5-80 TABLE 4- Minimum Installation Tension
U.S. Customary Bolt Diameter (inches) 5/8 3/4 7/8 1 1-1/8 1-1/4 1-1/2 Bolt Tension (kips) 20 29 41 54 59 75 108
d.Using a thickness gauge pr ovided by the DTI manufacturer, r ecord the number of spaces between the protrusions on the DTI that a 0.005 inch thi ckness gage is refused.
e.If the number of refusals exceeds the number in Table 5, the DTI has failed the DTI Verification Test for minimum tension. Reject the DTI lot. TABLE 5 *If the test is a coated DTI, the maximum number of spaces the gage is refused is the number of spaces on the DTI minus one
2.Step 2 is to determine the maximum bolt tension allowable u sing a DTI.
a.After completing step 1, the bolt shall be further tighten ed to the smallest gap to be used during installation. Normally, this is defined as a condi tion where all gaps refuse a 0.005 inch gage but at least one visible gap remains.
b.Remove the bolt from the tension measuring device and turn the nut on the threads of the bolt by hand. If the nut ca n be run the length of the th reads, excluding the thread run out, the DTI lot is acceptable. I f the nut is unable to run th e thread length at the smallest gap condition (defined in a) above), the test shall be performed ag ain using a larger acceptance gap.
504.50 Installation and Tensioning High Strength Bolts Select one of the methods listed
below for installing and tensioning high strength bolts. Do no t use standard torque determined by the use of tables or formulas that attempt to rel ate torque to tension.
504.51 Installation Install a hardened washer under the turned element and a hardened
washer on oversize holes. Install fasteners in all holes in a contiguous group, except for holes containing drift pins and br ing them to a snug tight cond ition, progressing systematically from the most severely restrained location in a connection to the free edges. Do not remove the drift pins until a minimum of 50% of the fast eners have been tensioned. Do not force the bolts. If the bolts cannot be installed easil y by hand, correct the hole alignment by installing more drift pins. Bolt Diameter (inches) ¾, 7/8 1, 1-1/8 1-1/4, 1-3/8 Number of Spaces in DTI 5 6 7 Maximum Number of gaps in which gage is refused * 2 2 3 5-81
504.52 Tensioning Install and tension bolts by: (1) the Calib rated Wrench method, (2)
the Turn of Nut method, (3) wit h Direct Tension Indicators or ( 4) Alternative Design Fasteners. Tension the fasteners systematically from the most r igid part of the joint to the free edges.
1.The Calibrated Wrench Method Adjustable pneumatic wrenches, adj ustable hydraulic wrenches or torque wrenches may be used. Calibrate the wrench used for tensioning bolts at least once ea ch shift with fastener assemblies of each diameter, length and R-C lot to be installed . Calibrate pneumatic wrenches any time a section of hose has been added or eliminate d. Calibrate pneumatic wrenches any time the compressor is changed. Randomly select five fastener assemblies of each length and R-C lot for wrench calibration. Install each of the fastener assemblies in the te nsion measuring device and install enough washers so at least three but no more than five threads are showing. Install at least one hardened washer under the turned element. Snug the b olt using the same procedure to be used during installation. If the wrench is an adjustable pneumatic wrench or an adjustabl e hydraulic wrench, set the adjustment so that each of the three assemblies is tensione d to no less than the Minimum Installation Tension specified in Table 4 above. If a torque wrench is used, tension five randomly selected fast ener assemblies to the minimum tension specified in Table 4. Record the torque readin gs. Discard the high and low torque reading. The job installation torque shall be the a verage of the three remaining torque values. When bolts are too short to fit in the tension-measuring device , install five randomly selected fasteners in a soli d joint with a hole diameter no gre ater than 1/16 inch the nominal bolt diameter. Rotate each asse mbly 1/3 turn and record the to rque. Discard the high and low torque reading. The job installation torque shall be the a verage of the three remaining torque values. Bolts used to calibrate wrenches may be re-used. 2. The “Turn of Nut” Method Perform the Turn of Nut calibrati on once, prior to fastener installation, for eac h diameter, length and R-C lot. Select a random sample of no less than three fastener assemblie s of each diameter, length and R-C lot. Install each assembly in a tension-measuri ng device. Bring the fastener assembly to snug tight (approximately 10% of the minimum instal lation tension from Table 4). Match mark the socket to r eference points on the tension-me asuring device in order to accurately determine nut rotation. Tighten the bolt to the requ ired rotation specified in Table
