Welded reinforcement of opeining in structural steel tension members

0314

SERIAL NO. SSC-75

FINAL REPORT

(Project SR-i 19)

on

WELDED REINFORCEMENT OF OPENINIS IN

STRUCTURAL STEEL TENSION MEMBERS

by

D. VASARHELYI and R. A. HECHTMAN

University of Washington

for

SHIP STRUCTURE COMMITTEE

Convened by

The Secretary of the Treasury

LABORATORIUM VOOR

:CHEEPSCO1j0T

Member AgenciesShip Structure Committee Address Correspondence To:

Bureau of Ships, Dept. of Navy Secretary

Military Sea Transportation Service, Dept. of Navy Ship Structure Committee

C) United States Coast Guard, Treasury Dept. U. S. Coast Guard Headquarters

Maritime Administration, Dept. of Commerce Washington 25, D. C.

American Sureau of Shipping

IM -IM U as

d2

z-«s -J

ti

(1) MARCH 21, 1955

SHIP STRUCTURE COMMITTEE

March 21,

₁₉₅₅

Dear Sir:

As part of its research program related to the

Improvement of hull structures of shins, the Ship

Struc-ture Committee has sponsored _{an investigation on the}

welded reinforcement of openings in structural steel

members at the University of Washington. _{Herewith is}

a copy of the Final Report, SSC-75, of the investiga-tion, entitled "Welded Reinforcement of Openings in

Structural Steel Tension Members" by D. Vasarhelyl and

R. A. Hechtman.

Comments concerning this report are solicited

and should be addressed to the Secretary, Ship

Struc-ture Committee.

This report is being distributed to those

in-dividuals and agencies associated with and Interested

in the work of the Ship Structure Committee.

Yours sincerely,

7e7

K. K. Cowart

Rear Admiral, U. S. Coast

Guard

Chairman, Ship Structure

Comm itt e e

MESI BER AGENCIES: _{ADDRESS CORRESPONDENCE TO:}

BUREAU OP SNIPS. DEPt. OP NAVY SECRETARY

MILITARY SEA TRANSPORTATION SERVICE. DEPT. OF NAVY Suie STRUCTURE COMMITTEE

UNITED STATE. COAST GUARD. TREASURY DEPT. U. S. COAST GuARO HEADQUARTER.

MARITIc ADMINISTRATION. DEPT. OP COMMERCE WASUINOTON 2S, D. C.

FINA.L REPORT

(Project

_SR-119)

On

WELDED REINFORCEMENT OF OPENINGS IN STRUCTURAL STEEL TENSION MEMES

by

D., Vasarhelyl and R. A. Hechtman

University of Washington

under

Department of the Navy

Bureau of Ships Contract NObs-5'0238 BuShips Project No.

NS-731-O3-f-f or

SHIP STRUCTURE CONITTEE

CD

N

.i:çS

TABLE OF CONTENTS

Page

I SYITOP SI S . . .

OSOOCSO O

O C

i

II. INTRODUCTION . , . . . , . . . 2

i, Problem of the Opening in a Structural

M ember . . . 2

2. General Background of the Problem . 6

III. TESTS OF PLATES WITH OPENINGS . . . 7

Specimen Material arid Specimens . 7

Method of Testing 16

Definition of Terminology e

17

1. General Behavior During Test and Fracture

of Plates with Openings . 25

IV.

BEHAVIOR OF PLATES WITH OPENINGS IN TEL PLASTIC

RANGE 26

Theoretical Elastic Stress Distribution. 26

Plastic Stress Distribution in Plates with

Openings . . . 26

Plastic Energy Distribution in Plates with

Openings . . . 33

+. _{Effect of Testing Temperature upon the}

Plastic Stress and Energy Distribution

₃₉

5. Conditions for the Initiation of Fracture0

39

6 Effect of the Shape of the Opening upon

the Properties of the plates with Openings +2

7. Effect of the Percentage of Reinforcement

upon the Properties of the Plates with

Openings . . e .

8 Effect of the Geometric Shape of the

Reinforcement upon the Properties of the

Plates with Openings . o o o . o o e

Overall Ductility of the Plates with

Openings., ..

. . 51

Efficiency of the Plates with Openings o o 51

il.

Modes of Fracture in Plates with Openings.

V. CONCLUSIONS , . . . 60

L. Conclusions with Respect to Plastic Flow

andFracture.

..

61

2. Conclusions and Recommendations with Respect

to the Design of an Opening and its

Re-inforcement , . . . 62

VI. ACKNOWLEDGMENTS . o e o e o o o e o o o o . ₆₃

VII. REFERENCES . . e

. ... e

6

LIST OF FIGURES

No. Title

i Details of Body Plates of

36" x

1/LJt,

36"

x 1/2"

and

+8"

x 1/2" Specimens . . . o 13

2 Details of Opening and Reinforcement . . . .

3 Specimens for Room and Low Temperature Tests in

2,+OO,OO-ib0 Testing Machine

. G...G....

₁₅

Load-Average Elongation Curves for 36" x l/+" and

36"xl/2"Specimens.

. .

e...

t.

23

5 Load-Average Elongation Curves for +8" x 1/2"

Specimens G . a . e e e 2+

6 Stress-Concentration Contours in y-Direction by

Theory of Elasticity for Typical Cases . . . . 27

7 Plastic Stress-Concentration Contours in y-Direction

for Unreinforced Plates as Determined from

Mea-sured strains. . . o . . . 29

8 Plastic Stress-Concentration Contours in y-Direction

for Reinforced Plates as Determined from Measured

Strains G t t I t O G 30

9 Comparison of Elastic and Plastic

Stress-Concentra-tion in y-DirecStress-Concentra-tion on Net Cross-SecStress-Concentra-tion of

Unrein-forced Plates . O t O o o o a o e G 31

10 Comparison of Elastic and Plastic

Stress-Concentra-tion in y-DirecStress-Concentra-tion on Net Cross-SecStress-Concentra-tion of

Rein-forced Plates G G G O O o o o t . o . 32

11 Unit Strain Energy Contours at Ultimate Load for

Unrejnforced Plates as Determined from Measured

Strains , e G i e e G I G O e e o 3+

12 Unit Strain Energy Contours at Ultimate Load for

Reinforced Plates as Determined from Measured

Strains . . . e t

35

13 Contours of Equal Relative Rate of Increase of Unit

Strain Energy Absorption with Increase in Applied

Load0 Unreinforced Plates O G . 37

Title Page

Contours of Equal Relative Rate of Increase of Unit Strain Energy Absorption with Increase in

Applied Load. Reinforced Plates ₃₈

15 Plastic Stress Concentration, Maximum Unit Strain

and Maxiniuin Unit Strain Energy as Ultimate Load was Approached

16 Effect ol' Notch Acuity Upon Properties of Plates

with Openings

17 Effect of Percentage of Reinforcement upon

Proper-ties of Plates with Openings

18 Effect of Geometric Shape of Reinforcement upon

Properties of Plates with Openings 1+8

19 Efficiency with Respect to Ultimate Strength of

Plates with Openings Sustaining Shear Fracture. . 50

LIST OF TABLES

Title Page

I Mechanical Properties of Plates of Different

Thick-ness, Semikilled Steel U As Rolled 8

II Description of Specimens 10

III List of Plates Used for Fabrication of Each

Speci-men 12

IV Strength and Energy Absorption of Specimens 18

V Nature of Failure In Specimens 21

VI Elongation to Ultimate Load and Failure of Plates

with and without Openings 52

VII Efficiency of

36" x

l/1+fl Plates with Openings as

Compared with Plain Plates--Tests at Room

Tempera-ture

WELDED REINFORCEMENT OF OPENINGS IN

STRUCTURLL STEEL TENSION MEMEERS

I. SYNOPSIS

The purpose of this research has been the investigation of some of the geometric factors which affect the performance

of plates with reinforced openings, such as the shape of

open-ing, the type and amount of reinforcement, and the width and

thickness of the body plate. Some of the tests were repeated

at low temperatures to bring in the factor of cleavage frac

ture. In the course of the project, a considerable amount of

work was directed toward determining the nature of the plas-tic flow which precedes the initiation of fracture and the

conditions which precipitate fracture0 Specific

recommenda-tions based on the findings of the investigation have been

made with respect to the design of openings and their

rein-forcement0 Many of the results of the research are applicable

to welded structures In general.

The extensive test work required the use and development

of somewhat new research methods and techniques., The

applica-bility of NadaPs octahedral strain energy method the

plastic stress _{and the resistance-wire grid}

system of measurements for plastic strain studies might be

-

--

-2-II. INTRODUCTION

1. Problem of the opening in a structural member. The

introduction of an opening in a structural member under

ten-sion decreases its effectiveness by reducing its net cross

section area and producing a region of stress concentration.

