Marek, P.

Tall, L.

Tebedge, N.

English

Lehigh University: Lehigh Preserve

Lehigh University
Lehigh Preserve
Fritz Laboratory Reports Civil and Environmental Engineering
1969
Column testing procedure, June 1969
N. Tebedge
P. Marek
L. Tall
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Recommended Citation
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http://preserve.lehigh.edu/engr-civil-environmental-fritz-lab-reports/380
3S-1./ 2c
by
. N. Tebedge
P. Marek
L. Tall
European Column Studies
COLUMN TESTING PROCEDURE
BY
Negussie Tebedge
Paul Marek
Lambert Tall
Fritz Engineering Laboratory
Lehigh University
Bethlehem, Pennsylvania
June, 1969
Fritz Engineering Laboratory Report No. 351.1
351.1
TABLE OF CONTENTS
ABSTRACT
1. INTRODUCTION
2. INITIAL MEASUREMENTS AND ALIGNMENT
2.1 Out-of-Straightness
2.2 Cross-Sectional Dimensions
2.3 Alignment of Specimen
3. INSTRUMENTATION
4. TESTING PROCEDURE
5. SUMMARY
6. ACKNOWLEDGEMENTS
7. TABLES AND FIGURES
8. REFERENCES
1
4
4
5
6
8
9
12
14
13
28
351.1
ABSTRACT
This report describes the instrumentation
and testing procedure proposed for the project "European
Column Studies"underway at Fritz Engineering Laboratory,
Le high Uni ver s i ty, Bethle h em ~ p'ennsy Ivan ia .
The purpose of this study is to gain
experience in the testing procedure and recording needed
for the project sponsored by the European Convention for
Constructional Steelwork Association, the National Science
Foundation, and the Welding Research Council. Some
preliminary tests on u.s. heavy shapes similar to the
European manufactured heavy sections were undertaken as
part,of the study.
This report summarizes the final proposal of
the instrumentation and testing procedure for the columns
to be tested to furnish information to be used in the
preparation of design specifications of the European
Convention.
351.1
1. INTRODUCTION
-1
The European Convention of Constructional
Steelwork Associations(ECCSA) is studying the conditions
by which the results from their basic research program
on column shapes with small ,dimens ions and light weights
can be extended to heavy columns.
According to the Test Program on Experimental
Studies of Buckling undertaken by Subcommittee 8.1 of ECCSA
as described in Ref. 1, the application of the column curve
o?tained from the statistical test program may not be valid
for sections of large dimensions and with heavy thickness,
nor for certain types of sections built-up by welding.
"Heavy sections" refer to columns larger than the section
HE 280 (equivalent to u.s. 12 WF 133) and "heavy thickness"
refer to the order of 30mm (1 1/8 inch) and higher.
Fritz Engineering Laboratory of Lehigh
University is conducting the program on the heavy shapes.
To obtain conclusive experimental evidence with the minimum
costs the program was restricted to the shape HEM 340
(equivalent to the U.S. 12 WF 161) and to two slenderness
351.1
ratios, 50 and 95. The two slenderness ratios were
-2
chosen on the basis that they belong within the most
critical range according to theoretical and practical
considerations. A total of 24 columns (12 per slenderness
ratio) will be tested.
In order to gain experience with the new
procedure and instrumentation as required by ECCSA, some
complementary tests were conducted at Fritz Engineering
Laboratory on a U.S. shape 12 WF 161. The method of
testing proposed for the European Columns(l) differs from
that used in the recent past at Lehigh University. This
prompted the investigation of the test methods; conclusions
and recommendations from the comparison study are given in
Ref. 2.
For the tests on the European columns the
- d - - d d (1) -II b drequlre lnstrumentatlon an proce ure Wl e use to
avoid introducing any new variables which may affect the
statistical evaluation.
However, the experience from the pilot tests
on the 12 WF 161 columns, the results of which are discussed
in Ref. 2, indicates some clarifications and adjustments.
