strength of aluminium .pdf

8/9/2019 Strength of aluminium .PDF

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t r e n g th o f a l u m i n i u mm e m b e r s c o n t a i n i n g l o c a lt r a n s v e r s e w e l d sY F W L a i

Mitchell FacFarlane Hon g Kong

D A NethercotDepartment o f Civil Engineering University of Nottingham Nottingham UK

Received April 1 990; Revised Janua ry 1991)

High strength aluminium alloys when welded suffer a local loss ofstrength du e to the deve lopm ent of heat-affected zones (HAZ). The in-fluence of such localized strength losses on the structural behaviour ofa lumin ium mem bers i s s tud ied u s ing a numer ica l techn ique . A t ten t ion

is g iven to the r ep resen ta t ion o f the non l inear s t r es s - s t r a inbeha viour of a luminium , in par t icu lar, i ts representat ion in a formsuitab le for incorporat ion in to numer ical p rocesses . Two f in i te e le-men t p rog rams , p rev ious ly deve loped fo r u se w i th s tee l fr ame s t ruc -tures , have been modif ied to incorporate the special features of thealum inium problem. Resul ts are presented for a se lect ion of exam plesto i l lu s t r a te the sever i ty o f the HAZ ef f ec t on the load ca r ry ingcapacity of structural memOers. The theoretical predictions have beenver i fied by compar i son w i th bend ing tes ts on 5 nonwe lded and 22welded 70 19 a lumin ium beams . General ly good ag reemen t wasfound be tween the theo re t ica l p r ed ic t ions and exper imen ta l r esu l t sfor a l l the tes ts .

Ke yw ord s: aluminium alloys, heat-affected zones, buck ling we lds

Most aluminium alloys used for structural applicationsare heat-treated or work hardened e.g. 6000 series and7000 series, to improve their mechanical properties.However, when these alloys are welded, heat-affectedzones (HAZ) are fo rmed in the parent metal adjacent tothe welds. These heat-affected zones possess inferiormaterial properties, the presence of which can lead to asignificant loss of strength for the member as a whole.The reduction in 0.2 proof stress, 00.2, in thisannealed region has been .found to be approximately25 -5 0 of the original strength of the parent metal.

This effect is not, of course, confined to membersbuilt-up by welding; welding an attachment to anextruded section or using welding at the ends of amember to attach it to other parts of the structure willalso produce localized HAZ effects. Although studies ofaluminium columns containing longitudinal welds havebeen reported *, almost no work appears to have beenconducted to study the effect of transverse welds onmember strength. Sample results were given by Valtinatand Muller 2 but no general conclusions were presented.

The aims of this paper are to present the essentialfeatures of two schemes for the numerical assessment ofthe ultimate strength of aluminium columns, beams and

beam-columns, including the effects of HAZ material,to validate the resulting programs by comparisonsagainst both existing data and a series of specially con-

0141-0296/92/040241-141 9 9 2 B u t t e r w o r t h - H e i n e m a n n l a d

ducted tests and to illustrate the use of these programsby providing results for a selection of examples whichdemonstrate the effects of local transverse welds. Thetwo programs, INSTAF and BIAXIAL, cover in-planebehaviour and flexural-torsionalbending, respectively.

Notation

AA*EE*E,LL*~ x

M o ~?1

?1

P

P

buckling/biaxial

area of cross-sectionarea of heat-affected zoneYoung's modulus of parent metalYoung's modulus of heat-affected materialtangent moduluslength of memberlength of heat-affected zonenondimensionalized maximum bendingstrength of member about x axis (=Mx/M0.2x)---- Z~o0.2knee facto r of parent metal in Ram berg-Osgood formulaknee fac tor of heat-affected material inRam berg-Osgood formulaaxial forcenondimensional maximum compressivestrength of member Pult/~o.2A )ultimate compressive strength for nonweldedmember

Eng. Struct. 1992, Vol. 14, No 4 241


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S t r e n g t h o f a l u m i n i u m m e m b e r s c o n t a i n i n g l o c a l t r a n s v e r s e w e l l s : Y F L a i a n d D A N e t h e r c o t

Pu~l

O

Q u i t

Q*t

Qo.z~

r~, ~

o~

00 2

0o .2

Oult~ t

e 1

, ~ky~ y

u l t ima te compress ive s t r eng th fo r we ldedm e m b e rla tera l point loadu l ti ma t e s tr e n g th o f n o n we l d e d me m b e r u n d e rla tera l point loadu l t i ma t e s t r e n g t h o f we l d e d me mb e r u n d e rla tera l point loadla te ra l po in t load co r re spo nd ing to ach ieve men tof M0.z~ with in cross-se ct ionrad ius o f gy ra t ion abou t x and y axes . r e spec -t ive lyp la s ti c m odu lus o f a sec t ion abou t x ax i se las t ic l imi t s t ress of parent meta le las t ic l imi t s t ress of heat-affec ted mater ia l0 .2 p ro of s t r es s o f pa rea t me ta l0 .2 p ro of s t re s s o f hea t -a ffec ted ma te r i a lu l t ima te tens i l e s t r eng th o f pa ren t me ta lu l t ima te t ens i l e s t r eng th o f hea t -a ffec tedmate r i a ls t r a in a t rup tu re o f pa ren t me ta ls t r a in a t rup tu re o f hea t -a ffec ted ma te r i a lnond imens iona l i zed mod i f i ed s l ende rness o fbea m = Mo.2x /Mcr) u2s lende rness( L / rx, L/r>,)nond in tens ionahze d s l ende rness r a t io( h f l r ( E l o o . 2 ) . 2 ,hy/r E/oo,2)1/2)

S t r e s s -s t r a in c u r v e s o f a l u m i n i u m a l lo y s

The ana lys i s o f the ine la s t i c behav iour o f a lumin iums t ruc tu res r equ i re s tha t a su i tab le r ep resen ta t ion fo r then o n l i n e a r s t r e s s - s t r a i n c u r v e b e u s e d , s i n c e t h echa rac te r i s t i c ob ta ined f rom a t ens i l e spec imen canno tbe s impl i fi ed to one o f e l a s t ic /pe r fec t ly p la s ti c beha v iouras i s f r equen t ly the case fo r mi ld s t ee l . The ac tua ls t r e s s - s t r a in cu rve typ ica l ly does no t possess a de f in i tey ie ld po in t , bu t r a the r a rounded zone o r ' kn ee ' o r va ry -ing sha rpness depend ing on the a l loy des igna t ion . InBr i t a in , and indeed in mos t o the r coun t r i e s , i t i s com-mo n p rac ti ce to r ega rd the 0 .2 p ro of s t r e ss , 00.2 , a sfu l f il l ing the ro le o f ' y i e ld po in t ' o f a lumin ium.

From a s tudy o f va r ious poss ib le schemes t '3 -7 , themo d e l p r o p o s e d b y Ra mb e rg a n d O s g o o d L5-7 h a s b e e nse lec ted a s the m os t su i tab le because i t i s ab le to p rov idea c lose r ep resen ta t ion o f the ac tua l behav iour o f mos ta l l o y s . By u s i n g t h e mi n i mu m v a l u e o f Yo u n g ' smo d u l u s , t h e Ra mb e rg - Os g o o d c u r v e g i v e s a l o we rbound to the expe r ime n ta l cu rves . M oreov er, thep a r a me t e r s r e q u i r e d b y t h e f o r mu l a a r e c o m mo n l y l is te dfo r s t anda rd a l loys in han dbooks and spec i fi ca t ions .

Th e Ra mb e rg - Os g o o d f o r mu l a i s u s u a l l y e x p r e s s e da s

+ O .O02(-~-a ~"e E \o0.2 /

(1)

and the t angen t modu lus E, , i s g iven by

do 1E, - - (2)

de 1 + ( (O.O0___2n)~( o ~ - '

E \ 0 0.2 / / \ 0 r 0 . 2 / /

Oul . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

' z Inelost ic reg ton (- 50 Neces)4

o I

"E ~ t i cr ' ig i~(I pte~)

i gu r e I P i e c e w i s e f o r m o f R e m b e r t - O s g o o d c u r v e

The f i r s t t e rm on the r igh t -hand s ide o f equa t ion (1 )rep resen t s the e la s t i c componen t o f s t r a in , wh i l s t thesecond t e rm r epresen ts the p l as ti c c o u n t o f s tr a inI f bo th equa tions a r e examined two undes i r ab le f ea tu resa re appa ren t

the Ram berg -O sgood cu rv e s t a rt s to dev ia te f romthe l inear e las t ic line a =E . e a ssoon as i t leaves theo r ig in

e and E, a re func t ions o f o , i e , e= f ( a ) a n dE, = f ( o )

Clea r ly the second t e rm o n the r igh t hand s ide o f equa -t ion (1) wi l l be ins ignif icant a t low s t ress levels , thecurve e ffec t ive ly fo l lowing the l inea r e l a s ti c l ine(o = E . e ) . Co mp ute r p rog rams tha t u se an u l t ima tes t r eng th approach to s imula te buck l ing behav iourusua l ly r equ i re o a s a func t ion o f e ( i . e . o = f ( e ) ) .Mo reoev e r, s ince the s t anda rd comput ing t echn ique wi l lbe one o f ' t r i a l and e r ro r ' , t he r e su lt ing non l inea r p ro -blem wil l require i te ra t ion techniques , e .g . d i rec t i te ra-t io n , N e w t o n - Ra p h s o n me t h o d e t c . , to e n s u re th erequ i red conv ergen ce . T hus i t i s computa t iona l lym u c h m o r e c o n v e n ie n t t o m o d i f y t h e R a n d ~ r g - O s g o o dfo rmula in to a p iecewise fo rm ( seeF i g u r e I ) .Fo r t h einelas t ic and s t ra in-hardening regions , d iv id ing thecurve in to approx ima te ly 50 p ieces and 30 p ieces ,respect ively is suff ic ient for the d i fference in s t ressbe twe en the o r ig ina l and p iecewise fo rm to be l e ss than0 . 1 . T h e t a n g e n t mo d u l u sEt , wh i c h ma y b e d e t e r -mined f rom equa t ion (2 ) , ca n a l so be r ep resen ted in th ismanner. By adop t ing th i s approach the au thors havefound tha t compu te r t ime i s u sua l ly r educe d by be tween10 and 30 t imes a s com pared wi th d i r ec t u se o f equa t ion( ] ) .

