ASSEMBLY OF STRUCTURAL CONNECTIONS USING HIGH

ASSEMBLY OF STRUCTURAL CONNECTIONSUSING HIGH-STRENGTH BOLTSBRIDGE CONSTRUCTIONINSPECTION TRAINING2004/2013

HIGH STRENGTH BOLTSGENERAL CONCEPTSSPECIFICATIONSFIELD ROTATIONAL-CAPACITY TESTINSTALLATIONINSPECTION

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GENERAL CONCEPTSTYPES OF PES OF BOLTSERECTIONROTATIONAL CAPACITY TESTINSPECTION

TYPES OF CONNECTIONSBEARING TYPE CONNECTION:BEARING OF THE SHANK OF THE BOLT AGAINST THE SIDE OFTHE HOLE - PLATE MATERIAL.(ADEQUATE FOR STATIC LOADING)

SLIP-CRITICAL CONNETIONS:TENSION FORCE IN THE BOLT GENERATESA CLAMPING FORCE BETWEEN PIECES OFMATERIAL BEING SPLICED TOGETHER.(WHEN NO SLIP AT SERVICE LOAD ISDESIRED)(RESISTS FATIGUE LOADING STRESS REVERSALS)SLIP-CRITICAL CONNECTION(SINGLE SHEAR)

What type of connections, for boltedgirder splices, do we (VDOT) use?A) Full penetration field weldsB) Bolted bearing connectionsC) Bolted slip-critical connections

C) Bolted slip-critical connectionsAASHTO - VDOT Design Specification:10.18 SPLICESBolted splices shall be designed as slipcritical connections.

SPECIFICATIONSSEC 407.06SEC 407.06(b)SEC 226.02SEC 226.02

What type of bolts do we (VDOT) typicallyrequire for making structural fieldconnections in bridges?A) 7/8” Diameter ASTM A307 boltsB) 7/8” Diameter ASTM A325 boltsC) 7/8” Diameter ASTM A490 bolts

B) 7/8” Diameter ASTM A325 boltsSEC 407.06(b)Field connections shall be made with highstrength 7/8 inch diameter bolts fabricated inaccordance with ASTM A325,unlessotherwise specified.

Torque vs. Tensionhttp://www.youtube.com/watch?v O96AUlIBkU8

SPECIFICATIONS407.06 (3)Required minimum Tension (lb) for a 7/8” ASTMA 325 bolt 39,000 lbs.39,000 lbs 39 kips

Snug tight condition is best defined as?A) Snug tight is defined as the tightnessattained such that the complete area of theconnecting surfaces are brought into firmcontact with each other.B) Snug tight is defined as tightness attainedwhen installing high strength bolts using turnof-nut method.C) Snug tight is defined as tightness attainedwhen all bolts in a connection have beentorqued to 569 FT-LB.

SPECIFICATIONSSEC 407.06(c)2. Bolted parts:Bolted parts shall fit solidly together when assembled and shall not beseparated by gaskets or any other interposed compressible material.

SPECIFICATIONS407.06 (b)3. Installation:An approved tension-indicating device (SKIDMORE-WHILHELMCALIBRATOR) shall be at all job sites where high-strength fastenersare being installed and tightened. Bolt tensioning devices and completebolt assemblies shall be tested with this device at the start ofconstruction and as required for the installation procedure. Thecalibrating device shall be capable of indicating actual bolt tension withina tolerance of 2 percent. The manufacturer or an approved testingagency shall have checked the device for the accuracy specified hereinwithin the previous 12 months. When turn-of-nut or direct tensionindicators are used, a representative sample of at least three completebolt assemblies of each diameter, length, and grade shall be tested.

Calibration

INSTALLATIONTIPS:COORDINATE WITH CONTRACTOR AND STEEL ERECTOR PRIOR TODELIVERY OF STRUCTURAL STEEL(METHODS OF ERECTION)(PROCEDURES OF ERECTION AND BOLT INSTALLATION TURN-OF-NUT METHOD OR DIRECT TENSION INDICATOR)FIELD ROTATIONAL CAPACITY TEST REQUIRED FOR ALL METHODS OFINSTALLATION(RECOMMEND PERFORMING TESTS PRIOR TO STARTINGSTEEL ERECTION)

INSPECTIONSEC 407.06 (b)3. Inspection:When the inspection wrench is a torque wrench, each calibration testbolt shall be tightened in the calibration device to the minimum tensionspecified for its size in Table IV - 3. (7/8” Dia. ASTM A325 – 39,000 lbs)The inspection wrench shall then be applied to the tightened bolt, andthe torque necessary to turn the nut or bolt head 5-degrees(approximately 1 inch at 12 inches radius) in the tightening direction shallbe determined.The average torque measured in the tests of three bolts shall be takenas the job-inspection torque.

