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New FatigueProvisions forthe Design of
Crane RunwayGirders
James M. Fisher
Julius P. Van de Pas
Author
James M. Fisher is vice presi-dent of Computerized
Structural Design (CSD), aMilwaukee, Wisconsin consultingengineering firm. Dr. Fisherreceived a bachelor of sciencedegree in civil engineering fromthe University of Wisconsin in1962. After serving two years asa Lieutenant in the United StatesArmy Corps of Engineers, Dr.Fisher continued his formal edu-cation. He received his master ofscience and Ph.D. degree instructural engineering from theUniversity of Illinois in 1965 and1968 respectively. Prior to joiningCSD, Dr. Fisher was an assistantprofessor of structural engineeringat the University of Wisconsin atMilwaukee. He is a registeredstructural engineer in severalstates.
Dr. Fisher has specialized instructural steel research anddevelopment. He has spent alarge part of his career investigat-ing building systems and thestudy of economical structuralframing systems. He was a for-mer chairman of the AmericanSociety of Civil EngineersCommittee on the Design of SteelBuilding Structures.
Dr. Fisher is a member of theAmerican Iron and Steel Institute(AISI) Committee onSpecifications, and a member ofthe AISC Specification Committeefor the Design Fabrication andErection of Structural SteelBuildings.
Dr. Fisher is the co-author ofseven books, as-well-as theauthor of many technical publica-tions in the field of structural engi-neering.
He is a member of theAmerican Society of CivilEngineers and honorary fraterni-ties Tau Beta Pi, Sigma Xi, ChiEpsilon and Phi Kappa Phi.
Dr. Fisher received the 1984T.R. Higgins Lecturship Awardpresented by the AmericanInstitute of Steel Construction.
Author
Julius P. Van de Pas is a princi-pal at Computerized Structural
Design and manages the firm'sColorado office. Mr. Van de Pashas been employed at CSD since1988. During his tenure at CSD,he has been responsible for thestructural design of numerousindustrial, commercial and institu-tional buildings.
Mr. Van de Pas received abachelor of science degree in civilengineering from the University ofWisconsin-Platteville in 1984 anda master of science degree in civilengineering from the University ofWisconsin-Milwaukee in 1991.He is Licensed as a Professionalengineer in Wisconsin, Michigan,California and Colorado.
In addition, Mr. Van de Pas hasserved as an adjunct assistantprofessor at the University ofWisconsin-Milwaukee. He hasalso co-authored a publication onsteel joist construction.
Summary
This paper will discuss thedesign of crane buildings rela-
tive to fatigue requirements.Emphasis is placed on the designand detailing requirements toavoid failures due to fatigue.Typical girder configurations,details, and problem areas will bediscussed, including lessons thathave been learned from previousfatigue related failures. Examplesare provided to illustrate how thedesigner can apply the new 1999AISC Fatigue Requirements todesign for the anticipated servicerequirements.
The allowable stresses for fatigue design are based on the 1999 AISC Specification Appendix K. In
accordance with AISE Section 3.10 fatigue loading is based on either the vertical load from one crane
including impact and 50% of the maximum lateral load, or the vertical load from both cranes and 50% of
the maximum lateral load. The following fatigue conditions will be evaluated:
1. The tension flange flexural stress.2. The web to tension flange shear flow stress.3. The top flange at the rail clips for lateral load flexural stress.4. The weld at the base of the intermediate stiffeners.
1. Tension Flange
Check the tension flange. Only the live load moment is used to determine the bending stress.
From the 1999 AISC Specifications Table A-K3.1, Stress Category B, Section 3.1,
2. Web to Flange Welds
Determine the fillet weld size for the bottom flange attachment to the web. This fillet weld is designed to
provide adequate shear flow capacity. The shear is based on the maximum live load shear on the girder.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
DRAFT(The following replaces the entire old Appendix K3)
K3 DESIGN FOR CYCLIC LOADING (FATIGUE)
This appendix applies to members and connections subject to high cycleloading within the elastic range of stresses of frequency and magnitudesufficient to initiate cracking and progressive failure (fatigue).
1. GeneralThe provisions of this section apply to stresses calculated on the basis ofUnfactored loads. The maximum permitted stress due to Unfactored loads is0.66
Stress range is defined as the magnitude of the change in stress due to theapplication or removal of the Unfactored live load. In the case of a stressreversal, the stress range shall be computed as the numerical sum ofmaximum repeated tensile and compressive stresses or the numerical sum ofmaximum shearing stresses of opposite direction at the point of probablecrack initiation.
