DESIGNOF

WELDEDSTRUCTURES

THE -JAMES F. LINCOLN ARC WELDING FOUNDATIONCLEVELAND OHIO

BY

er W. Blodgettmo

Published as a Service to Education

byTHE JAMES F. LINCOLN ARC WELDING FOUNDA liON

First Printing June 1966Fourteenth Printing May 1991

Special acknowledgment is herewith made to

Watson N. Nordquist

who has contributed much to the editingand organization of the material fromwhich this manual has been prepared

Trustees of the Foundation:

Dr. Donald N. Zwiep, Chairman,Worcester Polytechnic Institute,Worcester, Massachusetts

John T. Frieg, Trustee, Cleveland, Ohio

Leslie L. Knowlton, Trustee, Arter & Hadden,Cleveland, Ohio

Officers:

Secretary-Richard'S. Sabo, Cleveland, Ohio

Library of Congress Catalog Card Number: 66-23123

Printed in U.S.A.

Permission to reproduce any material contained herein will be granted upon request,provided proper credit is given to The James F. Lincoln Arc Welding Foundation,P. O. Box 17035, Cleveland, Ohio, 44117.

Copyright 1966 by The James F. Lincoln Arc Welding Foundation

The serviceability of a product or structure utilizing this type of information is andmust be the sole responsibility of the builder/user. Many variables beyond the controlof The James F. Lincoln Arc Welding Foundation affect the results obtained in applyingthis type of information. These variables include, but are not limited to welding proce-dure, plate chemistry and temperature, weldment design, fabrication methods andservice requirements.

PREFACE

WELDED STRUCTURAL CONNECTIONS have long been used in theconstruction of buildings, bridges, and other structures. The first welded buildingswere erected in the '20s-the greatest application being in low-level buildings ofmany types. The American Welding Society first published specifications forwelded bridges in 1936. But early progress came slowly.

During that year, 1936, The James F. Lincoln Arc Welding Foundationwas created by The Lincoln Electric Company to help advance the progress inwelded design and construction. Through its award programs and educationalactivities, the Foundation provided an exchange of experience and gave impetusto the growing application of welding.

Thus, within the last decade and particularly the past few years, unitizedwelded design has become widely accepted for high-rise buildings and bridgesof nobler proportions in addition to the broad base of more modest structures.

Now, the Foundation publishes this manual for further guidance andchallenge to architects, structural engineers, fabricators and contractors whowill build the structures of tomorrow ... and to the educators who will prepareyoung people for these professions. This material represents an interpretationof the best in accumulated experience of all who have participated in priorFoundation activities. The author has coordinated this with a continuing studyof current welding research conducted both in the United States and Europe,and against a background of participation on various code-writing committees.Much of the direct instructional information that resulted has been pretestedin over 70 structural seminars attended by over 4000 engineers.

The production of this manual has spanned several years during whichconstant effort was made to eliminate errors. The author will appreciate havingcalled to his attention any errors that have escaped his attention and invitescorrespondence on subjects about which the reader may have questions. Neitherthe author nor the publisher, however, can assume responsibility for the resultsof designers using values and formulas contained in the manual since so manyvariables affect every design.

June 1966

Secretary

The James F. Lincoln Arc Welding Foundation

CREDITS

The author and the publisher gratefully acknowledge the organi-zations and individuals who have contributed photographs orother illustrative material:

Allied Steel CorporationAllison Steel Mfg. Co.Allison Structural Steel Co.American Bridge Division,U.S. Steel Corporation

American Institute of Steel ConstructionAmerican Iron & Steel InstituteAmerican Welding SocietyBarber-Magee & HoffmanJohn F. Beasley Construction Co.Bethlehem Fabricating Co.Bethlehem Steel CorporationJ. G. BouwkampBurkhardt Steel CompanyThe California Co.California State Division of HighwaysCanadian Welding MagazineJ. A. Cappuccilli, ArchitectColumn Research CouncilConnecticut State Highway Dept.Dinwiddie Construction CompanyDominion Bridge Company, Ltd.Dominion Structural Steel Co., Ltd.B. M. Dornblatt & Associates, Inc.Dreier Structural Steel Co.Edmundson, Kochendoerfer & KennedyEngineering News-RecordEnglert Engineering CompanyFlint Steel CorporationFrankel Steel CompanyGeneral Electric Company,Industrial Heating Dept.

David R. Graham & AssociatesGranco Steel Products Co.Harley, Ellington, Cowin & Stirton, Inc.Haven-Busch Co.Herzberg & AssociatesHewitt-Robins, Inc.

Nathan N. HoffmanHoyle, Doran & BerryInland Steel CompanyJackson & Moreland Division,United Engineers and Constructors, Inc.

Kaiser Steel Corp.Kansas City Structural Steel Co.Felix M. Kraus, Consulting EngineerLehigh Construction CompanyLehigh University, Fritz Engineering LaboratoryRobert Charles Lesser, ArchitectR. C. Mahon CompanyP. H. Mallog Co.McGraw-Hill Book Co.Midwest Steel & Iron WorksNelson Stud Welding Division,Gregory Industries, Inc.

New England Construction MagazinePacific Car & Foundry Co.Pacific Iron and Steel CorporationPhillips-Carter-Osborn, Inc.Pittsburgh-Des Moines Steel Co.H. Platt CompanyPort of New York AuthorityProduct Engineering MagazineRepublic Steel CorporationJoseph T. Ryerson & Sons, Inc.Van Rensselaer P. Saxe, EngineerSchact Steel Construction, Inc.Steel Joist InstituteTennessee Gas Pipeline Co.United States Steel CorporationVermont Structural Steel Co.Paul Weidlinger, Consulting EngineersWelding Engineer MagazineWelding Research CouncilWest Coast Steel WorksMinoru Yamasaki-Smith, Hinchman & Grylls

In certain subject areas, the author has made adaptations of workdone by earlier investigators, to wit:

Friedrich Bleich"Buckling Strength of Metal Structures"McGraw-Hill Book Co., New York, N. Y.

Raymond Roark"Formulas for Stress and Strain"McGraw-Hill Book Co., New York, N. Y.

F. R. Shanley"Strength of Materials"McGraw-Hill Book Co., New York, N. Y.

S. Timoshenko"Theory of Elasticity"McGraw-Hill Book Co., New York, N. Y.

S. Timoshenko and S. Woinowsky Krieger"Theory of Plates and Shells"McGraw-Hill Book Co., New York, N. Y.

S. Timoshenko and James Gere"Theory of Elastic Stability"McGraw-Hill Book Co., New York, N. Y.

The publisher regrets any omissions from this list, and wouldappreciate being advised about them so that the records canbe corrected.

Introduction to Welded Construction

Properlies of MCiteriolsProperli of SectionBUIltUp Tension MembersAna lysis of BendingDeflection by BendinShear Deflection in BeamsDeflection of Curved BeamsD (gning fOr Impact loadsDesigning fot Fatigue loadsDesignmg for Torsional loadinAnalysi of Combined StressesBucklin of Plate.

Anolysi of Compre sionDesign ot Compr sslon MembersColumn Bas sColumn SpliceBaorlng-Pin ConnectionsDesigning Built Up Column

Welded Plate Girders for BuildingEfflclenl Plate GirdersWelded Plate Girders for BridgesBridge Pia e Girder witI Variable DepthGirders on 0 Ho izontol CurveTopered Gird rsOpen Web Expcmde Beams and GirdersShear ttcchment fIJr Composite

Construe ion -Build n9Shear Attachments for Composite

Constru in-BridgesFloor Systems for Bridg sOtthotropic Bridge DeckFabrica tion of Plate Girders and

Cover Plated BeamsField Welding of BuildingsField Weld ing of Bridg

1.1

2.12.22.3242.52.62.72.82.92.102.11212

3.13.23.33.43.53.

4.14.244.44.54.6

.7

4.8

4.94.10411

4.124134.14

TABLE OF

Part One

INTRODUCTION

Part Two

LOA D & STRESSANALYSIS

Part Three

COLUMN-RELATEDDESIGN

Part Four

GIRDER-RELATEDDESIGN

CONTENTS

Part FiveWELDED-CON NECTION

DESIGN

Part SixMISCELLANEOUS STRUCTURE

DESIGN

Beam- lumn Conneetlenst Angl ~

ti fene eat a keW F mrng Angle~Top on ding Plates or

imple Beams and Win BracingTop Connectin Pletes for

mr-Rieid onn clio sBeam to-Column ontinuau ConnedioB am- -Girder Continuo Conn die

ign of u e

Conn dlo s f r Tubul r ConnectionRigid-Frame nees (Elas ic e 'gn)W Idad Conn ction.. for Plastic De I nWelded C necn n for Vi r n el russe

D sign of Rigid Frames (Elastic De ign)Op n We r JoiReinf rdng 80Ho to Stiffen 0 PanelTanks. Bins an H pp rso igo of Han ers and Suppa

5.15.25.35.4

55

5.75.55.105.115.125.13

6.16.263

6.56.6

Part SevenJOINT DESIGN

AND PRODUCTION

S Iectio f ruc1ural St el orWelded Constructi 7.1

W Idebility and Welding Procedure 72Joint Design 7.3Oet rmi I geld rze 7.4Estimating Walding Cost 7.5WeI In 0 E)l"s ine Str duro 7.6Contr I hrmkag and Oi torhan 7.7Painting & orroslon of Ided SI cures 7.8Weld u Iity nd Inspe h n 7.9

Part EightREFERENCE DESIGN

FORMULAS

Bea . Diagr ms and F rmulaTrio Memb rOd rams nd rrnulcs

8.18.2

LIST OF SYMBOLS AND DEFINITIONS

E

r

f

s

thickness of section (In.}, time (min.); timeinterval (sec)material's tensile modulus of resilience(In-Ib/In." )material's ultimate energy resistance(in.-lb/in.3 )uniformly distributed load (Ibs/Iinear inch)length of moment arm (curved beam)distance of area's center of gravity to neutralaxis of entire section (in.)

y

u

w

x

A area (in. 2 ) ; total area of cross-sectionC stiffness factor used in moment distribution;

any specified constantE modulus of elasticity, tension (psi); arc volt-

age (volts)E. modulus of elasticity in shear (psi)E, tangential modulus of elasticity (psi)E, kinetic energyEp potential energyF total force (Ibs ): radial force (lbs)I moment of inertia (in.'); welding current

(amps)J polar moment of inertia (in.'); heat input

(joules/in. or watt-sec/in.)K ratio of minimum to maximum load (fatigue I;

ratio of web depth to web thickness; distancefrom outer face of beam flange to web toe offillet (in.}; thermal conductivity; any speci-fied constant

L length of member (in. or ft.); span betweensupports (In.)

L, effective length of columnM bending moment (in.-Ibs)

M, applied bending moment (in.-lbs)M, = plastic moment at connection (in.-lbs)N number of service cycles; minimum bearing

length of beam on seat (m.)P concentrated load (lbs)Q shear center; statical moment of cover plate

area about neutral axis of cover-plated beamsection

R reaction (lbs); torsional resistance of mem-ber (in}); weld cooling rate (0 F/ sec)

S section modulus (in.3 ) = I/cT torque or twisting moment (in.-lbs); tem-

perature (0F)U = stored energyV = vertical shear load (Ibs ), shear reaction;

velocity; volume; arc speed (in./min)W = total load (Ibs ), weight (Ibs ), total width

(in.)Y effective bearing length on base plate (in.)Z plastic section modulus (in.3 )

e.G. center of gravityHP horsepower

N.A. neutral axisRPM = revolutions per minute

c

a

v

b

a - angular acceleration (radians/sec/sec); in-cluded angle of beam curvature (degrees);form factor

tJ. = perpendicular deflection (in.), bending (tJ.b )or shear (tJ..)unit strain, elongation or contraction (in./in.)unit shear strain (in./in.)Poisson's ratio (steel = 0.3 usually); unitshear forceleg size of fillet weld (in.); rate of angularmotion about an axis (radians/sec)unit angular twist (radians/linear inch); in-cluded angle; angle of rotation

d

k

n

m

I = sumCT = normal stress, tensile or compressive (psi);

strength (psi)CTb = bending stress (psi)CTy = yield strength (psi)

7' = shear stress (psi); shear strength (psi)o angle of twist (radians; 1 radian = 57.3 de-

grees); angle of rotation (radians); slope oftapered girder; any specified angle

area of section beyond plane where stress isdesired or applied (in.2 ) ; length of plate(in.); acceleration or deceleration (ft/min,ft /sec}, clear distance between transversestiffeners of girder (in.)width of section (in.); distance of area's cen-ter of gravity to reference axis (in.)distance from neutral axis to extreme fiber(in.); distance of elastic center from refer-ence axisdepth of section (in.); moment arm of force( in. ); distance (In.), distance between cen-ters of gravity of girder flanges (in.)clear distance between girder flanges (in.)eccentricity of applied load (in.); total axialstrain (in.); moment arm of force (m.): ef-fective width (m.), length of Tee section inopen-web girder (in.)force per linear inch of weld (Ibs/In.): hori-zontal shear force (Ibsym.), (vectorial) re-sultant force (Ibsytn.), allowable strength ofweld (Ibsyin.)

fc' = compressive strength of concrete (psi)g acceleration of gravity (386.4"/sec2)h = height; height of fall; distance of expansion

on open-web girder (in.)any specified constant or amplification factormass; statical moment of transformed con-crete (composite construction)distance of section's neutral axis from refer-ence axis (in.); number of units in series

p = internal pressure (psi)q allowable force on shear connector

radius (In.), radius of gyrationlength of curved beam segment (in.); cleardistance between ends of increments of weld(in.)