E l a s t i c l i m i t s t r e s s o f a l u m i n i u _ m a l l o y s

As m e n t io n e d a b o v e , t h e a - e c u r v e o f a lu mi n i u m a l lo y sexhibi ts ne i ther a def in i te y ie ld s t ress , nor a def in i tee las t ic limi t s t ress . I t i s there fore sugge sted that the for-

mu l a e o f Ma z z o l a ni 6 a n d Ra m b e r g - O s g o o d ~'7 b ecombined to ob ta in the express ion fo r the e la s t i c l imi tstress oe as

ae = 1 - [1 - 2-= /" ] m (3)00.2

242 Eng . S t ruc t . 1992 , Vo l. 14 , N o 4


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S t r e n g t h o f a l u m i n i u m m e m b e r s c o n t a i n i n g l o c a l t r an s v e r s e w e l ls : Y F L a i a n d D A N e t h e r c o t

1.0

0 .9

0 .8

0 .7

N 0 .6

~ 0.5

0 .4

0 3

0 .2

0.1

0I I I I | I I t I I5 tO 15 20 25 30 3 5 4 0 45 50

Knee ector, t

Figure R e l a t i o n s h i p b e t w e e n n a n d o e / o o . 2

where

m --- 2.3 0 - 1.751 2T ]n = k n e e f a c to r in R a m b e r g - O s g o o df o r m u l a

The re la t ionsh ip be tween0.elao.2 and n i s shown inFigure 2 . I f the knee fac to r, n , o f t h eRa m b e rg - O s g o o d f o r mu l a is u s e d to c l a ss i fy th e a l lo y,equa t ion (3 ) m ay be s impl i fi ed to

fo r

5 _< n < 10 0.e= 0 . 4 5 0 0 .2

10 _< n < 20 (no nh eat trea ted allo ys) 0.~= 0 . 6 8 0 . 0 . 2

20 _< n < 40 (he at-tre ated alloy s) o. = 0.81Oo.2

S t r e s s s t r a i n r e l a t i o n s h ip s o f h e a t a f f e c t e dmate r ia l

Th e s t r e s s - s t r a i n r e la t io n s h ip o f h e a t - a ff e c t e d ma t e r ia l( H A Z ) c a n a l s o b e e x p r e s s e d b y a R a m b e r g - O s g o o dfo rmula ( seeFigu r e 3 , s ince the typica l character is t ic

5 0 0

2 5 0

A 2 0 O qE

Z=. 150

O 3

100

5C

Porent moteriol

E = 7 0 0 0 0 ( N / m m 2 )

o '(~2= 25 0 (N/ra m 2 }n = 2 5

fHAZ moter ia l

= 7 0 ( X X ) ( N / m m 2 )a ~ . 2 = 1 2 5 ( N / r a m 2 )

n = 10

I J I [ I I I I I I I0 I 2 3 4 5 6 7 8 9 IO II

St ro in (%)

Figure 3 T y p i c a l s t r e e s - s t r a i n c urve s f o r p a r e n t a n d H A Z m a t e r i a l

s h o ws Yo u n g ' s mo d u l u s o f t h e h e a t - a f fe c t e d ma t e r ia l a sbe ing the sam e as tha t o f the pa ren t a l loy bu t the ' y i e lds t r e s s ' , 0 .~.2' be ing reduc ed to be twe en 50% and 75% ofthe o r ig ina l va lue 9 . Ca re i s, how ever, necessa ryb e c a u s e e x a m i n a t i o n o f t h e a v a i l a b le0 . - e d a t a f o r I f f A Zm a t e r i a l m a y w e l l s u g g es t t he u s e o f a l o w e r n - v a l uet h a n f o r t h e p a r e n t m a t e r i a l . S i n c e t h i s w i l l g i v e as t e e p e r c u r v e a t l a r g e st r a in s n d t h u s e v e n t u a l l y h i g h e rH A Z s t r es se s i t i s n e c e ss a r y t o i m p o s e s o m e f o r m o fs t r a in l i m i t i n t h e a n a l y s i s . I t i s w o r t h m e n t i o n i n g t h a t am o r e s o ph i s t i c a t ed e p r es e n ta t i on o f H A Z e f fe c ts w o u l db c q u i t e p o s s i b l e w i t hi n t h e p r e s e n t a n a l y s i s e . g . o n e t h a tr e c o g n i s e d t h e H A Z a s h a v i n g v a r i a b l e p r o pe r t i e sa n d / o r a m o r e c o m p l e x s h a p e ; a n i m p r o v e m e n t o f t hi st y p e f i rs t r e q u i r e s t h a t b e t t e r q u a l i t y m e a s u r e m e n t s o fH A Z p r o p e r t i e s b e av a i l a bl e .

D e s c r ip t io n o f th e I N S TA F p r o g r a m

In o rde r to s imula te the in -p lane behav iour o f va r iousa lumin ium sec t ions , the INSTAF p rogram (o r ig ina l lyp repa red a t the U n ive r s i ty o f A lbe r ta ) to , wh ich i s basedon an u l t ima te s t r eng th ' p l a s t i c zones ' app roach , wasmodi f i ed to hand le the spec ia l p rob lems o f a lumin iums t ruc tu res . Or ig ina l ly INSTAF was re s t r i c t ed to theana lys i s o f b raced and u nbraced m ul t i s to rey s t ee l fr amesc o mp o s e d o f I - s e c t i o n me mb e r s b e n d i n g a b o u t t h e i rma jo r axes . The an a lys i s is based on a s t i f fness fo rmula -t ion wh ich accoun t s fo r geomet r i c a s we l l a s ma te r i a lnon l inea r i ty, the in f luence o f r e s idua l s t r e s ses an d s t ra inha rden ing o f the ma te r ia l . Th e fo rm ula t ion pe rmi t s con-s ide ra tion o f ex tende d reg ions o f y ie lded ma te r i a l r a the rthan d i sc re te p la s ti c h inges in beams and b eam -co lumn s ,re su l ting in fin i te e l emen t equa t ions , wi th the N ew to n-Raphson m e thod be ing used to so lve fo r the ove ra l l load -de fo rm a t ion cha rac te r i s ti c s o f the s t ruc tu re .

Since the s t r e s s - s t r a in r e la t ionsh ip o f the o r ig ina lp r o g r a m wa s t r il in e a r, t h e s t r e s s - s t r a i n c u r v e h a d t o b em o d i fi e d in to t h e p i ec e w i se f o r m o f R a m b e r g - O s g o o dfo rmula desc r ibed p rev ious ly. Moreover, the o r ig ina lp rogram cou ld dea l on ly wi th I - sec t ions unde r ma jo rax i s bend ing . Af te r the mod i f i ca t ions INSTAF canana lyse a lumin ium f rames o r i so la ted members wi thseve ra l d i f f e ren t types o f c ross - sec t ion ( I - sec t ion , H-sect ion, box-sect ion , tee-sect ion , channel and l ippedchanne l ) unde r ma jo r and minor ax i s bend ing . Themo d i f i e d I NSTAF c a n a l s o s i mu l a te t h e e f f e c t o flong i tud ina l and t r ansve r se we lds wi th in the member.

M emb ers con ta in ing t r ansve r se we lds a re ana lysed byd iv id ing the member in to seve ra l e l emen ts a long the i rl eng th , u s ing e lemen ts hav ing reduced p rope r t i e s torep resen t the hea t a f fec ted zones ad jacen t to thet ransve r se we lds . Because o f the way in wh ich eachcross-sect ion is represented , i t i s a lso poss ib le to dealwi th HAZ tha t ex tends ove r on ly pa r t o f the sec t iond e p t h a n d / o r a p a r t o f t h e me m b e r l e n gt h a s s h o wn i nFigure 4 .

The re su l t s ob ta ined f rom the mod i f i ed ve r s ion o fI NST AF h a v e b e e n c o m p a r e d w i t h e x p e r i me n t a l re s u lt sob ta ined f rom the Un ive r s i ty o f L iege ' 12 andtheore t i ca l r e su lt s ob ta ined by Hon g ~. Some e xampleso f t h e s e c o mp a r i s o n s a r e g i v e n i nFigures 5 and 6 ; thema x i mu m d i f f e re n c e b e twe e n e i t h e r t h e m e a n o f t h e t e str e su l t s and the INSTAF p red ic t ions o r the twotheore t i ca l ly ob ta ined co lum n cu rv es i s 5 %.

