as approved and in accordance with
Article 1072 — 10.
440-6 Field Erection
The Contractor is responsible for the safe erection of steel girders, diaphragms, and cross - frames, including the structural adequacy and stability of the bridge system during all phases of erection. Girders shall be stabilized with falsework, temporary b racing, holding cranes, or a combination thereof until a sufficient number of adjacent girders are erected with diaphragms or cross -frames connected to provide necessary local and global stability, and make the structure self -supporting. When required in the contract documents, the Contractor shall submit Erection Plans and Procedures, including associated Erection Engineering Calculations to the Department for review and approval. Report immediately any error in the shop fabrication or deformation resul ting from handling and transporting, which prevents the proper assembling and fitting up of parts by more than the moderate use of drift pins or by more than a moderate amount of reaming, chipping or cutting. Correct errors in the presence of the Engineer by approved methods. Do not perform hammering which injures or distorts the members. Before assembling the members, clean and dry to touch all bearing surfaces and permanently contacting surfaces. For bolted splices and field connections, initially fill 50 percent of the holes with a combination of erection bolts and full size erection pins but at least half (25% of the holes) shall be bolts . Sufficient pins shall be used near outside corners of splice plates, at member ends near splice plate edges, and in corners of diaphragm or cross -frame connections to ensure proper vertical and horizontal alignment. Filled holes shall be uniformly distributed between the web and flange connections such that approximately 50 percent of the web connections are filled and approximately 50 percent of the flange connections are filled. For diaphragms or cross -frames, the filled holes should be uniformly distributed between all the bolt groups connecting the diaphragm or cross -frame to the primary member . Ensure all splices are brought to the correct elevations before permanent fastening. For bolted connections use erection bolts with the same nominal diameter as the permanent fasteners, and use cylindrical erection pins which are 1/32 inch larger. Use permanent bolts as erection bolts if desired. Do not reuse permanent bolts for
4-56 final installation unless the nut is easily turned onto the bolt for the full threaded length by hand
and without the use of tools . Permanent bolts shall be installed in all the remaining holes of the connection and the entire connection brought to a snug condition prior to permanent tensioning or crane release. Snug tight is defined as being attained after a few impacts of an impact wrench or the full effort of an ironworker with an ordinary spud wrench. Snugging shall progre ss systematically from the most rigid part of the connection to the free edges. After all bolts have been snugged, every bolt in the connection should be revisited and resnugged if necessary, since snugging of an adjacent bolt may relieve tension on an ea rlier snugged bolt. As an option, fully tensioned temporary fit up bolts may be used to help bring the plies in full contact prior to permanent fastening. The requirement for 100% connection prior to crane release may be reduced if calculations submitted with the approved erection procedure support a reduced percentage of bolts. However, the minimum of 50% combination of erection pins and bolts will still be required. Primary member splice connections that are made up on the ground (prior to erection) shall be 100% complete and fully tensioned, in the no- load condition, prior to any lifting operation. Cross- frames and lateral bracing on curved girder bridges shall be fully tensioned before crane release to ensure stability during erection, unless othe rwise allowed on the approved erection plans. Use temporary bolts, including , but not limited to, erection and fit -up bolts, supplied with square or hexagon heads and square or hexagon nuts. The use of hexagon head temporary bolts and nuts is allowed, but paint both the head and nut with a durable yellow paint before installation. Field reaming may be used to correct minor misfits, without prior approval of the Engineer, subject to the following limitations:
A.Ream no more than 10 percent of the holes in a connection .
B.Ream no single hole more than 1/16” larger than the plan nominal hole diameter .
C.Assemble and securely hold connecting parts together .
D.Perform reaming with twist reams placed perpendicular to connecting parts .
E.Remove burrs on the outs ide surfaces .