S E C T I O N 1 . 1

I n t r o d u c t i o n t o

W e l d e d C o n s t r u c t i o n

1 . W E L D I N G ' S I M P O R T A N C E T O S T R U C T U R A L

F I E L D

W e l d i n g h a s b e e n a n i m p o r t a n t f a c t o r i n o u r e c o n o m y .

T h e p r o g r e s s m a d e i n w e l d i n g e q u i p m e n t a n d e l e c -

t r o d e s , t h e a d v a n c i n g a r t a n d s c i e n c e o f d e s i g n i n g f o r

w e l d i n g , a n d t h e g r o w t h i n t r u s t a n d a c c e p t a n c e o f

w e l d i n g h a v e c o m b i n e d t o m a k e w e l d i n g a p o w e r f u l

i m p l e m e n t f o r a n e x p a n d i n g c o n s t r u c t i o n i n d u s t r y .

M o r e a n d m o r e b u i l d i n g s a n d b r i d g e s a r e b e i n g

b u i l t a c c o r d i n g t o t h e p r e c e p t s o f g o o d w e l d e d d e s i g n .

T h e e c o n o m i e s i n h e r e n t i n w e l d i n g a r e h e l p i n g t o o f f s e t

e v o l u t i o n a r y i n c r e a s e s i n t h e p r i c e s o f m a t e r i a l s a n d

c o s t o f l a b o r . I n a d d i t i o n , t h e s h o r t e n e d p r o d u c t i o n

c y c l e s , m a d e p o s s i b l e b y w e l d i n g , h a v e h e l p e d e f f e c t

a q u i c k e n i n g i n t h e p a c e o f n e w c o n s t r u c t i o n .

W e l d e d c o n s t r u c t i o n h a s p a i d o f f h a n d s o m e l y f o r

m a n y a r c h i t e c t s , s t r u c t u r a l e n g i n e e r s , c o n t r a c t o r s , a n d

t h e i r c l i e n t - c u s t o m e r s . I t w i l l b e c o m e i n c r e a s i n g l y i m -

p o r t a n t a s m o r e p e o p l e a c q u i r e a g r e a t e r d e p t h o f

k n o w l e d g e a n d e x p e r i e n c e w i t h i t .

2 . R E C O G N I T I O N O F W E L D I N G

T h e w i d e s p r e a d r e c o g n i t i o n o f w e l d i n g a s a s a f e m e a n s

o f m a k i n g s t r u c t u r a l c o n n e c t i o n s h a s c o m e a b o u t o n l y

a f t e r y e a r s o f d i l i g e n t e f f o r t , p i o n e e r i n g a c t i o n b y t h e

m o r e p r o g r e s s i v e e n g i n e e r s a n d b u i l d e r s , a n d h e a v y

d o c u m e n t a t i o n o f r e s e a r c h f i n d i n g s a n d s u c c e s s e s a t -

t a i n e d .

T o d a y , t h e r e j u s t a r e n ' t m a n y m e n i n i n d u s t r y w h o

s p e a k d i s p a r a g i n g l y o f w e l d i n g . M o s t r e g u l a t o r y a g e n -

c i e s o f l o c a l a n d f e d e r a l g o v e r n m e n t n o w a c c e p t w e l d e d

j o i n t s w h i c h m e e t t h e r e q u i r e m e n t s i m p o s e d b y c o d e -

w r i t i n g b o d i e s s u c h a s t h e A m e r i c a n I n s t i t u t e o f S t e e l

C o n s t r u c t i o n a n d t h e A m e r i c a n W e l d i n g S o c i e t y .

W i t h t h i s a c c e p t a n c e , t h e r e r e m a i n s h o w e v e r a

c o n s i d e r a b l e t a s k o f e d u c a t i o n a n d s i m p l e d i s s e m i n a t i o n

o f i n f o r m a t i o n t o a c h i e v e m a x i m u m e f f i c i e n c y i n t h e

a p p l i c a t i o n o f w e l d e d d e s i g n . A n d , t h e r e i s e v e n a

c o n t i n u i n g n e e d f o r m o r e t h o r o u g h u n d e r s t a n d i n g o f

w e l d i n g b y c o d e w r i t i n g b o d i e s w h o f a i l t o u s e t h e f u l l

s t r e n g t h o f w e l d e d j o i n t s .

3 . W H Y W E L D E D C O N S T R U C T I O N ?

T h e r e a r e m a n y r e a s o n s f o r u s i n g w e l d e d d e s i g n a n d

c o n s t r u c t i o n , b u t p r o b a b l y t h e t w o b a s i c o n e s a r e 1 )

w e l d e d d e s i g n o f f e r s t h e o p p o r t u n i t y t o a c h i e v e m o r e

e f f i c i e n t u s e o f m a t e r i a l s , a n d 2 ) t h e s p e e d o f f a b r i c a -

t i o n a n d e r e c t i o n c a n h e l p c o m p r e s s p r o d u c t i o n s c h e d -

u l e s , e n a b l i n g t h e e n t i r e i n d u s t r y t o b e m o r e s e n s i t i v e

a n d r e a c t f a s t e r t o r a p i d l y s h i f t i n g m a r k e t n e e d s .

F r e e d o m 0 1 D e s i g n

W e l d i n g p e r m i t s t h e a r c h i t e c t a n d s t r u c t u r a l e n g i n e e r

c o m p l e t e f r e e d o m o f d e s i g n - f r e e d o m t o d e v e l o p a n d

u s e m o d e r n e c o n o m i c a l d e s i g n p r i n c i p l e s , f r e e d o m t o

F I G . 1 I n d i c a t i v e o f t h e d e s i g n f r e e -

d o m o f f e r e d b y u n i t i z e d w e l d i n g

d e s i g n , t h e Y a l e R a r e B o o k l i b r a r y ' s

f o u r o u t s i d e w a i f s a r e e a c h a

5 - s t o r y h i g h V i e r e n d e e l t r u s s . E a c h

i s a n e t w o r k o f G r e e k - t y p e c r o s s e s .

T h e s t r u c t u r e i s a l f w e l d e d - s h o p

a n d f i e l d .

1 . 1 - 1

~ l~~t1.1-2 / Introduction

employ the most elementary or most daring conceptsof form, proportion and balance to satisfy the need forgreater aesthetic value. Just about anything the de-signer may envision can now be given reality .because of welding.

Welded construction imposes no restrictions onthe thinking of the designer. Already, this has resultedin wide usage of such outstanding design advancementsas open-web expanded beams and girders, taperedbeams and girders, Vierendeel trusses, cellular floorconstruction, orthotropic bridge decks, composite floorconstruction, and tubular columns and trusses .

Weld Metal Superior to Base MetalA welded joint basically is one-piece construction. Allof the other methods of connecting members aremechanical lap joints. A properly welded joint isstronger than the material joined. The fused jointscreate a rigid structure in contrast to the nonrigidstructure made with mechanical joints. The compact-ness and calculable degree of greater rigidity permitsdesign assumptions to be realized more accurately.Welded joints are better for fatigue loads, impact loads,and severe vibration.

Welding Saves Weight, Cuts CostsConnecting steel plates are reduced or eliminated sincethey often are not required. Welded connections savesteel because no deductions need be made for ho lesin the plate: the gross section is effective in carryingloads. They oHer the best method of making rigid

con nections, resulting in reduced beam depth andweight.

This reduced beam depth can noticeably lower th eoverall height of a building. The weight of the structureand th erefore static loading is greatly reduced . Thissaves column steel, walls and partitions, facia , andreduced foundation requirements.

'Welded conne ctions ar e well suited to the newfield of plastic design, res ulting in further appreciableweight savings over con ventiona l rigid frame design.

Savings in transportation, handling time, and erec-tion are proportional to the weight savings.

Available StandardsArc welding, either in the shop or in the field, has beenused lon g enough to have been proved thoroughlydep endabl e. The AWS an d AISC ha ve set up dep end-able standa rds for all phases of structur al activity. Thesesta nda rds ar e backed up by yea rs of research andac tua l testing. They simplify th e design of welded con-nections and facilitate acceptance by purchasers andinspe ctors.

Other AdvantagesLess time is required on det ailin g, layout and fabrica-tion since fewer pieces are used . Punching or drilling,and reaming or coun tersinking are eliminated-a sub-stantial saving on large projects.

The typical weld ed joint produces a smooth, un-cluttered conn ection th at can be left exposed, withoutdet ract ing from th e appearance of the structure. W elded

FIG. 2 The a thlet ic unit of Ladue Jr. High School (Missouri) features an all-welded steellame lla roof fram e spa nning 252 ', expressing the strength of one-piece welded con-struction.

R E D U C T I O N I N P L A T E

S E < : T I O N ( I N P E R C E N T )

j o i n t s e x h i b i t l e s s c o r r o s i o n a n d r e q u i r e l i t t l e o r n o

m a i n t e n a n c e . T h e s m o o t h w e l d e d j o i n t s a l s o m a k e i t

e a s i e r t o i n s t a l l m a s o n r y , f a c i a a n d o t h e r c l o s e f i t t i n g

m e m b e r s , o f t e n r e d u c i n g t h e t h i c k n e s s o f w a l l s o r

B o o r s i n b u i l d i n g s .

S t r u c t u r e s c a n b e e r e c t e d i n r e l a t i v e s i l e n c e , a

d e f i n i t e a s s e t i n b u i l d i n g i n d o w n t o w n a r e a s , n e a r o f f i c e

b u i l d i n g s o r h o s p i t a l s .

4 . H O W G O O D I S A W E L D ?

M a n y e n g i n e e r s a r e u n a w a r e o f t h e g r e a t r e s e r v e o f

s t r e n g t h t h a t w e l d s h a v e , a n d i n m a n y c a s e s t h i s i s n o t

r e c o g n i z e d b y c o d e b o d i e s .

N o t i c e i n T a b l e 1 t h a t t h e m i n i m u m y i e l d s t r e n g t h s

o f t h e o r d i n a r y E 6 0 x x e l e c t r o d e s a r e a b o u t 5 0 % h i g h e r

t h a n t h e c o r r e s p o n d i n g v a l u e s o f t h e A 7 , A 3 7 3 a n d A 3 6

s t r u c t u r a l s t e e l s w i t h w h i c h t h e y w o u l d b e u s e d .

