Cooper, P. B.

Yen, B. T.

English

Lehigh University: Lehigh Preserve

Lehigh University
Lehigh Preserve
Fritz Laboratory Reports Civil and Environmental Engineering
1963
Fatigue tests of welded plate girders, Welding
Journal, Vol. 42, No. 5, May 1963, Reprint No. 220
(63-6)
B. T. Yen
P. B. Cooper
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Recommended Citation
Yen, B. T. and Cooper, P. B., "Fatigue tests of welded plate girders, Welding Journal, Vol. 42, No. 5, May 1963, Reprint No. 220 (63-6)"
(1963). Fritz Laboratory Reports. Paper 1694.
http://preserve.lehigh.edu/engr-civil-environmental-fritz-lab-reports/1694
\. \
WELDED PLATE GIRDERS
FATIGUE TESTS OF
WELDED,PLATE:GIRDERS
B. T. Yen
Peter B., Cooper
Fritz Engineering Laboratory Report No.251.26A
FATIGUE TESTS OF WELDED PLATE ~IRDERS
Submitted to the Plate Girder Project Committee
for approval as a news item for publication
in ~,theWelding Journal Research Supplement
, , '
B. ,T. Yen
,and
Peter B. Cooper
Lehigh University
Fritz Engineering Laboratory Report No. 25l.26A
July, 1962
251 -1
Tests on two full~size welded plate girders were recently conducted
at Fritz Engineering Laboratory, Lehigh University, to observe the behavior
under repeated loading of girders with .slender webs, to investigate the
applicability of the design recommendations(l) to bridge girders, and to
obtain preliminary data for planning further studies of the fatigue
strength of welded plate girders.
As shown in Fig. 1, the test girders were 40 feet long, and had
12" X 1" continuous flanges. Cover plates at reaction points added to the
stiffness of the girders to keep vertical deflections within the limita-
tions of the test equipment. The 50-inch deep webs were composed of 3/8-inch
plates at the ends and 3/l6-inch plates in the central test sections. The
only difference between the two girders was the spacing of intermediate
transverse stiffenera in the test sections.
The test section was subjected to high, uniform shear and a linear
moment gradient through the loading points at the girder ends and the sup-
ports at quarter points (Fig. 1). The loading condition was such that a
shear failure would occur under high static load. .Two hydraulically opera-
ted jacks(2) at the loading points were connected to two pulsators provid-
ing sinusoidally varying oil pressure at 250 cycles per minute thus exert-
ing repeated loads on the girders at the same rate. In order to prevent
tilting of a girder under load, the compression flanges were laterally
braced. An overall view of the test .setup is shown in Fig. 2.
A load range of half-maximum to maximum was used. Figure 3 shows
the test loads and the sequence of testing for the two girders. Girder F1
251 -2
.0
was subjected to a maximum load of 88 kips. The first crack occurred at
1/3 million cycles. Girder F2, which had panels smaller than those of
girder F1, had a load range of 46.5 kips to 93 kips and the first crack
was observed at two million cycles •. At two and half million cycles, and
after a repair, the maximum load was increased to 110 kips. Repairs by
welding subsequent to the formation .of cracks permitted trying different
repairing methods as well as continuation of testing to obtain additional
fatigue information. Girder Fl failed at 4,077,000 cycles when it could
no longer resist the applied load because of excessive cracking. Girder
F2 had been subjected toa total of 3,277,000 cycles when the test was
stopped.
The variou~ cracks which formed during the testing of girders F1
and F2 are sketched in Fig~. 4.and 5, respectively. It can be seen from
these figures that all cracks in the. test sections occurred in .the web,
either along a flange or along a stiffener. A typicat·~tack started as