In the case of complete joint penetration butt welds, the maximum designstress range calculated by Equation A-K3.1 applies only to welds withinternal soundness meeting the acceptance requirements of Section 6.12.2 or6.13.2 of AWS D1.1.
No evaluation of fatigue resistance is required if the live load stress range isless than the threshold stress range, See Table A-K3.1.
No evaluation of fatigue resistance is required if the number of cycles ofapplication of live load is less than 2 x 104.
The cyclic load resistance determined by the provisions of this appendix isapplicable to structures with suitable corrosion protection or subject only tomildly corrosive atmospheres, such as normal atmospheric conditions.
The cyclic load resistance determined by the provisions of this appendix isapplicable only to structures subject to temperatures not exceeding 300° F(150° C).
The Engineer of Record shall provide either complete details including weldsizes or shall specify the planned cycle life and the maximum range ofmoments, shears and reactions for the connections.
2. Calculation of Maximum Stresses and Stress Ranges
Calculated stresses shall be based upon elastic analysis. Stresses shall not beamplified by stress concentration factors for geometrical discontinuities.
For bolts and threaded rods subject to axial tension, the calculated stressesshall include the effects of prying action, if any.
In the case of axial stress combined with bending, the maximum stresses, ofeach kind, shall be those determined for concurrent arrangements of theapplied load.
DRAFTFor members having symmetric cross sections, the fasteners and welds shallbe arranged symmetrically about the axis of the member, or the total stressesincluding those due to eccentricity shall be included in the calculation of thestress range.
For axially loaded angle members where the center of gravity of theconnecting welds lies between the line of the center of gravity of the anglecross section and the center of the connected leg, the effects of eccentricityshall be ignored. If the center of gravity of the connecting welds lies outsidethis zone, the total stresses, including those due to joint eccentricity, shall beincluded in the calculation of stress range.
3. Design Stress Range
The range of stress at service loads shall not exceed the stress range computedas follows.
(a) For stress categories except category A, B, B', C, D, E and E' the designstress range, shall be determined by Equation A-K3.1.
(A-K3.1)
Metric: (A-K3.1M)
where
Design stress range, ksi (MPa)Constant from Table A-K3.1 for categoryNumber of stress range fluctuations in design lifeNumber of stress range fluctuations per day x 365 x years of designlifeThreshold fatigue stress range, maximum stress range for indefinitedesign life from Table A-K3.1, ksi
(b) For stress category F, the design stress range, shall be determinedby Equation A-K3.2.
(A-K3.2)
Metric: (A-K3.2M)
(c) For tension-loaded plate elements at their end by cruciform, T or cornerdetails with complete joint penetration welds or partial joint penetrationwelds, fillet welds, or combinations of the preceding, transverse to thedirection of stress, the maximum stress range on the cross section of thetension-loaded plate element at the toe of the weld shall be determinedas follows:
DRAFTBased upon crack initiation from the toe of the weld on the tensionloaded plate element the design stress range, shall be determined byEquation A-K3.1, for Category C which is equal to
Metric:
Based upon crack initiation from the root of the weld the design stressrange, on the tension loaded plate element using transverse partial-joint- penetration welds, with or without reinforcing or contouring filletwelds, the design stress range on the cross section at the toe of the weldshall be determined by Equation A-K3.3, Category C' as follows:
(A-K3.3)
Metric: (A-K3.3M)
where:
reduction factor for reinforced or non-reinforced transverse PJPjoints
the length of the non-welded root face in the direction of thethickness of the tension-loaded plate, in. (mm)the leg size of the reinforcing or contouring fillet, if any, in thedirection of the thickness of the tension-loaded plate, in. (mm)thickness of tension loaded plate, in. (mm)
Based upon crack initiation from the roots of a pair of transverse filletwelds on opposite sides of the tension loaded plate element the designstress range, on the cross section at the toe of the welds shall bedetermined by Equation A-K3.4, Category C" as follows:
DRAFT(a) For mechanically fastened connections loaded in shear, the maximum
range of stress in the connected material at service loads shall not exceedthe design stress range computed using Equation A-K3.1 where andare taken from Section 2 of Table A-K3.1.
(b) For not-fully-tightened high-strength bolts, common bolts, and threadedanchor rods with cut, ground or rolled threads, the maximum range oftensile stress on the net tensile area from applied axial load and momentplus load due to prying action shall not exceed the design stress rangecomputed using Equation A-K3.1 or A-K3.1M. The factor shall betaken as 3.9 x 10 8 (as for category E'). The threshold stress, shall betaken as 7 ksi (as for category D). The net tensile area is given by EquationA-K3.5.
