Residual Stresses in Welded Built-up T-1 Shapes October 1965 R

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Lehigh University

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Fritz Laboratory Reports Civil and Environmental Engineering

1-1-1965

Residual stresses in welded built-up T-1 shapes,October 1965, Reprint No. 320 (67-3)

E. OdarF. Nishino

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Recommended CitationOdar, E. and Nishino, F., "Residual stresses in welded built-up T-1 shapes, October 1965, Reprint No. 320 (67-3)" (1965). FritzLaboratory Reports. Paper 177.hp://preserve.lehigh.edu/engr-civil-environmental-fritz-lab-reports/177
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byEnver darFumio ishinoLambert: Tall

elded and RolledT-1 olumns

El

Fritz Engineering laboratory Report N00 29 08


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Welded Built-Up and Rolled Heat-Treated T-I Golumns

RESIDUAL STRESSES IN WELDED ~ ~ I L T - U P T-l SHAPES

byEnver Odar

Fumio NishinoLambert Tall

This work has been, carried out as part of aninvestigation sponsored by the United S ta te s S te elCorporation.

Fri tz E n g i n ~ e r i ~ g LaboratoryDepartment of Civil Engineering.

Lehigh UniversityBethlehem, Pennsylvania

October 1965

Fri tz Engineering Labora tory Report No. 290.8


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2.

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5.

6.

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9.

TABLE OF CONTENTS

ABSTRACT

INTRODUCTION

DESCRIPTION OF TESTSResidual Stress MeasurementsMechanical Proper ty Tes tsStub Column Tests

TEST RESULTS AND DISCUSSIONSResidua l St re ss MeasurementsMechanical Property TestsStub Column Tests

CO:MPARISON WITH PLATE RESULTS AND RESULTS OFOTHER STEELS

SuMMARY AND CONCLUSIONS

ACKNOWLEDGEMENTS

DEFINITION OF TERMS

TABLES AND FIGURES

REFERENCES

1

2

2

23

4466

7

10

11

12

14

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ABSTRACT

)\This repo rt presents the r e ~ u l t s obtained from an experimentalinvestigation of residual stresses in welded built-up columns made ofliT-I" s teel . fiT-I" s teel meets the requirements of ASTM DesignationAS140

The co lumn shapes were made by welding T-l s teel pla tes to-gether. Three welded built-up H shapes and t ~ o " w e l d e d Box shapes wereincluded in th e invest igat ion.

The investigation included residual st ress measurements, ten-si1e coupon tes ts and stub column t es t s . Comparison was made of theresidual stresses in shapes and the residual stresses in their compon-ent pla tes , and the r es idual s tr e ss e s were shown to be similar. Theknowledge of residual st ress in the cross section makes i t possible topredict the strength of a c o m p r ~ s s i o n member made of s tee l .


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1. INTRODUCTION

"Residual Stresses in Welded Built-Up Shapes Made of T-lSteel" is one phase of the research project on "Welded Built-Up and

"kRolled Heat Treated T-l Columns". An extensive study was conductedon Residual Stresses in T-1 Steel Plates, and the resul ts are presentedin Reference 1. This report gives results obtained from measuringresidual stresses in shapes made from welding T-l steel plates, andthe resul ts are compared with t ho se obt ai ned from measuring weldedplates , and also with resul ts from other steels.

Studies on the car ry ing capac it y of columns show that thestrength of axial ly loaded s tee l columns is great ly affected by the

(2 ' 3)residual stresses within th e cro ss section > This effect is morepronounced for welded sect ions (4) The theoret ical prediction ofstrength reduction in sect ions containing res idual stresses is avqil-able in m?ny sources such as in Refer ences 2 , 3, 5, and 6.

"T-I" steel is a high strength s tructural alloy s tee l produced by theUnited S ta te s S te el Corporation; i t meets the requirements of ASTMA514 and /o.r A5l7 s tee l .

-1-


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2. DESCRIPTION OF TESTS

Five shapes were included in the study. Three of th e shapeswere welded H shapes, and two shapes were welded Box shapes. Theywere made of flame-cut T-l plates , except for one 6 x 7 H shape wheresheared edge plates were used. Table 1 shows th,e shapes tested andtheir dimensions. The welding was by the automatic submerged arcwelding procedure ut i l iz ing Lincoln L70 wire and L840 f lux.