6.Record the tensions for eac h diameter, length and R_C lot. The average of the three tension readings shall be no less than the Minimum Installation Tension specified in Table 5-82
4.If any of the three fastener assemblies does not achieve m inimum installation tension at the specified rotation, select three more and re-test. Increas e the minimum rotation if necessary. Snug all the bolts in a contiguous group. Rotate the turned el ement the appropriate amount rotation specified in T ABLE 6. The unturned element sha ll be held by a wrench to prevent rotation during tightening. TABLE 6 Nut Rotation from Snug Tight 1, 2, 3 Disposition of Outer Faces of Bolted Parts Bolt Length Measured from Underside of head to extreme of point Both Faces Normal to Axis 3 One Face Normal to Bolt Axis and Other Face Sloped Not More Than 1 to 20 (bevel washer not used) 3 Both Faces Sloped Not More Than 1 to 20 from Normal to Axis (bevel washer not used) Up to and including 4 diameters 1/3 turn ½ turn 2/3 turn Over 4 diameters but not exceeding 8 diameters ½ turn 2/3 turn 5/6 turn Over 8 diameters but not exceeding 12 diameters 2/3 turn 5/6 turn 1 turn 1 Nut rotation is relative to bolt, regardless of the element ( nut of bolt) being turned. 2 For bolts tensioned with ½ turn or less, the tolerance shall be plus or minus 30 degree. For bolts tensioned with more than ½ turn, the tolerance shall be p lus or minus 45 degrees. 3 No research work has been performed by the Research Council on Riveted and Bolted Structural Joints to establish the turn-of-nut procedure when b olt lengths exceed 12 diameters, therefore, the required rotation must be determined by actual t ests in a suitable tension- measuring device simulating the actual condition.
3.Tensioning Fastener Assemblies with DTI’s Tension fasteners using DTI’s so that a 0.005 inch feeler gage is refused in at least the number of gap s shown in Table 7 and a minimum of one visible gap remains. Tightening beyond crushing the DTI shall be cause for rejection of the fastener assembly. TABLE 7 Inspection Criteria for DTI’s Number of gaps in DTI 4 5 6 7 8 9 Minimum number of gap refusals 2 3 3 4 4 5
4.Alternate Design Fasteners Alternate design fasteners tha t are designed to indicate bolt tension indirectly or tension bolts automatically may be u sed only with the approval of the Fabrication Engineer. Alternate design fasteners shall mee t the chemical and 5-83 mechanical requirements of AASHTO M 164M / M 164 (ASTM A 325/ A 325M) and shall have the same body diameter of similar traditional fasteners a nd not less than the same bearing area under the head and nut as a similar heavy hex fast ener. Provide a detailed written installation procedure from the fast ener manufacturer to the Fabrication Engineer for approva l prior to beginning bolt insta llation. The Fabrication Engineer may modify or place restrictions on the installation p rocedure prior to approval. Calibrate three random samples in a tension-measuring device. Each fastener shall achieve the Minimum Bolt Tension from Table 4 when installed an d tensioned in accordance with the approved installation procedure. If any of the three fasteners fails to achieve 100% of the Minimum Bolt Tension, a retest of five fast ener assemblies from the same lot may be performed. If any of the five fastener assembl ies fails to achieve 100% of the Minimum Bolt Tension, the lot shall be rejected. The Resid ent may require re- calibration of the fasteners if the condition of the fasteners has significantly changed. Tension alternate design fasteners immediately after installati on. Alternate design fasteners are extremely dependent on proper lubrication and thr ead condition. Handle and store fasteners in accordance with the manufacturer’s recommend ations. Fasteners that have been improperly handled or stored shall be rejected.