a tiny hair line on one' side of the.web at the toe of the fillet weld,
then penetrated through the web gradually while increasing in length. For
a crack length of a few inches, no effect on the .behavior of a girder was
detected.
In testing the girders a phenomenon was observed which generally
does not occur in beams under repeated loading: the thin webs of the
girders deflected back and forth transverse to their own planes. The
amplitude of this deflection between the maximum and the minimum loads
was more than 0.2 inches at some locations.
251
-3
It was reported recent1y(3) that tension field action is an impor-
tant factor in the evaluation of the shear carrying capacity of slender
web girders. For the two shear girders F1 and F2 where tension field action
developed, the test results lie in the same general domain as other fatigue
tests on welded plate girders or beams: depending on the loading range and
its relation to the strength of the specimen, the fatigue life can be long
or relatively short. Both girders were subjected to severe loading.
Girder F2 had a maximum load equal to.]l% of its computed static strength.
\
It sustained two million cycles without the development of any visible
fatigue cracks in the three test panels. In girder F1 the two panels were
longer than those of girder F2 and thus were weaker. The maximum load was
83% of the static strength. Although ,a crack was observed at one-third
of a million cycles in one panel, the other panel stood for 1·2 ,million
cycles before any cracks developed.
Certainly the results of tests on only two girders do not provide
enough data to draw precise design reconnnendations for bridge girders; but
the results are most favorable and encouraging. With the guidance of the
results described above, further research is continuing on the fatigue of
welded plate girders.
REFERENCES
1. K. Basler
"New Provisions for Plate Girder Design".
Ptoceedings, AISC National Engineering Conference, 1961
2. "B. Thur1imannand W. J.Eney
"Modern Installation for Test,ing of Large Assemblies under
Static and Fatigue Loading"
Proceedings, ,SESA, Vol. XVI,. No.2, 1959
3. K. Basler
"Strength of Plate Girders in Shear"
Proceedings, ,ASCE, Vol. 87, No. ST7, 1961
P1- Test sect~
GIRDER FI ~ 12
I XI"\
I I 3 II I 3/16"Weld
I I
I Ye I ,~ I I
I Weld I ~ I JI
1--10<-0·--1
.~ ~
31-g" 121-6" 31-9"~ 101-0" .
.P
T
50'
1..
P
EAR P(kips) II I
GIRDER F2 ~ 12"xll~
I 3 II I p 3/16" ,~ I II Ye I I II Weld I ~;). Weld j~ I I
n
"
T
5d
..i
p , -------401_0"----------1
I I
I I
SH
I
I
I
I
MOMENT
I'
I
I I
I I
! 120p (k-inJ I
I
I
Fig. I Test Girders and Setup
Fig. a Overall View of Test Setup
fcrackA
GIRDER F I I
rCrack C
O..L---~-_.....I-_-_----l---L L.----=- ..L.L..__
o l I l2 3xl06 cycles 4
Welding A Welding B
p
IGIRDER F21 r
crack A
rcraCkA rcraCk B
.-
O~---_.....I-_--_--L_--+--_L...---l.:---- __
o 2 l 3x 106 cycles
lWelding Awelding A
Fig. 3 Testing Loads and Sequence
.., . .\ ,. .
y
•~ r'" .-
T i ~ A ,.~ ) I II GIRDER I I II I I C I
I FI I iCD:-X I I1 I II I 1
I I I ~
x= -75 o
B
y
f
t Reinforcing
Stiffener
II I
::--IOu--t-- 10"
II
II
Fig. 4 Crock Location and Repairs 1 Girder F I
'.-."-.'." -, '.
p~
I
+75+25
y
-25-75x :0
~ ,
1 i ; I I T IQ ~ '" I II GIRDER I Cl -t-- I I• -x l.J I II F2 I I II I .A : 1I I : :
I I I 7Ihr
I II I IIt 7 V2_I. 7 V2_\
II
II
II
x - ~__II- _,,=,"",*-...L
t Reinforcing
Stiffeners
A
x
x-~-
B ~Stiffeners
x =+75
x
Fig. 5 Crack Location and Repairs, Girder F 2



Fatigue tests of welded plate girders, Welding Journal, Vol. 42, No. 5, May 1963, Reprint No. 220 (63-6)

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Fatigue tests of welded plate girders, Welding Journal, Vol. 42, No. 5, May 1963, Reprint No. 220 (63-6)

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