The purpose of the reinforcement is the restoration to the greatest possible degree of the characteristics of the member

which existed before the opening was present. Some of the

more important factors which must be considered in the

devel-oprnent of design standards for the welded reinforcement of openings are:

Shape of the opening.

Cross section shape of the reinforcement and the notches present in welded reinforcement because of

abrupt changes in section.

Deforinability of the region around the opening as it

affects the action of the whole member as part of a

statically indeterminate structure such as a ship. Mechanical properties of the steel.

Nature of the loading.

Low-temperature cleavage fracture.

This investigation has been concerned with the first three factors which are related principally to the geometric shape

The load carrying capacity of a member containing ari

opening can be made equal to that of the intact member by

restoration of cross seàtional area through suitable

rein-forcement around the opening0 However, as this report will

show, only a fraction of the energy absorbing capacity in the

plastic range of a member is restored by such reinforcement

be-cause the reinforcement cannot improve the stress distribution sufficiently to remove the stress raising effect of the

open-Ing0 The greatest capacity to absorb energy would exist in a

member in which all elements were stressed uniformly up to the

point where failure would begin0 L plain plate with parallel

sides loaded concentrically represents such a member0 In

con-trast, an opening, because of its stress raising effect which results in a nonuniform distribution of strain, prevents the most efficient utilization of the potential capacity of the

material to deform plastIcally The best that any good design

of reinforcement for an opening can assure is the recovery of

a fraction of the energy absorbing capacity of the plate

with-out an opening0 Since the tendency towards brittle fracture

at low temperatures is closely related to the capacity of a

structural steel member to absorb energy, the degree to which good design can bring about this restoration Is very important

Another point to be considered is that the addition of common types of welded reinforcement increases the thickness

and rigidity of the member around the opening and introduces

abrupt changes in cross section0 It is quite possible to

in-crease the stress raising effect of an opening by the addition of reinforcement and thereby worsen the condition rather than

improve

It0

Thus It may be seen that the design of an opening in a structural member and the reinforcement therefor Is not a

sim-ple problem0 It Is one In which the deformation of the member,

as well as its ability to carry stress, must be considered, for only by adequacy in both of these respects can the member carry its proper share of the load as a part of the structure and

have the capacity to absorb sufficient energy to prevent f

rae-ture In the face of adverse conditions. The objective of the

design must be greater efficiency in transmitting the applied

forces through the member0 Because openings In structural

members of all types, including the details of ships, have been

the source of many

faIlures, it may be assumed in this

problem

that the only satisfactory

design

for an opening is

the one which provides the greatest ability to carry load and

absorb the

energy

of deformation.

The purpose of this project has been an investigation of welded reinforcement for openings in plate members to determine

ways in which the design of openings and their reinforcement

may be 1mproved. The factors which were varied were the body

plate thickness and width, the shape of the opening, the type

and amount of reinforcement, and the testing temperature0

Forty-one large plate specimens, each having a centrally lo-cated opening with or without reinforcement, and two plain

plates without an opening were tested Most of these tests

were made at room temperature and resulted in shear fractures0 P few specimens were tested at temperatures sufficiently low

to produce brittle cleavage fractures. Since failure occurs

subsequent to general yielding of the material, an investiga-'

tion of the plastie deformation

which

preceded fracture was

carried out to establish the manner in

which

this deformation

vas related to the geometry of the specimen and the testing

temperature

While a considerable amount of research was accomplished in the course of the project, it did not lessen the need for more work in the future because this problem is a large one and only few varIables have been investigated--and none of

these exhaustively0

Detailed descriptions of these tests in previous prog

ress reports and

papers6,

listed in the References have

been summarized in this final report0 The reader is directed

-.6-.

as additional data, the method of testing and the theoretical

methods of analysis0

2 General background g problem0 The problem cf

openings in plates has been dealt with in a number of papers,

and

soiutions(72)

are available for the elastic stress

dis-tribution for cases exactly the same as or similar to those

investigated here. These solutions assume plane stress

condi-tions, which actually are not realized or even approached in the case of many types of reinforcement, especially those with an appreciable width in the direction of the body plate

thick-ness. The assumptions made in these solutions concerning the

interaction of the reinforcing ring and the body plate are

also important0 For example, when the reinforcing ring

be-comes sufficiently rigid, it begins to act in the mariner of a

rigid inclusion in the body piate50 In this experimental

investigation no particular correlation was found between the parameters developed by the theory of elasticity and the ulti-mate strength and energy absorption to maximum load of the

plates with openings.

Theoretical anaiyses(1 based on the theory of elastic-.

ity have shown that reinforcement of an opening in a plate

cannot restore the strength to that of the prime plate0

Re-cent anaiyses(13) based on the theory of plasticity indicate

that yield strength can be reestablished with well designed

Only a small number of theoretical solutions are available for the problem of the reinforced opening9 primarily because

of its difficulty, The simplifying assumptions sometimes

nec-essary to permit a solution for this case often impair the usefulness of the solution

IlL

TESTS OF PLATES WITH OPENINGS

L Specimen material and specimens0 All specimens were

fabricated from the same heat of plain carbon semikilled steels a grade meeting ASTM Designation A 7J+9T, in the as-rolled

con-dition and called "Steel U as-Rolled" in this report0 Plate

thicknesses of l/+, 1/2,

3/+9

and 1 inch were used0 Their

mechanical properties are shown in Table L The plates used

in the fabrication of each specimen are listed in Table 1110

The transition temperature as determined from one plate of

each thickness was as follows;

Plate Tear Test Temperature for Average

Thickness Transition

₁₅

ft-lb Energy ASTM Grain

Temperature (Charpy Keyhole Test) Size

Inches OF -j40 O 120 -7-8 6 5

MECHANICAL PROPERTIES OF PLATES OF DIFFERENT THICKNESS, SEMIKILLED STEEL U AS ROLLED i 1/2 Room Temp.

35

P TABLE I

Room Temp. Tests 36,600

62,1+00

28

*

Percentage elongation in 12 inches where noted.

**

Tensile Specimen

-from normalized sample out of permanently strained specimen.

Tensile specimen broke outside of gage length. All tear test specimens of full-plate thickness.

Chemical Composition 56

0, ) 5

0.22 0.1+7 0.010 0.028 0.05 0.07 Tr. 0.066 2.11+ 3 1/2

69,70

P 3)+,900 61,200

33*

62 0.1+7 T 38,100 62,600

30*

52 0.1+5 1/2 38 P 3+,900 60,200 32 * 61 +0 T 35,200 61,500 1-52 5 1/2

52,56

P 39,900 61,900 27 L15 6** 1/2

+9,5O,51

p 38,800 59,500 27 1+3

lo

i

55,56,70,71 p 32,800 61,100 33 56 120 15 i/+ 32,3+,99 P ++,2O0 63,1+00 28 1+5

16

i/+

17,23,31

P 1++,l0O 65,300 29 51 17 l/

8,19,21

P 1+,300 65,200 29 52 18 i/+

1,7,10

P

1+5,100 65,800

29

51 -1+0

Tensile

Properties

Tear Upper Ultimate Elong. Reduction Poisson's Test Yield Strength in 8 in* of Area Ratio in Trans. Point Plastic Temp0 Range psi psi per cent per cent °F C Mn P S

Si

Ni Cr Cu Mn/c

Plate

Thick-Temp. Used Direction No. ness of for of Test, Tensile Spec.

Parallel

Test No.

or Trans-

verse to

Rolling

In.

TABLE I (Cont0)

MECHANICAL PROP1.TIES OF PLATES OF DIFFERE

THICKNESS, SEMIKILLED STEEL U AS ROLLED

Plate

Thick-Temp0 Used Direction

Tensile

Pro erties

Tear No0

ness

of

for of Test, Upper Ultimate Elong0 Reduction Poissons Test

Tensile

Spec0 Parallel Yield Strength in 8 in' of Area Ratio in Trans0

Te st

No. or Trans- verse to Point Plastic Range Tempo

In.