T A B L E 1 - C o m p a r i s o n o f T y p i c a l W e l d M e t a l s

a n d S t e e l s

M i n i m u m

M i n i m u m

M a t e r i a l

Y i e l d S t r e n g t h T e n s i l e S t r e n g t h

A W S A 5 . 1 &

E 6 0 1 0

5 0 , 0 0 0 p s i 6 2 , 0 0 0 p s i

A S T M A 2 3 3

E 6 0 1 2

5 5 , 0 0 0

6 7 , 0 0 0

W e l d

E6 0 2 4

5 0 , 0 0 0 6 2 , 0 0 0

M e t a l

E 6 0 2 7

5 0 , 0 0 0 6 2 , 0 0 0

( a s w e l d e d )

E 7 0 x x

6 0 , 0 0 0

7 2 , 0 0 0

A 7

3 3 , 0 0 0

6 0 , 0 0 0 t o 7 5 , 0 0 0

A S T M A 3 7 3

3 2 , 0 0 0

5 8 , 0 0 0 t o 7 5 , 0 0 0

S t e e l s A 3 6

3 6 , 0 0 0

5 8 , 0 0 0 t o 8 0 , 0 0 0

A 4 4 1

4 2 , 0 0 0

6 3 , 0 0 0

4 6 , 0 0 0

6 7 , 0 0 0

5 0 , 0 0 0

7 0 , 0 0 0

M a n y o f t h e c o m m e r c i a l E 6 0 x x e l e c t r o d e s a l s o

m e e t E 7 0 x x s p e c i f i c a t i o n s . U s e d o n t h e s a m e A 7 , A 3 7 3

a n d A 3 6 s t e e l s , t h e y h a v e a b o u t 7 5 % h i g h e r y i e l d

s t r e n g t h t h a n t h e s t e e l .

T h e r e a r e n u m e r o u s r e a s o n s w h y w e l d m e t a l h a s

h i g h e r s t r e n g t h t h a n t h e c o r r e s p o n d i n g p l a t e . T h e t w o

m o s t i m p o r t a n t a r e :

1 . T h e c o r e w i r e u s e d i n t h e e l e c t r o d e i s o f p r e -

m i u m s t e e l , h e l d t o c l o s e r s p e c i f i c a t i o n s t h a n t h e p l a t e .

2 . T h e r e i s c o m p l e t e s h i e l d i n g o f t h e m o l t e n m e t a l

d u r i n g w e l d i n g . T h i s , p l u s t h e s c a v e n g i n g a n d d e o x i d i z -

i n g a g e n t s a n d o t h e r i n g r e d i e n t s i n t h e e l e c t r o d e c o a t -

i n g , p r o d u c e s a u n i f o r m i t y o f c r y s t a l s t r u c t u r e a n d

p h y s i c a l p r o p e r t i e s o n a p a r w i t h e l e c t r i c f u r n a c e s t e e l .

B e c a u s e o f t h e s e , p r o p e r l y d e p o s i t e d w e l d s h a v e a

t r e m e n d o u s r e s e r v e o f s t r e n g t h o r f a c t o r o f s a f e t y ,

f a r b e y o n d w h a t i n d u s t r y s p e c i f i c a t i o n s u s u a l l y r e c o g -

n i z e . B u t e v e n w i t h o u t a r e d u c e d s a f e t y f a c t o r , t h e r e i s

a c o n s i d e r a b l e c o s t a d v a n t a g e .

~W'1" ,

I n t r o d u c t i o n t o W e l d e d C o n s t r u c t i o n 1 1 . 1 - 3

I n s p e c t i o n a n d Q u a l i t y

M u c h m o n e y i s s p e n t a n n u a l l y b y i n d u s t r y a n d g o v e r n -

m e n t i n o b t a i n i n g a n d i n s p e c t i n g f o r a s p e c i f i e d w e l d

q u a l i t y . U s u a l l y t h e w e l d q u a l i t y s p e c i f i e d i s o b t a i n e d ,

b u t t o o o f t e n t h e q u a l i t y s p e c i f i e d h a s l i t t l e o r n o r e l a -

t i o n t o s e r v i c e r e q u i r e m e n t s .

W e l d s t h a t m e e t t h e a c t u a l s e r v i c e r e q u i r e m e n t s ,

a t t h e l e a s t p o s s i b l e c o s t , a r e t h e r e s u l t o f -

1 ) p r o p e r d e s i g n o f c o n n e c t i o n s a n d j o i n t s ,

2 ) g o o d w e l d i n g p r o c e d u r e ,

3 ) g o o d w e l d o r t e c h n i q u e a n d w o r k m a n s h i p , a n d

4 ) i n t e l l i g e n t , r e s p o n s i b l e i n s p e c t i o n .

I n t h e f o l l o w i n g e x a m p l e s ( F i g u r e s 3 , 4 , 5 a n d 6 )

t e s t s p e c i m e n s e x h i b i t u n d e r c u t , u n d e r s i z e , l a c k o f

f u s i o n , a n d p o r o s i t y . I n s p i t e o f t h e s e a d v e r s e c o n d i t i o n s ,

1 / 2 H P t A T E - + I _ I I . . I I . 1J . . -

~OO~Z~Z~S

7 . 6 % 9 : 6 % / 5 . %

F I G . 3 T e s t s a m p l e s p r e p a r e d t o s h o w e f f e c t o f

u n d e r c u t . S a m p l e s w e r e p u l l e d i n t e n s i o n u n d e r a

s t a t i c l o a d ; i n a l l c a s e s f a i l u r e o c c u r r e d i n t h e p l a t e

a n d n o t i n t h e w e l d .

1/2 HPtAT~1 ~ ~ ~

~" ~" ~" - ~" -

T - - T - - T - 1

U l T . T E N S I L E Z q 6 0 0 2 q { ) O O 2 t 1 6 0 0 Z / I . 6 0 0

A T F A I L U R E ' , , ,

A W f A l l O W A B L E P E R I A I " h '

1 / 4 H F I L l E T , 2 4 0 0 L I I .

F I G . 4 O n e r u l e o f t h u m b s a y s f i l l e t s i z e s h o u l d e q u a l

% p l a t e t h i c k n e s s t o d e v e l o p f u l l p l a t e s t r e n g t h .

U s i n g t h i s m e t h o d , a % " f i l l e t w e l d o n ' 1 2 " p l a t e

s h o u l d " b e a t t h e p l a t e " . B u t s o d i d 1 1 / 3 2 " a n d

5 / 1 6 " f i l l e t s . N o t u n t i l f i l l e t s i z e w a s r e d u c e d t o V 4 "

d i d w e l d f a i l u r e o c c u r . . . a t a s t r e s s o f 1 2 , 3 0 0

I b s l l i n e a r i n . , m o r e t h a n 5 t i m e s t h e A W S a l l o w a b l e .

1.1-4 / Introduction

ALL WELD S MACHINED FLUSH

I/8"fKD ~w~w~~~~% THROATREDUCTION /2.5% /8.8 % 25 % 3/%

FIG. 5 Weld samples were made, withvarying degrees of lack of fusion, asreduced-section tensile specimens. Weldswere mach ined flush before testing, andweld failure did not occur until the un-penetrated throat dimension had reached31 % of the total joint throat.

considered individually, the we ld under steady tensileload was found to be stronger than the plate. Theseexamples are not meant to show that the standard ofweld quality should be lowered. However, they arestriking evidence of how easy it is to make full-strengthwelds, welds stronger than the plate.

Welding is the only process that produces aunitized, or one-piece, construction. The we lded plateis so sound, strong, and ductile as to permit sometesting procedures that frequent ly are impossible orimpractical to perform with other connection methods.

The weld is so du ctil e that it can be readily bent

around a small radius, Figure 7. Apparently becauseit is possible to do so, bend tests are often required.Unfortunately, U-bend test resu lts do not correlatewell with actual service performance.

Because it is possible to examine a we lde d join t byradiographic inspection, some engineers feel thi s mustbe done.

Most radiographic inspection is based on respon-sible standards. These specifications assure th e qu alityrequired, yet are realistic . Frequently, however , localdecisions are made to require more perfect radiographicsoun dness than th e specifications demand.

FIG. 6 Excessive porosity (weld 1) asshown by radiograph did not weaken thejoint. Weld 2 shows perfect. In both casesthe weld was stronger than the plate.Specimens broke in the plate at approxi-mately 60 ,100 psi.

H o w I m p o r t a n t I s P o r o s i t y ?

N o r m a l l y , p o r o s i t y i f i t s h o u l d e x i s t i s n o t a p r o b l e m ,

b e c a u s e e a c h v o i d i s s p h e r i c a l . I t d o e s n o t r e p r e s e n t

a n o t c h . E v e n w i t h a s l i g h t l o s s i n s e c t i o n b e c a u s e o f

t h e v o i d , i t s s p h e r i c a l s h a p e a l l o w s a s m o o t h f l o w o f

s t r e s s a r o u n d t h e v o i d w i t h o u t a n y m e a s u r a b l e l o s s i n

s t r e n g t h .

T e s t s h a v e s h o w n t h a t a w e l d c a n c o n t a i n a l a r g e

a m o u n t o f p o r o s i t y w i t h o u t m a t e r i a l l y c h a n g i n g t h e

t e n s i l e o r i m p a c t s t r e n g t h a n d d u c t i l i t y o f t h e w e l d .

T h i s p o r o s i t y c o u l d a m o u n t i n t o t a l v o l u m e t o a v o i d

e q u a l t o 7 % o f t h e w e l d ' s c r o s s - s e c t i o n w i t h o u t i m p a i r -

i n g t h e j o i n t ' s p e r f o r m a n c e .

T h e A S M E B o i l e r a n d P r e s s u r e V e s s e l C o d e , S e c -

t i o n V I I I a n d X , w i l l a l l o w p o r o s i t y i n a w e l d t o t h e

e x t e n t s h o w n o n c h a r t s i n c o r p o r a t e d i n t o t h e C o d e .

T h e s e c h a r t s c o n s i d e r s i z e , d i s t r i b u t i o n , a n d a l i g n m e n t

o f v o i d s , v e r s u s p l a t e t h i c k n e s s .

T h e A W S B u i l d i n g C o d e w i l l a l l o w a s l i g h t p o r o s -

i t y i f w e l l d i s p e r s e d i n t h e w e l d . T h i s i s d e f i n e d a s " g a s

p o c k e t s a n d a n y s i m i l a r g e n e r a l l y g l o b u l a r t y p e v o i d s . "

T h e A W S B r i d g e S p e c i f i c a t i o n a l l o w s s o m e p o r o s -

i t y . F o r p o r o s i t y a b o v e J i G " i n v o i d s i z e , a t a b l e s h o w s

m i n i m u m c l e a r a n c e b e t w e e n v o i d s a n d m a x i m u m s i z e

o f v o i d f o r a n y g i v e n p l a t e t h i c k n e s s .

5 . D E S I G N F O R W E L D I N G

A d e s i g n e r m u s t k n o w t h e f u n d a m e n t a l d i f f e r e n c e s b e -

t w e e n w e l d i n g a n d o t h e r a s s e m b l y m e t h o d s i f h e i s t o

d e t a i l e c o n o m i c a l w e l d e d m e m b e r s . I f a w e l d e d g i r d e r ,

I n t r o d u c t i o n t o W e l d e d C o n s t r u c t i o n / 1 . 1 - 5

F I G . 7 W e l d m e t a l i n

w e l l - d e s i g n e d j o i n t s

d e m o n s t r a t e m u c h

g r e a t e r d u c t i l i t y t h a n

w o u l d b e r e q u i r e d i n a n y

t y p e o f s t r u c t u r e s .

f o r e x a m p l e , w e r e c o n s t r u c t e d w i t h m u l t i p l e c o v e r

p l a t e s , t h e c o s t w o u l d b e e x c e s s i v e . T h e u s e o f o n l y

o n e f l a n g e p l a t e w i t h a r e a s o n a b l e n u m b e r o f b u t t

w e l d e d s p l i c e s , a t p o i n t s w h e r e t h e p l a t e t h i c k n e s s

c a n b e r e d u c e d , i s u s u a l l y a d e q u a t e a n d a l s o g i v e s

i m p r o v e d f a t i g u e r e s i s t a n c e .

T h e s e l e c t i o n o f a c o n n e c t i n g s y s t e m s h o u l d b e

m a d e a t t h e d e s i g n l e v e l ; f o r s o m e t y p e s o f s t r u c t u r e s ,

m a y e v e n i n f l u e n c e t h e a r c h i t e c t u r a l c o n c e p t i t s e l f .

F I G . 8 M a n y c o n t e m p o r a r y s t r u c t u r e s a r e u s i n g e x p o s e d s t e e l f r a m i n g a s p a r t o f t h e

a r t i s t i c s c h e m e . W e l d i n g p r o v i d e s t h e u n e n c u m b e r e d s i m p l i c i t y o f f o r m e s s e n t i a l t o

t h e m o d e r n l o o k i n a r c h i t e c t u r e , t y p i f i e d i n t h i s s h o w c a s e b u i l d i n g .

