Design, Analysis and Fabrication of Welded Structures

INTERNATIONAL INSTITUTEOF WELDING

INSTITUT INTERNATIONAL DE LA SOUDURE

GERMAN DELEGATION DÉLÉGATION ALLEMANDE

Prof. Dr. A. HobbacherUniversity of Applied Sciences, Friedrich-Paffrath-Str. 101, D-26389 Wilhelmshaven, Germany

Tel. +49 4421 985 518, Fax +49 4421 985 403, e-mail: [email protected]

XV-1152-03

COMMISSION XV

Design, Analysis and Fabricationof Welded Structures

MINUTES OF THE COMMISSION XV MEETINGAT THE IIW ANNUAL ASSEMBLY

IN BUCHAREST, ROMANIA6 - 9 July 2003

Final version

Chairman: Prof. A. Hobbacher (Germany)Vice Chairman: Dr. J. Gerald (France); Prof. K. Horikawa (Japan)Secretary: R. Shaw (USA)

Schedule of plenary meetings of Commission XV:Day Date 8.30 - 12.30 am 14.00 - 18.00 pmMon 7 July 1. MeetingTue 8 July Com. XV invited to JWG

X-XV meeting2. Meeting jointly with com. XIII

Wed 9 July 3.1 Meeting jointly with com. X3.2 Meeting (16.00-18.00)

IIW Comm. XV XV-1552-04 page 2

Meeting on Monday, 7 July 2003 (14.00 to 18.00)

1. GENERAL QUESTIONS

Opening

Prof. Hobbacher opened the meeting with a welcome for the attendees to the CommissionXV meeting at 14:05.

Appointment of a Drafting Committee

Bob Shaw was approved to serve as the drafting committee, by concensus.

Approval of the final Agenda (XV-1130-03)

The Agenda was reviewed and adopted by concensus.

Minutes of the 2002 Annual Assembly in Copenhagen (XV-1126-02)

Adopted by concensus.

Annual Report of Commission XV for 2003 (XV-1128-03)

In the period 2002-2003, 17 meetings of working groups took place. They have beenattended by 45 participants from 10 countries. The chairman of he commission (Hobba-cher) was re-elected for the next three years. The distribution of documents by email wassuccessful and will be maintained.

XV-A (statically loaded components)– Design codes for high-strength steel have beencollected and are being reviewed.

XV- E (tubular structures)– The fatigue recommendations for tubular structures have beencompleted. They are on the way to ISO as a technical report. Static strength and highstrength steel are now under new consideration.

JWG XV-XIII (fatigue)– There has been discussion of various papers as the joint meetingswith Comm XIII. Recommendations on FEA at structural hot spot stress analysis inpreparation. Update of the IIW Fatigue Recommendations is in final state and ready forresolution.

JWG X-WV (RSDP) -- Round robin tests for computational prediction of residual stressesand distortions are being planned and underway. Computation, measuring and experimen-tal verification by test specimens are planned.

JWG X-XV (seismic) – The document “IIW Recommendations for Assessment of Risk ofFracture in Seismically Affected Moment Connections” has been completed and approved.

XV- WG9 (economy) – For calculative optimization of welded structures, new cost


functions have been refined. Several case studies have been presented. A comparison ofeconomy between bolted and welded frames was performed.

XV- WG11 (repair) – Case studies and reports are being collected. A workshop on repairis planned for Osaka.

The structure of Commission XV was reviewed. The following groups are without a chair:• SC XV-F on interaction between fabrication and design)• WG-8 on welded details• SG-1 on assembly of welded structures• SG-2 on ecological aspects

Review of the List of Members (XV-1129-03)

Some problems with certain e-mail addresses have been discussed. The documents will bedistributed according to the address list. It is the duties of the attendees and/or membersocieties to review and correct as needed.

Check on Working Documents (XV-1131-03)

For ISO publications, IIW has requested that drawings be in vector format, not bitmapformat. This will be further investigated by file extension.This is not necessary for internalIIW documents and for documents in Welding in the World.

The list of documents was reviewed for those distributed, those not distributed, or dis-tributed very late. Members encouraged to submit documents at least two weeks inadvance of meetings.

General remarks on Working Program by the Chairman

General Frame• Development of design and analysis of welded joints and structures• Operational design and metallurgical aspects of fabrication and erection• Maintenance inspection and repair and strengthening of welded structures• economical and ecological aspects of design, fabrication erection and maintenance

XV-A (statically loaded components)• calculation of welded high-strength steel structures• updating recommendations on analysis on analysis of statically loaded welded

components• revision of ductility requirements, especially for high strength steels• material toughness requirements (in collaboration with Commission X)

XV-E (tubular structures)• design and analysis of statically and fatigue loaded structures• tubular structures made of high strength steels

SC-F (interaction between fabrication and design)


• SC is now in “stand by” condition

SC-G (seismic design)• Recommendations and case studies on seismic engineering of welded structures

JWG X-XV (RSDP)• calculative prediction and control of residual stresses and distortions

JWG XIII-XV (fatigue design and analysis)• recomendations for design and analysis of welded joints and components

WG-8 (welded details)• catalogue of welded details and their relative merits under various points of view

WG-9 (economical aspects)• methods considering econical aspects• case studies for optimization• problems related to design, fabrication, erection and maintenance costs

WG-10 (FEA at static load)• elastic and plastic FEA of welded structures• loads, stress definitions, etc.

WG-11 (repair)• recommendations on inspection, repair and strengthening of welded structures• repair and strengthening of bolted connnections

SG-1 (assembly of welded structures)• problems concerning assembly, erection and removal of welded structures

SG-2 (ecological aspects)• ecological aspects related to design, fabrication, erection, removal and recycling

2. CALCULATION, DESIGN AND FABRICATION

Activities of SC XV-A "Analysis of Statically Loaded Welded Components" by SCChairman N. GRESNIGT

XV-1132-03 Annual Report of Subcommission XV-A - Analysis of staticallyloaded welded components (N Gresnigt )

The main task is to update the "old" IIW recommendations on the design and calculationof fillet welds. A survey was carried out of present rules and standards on weld design andcalculation, and contributions were received from Canada, Sweden, Germany, the USA(AWS and AISC) and Eurocode 3. Other countries are to follow. The results so far are laiddown in "Update on design rules for fillet welds" (IIW Doc. XV-A-18-2003).