E n g . S t ru c t. 1 9 9 2 , Vo l. 1 4 , N o 4 2 4 3


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S t r e n g t h o f a l u m i n i u m m e m b e r s c o n t a i n i n g l o c a l t r a n s v e r s e w e l l s : Y F L a i a n d D A N e t h e r c o t

i

one p l a t e (minimum5 pieces)

JjMoterial (~h ~

/Material @

F / / o /A 1

Figure Discrotization and different location of welds withinc r oss - sec t ion

T ~ _ | o m m \

~ - U ~ . . ~ , , , , .

t pI

0.2

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1l I I I

o 0 . 4 o . o o . 8 l . o , .' z , 4 1 .6, . ~

Figure Com parison of INSTAF program with experimentalresults o btained by Un iversity of Liege 11'12

I.Il.O0.90.80.7

i~ 0.6

0.50.40.2

0 2i0.1

00

p-ZOOmm-~_ . , T ~T, s . , ~

01.2 1 =. 4 o '. 6 o t ~ , .'o , .'~ , . , , ~ , I ~ ~ ' .o L ~2t~,x

Figure 6 Comparison o f INSTAF and Hong 1 results (longitudin-ally welded columns)

D e s c r i p t i o n o f B I A X I A L p r o g r a m

T h e B I A X I A L p r o g r a m w a s o r i g i n a l l y d e v e l o p e d f o rs tee l m em bers 13 and wa s then mo dif ied to s imula te theth ree -d imens iona l beh av iou r o f a lumin ium m emb ershav ing a lm os t any open c ross - sec t ion compos ed o f aser ies of f ia t p la tes . BIAXIAL is a f in i te e lement pro-

g ram, in wh ich the d i sp lacemen t me thod i s u sed toarr ive a t the force d isp lace me nt re la t ionships fo r abeam-co lumn e lemen t by cons ide r ing the p r inc ip le o fv i r tua l work . I t c an fo l low the lo s s o f s t i f fness due tosp read o f y ie ld wi th in the c ro ss - sec t ion and hence t r acethe th ree -d imens iona l load -de f lec t ion re sponse up to co l -lapse . T he effec t of twis t ing and w arping o n s t i ffness istaken in to account , and res idual s t resses and in i t ia l ou t-of-s t ra ightness are a lso inc luded in the analys is . AN e w t o n - R a p h s o n s o l u t i o n m e t h o d i s u s e d . T h es t re s s - s t r a in re la t ionsh ip emp loyed i s aga in thep iecewise fo rm o f the Ramberg -Osgo od fo rmu la . Bo thlongi tudinal and local t ransverse welds with in the

m e m b e r m a y b e a l l o w e d f o r u s i n g t h e s a m e t y p e o fapp roach a s desc r ibed fo r INSTAF.

xperimental v e r i f i c a t i o nVery l i t t le exper imenta l da ta on the s t ruc tura l responseo f a lumin ium me mb ers con tain ing loca l t r ansve rsewe lds a re ava i lab le . In o rde r to check the bas i s o f thea n a ly t ic a l a p p r o a ch u t il iz e d b y I N S T A F a n d B I A X I A La se r ie s o f te s t s on we lded b eams h as been condu c ted .Al l the beams used were 7019 a lumin ium a l loy wi th ac ross - sec t ion o f a 50 .9 mm x 102 .2 mm rec tangu la rbox . Due to the h igh to r s iona l s t i f fness o f the box -sec t ion , the beams were expec ted to f a i l by s imp lebend ing ra the r than by la te ra l buck l ing . In o rde r torep re sen t the mos t comm only occu r ing w e ld ing s i tua t ionand to p roduce d i f fe ren t ex ten t s o f hea t -a ffec ted zone s ,two 7 019 a lum in ium p la te s o f va ry ing leng ths wi thth ickness 12 .4 mm and app rox im a te w id th 24 .5 mmwere f i ll e t we lded to the top and bo t tom f langes o f theb o x s e c t i o n . T h e c r o s s -s e c t i on a l p r o p e r t i e s a n d t h ea v e ra g e d i m e n s i o n s f o r t h e n o n w e l d e d a n d w e l d e d s e c -

t i o ns a r e s h o w n i n F i g u r e 7A l to g e t h e r 5 n o n w e l d c d a n d 2 2 w e l d e d b e a m s w c r c

t es te d. T h e b e a m s w i t h e i th e r 1 2 0 0 m m o r 2 2 0 0 m m i nl e n g t h a n d w e r e s i m p l y s u p p o r t e d o v e r a s p a n o fI 0 0 0 m m o r 2 0 0 0 m m r es p e c ti v e ly . T h e w e l d e d p l a t e s

w e r e e i t h e r l o c a t e d a t m i d - s p a n s y m m e t r i c a l l y a tq u a r t e r - s pa n o r n e a r b o t h e n d s o f t h e s pa n . P l a t e s w e r ea l s o w e l d e d f o r t h e w h o l c l e n g t h o f t he f l a n g e s t o re p r e -s e n t the fu l ly hea t -a ffec ted beam. The de ta i l s fo r thebeam des igna t ions , loca t ions and leng th o f the we ldedpla tes are l is ted inTable 1 All the we ld ing was don e bya qua l i fi ed w e lde r a t the Roy a l Armam en t R esea rch a riaD e v e l o p m e n t E s t a bl i sh m e n t R A R D E ) . T h e w e l d i n gwire was 1 .6 mm d iame te r to theo l d Brit ish S t a n d a r dReg is t ra t ion des igna t ion NG61 , wh ich co r re sponds tothe Alumin ium Assoc ia t ion in te rna t iona l des igna t ion5 5 5 6 A .

a t e r i a l p r o p e r t i e s a n d e x t e n t o f h e a t a f f e c t e dz o n e

Befo re pe r fo rming the beam te s t s ,tens i le oupon tes tswere conduc ted in o rde r to ob ta in the mechan ica l p ro -pa r t ie s o f bo th pa ren t and hea t -a ffec ted ma te r ia l . A l l the

2 4 4 E n g . S t r u c t . 1 9 9 2 , Vo l . 1 4 , N o 4


5/14

S t r e n g t h o f a / u m i n i u m m e m b e r s c o n t a i n i n g l o c a l t ra n s v e r s e w e l ls : Y F L a i a n d D A N e t h e r c o t

R= 2.3rnm

4.7 mm- - - m

a

~5.4mrn

R = 3 .2m~

lO2.2 turn

C r o s s - s e c t i o n a lproperties

A = 1415.1 mmZ 1/

2" 1.7996 x l0 s mm4~t~/

rx 35 .7 mm J

50. 9 mm ~1

I 24.5mm_1I - - i

12.4 rnrn. _ L

~" Filletw e l d sApproximate cross-sectionalp r o p e r t i e s

A = 2548.1 mmZ /

Z 4.8 03 8 x 106 ram4 t ~

rx 45.2 mm J

F i g u r e C r o s s - s e c t i o n a l d i m e n s i o n s o f t e s t s p e c i m e n s

H a r d n e s s s u r v e y s w e r e c a r r i e d o u t o n a l l t h e b e a mspec imens to de te rmine the ex ten t o f the hea t -a ffec tedzones . Fro m these , i t was foun d tha t the l eng th o f thehea t -a ffec ted zone was equa l to the l eng th o f we ldedp la te p lu s 7 .5 mm on bo th s ides . Mo reoev e r, i t was a l sofound tha t bo th f l anges and on ly pa r ts o f the webs w erea ffec ted by we ld ing . The ex ten t o f hea t -a ffec ted zonepene t ra t ion wi th in the web ex tended to abou t 22 .3 mmmeasu red f rom the mid - th ickness o f the f l ange , g iv ing ato tal area o f the hea t -a ffec ted zone o f abou t 65 o f thea rea o f the o r ig ina l c ro ss - sec t ion .

esting procedure and instrumentation

The com ple te se t -up o f the beam te s t i s shown inFigure8 and fu l l de ta i l s can be found in Re fe rence 14 . Eachbeam was s imp ly suppor ted a t i t s ends and loaded bytwo ve r t i ca l po in t loads . D ur ing te s t ing , the to tal load onthe beam and the de f lec t ions a t mid -span (Ac) and thequa r te r- span were reco rded au toma t ica l ly and a l l there su l ts w ere s to red on the ha rd d i sk o f the comp u te r a f te rcomple t ion . Fo r sa fe ty rea sons , load ing was no t con -t inued r igh t up to f a i lu re , the t e s t s be ing s topped whenthe ra id - span exh ib i ted a r ea sonab ly l a rge amoun t o fdef lec t ion .