Residual Stress MeasurementsThe residual stresses were obtained by the method of section

ing(3). The holes were la id off on the sections in more than one placealong the length to c h e c ~ resul ts . Figures I and 2 show the typi-cal layo uts fo r marking and sectioning for welded H and Box shapesr espec t ive ly . The hole dimensions were s pa ce d in such a way as togive more readings at the regions where a t ransi t ion from tens i le tocompressive residual st ress was expected. The readings were taken onboth faces of the H shapes and on one face of the Box shape, since the

c o ~ p o n e n t plates were suff icient ly ~ h i n to, have uniform residualstresses throughout the thickness(7). Figure 3 shows the residuals tr es s d is tr ib u ti on in welded H and Box shapes and in their componentplates .Mechanical Property Tests

A number of tensi le coupons w e r e ~ t e s t e d to ascer ta in themechanical propert ies . The tension coupons were standard ASTM(8)_flat

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specimens. Table 2 shows the coupons included in the study and Fig. 4shows the locations from which the coupons were taken.Stub Column Tests

Five stub columns (2 ) , one f ~ o m ea ch shape , were t ~ s t e d toobtain the average load-s tra in re la t ionship for the section as awhole, and also to verify the measured residual st resses. The tes t ingset-up, procedure and the r equi red l engths were as specif ied in Reference9. Figure 5 shows a stub column ready for test ing.


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3. TEST RESULTS AND DISCUSSION

The patterns of res idual s tr e ss d i st ri bu t ion obtained frommeasurements on H and Box shapes are present'ed in Figs. 6 through 10,.The results for welded H-shapes are the readings of both to p and bottomfaces, whereas the readings shown for Box shapes are the outside facereadings only. Two sets of measurements taken from different sectionsare presented for each shape ; these show that there is l i t t l e variat ion in residual stress along the length of the shape. Table 3 givesa summary of resul ts . The resul ts are average valuee o f to p andbottom re ad ings fo r H shapes and one face reading for Box shapes.The resulting curves and the notat ion used in the Table are shown inFig. 3.

Figures 6 through 8 show the resiqual stresses for welded Hshapes. The pattern of residual stress dist r ibut ion had tensi ler es idual s tr es se s a t the junction of flange and web and a t th e flanget ip s , and compressive s t r es ses over the rest of the s hap e, e xc ep t fo rthe shape made of plates with sheared edg es, F ig . 6. The 6" x 7 11H-shape made of plates with sheared edges and the shape made of plateswith flame-cut edges showed a similar s t ress pat tern ex cep t f or theflange t ips where the residual stress pattern of one face i s to tal lydifferent from the other. This is a characterist ic pat tern result ing'from the shearing of the edges (1) There were tensile residualstresses at the junction of flange and web and a t the web ends; this

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was up to 80 ksi a t the web ends in magnitude with an average of 25 ksifor the flanges. Compressive residual s t resses covered the res t of the&hape with a ra ther constant dis t r ibu t ion and values not exceeding25 ksi , the average being 20 ksi . In shapes made of flame-cut plates ,Fig. 7, the tensi le residual s tress a t the flange t ips w ~ r e less than20 ks i , and reached 80 ks i a t the web ends on the weld metal. Thebottom face reading was not taken a t the junction of web and f lange,but the closes t measured points suggest that i t would have been over80 ksi on the weld. The compressive residual s t resses were dis t r ibutedra ther uniformly over most of the flange and web, with a n ave ra ge of20 to 22 ksi for b oth fla ng e and web. The measured resu l t s for the9" l O ~ " welded H shape are shown in Fig. 8. The t ens i le s t resseswere about 10-12 ksi a t the flange t ips and less than 40 ksi a t theweb t ip s . The compressive residual stress was spread over most ofthe flange width and web. The d is tr ib u ti on i s fa ir ly constant with avalue of 16 to 19 ksi in th e fla ng es and 6 to 8 ksi in the web. In a l lcases the difference between two sets of readings is insignif icant ,suggesting that the var iat ion of residual stress along the length ofthe shape i s rather small .

The resu l t s of measurements on welded Box shapes are shownin Figs. 9 and 10. The 6 x 6 Box shape had tensi le residual s t ressesa t the welded corners as high as 80 ks i with an average of 65 ks i .Compressive residual s t resses existed over most of the area, varyingfrom 24 to 28 ks i , with a ra ther uniform dis t r ibu t ion . In the largershape, the 10 x 10 Box, the pat tern was s imilar with tensi le r ~ s i d u a l


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stresses of 80 ksi at the four corners an d with a fair ly constant compressive residual s tr e ss d i st ri but ion throughout the ~ e s t of the section.The average compressive residual stress was about 10 - 16 ksi. In a l lBox shapes, the component plates had compressive residual stressuniformly dis t r ibuted over 80% of the to ta l width.

Mechanical Property TestsThe results obtained from some of the tension coupon tes t p are

given in Table 4 and a typical load strain relationship i s shown inFig. 11. The s ta t ic yield stress* was around 110 ksi for the couponstes ted.

