Allowable stress for fillet welds

[hrm]

we have to design connections according to AISC-ASD with European sections. Is it possible that the allowable stress for fillet welds equals 14.4 ksi, base material A36, E70xx electrodes?
Is this value for leg size or effective throat size?
(what reason has the limitation of shear capacity of weld to 0.4xFy of base material? Is this the relation to the connected area of weld to base material?)
I have found in an example for moment connection with end plates (8th edition of AISC-Manual) values for fillet welds 21 ksi (A36 base material), 22 ksi for full penetration welds (A36 base material) and 30 ksi for full penetration welds (A50).
Is no increase for allowable fillet weld stress possible by using base material A50?
Thank you for your support.

 

[dooron]

A good reference for weld design is O.Blodgett. I think you check the throat area for weld shear strength. Fillet welds, without any preparation may also cause a stress concentration on the inside corner, therefore careful look if there is any cyclic loads, the allowable stress level in these applications may go to 1/10 the ultimate.

 

[jgrek]

I will address the .40 x(Yield Strength)

Recall Von Mises stresses and material strengths when loaded in shear Yield strength in shear is taken as 58% (AISC uses 60%) of Normal direction yield. Combined with ASD Allowable Stress of 2/3 Yield you get:
.60 x.6667 = .400

I believe AISC uses the Effective Throat Width for calculating weld areas.

Fatigue can further lower the allowable.

 

[hrm]

Thanks for all your replies.
It is very strange for me that the allowable stress has such a low value because in 'old' (= ASD) German Standards the value for allowable stress was 13,5 kN/cm² (~19 kips).
In our 'new'(=LRFD) Standard (DIN 18800) the value for fillet weld stress is about 86% of the yield stress of base material (using S235 ~ A36).

Thank you for your support.

 

[hrm]

sorry, there's a mistake in my reply above:
13,5 kN/cm² equals about 19 ksi, not 19 kips.