351.1 -3
These, together with a description of the instrumentation
and testing procedure, are discussed below.
351.1
2.
-4
INITIAL MEASUREMENTS AND ALIGNMENT
The following data will be collected for each
column. The ECCSA requirements are presented within
quotation marks.
2.1 Out-of-Straightness
"Initial flexural curvature of the test specimen
will be measured in the two planes of symmetry
of the section."
Figure 1 shows the method for measuring initial
out-of-straightness using the theodolite and the movable
carpenter's frame square with a strip scale attached to it.
Out-of-straightness (x) about the weak axis
is obtained from four readings - one with reference to each
tip surface of the flange (Fig. lb). For the theoretical
evaluation, the values for each flange may be obtained
separately. The average of the four readings is taken as
th e aut - of - s tra igh tne 8 s, 0 f th e whole 8 ec t ion.
Out-af-straightness (y) about the strong axis
is obtained from ~he two readings (Fig. Ie). The average
351.1
of the two readings is taken to be used for theoretical
prediction.
-5
In Fig. 2, a plot of the readings obtained
for a typical column from the Comparative Study(2) is
shown.
The flexural curvature is obtained from the
measurements made at nine levels, each spaced at one-eighth
of the column length.
2.2 Cross-Sectional Dimensions
"Cross-sectional dimensions as shown in the figure
below* at preferably five sections (but at least
3 sections) along the column: the two ends, in
the middle and possibly at the quarter and three-
quater points."
The cross-sectional dimensions are measured
at five locations - the two ends, the quarter, the middle,
and the three-quarter points ..The measuring tools used are:
Thickness and depth - vernier 1caliper (1000 in.
·sensitivity)
. . 1
Web thickness - depth IDlcrometer (1000 in.
sensitivity, Fig. 4 shows how
* Figure 3 of this report.
351.1 -6
the web thickness is
determined)
The recorded dimensions for one of the
columns tested for the Comparative Study are tabulated
in Table 1.
It may be appropriate to note that function
errors such as angle,s between the flanges and the web as
shown in Fig. 5 are not measured. Such deformations~
however, are not usual for rolled steel sections.
Possible preparation errors as the angle a
between end plates, and center line deviation ~, which are
assumed to be zero in both cases (Fig. 6) also are not
measured.
2.3 Alignment of Specimen
"The alignment of the specimen will be through the
center of web and not through the real center of
gravity of the section, even if the section
shows a dissymmetry due to unusual tolerances.
The alignment will not be corrected during the
test."
The required alignment procedure is very simple
and time saving~ since the end plates can easily be welded
351.1 -7
with reference to the center of the web, and consequently
the end plates can be positioned with reference to the
.center line of the testing'machine without much difficulty.
It should be mentioned, however, that a new variable is
introduced for sections with the center of gravity not at
the center of the web. Such sections have ,been observed
in other investigations.
The column ends may not always be machined
to have parallel surfaces" thus one flange will be loaded
more than the other. It is recommended, therefore, to use at
least two strain gages at the center of the flanges or
p~eferably four at the flange tips at mid-height of the
column as shown in Fig. 7. The possible difference may
be reduced by adjusting the leveling plates at the
sensitive cross-head of the testing machine.
351.1
3. INSTRUMENTATION
-8
The instrumentation for the column tests
consists of lO~O inch graduation dial gages, 4 inch and
1 3/8 inch stroke potentiometers (with sensitivities of
4/1000 inch and 1/1000 inch res·pectively (Fig. 8) to
measure lateral deflections about both axes~ and the