INSPECTIONSEC 407.06 (b)3. Inspection:Bolts that have been tightened in the structure shall be inspected in thepresence of the Engineer by applying, in the tightening direction, theinspection wrench and its job-inspection torque to 10-percent of thebolts, but not fewer than two bolts, selected at random in eachconnection.If no nut or bolt head is turned by this application of the job-inspectiontorque, the connection will be accepted as properly tightened.If any nut or bolt head is turned by the application of the job-inspectiontorque, this torque shall be applied to all bolts in the connection. Boltswhose nut or head is turned by the job-inspection torque shall betightened and re-inspected, or all the bolts in the connection may beretightened and the connection resubmitted for the specified inspection.

SPECIFICATIONSSEC 407.06 (b)3. Installation:Fasteners shall be tightened to provide, when all fasteners in the connectionare tight, at least the minimum bolt tensions shown in Table IV-3 for the sizeof fastener used. Minimum bolt tension is also known as the Proof Load .For a 7/8” diameter ASTM A325 bolt the required minimum bolt tension (ProofLoad) is 39,000 lbs.

SPECIFICATIONSSEC 407.06 (b)3. Installation:MAJOR CHANGE IN VDOT SPECIFICATIONSTightening shall be performed by the turn-of-nut method,or by the use of a direct tension indicator using a loadindicator washer.Power wrenches, if used, shall be of adequate capacity and sufficientlysupplied with air to perform the required tightening of each bolt inapproximately 10 seconds.A CALIBRATED WRENCH IS NO LONGER ALLOWED!(POWER WRENCH CAN BE USED TO PERFORM TURN-OF-NUT)

SPECIFICATIONSSEC 407.06 (b)3. Installation:Snug tightening shall progress systematically from the most rigid part of theconnection to the free edges, and then the bolts of the connection shall beretightened in a similar systematic manner as necessary until all bolts aresimultaneously snug tight and the connection is fully compacted.a.Turn-of-nut tightening:When the turn-of-nut method for tightening high-strength bolts is used, boltsshall be installed in all holes and tightened to a snug tight condition to ensurethat all parts of the joint are brought into contact with each other.All bolts shall be given a suitable match-mark and tightened additionally bythe applicable amount of nut rotation specified in Table IV-4, progressingsystematically from the most rigid part of the joint to its free edges.

SPECIFICATIONSSEC 407.06 (b)3. Installation:a.Turn-of-nut tightening:TABLE IV – 4BOLT LENGTHBOTH FACESNORMALTO BOLT AXISUp to and including 4 diameters1/3 turnMore than 4 but not more than 8 diameters1/2 turnMore than 8 but not more than 12 diameters2/3 turn

Match marking for turn of the nut method

Close up of match marking for turn of thenut method

Close up of the best match marking forturn of the nut method (don’t forget tomark the bolt to make sure it does notturn when the nut is tightened.

Is there a problem here?

ROTATIONAL-CAPACITY TESTPURPOSE:VERIFY THAT THE FASTENER ASSEMBLY PROVIDED WILL FUNCTIONPROPERLY AS A UNITTHE ROTATIONAL-CAPACITY TEST ALSO CHECKS THE FOLLOWINGQUALITIES OF THE ASSEMBLY:Efficiency of lubricationInstallation ductilityStripping

Determine 10% of the specified proof loadfor a 7/8 inch Diameter ASTM A325 Bolt?(answer in a value of Tension)A) 4,100 LBB) 569 FT-LBC) 3,900 LB

C) 3,900 LBTABLE IV-3 BOLT TENSION7/8 inch Diameter ASTM A325 BoltRequired Min. Bolt Tension 39,000 LB (Proof Load)10% of Proof Load 0.10 x 39,000 LB 3,900 LB

ROTATIONAL-CAPACITY TESTPERFORMING THE TEST:UPON COMPLETION OF THE REQUIRED ROTATION, THE ASSEMBLY MUSTSHOW NO SIGNS OF FAILURE DEFINED AS FOLLOWS:INABILITY TO ROTATE THE ASSEMBLY TO THE NUMBER OF TURNS ASSPECIFIED IN SEC 226.02 (h) 3. a.INABILITY TO REMOVE THE NUT FOLLOWING THE TEST(NUT SHOULD SPIN “FREELY”)SHEAR FAILURE OF THE THREADS DETERMINED BY VISUAL INSPECTION(BOLT AND NUT THREADS)TORSIONAL FAILURE OF BOLT (TWISTING)

ROTATIONAL-CAPACITY TESTSEC 407.06(b)1.Bolts, nuts, and washers:Prior to installation, the Contractor shall perform a field rotational-capacitytest on two nut, bolt, and washer assemblies for each diameter and length inaccordance with Section 226.02(h)3.