F.Repair coatings in accordance with Section 442 of the s pecifications . For members with defects that cannot be corrected by reaming within these limits or that prevent the proper assembly of parts, the Contractor shall submit proposed correct ive methods to the Engineer for review and approval. All field reaming shall be documented and performed in the presence of the Engineer. Upon completion, documentation of field reaming shall be submitted to the Engineer for record purposes. The use of e rection bolts for field welded joints is allowed. Use erection bolts that are galvanized when the finish paint is applied in the structural steel fabrication shop and meet ASTM F3125 Grade A325 . Supplement these bolts with clamps as necessary to meet the AWS Specifications. Where unpainted AASHTO M 270 Grade 50W structural steel is used, use erection bolts meeting ASTM F3125 Grade A325 . After field welding the connection, leave the erection bolt in place with at least the minimum bolt tension shown in Table 440 -1. Use holes that are 3/16 inch larger than the nominal erection bolt diameter.
440-7 Field Welding
Perform field welding only when called for in the plan s and in a ccordance with
Article 1072 — 18.
4-57 Remove paint , galvanizing or other coating from the weld heat affected zone at the location of
field welds by blast cleaning (SSPC SP -6 finish) or power tool cleaning to bare metal , (SSPC SP-11 finish) just before welding. Clean sufficiently to bare metal to prevent contamination of the weld by the coating .
440-8 Connections Using High Strength Bolts
A.General This article covers the assembly of structural joints using plain or galvanized high strength carbon steel bolts with suitable nuts and washers tightened to a high tension. Use bolt holes that conform to Article 1072 -16. Protect bolts, nuts and washers fr om moisture during storage and so they show no signs of rust at the time of installation. Make sure that plain bolts and washers have a thin coat of lubricant at the time of installation. Use nuts that are pre- waxed by the producer or supplier before shipping to the project. Apply beeswax, stick paraffin or other approved lubricant to the threads of galvanized bolts just before installing the bolts. Use bolt, nut and washer (when required) combinations from the same rotational -capacity lot. Perform the rota tional- capacity test described in Subarticle 1072- 5(D)(4) on each rotational- capacity lot before the start of bolt installation. Use hardened steel washers as required by the test.
B.Bolted Parts Make sure that the slope of surfaces of bolted parts in contact with the bolt head and nut does not exceed 1:20 with respect to a plane normal to the bolt axis. Make sure bolted parts fit solidly together when assembled and are not separated by gaskets or any other interposed compressible material. Provide co ntact surfaces, including those adjacent to the bolt heads, nuts or washers, that are free of scale, dirt, burrs, oil, lacquer, loose rust, rust inhibitor, other foreign material and other defects that prevent solid seating of the parts.
C.Installation
1.Bolt Tensions Tighten each fastener to provide at least the minimum bolt tension shown in Table 440-1. Tighten fasteners with direct tension indicators in accordance with Subarticle 440-8(C)(5 ), or if permitted, by the use of load indicating bolts as provide d in Subarticle 440 -8(C)( 3). TABLE 440-1 REQUIRED BOLT TENSION Bolt Size, Inches Minimum Bolt Tension , Pounds 1/2 12,050 5/8 19,200 3/4 28,400 7/8 39,250 1 51,500 1 l/8 64,900 1 1/4 82,400 1 3/8 98,200 1 1/2 119,500
4-58 In situations where the nut cannot be properly accessed due to lack of clearance,
tighten by turning the bolt while preventing the nut from rotating. Use impact wrenches, if necessary, with adequate capacity and su fficiently supplied with air to perform the required tightening of each bolt in approximately 10 seconds.
2.Washers Make sure all fasteners have a hardened washer under the element , nut or bolt head , turned in tightening. Use galvanized washers when galvani zed nuts and bolts are required. As an exception to the above, use special washers for oversize, short -slotted and long- slotted holes in accordance with Subarticle 1072 -16(H). Where an outer face of the bolted parts has a slope of more than 1:20 with respect to a plane normal to the bolt axis, use a smooth beveled washer to compensate for the lack of parallelism.
3.Load Indicating Bolts Tightening by use of a load indicating bolt system is permitted provided it can be demonstrated by an accurate direct measurement procedure that the bolt is tightened in accordance with Table 440- 1. Tighten by approved methods and procedures.
