Strength of Transverse Fillet Welded Joints

65 downloads 18580 Views 401KB Size Report
Strength of Transverse Fillet Welded Joints. Analysis yields a design formula that is more rational than the method ..... Standard for Steel Tanks, Standard Pipes,.
Strength of Transverse Fillet Welded Joints Analysis yields a design formula that is more rational than the method of treating all fillets as though loaded in the weakest direction

BY BEN KATO A N D KOJI M O R I T A

SUMMARY. The resultant force on a fillet w e l d may be transverse to t h e axis of the w e l d , inclined to the axis or parallel to the axis. The stress distribution in the w e l d and its static resistance vary materially w i t h the relative orientation of load and w e l d axis. Most of the basic investigations o n the static strength and behavior of f i l let w e l d s w e r e conducted during 1920's and 1930's (Ref. 1). It has been s h o w n that breaking loads for transversely-loaded fillets w e r e of the order of 4 0 % greater t h a n those for longitudinally-loaded fillets of the same size and length. In this paper the term transverse fillet w i l l be used to describe the former, w h i l e longitudinal fillet w i l l be used for the latter. A f e w design specifications (e.g., Ref. 2) and design methods take these differences into account, but most do not, treating all fillet w e l d s as though oriented in the weakest direction. The main reasons for neglecting the greater strength of transverse fillet w e l d s are probably an interest in simplifying design and

the fact that the performance of a transverse fillet w e l d is complex. Recently, in recognition of the remarkable improvement in quality of steel, electrode and w e l d i n g t e c h niques, extensive investigations on fillet w e l d e d joints w e r e conducted to obtain more rational design formulas (Refs. 3 , 4 ) . Regardless of w h e t h e r or not one distinguishes between the different types of fillet w e l d loads in design, it is desirable to make a study of their performance. It should aid in assessing the true effectiveness of connections proportioned by conventional methods. In this report, the static strength and behavior of transverse fillet w e l d s are studied theoretically. A n approximate solution based on the theory of elasticity is reviewed and supplemented by an elastic-plasticstrain hardening analysis performed numerically using the finite element technique. The results are compared w i t h available test results. An Approximate Approach from t h e T h e o r y of Elasticity

BEN KATO is Professor and KOJI MORITA is Assistant Professor in the Faculty of Engineering, Department of Architecture, University of Tokyo, Tokyo, Japan.

A n approximate theory on the strength of transverse fillet w e l d s w a s presented by a senior writer (Ref.

5), based on the following assumptions:: 1. The direct stress (q) on the tensile face of the w e l d is uniformly distributed (Fig. 1). 2. The pattern of the elastic stress distribution remains unchanged until the breaking of t h e w e l d . 3. Breaking w i l l occur w h e n the shear stress at a point of the fillet reaches "Cmax.= /£

w h e r e electrode R-type(a) electrode

33.22

56.25

32.4

34.30

55.17

37.4

S5 B S10B S15B S20B S30B S40B S5 R S15R S40R

44.88 44.39 44.59 47.04 47.04 47.04 46.35 44.59 45.77

57.62 58.80 58.31 59.49 59.49 59.49 56.35 54.19 54.59

21.0 21.0 21.7 19.3 19.3 19.3 17.5 18.5 16.4

FEBRUARY

\\

ty

s^v

\ \

\\\\v

§H

x/8

R Fig. 6—Shear stress distribution by Eq.(10)

{a) B = basic; R = rutile

62-s

%

1974

nitudes are given irrespective of their orientation.a x ,

Start) fpata Input I ] Print



Subroutine

Input

InputJjataJ

Setup Overall Matrix KT

Subroutine D£M(Calculate D* ) Subroutine DPM (Calculate D* ) •Subroutine QSRM (Calculate element stiffness matrix K e ( e m superpose K elem. o n K i )

Stiffness

4_ Setup Load Vector F. M o d i f y KT by Support I Condition

T

Solve Stiffness Equation! KT-**

Calculate

= F

Subroutine

SOLVE

Subroutine

LDINCR

Subroutine

PRINT

A£ . a