B e a m t e s t r e s u l t sand computer s i m u l a t i o nu s i n g I N S TA F

Al l the expe r imen ta l r e su l t s were compared wi th thetheo re tica l p red ic t ions ob ta ined by INS TA F, a comple tes e t o f l o a d - d e f l e c t i o n c o m p a r i s o n s i s a v a il a b le i nRefe rence 14 . Typ ica l exam ples a re p rov ided a sFigures9 and 10 in the fo rm o f nond imens iona l ized p lo t s o fQ/Qo.z ve rsus At / span x 100 fo r mid -span de f lec -t ions where

c o u p o n r e s u l t s c a n b e f i r e d w i t h R a m s b e r g - O s g o o dfo rmu lae ( see Re fe rence 14 ) and the re su l t s fo r thepa ren t and hea t -a ffec ted ma te r ia l p rope r t i e s a re sum-marized in Tables 2 and 3 , respect ive ly. All the heat-a ffec ted coupons showed a reduc t ion in s t r eng th , w i ththe mean ra t io s o fa~l/ao.l~ 0 ~ . 2 / O ' 0 . 2and a~t/a lt be ing0 .62 , 0 .65 and 0 .83 , r e spec t ive ly.

o r

M 0 2 xQ0z , - (kN) fo r beam s wi th spans o f

0 . 3 1 0 0 0 m m

M o . 2 xQ0.2~ - (kN) for beam s with spans of

0 . 8 2 0 0 0 m m

Roller support/I

2Q

~ 1 ~0 ton load cell

II II III I t ~ LO odspreOder

B e a m

5 0 m m 5 0~ 4 0 0 m m = =

S p a n = I O 0 0 m m o r 2 0 0 0 r a m

I snl 1--

I

F i g u r e 8 B e a m t e s t s e t - u p

Eng. Struct . 1992, Vol. 14, No 4 2 4 5


6/14

S t r e n g t h o f a l u m i n i u m m e m b e r s c o n t a i n i n g l o c a l t ra n s v e r s e w e l l s : Y. F. L a i a n d D . A . N e t h e r c o t

Table I Te s t s c he me a nd s pe c ime n de s igna t ion N , nonwe lde d be a m; W, we lde d be a m; P, pa re n t me ta l ; E , we lde d p la t e s loc a te d ne a rthe two e nds ; F, fu l ly -we lde d

Loc a t ion o f we lde d p la t e sSpe c ime n de s igna t ion

Le ng th o f w e lde d p la t eLwp

LTL= 1 2 0 0 m m LTL= 2 2 0 0 m m LTL= 1 2 0 0 m m LTL= 2 2 0 0 m m

i~ L 7"L ~-i N 1000-P - 1 N -2000-P - 1N-IOOO-P-2 N-2000-P-2

f I N - lO O O -P - 3( w i t h o u t w e l d s )

L~ . . I " - W- 1 0 0 0 -L / 2 - 1 W- 2 0 0 0 - I J 2 - 1

wp

I 1 W-1000-L12-2 W-2 000-L /2 -2- - W- 1 0 0 0 - L / 2 - 3 W- 2 0 O O -L / 2 -3

W- 1 0 0 0 - L / 2 - 4 W- 2 0 0 0 - L / 2 - 4(a t mid-span)

6 0 0 m m 6 0 0 m m

~ - W-2000-L /4 -1

I I W-2OOO-L/4-3i....i- - ~ ~ , - - L w p ~ F. - - L w p

(symmetrica l ly a t quarter-span)

1 5 0 r a m 1 5 0 r a m

r- I-1i

- ' t I ' -L w p L w p - - -II - - -(ne a r the tw o e nds )

W-10OO-E-1W-IOOO-E-2W- 1 0 0 0 - E - 3

W-IOOO-F-1W-IOOO-F-2

I ] wW- 1000-F-4W- 1000-F-5

(a long the w ho le s pe c ime n)

W-2OOO-F-1W-2OOO-F-2W- 2 0 0 0 - F - 3

5 0

2 5

1 2 0 0

2 0 0

2 0 0

2 2 0 0

Spe c ime n de s igna t ion c onve n t ion i s a s s hown be low:

~ W-lOOO-L/2-1 ~ _

C ond i t ion o f Spa n o f be a m Loc a t ion o f Se que nc e numbe rwe ld ing du r ing t e s t we lde d p la t e fo r s pe c ime n

Table 2 Parent meta l propert ies , n = In211n oo.21oo.1 . Al l t e ns i l e c oupons w e re ob ta ine d f rom be a m N-IOOO-P-1

E O0. 1 GO. 2 (]rult (Et

Specim en Loca t ion (N/ram2) (N/ram2) (N/ram2) (N/ram2) (%) n ~=t/00.2

N - 1 F l a ng e 6 8 5 0 0 3 6 3 3 7 0 4 3 2 1 0 . 4N - 2 F l a ng e 6 9 8 0 0 3 7 6 3 8 5 4 3 1 11 . 6N - 3 F l a ng e 6 8 3 0 0 3 5 8 3 6 6 4 2 0 1 0 , 4N -4 We b 7 2 0 0 0 3 7 3 3 6 0 4 3 6 1 0 .2N - 5 We b 7 2 9 0 0 3 7 0 3 7 8 4 3 9 9 . 0N - 6 We b 7 0 2 0 0 3 6 6 3 7 4 4 3 4 9 .1N - 7 We b 7 4 6 0 0 3 5 2 3 5 9 4 1 5 1 0 . 6

M a x i m u m 7 4 6 0 0 3 7 6 3 8 5 4 3 9 11 .6M i n i m u m 6 8 3 0 0 3 5 2 3 5 9 4 1 5 9 .1M e a n 7 0 9 0 0 3 6 5 . 4 3 7 3 . 1 4 2 9 . 6 1 0 .3

S t a n da r d 2 1 7 5 . 2 7 . 8 8 . 2 8 .1 0 . 7 3de v ia t ion

C oe ff i c i e n t 3 . 07 2 . 15 2 . 20 1 . 89 7 . 11of varia t ion(%)

3 6 . 3 1 . 1 6 82 9 . 3 1 . 1 1 93 1 . 4 1 . 1 7 33 7 . 3 1 . 1 4 732 . 4 1 . 1613 2 . 1 1 , 1 6 53 5 . 1 1 . 1 5 6

3 7 . 3 1 . 1 7 32 9 . 3 1 . 1 1 93 3 . 4 1 . 1 5 5

2 4 6 E n g . S t r u c t . 1 9 9 2 , Vo l . 1 4 , N o 4


7/14

Strength o f a luminium mem bers conta in ing loca l t ransverse wel l s Y F Lai and D A Netherco t

Table 3 Hea t -affec ted prope r t i es , n = In 2/ Io(o~.21~.~ ) . ( see Reference 6) . Al l t ens i l e coupo ns wer e obta ined f rom top f l ang e of beamW-10OO-P-1

E * ~xil.1 o~ .z oust E~Spe c i m e n ( Nt r nm = l iN /r am 2 ) (NJRr~IR 2 ) (NJ nlll~ 2 ) (% ) 17 oru~t/ord.2

W - I 7 2 9 0 0 2 2 4 2 3 7 3 8 8 1 3 . 8

W - 2 7 2 7 0 0 2 3 2 2 4 8 3 5 5 1 2 . 8W - 3 7 0 7 0 0 2 3 2 2 4 5 3 5 3 1 2 .4W- 4 6 9 0 0 0 2 2 1 2 3 5 3 3 1 1 0 . 5W- 5 7 3 6 O O 2 2 9 2 4 3 3 6 2 11 . 7

M a x i m u m 7 3 6 0 0 2 3 1 2 4 8 3 8 8 1 3 . 8M i n i m u m 6 9 0 0 0 2 2 1 2 3 5 3 3 1 1 0 . 5M e a n 7 1 7 8 0 2 2 7 . 6 2 4 1 . 6 3 5 7 . 8 1 2 . 2

S t a n d a rd 1 6 9 1 . 6 4 . 4 4 . 9 1 8 . 3 1 . 1 0de v i a t i on

C o e f f ic i e n t 2 . 3 6 1 . 9 4 2 . 0 2 5 . 1 2 9 . 0 5o fva r i a t i o n(%)

1 2 . 3 1 . 6 3 7

10 .4 1 .43112.7 1 .44111 . 3 1 . 4 0 811 .7 1 .490

1 2 . 7 1 . 6 3 71 0 . 4 1 . 4 0 811.7 1 .481

1.4

1.2

I.C

~O.E\

0.6

0.4

0 . 2 . . . .

0 I | I I / I I0 ' 2 :3 4 5 6 7 8

6c SPan x 100%

Figure 9 Com pm i s o n be t we e n t e s t r e s u lt s a nd p r e d i c t e d l oa d -de f l e c t i o n c u r ve s a t m i d - s pa n ( s pe c i m e n W- I OOO-L/ Z

F igur e 7 the va lues o f Q 0 2 , are

- Q0.2. = 6 8.1 kN. g l o

1.4

1.2

1.0

~o.a60.6

0 4

0 2

a.. ,. ,N=~,,.~ = 2 5 . 5 k N W - I 0 0 0 - L / 2 - I I V- I O O O - L / 2 - 2

W I 0 0 0 - L / 2 - 3

w- ,ooo-L/z-4 =57.5 IoN. . . . . M i n i m u m~ M e a a

~ ~ * ~ = 2 1 . 6 k N

. ~ f aeem de~g~tion/ ~/ ~/ o W- 2 0 0 0 - L / A - I

. W - 2 0 0 0 - L / - 2

t W - 2 0 0 0 - L / A - 3

~ r . . . . . M inimumj ~ ~ M e o n

/ ~ . . . . M aximum

I 2 3 4 5 6 7Ac/spon x 100%

Figure 10 Com pa r i s on be t we e n t e s t r e s u l t a nd p r e d i c t e d c u r ve sa t m i d - s pe n ( s pe c i m e n W- 2000 - L / 4 - 1 , 2 , 3 )

The me an value of Oo.2 is use d to calculate Mo.2~ fornonwelded cross-sections. For the partially heat-affectedc ross - sec t ion , mean va lues o f bo th 00 .2 and 0~2 a rerequ i red . The re fo re , fo r the c ro ss - sec t ion shown in

s pec imen des igna t ion : W -1000-F - l , W- IO 00-F -2 , W-IO O O -F -3 ,W - 1000 -F-4 , W-10OO-F-5)

specimen des ignat ion: W-20OO-F - l , W- 2 0 0 0 - F - 2 , W- 2 0 0 0 - F - 3 )

o the r beam s pec imens w i thspan 1000 mm)

o the r beam s pec imens w i ths pan 2000 mm)

F r o m Tables 2 and 3 , i t is c lear tha t the mechanica l pro-pe r t i e s fo r the pa ren t and hea t -a ffec ted ma te ria l sh ow acer ta in var iab i l i ty. T o take th is e ffec t in to accou nt , th reetheo re t ica l cu rves a re shown inFigures 9 and 10 theseth ree cu rves be ing ob ta ined by inpu t t ing the max imum,mean and min im um va lues o f 00.2 and o~.2 , r e spec t ive lyin to the INST Al : p ro g ram. The e ffec t o f r e s iduals t r e s se s i s neg lec ted in the compu te r s imu la t ion .