°F

Rolling psi psi per cent per cent OF 19 Room 9,20,22 P Ì4f,000 65,900 28 52 Temp. 20 5,1-f,l6 P -f,700

66000

28 50 21 13,15 P O0 66,000 29 50 22 1/1+ 11,12,18 P 1f3,800 65,600 29 50 2 P +5,+00 66,100 30 50 2 25 26 i/ 1/2 1/2 2, 55A

37,55

P P p ++,8Oo 65,800 291' 50 36,500 61,800 31 36,900 61,800

35*

62 T 36,500 61,100 31* 51+ 0»+6 Low Temperature Tests 1 1/2 -+6 96 P +2,300 69,900 23* 51 3 1/2 -+6 71 P ++,30O 70,900 29* 56 0.50 1/2 T

3,900

72,000

051

1/2 -20 38 P +2,500 68,500

3*

60

051

2+ l/ -20 T P 38,900 6+,iOO

t

50 55,100 73,600 28* 50

06

No.

Size of Percen- Cross-Section

orner Reinforcent tage of Area

Radius Reinf. Groes Net

In. In2

Sp.

i 23 2 3 ii 37 38A 38 - 69 2 95 96 5 6 7 8 9 10 99 31

-10-TkBIE I]: flFSCRIPTION OF S1CIMENS

x i/1" Plain Platea (No Opening)

148" x 1/2" Plates with Openings Reinforced by a Face Bar

149 Square

i-1/8

So Square

_i-1/8

Gage

Test

Length Ten,

In

F 76 76 72 78 76 0

-20

76 76 -146 714 73 75 Th 72 85 -.146 -1..6

See Fig. 1

for location of gage length and dir:iensions

of body plate, and

Fig, 2 for

details of reinforcennt.

100 9,07 9.07

100 9.1)4 9.1)4

36" x 1/14" Plates with Unreinforced Openings

36

Circular

O

9.21

6.92 36

Square 1/32 o

9.18

6.82 36

Square

i-i/8

O 9.15

6.87

36

36" x 1/2"

Plates with Unrein.forced Openings

Square

i-1/8

0 18.00 13,50 36 Square

1-1/8

o

18.00 1.3.50 36 Square

i-]./8

o

18.00

3.3,50 36

Circular

o

18.00

13.50 36 Square _1/32 0

18.00

13.50 36 Square 1/32 O 18.00

13.50

36

3I1

_{p]g with Openings Reinforced by a Face Bar}

Circular

2 x 1/14 140 9.1]. 7.76 36 Circular i X 3,/14 17 9.15 7.25 36 Square 1/14 2 z 3,/14 140 9,13. 7.72 36 Square

3/16

3. z 1/14 3.6 9.02 7.13 36 Square

i-1/8

2 z

1/14 140 9.13 7.714 36 Square

_i-1/8

i

X 1/14 16 9.35 7.22 36 Square

_i-1/8

2 x 1/14 140

900

7.714 36 Square

i-3,/8

1 x

16 9.00 7.22 36

2 x 312

33 21432 2 1.214 148

2 x 3,/2

33 214.32 21.2h 148 70

-20

-11-TABIL

II

EsCFtIPTIoN OF SPE.CINS (Conta)

0penin

Size of

Percen- Cross-Section

Gage

Test

No0 Shape

Corrr

Reinforcement

tage of

Area length Temp.

Radius

_Reinf.

Gross Net

In

F

36" x 1/14" Plates with Openings Reinforced by a Single Doubler Plate

148" x 1/2" Plate8 with Openings keiriforced by a Single oub1er Plate

51 Square

i-1/8

18 x 18 x 1/2

96 214.17 214.01 148 714

52 Square

l-1/8

18 x 18 x 1/2

_{96 214,00 214.01 148 -146}

36" x 1/14" Plates with Openings Reinforced by an In.9ert Plath

17

Circiir

2-3/14D x 1/2 39

9u

7,7]. 36 714 18

Circular

l0-1/2D z 1

50 _9.13 8.08 36 75 19 Square _1/32

lSD x 1/2

33 9.014 7.55 36 76 20 Square _{1/32 12_3/)4r12-3/14ir/2 39 9.13 7.72} 36 72 21 Square

i-1/8

]5D z 1/2

62 9.02

8.17

36 77 314 Square

l-1/8

15D x 1/2 62

9.00

8.17 36 -.146

22 square

_i-118

12-3/14x12-3/Lixl/2 39 9.0 7.66 36 73

148" z 1/V' Plates with Openings Reinforced by ari Insert Plate

5 Square

i-1/8

lSD x 1/2

66 23 .63 22 .09 148 70

55A Square

1-1/8

15D x 1/2 67 23.58 22 .10 148 69

56 Square

1-1/8

15D x 1/2 66 214 .00 22 .09 148 -146

70 Square

1-1/8

12-3/14x12-3/14x1 39 214.00 21.38 148 76

71 Square

i-1/8

_{12-3/14x12-3/14x1 39 214.00 21.38} 148 -146

36" x 1/iL" Plate with Opening Reinforced by

a Combination

of Face Bar and Insert Plate

85 Square

1-1/8

78 9.00

85o

36 76

ii

Circular

18"D x 1/14 102

9.11

9.13 36 75 12

Circular

_{13'"D x 1/14 50}

_9ilj.

₇₉₉

_{36 73} 13 Square 1/32 18 x 18 x 1/14 1014 9.17

9.21

36 76 Th Square _]J32

_l3

x l3

_{x i/IL 51} 9.114 8.02 36 71 15 Square

1-1/8

18 x 18 x i/IL

103 9.13 9.16 36 76 32 Square

i-1/8

18 x 18 x 1/14 103

9,00

9,16 36 -146 16 Square

l-1/8

13

x l3

x 1/14 52 _{9.13 8.01 36 73}

-12--TABLE III

LIST OF PLATES USED FOR FABRICATION OF EACH SPECIN

Specimen Plate Tmber Used for

Thmber Body Plate* Reinforcement

1 18 2+ 3 2+ 23 --5 20 20 6 23 23 7 18 18 8 17 17 9 19 19 10 18 18 11 22 21 12 22 21 13 21 21 1+ 20 21 15 21 21 16 20 21 17 16 ₂₅ 18 22 10 19 17 25 20 19 25 21 17 25 22 19 ₂₅ -'23 16 --31 16 ₂₁ 32 15 21 3)+ 15 26 37 26 38A 38 Ef₉ 50 51 52 55 55A 56 69 70 71 85

95

96 99 6 6 ₂₅ 6 ₂₅ 5 26 26 10 25 10 5 10 3 --3 10 1

15

21

*Mechanical properties of plates are given in Table I. Sketches of specimens are in Figs. 1 and 2.

48" WIRE SPACING ON BOTH FACES

[ti

W: 36" O - LOCATION OF THERMOCOUPLES N a WI 52" SLIDE WIRE SPACING H FACES SAME

ii 3i"

1134"

h

?31:

)Itt

LJ

48" FIG. I.

DETAILS OF BODY PLATES OF

36" X /4, 36'X /2" AND 48" X 1/2" SPECIMENS w

L

I o p-Y A $ o p-SLIDE _SAME N R 36 w w

II 2 69 I2 !4 - SI-95, 96 r///////,'J 37, 3 8A 38 k'//////. '3 55. 55A, 56 5, 32 21, 34 'It..--[-I. 22 70,7! FIG. 2. DETAILS OP OPENING AND AFINP0CEMEN1

I

8 ft-

1'9 i-I/v. 9, 99 IO, 31 49, 50 l/t

20mt

FIG.

3.

-16-The details of the specimens, including the size of the body plate, the shape of opening, and the type of

reinforce-ment are given in

Figs0

i and 2 and Table 110 Three sizes of

body plates were used: 36-in0 by 1/1+-in., 36-in0 by 1/2-in.,

and #8-in. by 1/2-in. The edges of the specimens were flame

cut and ground smooth0 The reinforcement was welded in

ac-cordance with U. S0 Naval General Specifications, Appendix ₅

(Navships )+51). The electrodes met AWS Specification E-6010.