A preliminary proposal for the set-up of new design rules for the calculation of fillet weldshas been discussed. The questionnaire on fillet weld design, quality requirements andresearch in various countries has discussed, finalised and sent to members of the Subcom-mission. Research into the factors that govern the strength and deformation capacity offillet welds and simple connections with fillet welds is encouraged. Such research isnecessary to achieve the main goal of the Subcommission: the set-up of better design rules.

3. ECONOMY

Annual report of Working Group XV-9 "Fabrication and Economical Aspects in Designof Welded Structures and Details" by the Chairman J. JARMAI.

XV-1137-03 Annual report of WG XV-9 - Fabrication and Economical Aspectsin Design of Welded Structures and Details (Jármai).

The Working Group met on Sunday, 6 July. The main topics of the Working Group are thefollowing:

• to elaborate new cost functions for cost minimization• to use stability, stress, deflection, etc. constraints for design• to introduce new structural models• to use new mathematical models, finding the best

A successful conference on fabrication and economy was held entitled the InternationalConference on Metal Structures, ICMS 2003 at the University of Miskolc, Hungary 3-5April, 2003. Proceedings are available from Millpress Science Publishers, Netherlands,www.millpress.com, ISBN 90 77017 75 5.

Upcoming conferences include:

International Symposium on Tubular Structures, ISTS10, September 18-20, 2003, Madridhttp://www.ictubular.es/ists10/

International Cost Engineering Council, 18th ICEC Congress and 4th World Congress, 17-21April 2004, Cape Town, SAhttp://www.be-events.co.za/index.html

2nd International Conference on Structural Engineering, 5-7 July 2004, Cape Town, SAhttp://www.ebe.uct.ac.za/~semc2004

XV-1144-03 Optimum design of a belt-conveyor bridge constructed as a weldedring-stiffened cylindrical shell (Farkas, Jarmai, Virag)

In the structural optimization of a ring-stiffened cylindrical shell, the unknown variablesare the shell thickness as well as the thickness and the number of flat rings. The shelldiameter allows for a belt-conveyor structure inside of the shell. The uniformly distributed


normal load consists of dead and live load. The design constraints include the local shellbuckling strength, the panel ring buckling, and the deflection of the simply supportedbridge. The shell thickness does not depend on the number of ring stiffeners. The costfunction includes both material and fabrication costs. The fabrication cost function isformulated according to the fabrication sequence and includes the cost of forming of shellelements into the cylindrical shape and the cost of cutting and welding the flat plate ring-stiffeners. The optimum number of ring stiffeners is calculated .

Motion by Costa to submit for publication as a Class A document, subject to editorialreview by the chairs of the Working Groups: XV-1144-03, entitled “Optimum design ofa belt-conveyor bridge constructed as a welded ring-stiffened cylindrical shell” (Farkas,Jarmai, Virag). Passed 8-0-0 as RESOLUTION #1.

XV-1145-03 Optimum design and cost calculation of a simple frame with weldedor bolted corner joints (Jarmai, Farkas, Uys)

A single bay, one story steel planar frame is constructed from rolled I-profile elementsconsisting of universal columns and a universal beam. The buckling strengths of thecolumns and beam, according to Eurocode 3 (2002), constitute the design constraints. Thebeam and column profiles are optimised to minimize the structural mass subject to thedesign constraints for both a flush-end-plate bolted (semi-rigid) structure and a welded(rigid) structure. The structure is subjected to a horizontal force and a uniformly dis-tributed vertical load. Comparing the costs of these optimal solutions shows that the boltedframe is 7% or 13% cheaper than the welded frame, on the basis of British and SouthAfrican cost data, respectively.

It can be concluded that the bolted connections are more economic than the fully weldedones. However, the calculation is very sensitive to the given data concerning productiontime. These data are different in various companies and countries as well. The scatter canbe relatively large between solutions, but making the calculation for a given frame usingactual time and cost data, one can get the result and can choose the type of connection.Because the rotational stiffness of semi-rigid bolted connections is smaller than that ofwelded ones, the maximum bending moment in an unbraced frame structure is smaller andthe beam section can be smaller. The difference between the fabrication costs is significantas well. The disadvantage of bolted connections is the very complicated calculation ofrotational stiffness. This causes difficulties in the optimum design of frames with semi-rigid beam-to-column connections.

Motion by Costa to submit for publication as a Class A document, subject to editorialreview by the chairs of the Working Groups: XV-1145-03, Optimum design and costcalculation of a simple frame with welded or bolted corner joints (Jarmai, Farkas, Uys).Passed 9-0-0 as RESOLUTION #2.


Meeting adjourned for the day, 5:40 pm.

Meeting on Tuesday, 8. July 2003 (14.00 to 18.00)

JOINT MEETING WITH COMMISSION XIII "Fatigue of Welded Components andStructures

4. DESIGN OF WELDED TUBULAR STRUCTURES

Activities of SC XV-E "Welded Joints in Tubular Structures", by SC Chairman Zhao X.L.(G. Davies reporting)

XV-1133-03XIII-1981-03

Annual Report of Subcommission E - Welded Joints in TubularStructures (Zhao X.L. / J. Jarmai reporting)

Since the last Annual Report, the Subcommission has met twice: in Kumamoto University,Japan, 3 June 2002 and at Hotel Le Pigonnet, France, 30 September 2002. No meeting ofthe Subcommission is being scheduled in conjunction with the IIW 2003 Annual Assem-bly. The next meeting is scheduled for 20 September 2003 in Madrid, Spain after the 10thInternational Symposium on Tubular Structures.

