Lyse, I.

English

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Lehigh University
Lehigh Preserve
Fritz Laboratory Reports Civil and Environmental Engineering
1933
Tests of reinforced concrete columns, Civil
Engineering, Vol. 3 (1933), p. 366-368, Reprint No.
34 (33-10)
I. Lyse
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Recommended Citation
Lyse, I., "Tests of reinforced concrete columns, Civil Engineering, Vol. 3 (1933), p. 366-368, Reprint No. 34 (33-10)" (1933). Fritz
Laboratory Reports. Paper 1151.
http://preserve.lehigh.edu/engr-civil-environmental-fritz-lab-reports/1151
•...
.,fRITZ £"~G1;'~E[:~~~ 'Li-\BORATORY
-'.. LEHIGH UNIVERSITY .
,\,=~ETHLEHEM,P£NNSYLVANJA
TESTS OF REINFORCEDCONgRE'I'ECOLUWIS
'by Inge Ly'se*
..DrrRODUCTIQN.·
i'be re·inforced eon.erete.<}'()lu.um '1nvee.ttgation sponsore'cl
. .
by the. American .Concrete. Insti tuteandtoward Wh1cl'1th~, -.e1"1-·, ,
can SQcie·ty of 01\.,11 J$ngineer,s oo,ntrlbuted finanotallr t has·es'",,:
. . '. ..\ '.' .' .
.
tablished ,eertainrelationships between the properties ot th~
mater1aJ.sand the strength of .the column. The ultimate strengt'h
of tIle eolumns has been found 'to be IlUide up of the strength. of
the' concrete "(column ·s'trengthequal to about 65 per cent of the
oylinder ,strength). and the yield-point strength of tbe longi'tu~
dinal -st~l.· ,For .columns havingsplralrelnforeement whieh pro-
,duoed str'erigth in exces:~Of th~$trength ·o,f the: rirecproot1n£.s
shell;thestr:ength ot the column was ,increased by the spiral.,
Since' alleolumns ,included 1n tIle ,inve.stf~ationhad longitudinal
re1ntorcemellt of' only & per cent and lee's; lts-eemed 1mpel:t'allt
. . .... • .
tha.ttests· he made on' ~()l~s ha.ving' greater per~entage'so~ ~e';
int·orcement. '. Consequently '~he- Fri~,z EngineerIng Laboratory o,t
Lehigh university earr1edoutan' invest1gati'0l1 OllCOJ.umns having
. ,
. .
. as much as 17-~/2 per cen:t 1~ng:1tlldina.l re1ntorc&m~nt~'
Furtbermore t 'tests' 'lter'e·mad:GGll,columns which had' a ve~ry
" ,high:. grade ,~teel.tc~X"einforeementend on ·coltUnlls whioh had weld-
ed reintordemellt •
* Res,aaron Assistant PrefessorQf Engineering J1tlaterial's'
'. Lehigh Ul1iversfty, Bethlehem, Pennsylvania
- 2
. POOGRAM .AND J?li.OOED'{JBE
This series of tests included a. total of 42 c·o.lumns
8-1/4 in. indi,amete'r and 60 in. ~ong. .The p1;ogram tor the
testa1a given in.' Table J..
Two coneret~St of 2000 and 4000·lb. per sq.ln. 'designed
strength. we,re used. Plain columna were made wl~h. ~aoh gr~d.
of concrete. For 2.0 per eentspiral reintox-eement, the per- .
eentages of long!tudinal reintoro'ement' were 1-1/2, 6. 10--1/2,
. 14 and 17'-1/2', With long1tudinalreinfo:rcement 01' 14-per cent
_... .
the spi.ral reinforcement was. either' 0, 1..20·r· 2.0 peroent.
The harsin the columns having 1-1/2 and 6 per cent reinforce-
ment were of thesaxne 'stock: as those used tor reinforoement in
the A.C.l.column investigation. The yield-point stress was
47,800 lb. per sq.in. tor the 1-1!2per'eent reinforcement and
44,900 lb. per sq.1n.tor the 6 per aent 'reinforoement. The'
bars in the co1umns 'haVing 1~"'1./2;, 14 and +'1-1/2 per cent re-
inforcement were 1-1/2 in. in diameter and had an average
yield-point stress of 35,900 lb. per sq. In. ·The splra~s. came
frOm the same stook'as tl10se used in the A.C. I.' 1nves~lgatlon.•
Noy1e1d p,ol,nt o.ould. be determined :from the. tests of the spi.-:-
ralcoupons.. The ultimate strength was 82,200 lb. per sq.ln•.
·for the 1.2 per oent spiral ·and 71:,560 lb. per sq~,in. tor the
.. 2.0 percent sp1ra1. Add! tiona! tests were made 'on c·olu..'1lIls
in' which the 6 per oent longitudinal reinforcement consisted
of bars havingy1eld-point stress of 94,500 lb. per ,sq. in. and
- :;