(A-K3.5)
Metric: (A-K3.5M)
where
pitch, mm per threadthe nominal diameter (body or shank diameter), in. (mm)threads per in.
In joints that are not fabricated and installed to satisfy all of the requirementsfor slip-critical connections (Section J3.8), except the requirements for fayingsurface condition, all axial load and moment applied to the joint plus effectsof prying action (if any) shall be assumed to be carried exclusively by thebolts or rods.
In joints that are fabricated and installed to satisfy all of the requirements forslip-critical connections, except requirements for faying surface condition, ananalysis of the relative stiffness of the connected parts and bolts shall bepermitted to be used to determine the tensile stress range in the pretensionedbolts due to the total service live load and moment plus effects of pryingaction. Alternatively, the stress range in the bolts shall be assumed to be equalto the stress on the net tensile area due to 20 percent of the absolute value ofthe service load axial load and moment from dead, live and other loads.
5. Special Fabrication and Erection Requirements
Longitudinal backing bars are permitted to remain in place, and if used, shallbe continuous. If splicing is necessary for long joints, the bar shall be joinedwith complete penetration butt joints and the reinforcement ground prior toassembly in the joint.
In transverse joints subject to tension, backing bars, if used, shall be removedand the joint back gouged and welded.
In transverse complete joint penetration tee and corner joints, a single passreinforcing fillet weld, not less than ¼ in. (6 mm) in size shall be added at re-entrant corners.
DRAFTThe surface roughness of flame cut edges subject to significant cyclic stressranges shall not exceed 1 000 µin. (25 µm), where ASME B46.1 is thereference standard.
Re-entrant corners at cuts, copes and weld access holes shall form a radius ofnot less than 3/8 in. (10 mm) by pre-drilling or sub-punching and reaming ahole, or by thermal cutting to form the radius of the cut. If the radius portionis formed by thermal cutting, the cut surface shall be ground to a bright metalsurface with a surface roughness value not more than(ASME B46.1).
For transverse butt joints in regions of high tensile stress, run-off tabs shall beused to provide for cascading the weld termination outside the finished joint.End dams shall not be used. Run-off tabs shall be removed and the end of theweld finished flush with the edge of the member.
See Section J2.2b Fillet Weld Terminations for requirements for end returnson certain fillet welds subject to cyclic service loading.
1.1 Base metal, except non-coatedweathering steel, with rolled or cleanedsurface Flame-cut edges with surfaceroughness value of 1 000 µin (25 µm)or less, but without re-entrant corners.1.2 Non-coated weathering steel basemetal with rolled or cleaned surface.Flame-cut edges with surfaceroughness value of 1 000 µin (25 µm)or less, but without re-entrant corners1.3 Member with drilled or reamedholes. Member with re-entrant cornersat copes, cuts, block-outs or othergeometrical discontinuities made torequirements of Appendix K3 5, exceptweld access holes, with surfaceroughness value of 1 000 µin (25 µm)or less
1.4 Rolled cross sections with weldaccess holes made to requirements ofSection J1.6 and Appendix K3.5.Members with drilled or reamed holescontaining bolts for attachment of lightbracing where there is a smalllongitudinal component of brace force.
A
B
B
C
250x108
120 x108
120 x108
44x108
24
24
16
10
Away from allwelds or structuralconnections
Away from allwelds or structuralconnections
At any externaledge or at holeperimeter
At reentrant cor-ner of weld accesshole or at anysmall hole (maycontain bolt forminor connec-tions)
SECTION 2 - CONNECTED MATERIAL IN MECHANICALLY FASTENED JOINTS
2.1 Gross area of base metal in lapjoints connected by high-strength boltsin joints satisfying all requirements forslip-critical connections
2.2 Base metal at net section of high-strength bolted joints, designed on thebasis of bearing resistance, butfabricated and installed to allrequirements for slip-criticalconnections2.3 Base metal at the net section ofother mechanically fastened jointsexcept eye bars and pin plates.
2.4 Base metal at net section of eyebarhead or pin plate.
B
B
D
E
120x108
120x108
22x108
11 x108
16
16
7
4.5
Through grosssection near hole
In net sectionoriginating at sideof hole
In net sectionoriginating at sideof holeIn net sectionoriginating at sideof hole
SECTION 3 - WELDED JOINTS JOINING COMPONENTS OR BUILT-UP MEMBERS
3.1 Base metal and filler metal inmembers without attachments built-upof plates or shapes connected bycontinuous longitudinal completepenetration groove welds, back gougedand welded from second side, or bycontinuous fillet welds.