No specimen was tested until at least seven days after the

welding was completed0

2. Method of testing. AU specimens were loaded as shown

in Fig. 3 in a 2,1i-00,000-lb. universal hydraulic testing

rna-chine with their longitudinal centerline parallel to the

roll-ing direction of the plate. Three types of gaging were used

on all specimens to make the following measurements: the over

al]. elongation by slide-wire resistance gages on a gage length

equal to the width of the plate and straddling the area of the opening9 the strains in the elastic range on one quadrant of the plate by SRf strain gages, and the temperature of the

plates by thermocouples. The deformation In the plastic range

of an area containing the opening was intensively studied in

the case of seven The elongations were measured

by a slide-wire gage grid system specially devised for those

-17-enclosed in an insulated bag through which chilled air was circulated to bring the temperature of the plate to as low as

as shown in

Fig0

3

30 Definitior terminoloy0 Some terms used in this

report are defined below0 The elongations measured over a

gage length equal to the plate width at five points across

the width as shown in

Fig0

i vere averaged to give the

aver-age elongation0 The term 'ioad at general yielding of the

specimens" refers to the load at the point where a definite elbow appeared in the plot of the total load on the plate

against the average elongation The area under this curve,

or any portion of it, represented the energy absorption of

the specimen up to the point under consideration0 _Two

val-ues of the energy absorption have been reported, the energy

to ultimate load and the energy to failure0

The ultimate load (the maximum load sustained _{by the}

specimen) was divided by the original net cross section area

of the specimen to give the maximum average net stress or

Ui-tirnate strength of the plates The three shapes of opening

are referred to as circular, square with rounded corners, and

square; and the plates without openings as plain plates0

The unreinforced plates with openings were considered as

having zero percentage of reinforcement, _{For reinforced plates}

There the energy to

ultimate load is slightly

larger than the energy to failure, the difference

represents the

elastic recoil of the specimen during fracture0

STRENGTH AND ENERGY

ABSORPTION OF SPECIMENS Spec,. No Opening Percent Heinf, In Test Tempe F General Yielding Ultimate Strength

Enorr Absorption in 1000's in-lb to

Shape Corner Radius Load Average Stress Load lbs Average Stress Gross Net lbs psi psi Gross psi Net psi Ultimate Load Failure Plain Plates (3611 x

i

loo

8]. 380,000 142,000 142,000

585,500 65,390 6,39O

14,018

6,276

23 100 76 390,000 Ii3,300 143,300 583,000 614,780 614,780 14,062 6,779

Plates

with Unreinforced enings (36" x 1/14") 2

Circular

O 76 291,500 32,1400 143,200 14)40,000 148,900 65,150 1,136 1,16)4 3 Square 1/32 Q 72 292,000 32,500 143,250 357,500 39,800 52,900 338 538 14 Square

i-1/8

o 78 292,000 32,500 143,250 1421,000 146,700 62,350 117 899

Plates with llnreinforced Ope nings

(36" x 3/2")

37 Square i-1/8 0 76 14O,0oO 25,000 33,300

800,000 W,5oO 59,300

1,700 2,179 38A Square

1-3/8

o o oo,000 27,800 37,000 898,000 149,900 66,500 2,890 3,1470 38 Square

1-1/8

0 -20

500,000 27,800 37,000

9)5,000 50,800 67,700

2,778

2,778 69 Circular O 76 500,000 27,800 37,000 8)45,000 147,000 62,500 1,739 2,533 95 Square 1/a2 0 76 1477,500 26,500 35,1400 710,000 39,1400 52,600 1,100 1,597 96 Square 1/32 o 4i.6 550,000 30,600 140,700 6148,000 36,000 148,000 1486 1486

Plates with Openings Reinforced by a

5 Circular 140 714 321.,O00 36,000 142,500 517,000 57,1400 67,800 1,277 1,1420 6

Circular

17 73 3214,000

36,000 145,5

1457,000 50,800 614,200 725 910 7 Square 140 75 322,000 35,800 142,230 397,000 1414,100 52,070 1422 750 8 Square 3/3.6 16 714 288,000 32,000 140,1420 391,500 143,500 514,950 14147 780 9 Square

1-1/8

140 72 319,000 35,500 141,8140 1451,000 0,100 59,150 7)47 1,063

Spec. No0

OpenI

Percent

T08t

General Yielding

Shape

orrr Reinf,

mp. Load

Avera;e Stress

Radius Gross TABLE IV (Cont.)

STBENGTI-I AND ENERGY ABSORPTION OF SPECIMENS

Ultimate Strength

Load

Average Sres

Groes

Net

Energy Absorption

in 1000'ø in-lb to

Ultimate Fáilure

Load

Pnlate6 with Openin,e Reinforced by

a Face Bar

(36" x i,/14") (cant0) 10 Square

l-1/8

16 75 313,000 143, 930 148,930 t67,000 5].,900 655140 1,2114 1,5014 99 Square

1-1/8

LLO -146 3140,000 37,800 14)4,000 507,000 56,1400 65,500 1,062 1,019 31 Square 1-1/8 16 -146 3614,000 140,1400 o, 1400 527,000 58,600 73,000 1,857 1,880

Plates with Openings Reinforced

by a Face Bar

(148" X iJ2") 149 Square 1-1,'8 33 70 7140,000 30,1400 314,800 1,255,000 51,600 59,000 3,510 14,710 5C Square i-ij8 33 -20 880,000 36,600 141,500 1,1410,000 58,800 66,800 5,892 5,610

Plates with 0peninj

Reinforced by a Single

oub1er Plate

(36" x 1/14") 11 Circular 102 75 360,000 140,050 140,050 555,000 61,670 61,670 1,358 1,569 12 C1rculzir 50 73 331,500 36,900 142,100 1488,000 514,200 62,000 771 983 13 Square 1/32 1014 76 337,500 37,500 37,500 1451,500 50,170 50,170 387 728 114 Square 1/32 51 71 300,000 33,300 38,100 1406,000 145,100 51,600 328 621 15 Square 1-1/8 103 76 362,000 140,220 140,220 522,500

58,060 58,060

729 1,099 32 Square 1-1/8 103 -146 t14l,O0O 149,000 148,100 5l8,0o0 60,900 59,800 8914 1, 1014 16 Square

1-1/8

52 73 300,000 33,300 38,100 1457,000 514,100 61,900 779 1,1514

Plates with Openin?6 Reinforced by a Single Doubler Plate

(148" x 51 Square 1-1/8 96 714 770,000 31,900 32,100 1,385,900 57,1400 57,700 14,730 5,360 2 Square i-1/8 96 -146 950,000 9,6OO 39,600 1,1460,000 60,800 60,800 14,303 14,187

in

F

lbs

p81 psi lbs

psi

psi

Spec.

No. Opening Shape Corner Uadiva

in.

17

Circular

39 18

Circular

SO 19 Square 1/32 33 20 Square 1/32 39 2]. Square

1-1/8

62 3Ii Square

i-1/8

62 22 Square 1-1/8 39 55 Square

1-1/8

66 5A

square

1-1/8

67 56 Square

i-1/8

66 70 Square

1-1/8

39 7]. Square

i-]J8

39

TABLE IV (Cont.)

STRENGTH AN!) ENERGY ABSOR1'II0N OF SPECIMENS

Percent Test

General Yielding

Heini.

Temp.

Load

Average Stress Groes

Net F Ths psi psi Ultiimte Streneth Load Average treaa Groas Net lbs psi psi Platea with

0peniwa

Reinforced by an Insert Plate

(36" x 1/1)

Energy Absorption

in 1000's

in-lb t 'Iii tima ta

Failure

Load 7h )22,000 35,800 141,880

1495,000 %,000 614,390

1,196 1,361 75 3140,000 37,800 143,200 521,500 58,000 66,300 1,268 1,1400 76 301,000 33,1400 39,660 362,000 140,200 1,7.690 229 518 72

320,000 35,600

1,1,620 1,27,000 1,7,500 55,5140 5145 836 77 300,000

33,300 36,360

1478,000 53,100 57,9140

1,1$

l,1481i

-376,000 14i,8oc 146,000 551,500

61.300 67.Oo

1,652 1,5142 73

319,000 35,500

141,1490 1437,000 1.43,600 56,81.10 600 9714

Plates with Openings Reinforced by an Insert

Plate

(148" x 1/2") 70

800,000 33,800 36,200 1,27S,000

514,000 57,700 69 800,000 33,900 36,200

1,288,000

514,800 58,300 -146 900,000

38,200 1O,8O0

1,360,000 S7,600

61,500 76

800,000 33,300 37,600 1,276,000

53,100 59,700 -146

800,000 33,300 37,600

1,176,000 148,800 55,000 Lt 2140 1,, 082 3,14214 3,362 2,0814 14,660 L,,328 3,220 3,699 0814

Plate with Opening

Reinforced

br a Combination of Face Bar and Insert Plate

(36" x 1/14") 85 Square

i-1/8

78 76 295,000 32,780 314,710 1493,000 514,780 58,000 1,14142 1,7L7

3pec. Shape of Per Cent Test Fracture Per Cent Location of

No, Opening Reinf. Temp. Cleavage Shear Unbroken Final Fracture

Plain Plate (6" x 1/1+") i loo 81 0 ₇₆ 23 100 76 0 70 2 3 Circular O Circular O Square R.C. O -21-TABLE V

NATURE OF _{FAILURE IN} SPECIMENS

21

30

Plates with Unreinforced Opening (6" x 1/1+")

Plates with tfnreinforced Opening (6" x 1/2")