1.1-6 / Introduction

The most efficient use of steel is achieved with weldeddesign, the advantages of which grow with th e size ofthe structure. In fact, th e full advantages of usingsteel in compe tition with other materials will only berealized wh en th e structure is erected as a weldeddesign , and when fabricat ors and erectors use modemtechniques of welding, production scheduling, andmater ials handling.

A welded office building in Dallas , Texas, is anexample of th e economies possible in structural w eld-ing. The building is 413 feet high , has 34 floors, andcontains 600,000 square feet of usable floor space. Thesavings are impressive. Th e contractor states that by

FIG. 9 Welded connections contributed to safer andmore economical erection of the stately 33-storyHartford Building in San Francisco, California'stallest skyscraper. Semi-automatic welding, usingself-shielding cored electrode, speeded completionof 80 beam-to-column connections per floor.

designing for welding he saved 650 tons of steel. Com-parison estimates show an additional saving of app roxi-mately $16.00 per ton in fabrication and erection.Futhermore, approximately six months in constructiontim e will be saved as a result of using a weld ed steelframe.

Comparative experience has proved that had thistype structure involved weld ed connections that weresimply converted from another type of connection, th erestill would have been savings but substantially lessthan wh en designing specifically for welding.

6. WELDED DESIGN OF BUILDINGS

The tall er that buildings grow, the greater the role ofwelding. This applies to th e shop fabrication of columnsand oth er stru ctura ls, and also to the field weldingassociated with erection.

A majority of the more recently built skyscrapersare of welded design. These are found in all sectionsof th e country, including earthquake-prone San Fran-cisco.

Expanded open-web beams and girders-fabri-cated from standard rolled beams-are providing greatsavings in both bridge and building design. An open-web girder designed to have the required momentof inertia will result in a weight saving as high as 50%.In multi-story buildings, wh ere utility supply lines canbe run through th ese beams and girders rather thansuspended below, th e overall building height is sub-stantially shortened. This results in significant savingsin material costs-for columns, facia , stairs, etc.

The ease with which tapered beams and girderscan be fabricated from standard rolled beams permitsan endless variety of savings in building design. Tap-ered spandrel beams are often made deep enough atthe column end to reduce th e bending forc e and elim-inate need for column stiffeners. The spandrel beamis shop welded to th e column for lowest cost andshipped to th e site.

Special built-up columns can be used to ob-tain open , column-free interiors, to mount facia eco-nomically, to provide the steel-and-glass look whichdominates today's downtown and industrial park archi-tecture.

Th e new look in building design-esp ecially re-search centers , office buildings, libraries and museums-calls for a heavy use of exposed steels, including th ecorrosion-resistant steels such as ASTM A242. The cleantrim lines which are demanded with this use of exposedsteel can be achi eved only by welding.

Light, airy roof supporting space frames-three-dim ensional truss systems-are being shop-fabricatedin sections, final assembled on th e ground at th e siteand lift ed into place. W elding facilitat es th e use of

s u c h d e s i g n s , s i n c e t h e r e i s a l a c k o f e x t r a n e o u s m a -

t e r i a l i n t h e m u l t i p l i c i t y o f c o n n e c t i o n s a s w o u l d b e t h e

c a s e w i t h a n y o t h e r m e a n s o f a s s e m b l y .

P l a s t i c d e s i g n d o e s n o t u s e t h e c o n v e n t i o n a l a l l o w -

a b l e s t r e s s e s , b u t r a t h e r t h e c a l c u l a t e d u l t i m a t e l o a d -

c a r r y i n g c a p a c i t y o f t h e s t r u c t u r e . I n t h e c a s e o f r i g i d

f r a m i n g , p l a s t i c d e s i g n r e q u i r e s l e s s e n g i n e e r i n g t i m e

t h a n d o e s c o n v e n t i o n a l e l a s t i c d e s i g n a n d , i n m o s t

c a s e s , r e s u l t s i n s i g n i f i c a n t s a v i n g s i n s t e e l o v e r t h e

u s e o f e l a s t i c d e s i g n . W e l d i n g i s t h e m o s t p r a c t i c a l

m e t h o d o f m a k i n g c o n n e c t i o n s f o r p l a s t i c d e s i g n . T h i s

i s b e c a u s e t h e c o n n e c t i o n m u s t a l l o w t h e m e m b e r s t o

r e a c h t h e i r f u l l p l a s t i c m o m e n t s w i t h s u f f i c i e n t s t r e n g t h ,

a d e q u a t e r o t a t i o n a l a b i l i t y , a n d p r o p e r s t i f f n e s s .

7 . W E L D E D C O N S T R U C T I O N O F B R I D G E S

T o d a y b r i d g e s o f e v e r y t y p e - s u s p e n s i o n , a r c h , t r u s s ,

p l a t e a n d b o x g i r d e r , e t c . - a r e c o n s t r u c t e d o f s t e e l b e -

c a u s e o f s t r e n g t h , d e p e n d a b i l i t y , a n d p e r m a n e n c e . B e -

c a u s e t h e r e a r e n o l i m i t a t i o n s p l a c e d o n w e l d i n g , t h e

b r i d g e e n g i n e e r i s n o t l i m i t e d o r r e s t r i c t e d i n h i s t h i n k -

i n g . D u e t o t h i s n e w f r e e d o m o f d e s i g n e f f e c t e d b y

w e l d i n g , s o m e r a t h e r u n u s u a l a n d u n i q u e b r i d g e s h a v e

a p p e a r e d i n r e c e n t y e a r s .

T h e S t a t e o f C o n n e c t i c u t h a s f a v o r e d w e l d i n g

d e s i g n f o r i t s h i g h w a y b r i d g e s f o r o v e r 2 0 y e a r s . T h e

T u r n p i k e h a s 2 8 a l l - w e l d e d b r i d g e s , t h e l a r g e s t o f

w h i c h i s t h e 2 4 - s p a n , 2 6 6 1 - f o o t M i a n u s R i v e r B r i d g e a t

G r e e n w i c h . T h e e x p e r i e n c e o f t h e S t a t e s o f C o n n e c t i c u t ,

N e w Y o r k , T e x a s , C a l i f o r n i a a n d K a n s a s h a s c l e a r l y

s h o w n t h a t s u b s t a n t i a l s a v i n g s a r e p o s s i b l e i n p r o p e r l y

d e s i g n e d w e l d e d b r i d g e s .

B r i d g e g i r d e r s o f v a r i a b l e d e p t h e n h a n c e t h e

a p p e a r a n c e o f t h e s t r u c t u r e , w h i l e p l a c i n g t h e m e t a l

w h e r e n e e d e d a n d t a k i n g i t a w a y w h e r e s h a l l o w e r

s e c t i o n d e p t h i s p e r m i s s i b l e - t h e r e b y s a v i n g t o n s o f

s t e e l .

A 9 0 0 ' l o n g w e l d e d b r i d g e s p a n n i n g t h e t r a c k s o f

t h e E r i e R a i l r o a d o n t h e N e w Y o r k T h r u w a y h a d t o

b e s h a p e d t o m e e t s i t e r e q u i r e m e n t s . T h e T h r u w a y a t

t h i s p o i n t i s o n b o t h a v e r t i c a l g r a d e a n d a h o r i z o n t a l

c u r v e , r e q u i r i n g s u p e r e l e v a t i o n . I t i s e s t i m a t e d t h a t

m o r e - f l e x i b l e w e l d e d d e s i g n a l s o d e v e l o p e d a 5 0 % s a v -

i n g s i n t h e w e i g h t o f s t e e l .

I n b o t h b u i l d i n g a n d b r i d g e c o n s t r u c t i o n , t h e

d e v e l o p m e n t o f w e l d e d s h e a r c o n n e c t o r s a n d s p e c i a l -

i z e d w e l d i n g e q u i p m e n t f o r a t t a c h i n g s u c h c o n n e c t o r s

h a s a c c e l e r a t e d t h e u s e o f c o m p o s i t e f l o o r c o n s t r u c t i o n

- w h e r e t h e c o n c r e t e a n d s t e e l a c t t o g e t h e r w i t h a

s t r e n g t h g r e a t e r t h a n e i t h e r c o m p o n e n t , r e s u l t i n g i n

l a r g e s a v i n g s .

O r t h o t r o p i c b r i d g e d e s i g n , l o n g a c c e p t e d i n E u -

r o p e , i s c o m i n g i n t o p r o m i n e n c e i n A m e r i c a a s a m a j o r

a p p r o a c h t o r e d u c t i o n o f b r i d g e c o s t s . T h i s c o n c e p t c a l l s

I n t r o d u c t i o n t o W e l d e d C o n s t r u c t i o n / 1 . 1 - 7

F I G . 1 0 L a r g e b r i d g e s e c t i o n s a r e s h o p - f a b r i c a t e d ,

s h i p p e d t o t h e s i t e , a n d l i f t e d i n t o p o s i t i o n . T h i s

l o w e r s e r e c t i o n c o s t s a n d c o m p r e s s e s t h e p r o j e c t

t i m e t a b l e .

f o r t h e c o m p l e t e d e c k t o a c t a s a u n i t . O r t h o t r o p i c

d e s i g n c o u l d n o t b e e x e c u t e d w i t h o u t w e l d i n g .

8 . W E L D E D C O N S T R U C T I O N O F O T H E R

S T R U C T U R E S

W e l d i n g h a s f a c i l i t a t e d t h e d e s i g n a n d c o n s t r u c t i o n o f

a g r e a t v a r i e t y o f s t r u c t u r e s w i t h t h e c o n t e m p o r a r y l o o k .

E v e n w a t e r t o w e r s h a v e t a k e n o n a b e a u t y t h a t c o m p l e -

m e n t s a d j a c e n t a r c h i t e c t u r e .

S t a d i u m s f o r b i g - l e a g u e s p o r t s c l u b s a n d f o r b i g -

n a m e c o l l e g e s a r e l e a n i n g h e a v i l y o n w e l d i n g . A m o n g

t h e s e a r e S h e a S t a d i u m , A n a h e i m ' s n e w h o m e f o r t h e

A n g e l s , a n d o t h e r s . A v e r y u n i q u e f e a t u r e o f t h e m o d e m

s t a d i u m r e s u l t i n g f r o m w e l d e d s t e e l d e s i g n i s t h e

c a n t i l e v e r e d r o o f w h i c h r e m o v e s c o l u m n s a s o b s t r u c -

t i o n s t o s p e c t a t o r v i s i o n a n d p l e a s u r e .

T o w e r s , s p a c e n e e d l e s , h u g e r a d i o t e l e s c o p e s , r a d a r

a n t e n n a s , o f f - s h o r e d r i l l i n g r i g s , o r e u n l o a d e r s , a n d

m a n y o t h e r s t r u c t u r e s a r e b e i n g d e s i g n e d f o r w e l d e d

c o n s t r u c t i o n .

1.1-8 I Introduction

9. REVOLUTION IN SHOP FABRICATION &ERECTION

Today's structure goes up quickly due to welding. Thetrend is to build the structure on a sub-assembly basis,doing as much work as possible under ideal shop con-ditions where mass-production techniques can be fullyemployed.

The progress made in recent years in automatic andsemi-automatic welding equipment and in positionersand manipulators has made shop fabrication of specialgirders, knees, and built-up columns extremely attrac-tive. In many cases, the ingenious designer can maketremendous savings through the design of specialstructural members. This includes members havingcomplex cross-sectional configuration and hybrid mem-bers that are a mix of steels having different analyses.

IM'odern structural fabricating shops have fixturesfor assembling plates into columns and girders, manip-

ulato~s for welding automatically, and positioners forsupporting members so that attaching plates may bewelded in the fiat position.

Welding developments in the past few years havegreatly increased welding speeds, while assuring highquality welds. In submerged-arc welding the use ofmultiple arcs, with two and three welding heads has

tremendously increased welding speeds. Continuouswire processes for semi-mechanized welding for bothshop and field applications have substantially increasedproductivity.

Much progress has been made in automatic manip-ulators, enabling the welding head to be put intoproper alignment with the joint of the member in amatter of seconds. This alignment is automaticallymaintained along the length of the joint during welding.These manipulators represent a major cost reductionpossibility. As the size of the structure increases, thetotal arc time on a welded job becomes a decreasinglysmaller percentage of the total fabricating time. Thussavings in handling time and increasing manufacturingcycle efficiency are the major potentials for cost re-duction.

