Weld Group Analysis

[joro]

Hello,

I am writing in hopes of acquiring information on the analysis of a groove & fillet weld group.

Here is my question:

In analyzing a groove weld "capped" with a fillet weld how is the strength of the weld determined. More specifically, how is the effective throat measured? Is it the penetration depth of the groove weld plus .707 * the leg of the fillet?

Also, is the allowable shear stress the smallest of .3 x ultimate strength of the filler material or would if be .4 x base metal yield strength per AWS code?

Any guidance would be greatly appreciated.

Thanks
Joe

 

[welding1]

The answer depends on how the joint is to be loaded. Normally you would consider the smallest cross section as the weakest point. Fillet welds are idealised as perfect triangles; the leg length should be reduced to allow for concavity and the throat decreases to allow for convexity.

The design stress would depend upon the design code you were using; 2/3 of yield is common design stress. It also depends on what confidence you have in the quality of the weld, the consequence of its failure and how accurately you have predicted its loading.

I have a lot of information on calculating the strength of fillet welds on my site

http://www.gowelding.com

which you may find useful.

 

[welding1]

Oops I forgot,

From Mohrs Circle
Maximum Shear stress = Yield Stress / 2

Most codes seem to use:- Design Stress / 2

 

[joro]

Welding1,

Thanks for our response.

I should have stated that the weld group is subject to a parallel load (shear). The weld joint is a 15" diameter bushing approximately 9" long being welded to a 24” OD flange 2” thick.

I also have no problem analysis the welds independently. What I need is information on analyzing the combined effects of the groove & fillet weld.

Thanks
Joe

 

[welding1]

The path of any failure will usually take the shortest route. It is therefore prudent to analyse all possible failure routes, and mechanisms. The fillet weld of a compound weld seldom carries any load, it is usually done to smooth out the notch effect of the corner.

The shear failure will probably pass though the toe of the fillet weld on the thinnest part.