Mr. Glenn Ziegenfuss, IIW Standards Officer, has forwarded the subcommission resultsof the ISO DIS ballot on ISO 14347 draft prepared by the subcommission. This ISO draftwas based on IIW Doc. XIII-1804-99 and IIW Doc. XV-1035-99. The ballot passedunanimously with comments provided by ANSI (USA) and BSI (UK). The Subcom-mission prepared replies to ANSI and BSI's comments. The Subcommission also preparedthe final draft (IIW Doc. XV-E-03-276) after incorporating all the actions listed in IIWDoc. XV-E-03-274 and IIW Doc. XV-E-03-275, and all other minor comments receivedin the last 2 years. The above three documents (IIW Doc. XV-E-03-274, IIW Doc. XV-E-03-275 and IIW Doc. XV-E-03-276) have been submitted to Mr. H. Glenn Ziegenfuss forprocessing to ISO as a final draft for balloting at the FDIS. The voting was carried outaccording to IIW rules. It passed 11-0-0 as RESOLUTION #3.

The next major task of the subcommission is to update the IIW Static Strength Recommen-dations for Welded Tubular Joints to incorporate research results in the last 13 years. Themajor items that require updating were identified as CHS to CHS joints:

1. Plate to CHS or RHS joints 2. Reinforced joints 3. Multiplanar joints 4. Loading cases 5. Validity range of parameters 6. High strength steels

This third edition will be formatted at the outset as an ISO draft specification, but still


submitted for approval via IIW, in the same manner as has been done for the fatiguestrength recommendations. The second draft is under preparation and will be discussed atthe next subcommission meeting to be held in Madrid, Spain, 20 September. It is expectedthat the third draft be distributed at the 2004 IIW Annual Assembly to be held in Osaka forvoting by National delegates to IIW Commission.

No technical documents were submitted.

5. FATIGUE DESIGN

Activities of JWG XIII-XV "Calculation of Welded Joints Subject to Dynamic Load", byJWG Chairman A. HOBBACHER

XV-1136-03XIII-1988-02

Annual Report of Joint Working Group XIII-XV - Calculation ofWelded Joints Subject to Dynamic Load (A. Hobbacher et al.)

In the last period, two meetings have been organized, at the IIW Annual Assembly inCopenhagen, Denmark, 23 June 2002 and the interim meeting in Lappeenranta, Finland,2.March 2003. The main focus of the work of the group was the updating of the IIW FatigueDesign Recommendations (Doc. # XIII-1965-03 / XV 1127-03). The discussions havereached a final state and so a basic resolution can be made. Finetuning and editorialsmoothening can be done later. Several items have been and are currently in the center ofdiscussions, as follows:

1. Improved recommendations on structural stress (Niemi / Fricke)2. Introduction of post-weld improvement techniques (Haagensen / Maddox)3. Review and discussion of detail catalogue jointly with the Eurocode bodies4. Review of the effect of residual welding stress on fatigue5. Recalculation of tables for simplified assessment of cracks6. Expansion of notch stress method to aluminium7. Refined statistical procedures for testing and evaluation8. Consistency of different assessment methods

Still in discussion are two topics:1. More detailed consideration of complex loading problems2. Questions of cumulative damage calculations

XV-1127-03XIII-1965-03

Recommendations for Fatigue Design of Welded Joints and Compo-nents(Hobbacher)

The aim of the Recommendations is to provide a basis for the design and analysis ofwelded components loaded by fluctuating forces, to avoid failure by fatigue. In additionthey may assist other bodies who are establishing fatigue design codes. It is assumed thatthe user has a working knowlegde of the basics of fatigue and fracture mechanics.


The recommendations present general methods for the assessment of fatigue damage inwelded components, which may affect the limit states of a structure, such as ultimate limitstate and servicability limited state. They give fatigue resistance data for welded compo-nents made of wrought or extruded products of ferritic/pearlitic or bainitic structural steelsup to fy=960 MPa, of austenitic stainless steels and of aluminium alloys commonly usedfor welded structures. The recommendations are not applicable to low cycle fatigue, whereFnom > 1.5Afy , max Fnom > fy, for corrosive conditions or for elevated temperature operationin the creep range.

Motion by Shaw to publish as a Class B document, subject to final editorial correctionsand clarifications by the concerned WG Chairman of Commissions XV and XIII, and theChairmen of Commissions XV and XIII. Passed 22-0-0, as a combined vote of delegatesof Commissions XV and XIII as RESOLUTION #4.

6. FATIGUE OF WELDED STRUCTURES

XV-1147-03XIII-1996-03

Economic study on fatigue design of the effect of hammer peeningtreatment in welded joints (C. A. Moura Branco, V. Infante)

An economic study for the fatigue design of a welded structure was carried out whereimprovement techniques were compared in terms of minimum cost design. The case studywas a simply supported beam subjected to fatigue loading. Three different conditions wereanalysed: (1) as-welded structure, (2) hammer peening of all weld details, and (3) hammerpeening of selected critical details. The hammer peening conditions are illustrated by theminimization of the cost function that contains an additional cost factor for the appliedtreatment. In optimum design, by minimizing a cost function, safety is guaranteed, butinclude design constraints on strength and fabrication.

Post-welding treatment diminished the optimum dimensions, giving a substantial reductionof costs. Comparing the three situations, the cost of the as-welded structure alone is greaterthan that of hammer peened structures. Hammer peening of all welds reduced the cost by10-13%, and hammer peening critical details only provided a cost reduction of 18-20%.

XV-1146-03XIII-2000-03

Fatigue capacity of fillet welded connections subjected to axial andshear loading (I. Lotsberg)

The objective of this work is to develop a suitable methodology for fatigue assessment offillet welds subjected to simple or complex normal and/or shear stresses in relevantFloating Platform Storage Offshore (FPSO) details from the view point of weld throatfailure. The work is performed within the FPSO Fatigue Capacity JIP (Joint IndustryProgram).