76 0 80 20 Through Opening

72 0 60 1+0 Through Opening

(Corner)

78 0 ₅₉ +i Through Opening

37

Square B.C. O 76 0 51+ 1+6 Through Opening

38A Square B.C. O 0 87 13 0 Through Opening

38 Square R.C. O -20 91 ₉ 0 Through Opening

69 Circular O ₇₆ 0 67 ₃₃ Through Opening

95' Square O ₇₆ 0 ₈₉ 11 Through Opening

96 Square O -1+6 100 O O Through Opening

Plates with Openings Reinforced by a Face Bar (6' x 1/1+")

5' Circular 1+0 71+ 0 58 1+2 Through Opening

6 Circular 17 ₇₃ 0 63

₃₇

_{Through Opening}

7 Square 1+0 ₇₅ 0 ₅₉ 1+1 _{Weld to Rein.}

8 Square 16 71 0 62 38 Through Opening

9 Square B.C. 1+0 _{72 0} 1+1+ _{56 Weld to Rein.}

lo Square R00. 16

₇₅

0 ₆₉ 31 Through Opening

99 Square R,C. 1+0 -16 97 ₃ 0 Through Opening

31 Square R.0 16 -1+6 _{75' 25' 0 Through Openîng}

Plates with Ooenin s Reinforced b Face Bar X 1 2")

1+9

_{Square R.C.}

33 70 0 _{77 23 Weld to Rein0}

55 Square R.C. 66 55A Square R.C. 67 56 Square R.C. 66 70 Square R.C.

₃₉

71 Square R.C. 39 -22-TABLE V (Cont.)

NATURE 0F FAILURE IN SPECIMENS

Plates with Openings Reinforced by an Insert Plate (1+8" x

1/2")

70 ₅₇ 28 l

69 0 ₇₉ 21 Through

Opening

-1+6

:ioo

O O

Through Body

Plate

76 1 50 1+9 Through Opening

-1±6 100 0 0 Through Opening

Plate with Opening Reinforced by a Combination of Face Bar

and Insert Plate (6" x 1/1±")

85 Square B.C. 78 76 O 67 33 Weld t Body

Plate

*Initial failure in pulling plates. Spec. No. 51 reloaded after

3 days, Spec. No. 52 after 9 days, and Spec. No. ₅₅ after iO days.

51

52

Square R.C. 96 71+ 0 81

Square R. C.

96 -1+6 100 0

Plates with 0oenin s Reinforced by an Insert Plate

19 0 ('6"

Weld to Reinf.*

Through Body

Plate*

x 1/1+")

17 Circular

₃₉

71+ _{O 72 28 Through Opening}

18 Circular 50

₇₅

0 61

₃₉

Through Opening

19

Square

33 76 0 51+ 1+6

Through Opening

(Corner)

20 Square 39 72 0 62 38 Through Opening

(Corner)

21 Square R.C. 62 77 0 66 31± _{Through Opening}

22 Square R.C.

₃₉

₇₃ O

67

₃₃ Weld to fleinf.

31+ Square R.C. 62 _)+7 96 1+ 00 Through Opening

Spec. No. Shape of Opening Per Cent Reinf. Test Temp.

Fracture Per Cent Location of

Final Fracture

Cleavage Shear Unbroken

Plates with Openings Reinforced by a Single Doubler Plate (6" x

11 Circular 102 ₇₅ 0 58 1+2 Through Opening

12 Circular 50 ₇₃ 0 62 38 Through Opening

13 Square 101+ _{76 0} 58 +2 Through Opening

(Corner)

11 Square 51 71 0 50 50

Through Opening

(Corner)

15 Square PL.C. 103 76 0 65

35

Through Opening

32 Square R.C. 103 -1+6 63 22 15 Through Opening

16 Square R.C. 52 ₇₃ 0 ₅₅ 1+5

Through Opening

g

AVERAGE ELONGATION ON 3e IN. GAGE LENGTH - INCHES 36"x 1/4" PLATE WITHOUT OPENINGS

-.23-2 3

AVERAGE ELONGATION ON 36 IN GAGE LENGTHINCHES

36" G 1/4" UNREINFORCED PLATE

36" /4" 6, REINFORCED BY FACE BAR 36" I/4 ,, REINFORCED BY INSERT

FIG. 4. LOAD-AVERAGE ELONGATION CURVES FOR 36"x 1/4" AND 36" H /2" SPECIMENS.

00 00 NO, I SPEGNO2R SPEC. 6__A_4 2 A 6 R IO IO 14 O-0--o SPEC. 302 NO.3 1104 SPEC. A-A---_O SPEC.

r

_{: ::}

i'

A A SPEC.NO.13

If A'-'A SPEC. NO.14

EE :.

H

000 400 200

11

I.

A O O H SPEC NG SPEILHO.3e SPEC.NO. SPEC.NG. A8 GSPEC,N0.S5 6 ASPPC.N0.SN 37

ÍIII

36A 69 -. H H H 0-o V 9$ b 76' S

-11

I1iU

liMlit

:

SPEC403I H00 SPG9G

a.

G-O.-'-O

ft

__EOJ2

SPECRO17 ? GAENAGE ELONGATION Old 3H IN, GAGE LENGTH INCHES

AVERAGE ELONGATION ON 36 IN. GAGE LENGTH INCHES 36"x 1/2" UNREINFORCED PLATE 36" /4" 6,, REINFORCED BY SINGLE DOUBLER 6,

2 3 2 3

AVERAGE ELONGATION 01136 IN, GAGE LENGTH INCHES AVERAGE ELONGATION ON 3H IN. GAGE LENGTH INdIES

ROO AGO 300 000 lOO O 600 500 400 200 lOO 600 500 400 6300 200 loo O 60G 300 400 300 20G lOO

600 _I400 200 000 000 600 400 200 600 400 200 loo BO ₆₀₀ 40 20 O o S

i

O FIG. 5.

LOADAVERAGE ELONGATION CURVE8

FOft 49" X I/2 SPECIMENS.

_____.__ï_

-Ji

'S.S

IV_

I_

i, ".0. SPEC. NO.55 74 SPEC. NO.65 -4N I 75 -0-" SPEC. *5PC6. O5FEG 50.55 RO.550 6036 70"F

I

5O.F ."RF o 4f l/2 & REI'ORCEO BY FACE BAR 48" i/f L REINFORCED BY SINGLE DOUBLER PLATE o 2 3 4 48 /2" A REINFORCED BY ROUND INSERT 2 3 4 5 6 2 B 4 6 2 3 4 48" 1/2 5 REINFORCED BY SQUARE INSERT 6 60 ₄₀₀ 200 lOO BO 600 400 200 o 1600 400 1200 000 800 600 400 200

-25-per cent between the additional net cross section area added to the unreinforced specimen and the cross section area of

the material removed from the body plate by the opening0 Thus

a reinforced plate with a net cross section area equal to the area of the plain plate would have a percentage of

reinforce-ment of 100 per cent0

The percentage of' cleavage or shear in the fracture was

taken as the ratio in per cent of the cleavage or shear por-tion of the actual cross secpor-tion, including any unbroken part,

of the specimen along the fracture line.

. General behavior during test and fracture of plates

with openings0 A detailed description of the results of' these

tests has already been presented in the previous progress

re-ports"60 Accordingly, only a summary of the data is

in-eluded here

A comparison of the applied load and the average elonga-tion on a gage length equal to the width of the plate is shown

for all tests in Figs. - and 5. A summary of the more impar-.

tant data and a description of the failure are given in Tables

IV to VII, inclusive, and

Figs0

7--l8 The results of the

tests and their significance will be discussed in the

subse-quent sections of this report.

-26-IV. BEHAVIOR IN THE PLASTIC RANGE OF PLATES WITH OPENINGS

Theoretical elastic stress distribution. For purposes

of comparison with the plastic stress distribution determined for certain specimens, the elastic stress distribution was computed by theory wherever a solution was available for a case similar to or the same as that of the specimens being

tested0 The results are presented in Fig. 6 in the form of

elastic stress concentration contours0 This figure indicates

three important facts: first, that for those cases where the ratio of the width of the plate to the diameter or width of the opening is greater than about four, the solution for a

plate of infinite width gives satisfactory results; second, for all practical purposes the shape of the opening affects the elastic stress pattern only in the vicinity of the open-ing; and thirds the elastic stress concentration factor for a circular opening is 3.00 and for a square opening with a

cor-ner radius one-eighth the width of the opening 3.09. These

facts are in accord with St. Venant's principle.