angle of twists at the five levels described earlier. In
addition to the practice suggested by ECCSA, measurements
of lateral deflection and angle of twists of both ends
will be taken for the purpose of using a reference. A
possible condition for the case of mid-height deflection
is shown in Fig. 9. A layout of the instrumentation is
shown schematically in Fig. 10.
instrumentation of the column.
Figur~ 11 shows the
351.1
4. TESTING PROCEDURE
-9
The loading will be carried out as required
by ECCSA with only minor modifications:
speed of loading will not be kept constant
after the column starts yielding, and that
the rat e will depend on the type' of te s t i ng
machin~ used.
a) The required loading rate of 1.42 ksi/
min. (1 kp/sq. mm. per min.) will be
established by adjusting the valve
setting of the testing machine when the
column"is within its elastic range. The
established valve setting will be kept
fixed and will be used until the ultimate
load is reached. It is noted that the
b) The column is' .loaded continuously up to' the
dynamic ultimate load which will be
recorded' on the X- Y plotter (Fig. 12)
and the Brush multichannel oscillograph
(Fig. 13) and is indicated by the stopping
of the follower pointer of the dial
on the testing machine. All other
351.1
.-10
deflection characteristics will be
recorded automatically.
are shown in Fig. 14.
Typical plots
c) The static ultimate load will be
obtained immediately after the dynamic
ultimate load is reached. This
information is not required by ECCSA.
The value of the static load will be
obtained from the method of column
testing used at Lehigh university(3)
by closing the loading valve and taking
a reading when no further movement of
the sensitive cross-head is observed.
To confirm stabilization, a plot of the
load change and cross-head movement
versus time is shown in Fig. 15.
Stabilization usually takes place after
about 15 minutes.
d) After the static load is recorded the
test will be continued using the valve
setting established originally until a
mid-height deflection of 2 to 3 inches
is reached. Continuation of testing is
351.1 -11
not required by ECCSA. A sketch of the
complete P-Li curv·e resulting from such
a test w·il1 be similar to that shown
in Fig. 16.
351.1
5 • SUMMARY
-12
The testing of the European columns will
follow the required European Convention procedure,
described in Re_f. 1, with additional instrumentation and
recordings.
saving.
The required alignment is simple and time
Strain gages are recommended to be used for
columns with large preparation errors.
All deflection characteristics will be
plotted using automatic plotters.
The required loading rate of 1.42 ksi/min.
(1 kp/sq. mm. per min.) will be established when the
column is loaded within its elastic range. The established
valve setting will be used up to the end of the experiment.
Loading on the column will be stopped
immediately after the ultimate dynamic load has been
reached. The ultimate static load will be determined using
the Lehigh me~hod of testing after which the test will be
continued using the valve setting established originally.
351.1
6 . ACKNOWLEDGEMEN.TS
-13
This progress report presents the column
testing procedure proposed for a series of column tests
to be conducted for the European Convention of
Constructional Steelwork Association.
The investigation is being conducted at
Fritz Engineering Laboratory, Lehigh University, Bethlehem,
Pennsylvania. The European Convention, National Science
Foundation, and the Welding Research Council jointly
s.ponsor the study.
The guidance of Task Group 11 of the Column
Research Council, under the chairmanship of Lynn S. Beedle,
is gratefully acknowledged. Special thanks are due to
Duiliu Sfintesco, Director of Research, Centre Technique
Industriel de la Construction Metallique, Paris, for his
advice in the initiation of the study.
351.1 -14
7. TABLES AND FIGURES
TABLE I: CROSS SECTION DIMENSION
(;.,)
<..n
j-J
j-J