ttl:t1m.ate strengtho·r 1.32,500' lb. per sq.in,. Tests were also
made on ·columns which M.d 1? ...~/2pe,r ,oent~111toroemant where.
each bar was cut' in hall'and:we.ld.ed togetlla'r eleetr1'()~11y be-
from the same supply., and the m~thQd of ma.k1ng.~ ourtng, and
testing was tIle saI'IJ.eas that us~d in. the A.C" I.invest1ga.tlQn.
(See Lehigh University Reeearoh Circulars No. E?4 and 81). ,,A
photograph ot thereinforo1ngun1ts u~ed f9r~4per e~t ~on­
gitudlnaland no spiral reinforcement. is shown in Fl~. 1.
DISCUSSIOIiOF RESULTS
Both conorete -mixes had the smnev/ater ·content per
ciubic~ard ,of 'C!'0ncrete. The ave~ageslumlls tC?r the ,e~ne~ete
'we.re 6.3 and 7.6 to-r 'the '2000 lb. and 4000 lb.pe-r sq·.in.
. .
mixes respectively. A summary Qtthe results of "the 't,ests
is given in Table 2.
It is noted that the strel'.lgths :o-fbothcollcir-et~mixes;
remained fairly constant for all the columns. The uniformity
in strength 'resultsot companion ·oolumns was very good through-
out the. tests.
The load-deformat lon-o.urves, are sh:own' 1nF1g. 2· and
3 toreolumns having design' strengthsot c'oncrete of .2QOo- and
4000 .lb.per sq.1n. respeotively •. In Fig. 4:: therelatl~n be-'
tween the de,fomtion ·of the ~ong1tud.inal reinforcement and
4·
tIle loadoarried by the reintoro:ement' is sh:own for the vari...
ous percentages us·ed. OncOft?paring the d.lagrams ofF!g. 4
with'those of' Fig•. 2 and3.ast-rikingsimi~E1rity is noticed.
. ,
The distances between. theQurves~or the,va.rious peroentages'
ot reinforoement fire very nearly the same 'in, the' 'thr.ee fig-
ures, indic,ating that the· steel is giving its fUll s·tress
value to the column .atany strain. .regardless of the amount
or grade of steel. Except :f'orthe columns having only 1-1/2
per cent and' 0 per cent longitudlnal'relnforcement,a'sharp
break in the deforma.tion curves atstra1ns corresponding ap-
proximately to the Y1e~d-pointst.re.inofthe reinforeement
indieates: a. yield point. of theoolumns•. The greater the per-
cel1tages of longitudinal re'inforcement, the sllarper is the
break in the deformat·1oneurves. It is not·eel that the deform-
ationcurvesfor the columns ha.ving the High. Yield point stee~
showed a greater increase in load with' increase in the strain
beyond the yield point than did the curyea foroolumns.having
. .
'mild steel•. This is evidently due to theta-at that the High
Yield .Point st'eel did not have a sharp yield point. The test-·
lng' machine, showed no drop or the lever at· the yield pOint of
this steel. which yield poin't had to be determined .from the
stress-strain diagram. The strength results indicate that at
the maximum load' of the coltllDllsthe .High YieldPo1nt steel .
carried load oorresponding to 120 per oent of its yield-point
strength. Attentton is called to the faot tXtat the totald.e.·
formation at. the yield point of the column was more. than twice
as large ·tor the ~1gh Yie~d.Po1nt steel' as tor the. ord~nary
re1nf·oroingstaeJ.. Thus the a.m.ount 01' t1.ow in a column ~y
be 'doubled before the yield-point stress of the steelh8.s
, . .
been reached. Sponsors of design -for efffJct o:t flow on s·tress
in retntorcementshtJuld therefore welcomErthe ;introductionot
theHlgh Yield Point steel. The advantage of this .steel on
the strength of the col~ is, furthermore, so outstanding
thatspeclal attention should be given to this typeo.tsteel.
The effect of the amount of spiral. reinforcement on
tile deformation o:r the .columns is .illustrated in ·Fig. 5~ The
deformat1oncurves for columns having no spiral, and those
having 1.2 per cent spiral reintor·eement are seen to very
. .
nearly c.oinelde t both for 2000 and. 4000 lb. par sq.1n. con-
crete. The deformationeuxvestor the columns having 2.0