In the plates with a single doubler plate reinforcement the SR-1+ readings indicated a second peak of stress

concentra-tion in the body plate adjacent to the outer edge of the

dou-bler. The theoretical stress distribution for an insert plate

in Fig. 6 shows such a point.

Plastic stress distribution in plates with opening. The stresses in the plastic range of the steel were computed from the measured strains in the specimen by the tangent

INrINITE WIDTH O.95

:::pk%

p

3.1OMAX. O O I 6OMAX. IN PLATE h*INITE WiDTH. FACC BAR FIG. . STRESS-COqICENTRATIOH CONTOURS * p-DIRECTION BY THEORY O ELASTICITY

-28-modulus method of stress anaiysis(26) developed by this

in-vestigation. The plastic stress concentration contours and

distributions in Figs0 7 to 10, inclusive, give the ratio of

the true stress at any point in the y-direction (the direction of the applied tension) to the uniform true stress on the

gross area of the specimen in a region remote from the

open-ing.

The transition from the elastic to the plastic stress state brought about no significant change in the general na ture of the stress pattern but only in the relative values of

the stresses themselves, Js the load on the specimen was in"

creased to the maximum, or ultimate load, there was a tendency for the plastic stresses across the section to approach

uni-f ormity, that is, uni-for the specimen to develop a more euni-funi-ficient

manner of carrying the stresses than existed in the elastic

range. This trend towards a leveling out of high stress

con-centrations and consequently more nearly uniform stress dis-tribution was most pronounced in the specimens with the lower

elastic stress concentration factors. These tests showed why

it is desirable in the design of openings and their

reinforce-ment to remove causes of stress concentration to the greatest

possible degreeG When a severe stress raiser was present, the

plastic stress gradients around the opening were steeper. Good

SPEC. NO. 31. 76F

-29-.

SPEC NO 69 76F.

SPEC. NO. 38. -80F.

SC. NO. 95. 16 F SPEC. NO. 96 -46 .

-30-SPEC. NO. 70. 76 E.

SPEC. NO. 71. -46F.

FG 8. PLASTIC STRESS-CONCENTRATION CONTOURS N y DIRECTION FOR REINORCED PLATES S DETERMINED FROM MEASURED STRAINS.

SPEC. NO. 31 76F

SPEC. NO, 95. 76 F,

-31--.AI_ FOR LOAD OF 575 XPS 0--- FOR LOAD OF7IOIQPS

C MA XIS 1*4)

_S._ tLASTIC OWl STRAIN (S 8-4)

SPEC. NO. 69. 76 F

RAClURE

- Rl CLASTIC INEORI.

F08 LOAS OF 650 XIP

FOR LOAO OF 845 KIPS,

MAXIMUM)

SPEC. NO. 38. -2O F,

FR AC T LW

SPEC. NO. 96. -46F.

too

-32-LOO

.00 YRACTURC

-e--Ç LOAD OF 15001RO

jJ 03K LOAD OF 1276 KIRS

(MAX MUM)

SPEC. NO.7 46F

FIG. IO. COMPARISON OF ELASTIC AND PLASTIC STRESSCONCENTRATION IN y DIRECTION ON

-33-efficient plastic stress distribution and thereby a higher

ultimate strength and energy absorption0

3.

Plastic energy distribution in plates with openings0

The unit strain energy distribution in the vicinity of the opening was computed from the measured strains in the

speci-mens by the octahedral theory of A. Nadai. Contour maps

showing the unit energy distribution in the plastic range ap-pear in Figs0 U and 12.

It is interesting to point out that the contour line for the average unit energy absorption (the total energy absorp-tion in the gaged area divided by the volume of the specimen within that area) fell in almost the same location in each plate as the contour line for unit stress concentration for

both the elastic and the plastic stress states0 Also, the

higher values of the unit energy absorption appeared in the

same area of the specimen where the higher values of the elas-tic and plaselas-tic stresses occurred.

These few tests appear to indicate that one principal function of the reinforcement is that of reducing the spread between the maximum and the minimum values of the unit energy

absorption. In respect to the unreinforced plates, Fig. 11

shows how decreasing the severity of the notch reduced the concentration of high values around the corner of the open-ing and caused a more nearly uniform distribution of the en

SPEC. NO. 3. 76 F.

SPEC. NO. 69. 76 F

SPEC. NO. 38. -2OF.

SPEC. NO. 95. 76F. SPEC. NO. 96. -46F.

-35-SPEC. NO. 70. 76F

SPEC. NO. 71. -46F.

HG. 2. UNIT STRA ENERGY COHTJRS AT ULTIMATE LOAD FOR REINFORCED PLATES

-36-radii in design was indicated. Similar statements could also

be made concerning the plastic stress distributions shown In

Figs. 7--10.

It was foundt26) that the unit plastic energy absorption

at any given point in the specimen Increased in accordance

with the empirical equation,

0A+BP,

where e Is the base of Naperlan logarithms, A and B were

nu-merical quantities, and P the applied load. The small

quan-tity A was found to remain almost constant. The significant

variable was B, the slope of the semi-logarithmic curve

relat-Ing u and P. From semi-logarithmic plots of u against P for

each of the many points of the grid system on the surface of

the specimen, the values of B were obtained. A similar

semi-logarithmic plot with respect to the average unit energy ab-sorption UAV for the entire gaged area gave the average value

of B, or BA . The ratio has been called the relative rate

V

Av

of increase of the unit energy absorption. Maps showing the

contours of equal values of this ratio appear in Figs. 13 and

11±. The fact that the experimental data were amenable to such

a rationalization indicated that the energy absorption devel-oped In a systematic and logical manner at all points of the

/

SPEC. NO 95. 76 F

-37-.

SPEC. NO 69 76F

FIG. 13. Coritors of Equal Relative Rate of Increase of

Unit Strain Energy Absorption with Increase in

Applied Load. Ifnreinforced Plates.

-38-SPEC NO. 70. 76P

SPEC. NO. TI. - 46F

FL3. lL. Contours of Equal Relative Rate of Increase of

Unit

Strain

Energy Absorption with Increase in

-39-1+ _{Effect of testing temperature upon the plastic stress}

and energy distribution. The plastic stress distributions in

Figs0 7 and 8 and the plastic unit energy distributions in

Figs 11 and 12 were examined by the application of

statisti-cal methods for the purpose of determining whether they _could

be correlated with the mode of fracture in any way0 In each

of these plots are shown the results for duplicate _specimens

tested at two different temperatures--one selected to produce

shear fractures and the other predominately cleavage fracture,

Specs No0 37 and

38,

and ₉₅ and 96, and 70 and 7l It was

found that in the plates with the latter mode of fracture _the

higher plastic stress and unit energy values _{were concentrated}

more closely around the opening than in the plates with the

former mode of fracture; that is, the plastic stress _and

en-ergy gradients were steeper0 _{Cleavage fracture was}

accompa-nied by a less efficient stress and energy distribution than

shear fracture0 _{Moreover, this effect of testing temperature}

on the behavior of two Identical specimens suggests that _tests

resulting in shear fractures cannot be used to _{give reliable}

predictions of the probable results of low-temperature _tests

which produce cleavage fracture0

5 Conditions for the initiation of fracture0 _{In these}

tests It was observed that the fracture was initiated at the maximum, or ultimate load, whether it was of the shear or

the true stress, unit energy, and unit strain were observed.

The highest elastic stress and first Luders line were also

found in this region0

The experimental data were examined for information which might describe the conditions under which fracture was

initi-ated, such as the maximum true stress, the maximum unit energy

absorption, and the maximum unit strain. It should be pointed

out with respect to these maxima that the use of a grid system of l-in, gage lengths may have resulted in small errors in de-termining the exact location or the true value of the absolute maximum, which always occurred near the boundary of the

open-ing0

A considerable variation of the maximum true stress was observed in the seven specimens, the range being from 68.5 to

lO5O

ksi0

However, when the maximum plastic stress

concen-tration factor was computed, the relations shown in the upper

two diagrams of Fig0 15 were found. The stress concentration

factor was always maximum in the elastic range, decreased as the plastic stress or load level increased, and approached a constant and also a minimum value as the ultimate strength of

the plate was reached0 This observation suggests that perhaps

the low energy cleavage fracture of some welded members, which is often accompanied by low ultimate strength, may result in part because the amount of plastic flow which has occurred is not large enough to bring about a sufficient reduction in the

o D C Q C o ()I Q, Q, 0) _u) 0 . o. C 0. D E >. _{w 0.2 C D} .:: o., (I) o tizo 6 D E 12 C _w E 4 'C

PER GENT OF ULTIMATE LOAD

o. C .0.3 _{* o} E X D o C20 _{.E 6} E12 > D' C ILl

c4

FIG. 15.