Stub Column TestsA typical load-stra in relationship obtained from test ing a

6 x 7 H ~ s h a p e made of plates with fl ame-cut edges i s shown in Fig. 12.The effect of the res idual stresses pre&ent in the cross section on theload strain relationship i s seen from t he exi st ence of a rounded kneein this figure(2). The proport ional l imit was reduced below thatobtained from the tension coupon t e s t , (Fig. 11,) an d the yieldings tar ted at ~ b o u t 74% of the to ta l yield load of the cross section.This reduction confirmed the magnitude of the measured r es idual s tr es s es ,which were relat ively high, 20 - 22 ksi) for this part icular shape.

1< The "static yield s tress" is defined in Section 7, Definit ions.


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4. COMPARISON WITH PLATE RESULTS AND RESULTS OF OTHER STEELS

Welded shapes are formed from a number of plates, welded to-gether; the plates may be center-welded, both edges welded or single

e d g e ~ w e l d e d pla tes. An extensive study(l) was conducted on T-l s teelplates welded and unwelded, and i t is of in te res t to determine whetheran estimate of residual s tress existing in welded shapes can be madefrom a knowledge of the residual stress in i t s component pla tes. Thefactors affecting the poss ib le d if fe rence between residual stress inplates and shapes may be as follows:

1. The general r i se in temperature af ter welding may be differ-ent to addi t ional plates for heat flow in shape s and ,

2. Each pla te in a shape has some re st ra ining e f fec t on theother. I t may be expected tha t the effect depends greatly on the re la-t ive sizes of the pla te elements; namely the effect of res t ra ining wil lbe much more pronounced i f a small plate i s welded to a large pla te ,

d 1 d - f h - f 1 we1ded - -1 (10,11):an ess ~ r o n o u n c e t e s ~ z e s 0 pa t e s are s ~ m ~ ar .kIn th is study the plates were of almost the same size and i t

may be assumed that the effect of res t ra in t is very small. Figure 13shows the res idual s tress dis tr ibution measured in a 6" x 7 11 H-shapewith plates having flame.cut edges, and the residual s tr es s d is tr ibu -tioD measured from a number of center-welded and edge-welded plates ofsimilar geometry. The results are s imilar ; t h ~ s , the compreSSiveresidual stresses in the web and flanges of a built-up section can be


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represented by the dis tr ibution o b t ~ i n e d from measuring i t s componentplates . The tensi le s tress on the top face reading at the ju nc tio n offlange and web is less for the shape probably due to the fact that weldmetal did not penetrate far into the flange plate, wher,eas the separateplate was grooved and the beam laid in the groove. However, th e mainpurpose of th is study was to accurately determine the compressive resid4alstresses, ra ther than tens i le res idual s t resses , since it i s the com-pressive residu'al s t ress which affects the strength of compression members.The comparison of residual str es se s in a Box shape and i t s componentplate is shown in Fig. 14 . The patterns shown are the top face r eadingsof th e 6" x 6" Box and the top face re ading o f a 6" x plate welded onbot h edges . Again, the s im i l ar it y ex is ts . Thus, i t is clear that com-ponent plates have a residual stress pat tern and magnitude similar totha t in the welded bui l t -up shape made of these plates .

The results of a study on th e residual s t resses in welded A7s tee l shapes, and applicable to A36 s teel shapes, are presented inRef. 10 . I t is of in te res t to compare these results with thos e of thisstudy since the s h a p e ~ are of ident ical geometry. There is no possibil i tyof direct comparison for H-shapes) since the A7 s teel shapes were madefrom universal mi l l pla tes; however, for Box shapes the effect of flamecut t ing is almost eliminated by subsequent weld ing of the edges. Figure15 shows the residual s t resses measured in 6" x 6" box shapes of A.7 andT-l s teels . The general pat tern of the residual s tress is similar forboth s tee ls . However, ' the magnitude of compressive residual stress i ss l ightly less for A7 s teel .


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Although for T-l s tee l the value of the compressive residuals tress is s l ightly higher and is over a wider portion of the section,nevertheless, i t is a s m a ~ l e r fraction of the y ie ld s tr engt h. Theeffect of residual s tress on the ~ a r r y i n g capacity of welded b u i l t ~ u pT-I s teel columns wil l be smaller than the e f ~ e c t on the shapes made ofA7 and A36 s t e e l s ~ 2 ) .

Final ly, in comparing the re:;;idual stresses in welded 6 x 7H-shapes with res idual stresses in a rolled heat-treated 8 ~ 3 1 shape,both of T-l s teel , th e magnitude of r e ~ i d u a l s tress in the rolledheat- t rea ted shape is much lower probabl y a s a resu l t of the ,tempering

t ~ e a t m e n t . Figure 16 shows this comparison of res idual stresses inwelded built-up and rolled heat-treated ahapea(12).


