Missouri University of Science and Technology Missouri University of Science and Technology

Scholars' Mine Scholars' Mine

Center for Cold-Formed Steel Structures Library Wei-Wen Yu Center for Cold-Formed Steel Structures

01 Jun 1939

Cornell University School of Civil Engineering Tests on light Cornell University School of Civil Engineering Tests on light

beams of cold-formed steel beams of cold-formed steel

Cornell University School of Civil Engineering

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Recommended Citation Recommended Citation Cornell University School of Civil Engineering, "Cornell University School of Civil Engineering Tests on light beams of cold-formed steel" (1939). Center for Cold-Formed Steel Structures Library. 1. https://scholarsmine.mst.edu/ccfss-library/1

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SCHOOL oit' CIVIL E.';Gr:~EERDW~, COR:HLL mIIVIRE:I'IY.

TEE,Tb ON LIGHT .E:.iUS O:J' COLL ~·OR.iED ~lrEEL

1J'OH 'rHE f~EF.IC,hN· If-OJ fu'!l) ~/l.E:rL I;.\IS':'I'lU'IE.

l!'OUR'lH PROGRESS REroRT, JU';{E e I 19Z9.

1. OJJECT OF 'I'P.l~~ REPORT •

. Buckiing tests huV'('· bl3en carrie"; Jut on. H.e rem3.iniu? three

t';t:t1:1lUS of thf: 22 (fags series, Le. B-22-812a. B-22..816a anc B-22-820a.

A stress curvey has ~cen made on th~ bQttoQ fl~~~e of bea~ B--22-8l2b.

A ~ew series of 22 Fa~e specimens has b~€~ desip.neu for the further study

(;f t·~·le b~)t talA flan&'e stresse;:; and of the t,1p .fl&Il/7e bucklin@'.

I I. ;i!:E'lHOD 01/ rfEE:'I'S.

Tup saIne methods of testin~ ..,':ere uS6d a8 described in the

1)t'(,Tlious reo')r"t.· It Vias f~l1.¢cl hf)~;JeV0r tLat the "pres ont meth'Jd ·:,f nl.:nmtin:·

Fi" ;.{uVf"p.nbr-:rpf:r strain j-a::: es ri':s'oJl ts i:.1 si.cori()ill:; (ift'icultiE;S ~n these

mtth~d )f Boplyin? the ~a~8s wil~bp e€vel~~e~ f~r furth€r invostiFation.

III. GlU'iPHIlAL RE.P.2:r~E.{~ArIOiJ G.;!' 'EiE. RESJLTS.

ThE r&sul ts ('1' th0 t uckl:i.nr tests 'lr:·' f.l'i von in thre'~ '.)f' the

tlCC,,)ffi?any in~'" rrap~ls ~ 'Ill ~ rf;sul ts :Jl' the strt;SG survey of B-22-812b Qre

tL)t incluciec: in t!'lis rqJ'H·t l'~;r rU';H3)nS r"lV8Il bcL)w. 'I'~e SUt?:-\:'stt?tl

(a:nensicns 01' thE. m;w series')!' sp0cif;';.ens will be f~)Und 0n the l'::tE·t

t· sheets.

f:1H:f~ts'26, 27, ::::8 !-,-ivt';o tl::f~ 10l:id doflr::cti;)11 curves of the UP,&:lG ;3-::':2-5120,

B-22-8l6a ClllC. B-22-8Z0a r~,s~E,ctilJ(~ly.

- 2 -

IV. BUCKLTI~G OBSERVATIO~S.

1}B-22-812a.

This beam failed ut about 2550 lh., w'ii:i ch corrE;sponcs to a

c')m~uted strf":ss of 126E'l{) p.£.L in t:1€ flant"8s. IIhe bucklinp was do-

t ected by thet;reak in the loae! (jeflc:ctio"l curve; at this l·')ut a slipht

l:)cal sh0rt lJrave appearec. at part "a" near mit:span .)I!. one siCe ·..,r the

flanf"e. (Part "a" see sheet 21). No f.ro;>pinr 'Ji' the load 0ccured,..-..

At a furt.cf"r incrE;ase .)f the load tt') 2700 n. ~ sud:.:i.en hucklin¥ \'rave famed

directly at nne Of the load ,Joints ane tt:e 18116 raoidly dr(~pp",d. In­

sDecti,)n revealed/ t:nat the t.'!') s~l.eets of part "b"i.had buckled separately,

t ~l€ bucklinf' "mves beiu;:; siiiffec with respect t,.) .:)11e an.;ther about 2"

and t.ll€: tc,p sheet havinp- bentu?,. the br)t t~!ll snE·€-t, d')1'.n. At this place the

s::>aciup ·)f tp.e S!:Dt welc.s is 4", v:b.Gre:as •)n t:lE: rest ~·f the beam. it i8 2" •

This eX'Jlains t:ie separate action :)1' the tw~) sneets.

2) B-22-816a enG B-22820a.