PLASTIC STRESS CONCENTRATION, MAXIMUM UNIT STRAIN AND MAXIMUM UNIT STRAIN ENERGY AS ULTIMATE LOAD WAS APPROACHED.

o..___ SPEC.

EÏE0

°37

u

A

a Q

1K

_-.

u

-IA SPEC.

Jc

95 o 9' 1. SPEC. 0. 96 -46F.

¡

A

A

NO.

r

90 loo C o o.' loo 50 60 70 80 90

-+2-The maximum unit nominal strains observed in the specimens are plotted in the middle diagrams of Fig. 15, and the maximum

unit energy absorption in the lower diagrams.

While the plots in Fig. 15 show that certain of the maxi-mum properties of the specimens followed a consistent relation,

they also indicated that no single numerical value of any one of these properties could be used to predict the imminence of

fracture. while the geometry of the specimen was an important

factor in determining failure, other factors, such as the test-ing temperature, the mechanical properties of the steel before and after permanent deformation, and undoubtedly the many small stress raisers produced during the fabrication and welding of

the specimens were also significant. The common theories of

failure are related only to the geometry of the specimen.

6 Effect of the shape of the opening upon the properties

of the plates with openings0 In these tests it was found that

the most important factor affecting the properties of the plates with openings was the notch severity of the opening, which

de-pends primarily upon the notch radius. The notch acuity was

R0

expressed in terms of the ratio, a-, where R0 Is the

half-N

width of the opening and RN the radius of the notch0 The

rela-tions of various properties of these plates to this ratio are

shown In Fig. l6 All the specimens in these plots sustained

O 40 -J w 50 30 2000 a-z 0o 1200 o Z o b-& 600 a, 3-'3 400 Z w _L3_ 2 4 6 8 IO 20 40 60 80100 144

RATIO OF HALF-WIDTH OF OPENING TO NOTCH RADIUS R./R1.

'3 3 '9 70 50 45 5.0 u, Li T (2 Z 4.0 '3 o -J 3.0 I-O 2.0 Z o I-.0 o -J w 0 0 2 4 6 8 IO 20 40 60 80100 44 ₂ 4 6 8 IO 20 40 60 80100 144

RATIO OF HALF-WIDTH OF OPENING TO NOTCH RADIUS RO/Ru _{RATIO 0F HALF-WIDTH OF OPENING TO NOTCH RADIUS R/R,1}

FIG 16. EFFECT OF NOTCH ACUITY UPON PROPERTIES OF PLATES WITH OPENINGS.

2 4 6 8 0 20 40 6080100144

RATIO 0F HALF-WIDTH 0F OPENINC TO NOTCH RADIUS R/R,

20

r-35 '._ 31$ I7 6 6 SKET&I OF OPENING 09 S-. S.. S.-'.5 '-S S.----'_UT 5. -'S 'S-

--5. -S' o CIRCULAR OPENING D SQUARE OPENING ROUNDED CORNERS SQUARE OPENING SHARP CORNERS DIO .32,18 .7 09 22j 8 016 021 005 DII I8 -S DIO -S -S

-02 021 -.

5- S-- 022 S-7S8 -S DIO -S 35,17 II,I8 32 021 S' - -S i69 S-.-'. ₂₂ -S-

₇

_e

'-'-_-_ I3j -'---u 20 '9 III 20 14 ICI

The average net stress at general yielding did not appear to be affected by the notch acuity to any appreciable extent.

R,.

However, an increase in the ratio, , which amounts to an

in-N

crease in the notch severity, reduced the ultimate strength, the energy absorption to ultimate load, and the elongation to ultimate load in a manner which was linearly related to the

logarithm of this ratio. The variation within the scatter

bands in these plots represents the effect of the percentage

of reinforcement and the geometric shape of the reinforcement,

In general, it was noted that the plates which developed

the higher ultimate strengths absorbed the most energy.

7° Effect of the percentage of reinforcement upon

properties of the plates with openings. The effect of the

percentage of reinforcement upon the properties of specimens

sustaining shear fractures is shown in Fig. 17. A slight

downward trend in the average net stress at general yielding and the ultimate strength and an increase in the ultimate load

was found as the percentage of reinforcement increased. The

load carrying capacity of the plates was increased by adding more reinforcement, but this improvement was accompanied by a

small reduction in the ultimate stress carrying capacity of

the plate. Thus the increase in load carrying capacity was

not commensurate with the added amount of reinforcement. No

significant change in the energy absorbing capacity of the plates was brought about by increasing the percentage of

50

50

34

30 0

7_.__ UI4SQI.I4 OPENING SHARp CORNERS _Lf5_ 45 0 20 40 60 80 lOO PERCENT 0F REINFORCEMENT 300 92O00 z 1200 o I-z o 800 o Ii, 400 UI z UI o

FIG. IT. EFFECT 0F PERCENTAGE 0F REINFORCEMENT UPON PROPERTIES 0F PLATES WITH OPENINGS.

OIl __- I2Qj 021 E22 2O _UI4 010 95 018 085 OIl 32 07 021 34 06 09 I2cOI6 20 7 OIS 13 U IS 14 UI3 010 018 012 06 U19 02 I4I6 III5 021 13 085 70 65 02 60 (n UI I-o CIRCULAR O SQUARE ROUNDED SQUARE SHARP OPENING OPENING CORNERS OPENING CORNERS CIRCULAR OPENING 5 018 DIO 06 4 017 022 20 12c016 SQUARE OPENING, oli 021 ROUNDED 085 Co,5 0I5 20 40 60 60 loo PERCENT 0F REINFORCEMENT loo ao 40 60 80 PERCENT 0F REINFORCEMENT lOO 20 40 60 80 PERCENT OF REINFORCEMENT 3 19 550 500 u, Q-O 450 -J UI I.-400 350

-6-Fig. 17 shows the general trends for all the types of

reinforcement. There existed for each type of reinforcement

s

an optimum percentage below which the plates failed through

the opening. Above this optirnuni percentage the reinforcement

tended to act as a rigid inclusion in the body plate, and failure occurred by shear in the weld joining the outer edge

of the reinforcement to the body plate. This latter mode of

failure resulted in somewhat reduced strength and energy

ab-sorption.

This optimum percentage of reinforcement was different

for each type of reinforcement. For example, it was around

3 to )Q per cent for a face bar, 95 to 100 per cent for a

single doubler plate, and somewhere between 30 and 60 per

cent for an insert plate. These values are tentative

inas-much as an insufficient number of tests were made to

estab-lish these values more definitely. However, they indicate

that the doubler plate type of reinforcement would be most

efficient for the higher percentages of reinforcement.

8. Effect of the geometric shape of the reinforcement

upon the properties of plates with openings. The previous

section showed that the optimum percentage of reinforcement

varIed for the different types of reinforcement. The reason

for this variation was found to lie in the geometric shape of

the cross section of the reinforcement, principally its width

the solutions by theory of elasticity for the reinforced open-ing assume plane stress conditions and therefore do not fit the actual problem, lt was necessary to develop an empirical parameter which would express the "shape factor" of the

rein-forcement. The square of the radius of gyration (the moment

of inertia of the net section of the specimen about the trans-verse centerline of the plate divided by the area of the net

section) was found to be a suitable parameter and will be

re-ferred to hereafter for brevity as k2. Various properties of

the plates with openings are related to lt in Fig, 18.

The average net stress at general yielding decreased as

the value of k2 increased to a value between 20 and 30, in

which range the triaxiality of stress induced by the width of

the reinforcement was maximum0 For higher values the greater

rigidity of the reinforcement, which tended to make lt act as

a rigid Inclusion, increased the yield stress somewhat.

The relations of the ultimate load, the ultimate strength,

and the energy absorption to ultimate load to the parameter k2

iere similar in nature. For the plates with the square

open-ing and the square openopen-ing with rounded corners, there was an

optimum value of k2, and the plotted points corresponding to

higher values of this parameter represent those plates where fracture occurred in the weld at the outer edge of the

rein-forcement or In the body plate. However, no such failures

50 30

-8-o I-z o I.-Q. o (n 3-o w z w 70 50 45 800 400 o O IO 20 30 40

(RADIUS 0F GYRATIONfXX IN 0.001 IN'

IO 20 30 40

(RADIUS 0F GYRATI0NQ N 0.001 IN'

FIG. IB. EFFECT 0F GEOMETRIC SHAPE OF REINFORCEMENT UPON PROPERTIES OF PLATES WITH OPENINGS.