~,, 76 rnm ~i

6 . 3 m m

76 m m

Figure 11

4 . 3 m m

Cross-sec t ion used for paramet r i c s tudies ( INSTAF)

Eng. S t ruc t . 199 2 , Vol. 14 , No 4 247


8/14

S t r e n g t h o f a l u m i n i u m m e m b e r s c o n t a in i n g lo c a l t r a n s v e r s e w e l l s : Y F L a i a n d D A N e t h e r c o t

Table 4 C o m p a r i s o n b e t w e e n t e s t r e s u l t s a n d t h e o r e t i c a l r e s u l t s o b t a i n e d u s i n g I N S TA F p r o g r a m

E x p e r i m e n t a l M e a n o f T h e o r e t i c a ll o a d e x p e r i m e n t a l l o a d

Sp e c i m e n ~ c ( m a x ) A o ( m a x ) O rn ax 0 3 0 O s o 0 3 0 A s o 0 3 o O e o D i f f e r e n c ed e s i g n a t i o n ( m m ) ( m m ) ( m m ) ( k N ) ( k N ) ( k N ) ( k N ) ( k N ) ( k N ) ( % ) R e m a r k

N - 1 0 O O -P - 2 5 1 . 7 3 6 . 6 6 8 . 2 6 2 , 7 - 6 2 . 3 - 5 8 . 2 - 6 . 6N - I O O 0 - P - 3 6 3 . 1 4 5 . 3 6 9 . 7 6 1 . 9 -

W- 1 0 0 0 - 4 / 2 - 1 3 1 . 7 2 2 . 2 5 8 . 8 5 7 . 2 - 5 6 . 0 - 5 2 . 5 - 6 . 2W - 1 0 0 0 - 4 / 2 - 2 6 2 . 3 6 2 . 7 5 4 . 8 5 4 . 8W - 1 0 0 0 - 4 / 2 - 3 4 8 . 1 3 4 . 4 6 4 . 2 6 0 . 3 -W- 1 0 0 0 - 4 / 2 - 4 6 0 . 1 4 5 . 1 5 7 . 2 5 1 . 7 -

W- 1 0 0 0 - E - 1 6 1 . 1 4 4 . 3 6 4 . 0 5 7 . 2 - 5 6 . 0 - 5 7 . 6 - - 2 . 9W- 1 0 0 0 - E - 2 6 5 . 9 4 6 . 6 6 4 . 4 5 5 . 2 -W- 1 0 0 0 - E - 3 6 4 . 4 4 5 . 2 6 4 . 4 5 5 . 6 -

W - I O O 0- F -1 > 5 1 . 9 > 3 8 . 1 > 1 0 2 . 6 8 8 . 5 - 8 8 . 7 - 8 0 . 3 - 9 . 5W - 1 0 0 0 - F - 3 > 5 9 . 0 > 4 1 . 0 > 1 0 4 . 2 8 7 . 7 -W - 1 0 0 0 - F - 4 5 6 . 7 > 3 8 . 5 > 9 8 . 7 8 9 . 3 -W - I O 0 0 -F - 5 > 5 4 . 0 > 3 8 . 5 > 9 7 . 9 8 9 . 3 -

N -2 O O O -P - 1 1 2 6 . 7 7 9 . 9 2 3 . 0 - 2 0 . 0 - 2 0 . 3 - 2 0 . 0 1 . 5N - 2 0 0 0 - P - 2 1 2 8 . 7 8 2 . 2 2 3 . 6 - 2 0 . 5

W- 2 0 0 0 - 4 / 2 - 1 2 0 8 . 5 1 3 5 . 7 2 0 . 7 - 1 7 . 0 - 1 9 . 1 - 1 8 . 6 2 . 6W- 2 0 0 0 - 4 / 2 - 2 1 5 5 . 2 1 0 3 . 8 2 3 . 6 - 1 9 . 6W - 2 0 0 0 - 4 / 2 - 3 1 0 5 . 3 6 9 . 8 2 3 . 7 - 2 1 . 2W - 2 0 0 0 - 4 / 2 - 4 > 1 0 5 . 0 > 6 7 . 8 > 2 0 . 9 - 1 8 . 2

W- 2 0 0 0 - 4 / 4 - 1 > 1 2 8 . 7 > 8 3 . 0 > 2 2 . 9 - 1 9 . 9 - 2 0 . 8 - 1 9 . 6 5 . 8W- 2 0 0 0 - 4 / 4 - 2 > 1 2 7 . 4 > 8 1 . 9 > 2 4 . 7 - 2 1 . 7W- 2 0 0 0 - 4 / 4 - 3 > 1 2 2 . 7 > 7 8 . 2 > 2 3 . 3 - 2 0 , 7

W - 2 0 0 0- F -1 > 1 5 3 . 4 > 9 8 . 5 > 3 9 . 3 - 3 1 , 6 - 3 1 . 6 - 2 8 . 5 9 , 8W - 2 0 0 0 - F - 2 > 1 4 4 . 6 > 9 5 . 6 > 3 8 . 6 - 3 1 . 5W - 2 0 0 0 - F - 3 > 1 4 6 . 8 > 9 5 . 9 > 3 9 . 6 - 3 1 , 8

L BL B

B FLBL BLB

L BL BL B

N BN BN BN B

LBLB

B FB FB FB F

N BN BN B

N BN BN B

0 3 0 c o r r e s p o n d i n g a p p l i ed l a te r a l p a t c h l o a d w h e n m i d - s p a n o f b e a m d e f l e c t s 3 0 m mQ s o c o r r e s p o n d i n g a p p l ie d la t e r al p a t c h l o a d w h e n m i d - s p a n o f b e a m d e f l e c t s 6 0 m mQ m a x m a x i m u m a p p l ie d l at e r a l p a t c h l o a d m e a s u r e d in t e s tA c ( m a x ) m a x i m u m m i d - s p a n d e f l e c t io n o f b e a m m e a s u r e d i n t e s tA o ( m a x ) m a x i m u m q u a r t e r - s p a n d e f l e c t i o n o f b e a m m e a s u r e d in t e s tL B b e a m f a i l e d i n l o c a l b u c k l i n gB F b e a m f r a c t u r e d d u r i n g t e s tN 8 n o l o c a l b u c k l i n g o r f r a c t u r e u p t o O mB ~

C o m p a r i s o n s w i t h t es t r e s ul ts

F r o m Figures 9 a n d 10 ( and the supp lemen ta ry f igu reso f Refe rence 14 ) i t can be seen tha t INSTAF gene ra l lyg ives conse rva t ive p red ic t ions o f the behav iour o fwe l d e d a l u mi n i u m me mb e r s . Th e l o a d s wh i c h c o r r e s -p o n d t o a c e n t ra l d e f le c t io n o f 3 0 mm a n d 6 0 m m f o rbeams wi th 1000 mm span and 2000 nun span , r e spec -t ive ly have been chosen a rb i t r a r i ly fo r compar i sons .Table 4 gives th e the ore t ica l va lue s o f Q3o and Q60obta ine d by us ing the m ean values of a0.2 and o~.2 (seeTables 2 and 3 i n I NSTA F. Th e m a x i mu m d i f fe r e n c ebe tween the measured and p red ic ted va lues o f Q3o o rQ60 given in Table 4 i s less than 10 , wi th the d i f -f e renc e be ing l a rges t fo r the fu l ly -we lded beams fo rwhich the add i t iona l a rea o f f i ll e t we ld was neg lec ted inthe s imula t ion s ince comple te fus ion ove r the i r fu l l

l eng th d id no t appea r to have been ach ieved . I t i s con-s ide red tha t the compar i sons o fFigures 9 and 10 andTable 4, when t aken in a s soc ia t ion wi th the ea r l i e rc o mp a r i s o n s o fFigures 5 and 6 , suppor t the gene ra la p p r o a c h t a k e n t o t h e a n a l y s e s o f we l d e d a l u mi n i u mme mb e r s .

a r a m e t r i c s t u d i e s fo r t ra n s v e r s e l y w e l d e dm e m b e r s

The two p rog rams have been u sed in a se r ie s o fparamet r ic s tud ies d iv ided in to two m ain a reas . Thesehave been des igned to p rov ide some bas ic in fo rma t ionon the e ffec t o f t r ansve r se we lds on the s t r eng th o fa lumin ium members . The c ross - sec t ions shown inFigures 11 and 12were used fo r s tud ie s o f in -p laneb u c k l i n g ( I NSTAF) a n d f l e x u r a l - t o r s i o n a l b u c k l i n g( B D ~ X L & L ) .