Semi-automatic field welding is speeding up erec-tion and lowering costs. Submerged-arc has long beenused in the field for fiat welding. Recently the use ofself-shielding cored electrode wire, automatically fed,has greatly extended the speed and uniform qualityinherent with semi-automatic welding. This process israpidly winning general acceptance. It is not affectedby rather severe wind and other adverse climatic con-ditions. Both submerged-arc and certain cored electrodeprocesses are considered low hydrogen.

1/2 II FILLETS ON BEAMS AND COLUMNSWELDING METHOD ARC/~PEEDIN. MIN.

STICK ELECTRODE (E 7028) SY2SINGLE ARC SEMI-AUTOMATIC (SUB-ARC) 12

~ SINGLE ARC SEMI-AUTOMATIC (INNERSHIELD) 12SINGLE ARC AUTOMATIC (SUB- ARC) 15TWIN ARC AUTOMATIC (SUB-ARC) 25TANDEM ARC AUTOMATIC (SUB-ARC) 30

r1 TANDEM AUTOMATICS (SUB-ARC) CD 18(BOTH WELDS CD AND ) (2=36 )SIMULTANEOUSLY = 36 IN. 1/2 FILLET/MIN.:J~: TRIPLE TANDEM AUTOMATICS (SUB-ARC)

P r o p e r t i e s

1 . I M P O R T A N C E O F P R O P E R T I E S

A l l m a t e r i a l s h a v e c e r t a i n p r o p e r t i e s w h i c h m u s t b e

k n o w n ' i n o r d e r t o p r o m o t e t h e i r p r o p e r u s e . T h e s e

p r o p e r t i e s a r e e s s e n t i a l t o s e l e c t i o n o f t h e b e s t m a t e r i a l

f o r a g i v e n m e m b e r . *

I n t h e d e s i g n o f s t r u c t u r a l m e m b e r s , t h e p r o p e r t i e s

o f m a t e r i a l s w h i c h a r e o f p r i m a r y c o n c e r n a r e t h o s e

t h a t i n d i c a t e m a t e r i a l b e h a v i o r u n d e r c e r t a i n t y p e s o f

l o a d . S o m e p r o p e r t y o f m a t e r i a l i s c a l l e d f o r i n e a c h o f

t h e b a s i c d e s i g n f o r m u l a s .

P r o p e r t i e s c o m m o n l y f o u n d i n e n g i n e e r i n g h a n d -

b o o k s a n d s u p p l i e r s c a t a l o g s a r e t h e s e :

1 . u l t i m a t e t e n s i l e s t r e n g t h

2 . y i e l d s t r e n g t h i n t e n s i o n

: 3 . e l o n g a t i o n

4 . m o d u l u s o f e l a s t i c i t y

5 . c o m p r e s s i v e s t r e n g t h

6 . s h e a r s t r e n g t h

7 . f a t i g u e s t r e n g t h

O t h e r p r o p e r t i e s s u c h a s m o d u l u s o f r e s i l i e n c e a n d

u l t i m a t e e n e r g y r e s i s t a n c e , m a y a l s o b e g i v e n .

T a b l e s 1 a n d 2 p r e s e n t p h y s i c a l p r o p e r t i e s a n d

c h e m i c a l c o m p o s i t i o n o f v a r i o u s s t e e l s . T h e s e a r e p r o -

. " A l s o s e e " M e t a l s a n d H o w t o W e l d T h e m " b y T . B . J e f f e r s o n

a n d G . W o o d s ; J a m e s F . L i n c o l n A r e W e l d i n g F o u n d a t i o n .

S E C T I O N 2 . 1

o f M a t e r i a l s

p r i e t a r y s t e e l s t h a t a r e n o t p r o v i d e d f o r b y t h e A S T M

s p e c i f i c a t i o n s f o r b a s i c s t e e l s u s e d i n t h e s t r u c t u r a l f i e l d .

T h e s p e c i f i c a t i o n s t e e l s a r e c o v e r e d i n S e c t i o n 7 . 1 o n

t h e S e l e c t i o n o f S t r u c t u r a l S t e e l .

1 I t - ,~) ( - - < I I

1 [ 1 g J I

f - - - - - Z1 1 ' : " - - . . .

f i n o I d i s t a n c e o r - z : s . y "

e l o n q a t i o n I n 2 : "

F I G . 1 T e n s i l e t e s t s p e c i m e n b e f o r e a n d a f t e r

t e s t i n g t o f a i l u r e , s h o w i n g m a x i m u m e l o n g a t i o n .

P r o d u c e r

G r e a t L a k e s S t e e l

J o n e s & L a u g h l i n

L u k e n s S t e e l

R e p u b l i c S t e e l

U S S t e e l

Y o u n g s t o w n S h e e t

& T u b e

T A B L E

1 - P r o p e r t i e s

a n d

C o m p o s i t i o n

o f C o n s t r u c t i o n a I A l l o y S t e e l s

Y i e l d U l t .

N o m i n a l C o m p o s i t i o n , %

A l l o y P o i n t , S t r e n g t h , E l o n g . , C M n

S i C u M o

C r

N i

p s i p s i

%

N - A - X t r a

8 0 8 0 0 0 0 9 5 . 0 0 0

1 8 0 . 1 5 0 . 8 0 0 . 7 0 0 . 2 0 0 . 6 5

9 0 9 0 . 0 0 0 1 0 5 . 0 0 0 1 8

0 . 1 5 0 8 0 0 . 7 0 0 . 2 0 0 . 6 5

1 0 0 1 0 0 . 0 0 0

, 1 5 . 0 0 0

1 8 0 . 1 5 0 . 8 0

0 . 7 0

0 2 0 0 . 6 5

1 1 0

1 1 0 . 0 0 0 1 2 5 . 0 0 0

1 8

0 . 1 5 0 . 8 0 0 . 7 0 0 . 2 0

0 . 6 5

J a l l o y - S - 9 0

9 0 , 0 0 0

1 0 5 . 0 0 0

1 8 0 . 1 5 1 . 2 5 0 . 2 5 0 . 2 5

J o l l o v - S v l O o

1 0 0 . 0 0 0 1 1 5 , 0 0 0

1 8 0 . 1 5 1 . 2 5

0 . 2 5

0 . 2 5

J a l l o y - S l I 0

1 1 0 . 0 0 0

1 2 5 , 0 0 0 1 8 0 . 1 5

1 . 2 5 0 . 2 5 0 . 2 5

T I

1 0 0 . 0 0 0 1 1 5 . 0 0 0

1 8

0 . 1 5

0 . 8 0

0 . 2 5 0 . 3 5 0 . 5 5

0 . 6 0

0 . 8 5

R e p u b l i c 6 5

6 5 . 0 0 0 8 5 . 0 0 0

2 0 0 . 1 5 1 . 0 0 0 . 1 5 1 . 1 5

0 . 2 5

1 . 2 5

7 0

7 0 . 0 0 0 9 0 . 0 0 0

1 8 0 . 2 0 1 . 0 0 0 . 1 5 1 . 2 5

0 . 2 5

1 . 5 0

T - l

1 0 0 . 0 0 0 1 1 5 . 0 0 0

1 8 0 . 1 5

0 . 8 0

0 . 2 5 0 . 3 5 0 . 5 5 0 . 6 0 0 . 8 5

Y o l o y S

6 5 . 0 0 0 9 5 . 0 0 0

2 0 0 . 1 2 0 . 6 0 0 . 3 0 1 . 0 0 1 . 8 0

O t h e r

0 . 0 9 Z r

0 . 0 9 Z r

0 . 0 9 Z r

0 . 0 9 Z r

C b

C b

V . B

V , B

- T a b l e c o u r t e s y P R O D U C T E N G I N E E R I N G M a g a z i n e

2 . 1 - 1

2.1-2 / Load & Stress Analysis

TABLE 2-Properties and Composition of High-Strength Low Alloy Steels

Yield Ult. Nominal Composition, 0/0Producer Alloy Point, Strength, Elong., C Mn Si Cu Mo Cr Ni Other

psi psi %

Alan Wood Steel Dynalloy I 50,000 70,000 22 0.15 0.80 0.30 0.45 0.10 0.55Dynalloy II 45,000 62,000 25 0.15 0.80 0.30 0.45 0.10 0.55

Armco Steel High Strength No.1 50,000 70,000 22 0.15 0.70 0.15 0.60 0.752 45,000 64,000 0.15 0.70 0.15 0.60 0.753 40,000 60,000 35 0.10 0.60 0.10 0.20 0.02 V4 50,000 70,000 22 0.25 1.35 0.25 0.205 45,000 60,000 25 0.22 ) .25 0.30 0.20 0.02 V I

8ethlehem Steel Mayari R 50,000 70,000 22 0.12 0.75 0.55 0.50 0.70 1.0 0.10 ZrMedium Manganese 50,000 75,000 20 0.25 1.35 0.30 0.30Manganese Vanadium 50,000 70,000 22 0.22 1.25 0.30 0.20 0.02 V

Crucible Steel Maxeloy 50,000 70,000 22 0.15 1.20 0.50 0.20 0.50of America

Colorado Fuel Clay-Loy 50,000 70,000 0.22 1.25 0.35 0.50 0.2 V& Iron

Inland Steel Hi-Steel 50,000 70,000 22 0.12 0.75 0.15 0.95 0.18 0.55Hi-Man 50,000 75,000 20 0.25 1.35 0.30 0.20Hi-Man 440 (A440l 50,000 70,000 0.28 1.35 0.30 0.20Tri-Steel 50,000 70.000 22 0.22 1.25 0.30 0.20 0.02 V

Jones & Laughlin Jalten No.1 50,000 70,000 22 0.15 1.30 0.10 0.30 0.05 V2 50,000 70,000 22 0.15 1.40 0.10 0.303 50,000 70,000 22 0.25 1.50 0.25 0.20

JLX-45-W 45,000 65,000 22 0.15 0.75 0.10 0.03 Cb-50-W 50,000 70,000 22 0.15 0.75 0.10 0.03 Cb-55-W 55,000 75,000 22 0.15 0.75 0.10 0.03 Cb-60-W 60,000 80,000 22 0.15 0.75 0.10 0.03 Cb

Kaiser Steel Kaisaloy No. I 50,000 70,000 23 0.20 1.25 0.60 0.35 0.15 0.25 0.60 V, Ti2 45,000 60,000 25 0.12 0.60 0.50 0.30 0.10 0.25 0.60 V, Ti3 58,000 83,000 15 0.30 1.50 0.35 0.35 0.10 0.25 0.40 V, Ti

Structural High Strength 50,000 75,000 18 0.27 1.60 0.30 0.20

Lukens Steel Cor-Ten 50,000 70,000 22 0.12 0.35 0.50 0.40 0.80 0.65

Notional Steel GLX-45-W 45,000 65,000 22 0.15 0.75 0.10 0.03 Cb(Great Lakes GLX-50-W 50,000 70,000 22 0.15 0.75 0.10 0.03 Cb

Steel and GLX-55-W 55,000 75,000 22 0.15 0.75 0.10 0.03 CbWeirton Steel) GLX-60-W 60,000 80,000 22 0.15 0.75 0.10 0.03 Cb

N-A-X High Tensile 50,000 70,000 22 0.15 0.75 0.75 0.25 0.20 0.55 0.10 ZrN-A-X High Manganese 50,000 70,000 22 0.25 1.35 0.30 0.20

Pittsburgh Steel Pitt-Ten No.1 50,000 70,000 22 0.12 0.75 0.20 0.85 0.70

Republic Steel Republic 50 50,000 70.000 22 0.15 0.75 0.65 0.10 0.30 0.75Republic M 50,000 75,000 20 0.25 1.35 0.30 0.20

US Steel Cor-Ten 50,000 70,000 22 0.12 0.35 0.50 0.40 0.80 0.65Ex-Ten-45 45,000 0.20 0.75 0.10 0.01 CbEx-Te-n-50 50,000 0.25 0.75 0.10 0.01 CbMan-Ten 50,000 75,000 20 0.25 1.35 0.30 0.20Man-Ten IA440) 50,000 70,000 0.28 1.35 0.30 0.20Par-Ten 45,000 62,000 28 0.12 0.75 0.10 0.04 VTri-Ten 50,000 70,000 22 0.22 1.25 0.30 0.20 0.02 V

Youngstown Yolay 50,000 70,000 22 0.15 0.75 0.30 1.00 1.70Sheet & Tube Yaloy A242 50,000 70,000 22 0.22 1.25 0.30 0.20 0.02 V

Yalay E HSX 45,000 80,000 25 0.18 1.00 0.30 0.35 0.40 0.70Yoloy EHS 50,000 70,000 22 0.18 1.00 0.30 0,35 0.40 040 0.70Yolay M-A 50,000 70,000 20 0.25 1.60 0,30 0.35Yoloy M-8 45,000 70,000 22 0.2:1 1.40 0.25 0.20Yolay 45W 45,000 65,000 30 0.15 0.65 CbYoloy 50W 50,000 70,000 28 0.15 0.65 Cb

- Table courtesy PRODUCT ENGINEERING Magazine

FIG. 2 A tensile testing mac hine a pp lies apulling for ce on the tes t piece. The max imumload applied be fore failure of the piece,divided by the orig ina l cross-secti on, eq ua lsthe materia l's ultimate tensile stre ngt h.