02 018

-08 O4,__i20I6:i 20 022 085 ... fl9 IS

7

o

o CIRCULAR OPENINGSQUARE OPENING

ROUNDED CORNERS SQUARE OPENING SNA CORNERS 2 3 DIO 018 164 ₁₃ 085 085 0h

,joi

1 04 812 20 Q OIl

-05

Ji

13 /02 I

/-04 7 O IO 20 30 40 50

(RADIUS 0F GYRATI0NfIPd 0.001 IN'

O IO 20 30 40 50 (RADIUS 0F GrRATI0N IN 0.001 N' 2000 1600 P- I-1200 65 (n 60 55 600 550

r

450 -J n 400 350

this shape of opening no significant drop-off in strength or

energy absorption was found for the higher values of k20

Thus this empirical parameter, the square of the radius of gyration of the net section of the plate, appeared to de-scribe adequately and consistently the effect of the geomet-ric shape of the reinforcement upon the ultimate properties

of the plates0

There is good reason to believe that this parameter would be equally applicable to coamings, hatch corners, and other

similar details.

The data of these tests were combined with the data of

other tests of plates with reinforced

openings6

in

Fig0

l9

Unfortunately, only the ultimate strength, and not the energy

absorption of these latter tests, was recorded0 A correlation

similar to that in Fig. 18 was found here for the efficiency

rjth respect to ultimate strength0 In the Model Basin tests

plates with square openings and values of k2 larger than the optimum value almost failed in the weld at the outer edge of

the reinforcement or in the body plate0 Moreover, plates with

a circular opening and a value of k2 almost seven times the

maximum value for any specimen in the present tests showed only a slight reduction in efficiency with respect to ultimate

strength0 This last observation suggests the possibility that

it would be difficult to make a poor design of reinforcement

I

z w 100 o w a- z I- (D z 90 u, w I- 4 80 o I- I-. L) w 70 a. u) w

I

u z w u IL. (L. w 60 50 IO 20 30 40 50 60 (RADUJS 0F GYRATION)2 IN 0.001 IN x.x 90 V320 FIG. 19. EFFICIENCY

WITH RESPECT TO ULTIMATE STRENGTH OF PLATES WITH OPENINGS SUSTAINING SHEAR FRACTURE.

4

s

-I8 'I2 O "!'

82

011 Ø25 280 tI7 017 v48 216 lO Ø21 ?32 iO Q6 113 09 2 TESTS

SQUARE CIRCULAR SQUARE

D SQUARE 0 CIRCULAR OF TESTS U.S. IN OPENING, OPENING,

OPENING, OPENING, OPENING,

EXPT. MODEL 15 TillS REPORT ROUNDED X I/e' IS" X I/S' 36" X 36' X BASIN _CORNERS, /4' 1/4" 36' X 1/4' 015 02 022 Ø 18

.4

13 1 70 80

51

shape of the opening is evidenced. Contrariwise, as the notch

severity of the opening increases, the likelihood increases of losing some of the capacity to carry load or stress and absorb energy because of too much rigidity in the reinforcement in

the direction of the thickness of the body plate0

9. Overall ductility of jj plates with oDenings0 The

de-gree of ductility attained by the different specimens Is

sum-rnarized in Table VI0 While the average unit strain to ultimate

load in the plain plates exceeded 21 per cent, it ranged from approximately 2 to U per cent in the plates with openings0

Most of the values fell between 2 and 6 per cent. The strain

raising and ductility reducing effect of an opening in _a

struc-tural member was made quite apparent by these tests0

lO _{Efficiency of the plates with openig0 One purpose}

of the reinforcement is that of restoring to the greatest

pos-sible degree the properties of the plain plate0 The ratio of

the value of sorne particular property of a plate with an

open-ing to the similar value for a plain plate may be called the

efficiency with respect to the property under consideration0

This ratio expresses the degree to which the reinforcement restores the qualities which would exist In the plain plate0

Table VII lists the values of the efficiency of the

vari-ous 36-in, by 1/-f--in. plates with openings. _{The average of}

the values for the two plain plates was used as the basis for

ELONGATION TO ÏJLTIMATE LOAD AND FAILTJRE _{OF PLATES} WITH AND WITHOUT OPENI1GS

Te8t Gage

Total Elongation in

Temp.

length

Gage Length to:

Ultimate

Failure

Load

F.

In.

In.

In.

TABLE VI

Av. Unit Strain in

Gage Length to:

Ultimate

Failure

Load

in/in.

In./In.

Plates With Square Opening with Sharp Corrirs

_{(36e X 11w')}

14 o 78 36 2 .07 2.67

5.7

₇₀₎₃ 9 Face Bar 140 72 36 1.97 2 .73

5.5

7,6 99 Face Bar 110 -116 36 2.55 2.38

7l

6,6

10 Face Bar 16 75 36 3.011 14.00 1101 31 Face Bar 16 -146 36 3 .93 11.16 1009 11,6 15 Doubler 103 76 36 1,70

2 70

11.7 7 5 32 Doubler 103

46

36 _{1.93 2.30} 5.11 16 Doubler 52 73 36 2.00 _3.38

5.6

₉₀₁₄ 21

Insert

2 77 36 2 86 3.72

7.9

10,3 311

Insert

62 -146 36

_3.50

_{3.15 907}

_8.7

22

Insert

_{39 73} 36 1.62 2 .80 IL

5

7.8 85

Insert &

7708 76 36 3.117 11.37

9,6

12.1 Face Bar

Plates With Circular Opening

(36" x 1/14")

2 0 76 36 2.67 3q12 7.14 d.7 5 Face Bar 110 714 36 2,98 3.53 _{8 .3} 9,8 6 _{Face Bar 17 73 36 l914 2.6)4 703} 11 Doubler 102 75 36 2,88 3.38 800 9 .14 12 Doubler 50 73 36 1,88 2.55 5

2

7.1 17

Insert

₃₉ 7)4 3f 2 98 3.59 8 .3 10,0 18

In5ert

50 75 36 2,68 3140 8,0 9014

i

23

Plates

Plates Without Opening

_{(36" x i/li")}

21.5 21.11 1/11")

2).5

311.3 81 36 _{7.75 8,83} 76 36 7.70 12.35

!ith Square Opening with Sharp Corners

_{(36" x}

3 0 72 36 1.08 1.80

3.0

5 0

7 Face Bar 140 75 36 _1.19 2 .35 3 .3 0, 8

FaceBar

16 711 36 1.31 _{2 514} 3.6

s j

13 Doubler 1014 76 36 _0.97

2 10

2.7

S 1)4 Doubler _{51 71} 36 _{o 92}

2 Ci

_{2 6}

_{5 .6} 19

Insert

33 76 36 _0.73

2 00

2 0

5.6

20

_Insert

₃₉ 72 36 1.11? 2 00 11.1 5 .6 Spec,

feinSorcenent

No. 'Ì'ype Per

Spec. Reinforcement

No Per

Cent

-53-TA.BLE VI (Cont.)

ELONGATION TO ULTIMATE LOAD AND FAILURE OF PLATES WITH AND WIThOUT OPENINGS

Test Gage

Total Elongation

in

Tenp. Length Gage Length to:

Uitte

Failure

Load

F0 In, In. In.

Av. Unit Strain in Gage Length to:

Ultimate Failure

Load

In/In.

In./In.

95 96

Plates With Square Opening With Sharp Corners (36" x 1/2")

7.8 1.9

0 76 36 1.81 2,8].

0 -146 36 0,67 0.67

Plates With Square Opening With Rounded Corners _(36"

5.0

1.9

x 1/2") 37 0 76 36

_2.30

_{3.36 6.14 9.3} 38A 0 -20 36

_3.80

_{14.63 10.6 12.9} 36 0 0 36 3.60 3.60 10.0 10.0

Plates With Circular Opening

_{(36" x 1/2")}

69 0 76 36 2.145 3.57

6,8

9.9

Plates With

Square Opening With ktounded Corners _{(148" x 1/2")}

LiS' Face Bar ₃₃ 70 148 3,36 5.08

7.0

10.6

SO Face Bar ₃₃ -20 _{148 14.90 10,2 9.5} 51 Doubler 96 714 148 14.014 _{S .1S} 8.14 107 52 Doubler 96 -146 145 3.58 3.58 7.5 55 Insert 66 70 L8 _3.97 Ii .28 8.3 8,9 55A Insert 67 _{69 148 3.914 14.20 8,2}

_8.7

56 Insert _{66 -146 148 3.05 2 . 7}

_6.3

_5.7

70 Insert _{39 76} 148 3.25 _14.0

6.8

8.3 71 Insert 39 -146 148 2 00

2,0

_{14,2 I 2}