4.Galvanized High Strength Bolts Use mechanically galvanized high strength bolts in all bolted connections for painted structural steel. Install galvanized high strength bolts carefully so shop painted surfaces are not scarred or otherwise damaged. Repair galvanized surfaces that are abraded or damaged by thoroughly wire brushing the damaged area and removing all loose and cracked coating, after which give the cleaned area 2 coats of non- aerosol organic zinc repair paint , in accordance with
Article 1076 — 7.
Galvanized or coated bolts of any grade that have been previously tensioned up to and including snug tight and subsequently loosened shall not be reused.
5.Direct Tension Indicators (DTI’s) Supply DTI’s in accordance with ASTM F959 and Article 1072 -5. Furn ish the Engineer with at least four 0.005 inch metal feeler gauge s for each container of DTI’s shipped before beginning installation. Make sure that the lot number on the containers of DTI’s is for the same lot number tested as indicated on the test docume nts. Furnish to the Engineer 3 samples of load indicating washers from each lot number, each size and type for tests and 4 each of the metal feeler gauge s required for performing the tests. Install the DTI under the bolt head. If it is necessary to instal l the DTI under the nut, or if the bolt head shall be turned, install additional hardened washers between the nut or bolt head and the DTI . Provide a calibrated Skidmore -Wilhelm Tension Indicating Device (or an acceptable equivalent device) on the project for determining the tension imposed on a fastener when the protrusions on the DTI are properly compressed. Ensure an AASHTO accredited testing facility calibrates the device within 12 months of the testing date and provide the Engineer a certificate of calibration. Test 3 samples from each lot of DTI’s in the presence of the Engineer. Achieve a minimum bolt tension of 5% greater than that required by Table 440 -1.
4-59 Do not substitute DTI’s for hardened steel washers required with short slott ed or
oversized holes. If desired, use direct tension indicators in conjunction with hardened steel washers. Install DTI’s initially to a snug tight condition in accordance with Article 440 -6. After snug tightening of all bolts, such that the plies of st eel members are brought into full contact, fully tighten beginning at the most rigid part of the joint and continuing toward its free edges. Ensure that DTI’s have not been partially compressed during the snugging process. For tightening fasteners contain ing DTI’s , use a clean and lubricated wrench. Maintain air supply and hoses in good condition and provide air pressure of at least 100 psi at the wrench. When tightening the fasteners, ensure that the part of the fastener being restrained from turning doe s not rotate during the tightening process. Ensure that no portion of the DTI protrusions is accidentally partially flattened before installing in the structural steel joints. Do not reuse direct tension indicators. If it is necessary to loosen a bolt pr eviously tensioned, discard and replace the DTI .
D.Inspection Allow the Engineer the opportunity to observe installation of bolts to determine that the selected tightening procedure is properly used. The Engineer determines when bolts are properly tightened and in the case of direct tension indicator bolts that the correct indication of tension is achieved. After properly tightening bolts, make sure that the end of the bolt is flush with or extended beyond the outer face of the nut. Do not begin pa inting in the area of tightened bolts until after bolt inspection is complete. When using direct tension indicators, proper tension of bolts is inspected by the Engineer by inserting a 0.005 inch thickness feeler gauge provided by the Contractor into the openings between adjacent flattened protrusions of the direct tension indicator. Proper tension is obtained when the number of spaces for which the gauge is refused is equal to or greater than the value shown in Table 440-2. TABLE 440-2 DIRECT TENSION INDICATOR GAP REFUSAL Number of Spaces in Washer Number of Spaces Gauge is Refused The gauge shall be refused in all spaces when the direct tension indicator is used under the turned element. When using direct tension indicators, do not tighten bolts to a no visible gap condition. At least 10%, but no less than 2 of the bolts in each connection a re inspected with feeler gauges. Additionally, all remaining bolts in each connection are visually inspected for proper tightening.
440-9 Surface Preparation and Protection of Weathering Steel
After fabrication, shop clean all weathering steel remaining in the unpainted condition in the completed structure to a SSPC SP -6 finish. Provide a contact surface condition in accordance with Subarticle 442 -7(B) at the time of bolt installation.
Source: North Carolina Standard Specifications for Roads and Structures, 2024 Edition. Pages 190–195 of 857.