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Design ReCO!llmendatilJus for Hu1ti-Story Frames·

lCAL PROPERTIES OF ASTM A36 AND A441 STEEL

by

Lee C. Lim

,Le-Uu Lu

--lYQQ S. Eeeale

FRITZ EI1\'f"f"'''ERING'll...::d \ l. I

LASORATORY UBRARY ,

This work has been carried out as part of aninvestigation sponsored by the American Iron and

'1 J ". , frStee 1 Ins t i tu te ..'Nv,.. O\ -t 'j\ I,:. 1,1\.: ;~.J. (). '~"(1 E~,~:;u: ·n-?-J (.-0 :)i·~ £.',: k: •

'"Reproduction of this in whole or in pa~t is

permitted for any purpose of the United StatesGovernment.

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",

Fritz Engineering Laboratory

Lehigh University

Bethlehem) Pennsylvania

August 1969

. _.\J

Fritz Engineering Laboratory Report No. 3L~5, \.+

TABLE ~. lr CONTENTS

1. INTRODUCTION

2. DESCRIPTION OF TENS ION SPECIMENS

3. BEHAVIOR AND DEFINITIONS

4 . . ANALYSIS OF DATA

.5. ACKNOWLEDGMENTS'

6 ~ TABLES AND FIGURES

7. REFERENCES

,

1

2

3

6

7

8

1. INTRODUCTION

This report briefly sUlrumarizes

of 165 tension specimens from plates and

l .

of the te-st data

of A36 steel and 11

specimens from plates and shapes of A441 steel. The specimens. . - ofuA· <U ~",t of- fu..,;" .G'- Jv.J~clJ'~

were previously tested by~personnel'Qf &eve~l researchAprojects some

~+ F=t;h..l,J.w"..L- M wlIieil- are st.:i.--l-l-act-i-¥e-i-R-the---l-abor-a·t-or-y-.- ov. ~~"'-'"7

The purpose 'of ~his i~O", is to obtain thQ

mechanical properties of 8 two steels loaded in

~~ may be· incorporated into the revised edition of ASCE-WRC

41 "ptastic Design in Stee 1". -----

2. t>ESCRIPTIOI~ ,-,F TENSION SPECIMENS

All tension specimens were fabricated ~~le procedure5

, ['nJ~recommended in Refs. land 2. ,~-specimen ha~ a gage length of 8

inch and width 1 1/2 inch. The'tests were performed in a 120 kip

Tinus-Olsen machine. A,detailed description of the requisite

preparation for the test and the testing procedure hav~ been given

in Ref. 2.

tM~The majority of these specimens were ~o't from the flanges

and webs of fourteen different structural shapes: 6W20) 6W25, 8v'f24 ,

8'1f35 , 8\140, 8v'f48 , lO:E2l) lOv'f29 , l2vE27, l4W30, 8B15, l2B16.5, l2B22,

and 8Il8.4. Of the 165 tension specimens, 6f A36 steel, 106 specimens

were cut from flanges, 50 from webs, and the remaining nine specimens

were cut from plates. Of the eleven A44l (50) specimens) four were

cut from webs,. two from flanges, and five from plates.

-2

3. DEFINITIONS

\/-3

For a tension specimen, a typical load-deformation curve

should exhibit three stages of behavior as shown in Fig; 1. In stage

'1, the specimen behaves elastically. There is an almost 1inearre­

1ationship beb-leen load a~d deformation until 1t"01IUi1rre~\;\J.W ~-<-~L, Dr\M"~ \{,.~ 1~}~ Q.Lv-J

~. This contaiR8d~la~i~ flow or yielG4flt i~due primarily to:

(1) misalignment of the specimen;

,(2) variation in cross-sectional characteristics; and

(3) presence of residual stresses.

The first stage is terminated ~y yielding of the whole cross-section

in certain regions of the specimen. In most cases, the stress level

" at which complete yielding first commences represents the upper

yield stress cr of the steel.uy

On de forming the spec i:men, further, it enters i.~~tage Il(D

-behalWior. This behavior i~ initially identified by a drop in stress

level to what is commonly known as lower yield stress ~~Oty before

. . 1 ' 1 h' h" -kL:t f f h d f '1t r1ses up to a new stress eve w lC 1s~codstant or urt er e or-

mation of the specimen. However if the ,deformation is terminated, the

load capacity. of the specimen will drop" The stress level at which the

specimen can sustain for no, further deformation at a strain of 0.5 per

leve1. 0yd' ,The difference betHeen' dynamic yield stress and static

ns dynamic yield stre~s

The stress leve 1 ~~'cent is known as static yield stress ~~~ a .ysr'prior to the t~rmination of deformation is K~DW~

-4

and is due essentially to strain rate

is marked by the' onset of strain-hardening.\~ P&-t1J-_ c~j'4 j

A t this stage, yielding has 5;read over the ,,,hole length o~pe'Cimen .

yield stress is uiually small

effect~3) The end of stage II

and the average strain is known as apparent strain-hardening strain.

Stage III 'describes the behavior after the full plastic flow.