The status on current design recommendations concerning the fatigue capacity of filletwelds was presented by Dr. Maddox (2002), based on a literature survey. In order toexamine the validity of the recommendations and to supplement the fatigue test data base,a test matrix with 33 specimens was developed. This included 8 simple fillet welded


cruciform joints that were subjected to axial loading and 25 fillet welded tubular speci-mens that were subjected to axial load and/or torsion for simulation of a combined stresscondition in the fillet weld. The test data are also compared with design guidance fromIIW (1996), Eurocode 3 (1993) and Det Norske Veritas DNV-RP-C203 (2001).

Based on this work the following conclusions can be drawn:

• There was no evidence from the fatigue test results to indicate that there is athickness effect related to the size of the fillet weld or the main plate thickness.

• The equation for the stress concentration factor at the roots of fillet welds incruciform joints to allow for misalignment-induced bending presented by Mad-dox (2002) was found to be reasonable.

• The test data with pure tangential shear in the fillet weld indicated that IIW andEurocode are conservative by a factor of 10 on life for this loading condition.However, they were in reasonable agreement with the mean line of DNV-RP-C203.

• The mean S-N curve fitted to the results for pure tangential shear in the filletweld had a slope in between those of the IIW/Eurocode and DNV-RP-C203.

• The ratio of Fmin/Fmax with respect to parallel shear stress does not seem to havea significant effect on the fatigue life.

• Based on a comparison with the test results obtained for combined stresses in thefillet weld, the design procedure in IIW and Eurocode was found to be on thesafe side.

• Comparison of the same data with the design procedure in DNV-RP-C203showed it to be marginally on the safe side for the endurances considered. Theapproach in DNV-RPC203 for combined stresses becomes more conservativecompared to IIW and Eurocode with a higher number of fatigue cycles.

7. STRUCTURAL STRESS APPROACH AND FINITE ELEMENT METHODS

Activities of the combined group WG XV-10 and WG XIII-3 on finite element analysis byMr. Fricke.

XV-1138-03 Annual Report of WG XV-10 and WG XIII-3 (Fricke)

After the Annual Assembly of IIW 2002 in Copenhagen, where W. Fricke was appointedas Chairman, one interim meeting was held in Lappenranta/Finland on March 11, 2003

The editorial group (E. Niemi, S.Maddox, W. Fricke) finalised the Structural Hot-spotStress Approach To Fatigue Analysis Of Welded Components - Designer’s Guide (XV-1090-00, XIII-1810-01 by E. Niemi). In addition to several minor modifications andclarifications by inserting overview figures and tables, the chapters were re-arranged tokeep all information on finite element analysis together. Furthermore, recent developmentssuch as the structural stress method by P. Dong, were discussed and addressed briefly inone subchapter.


The WG contributed mainly to three topics of the updated IIW Fatigue Recommendations:• Finite element modelling to determine structural hot-spot stresses• Application of the structural hot-spot stress approach to cases with post weld

treatment• Consideration of stress magnification due to misalignment in the structural hot-

spot approach

For future work, the proposal has been made to prepare a guidance on the effective notchstress approach,

XV-1151-03 Finite element calculations and assessment of static stresses in loadcarrying fillet welded joints (Fricke et al)

Fillet welds have to be designed with a sufficient strength with respect to static as well ascyclic loads. The present paper deals with the calculation of the relevant stresses for staticstrength, which are usually assessed regarding the ultimate load-carrying capacity of theweld. After reviewing the current procedure, where nominal stress components in the weldthroat are determined analytically, the application of the finite element method is demon-strated by the example of a fillet-welded lifting-eye. The stresses from coarse and finemeshes are compared with the analytical results. High stress peaks are observed in finemeshes. Some problems occur when deriving the nominal stress components in the weldfrom the element stresses in the finite element models. A non-linear calculation with thefine-mesh model shows the redistribution of stresses after yielding, where the high stresspeaks resulting from the linear stress analysis disappear. Finally conclusions are drawnwith respect to the calculation of nominal stress components in fillet welds from finiteelement models, which can be used in the subsequent strength assessment of the welds.

Coarse 3D finite element meshes, where the fillet weld is represented by only one or twosolid elements in the cross section, yield results which may under-estimate the stresses inthe weld by more than 50 %, if these are derived from the stresses only in the weldelements or in the opposite elements in the plates. This is due to the fact that the nodalforces between the elements create also stresses in the adjacent elements at the root gapwhich have to be considered when calculating the averaged weld stresses. Even in thiscase, the differences can still be relatively large, as the example has shown. Reliablestresses are only derived from nodal forces acting in a section through the weld andreferred - as usual - to the throat thickness.

The equivalent stresses calculated in accordance with the codes show large differencesbetween the analyses. Particularly the analytical formulae yield high stresses at the endsof the weld under in-plane bending and torsional loads, which would result in a con-servative design. Here, the finite element analysis gives more realistic values, as far as thestresses are averaged through the weld throat. A further stress redistribution along thewelds due to yielding can increase the load-carrying capacity considerably. However, itsutilization in design is questionable due to uncertainties related to modelling aspects aswell as possible weld imperfections.


XV-1140-03XIII-1977-03

Experimental Investigation and Finite Element Analysis of T-Joint Profile under Axial Loading (M. Haghpanahi and A. Ravan)

Increasing progress in computer science and related software have made finite elementmethods one of the most efficient tools in analyzing welded joints. For a precise verificati-on of the experimental results, a FEA seems to be essential. An experimental and numeri-cal investigation of strains in welded T-joints profiles under axial loading was performed.It is a practice to model a welded T-joint using isoparametric brick elements for thebrace/chord intersection region, including the weldment. However, it is an extremelytedious procedure to use mapped solid elements and a sufficient merge condition at allnodes lying on the interface between the weld toe and profile. The study also provides thesensitivity analysis of different weld toe models and sizes. The obtained experimentalresults were in good agreement with the FEM results, showing that modeling based onsolid elements using a mapped mesh method can be used as an efficient method to modeljoint profiles. A model based on the consideration of weld region and brace as a unitedvolume is suggested, using fewer elements, causing less error yet has a high reliability.Despite all experimental errors (operator errors, design tolerances…) the numerical resultswith within an acceptable engineering tolerance.