SPECIFICATIONSSEC 407.06 (c)3. Installation:Bolts shall be installed with a hardened washer under the nut or bolt head,whichever is the element turned in tightening.The length of bolts shall be such that the point of the bolt will be flush with oroutside the face of the nut when completely installed without over-tensioningthe bolt.(Contractor shall also perform field rotational-capacity test)

ROTATIONAL-CAPACITY TESTPERFORMING THE TEST:ELONGATION OF BOLT, IN THREADS BETWEEN THE NUT AND BOLT HEAD,IS TO BE EXPECTED AT THE REQUIRED ROTATION AND IS NOT TO BECLASSIFIED AS A FAILURE.

ROTATIONAL-CAPACITY TESTDOCUMENTATION:SPECIFICATION AND CONSTRUCTION MANUAL DO NOT ADDRESSDOCUMENTATION SHOULD BE KEEP IN PROJECT RECORDS (Diary)RECORD: (TWO ASSEMBLIES TESTED PER LENGTH PER RCT LOT)CALIBRATOR SERIAL NO. CALIBRATION DATEBOLT DIAMETERBOLT LENGTHNO. TURNSMEASURED TENSIONTYPE/GRADE BOLTRCT LOT NO.MEASURED TORQUENOTE CONDITION OF BOLT AFTER COMPLETING TESTCONTACT BRIDGE SECTION IF BOLTS DO NOT PASS RCT (DO NOT USE)

ROTATIONAL-CAPACITY TESTProject No.Date:Rotational Capacity Test ResultsGrade A325,Galvanized Bolt Diameter 7/8"Skidmore - Wilhelm Bolt Tension Calibrator Serial No. 5031 Calibration Date - 09/09/994 3/4" Length@ 1 turnMeasured TensionMeasured TorqueLot # 508064 A# 1 53,000 LB# 2 50,000 LB2 3/4" Length Lot # 508039 C@ 2/3 turn# 1 56,000 LB# 2 51,000 LB# 1 760 FT-LB# 2 760 FT-LB# 1 540 FT-LB# 2 610 FT-LB4" Length Lot # 505364 A@ 1 turnMeasured Tension# 1 60,000 LB# 2 60,000 LBMeasured Torque2 1/2" LengthLot # 95094 A@ 2/3 turnLength insufficient for tensionmeasurement# 1 700 FT-LB# 1 700 FT-LB# 2 800 FT-LB# 2 800 FT-LBNo failures noted - all threads OK after tensioning

ROTATIONAL-CAPACITY TEST

INSPECTIONSEC 407.06 (b)3. Inspection:(TORQUE WRENCH)The Engineer will observe the installation and tightening ofbolts to determine that the selected tightening procedure is properlyused and will determine that all bolts are tightened.The Contractor in the presence of the Engineer shall use an inspectionwrench to inspect the tightening of bolts.There shall be a washer under the part turned in tightening each bolt ifwashers are so used on the structure.

Bolts shall be inspected to ensure that theproper is achieved.A) torqueB) tensionC) number of turns

B) tensionTABLE IV-3 BOLT TENSIONWe want to ensure that the proof load (requiredminimum bolt tension) for a given bolt is achieved.(Proof load-7/8” Diameter ASTM A325 bolt 39,000 LB)

INSPECTIONTIPS:WHEN INSTALLING HIGH STENGTH BOLTS A MINIMUM BOLT TENSION ISREQUIRED (SLIP-CRITICAL CONNECTION)TORQUE CAN BE DIRECTLY RELATED TO TENSION UNDER IDEALCONDITIONS:(PROPER STORAGE OF BOLTS, NUTS, WASHERS)(PROPER LUBRICATION OF BOLTS, NUTS)(RUST FREE BOLTS AND NUTS)ASTM A325 3/4 INCH DIAMETER BOLT (REQD MIN. TENSION 28,000 LB)CONDITIONTENSIONTORQUEFAILURENEW28,000 LB300 FT-LBNADRY7,500 LB300 FT-LBNARUSTED10,000 LB300 FT-LBNA24,000 LB750 FT-LBBOLT- SHEAR

SPECIFICATIONSSEC 407.06 (3b)3 Installation:b. Direct tension olting-resources/pop-videos.php?video calibration.html

WHAT DOES THE FUTURE HOLD FOR BOLTS!

When the inspection wrench is a torque wrench, each calibration test bolt shall be tightened in the calibration device to the minimum tension specified for its size in Table IV - 3. (7/8” Dia. ASTM A325 –39,000 lbs) The inspection wrench shall then be applied to the tightened bolt, and the torque necessar