per cent spira.l, however. are somewhat steeper than .for the
othercolunms.. This' ispart1ydue to the dit:f'ere'nce' in the
strength of the conere·te. in thee.olumns.. Table 2- shows that
the strength of the.cl,oneret·e .used in the .Qolumnshaving 2.0
per cent spiral reinf'orc'ement wae',;about ten percent higher
than the concrete used in the columns having no. spiral or 1.2
per cent spiral reinforcement. Whencorreetions are made for
this diff·erence in the. strength,thede~o:rII1ationcurvest as
well as the yield point or the oolumns, would vel-y nea.rly
coinoide for theoolumns having var~ous amounts of' spiral
reinforcement.
STBENGTHBESULTS
Tlle'strengths ,of all the columns' are given in Table 2.
The strength.s ofeal._shaving 2.0 per eentsplr.al reinforce-
ment have .bee~ pl:otted 'a~1nst they1eld....point strength of' the
longitudlnalra1nfQrcement·in Fig.' &. This figure proves eon-
elusively that the longitudinal re1n.toroement adds its full
yield"'1;>0int strength t.o, the-co~umn. r;egardless ot' am0W'lt, up
to 17..1/2 per cent reinforcement. The high y1.eld po·int .steel..
is found to contribute 'an amount of load corresponding tl,) l20
per cent ot its yield-point. s.trength ·to tIle strength of the
column.. FurtherDlore, the parallelismot the curves in Fi.g. {)
shows that the grade of concretehae no effect upon the
strength added by the longitudinal reinforoement • These re-
sultsarein harmony with those obtained in the A.C.• I. ·.column
investigation, in which a maximum of 6 percent longitudinal
reinforoement was used•.. It may therefore be cono'ludedthat
for reinfol--ced concrete eolunms havi.ng ~ess than 17-1/2 per
c'ent longitUdinalre1nforce.ment.,.thestrengtho:t tIle column
1sequal to the strength ot the ooncrete1n the eo~u:mn"plus.
the yield-point strength of thee longitudlna1relnfQrcemel?-'t
plus whateverarnount i·sadded by the-spiral re1D.foreement.
The tests 1ndicatethat the strength added by.thespi-
ral rein:foreement is approx.1mately equal to two times' the
y1eld-po1ntstrength of the spiral less the amount ot ~oa.d
carried by the protective shell outside 'the spiral.
7.~m!JIARY
1 •. The deformation curve of reinforce,d concrete
co.lumns having ten per cent or more longi tUdinal reinforce...·
ment 'showed a.. definite Yield.point. Thi:6 yield-point strain,
corresponded .appr·oxima'tely to the yield-pointatrain of. the
longltudinalreinf'orcement.
2.1'he columns havingh1gh grade steel gave yleld-
point deformation more than tw1(n'~' as large 8..S did columns
ha.ving ordinary reinforcing s.teel.
3.. Thelongitud1nal reinforoement a.dded its' tull
yield--point. strength to the eo·lumnfor. asmuohas 1?-1/2
per oent reintorcement,. the largest amount used in this 1n-
vest1.ga.tion.
. .
4. The high yield po~nt steel added about 20 :per
cent in excess of its yield-point strength to the strength
of the column.
S. The strength of tied columns' and of spiral columns
in which the spiral reinforcement hade. strength' equal to or
less tha.n the 'strength of th.e protect1ve s·hel1:~. is equal to 85
per cent of' the cylinder . strength of the concrete times the to-
tal area 01" concrete., plus the' yi eld-pointst,ress ot the longi-
tudinal reinforoement tiIrlOs its .area.
6. For design purposes the e·tteotlveness ratio of the
spiral reinforoement may b.e considered equal to 2.0.
-'\.


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Fig. 1 - ourteen Per Cent
Longitudinal Reinforcement









Tests of reinforced concrete columns, Civil Engineering, Vol. 3 (1933), p. 366-368, Reprint No. 34 (33-10)

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Tests of reinforced concrete columns, Civil Engineering, Vol. 3 (1933), p. 366-368, Reprint No. 34 (33-10)

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