XV-1148-03XIII-1991-03

Determination of the structural hot spot stress using the finite ele-ment method - a comparison of current procedures (I. Poutianen, P.Tanskanen, J. Martinsson, M. Byggnevi)

Three methods for determining the structural hot spot stress for fatigue analysis of weldedstructures are evaluated: (1) linear surface extrapolation (LSE), (2) through thickness atthe weld toe (TTWT), and (3) Dong method. The methods were used to evaluate finiteelement analysis limits and accuracy obtained for a simple 2D structure, a 3D structuraldetail and for complex 3D structures in an industrial application. LSE and TTWT arebased on normal stresses while the Dong method also requires that shear stresses aregenerally correct. For 2D models, TTWT and Dong gave uniform results for virtually allmesh variations used in this study. Good results for LSE were obtained when using near-equal sided elements. For 3D structures, the Dong method requires more care duringmeshing and is numerically more demanding than other methods during post processing. When TTWT is used for 3D structures, the computed structural stress is virtually identi-cal to that found using Dong, but the meshing requirements are somewhat easier and thepost processing requires only that nodal averaging be considered.

XV-1149-03XIII-1993-03

Equivalent structural stress approach to fatigue analysis of a tubularjoint - Case study with fatigue challenge by the SAE Fatigue evalua-tion and design committee (H. Kyuba, P. Dong, J.K.Hong, presentedby N. Chen)

The Equilibrium-Equivalent Structural Stress method has been recently developed throughseveral joint industry projects as a robust method to analyze welded components using thefinite element method. This method has demonstrated its effectiveness in correlating theprevious fatigue test results available in the literature. The authors employed this


Equilibrium-Equivalent Structural Stress method for a competition organized by the SAEFatigue Design & Evaluation Committee to predict the fatigue life of a tubular joint.Among all the methods used by many participants, the authors’ life prediction was selectedas the best, based on actual test results. This paper provides the details of the SAE fatiguechallenge problem definition, test results, and our structural stress approach. The predictedmean life by the Equilibrium-Equivalent Structural Stress method utilizing the proposedASME Div. II Structural Stress curve achieved excellent agreement with the mean life ofthe experimental results. Other stress indexes (such as the maximum principal stress andthe von Mises stress) had maximum stress at a location different from the crack location.Furthermore, the Equilibrium-Equivalent Structural Stress showed significant meshtolerance with only a few percent difference in stress when halving the mesh size.

Additional parametric investigations were also performed to examine other stress para-meters and weld representation issues. Some of major findings were:

1) The E2S2 can adequately capture failure location and provide a good life predicti-on to the rather complicated tubular joints under complex loading;

2) The E2S2 parameter showed an excellent insensitivity to mesh sizes and elementtypes;

3) The simple representation of the weld in shell models is proven to be adequatethrough the comparison between the shell and solid element results;

4) In general, a shell model with the weld profile is recommended for using theE2S2 method because it provides a good approximation in representing actualload transfer mechanisms in complex joints;

5) It is difficult to use the conventional FEA stress outputs such as the maximumprincipal stress and the von Mises stress at the weld toe locations since theyshow the maximum values at the location different from the actual failure loca-tions detected in experiments and since they show their strong mesh/elementsensitivities.

Meeting on Wednesday 9 July 2003 (14.00 - 18.00)

JOINT MEETING WITH COMMISSION X "Structural performance of weldedjoints, fracture avoidance" (14.00 - 16.00)

8. RESIDUAL STRESSES AND DISTORTION

Activities of JWG XV-X "Residual stresses and distortion prediction and control", by J.JANOSCH

XV-1135-03X-1535-03

Annual Report of Joint Working Group X-XV - Residual Stressesand Distortion Prediction and Control (J. Janosch)

JWG meeting was held 8 July 2003 from 8:30 - 12:30. The current working programincludes:

(1) Eexecution of a second phase of round robin, made in 2D and 3D so as to define the


standard IIW procedure used for predicting the residual stress state and the distortion inwelded structures. The results of the 2D (dimensional) simulation were presented last yearduring the IIW assembly in Copenhagen. The new 3D protocol (doc IIW-X/XIII/XV-RSDP-075-03) was sent to the members in January 03. It represents the 3D application ofthe GTAW welding process of the butt weld in an austenitic stainless steel plate. The newobjectives are to predict in 3D the residual stress distributions and the global distortion ofthe assembly. Final report will be presented in Osaka in 2004. Jean Jacques Janosch isleading this action.(2) Execution of a experimental Round robin of Residual Stress measurement made ofWelded reference plates (used for the Theme 1) in order to draft a guideline on utilisationof existing methods and evaluating “performance and limitation” of each technology. Mostof the activity in 2003 was dedicated to the welded assembly manufacturing. This actionis leaded by CEA and is also providing the plates and realizing the welding. Three firstwelding assemblies will be available for Summer time. This action is led by Prof. Wohl-fahrt.(3) Drafting of a compendium to collect and identify the existing numerical or experimen-tal data, in order to constitute a collection of normalized IIW Doc with profiles of residualstresses and distortion in welded assemblies (fillet welds, butt welds, branch pipes, pipes,etc.). This action is led by Pingsha Dong.(4) Definition of a reference guide for Design Departments.