504.53 Inspection Inspect all completed joints within 72 hours following completion of
tensioning each joint or contiguous group of fasteners. Use the following inspection procedure: 1. The Contractor, in the presence of the Resident shall use a calibrated torque wrench as an inspection tool.
2.At least once each day, tighten a representative sample o f five bolts from each diameter, length and Ro-Cap lot us ed in the work in the tension -measuring device to the Minimum Bolt Tension specified in Table 6. Place a washer unde r the turned element of each bolt assembly. The job inspection torque shall be the ave rage of three values after rejecting the high and low values.
3.Bolts represented by the sample in the preceding paragraph w hich have been tightened in the structure shall be inspected by applying, in t he tightening direction, the inspection wrench and the job inspection torque to a minimum of 10% of the bolts, but not less than two bolts, selected at random, in each connection. I f any nut or bolt is turned more than five degrees (approximately one inch at a twelve inch radi us) by the application of the job inspection torque, all bolts in the connection shall be tes ted. Alternatively, the Contractor or Erector may re-tighten all the bolts in the conne ction before the specified inspection. 5-84
4.For joints using DTI’s, inspection will consist of verifying that the DTI has the minimum number of refusals required from Table 9 and the minimu m gap allowed in the work (from the DTI Verificati on Test) remains in at least one s pace.
5.At the Resident’s option, if the Quality Assurance Inspecto r witnesses the initial and final tensioning of fasteners i n a joint using the “Turn of Nut ” method and finds it acceptable, no further inspection will be required.
504.54 Reuse of Bolts Reuse only black AASHTO M164M/M164 (ASTM
A325/A325M) bolts. Do not reuse galvanized fasteners.
504.55 Field Welding Welders shall have in their possession a valid certification for the
process and position to be used in production from the American Welding Society or other organization acceptable to the Resident. Submit a written Weld Procedure Specification for each joint to the Fabrication Engineer for review. Provide the Weld P rocedure Specification to the we lder and Resident prior to beginning welding. Do not perform field welding without an app roved Weld Procedure Specification. Power sources shall have meters indicating ampe rage/voltage that have been calibrated within 1 year. Field welding and nondestructive examination of field welds sha ll be done in conformance with the requirements of the D 1.5 Code.
504.56 Misfits The correction of misfits involving minor reami ng will be considered a
legitimate part of steel erection. Errors in shop fabrication or deformation from handling and transportation that prevents the proper assembling and fit- up of parts by the use of drift pins or by reaming (not to excee d 10% of the holes in a contigu ous array) shall be reported immediately to the Resident. P rovide a written proposal for co rrection to the Fabrication Engineer. Do not make any field corrections that involve cutti ng or welding without the permission of the Resident. ANCILLARY BRIDGE PRODUCTS and SUPPORT STRUCTURES
504.57 Ancillary Bridge Products Ancillary bridge products are defined in Subsection
713.01 of the Standard Specifications. Fabricate ancillary bri dge products in accordance
with the D1.5 Code as applicable to ancillary bridge products a nd this Specification. Fabricate tubular products in accordance with the AWS D1.1 Stru ctural Welding Code (the D1.1 Code).
504.58 Support Structures Weld support structures in accordanc e with the D1.1 Code.
Support structures shall include, but not be limited to, non-ve hicular bridges, high mast poles, light and signal poles , dual purpose poles, strain poles and sign supports; cantilever, bridge and butterfly support structures.
Source: Maine Standard Specifications for Road and Bridge Construction, 2020 Edition. Pages 372–376 of 817.