The vari ous properties ar e best defined by adescription of what happens when a specime n of thematerial is subjec ted to load duri ng laboratory tests.

2. TENSILE PROPERT I ES

In a tensile tes t, the machi ned and ground sp ec imenof the mat erial is marked with a centerpunc h at tw opoints 2" apa r t, as shown in Figure 1. Thc specimenis placed in a ten sile test ing machine, and an axial loadis appl ied to it by pulling the jaws holding th e ends ofthe speci me n in opposing directions at a slow andconstant rat e of speed , F igure 2.

As the pulling progresses, the specimen elongatesat a uniform ra te which is proportionate to the rate atwhich the load or pulling for ce increases. The load

70 -I----+---+---+---+-- +-- -+--1

50 -+ --+--/'"o,

0 40oo

>'30'"~

V) 20

10

oo 0,025 0.050 0.075 0.1 00 0.125 0.150 0.175 Q200 Q225

Stra in , in/ in.

FIG. 3 A stress-strain diagra m for mild ste e l,showing ultima te tensile stren gth and ot he rproperties. Here, the most cri tica l portion ofthe curve is magnified.

Properties of Materials / 2.1-3

divided by th e cross-secti ona l area of the specimenwithin th e gag e marks represents the un it stress orresistan ce of th e mat er ial to the pull ing or tensile force.This stress ( if) is expr essed in pounds per square inch,psi. T he elonga tion of the specimen represents thestrain ( E) induced in th e ma te rial and is expressed ininch es per inch of length, in.ym. Stress and stra in areplo tted in a diagram, shown in simp lified fonn inF igur e 3.

The propor tional relationsh ip of load to elongation,or of stress to strain, continues un til a point is reachedwh ere the elon ga tion begins to increase at a Fas ter rat e.This point, beyo nd which the e longation of the speci-men no longer is proportional to the load ing, is theprop ortional elast ic limit of the material. When theload is removed, the specimen retu rn s to its origina ldimen sions.

Beyond the elastic limit, further mov emen t of thelest machine jaws in opposing directions causes apermanent elongation or deformation of the specimenmat eri al. In the case of a low- or med ium-carbon stee l,a point is reached beyond which the met al stretchesbriefly witho ut an inc rease in load. This is the yieldpoint.

For low- an d med ium-carbon steels, the un it stressat the yield point is considered to be the ma terial'stensile yield strength ( if,) .'" For other metals, the yieldstrengt h is the stress requ ired to strain the specimen bya sp ecified small amount be yon d the clastic limit. Fo rordi nary com mercia l purposes, the cla stic limit is as-sumed to coincide with the yie ld streng th .

Beyond the material's elastic limit, continued pull-ing causes the specime n to neck down across itsdiameter or wid th. T his action is accompanied by a

':' The symbols co mmonly used for yield st ren g th , ul timat estre ng th , and axia l stra in do not ind icat e th e typ e of land.

2.1-4 / Load & Stress Analysis

FIG. 4 Stress-strain curves for several materialsshow their relative elasticity. Only that portionof curve displaying a proportional relationshipbetween stress and strain is diagrammed.

further acceleration of the axial elongation, which isnow largely confined within the relatively short necked-down section.

The pulling force eventually reaches a maximumvalue and then falls off rapidly, with little additionalelongation of the specimen before failure occurs. Infailing, the specimen breaks in two within the necked-down portion. The maximum pulling load, expressedas a stress in psi of the original cross-sectional area ofthe specimen, is the material's ultimate tensile strength(

P r o p e r t i e s o f M a t e r i a l s / 2 . 1 - 5

4 . S H E A R S T R E N G T H

F I G . 5 F a t i g u e t e s t r e s u l t s a r e p l o t t e d o n < T - N

d i a g r a m ; s t r e s s v s . n u m b e r o f c y c l e s b e f o r e

f a i l u r e .

2 0

. 1 0 ' 1 0 ' 1 0 ' 1 0

7

1 0 '

" N " - C y c l e s o f S t r e s s

b e d i s c u s s e d m o r e c o m p l e t e l y u n d e r S e c t i o n 3 . 1 .

W i t h l o n g c o l u m n s , t h e e f f e c t o f e c c e n t r i c l o a d i n g

i s m o r e s e v e r e i n t h e c a s e o f c o m p r e s s i o n t h a n t e n s i o n .

u n d e r a s p e c i f i c l o a d v a l u e e x p r e s s i b l e a s a u n i t s t r e s s .

T h e u n i t s t r e s s i s p l o t t e d f o r e a c h s p e c i m e n a g a i n s t

t h e n u m b e r o f c y c l e s b e f o r e f a i l u r e . T h e r e s u l t i s a

< T - N d i a g r a m ( F i g . 5 ) .

T h e e n d u r a n c e l i m i t ( u s u a l l y < T l ' ) i s t h e m a x i m u m

s t r e s s t o w h i c h t h e m a t e r i a l c a n b e s u b j e c t e d f o r a n

i n d e f i n i t e s e r v i c e l i f e . A l t h o u g h t h e s t a n d a r d s v a r y

f o r v a r i o u s t y p e s o f m e m b e r s a n d d i f f e r e n t i n d u s t r i e s ,

i t i s a c o m m o n p r a c t i c e t o a c c e p t t h e a s s u m p t i o n t h a t

c a r r y i n g a c e r t a i n l o a d f o r s e v e r a l m i l l i o n c y c l e s o f

s t r e s s r e v e r s a l s i n d i c a t e s t h a t l o a d c a n b e c a r r i e d f o r

a n i n d e f i n i t e t i m e .

T h e o r e t i c a l l y t h e l o a d o n t h e t e s t s p e c i m e n s s h o u l d

b e o f t h e s a m e n a t u r e a s t h e l o a d o n t h e p r o p o s e d

m e m b e r , i . e . t e n s i l e , t o r s i o n a l , e t c . ( F i g . 6 ) .

S i n c e t h e g e o m e t r y o f t h e m e m b e r , t h e p r e s e n c e

o f l o c a l a r e a s o f h i g h s t r e s s c o n c e n t r a t i o n , a n d t h e

c o n d i t i o n o f t h e m a t e r i a l h a v e c o n s i d e r a b l e i n f l u e n c e

o n t h e r e a l f a t i g u e s t r e n g t h , p r o t o t y p e s o f t h e m e m b e r

o r i t s s e c t i o n w o u l d g i v e t h e m o s t r e l i a b l e i n f o r m a t i o n

a s t e s t s p e c i m e n s . T h i s i s n o t a l w a y s p r a c t i c a l h o w -

e v e r . L a c k i n g a n y t e s t d a t a o r h a n d b o o k v a l u e s o n

e n d u r a n c e l i m i t , s e e S e c t i o n 2 . 9 o n F a t i g u e .

-~

I

I

~

o 0

E n d u r a n c e

o ( )

1 0

Li~,t

5 0

4 5

' "Q .

0

4 0

0

0

' "

3 5

' "

~

V i

3 0

I

c

2 5

6 . I M P A C T P R O P E R T I E S

I m p a c t s t r e n g t h i s t h e a b i l i t y o f a m e t a l t o a b s o r b t h e

e n e r g y o f a l o a d r a p i d l y d e l i v e r e d o n t o t h e m e m b e r .

A m e t a l m a y h a v e g o o d t e n s i l e s t r e n g t h a n d g o o d

d u c t i l i t y u n d e r s t a t i c l o a d i n g , a n d y e t b r e a k i f s u b j e c t e d

t o a h i g h - v e l o c i t y b l o w .

T h e t w o m o s t i m p o r t a n t p r o p e r t i e s t h a t i n d i c a t e

t h e m a t e r i a l ' s r e s i s t a n c e t o i m p a c t l o a d i n g a r e o b t a i n e d

f r o m t h e s t r e s s - s t r a i n d i a g r a m ( F i g . 7 ) . T h e f i r s t o f

t h e s e i s t h e m o d u l u s o f r e s i l i e n c e ( u ) w h i c h i s a

m e a s u r e o f h o w w e l l t h e m a t e r i a l a b s o r b s e n e r g y p r o -

v i d i n g i t i s n o t s t r e s s e d a b o v e t h e e l a s t i c l i m i t o r y i e l d

L E V E R

W I L S O N F A T I G U E T E S T I N G M A C H I N E

L O W E R P U L L H E A D

T E S T S P E C I M E N

U P P E R P U L L H E A D

F I G . 6 T y p i c a l s e t u p f o r f a t i g u e t e s t i n g u n d e r

p u l s a t i n g a x i a l s t r e s s e s .

o

.

.

o

o

5 . F A T I G U E S T R E N G T H

T h e r e i s n o r e c o g n i z e d s t a n d a r d m e t h o d o f t e s t i n g

f o r s h e a r s t r e n g t h o f a m a t e r i a l . F o r t u n a t e l y , p u r e

s h e a r l o a d s a r e s e l d o m e n c o u n t e r e d i n s t r u c t u r a l m e m -

b e r s b u t s h e a r s t r e s s e s f r e q u e n t l y d e v e l o p a s a b y -

p r o d u c t o f p r i n c i p a l s t r e s s e s o r t h e a p p l i c a t i o n o f

t r a n s v e r s e f o r c e s .

T h e u l t i m a t e s h e a r s t r e n g t h i s o f t e n o b t a i n e d f r o m

a n a c t u a l s h e a r i n g o f t h e m e t a l , u s u a l l y i n a p u n c h - a n d -

d i e s e t u p u s i n g a r a m m o v i n g s l o w l y a t a c o n s t a n t r a t e

o f s p e e d . T h e m a x i m u m l o a d r e q u i r e d t o p u n c h t h r o u g h

t h e m e t a l i s o b s e r v e d , a n d u l t i m a t e s h e a r s t r e n g t h i s

c a l c u l a t e d f r o m t h i s .

W h e r e i t i s n o t p r a c t i c a l t o p h y s i c a l l y d e t e r m i n e

i t , t h e u l t i m a t e s h e a r s t r e n g t h ( T ) i s g e n e r a l l y a s s u m e d

t o b e 3 f 4 t h e m a t e r i a l ' s u l t i m a t e t e n s i l e s t r e n g t h f o r

m o s t s t r u c t u r a l s t e e l s .

W h e n t h e l o a d o n a m e m b e r i s c o n s t a n t l y v a r y i n g i n

v a l u e , i s r e p e a t e d a t r e l a t i v e l y h i g h f r e q u e n c y , o r

c o n s t i t u t e s a c o m p l e t e r e v e r s a l o f s t r e s s e s w i t h e a c h

o p e r a t i n g c y c l e , t h e m a t e r i a l ' s f a t i g u e s t r e n g t h m u s t

b e s u b s t i t u t e d f o r t h e u l t i m a t e s t r e n g t h w h e r e c a l l e d

f o r b y t h e d e s i g n f o r m u l a s .

U n d e r h i g h l o a d v a l u e s , t h e v a r i a b l e o r f a t i g u e

m o d e o f l o a d i n g r e d u c e s t h e m a t e r i a l ' s e f f e c t i v e u l t i -

m a t e s t r e n g t h a s t h e n u m b e r o f c y c l e s i n c r e a s e s . A t

a g i v e n h i g h s t r e s s v a l u e , t h e m a t e r i a l h a s a d e f i n i t e

s e r v i c e l i f e , e x p r e s s e d a s " N " c y c l e s o f o p e r a t i o n .