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5. SUMMARY AND CONCLUSIONS

A summary of the results obtained from the experimental invest igat ion into the residual stresses in weLded b u i l t ~ u p shapes ispresented here.

The study, together with previous resul t s obta in ed fo r weldedp l a t ~ s of T-l s teel , s ~ p p l i e s a basic knowledge needed for estimatingthe s tr en gth of medium-size welded bui l t -up columns of T-l steel .

Three H and two Box ahapes were included in the study. Theshapes were buil t .up by welding T-,l s tee l plates together. The com-ponent plates had edges ei ther flame-cut or sheared and were weldedautomatically by th e submerged-arc welding process uti l izing LincolnL70 wire and L840 flux.

The fol lowing conclusions can be drawn f rom this study.1. Residual stresses in component plates give a close re

presentat ion of the res idual s tre ss es in the shapes themselves. (Sec.3, Figs 13, 14.)

2. Welded built-up T-I s tee l shapes have r es idual s tr e ss e sconsiderably higher than r ol le d h ea t-t re ate d T -l s tee l shapes. (Sec.3, Fig. 16.)

3. Residual stresses in welded b u i l ~ - u p s teel sections aresl ight ly higher in magnitude th an tho se in welded built-up shapesA7 s teel . Since they const i tute a smaller fraction of the yield strengthfor T-l s teel , i t is expected that the strength of T-l s tee l compression

m e m b e r ~ should be affected less by the i r presence. (Sec. 3, Fig. 15.)-10-


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6. ACKNOWLEDGEMENTS

This study has been carried out as, a part of th e researchproject on "Welded Built-Up and Rolled Heat-Treated T-I Steel Columns"being c o n d ~ c t e d at F r i t ~ Engineering Laboratory, Department of Civi lEngineering, Lehigh University in Bethlehem, Pennsylvania.

The project ls sponsored by th e United States Steel 'Corporation.Charles G. Schill ing of tha t corporation made many valuable Gomments,both in the course of the program, and in the preparation of this report. Task Group 1 of the Column Research Council of' the EngineeringFoundation acted in an advisory capacity under the chairmanship 6fJohn A. Gil l igan. T.he assistance of Ching-KuQ Yu during th e study isacknowledged.

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7. DEFINITION OF TERMS

Residual StressesResidual stresses are the s tr e's se s formed' as a resul t of

permanent deformations of certa in fibers during the fp.b.rication orcooling processes.Yield Point

The yield point is the f i r s t stress in a mate ri al l es s thanthe maximum attainable s t ress , a t which an increase in s tra in occurswithout an increase i n s tr es s( 8) .Yield Strength

The yield strength is the stress a t which a material exhibitsa specif ied limit ing deviat ion from the proportionality of stress tos t ra in . The deviat ion is expressed in terms of s tra in(8).Yield Stress Level

The yield st ress level is th e average s tress during actualyielding in the plast ic range. I t remains fair ly constant for s tructura ls teel , provided the s t ra in ra te remains constant.Static Yield Stress Level

The s t a t i ~ yield st ress level is the average s tress duringactual y ie ld in g in the plast ic r a n g ~ , with zero s t ra in rate .Stub Column

A stub column is a short compression t es t specimen, suf f i c i en t ly long for use in measuring the s t ress-s t ra in relationship for the

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complete cross section, but short enough to avoid buckling as a columnin the elas t ic and plast ic ranges.


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8 TABLES AND FIGURES

-14.,.


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NO.

TABLE 1

SHAPE

SHAPES TESTED

EDGEPREPARATION

PLATE SIZE (IN)

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{ 6 x 1/2 flangeW-A 6 x 7 - H Sheared

6 x 3/8 web

r 6 x 1/2 flangE?W-B 6 x 7 - H Flame-Cut l 6 x 3/8 web9 x'3/4 flange

W.C 9 x - H Flame-Cut { 9 x 1/2 web6 x 1/4

W-D 6 x 6 Box Flame-Cut { x 1/410 x 1/2

W-E 10 x 10 Box Flame-Cut ( 9 x 1/2


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TABLE 2 TENSION COUPONS TESTED

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SHAPE COUPON NO. PLACE TAKEN

W-A-l Flange6 x 7 H W-A-2 Flange(Sheared)

W-A-3 Web

W-B-l Flange6 x 7 H W-B-2 Flange(Flame Cut)

W-B-3 Web

W-C-l Flange9 x H W-C-2 Web

W - C ~ 3 FlangeW-D-l *W-D-26 'x 6 BoxW-D-3W-D-4

W-E-l '1

Documents

Residual Stresses in Welded Built-up T-1 Shapes October 1965 R