XV-1141-03 First 3D modelling results on residual stress, Report of Round RobinTest Phase II (IIW-X-XII-XV-RSDP-77-03) (J. Janosch)

The round robin phase II began with a 2D modelling application (IIW-X/XV-RSDP-60-01) and was essentially designed to take into account the lessons learn from the firstexercise. The objectives were to provide a “rigorous”, accurate and adapted experimentaldatabase to the partners to predict in 2D the GTAW welding process of a butt weld in anaustenitic stainless steel The expected results were the prediction of the thermal cycles,residual stress distributions and distortion of the plates. As compared to the first exercise,the analysis of the results (IIW-X/XV-RSDP-68-03) evidenced a significant improvementof the quality and homogeneity of the results. Nevertheless, some differences in resultswere still present on thermal cycles and residual stresses distributions. The first analysisevidenced that these variations should be linked with: (1) the modeling method of thewelding heat input which affects the thermal cycle - influence of heating slopes andcooling slopes, and the maximum peak temperature value, (2) mesh size effects near thenotch (weld toe & root) which affect the peak stress, (3) the mechanical model used for the3rd dimension, and (4) remelt zone history of the first weld by modeling the seconddeposit (strain history).

The second part is to continue the round robin action with a 3D modelling. Document IIW-X/ XIII/XV-RSDP-75-03 presents the 3D modelling protocol of the GTAW weldingprocess application previously used for the 2D simulation. The objectives are to predict,in 3D, the residual stress distributions and distortion. The modelling results will be thencorrelated with the experimental measurements realized in parallel by RSDP experimentalround robin action.


XV-1142-03 Experimental Residual Stress Measurement, Round Robin Report(IIW-X-XIII-XV-RSDP-78-03) (H. Wohlfahrt)

Prof. Wohlfart summarized the proposed research using three welded austenic stainlesssteel plates, identifying the nine to ten laboratories that will be participating and whichmethods each participant will be using - X-ray, neutron-D, hole drilling, deep-hole dril-ling, sectioning, and perhaps holography (Paton).

XV-1143-03 Compendium of Residual Stress, Report (P. Dong, USA)

This document summarizes the residual stress distributions based on the on-going X-XIII-XV joint working group (JWG) round robin efforts on the compilation of the existingresidual stress distributions for welded joints initiated two years ago within the IIWcommunity. The present focus is on the residual stress distributions in pipe and vesselwelds, since more rigorous validations are mostly available in these applications inperforming structural integrity assessments. Based on the submissions from some of theparticipants in the IIW RSDP joint working group and publications in open literature todate, the residual stress distributions in pipe and vessel welds can be compiled based ontwo important categories: (a) self-equilibrating dominant type and (b) bending dominanttype. Various available and credible residual stress solutions collected to date are thendocumented based on such a categorization. To facilitate the interpretation of the residualstress results documented, additional explanations on the underlying mechanics thatconnects the two important types of residual stress distributions were presented.

The following important findings as far as girth welds are concerned, although detailedparametric relationships still remain to be developed through both on-going and futuredevelopment efforts:

(1) Two characteristic residual stress distributions exist in girth welds in terms ofthroughthickness axial residual stresses. One is of bending-dominated type; andthe other is of self-equilibrating dominated type,

(2) Hoop residual stress distributions tend to be relatively invariant due to typicallyhigh restraint conditions in the hoop direction. To a large extent, overall through-thickness distribution of the hoop residual stress distributions can be related toaxial residual stresses, in addition to their equilibrium requirements in the hoopdirection, and

(3) Among the various parameters examined, pipe radius plays the most critical rolein determining the overall bending content of a given residual stress distribution.To a less degree, pipe wall thickness and number of passes further contribute tothe bending content. Weld pass sequence and heat input per pass mostly con-tribute though-wall variations in a localized manner for typical applications.

9. EARTHQUAKE STRUCTURAL ENGINEERING

Activities of SC XV-G "Fundamentals of seismic design and fabrication of weldedstructures", by SC Chairman G. DAVIES, reported by R Shaw


XV-1134-03X-????-03

Annual Report of Subcommission G - Interaction of SeismicDesign and Fabrication of Welded Structures (G. Davies)

The activities of SC XV-G have been entirely devoted to developing the report “IIWRecommendations for Assessment of the Risk of Fracture in Seismically Affected MomentConnections”, XV-1102-02, X-1504-02. That task has been completed. Minor editorialimprovements to text and tables have been incorporated in the final version submitted inMarch 2003. Prof. Burdekin will be giving the final lecture at the IIW InternationalConference on Thursday entitled “Selection of Materials for Avoidance of Fracture inWelded Steel Moment Frame Structures Subject to Seismic Loading.”

It is the recommendation of XV-G to discontinue the JWG with Commission X. SC XV-Gshould continue. The position of chairman of XV-G is uncertain at the moment, but willbe resolved soon. A working program will be prepared and presented in Osaka.

XV-1150-03 Full scale testing of beam-to-column connections with partial jointpenetration groove welded joints) Azuma K, Kurobane Y, Dale K,Makino Y)

This paper concerns the applicability of partial joint penetration (PJP) groove welds forbeam-to-column connections. Two full-sized beam-to-column connections with PJPgroove welds at the ends of the beam bottom flanges were tested under cyclic loads. Whenthe unfused regions created by PJP groove welds were reinforced by fillet welds so that thewelded joints have a sufficient cross-sectional area, ductile cracks grew stably and, inconsequence, the connections showed sufficient deformation capacity. Test results werereproduced well by non-linear FE analyses. Strains sustained at points around internaldiscontinuities were found to be low because of greater cross-sectional areas of weldedjoints compared with the cross-sectional area of the beam flanges. Fracture toughnessproperties of numerically modeled connections were evaluated by using a recently develo-ped fracture mechanics approach.

Both the test results and the fracture mechanics-based assessment demonstrated that it isunlikely to initiate brittle fracture at these discontiuitites. Strain and de-flection measure-ments as well as FE analysis results showed that strains sustained at the end portions of thebeam flanges before cracks extended significantly were about equal in magnitude irrespec-tively of the specimen type. Nevertheless, crack growth and failure behavior variedsignificantly with the details of connections.