Top n-I
-2
-3
-4
Bottom U-5
Back
LeftIRi9ht
Front
Top View
Proj. No: 351
Steel Grade: A36
Shape: 12WI61
Col. No: 01
I If IILength: 13 -4 "2
Recd: P.M. t N.T:
Date: 2/9/69
Section hA hr bf bb
tfr t br cfr cbr Area
tfl fbi wf wb cfl cbl (in2)
I 1.4-64 1.440 5.789 5.80413.765 13.829 12.613 12.596 1.460 1.460 .978 .993 5.846 5.799 47.432
1.464 1.432 5.785 5.815
2 13.771 13.856 12.604- 12.594- 1.4-47 1.460 .973 .990 5.845 5.789 47.266
:3 1.4-69 1.432 5.773
5.801
13.795 13.818 12.603 12.577 1.452 1.4-71 .975 .982 5.855 5.794- 47.323
1.471 1 .. 427 5 .. 784- 5 .. 804-
4 13.780 13.832 12.618 12.596 1.451 1.439 1.034- 1 .. 006 5.800 5 .. 786 47.615
1.472 1.4-33 5.788 5.800
5 13.763 13 .. 845 12 .. 608 12 .. 598 1.455 1.436 1.025 1.006 5.795 5 .. 792 47 .. 599
Average 13 .. 775 13.836 12.609 12 .. 592 1.461 1 .. 443 0.997 0 .. 995 5.806 5 .. 798 47.450
See Fig. 3 for Notation I
j-J
en
351.1 -16
(a )
:3
(b )
2
x
4
(c )
y
Fig. 1 Instrumentation for Initial Out-of-Straightness
Measurements.
l-l
(.U
()l
l-l
0,21
0.250
(+)
0.240
AverageFront-2
Proj. No: 351
Shape: 12W"'161
Col. No: 01
Front- 1
Read and Reed: P,M. ~ N,T.
Date: 2/9/69
WEAK AXIS, INITIAL QUT-OF-STRAIGHTNESS
B
L(-)r (+)R
FBack-I Back- 2
I I I
311302812040 I
1,38 4.30
3
4
1 I~:i~ I~:i~ I
5 I -. ~. I - .......~ I
Front Back
13 • 50 120320 I
1.60 4,280
II 1
3
•
40
1
2042 I1.50 4.34
2 1
3
•
30
1
2044
I1.40 4,35
21 13.26 12 •46 I1.34 4.38
Right
Left
Fig. 2a Measurements of Initial Out-of-Straightness
(Weak Axis).
I
~
-..J
Read and Reed: RM. ~ N:r:
Date: 2/9/69
0.07
(;.)
U1
~
~
0.035
0.03
Average
0.07
0.08
Proj. No: 351
Shape: 12W-SI
Col. No: 01
STRONG AXIS, INITIAL OUT-OF-STRAIGHTNESS
LR(+)-~--c-)8
Back FrontBack Front
11.0 I 4.0 I
II I 0.98 I 4.0 I
31 11.05 I 4.05 I
4 11.10 I 4.12 I
5 1 1 •19 I 4.20 I
21 I 1.00 I 4.00 I
3 11.02 i 4.01 I
4 1 I 1.16 I 4.17 I
2 I 0.98 I 3.96 I
Fig. 2b Measurements of Initial Out-of-Straightness
(Strong Axis).
I
J---I
Q)
351.1
-19
h~
1- ... 1
Fig. 3 Required Measurements of Cross-Sectional
Dimensions.
351.1
-20
w=b-{h+h )1 2
Depth Gage Micrometer
Reference Bar
~Veling Bar
~----1111'------_ - =::~ :::- -:J
(a )
Fig. 4 Determination of Web-Thickness Using the
Depth Micrometer.
-I
351.1
Fig. 5 Possible Fabrication Error.
-21
(0) Ideal Case
Fig. 6
(b ) Non- Parallel End-Plates (c ) Deviation of Center Line
Possible Preparation Errors Not Taken Into
Consideration.
351.1
Strain Gages---+------...· ----- Strain Gages
-22
Fig. 7 Strain Gages for Preliminary Alignment.
Fig. 8 A 4-inch Potentiometer.
351.1
-23
Fig. 9 Deflection Measurements at Ends for Correct
Mid-Height Deflection.
.....
-
-
Fig. 10 Schematic Drawing of Instrumentation.
351.1 -24
Fig. 11 Instrumentation of Column.
351.1
-25
Fig. 12 The X-Y Plotter.
Fig. 13 The Brush Multichannel Oscillograph.
351.1
-26
p p
8
(b)
</>3
P
P W~ 3- -
2
P
</>
(C )
(a) Results from X- Y Plotter
(b) Lateral Deflection from a Brush Multichannel Oscillograph
(c) Torsional Ang Ie from a Brush Multichannel OsciUograph
Fig. 14 Load-Deflection Characteristics Curves.
351.1
LOAD
DEFLECTION
5 10 15 20
TIME (MINUTES)
-27
Fig. 15
p
Fig.. 16
Typical Load-Relaxation Curves.
Pou = Ultimate Dynamic Load
Psu = Ultimate Static Load
Typical Load-Deflection Curve.
351.1 -28
8. REFERENCES
1. CEACM, SOlis-Commission No .. 81
NOTE POUR L'ETABLISSEMENT D'UN PROGRAMME
D'ESSAIS DE FLAMBEMENT SUR POUTRELLES H,
Doc. CEACM - 8.1 - 6'8/1 - F, Janvier, 1968.
ECCSA, Subcommittee 8.1
NOTES FOR THE ESTABLISHMENT OF A TEST
PROGRAM ON THE BUCKLING OF H-SECTION
COLUMNS, ECCSA Doc. - 8.1 - 68/1 - F,
January, 1968.
2. Tebedge, N., Marek, P., and Tall, L.
COMPARISON OF COLUMN TESTING METHODS,
Fritz Engineering Laboratory Report No.
351.2, in pre~aration.
3. Estuar, F. R., and Ta11,L.
TESTING OF PINNED-END STEEL COLUMNS,
Test Methods for Compression Members,
ASTM STP 419, Am. Soc. Testing Mats., 1967.


Column testing procedure,  June 1969

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