3.2 Base metal and filler metal inmembers without attachments built-upof plates or shapes, connected bycontinuous longitudinal completepenetration groove welds with backingbars not removed, or by continuouspartial joint penetration groove welds.
3.3 Base metal and weld metaltermination of longitudinal welds at weldaccess holes in connected built-upmembers.
3.4 Base metal at ends of longitudinalintermittent fillet weld segments.
3.5 Base metal at ends of partial lengthwelded coverplates narrower than theflange having square or tapered ends,with or without welds across the ends ofcoverplates wider than the flange withwelds across the ends.
Flange thickness < 0.8 in. (20 mm)
Flange thickness > 0.8 in. (20 mm)
3.6 Base metal at ends of partial lengthwelded coverplates wider than theflange without welds across the ends.
B
B'
D
E
E
E'
E'
120x108
61 x 108
22x108
11 x108
11 x108
3.9 x108
3.9 x 108
16
12
7
4.5
4.5
2.6
2.6
From surface orinternaldiscontinuities inweld away fromend of weld
From surface orinternaldiscontinuities inweld, includingweld attachingbacking bars
From the weldtermination intothe web or flange
In connectedmaterial at startand stop locationsof any welddeposit
In flange at toe ofend weld or inflange attermination oflongitudinal weldor in edge offlange with widecoverplates
In edge of flangeat end ofcoverplate weld
SECTION 4 - LONGITUDINAL FILLET WELDED END CONNECTIONS
4.1 Base metal at junction of axiallyloaded members with longitudinallywelded end connections. Welds shallbe on each side of the axis of themember to balance weld stresses.t<½-in. (13mm)
t>½-in. (13mm)
E
E'
11x108
3.9x108
4.5
2.6
Initiating from endof any weldterminationextending into thebase metal
5.1 Base metal and filler metal in oradjacent to complete joint penetrationgroove welded splices in rolled orwelded cross sections with weldsground essentially parallel to thedirection of stress.5.2 Base metal and filler metal in oradjacent to complete joint penetrationgroove welded splices with weldsground essentially parallel to thedirection of stress at transitions inthickness or width made on a slope nogreater than 8 to 20%.
5.3 Base metal with equal to orgreater than 90 ksi (620 MPa) and fillermetal in or adjacent to complete jointpenetration groove welded splices withwelds ground essentially parallel to thedirection of stress at transitions in widthmade on a radius of not less than 2 ft.(600 mm) with the point of tangency atthe end of the groove weld.5.4 Base metal and filler metal in oradjacent to the toe of complete jointpenetration T or corner joints or splices,with or without transitions in thicknesshaving slopes no greater than 8 to 20%,when weld reinforcement is notremoved.5.5 Base metal and weld metal attransverse end connections of tension-loaded plate elements using partial jointpenetration butt or T or corner joints,with reinforcing or contouring fillets,shall be the smaller of the toe crack orroot crack stress range.Crack initiating from weld toe:
Crack initiating from weld root:
B
B
B'
B
C
C
C'
120 x 108
120 x108
61 x108
120 x108
44x108
44x108
Eqn.(A-K3.3)
16
16
12
16
10
10
Noneprovided
From internaldiscontinuities infiller metal oralong the fusionboundary
From internaldiscontinuities infiller metal oralong fusionboundary or atstart of transitionwhen(620 MPa)
From internaldiscontinuities infiller metal ordiscontinuitiesalong the fusionboundary
From surfacediscontinuity at toeof weld extendinginto base metal oralong fusionboundary.
Initiating fromgeometricaldiscontinuity at toeof weld extendinginto base metal or,initiating at weldroot subject totension extendingup and then outthrough weld
11/09/99 APPENDICES13-30
173
Description StressCategory
Constant Threshold Potential CrackInitiation Point
SECTION 5 - WELDED JOINTS TRANSVERSE TO DIRECTION OF STRESS
5.6 Base metal and filler metal attransverse end connections of tension-loaded plate elements using a pair offillet welds on opposite sides of theplate. shall be the smaller of thetoe crack or root crack stress range.Crack initiating from weld toe:
Crack initiating from weld root:
5.7 Base metal of tension loaded plateelements and on girders and rolledbeam webs or flanges at toe oftransverse fillet welds adjacent towelded transverse stiffeners.
C
C"
C
44 x 108
Eqn.(A-K3.4)
44x108
10
Noneprovided
10
Initiating fromgeometricaldiscontinuity at toeof weld extendinginto base metal or,initiating at weldroot subject totension extendingup and then outthrough weld
From geometricaldiscontinuity at toeof fillet extendinginto base metal
6.1 Base metal at details attached bycomplete joint penetration groove weldssubject to longitudinal loading onlywhen the detail embodies a transitionradius R with the weld terminationground smooth.