Through some internal metallurgical process, steel begins to offer

small re~istance to the externally appl{ed load. Of intereit to research. ~t.

is the value of strain-hardening modulus E of steel in t~~ r~gionA~. -to .1 s t '~~_tt,"'I'tll''-~:~~~~~:''-_'"'' .

immediately afte~train-hardening. There are a few approaches usedf\

in evaluating Est and some of these are briefly reviewed below:

(1)

(2)

(3 )

E 1 is the instantaneous value as measured by a tangentst

to the curve at the apparent onset of strain-hardening

(Fig. 2(a». It represents the upper bound of the

·E values.st

E 2 is the slope of a line drawn to pass through thest

strain points of 0.003 in/in. and 0.010 in/in. beyond

the ap~arent onset of strain-hardening on the stress­

strain curve as illustrated in Fig. 2(b). The inter­

section on 'the stress-strain curve of the dynamic yield

stress level in the plastic range (stage II) with the

simplified strain-hardening line gives the reported'ji, .v

strain-hardening strain of the steel est' ~h·ts value

of the strain-hardening modulus0exhibits the least\ .1 \ \

scatter of exper:imental values. ~e-t,.\.,.,:v-t,_A~'} ·tt-..;:::. ;\-~.~'.\.oc:

Est3

is obtained by the average value in an increment

of 0.005 in/in. strain af~er the onset of strain-harderiing~4)The onset of strain-hardening is defined. in this instance

as the strain corresponding to the inter~ection o~ the •

~tress-strain curv~ of the yield stress level in the

plastic range with the. tangent to the curve in the

strain-hardening range (Fig. 2(c~.

-5

Whatever the true value of E might be) it invariably de­st

creases as the deformation increases until the tensile strength au

is reached. Thereafter) unloading begins with increasing deformation.

Fracture occurs at very large deformation) usually of the orde~ of about

25 per cent of the originally undeformed length and also at the section

where necking occurs resulting in substantial reduction in original

area.

."

-6

4. ANALYSIS OF DATA

The complete analysis of the test data of A36 steel are

given in Table 1 and those of A44l are in Table 2. There are.-ltt I'"quantities defining every specimen and these are (from left to right,

top to bottom) source, project number, specimen number, shape from

which the specimen was cut, thickness, dynamic yield stress, static

yield stress, tensile strength, percent elongation, percent of area

reduction, strain at onset of strain-hardening, strain-hardening•

o'O:hI.~V _ --modtl1:us Est1 ' Est2 ' Est3 ' ratio of static yield stress over mill

yield. stress and finally the rupture strength a .r

A summary of the analysis of all data is given in Table

3 and the histograms of the important properties of A36 steel are

shown in Figs. 3-12. No histograms for

because thecAymeer ~~availab1e·data is

A44l steel are provided

\~~~~·teo [ for the results

to be considered representative. However, the average values of the

important properties of this steel are documented in Table 3 and

are to be taken as the information available at the present time.

I~, bo;~cases, the static yield stress level is above the'-..- ..

ASTM value. The scatter "for Est values ~port8d heFe-i:.R is quite large,~-

as are the E values for A572 Grade 65 "steel reported in Ref. 4.st

The average tensile strength fo~ A36 steel is about 62 ksi, and this

is about 4 ksi above the minimum tensile stress specified by the ASTM.

The aven"ge tensile strength for" A44l- steel is about 7 ksi above the

ASTM value for ~pecimens of thickness reported hetein., "---

-7

5. ACKNOHLEDGMENTS

The work that led to this reported was conducted as part

of a general study on "Design Recommendations on Multi-Story Frames"

which is being carried out at~~~: Fritz Engin~ering Laboratory in, -

Lehigh University. This study is sponsored by the Americ~t'\Iron

and Steel Institute and the Welding Research Council. Technical

Mvice~biS study is provided by the Lehigh Project Subcommittee)

oaf ti~ Structural Steel Committee/~eWelding Research Council.

Dr. T. R. Higgins is'the Chairman of the Lehigh Project Subcommittee.

et&?(

Tl~ authors wish to thank the personnel of Fritz Laboratory

Project Nos. 230, 273, 329, 332, 334 and 346 for their ~enerotl~ a~~ \~~~ te s t da ta . .~:-;~·::~~·:·~~·;~··:~~~~~~he-aSS-is tan ce·

Wlt~ &.--it~ d'·.--.of. Mr. M. Hyland in cellec Ling-ene analyz~'--the test data.

Mrs. Sharon Balogh prepared the prawings

.tU.."'eLY. tarefoHr typed "4:frrs report.

. . ,..

and Miss Karen Philbin

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REFERENCES

ASTM1968 BOOK OF A~TM STANDARDS PART 31,Testing and Materials, Philadelphia,

Desai, ~. (~UlTENSI.ON TESf!NG PROCEDURE,Fritz En ine ingLaboratory ReportNo. 237.44p1 Lehigh University,~

Rao, N. R., Lohrman, M. and Tall, L.EFFECT OF STRAIN RATE ON THE YIELD STRESS OF STRUCTURAL STEELS,Journal of Materials, Vol. I, No. I, March 1966, AmericanSociety for Testing _and Materials, Philadelphia> Pa.

L

3.

"2.

Desai, S.MECHANICAL PROPERTIES OF ASTM A572 GRADE 65 STEEL, Fritz En­gineering Report No. 343.2, Lehigh University, September 1969.

4.