A s e r i e s o f i d e n t i c a l s p e c i m e n s a r e t e s t e d , e a c h

2.1-6 / Load & Stress Analysis

Unitstress(a)

o B

au

Unit strain (f) D

C FIG. 7 In the stress-strain dia-gram for impact, the elongationat moment of ultimate stress isa factor in determining thetoughness of the material interms of ultimate energy re-sistance.

point. It indicates the material's resistance to deforma-tion from impact loading. (See Section 2.8 on Impact.)

The modulus of resilience (u) is the triangulararea OAB under the stress-strain curve having its apexat the elastic limit. For practicality let the yield strength((Ty) be the ultitude of the right triangle and theresultant strain (E).) be the base. Thus,

(Ty + (Tn Ellu, = 2

where:(Tr material's shear strength(Tll material's ultimate strengthEll strain of the material at point of

ultimate stress

where E = modulus of elasticity.

Since the absorption of energy is actually a volu-metric property, the u in psi = u in in.-Ibsjcu. in.

When impact loading exceeds the elastic limit (oryield strength) of the material, it calls for toughnessin the material rather than resilience. Toughness, theability of the metal to resist fracture under impactloading, is indicated by its ultimate energy resistance( u ll ) . This is a measure of how well the materialabsorbs energy without fracture.

The ultimate energy resistance (ull ) is the totalarea OACD under the stress-strain curve. For practi-cality the following formula can be used:

U=(T2

2E

Since the absorption of energy is actually a volu-metric property, the U ll in psi = u., in in.-Ibsjcu. in.

Tests developed for determining the impactstrength of materials are often misleading in theirresults. Nearly all testing is done with notched speci-mens, in which case it is more accurately the testingfor notch toughness.

The two standard tests are the Izod and Charpy.The two types of specimens used in these tests andthe method of applying the load are shown in Figure 8.Both tests can be made in a universal impact testingmachine. The minimum amount of energy in a fallingpendulum required to fracture the specimen is con-sidered to be a measure of the material's impactstrength. In actuality, test conditions are seldom dupli-cated in the working member and application of thesetest data is unrealistic.

--jI.09z't ...L a315"~ Ia39lEJ--.Lr-2.9fZ"---j n 1-1"394"

FIG. 8 Typical Izod (left) andCharpy (right) impact test speci-mens, methods of holding andof applying the test load. TheV-notch specimens shown havean included angle of 45 and abottom radius of 0.010" in thenotch.

S E C T I O N 2 . 2

P r o p e r t i e s o f S e c t i o n s

M = a r e a o f e l e m e n t m u l t i p l i e d b y t h e d i s t a n c e

( y ) o f e l e m e n t ' s c e n t e r o f g r a v i t y f r o m r e f e r -

e n c e a x i s o f s e c t i o n

T h e m o m e n t s o f t h e v a r i o u s e l e m e n t s a r e t h e n

a l l a d d e d t o g e t h e r . T h i s s u m m a t i o n o f m o m e n t s i s

n e x t d i v i d e d b y t h e t o t a l a r e a ( A ) o f t h e s e c t i o n .

T h i s g i v e s t h e d i s t a n c e ( n ) o f t h e n e u t r a l a x i s f r o m

t h e r e f e r e n c e a x i s , w h i c h i n t h i s c a s e i s t h e b a s e l i n e

o r e x t r e m e f i b e r .

F i n d i n g t h e N e u t r a l A x i s

I n w o r k i n g w i t h t h e s e c t i o n ' s m o m e n t o f i n e r t i a , t h e

n e u t r a l a x i s ( N . A . ) o f t h e s e c t i o n m u s t b e l o c a t e d . I n

a m e m b e r s u b j e c t t o a b e n d i n g l o a d f o r e x a m p l e , t h e

n e u t r a l a x i s e x t e n d s t h r o u g h t h e l e n g t h o f t h e m e m b e r

p a r a l l e l t o t h e m e m b e r ' s s t r u c t u r a l a x i s a n d p e r p e n -

d i c u l a r t o t h e l i n e o f a p p l i e d f o r c e . T h e n e u t r a l a x i s

r e p r e s e n t s z e r o s t r a i n a n d t h e r e f o r e z e r o s t r e s s . F i b e r s

b e t w e e n t h e n e u t r a l a x i s a n d t h e s u r f a c e t o t h e i n s i d e

o f t h e a r c c a u s e d b y d e f l e c t i o n u n d e r l o a d , a r e u n d e r

c o m p r e s s i o n . F i b e r s b e t w e e n t h e n e u t r a l a x i s a n d t h e

s u r f a c e t o t h e o u t s i d e o f t h e a r c c a u s e d b y d e f l e c t i o n

u n d e r l o a d , a r e u n d e r t e n s i o n .

F o r p r a c t i c a l p u r p o s e s t h i s n e u t r a l a x i s i s a s s u m e d

t o h a v e a f i x e d r e l a t i o n s h i p ( n ) t o s o m e r e f e r e n c e a x i s ,

u s u a l l y a l o n g t h e t o p o r b o t t o m o f t h e s e c t i o n . I n

F i g u r e 1 , t h e r e f e r e n c e a x i s i s t a k e n t h r o u g h t h e b a s e

l i n e o f t h e s e c t i o n . T h e t o t a l s e c t i o n i s n e x t b r o k e n

i n t o r e c t a n g u l a r e l e m e n t s . T h e m o m e n t ( M ) o f e a c h

e l e m e n t a b o u t t h e s e c t i o n ' s r e f e r e n c e a x i s , i s d e t e r -

m i n e d :

y ,

N e u h - a l

1 -

n

A x i s

n

j y

B a s e L i n e

2 . 2 - 1

F I G U R E 1

b , - - - - - - - j

f - - - 1 - - - 1 - - - -

t

d

z

J _

Y z .

~

-

I "

T

d ,

. : L

1 1 - - -

y -

1 . I M P O R T A N C E O F S E C T I O N P R O P E R T Y

T h e a r e a ( A ) o f t h e m e m b e r ' s c r o s s - s e c t i o n i s u s e d

d i r e c t l y i n c o m p u t a t i o n s f o r s i m p l e t e n s i o n , c o m p r e s -

s i o n , a n d s h e a r . A r e a ( A ) i s e x p r e s s e d i n s q u a r e i n c h e s .

I f t h e s e c t i o n i s n o t u n i f o r m t h r o u g h o u t t h e l e n g t h

o f t h e m e m b e r , i t i s n e c e s s a r y t o d e t e r m i n e t h e s e c t i o n

i n w h i c h t h e g r e a t e s t u n i t s t r e s s e s w i l l b e i n c u r r e d .

2 . A R E A O F T H E S E C T I O N ( A )

T h e b a s i c f o r m u l a s u s e d i n t h e d e s i g n o f s t r u c t u r a l

m e m b e r s i n c l u d e a s o n e f a c t o r t h e c r i t i c a l p r o p e r t y o f

t h e m a t e r i a l a n d a s a n o t h e r f a c t o r t h e c o r r e s p o n d i n g

c r i t i c a l p r o p e r t y o f t h e m e m b e r ' s c r o s s - s e c t i o n . T h e

p r o p e r t y o f t h e s e c t i o n d i c t a t e s h o w e f f i c i e n t l y t h e

p r o p e r t y o f t h e m a t e r i a l w i l l b e u t i l i z e d .

T h e p r o p e r t y o f s e c t i o n h a v i n g t h e g r e a t e s t i m -

p o r t a n c e i s t h e s e c t i o n ' s a r e a ( A ) . H o w e v e r , m o s t

d e s i g n p r o b l e m s a r e n o t s o s i m p l e t h a t t h e a r e a i s

u s e d d i r e c t l y . I n s t e a d t h e r e i s u s u a l l y a b e n d i n g a s p e c t

t o t h e p r o b l e m a n d , t h e r e f o r e , t h e r i g i d i t y f a c t o r n o r -

m a l l y i s t h e s e c t i o n ' s m o m e n t o f i n e r t i a ( I ) a n d t h e

s i m p l e s t r e n g t h f a c t o r i s t h e s e c t i o n m o d u l u s ( S ) .

A n o t h e r p r o p e r t y o f s e c t i o n t h a t i s ' o f m a j o r i m -

p o r t a n c e i s t h e s e c t i o n ' s t o r s i o n a l r e s i s t a n c e ( R ) , a

m o d i f i e d v a l u e f o r s t a n d a r d s e c t i o n s .

3 . M O M E N T O F I N E R T I A ( I )

W h e r e a s a m o m e n t i s t h e t e n d e n c y t o w a r d r o t a t i o n

a b o u t a n a x i s , t h e m o m e n t o f i n e r t i a o f t h e c r o s s - s e c t i o n

o f a s t r u c t u r a l m e m b e r i s a m e a s u r e o f t h e r e s i s t a n c e t o

r o t a t i o n o f f e r e d b y t h e s e c t i o n ' s g e o m e t r y a n d s i z e .

T h u s , t h e m o m e n t o f i n e r t i a i s a u s e f u l p r o p e r t y i n

s o l v i n g d e s i g n p r o b l e m s w h e r e a b e n d i n g m o m e n t i s

i n v o l v e d .

T h e m o m e n t o f i n e r t i a i s n e e d e d i n s o l v i n g a n y

r i g i d i t y p r o b l e m i n w h i c h t h e m e m b e r i s a b e a m o r

l o n g c o l u m n . I t i s a m e a s u r e o f t h e s t i f f n e s s o f a b e a m .

M o m e n t o f i n e r t i a i s a l s o r e q u i r e d f o r f i g u r i n g t h e v a l u e

o f t h e p o l a r m o m e n t o f i n e r t i a ( J ) , u n l e s s a f o r m u l a i s

a v a i l a b l e f o r f i n d i n g t o r s i o n a l r e s i s t a n c e ( R ) .

T h e m o m e n t o f i n e r t i a ( I ) i s u s e d i n f i n d i n g t h e

s e c t i o n m o d u l u s ( S ) a n d t h u s h a s a r o l e i n s o l v i n g

s i m p l e s t r e n g t h d e s i g n s a s w e l l a s r i g i d i t y d e s i g n s . T h e

m o m e n t o f i n e r t i a o f a s e c t i o n i s e x p r e s s e d i n i n c h e s

r a i s e d t o t h e f o u r t h p o w e r ( i n .

4

) .

2.2-2 / Load & Stress Analysis

lIb b~31 (3)

I Problem 2 IHaving already located the neutral axis of the sectionin Figure 2, the resulting moment of inertia of thesection (detailed further in Fig. 3) about its neutralaxis is found as follows:

width of rectangle, anddepth of rectangle

where bd

6 43 2.83In = ----r2 + (6 . 4 . 7.22 ) + ----r2 +

(2 . 8 . 1.22 ) + 101~43 + (10 . 4 . 4.82 )= 32 + 1244 + 85.3 + 23 + 53.3 + 921.6= 2359 in. 4

Moment of Inertia by Elements (Second Method)In the second method, the whole section is broken intorectangular elements. The neutral axis of the wholesection is first found. Each element has a moment ofinertia about its own centroid or center of gravity(e.C.) equal to that obtained by the formula shownfor rectangular sections. (See Table 1.)

In addition, there is a much greater moment ofinertia for each element because of the distance of itscenter of gravity to the neutral axis of the wholesection. This moment of inertia is equal to the areaof the element multiplied by the distance of its e.C.to the neutral axis squared.

Thus, the moment of inertia of the entire sectionabout its neutral axis equals the summation of the twomoments of inertia of the individual elements.

Finding the Moment of InertiaThere are various methods to select from to get thevalue of moment of inertia (I). Four good methodsare presented here.

lIn ~~31 ............................(2)

6.8"

(4 . 6 . 14) + (2 . 12 . 6) + (4 . 8 . 2)(4 . 6) + (2' 12) + (4' 8)

336 + 44 + 64 544- 24+24+32 80

I IMI sum of all moments ( 1)n - IA or total area .

Thus, the neutral axis is located 6.8" above thereference axis or base line and is parallel to it.