A m o n g a l l t h e c o m m o n l y u s e d a l u n t i n iu m a l l o y s ,6082-TF g ives the mos t seve re r educ t ion in s t r eng th dueto HAZ e ffec t s ; the re fo re , the fo l lowing mechan ica lp rope r t i e s o f 6082-TF a l loy were chosen fo r thepa rame t r i c s tud ie s

Parent

E - - 7 0 0 0 0 N / r a m 2

0 0.2 = 2 5 0 N / r a m 2

n = 25

2 4 8 E n g . S t r u c t . 1 9 9 2 , V o l . 1 4 , N o 4


9/14

S t r e n g t h o f a l u m i n i u m m e m b e r s c o n t a in i n g lo c a l t r a n s v e r s e w e l l s : Y F L a i a n d D A N e t h e r c o t

I8 0 m m ..J- I

I I Ilmm

20 0 mm7 mm

F i g u r e 1 2 Cross-sectionused for parametric studies (BIAX IAL)

H A Z

E * = 7 0 0 0 0 N / m m 2

(7~.2 = 1 2 5 N / r a m 2

n* = 10

IQ

I . Il Euler urve

O.S ~ Y L ~ L = 0.0 (Nonwelded)0.8

0 . 7 ~ \ ~ / o . IO.E ~ 0 2 ~O. ~ .0.3

0.4 ~ 0 (WhollyHAZ rnoter~ol)0.2

0 . 2 - - - ~ . . . . . ~o.

O o o15 ,Io ,15 2 ,o 2 .~ ~io A 4 0 ; 5 5

F i g u r e 4 C o l u m n c u r v e s f o r c o l u m n s w i t h H A Z a t m i d - h e i g h tin-plane buckling)

I.I I1.0

0.90 .80.7

i~. 0.6

0 50 4

0 3

0 2O, I

00

\ / Elastic criticx=l urve~ ~L~ = 0 (Nonwetded)

\ Y " / - L* = ,50 mm o, mid- height

" ~ / L ~= L (Wholly HAZmoteriol)

I I tO I0 .5 1.5

F i g u r e 5 C o l u m n c u r v e s f o r t r an s v e r s e l y w e l d e d c o l u m nsL * = 5 0 m m a t m i d - h e i g h t , f l e x u r a l - t o r s i o n a l b u c k l i n g )

In i t i a l geomet r i c imper fec t ions in the fo rm o f ha l f s ine

w a v e s w i t h m a x i m u m a m p l it u d es o f L / I O 0 0 a n d 0 . 0 1rad ians fo r ma jo r and minor ax i s de f l ec t ions and tw is t ,r e s p e c ti v e ly w e r e a s s u m e d . F o r I N S T A F o n l y t h e i n -p lane in i t i a l bow w as r equ i r ed .

P a r a m e t r i c s t u d i e s o f t r a n s v e r s e l y w e l d e dc o l u m n s

A l l t h e s t u d i e d c o l u m n s w e r e p i n - e n d e d a n d s u b j e c te d t oax ia l load on ly ; r e s u l t s a r e s how n inF igu r e s 13 - 15 .F igure 13 cover s the e f f ec t o f the loca t ion w i th l eng th

I

I000i

9 0 C

80C

70C

6 0 C

so c

4 0 C

3O

20(:

IOC

c~ L~ 'L0,0

C 0.1 At bothefldsO 0.1E 0.2F 0.3G 1.0

0 I. 0 I.Jl

P

Goi

pe l l o 2 o 1 3 '.4

0 OB

~ ~ O C o B

o ' . 5 o ' . 6 o ' . 7 o ' . 8 o ' 9P u l t / P u l t

F i g u r e 3 E f f e c t o f lo c a t i o n a n d e x t e n t o f H A Z o n u l ti m a t es t r e n g t h o f c o l u m n s ( i n - p l an e b u c k l i n g )

L = 1 0 0 0 m m (X x = 3 1 ) a n d a r a ti o o f l e n g th o f H A Zt o c o l u m n l e n g t h L / L * )o f b e t w e e n 0 a n d 1 . T h e l o c a -t i o n o f H A Z w a s s h i ft e d f r o m o n e e n d o f t h e c o l u m n t ot h e o t h e r. M o r e o v e r, H A Z l o c a te d a t b o t h en d s o f t h ec o l u m n w i t h l en g t h s o f 0 . 0 5 L a n d 0 .1 L w a s a l s o c o n -s ide red . F rom F igu r e 13 i t i s c l ea r tha t the max imumr e d u c t i o n i n c o l u m n s t r e n g t h o c c u r s w h e n t h e H A Z i sloca ted a t the mid -he igh t o f the co lumn , w i th the r educ-t ion inc reas ing as the l eng th o f H A Z inc reas es .

Brungraber and C la rk~ 5 have s ugg es ted thatt r a n s v e r s e w e l d s w h i c h p r o d u c e H A Z e x t e n d i n g f o r n o tm o r e t h a n 0 . 0 5 L f r o m t h e e n d s o f t h e c o l u m n h a v e a

neg l ig ib le e f f ec t on the buck l ing s t r eng th o f p in -endedc o l u m n s . H o w e v e r, s i n c e th e s t u d i es p r es e n t ed h e r e ins ho w s tr eng th r educ t ions o f a round 30 i t w o u ld appeart o b e u n s a f e t o n e gl e c t e v e n t h i s a m o u n t o f H A Z .

Figures 14 and 15 p r e s e n t c o l u m n c u r v e s f o rt r ans ver s e ly w e lded co lum ns fo r ma jo r ax i s in -p laneb u c k l i n g a n d f ie x u r a l - t o r s i o n a l b u c k l i n g , r e s p e c t iv e l y.T h e H A Z i s l o c a t e d a t t h e m i d - h e i g h t o f t h e c o l u m nw here i t w i l l g ive the m ax im um reduc t ion in s tr eng th . I tcan be s een f rom bo th f igu res tha t even a r e la tive ly s m al ldeg ree o f t r ans ver se w e ld in g w i l l l ead to buck l ings t r eng ths tha t a r e c lo s e to thos e o f a s imi la r co lum n con-s i s t ing w ho l ly o f H A Z m ate r ia l .

P a r a m e t r i c s t u d i e s o f t r a n s v e r s e l y w e l d e db e a m s

Res u l t s fo r the in -p lane and ou t -o f -p lane r es pons e o fbeams a re p res en ted inF igur es 16 and 17 . InF igur e 16 ,

E n g . S t r u c t . 1 9 9 2 , Vo l . 1 4 , N o 4 2 4 9


10/14

S t r e n g t h o f a l u m i n i u m m e m b e r s c o n t a in i n gl o c a l t r a n s v e r s e w e l l s Y F La i and D A N e t h e r c o t

I000900

8007 0 0

6 0 050040C

50C200

I 0 00

Curve L /LA 0.0 ( Nonwelded

o i At ~th ~l=C 0.1ED 0.20.3F i.o (Wholly AZmoterlol)

o[

i L i

011 I0.2 0,3 0 4

B A

F D C B

A1.5 0.6 0.7 0.8 09 1.0

Q u i t Q u i t

Figure 16 E f f e c t o f l o c a t io n a n d e x t e n t o f H A Z o n b e n d i ng s t r e n g t ho t b e a m s ( i n - p l a n e b e n d i n g )

w hen the app l i ed s t r e s s w i th in the H A Z i s g rea te r thanthe elas t ic l imi t s t r e s s , a*, o f equa t ion 3 ) . W hen thet r ans ver s e w e lds a r e loca ted nea r the tw o ends o f thebeam, the s t r e s s l eve l w i th in the H A Z i s w e l l be low a*and the beam the re fo re , w i l l behave as i f i t i s a s ing le -phas e mate r ia l . Bu t i f the t r ans ver s e w e ld i s loca ted inthe midd le o f the beam , the s t r e ss l eve l w i th in the H A Z

beco m es g rea ter than ae* , and hence , caus es s e r iousreduc t ions in bend ing s t r eng th .

The r es u l t s o fF i g u r e 1 7 s h o w h o w f o r b e a m s u n d e run i fo rm s ing le cu rva tu re bend ing the p res ence o f at r ans ver s e w e ld a t mid - s pan caus es s evere r educ t ions inl at er a l buck l ing s t r en g th a lm os t dow n to the l eve lo b t a i n e d f o r a s i m i l a r b e a m c o n s i s t i n g w h o l l y o f H A Zmater ia l .