B
C
D
E
120 x 108
44x108
22x108
11 x 108
16
10
7
4.5
Near point oftangency of radiusat edge of member
11/09/99 APPENDICES 17513-32
Description StressCategory
Constant Threshold Potential CrackInitiation Point
SECTION 5 - WELDED JOINTS TRANSVERSE TO DIRECTION OF STRESS (cont'd)
SECTION 6 - BASE METAL AT WELDED TRANSVERSE MEMBER CONNECTIONS
6.2 Base metal at details of equalthickness attached by complete jointpenetration groove welds subject totransverse loading with or withoutlongitudinal loading when the detailembodies a transition radius R with theweld termination ground smooth:When weld reinforcement is removed:
(600 mm > 150 mm)
2 in. (50 mm) > R
When weld reinforcement is notremoved:
2 in. (50 mm) > R
6.3 Base metal at details of unequalthickness attached by complete jointpenetration groove welds subject totransverse loading with or withoutlongitudinal loading when the detailembodies a transition radius R with theweld termination ground smooth.
When weld reinforcement is removed:
When reinforcement is not removed:
Any radius
B
C
D
E
C
C
D
E
D
E
E
120 x108
44x108
22x108
11 x 108
44x108
44x108
22x108
11 x 108
22x108
11 x 108
11 X 108
16
10
7
4.5
10
10
7
4.5
74.5
4.5
Near points oftangency of radiusor in the weld or atfusion boundary ormember orattachment
At toe of the weldeither along edgeof member or theattachment
At toe of weldalong edge ofthinner material
In weld terminationin small radius
At toe of weldalong edge ofthinner material
11/09/99 APPENDICES13-34
177
Description StressCategory
Constant Threshold Potential CrackInitiation Point
SECTION 6 - BASE METAL AT WELDED TRANSVERSE MEMBER CONNECTIONS (cont'd)
6.4 Base metal subject to longitudinalstress at transverse members, with orwithout transverse stress, attached byfillet or partial penetration groove weldsparallel to direction of stress when thedetail embodies a transition radius, R,with weld termination ground smooth:
D
E
22x108
11 x108
74.5
In weld terminationor from the toe ofthe weld extendinginto member
7.1 Base metal subject to longitudinalloading at details attached by completepenetration groove welds parallel todirection of stress where the detailembodies a transition radius, R, lessthan 2 in. (50 mm), and with detaillength in direction of stress, a, andattachment height normal to surface ofmember, to:
a < 2 in. (50 mm)
or 4 in (100mm)
a> 12b or 4in. (100mm)when b is > 1 in. (25 mm)
7.2 Base metal subject to longitudinalstress at details attached by fillet orpartial joint penetration groove welds,with or without transverse load ondetail, when the detail embodies atransition radius, R, with weldtermination ground smooth:
R > 2 in. (50 mm)
C
D
E
E'
D
E
44 x 108
22 x 108
11x108
3.9 x108
22 x 108
11 x108
10
7
4.52.6
7
4.5
In the member atthe end of theweld
In weld terminationextending intomember
1 "Attachment" as used herein, is defined as any steel detail welded to a member which, by its merepresence and independent of its loading, causes a discontinuity in the stress flow in the member and thusreduces the fatigue resistance.
11/09/99 APPENDICES 17913-36
Description StressCategory
Constant Threshold Potential CrackInitiation Point
SECTION 6 - BASE METAL AT WELDED TRANSVERSE MEMBER CONNECTIONS (cont'd)
8.1 Base metal at stud-type shearconnectors attached by fillet or electricstud welding.
8.2 Shear on throat of continuous orintermittent longitudinal or transversefillet welds.
8.3 Base metal at plug or slot welds
8.4 Shear on plug or slot welds
8.5 Not fully-tightened high-strengthbolts, common bolts, threaded anchorrods and hanger rods with cut, groundor rolled threads. Stress range ontensile stress area due to live load plusprying action when applicable.
C
F
E
F
E'
44x108
50x1010
(FormulaA-K3.2)
11 x 108
50X1010
(FormulaA-F3.2)
3.9 x108
10
8
4.5
8
7
At toe of weld inbase metal
In throat of weld
At end of weld inbase metal
At faying surface
At the root of thethreads extendinginto the tensilestress area
11/09/99 APPENDICES 18113-38
Description StressCategory
Constant Threshold Potential CrackInitiation Point