B-22-3l6a buckled at 2~80 lb. (10100 p.b.i.), B-22-8~0a

bucklec. at 2"50 lb. (7900 p.[j.i.). 'I'he bu~:kLinF' pr::·cesses :)1' these two

bf)am.s WE:re very much alike, altn')u;;.'h in ~,(~a(;1. !3-22-820a tht~ def!):rmatiun

I)f thA t;)il flatU'e ~ef';re huckliIli.~ tnk place, \'jas much &':reator than in

B-2~~-8l6a. r:'he t;~p flen;:.·E'.s ':.f b~)t h Dc'ainS as !'Qceived had sli,-"ht v,aves.

Ti:l~.se V'Cive6 iUCTF;;.tS(~: in t:;;;J.nlitud(· 'cl..r'lC:er lsaCi until, es~eciall~r '}u be&;n

B-22-820a the entire t-)!:> 1'l::m...!~" a:?peu.red i1ctivily 'tv·istcC:. Th,0;;;;e v;ere UJt

:O~1')rt tut l)nf' wavesl the lE.·no;'tr:. of :.me lUil,t' wave beinp ab:-ut ~ ft.

Buckl.ir.r. v'~lich resulted ill (:r:)~)l)in?" of the lQad, .::Jccurrei!. en t')th

t.car13 v...~('n a v f!l'y elip':lt sh:)'rt l::Jcal wave r,)1'tGE:.C! at paTt "utr. Gn bm:m

1::-::',2-820"1 t!H.; C.€"tc.. ")1' part "a" at :me sido 'WUI', ~J../4t1, at ·t;r_e ~·tner 1/2"';

b ucklinE? t:lJk place at the 1/2" side. 'I'll.is beum was f"urthf.:r ;.. ent lii·t(~r

I!l the f')llov··linr·table t ~:e f\ctual allC tht,> the-:r(;tlcal bucklin~

strf'SSES '=ire recorutJd for all flY·: bowns:)f' t:-.is se:ri(·s. The thc':'retical-'

-t!:;.c ,)tr..er; "ty')O 2" m0mlS U sll.1ilar ;llat.e, unsup~nrtet: at ::·1'1e edpe, but

';..

c0r:l)letely restrai~ed at the ·)ther. {See cccti,;:l V. of third ])r0f"reSS re::.n-t}

Table I.

Bucklinp strFsSBS Q~~ tv ~e. 'f' t'ailure

Beaiil C'}!!l ")ut8d critical stress 01' Actual FaileC

f\3rt "a It pa.rt "btl failure first ill

ty'J& 1 tyJ8 2 ty)6 1 tv·)c 2 ...~art.L .I. .'.'"

B-22-84a 51000 1~4000 ,..5200 119:)':) 14·500 b_...-....

B-22-S8a 12n:,o ~~,O()O 167DO ·;28Uf) Jr.::?2f\ a--B-22-812a 12?f.:0 ~.~()r_~o 6500 l'/i2'JG 12650 a

B-22-816a 51000 l~ i10CJ:J Z55~) 9?nO 1(11)0 b--B-22-820a 51000 l:?<!OOO ;3S~~/) 7400 ?900 b-f'~s a first l1:nr,)xit.latL.n it SOOiilS -thcrr:i'.;.l'c Cl:.>tu::: lis:b.ed, thatj1dTt "u" ()I'

-'

- 4 -

takec into acc')unt in desi~ninl! the }r8rJ~serl new s,1€cifUens.

T':'~e deflecti~ns)f the beams c:f this series under loads less

than the bucklinp- IJad d.) not Show the same ref-"ulari ty as in the series

A-14. A Iilcrked deviation i'r)!il the straiR"ht line is seen eS:J6cially on

t:16 l::>Bo deflectiJn curves ..)f I:l-22-81'6a anc, B-22-820 .. end a c'Jm:)aris:-m of

t'~lC actual and t:1.8 c.)ffi'-JutE':·d deflccti m rev"t.lls the followinf!' facts:

Table II,

COffi0arisJu of theoretical and actUtil doflection belo~

bucklin~ l0at (luBe Incre~ent P = 1200 lb.)

def'lectivnd

&.Bct

Series A-14

B-22-84a .;:;90

B-22-88a .200

B-22-8l2a .155

B-22-S16a .150

B-22-820a .160

the:>r

.268

.165

.119

.095

.078

dact/a

theJr.1.0

L08

1.21

1.Z0

1.75

2.06

It tl-tus appea.rs th:J.t with increasinr-' widtil (flexibility) of' thE- top f1anre

tl18 rl€!idi ty of t!:e heam as Q wi.lo1e rapidly (;&crcases; this takes place

not only near the buckli:w' load ijut throur"hout t"~f; 6ntire 10&(; ran07e.

