Weld Group Design Using AISC Equation J2-5 2

[sekwahrovert]

When calculating Fw, AISC 360-05 Eq. J2-5 results in a higher value than Table J2.5 for fillet welds. As I understand it, the higher value reflects the fact that a weld is stronger when loaded transverse to the weld axis as opposed to being loaded in the direction of the weld axis. According to section J2.4, Eq. J2-5 can only be used for a "linear weld group loaded in-plane." A linear weld group is defined as "one in which all elements are in a line or are parallel." I can imagine many scenarios in which a fillet weld is loaded transverse to its own axis, but few scenarios in which a linear weld group is loaded in plane. For example, if the fixed end of a cantilevered pipe is welded to a flat plate and a load is applied to the other end of the pipe creating a bending moment in the pipe, then any segment of the circular weld would be loaded almost entirely transverse to its axis. However, the weld group does not fit the description of a linear weld group and it is not loaded in-plane. Is there any way to justify the use of Eq. J2-5 for the weld group just described? I have attached a typical detail illustrating the welded connection I am asking about.

 

[WillisV]

thread725-262656

 

[dik]

A couple of comments on the detail:

You might want to include the fillet weld size in the schedule so that it can be increased for larger dia. pipe columns.

You may want to frame the slab into the concrete blockout and use a flexcel joint around it with a granular fill buffer between the soffit of the slab and the top of the footing.

You may want to use headed anchor rods instead of the 'L' bolts shown.

Dik

 

[sekwahrovert]

Thanks to you, WillisV, for directing me to the previous post. I also asked AISC my question and received this response:

A couple of changes related to this provision have been made in the 2010 Specification. First, we clarified that Sections J2.4.(a) and J2.4.(c) can only be used with welds of uniform leg size. This was always the intent but needed to be clarified. In most instances, but not all, the leg sizes will be uniform. The second change is more substantial and related to your question. We removed the requirement that the load must be in-plane. This change was based on testing that indicated there was sufficient ductility to justify using the strength increase for transverse loads as well.

In practice the in-plane restriction was often overlooked. In fact if you look back through the Manuals, the 13th Ed. included, you will find that the eccentrically loaded weld group tables in Part 8 included cases with out-of-plane loads and incorporated the directional strength increase. Now out-of-plane loads are not prohibited, which brings the Manual, common practice and the Specification into accord.

Additionally it should be recognized that Sections J2.4.(a) and J2.4.(c) are only special cases of the approach reflected in Section J2.4.(b) which can be applied over a wide range of geometries and even for weld groups consisting of elements of non-uniform leg sizes.

J2.4.(a) could likely be applied to you condition by recognizing (by inspection) that compatibility among the weld elements is not an issue, since all elements will presumably be loaded in a similar way. Alternatively Section J2.4.(c) could be applied to more rigorously satisfy the intent of the Specification.​

Thanks to you, dik, for looking at the detail I attached. While I wasn't really looking for detailing advice, I appreciate your insight and will take it into consideration.