I . I -

1.0. ~ \x \ L'~=0 ( Nonwelded

o.9o80.7 ~ / L * = L ( Wh011yHAZrnoterlol

, ~ 0 60.50.40.30.2O l

00 Or,5 1.10 1 5

F i g u r e 17 S t u d y o f t ra n s v e rs e l y w e l d e d b e a m s L * = 5 0 m m a tm i d - s p a n I f l e x u r a l -t o r s i o n a l b u c k l i n g

t h e l e n g th o f b e a m s e l ec t e d w a s 1 0 0 0 m m a s s u m i n g t Ls imp ly - s uppor ted ends w i th a cen t ra l po in t load under ~ oin -p lane bend ing . F o l low ing pa ramet r i c s tudy C1 , the 0 . 9l o ca t io n o f t h e H A Z w a s m o v e d a l o n g t h e b e a m f r o m o . e0 . 7one end to the o the r w i th d i f f e r ences in theL * I Lratio. , ~ o . 6T h e r e s ul ts s h o w t h at th e e ff e c t o f H A Z c a n b e n e g l e c te d o .i f the w e lds a r e loca ted nea r the tw o ends bu t tha t the 0 . 4m axim um reduc t ion in bend ing s t r eng th w i l l occu r i f the o .3H A Z i s l o c a te d a t t h e p o i n t o f m a x i m u m b e n d i n g 0 2m o m e n t . M o v e v e r, t h i s re d u c ti o n i s in d e p e n d e n t o f t h e O . od i m e n s i o n s o f t h e H A Z . T h i s c a n b e e x p l a in e d b y t h e os t r e s s - s t r a i n r e la t io n s h i p o f th e p a re n t a n d H A Z

m a t e ri a l o f t h e a l u m i n i u m a l l o y s s e eF ig u re 3 . T h eH A Z mate r i a l w i l l exh ib i t a r educ t ion in s t r eng th on ly

E x a m p l e s o f c o n t i n u o u s b e a m s a n d f r a m e s

S i n c e I N S TA F c a n d e a l w i t h t w o - d i m e n s i o n a l r i g i d

j o i n t e d f r a m e s a n d n o t s i m p l y i s o l a t e d m e m b e r s , s o m es t u d ie s h a v e b e e n m a d e o f t h e e ff e c ts o f H A Z a s m i g h tb e p r o d u c e d b y t h e u s e o f w e l d e d c o n n e c t i o n s o n t h ep e r f o r m a n c e o f s i m p l e a s s e m b l i e s o f m e m b e r s .

The f i rs t o f thes e concerns a can t i l eve r co lu m n fo rw h ich a t t achmen t to the founda t ion w ou ld p roduce anH A Z in the r eg ion immed ia te ly ad jacen t to the bas e .F ig u re 1 8 g i v e s c o l u m n c u r v e s w h i c h s h o w h o w t h e

o o 1 :, f

\ \ \ \ L~ = 0 (Nonw elded)~30 mm

60 mm* = L (Wholly HA Z moteriol)

I I I0.5 1.0 t.5

Figure 18 E f f e c t o f t ra n s v e r s e w e l d i n g o n s t r e n g t h o f a f i x e db a s e c o l u m n

T a b l e R e s u l t s f or f ra m e e x a m p l e o f Figure 19 ( Va l u e s i n b r a c k e t s a r e b u c k l in g l o a d s a t p in - e n d e d m e m b e r s . )

Lc )~x( m m ) ( c o l u m n ) E c c e n t r i c l o a d - Figure 19 a) C o n c e n t r i c l o a d - Figure 19/b)

Pu*kl Pu*it2 Pu~tl P ~ tlN o H A Z L * = 3 0 m m W h o l l y H A Z N o H A Z L * = 3 0 m m W h o l ly H A Z

P.=t Pu~t Pult P~ t

P .I t(k N) Pu*~l kN) P~it2(kN) Pult(kN) Pu~tl (kN) P~ t2(kN )

9 5 4 3 0 3 0 1 . 7 1 9 1 . 3 1 5 8 . 7 0 . 6 3 0 . 5 3 2 9 8 . 5 ( 2 7 8 . 7 ) + 1 8 3 . 5 1 5 5 . 5 ( 13 9 . 5 ) 0 .6 1 0 . 5 21 5 9 0 5 0 2 8 2 . 1 1 9 0 . 7 1 4 0 . 3 0 . 6 8 0 . 5 0 2 8 0 . 9 ( 2 3 6 . 3 ) 1 8 0 . 5 1 3 8 . 1 ( 1 1 8 . 7 ) 0 . 6 4 0 . 4 92 2 2 6 7 0 2 5 4 . 7 1 8 0 . 1 1 2 6 . 7 0 . 7 1 0 . 5 0 2 5 3 . 5 ( 1 5 8 . 5 ) 1 7 3 . 9 1 2 5 . 7 ( 1 0 0 . 1 ) 0 . 6 9 0 . 5 0

25 0 Eng . S t ruc t . 199 2 , Vol . 14 , No 4


11/14

S t r e n g t h o f a lu m i n i u m m e m b e r s c o n t a i n i n g l o c a l t r a n s v e r s e w e l l s : Y. F. L a i a n d D . A . N e t h e r c o t

Table 6 Effe ct of partially HAZ affected cross-section on member strength

Qp (kN)Degree of softening O,~, kN) Mp (Plastic

Cases on cross-section A/A (INSTAF) (kN m) th e o ry ) OplO , ,

| _

r -

I I8 0 r a m

J _ 1 4 4 4 m I Ir ' - " - 1

0

1 4 4 . 4 m m

,c,

144 . 4 mm

135mm'---~ l

-~ ~ 5 m m l Sm~m

U ... I-~ -- 70mm-~--2.4mmJ ' = ~- - 1 3 5 mmiP / J .f J J J . f J J J i J J ~ l I

9 m mI I

0.0 43.55 16.75 46.43 0.93 8

0.3 3 8.97 12.35 3 4.2 1 1.139

0.5 40.07 14.14 39.17 1.023

1 4 4 . 4 mm

O/(e ) ~

144.4 mm

~ - - 7 0 mm-~-

Ill'MIll.4 m-~-70 mm-~-- 9.4ram

~ - - - - ~ 1 3 5 m m

T ~ f f f / i l / / ~ I

~.~ .5.7 ~I l l I # 3 - - ~ i i - - t

- - ~ - 7 0 m m - - ~ , 5 .7ram

0.5 34.71 11.84 3 2.8 1 1.058

0.5 32.11 11.28 31.26 1.027

1 4 4 . 4 m m

v # ' J J f / J J / J / J I

J A r ~ r A r l

1.0 31.55 10.39 28.75 1.097

0

(g) ~..

- - - ~ .

k 4 4 4m m I

r J ~ / L / / J / / i l l

H 1.0 31.25 10.39 28.75 1.097

Eng. Struct . 19 92, Vol . 14, No 4 251


12/14

Strength of a /uminium members conta in ing /o ca / t rans verse we~Is: Y F La i and D A Netherco t

P

~T

L c L * = 3 0 m m

P

4~ ' L * IiI

L

_ L ; J ~ . ~ k . ,

I_ ~ l I_r -r - 9 5 4 m ma b

L * : 3 0 m m

9 5 4 m m--q

C o l u m n B e o ms e c t i o n s e c t i o n

I,--7 6 m rr ~ ._ I, ,,-76 m m q,I L

m m t /l l[4 '3m m / I4 ' ;mJ - - , ~ 1 5 2 rn m

J

Figure 9 We l d e d f r a m e e x a m p l e

presenc e o f even a sho r t l eng th o f HA Z in th i s c r it i ca lr eg ion causes subs tan t ia l r educ t ions in the m em ber sbuck l ing load , a lmos t dow n to the l eve l o f a w ho l lyHAZ member. Fo r the pa r t i cu la r conf igu ra t ion s tud ied ,t h e s t r en g t h o f t h e we l d e d c o l u mn wa s o n l y ju s t o v e r

ha l f tha t o f an equ iva len t unw elded co lumn , over mos tof the pract ical range of s lenderness .

Figure 19 i l lus t ra tes a two-har f rame for which i t hasbeen a s sum ed tha t the jo in t cons i s ts o f H AZ mate r i a le x t e n d in g 3 0 mm a l o n g t h e b e a m a n d d o wn t h e

Table 7 E f f e ct o f H A Z o n c o n t i n u o u s b e a m s

Case Co n d i t io n Qu it (k N) Quit~Quit Qp(k N)

(a) 82.8 0 1.0 69.6 4A D Z~

1 4 44 m m } _

Q A A

1 4 4 4 m m } 1 4 4 4 m m _ }

( b) _ _ _ 4 5 . 5 4 0 . 5 5 4 3 . 1 3~ ( b A , , , ,

0

(c) 60.86 0.73 60.80,, @ A , , , ,

0

,d, ~ (D ;"

(e)

0

6 1 . 9 0 0 . 7 5 6 9 . 6 4

4 4 . 5 0 o. 54 43.13

2 5 2 E n g . S t r u c t . 1 9 9 2 , Vo l . 1 4 , N o 4


13/14

Strength of a luminium members conta in ing loca l t ransverse wel ls : Y F La i and D A Netherco t

co lum n. Resu l t s a re p resen ted inTable 5 fo r 3 d i f f e ren tgeomet r i e s a s suming e i the r concen t r i c o r eccen t r i cco lumn load ing . These g ive the f r ame ' s u l t ima te loadde te rmined by e i the r a l lowing fo r o r neg lec t ing thep r e s e n c e o f th e H A Z a s we l l a s a t h i rd a p p r o a c h i nwh i c h i t wa s a s s u me d t h a t t h e wh o l e o f t h e c o l u mn wa sc o mp o s e d o f HA Z ma t e r ia l . Th e r e a s o n f o r t h e s li g h tl yh i g h e r l o a d l e v e ls f o r t h e c a s e o f e c c e n t r ic c o l u mnload ing i s tha t in th i s case pa r t o f the app l ied load o n thebea m is res is ted by the reac t ion a t it s r ight-hand suppor t .Clea r ly fo r bo th fo rms o f load ing the p resence o freduce d s t r eng th m a te r i a l a t the jo in t c auses subs tan t ia lr educ t ions in load ca r ry ing capac i ty, a lmos t down to thel e v e l s c o r r e s p o n d i n g t o a wh o l l y HAZ c o l u mn . Aswo u l d b e e x p e c t e d , t h e mo r e s l e n d e r c o l u mn s a r e r a t h e rless affec ted s ince buckl ing involves less ine las t icact ion .