VI. STR~~ OBSEEV~1IO~S ON B-~2-812D.

S train measurements were c~rritd out on six points on the

bottom flanpe of this beffin in the usual way. Since the results apP8arec

r8io1arkably irr':wu1ar) r€Deateo. reacini7s vri t~l resettinf' ai' the ~~a<7es '/J61'e

takell sir.lilal' to taose reported. on in section IV. of the secene;. ~rq-re~s

r€::Y~rt •. It wac observed t that the reaclin/?El:;rarieo. tn a sy&t8rr~:.;.tic v:ay

dr;p~mCii:"1f."mQ7: t'1e ('la.'1ner of inOlli'"ltinq tr~e f"arrLS, i. (;. Lifi'( rpnt reaain["s

ere obt sinee whea the mounti)'." rod was upplie{~ from one side of the ~age

or from the other sice. 'I'he cleviatic.as were too larue ( ... ~01[) to pro-• - .0

v~ce any reliable ~ata by avorapinp. It can only be said in th& most

cE'neral \"ay) that no marked chanpe in tne lrlupni tude of the lonrd tuc.inal

streGS8S U7p.r the width of the f1anfe takeo place. The o~served irreq-

ularities o0viously result fr0~ the followin~ fact: The lrroUllti~r device

us~d is similar t~ that designed by B€p~s & Tinby (Eng. News-Record,

~arch 17, 1928) except that the h~erhead of this df;si~n is replaced by

a calibrated snrin¢ support. It is easily seen that a relative motion- .of the point, vlhere this support rests, will : a transl~i tted throUf:'h the

ffi:Juntinf"' rod to the papa ant: thus will affect the reading. Obviously

such motion occurs: b. the flE:xi-ble li/?ht ["age t'lanf?es, resultln~ in a

certain twistiu:7. of the. flanpH. This is <:;sp0cially likely in the beam.

~'s

under con::.idt'lratir.n, since t.he 'tJ' tla.i.1pe 0f this b08lll.,received was not ht

rib"ht ant-les to thE, WEb andhence the bCU1t vas b:mnd to twist u::ld€r l,:,ad.

It theref')re a:>')ears necessar-J t:· develc:p a nev: 1'1;jUlltin,r,' device for the

if n·)t C8nnectea with a remctf:: p~Jint of tilt: 1'1:';ln~·e.

c ·uld be carried r~ut 'In bea;TI5 B-22-816 anc.~ B-~;2-820 I since hucklin/7

r'CCUTf)Qnt suetl L'wJ stresS8s, th~lt 00 sufficient l)grj ra,'1f'e for stress

(;ctcnninutbns is aV(l11able.

,~vrI. CONGLUSIO~S.

1) 'I'fir.: bucklin~ jf the t0P fla...'1p€ or: :ill fi V2 beauts teGted Jccured in a

rer·uV.:.r manner ruided by the formulas fti VC:'J1 in section VIII.

2) The beams under c'~;nsideruti')n snowed U ll1url,::ed C:ecreas€ ill ri :"idi ty

wi tn incrHlsin~· f".1a:l(1'E: V;iC;ttl. 'l'i.is tact re3ulteo in heavy twistin@" of thp

- 6 -

tJ~J .t'lUL1['e under l:)l::l.cs muci-l belli'! t'lC: ul tit:l..::lte bucklin;:: load. For t!11s

rcas"-,n t!l€ le-a'l Gc,floctLm curves ,Ji' theM; , eaIns show a clear depax-ture

fr,·m tne straipht line) especially 1'Gr the wide 'lJe8Jns, and an actual de-

flecti,)ll much .9'reater than the :me c)moute~ for a rip-H; cross section.

~) ::?urt!ler tests are necessCl.I"J t::· investip.b.tc bC)tI:D. ')f these problems.

VIII. DESIQ'l OJ!' THE NEXT SERIES OF SPECIMENS.

In order t" co:nplE:te t~!e stress 5urvey on the b()tt·~m

tlanpes of th.e 22 f:"a~e bea::ls it appoars UGCOBE,<;l.I"'! t:) iluve &"uther series

of these bea.'1ls with increased ril:,dC::i ty :)i' tlu: t:)p f1anr6. The results

menti')uec in secti,m V. t)f tnls refnrt were u:'JGti t-::J' acsi&"n the new

specimens on the: asis Jf a SUPP~)S6u ::mcklJ.n? ~tr(;Scj rrr.' 400000 p.s.i.

6"" cri t = lZZa (100 h) 2b

GoJ

cri t ~ 2500 (100 2:,) 2b

"type lIt railure is to be €'x-rocted ar,d

f~~ the part ~f the f18~~6 of a

h - t!liclGlf;';;S of the -part ')f the flane€: under c:mstd.erat i:'n

():: free wiath II 11 n " I'

It is expectec. ti1at tu«se bea:.as ...,ill n~:t t:,n ly serve f(Jr

- 7 -

~cans ~f this series will ho tested to failur~ with these stiffeners

cut off in order to diE,cern purE: Luckl1uf" a.nC twiGtinr;: action. which

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