Match shear welds and shear rupture AISC 2

So, there are two ways a weld connection fails.
1) The weld itself fails.
2) The weld is sufficiently strong, but the base material it is connected to is not strong enough and ruptures.

What this paragraph is saying is that it can be difficult to predict #2 precisely for some weld arrangements. Therefore, they take a shortcut and look at the rupture strength of the base material and what thickness it would take for it to match the weld strength. If the actual thickness of the base material is too small then they will say that the base material doesn't work....

Thanks for your answer JoshPlum, it really helped a lot!! I have another doubt and i would appreciate your help again.

In first lines of paragraph say that the strength of a connecting element can be evaluated directly, for example, the wall of a HSS subject a tensile force.

My doubt is this: why in this case it is possible to evaluate the strength of base metal but it is not possible in a beam web? What is the difference?

Thanks again!!

You might want to check out the following (very brief) article by Carlo Lini of AISC's Steel Solution's Center.

Thanks JoshPlum. I just read the document and it was very interesting to me. I must recognize i didn't understand the contraction issue in welds but my doubts were disiped. if you have other documents about metalic structures that could share with me, i would be very grateful. I would like to have your mail. Thanks again.