A modified fracture mechanics approach was examined on two full-scale connectionsusing strains obtained by FE analyses. The method was found to be applicable; the predic-tions happened to exactly coincide with the test results. However, some difficulties in theproposed approach lies in how to evaluate the effect of plastic constraint and of ductilecrack growth. The connections and loading conditions had to be represented by reproduci-ble numerical models, because the method requires local strains at points where flaws existon the assumption that no flaw exists. Further experimental verifications to evaluate thefracture toughness of various joints with weld defects are required to make the proposedassessment method more reliable.


10. ASSEMBLY, REPAIR AND ECOLOGY

Annual Report of com. XV Study Group on “Repair of Welded Components” by ChairmanR. SHAW.

XV-1139-03 Annual report of SG XV on Repair of Welded Components (Shaw)

Since formation as a study group, three meetings have been held. An organizationalmeeting was held in Ljubljana on 8 July 2001, and a follow-up meeting was held in Tokyoon 3 April, 2002. A brief meeting was held in Copenhagen to refine the Working Program,as below. The meeting scheduled for Bucharest was cancelled because of lack of time.Efforts have focused on securing and distributing documents relative to the subject matterto interested participants in the Working Group, and documents have been made availableon a page at www.steelstructures/IIW_files/IIW-XV-WG11.htm. All attempts to secure theprevious files collected by Biskup have failed. Many more documents are needed beforea focused effort can be made to thoroughly review and update the Biskup paper of 1988.The Working Group intends to solidify the participation and assign specific portions tointerested individuals. This will enable the detailed review of the Biskup document byindividual section, and allow for follow-up dissemination of information.

1. Review and update Biskup 1988 paper “Recommendations for repairs and/orstrengthening of steel structures”, as needed.

2. Exchange information in codes and standards, standard practices, and researchdata in several topics related to repair

3. Publish design guidelines, as appropriate, addressing the above topics4. Collect and publish case studies of examples of repair and/or strengthening of

existing structures affected by corrosion, overload, impact or fire, using print,CD or internet

5. Provide review and comment on section 5.5 (Repair) of IIW “Recommendationsfor Fatigue Design of Welded Joints and Components”

6. Hold a workshop jointly with Commission XIII's Working Group 5 in Osaka inJuly 2004.

11. INDIVIDUAL CONTRIBUTIONS

none

12. WORKING PROGRAM

XV-1020-99 Working Program of Commission XV (Hobbacher)

The working program was reviewed. Member societies will be asked to submit applica-tions for the position of Chairman for XV-F, WG-8, SG-1. No changes to the workingprogram were proposed.

Prof. Radu Bancila of Romania volunteered to take on the chairmanship of SG-2 on


Ecology. He was duly elected under RESOLUTION #5. Motion to name Prof. RaduBancila the Chairman of SG-2. Approved 8-0-0.

13. MISCELLANEA

Future Annual Assemblies:

2004 Annual Assembly in Osaka2005 Annual Assembly in Prague2006 Annual Assembly in Quebec City2007 Annual Assembly in Croatia2008 Annual Assembly in Austria

An intermediate meeting has been tentatively scheduled for late February in Portugal, withCommission XIII..

IIW Website - Glenn Ziegenfuss (presented on Tuesday afternoon)• over 1300 documents currently downladable• over 1100 weekly visits (many more just prior to Annual Assembly)• send documents in .doc (Word) or (.pdf (Adobe)• for standardization documents at ISO, figures must be in .dxf (vectorial picture) -

no bitmaps (but this is not applicable to IIW only documents)• a new private forum feature is available for Commission, Subcommission and

Working Group activities

The Commission adjourned its business at 17:00, with thanks to the Chairman and thehope to see each other again in Osaka Japan next year.

A. HobbacherChairman of IIW Commission XV


List of Resolutions 2003IIW Commission XV

Resolution #1:

To submit the following document as a class A document for publication in Welding in theWorld, subject to an editorial review by the chairs of the working units of Com. XV:


Resolution #2:

To submit the following document as a class A document for publication in Welding in theWorld, subject to an editorial review by the chairs of the working units of Com. XV:


Resolution #3:

To transmit the following IIW document to ISO as a proposed international standard (ISOwork item: ISO/WD 14347-1) according to Route II.

XV-E-276-03ex XV-1035-99

Fatigue Design Procedure for Welded Hollow Section Joints - Part 1

Resolution #4:

To publish the following document as a class B document, subject to final editorialcorrections and clarifications by the concerned WG chairmen of the commissions XIII andXV and the chairmen of commissions XIII and XV.

XV-1127-03XIII-1965-03

Recommendations for Fatigue Design of Welded Joints and Compo-nents (Hobbacher et al.)

Resolution #5:

Prof. Radu Bancila to take the chair of com XV Study Group 2 on ecological apects.



Annual IIW Assembly 2003List of attendees of Com. XV

Name Country Position 7 July 8 July 9 JulyAgerskov, H Denmark O XAzuma, K Japan E X X XBancila, R Romania D XBaron, O Romania O XBeloev, M Bulgaria E X XBranco, C Portugal E XChapetti, M D Argentina E X XChen, N USA D XCosta, G Italy D X XDong, P USA E XFarkas, J Hungary D X XFricke, W Germany D X XGerald, J France D X X XHaagensen, P. Norway N X X XHermans, M Netherlands E XHighpanahi, M Iran E X X XHobbacher, A Germany Chairman X X XHorikawa, K Japan O XIshikawa, T Japan E XIwata, T Japan O X XJanosch, J J France E X X XJarmai, K Hungary E X X XKinomoto, T Japan E XKlobcar, D Slovenia O XKueppeus, M Germany E X XLobanov, L Ukraine D X X XLotsberg, I Norway O XMachida, F Japan E XMaddox, S UK E XMarquis, G Finland D XMartinsson, J Sweden XMateiu, H Romania O X X XMiki, C Japan E X