The e ffec t o f HAZ mate r i a l be ing loca ted in e i the r apa r t o f a con t inuous s t ruc tu re o r wi th in a pa r t o f thec ross - sec t ion and ove r on ly a pa r t o f the l eng th o f ame mb e r h a s b e e n s t u d i e d b y me a n s o f t h e b e a me x a mp l e s o fTables 6 and 7 The f i r st o f these dea l s wi tha s ing le span beam fo r w h ich p rogress ive ly g rea te r p ro -p o r ti o n s o f t h e me mb e r a r e a s s u me d t o b e a f f e c te d . A l lo f the r e su l t s fo l low a p red ic tab le pa t t e rn , wi th theb e a m ' s s t re n g t h be i n g c o n t r o ll e d b y t h e r e d u c e d mo me n tcapac i ty o f the mos t h igh ly loaded c ross - sec tion . Sim pleca lcu la t ions us ing a t r ans fo rmed sec t ion concep t tod e t e r mi n e t h e r e d u c e d m o me n t c a p a c it ie s p r o v i d e v e r ygood es t ima tes o f the load ca r ry ing capac i t ie s .Table 7dem ons t ra te s tha t the p resence o f r educ ed s t r eng th spansin a con t inuous beam may be a l lowed fo r in a s impleapprox ima te w ay by cond uc t ing an ana lys is u s ing s implep la s t i c theo ry in wh ich the appropr ia te momentcapac i t ie s o f each span a re used . T h i s appea r s to wo rkpa r t i cu la r ly we l l fo r cases (b) , ( c ) and (e ) , fo r w h ich oneor more spans o f HAZ mate r i a l pa r t i c ipa te in the co l -lapse , bu t fa i ls to d is t inguish betw een cases (a) and (d) .No t su rp r i s ing ly fo r case ( a ) , a s ign i f i can t unde res t ima teis obta ined due to the neglect in the s imple p las t icapproach o f the a scend ing pa r t o f the ma te r i a l s t r e s s -s t r a in cu rve . On the o the r hand , fo r case (d ) themec han i sm approac h , s ince i t is conf ined to spans 1 and2 , t akes no accoun t o f the H A Z span 3 and thusove res t ima tes the load ca r ry ing capac ity. How ever, u sedwi th ca re , s imple p la s t i c theo ry appea r s to g ive eas i lyca lcu la ted , r easonab ly acc ura te e s t ima tes o f the co l l apseload o f pa r t i a l ly HAZ a ffec ted a lumin ium beams .

Conclusions

Co m p u t e r p r o g r a ms h a v e b e e n p r e p a r e d t h a t p e rmi t t h ein -p lane and ou t -o f -p lane r e sponse o f a lumin iummembers con ta in ing t r ansve r se we lds to be s tud ied .From the pa ramet r i c s tud ie s unde r taken the ma in f ind -ings a re

(1 ) For end-we lded co lumn s , i t i s unsa feto neg lec t the

s o f te n i n g e f fe c t e v e n i f t h e d i me n s i o n s o f t h e HA Zare sma l l .(2 ) The m ax im um reduc t ion in co lum n s t r eng th wi l l

o c c u r w h e n t h e HA Z i s lo c a t e d at t h e mi d - h e ig h t o ft h e c o l u mn . Fo r t h e c o l u mn c u r v e s , t h e b e h a v i o u ro f cen t ra l ly -we lded co lumns i s qu i t e s imi la r to tha t

o f a l u mi n i u m c o l u mn s c o n t a i n i n g wh o l l y HAZmate r i a l . Thus un le ss the co lumns a re ve ry s l ende ri t i s qu i t e accu ra te and reasonab le to des ign thecen t ra l ly -we lded co lum ns a s i f they cons i s t eds o le l y o f H AZ ma t e r ia l .

(3 ) For t r ansve r se ly we lded beam s , the loca t ion o f theHA Z ma t e r ia l a n d t h e mo m e n t p at t e rn a r e t h e m o s timpor tan t f ac to r s . Prov id ing s t r e s ses wi th in theHA Z r e ma i n b e l o w t h e a * v a l u e o f e q u a t io n ( 3 ) ,t h e b e a m m a y b e d e s i g n e d a s u n we l d e d .

(4 ) For 7000 se r i e s a lumin ium a l loys , the d ra f t BS8118 sugges t s a reduc t ion in 0 .2 p ro of s t r es s fo rthe hea t -a ffec ted ma te r i a l o f 25 . From the tens i l ecoupon t e s t s ca r r i ed ou t by the au thors , a f igu re o fapprox im a te ly 35 was ob ta ined . Th i s is in ag ree -men t wi th the f ind ings o f unpub l i shed work a tR A R D E .

(5 ) From the com par i son be tween the theo re t ica l ande x p e r i me n t a l l o a d - d e f l e c t i o n c u r v e s o f t h et ransve r se ly we lded beams wi th in the r angecove red by the te s t s , gene ra l ly good ag reem en t wasobse rved . Check s on t h e sens i tiv i ty o f thenum er ica l r e su lt s to the exac t se t o f inpu t da ta usedfu r the r conf i rme d tha t the s t r eng th o f t r ansve r se lywe lded members i s p r inc ipa l ly dependen t on theme c h a n i c a l p r o pe r t ie s o f t h e HA Z ma t e r ia l .

(6 ) Simple p la s t i c theo ry, u s ing ' p l a s t i c momentcapa ci t ies ' based on a0 .2 and a~.2 or both asappropr ia te , g ive r easonab ly accura te and eas i lyca lcu la ted e s tima tes o f the load ca r ry ing capac i t i e so f p a r t ia l ly HA Z a f f e c te d b e a ms .

cknowledgements

Th i s wo r k f o r m s p a r t o f a p r o je c t f u n d e d by R ARD E;the au thors a re g ra te fu l fo r a s s is t ance f rom Mr. D. Web -be r and Dr. P. S . Bu l son .

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67

8

9

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Hong, G. M . 'Aluminium column curves ' ,Aluminium structuresdesignan d construct/on (ed. R. N arayanan) E lsevie r Applied SciencePublishers, 1987, pp 40 -4 9Valtinat, G. and Muller, R. 'Ultima te load of beam-columns inaluminium alloys with. longitudinal and transversal we lds',Second/nt. Coll. Stab ility Prelim. Re p.Liege , 1977, pp 393- 404Dwight, J. B. 'Lo cal buckling of aluminium - preliminary pr opo sals',BSI Com mittee for Revision ofCP1 18, CSB/36, A/P aper, 28, March1982 (unpublished)Frey. F. , Lemaine, E. , de V ille de Goyet, V. .Jetteur. P. andStuder. M. FineI-G. Non-linear finite element analysis pro-gram users manual '. University of Liege. IREM Internal Report85/3, July, 1985Little, G. H. 'Collapse behavionr o f aluminium plates ', BSIC o m m i tt e e for the Revision of CPlIg, A/paper, 27 March 1981(unpublished)Mazzolani, F.Aluminium alloy structures PitmanNew York, 1985Ramberg, W . and Osgnod, W. R. 'D escription of stress-strain curvesby three parameters ', NACA Tech. Note 902, 1943Zienkiewicz, O. C. Theinite element method in engineering science(3rd edn) McGraw-Hill, 1977British Standards Institution Draft British Standards BS 8118, 'Codeof practice for the design of aluminium structures ', 1985Murray, D. W., EI-Zanaty, M. H. and Bjorhovde, R. 'Inelasticbehaviour of multi-storey steel fram es', U niversity of Alberta, Struc-tural Engineering Report, No. 83, April 1980

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S t r e n g t h o f a l u m i n i u m m e m b e r s c o n t a i n i n g l o c a l t ra n s v e r se w e l ls : Y F L a i a n d D A N e t h e r c o t

11 Gilson, S. and Cescotto, S. Expe rime ntal research on the bucklingof aluminium alloy columns w it h unsymmetrical cross-section ,University of Liege, Belgium (undated)

12 Gilson, S. and Cescotto, S. Exp erim ental research on the bucklingof aluminium alloy columns with unsymmetrical cross-section -complementary tests , Un iversity of Liege, Belgium (undated)

13 EI-Khenfas, M. A. and Nethercot, D. A. Ulti ma te strength analysisof steel beam colum ns subject to biaxial bending and torsio n ,ResMechanica 1989, 28 , (1 -4 ) , pp . 307-360

14 Lai, Y. F. W., Buc kling strength of welded and non-weldedaluminium mem bers ,Ph.D Thesis University of Sheffield, UK ,October 1988

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