Welding On Unstiffened Flange

Figure 4.7: Calculation of weld forces for intermittent welds

4.10 Connections to unstiffened flanges

(1) Where a transverse plate (or beam flange) is welded to a supporting unstiffened flange of an I, H or other section, see Figure 4.8, and provided that the condition given in 4.10(3) is met, the applied force perpendicular to the unstiffened flange should not exceed any of the relevant design resistances as follows:

- that of the web of the supporting member of I or H sections as given in 6.2.6.2 or 6.2.6.3 as appropriate,

- those for a transverse plate on a RHS member as given in Table 7.13,

- that of the supporting flange as given by formula (6.20) in 6.2.6.4.3(1) calculated assuming the applied force is concentrated over an effective width, beff, of the flange as given in 4.10(2) or 4.10(4) as relevant."

Figure 4.8: Effective width of an unstiffened T-joint

(2) For an unstiffened I or H section the effective width beff should be obtained from:

where:

/yf is the yield strength of the flange of the I or H section; fyp is the yield strength of the plate welded to the I or H section.

The dimension s should be obtained from:

(3) For an unstiffened flange of an I or H section , the following criterion should be satisfied:

where:

fup is the ultimate strength of the plate welded to the I or H section. bp is the width of the plate welded to the I or H section.

Otherwise the joint should be stiffened.

(4) For other sections such as box sections or channel sections where the width of the connected plate is similar to the width of the flange, the effective width beff should be obtained from:

beff = 2tw + 5tf but beff <2tw + 5 ktf ... (4.8)

NOTE: For hollow sections, see Table 7.13.

(5) Even if beff < bp, the welds connecting the plate to the flange need to be designed to transmit the design resistance of the plate bp !\>f[ \> / 7mo assuming a uniform stress distribution.

4.11 Long joints

(1) In lap joints the design resistance of a fillet weld should be reduced by multiplying it by a reduction factor /?LW to allow for the effects of non-uniform distribution of stress along its length.

(2) The provisions given in 4.11 do not apply when the stress distribution along the weld corresponds to the stress distribution in the adjacent base metal, as, for example, in the case of a weld connecting the flange and the web of a plate girder.

(3) Generally in lap joints longer than 150a the reduction factor ft\ v, should be taken as p\ vv. i given by:

l = 1,2 - 0,2Zj /(150a) but y9Lw l < 1,0 ... (4.9) where:

Lj is the overall length of the lap in the direction of the force transfer.

(4) For fillet welds longer than 1,7 metres connecting transverse stiffeners in plated members, the reduction factor ft\ v, may be taken as p\-,,2 given by:

A,w.2= 1,1 -Zw/17 but /?lw.z<1,0 and ^Lw 2 > 0,6 ...(4.10) where:

Lw is the length of the weld (in metres).

4.12 Eccentrically loaded single fillet or single-sided partial penetration butt welds

(1) Local eccentricity should be avoided whenever it is possible.

(2) Local eccentricity (relative to the line of action of the force to be resisted) should be taken into account in the following cases:

- Where a bending moment transmitted about the longitudinal axis of the weld produces tension at the root of the weld, see Figure 4.9(a);

- Where a tensile force transmitted perpendicular to the longitudinal axis of the weld produces a bending moment, resulting in a tension force at the root of the weld, see Figure 4.9(b).

(3) Local eccentricity need not be taken into account if a weld is used as part of a weld group around the perimeter of a structural hollow section.

(a) Bending moment produces tension at the (b) Tensile force produces tension at the root of root of the weld the weld

Figure 4.9: Single fillet welds and single-sided partial penetration butt welds

4.13 Angles connected by one leg

(1) In angles connected by one leg, the eccentricity of welded lap joint end connections may be allowed for by adopting an effective cross-sectional area and then treating the member as concentrically loaded.

(2) For an equal-leg angle, or an unequal-leg angle connected by its larger leg, the effective area may be taken as equal to the gross area.

(3) For an unequal-leg angle connected by its smaller leg, the effective area should be taken as equal to the gross cross-sectional area of an equivalent equal-leg angle of leg size equal to that of the smaller leg, when determining the design resistance of the cross-section, see EN 1993-1-1. However when determining the design buckling resistance of a compression member, see EN 1993-1-1, the actual gross cross-sectional area should be used.

4.14 Welding in cold-formed zones

(1) Welding may be carried out within a length 5t either side of a cold-formed zone, see Table 4.2, provided that one of the following conditions is fulfilled:

- the cold-formed zones are normalized after cold-forming but before welding;

- the r/i-ratio satisfy the relevant value obtained from Table 4.2.

Table 4.2: Conditions for welding cold-formed zones and adjacent material

r/t

Strain due to cold forming (%)

Maximum thickness (mm)

Generally

Fully killed Aluminium-killed steel (Al > 0,02 %)

Predominantly static loading

Where fatigue predominates

> 2,0 >1,5 >1,0

>2 >5 > 14 >20 >25 >33

any any 24 12 8 4

any 16 12 10 8 4

any any 24 12 10 6

0 -1

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