Milicevic, R Serbia +Mn D X X XMochizuki, M Japan O X XMori, T Japan E XMurakawa, H Japan O XNakagomi, T Japan D X X XNarström, T Sweden E X XOno, S Japan E XPanezic, S Canada D X XPartene, C Romania D XSamuelsson, J Sweden E XShaw, R USA D X X XStankovic, D Serbia+Mn E XStevanovic, R Serbia+Mn E XSuganuma, H Japan E XSzubryt, M Poland O XTakemi, K Japan E X XWoerner, W New Zealand D X X XWohlfahrt, H Germany E X X X


Kurzbericht von der IIW Jahresversammlung 2003 in Bukarest, 6.-9.7.2003

IIW Kommission XV Grundlagen der Konstruktion, Berechnung und Fertigung von Schweißkonstruktionen Vorsitzender: Prof. Dr. A. Hobbacher (Deutschland) Neben sechs Arbeitsgruppen-Sitzungen hat die Kommission an drei Tagen getagt. Es waren 49 Teilnehmer aus 28 Ländern anwesend. Insgesamt wurden zwischen den Jahresversammlungen 17 Arbeitsgruppen-Sitzungen durchgeführt. Neben den allgemeinen und organisatorischen Dingen wurden 22 technisch-wissenschaftliche Dokumente vorgestellt und diskutiert. Die Arbeitsgruppe für statische Berechnung (Gresnigt NL) konzentriert ihre Aktivitäten auf die Berechnung bei hochfesten Stählen. Zur Zeit werden Daten gesammelt und ausgewertet. Ein besonderes Problem ist die in vielen Regelwerken aufgestellte Forderung nach 15% Bruchdehnung, die bei hochfesten Stählen nur teilweise erfüllt werden kann. Die Gruppe für Rohrkonstruktionen (Zhao AUS) hat die Empfehlungen zum schwingfesten Bemessen auf das ISO-Format umgearbeitet und auf den Weg gebracht. Mit einer entsprechenden Resolution wurde die Weiterleitung an ISO beschlossen. Die weiteren Arbeiten werden sich nun auf eine Aktualisierung der 14 Jahre alten statischen Bemessungsregeln konzentrieren, wobei auch hochfeste Stähle betrachtet werden sollen. Die mit der Kommission XIII gemeinsam geführte Arbeitsgruppe (Hobbacher D) hat die Aktualisierung der IIW-Empfehlungen zu Schwingfestigkeit soweit fertiggestellt, dass sie in einer Resolution angenommen werden konnte. Verschiedene Feinabstimmungen werden noch vorgenommen. Neu sind die Einführung einer groben FEM-Elementierung beim Strukturspannungsnachweis, die rechnerische Erfassung des Effektes der Nachbehandlungen zur Steigerung der Schwingfestigkeit und der Kerbspannungsnachweis bei Aluminium. Dieses Dokument ist zur Zeit das einzige Regelwerk, welches alle aktuelle Nachweismethoden in konsistenter Weise anwenderunabhängig vereinigt. Die Arbeitsgruppe für finite Elemente hat unter ihrem neuen Vorsitzenden (Fricke D) die Arbeiten ganz auf die Elementierung beim Strukturspannungsnachweis konzentriert. Aus wirtschaftlichen Gründen werden grobe FEM-Netze angestrebt. Die Arbeiten sind soweit abgeschlossen, dass sie in die neue Aktualisierung der IIW-Empfeh-lungen zur Schwingfestigkeit übernommen werden konnten. In Zukunft sollen Empfehlungen zum Kerb-spannungsnachweis aufgestellt werden. Das Beherrschen des Verzuges und der Eigenspannungen ist für die Schweißkonstruktion fundamental. Die mit Kommission X gemeinsam geführte Arbeitsgruppe (Janosch F) befasst sich mit der rechnerischen Vorhersage. Durch internationale Ringversuche sollen die Ergebnisse von Modell-Bauteilen verglichen werden. Die erste Phase wurde bereits abgeschlossen. Sie zeigt, dass noch ein erheblicher Forschungsaufwand nötig ist. In der nun angelaufenen zweiten Phase sollen dreidimensionale Standard-Methoden entwickelt werden. Die Arbeit der Gruppe zur erdbebensicheren Konstruktion (Davies UK) ist mit der Fertigstellung des Dokuments zu Bewertung des Risikos von erdbebenbelasteten Konstruktionen in gewisser Weise abgeschlossen. Gleichwohl besteht weiter das Bedürfnis, eine Gruppe zu haben, in welcher konstruktive Probleme gesammelt und diskutiert werden können. Nächstes Jahr soll eine neuer Vorsitzender gewählt und ein neues Arbeitsprogramm aufgestellt werden. Die Fragen der Wirtschaftlichkeit der Schweißkonstruktionen werden in einer besonderen Arbeitsgruppe (Jarmai HU) behandelt. Es wurden wiederum mehrere Beispiele vorgestellt, bei denen die günstigste Ausführung mit rechnerischer Optimierung ermittelt wurde. Die Gruppe zur Reparatur von Schweißkonstruktionen (Shaw USA) arbeit eng mit der entsprechenden Gruppe der Kommission XIII zusammen. Das Ziel ist, die Empfehlungen aus dem Jahre 1988 zu aktualisieren. Zur Zeit wird Material gesammelt, das später als Grundlage für eine neue Empfehlung dienen soll. Für nächstes Jahr ist in Osaka eine größere Arbeitssitzung zu diesem Problemkreis vorgesehen. Die Arbeitsgruppe zur Ökologie der Schweißkonstruktionen wurde aktiviert. Ein neuer Vorsitzender konnte gewonnen werden (Bancila RO).

Date post:	12-Feb-2016
Category:	Documents
Upload:	taosye
View:	63 times
Download:	5 times