FIGURE 2

I Problem 1The neutral axis of the compound section shown inFigure 2 is located in the following manner:

Moment of Inertia for Typical Sections(First Method)The first method for finding the moment of inertia isto use the simplified formulas given for typical sections.These are shown in Table 1. This method for finding Iis the most appropriate for simple sections that cannot

.be broken down into smaller elements. In using theseformulas, be sure to take the moment of inertia aboutthe correct line. Notice that the moment of inertia fora rectangle about its neutral axis is-

but the moment of inertia for a rectangle about itsbase line is - FIGURE 3

M o m e n t 0 1 I n e r t i a b y A d d i n g A r e a s ( T h i r d M e t h o d )

W i t h t h e t h i r d m e t h o d i t i s p o s s i b l e t o f i g u r e m o m e n t

o f i n e r t i a o f b u i l t - u p s e c t i o n s w i t h o u t f i r s t d i r e c t l y

m a k i n g a c a l c u l a t i o n f o r t h e n e u t r a l a x i s .

T h i s m e t h o d i s r e c o m m e n d e d f o r u s e w i t h b u i l t - u p

g i r d e r s a n d c o l u m n s b e c a u s e t h e d e s i g n e r c a n s t o p

b r i e f l y a s a p l a t e i s a d d e d t o q u i c k l y f i n d t h e n e w

m o m e n t o f i n e r t i a . I f t h i s v a l u e i s n o t h i g h e n o u g h , h e

s i m p l y c o n t i n u e s t o a d d m o r e p l a t e a n d a g a i n c h e c k s

t h i s v a l u e w i t h o u t l o s i n g a n y o f h i s p r e v i o u s c a l c u l a -

t i o n s . L i k e w i s e i f t h e v a l u e i s t o o h i g h , t h e d e s i g n e r

m a y d e d u c t s o m e o f t h e p l a t e s a n d a g a i n c h e c k h i s

r e s u l t . T h i s i s d o n e i n t h e s a m e m a n n e r a s o n e u s i n g

a n a d d i n g m a c h i n e , w h e r e b y y o u c a n s t o p a t a n y t i m e

d u r i n g a d d i n g a n d t a k e a s u b - t o t a l , a n d t h e n p r o c e e d

a l o n g w i t h o u t d i s r u p t i n g t h e p r e v i o u s f i g u r e s .

U s i n g t h e p a r a l l e l a x i s t h e o r e m f o r s h i f t i n g t h e

a x i s f o r a m o m e n t o f i n e r t i a , t h e m o m e n t o f i n e r t i a

o f t h e w h o l e s e c t i o n a b o u t t h e r e f e r e n c e l i n e y - y i s -

I n + A n

2

~ ( 4 )

I

y

A n 2 1 ( 5 )

t o t a l m o m e n t s a b o u t b a s e M

S i n c e n =

t o t a l a r e a

M 2

a n d o f c o u r s e n

2

= A 2

S u b s t i t u t i n g t h i s b a c k i n t o e q u a t i o n ( 5 ) :

N o t e : n e u t r a l a x i s ( n )

h a s d r o p p e d o u t

T h u s :

I I n I

y

- ~ I (6 )

w h e r e :

I n m o m e n t o f i n e r t i a o f w h o l e s e c t i o n a b o u t i t s

n e u t r a l a x i s , n - n

I , s u m o f t h e m o m e n t s o f i n e r t i a o f a l l e l e m e n t s

a b o u t a c o m m o n r e f e r e n c e a x i s , y - y

M s u m o f t h e m o m e n t s o f a l l e l e m e n t s a b o u t

t h e s a m e r e f e r e n c e a x i s , y - y

A t o t a l a r e a , o r s u m o f t h e a r e a s o f a l l e l e m e n t s

o f s e c t i o n

A l t h o u g h I , f o r a n y i n d i v i d u a l e l e m e n t i s e q u a l

t o i t s a r e a ( A ) m u l t i p l i e d b y t h e d i s t a n c e s q u a r e d

f r o m i t s c e n t e r o f g r a v i t y t o t h e r e f e r e n c e a x i s ( y 2 ) ,

P r o p e r t i e s o f S e c t i o n s / 2 . 2 - 3

T A B L E l - P r o p e r t i e s o f S t a n d a r d S e c t i o n s

M o m e n t o f

,

S e c t i o n R o d i u s o f

I n e r t i o

M o d u l u s

G y r o t i o n

I

S

r

I - b - - - . . ,

8

1

b d

J

b d

2

d

-

-

- I

1 2

6

V T 2

r - b - j

_ 0 1

b d

J

b d

2

d

-

-

' , 1 3

3

3

~J

b d

J

b d

2

d

-

-

-

3 6

2 4

V T 8

f--b~

~t

b d

3

b d

2

d

d

-

_ _ l

1 2

1 2

V 6

f . - b

e r

7 I " d '

7 I " d

J

d

-

-

-

6 4

3 2

4

- ( @ f

7 1 "

7 1 " ( D ' - d

4

)

V D 2 + d

2

6 4 ( D 4 _ d

4

)

- - - -

3 2

D 4

{ j

_ . L

7 I "

0 3 b

7 I "

0 2 b

0

-

-

-

4

4

2

~b'1

W

i ~ (0 3 b - c

J d

)

7 I " ( 0 3 b - - ( ; 3 d )

1

oJb~d

-

4 0

0

c b - e - c d

e a c h e l e m e n t h a s i n a d d i t i o n a m o m e n t o f i n e r t i a ( I . . )

a b o u t i t s o w n c e n t e r o f g r a v i t y . T h i s m u s t b e a d d e d

i n i f i t i s l a r g e e n o u g h , a l t h o u g h i n m o s t c a s e s i t m a y

b e n e g l e c t e d :

T h e b e s t w a y t o i l l u s t r a t e t h i s m e t h o d i s t o w o r k

a p r o b l e m .

2.2-4 / Load & Stress Analysis

I Problem 3 I hand column, to be later added in with the sum ofr; Thus,

53.3 in."

bd"r, = 12

10 . 4312

Plate Size Distance y iA=b'd M=Ay I, =Ay2= My bd3

in. 2 in. 3 in.4 I.=~in."

0 10"x4" 2" 40.0 80.0 160.0 53.3 211x8" 8" 16.0 128.0 1024.0 85.3 6"x4" 14" 24.0 336.0 4704.0 32.0

Totol 80.0 544.0 5888.0 170.6

6058

6059 - 3700

M2I, + I g - A

5888 + 170.6 _ (~)2

Usually the value of Ig is small enough that itneed not be considered. In our example, this valueof 53.3 could be considered, although it will not makemuch difference in the final value. The greater thedepth of any element relative to the maximum widthof the section, the more the likelihood of its Ig valuebeing significant.

The table will now be filled out for plates BandC as well:

Base

Plate Size Distance y A=b,d M=A'Y I, = Ay2=My bd3in.2 in.3 in.4 1'=12

in.4

(A 10"x4" 2"( B ) 211x8" 8"(c 611x411 14"

TotoI

FIGURE 4

The base of this section will be used as a referenceaxis, y-y. Every time a plate is added, its dimensionsare put down in table form, along with its distance (y)from the reference axis. No other information is needed.It is suggested that the plate section size be listed aswidth times depth (b X d); that is, its width first anddepth last.

The above table has been filled out with all of thegiven information from the plates. The rest of thecomputations are very quickly done on slide rule orcalculator and placed into the table. Notice how easyand fast each plate is taken care of.

Starting with plate A, 10" is multiplied by 4" togive an area of 40 sq. in. This value is entered intothe table under A. Without resetting the slide rule,this figure for A is multiplied by (distance y) 2" togive 80 inches cubed. This value for the element'smoment is placed under M in the table. Withoutresetting the slide rule, this figure for M is multipliedby (distance y) 2" again to give 160 inches to thefourth power. This value for the element's moment ofinertia about the common reference axis y-y is recordedunder (Iy ) in the table.

If the moment of inertia (Ig ) of the plate aboutits own center of gravity appears to be significant,this value is figured by multiplying the width of theplate by the cube of its depth and dividing by 12.This value for Ig is then placed in the extreme right-

= 2359 in."

M 544and n = A = 80

= 6.8" (up from bottom)

A recommended method of treating M2/ A on theslide rule, is to divide M by A on the rule. Here wehave 544 divided by 80 which gives us 6.~. Thishappens to be the distance of the neutral axis fromthe base reference line. Then without resetting theslide rule, multiply this by 544 again by just slidingthe indicator of the rule down to 544 and read theanswer as 3700. It is often necessary to know theneutral axis, and it can be found without extra work.

[ Problem 4 ITo show a further advantage of this system, assumethat this resulting moment of inertia (2359 in.") is not

P r o p e r t i e s o f S e c t i o n s / 2 . 2 - 5

l a r g e e n o u g h a n d t h e s e c t i o n m u s t b e m a d e l a r g e r .

I n c r e a s i n g t h e p l a t e s i z e a t t h e t o p f r o m 6 " X 4 " t o

8 " X 4 " i s t h e s a m e a s a d d i n g a 2 " X 4 " a r e a t o t h e

a l r e a d y e x i s t i n g s e c t i o n . S e e F i g u r e 5 . T h e p r e v i o u s

c o l u m n t o t a l s a r e c a r r i e d f o r w a r d , a n d p r o p e r t i e s o f

o n l y t h e a d d e d a r e a n e e d t o b e e n t e r e d . I n i s t h e n

s o l v e d , u s i n g t h e c o r r e c t e d t o t a l s .

i t w i l l s i m p l i f y h i s c o m p u t a t i o n s .

T h e c l o s e r t h e r e f e r e n c e a x i s ( y - y ) i s t o t h e f i n a l

n e u t r a l a x i s ( N . A . ) , t h e s m a l l e r w i l l b e t h e v a l u e s o f

( I

y

a n d I

g

) a n d M 2 I A . H e n c e , t h e m o r e a c c u r a t e t h e s e

v a l u e s w i l l b e i f a s l i d e r u l e i s u s e d .

I f t h e r e f e r e n c e a x i s ( y - y ) i s p o s i t i o n e d t o l i e

t h r o u g h t h e c e n t e r o f g r a v i t y ( e . C . ) o f o n e o f t h e

e l e m e n t s ( t h e w e b , f o r e x a m p l e ) , t h i s e l i m i n a t e s a n y

s u b s e q u e n t w o r k o n t h i s p a r t i c u l a r e l e m e n t s i n c e y = 0

f o r t h i s e l e m e n t .

I f t h e r e f e r e n c e a x i s ( y - y ) i s p o s i t i o n e d a l o n g t h e

b a s e o f t h e w h o l e s e c t i o n , t h e d i s t a n c e o f t h e n e u t r a l

a x i s ( n = M I A ) f r o m t h e r e f e r e n c e a x i s ( y - y ) t h e n

a u t o m a t i c a l l y b e c o m e s t h e d i s t a n c e ( C b ) f r o m t h e

n e u t r a l a x i s t o t h e o u t e r f i b e r a t t h e b o t t o m .

T h e f o l l o w i n g p r o b l e m i l l u s t r a t e s t h e s e p o i n t s .

P r o b l e m 5

F I G U R E 5

M 2

I n = r , + I I I A

= 7 6 3 7 _ (~)2

2 7 4 7 i n . "

P l a t e

S i z e

D i s t a n c e y

i A = b d

M = A y

I , = A y 2 = M y

b d

3

i n .

2

i n .

3

i n .

4

1 = 1 2

i n .

4

P r e v i o u s S e c t i o n

- - 8 0 . 0

5 4 4 . 0 5 8 8 8 . 0 1 7 0 . 6

N e w 0

2 1 /

x 4

1 J

1 4 "

8 . 0 1 1 2 . 0

1 5 6 8 . 0 1 0 . 6

T o t a l

8 8 . 0

6 5 6 . 0

7 4 5 6 . 0 1 8 1 . 2

7 6 3 7

y R e f . p l a n e

y - -

N A r

1 7 . 0 "

C b = 1 7 . 0 7 5 " I

Jt~#~~CGOf'

I . . . 1 6 " ~ 1

F I G U R E 6

M 6 5 6

A 8 8

7 . 4 5 " ( u p f r o m b o t t o m )

a n d n =

I t i s v e r y e a s y t o i n c o r p o r a t e a r o l l e d s e c t i o n i n t o a

b u i l t - u p m e m b e r , f o r e x a m p l e t h i s p r o p o s e d c o l u m n t o

r e s i s t w i n d m o m e n t s . S e e F i g u r e 6 . F i n d t h e m o m e n t

o f i n e r t i a o f t h e w h o l e s e c t i o n a b o u t i t s n e u t r a l a x i s

( I n ) a n d t h e n f i n d i t s s e c t i o n m o d u l u s ( S ) .

C h o o s i n g