Balanced Welds for Truss Members

[jike]

Although I mainly deal with buildings and static loads, I recall the need to use balanced welds (about the member centroid) for truss connections that have repetitive loading (such as vehicles). I see this also referenced in Ex. 17, Appendix K, AISC 9th Edition. I assume the stress level recommended is only for the repetitive live load and that the static dead load does not need to be included in this stress level.

Generally fabricated joists or joist girders with double angle web members do not have balanced welds since their intended use is for static loads only. Is there a reference on how to analyze the connections that do not have balanced welds?

 

[nutte]

If you use unbalanced welds, the weld group is eccentric to the neutral axis of the angle. This is because the centroid of the weld gorup does not fall on the neutral axis of the angle.

If you only have static loads, you are allowed to neglect this eccentricity and design the weld as if it were concentric.

If you have dynamic loads, you must account for this eccentricity. Luckily there are tables showing the strengths of welds under eccentric load.

 

[abusementpark]

If you only have static loads, you are allowed to neglect this eccentricity and design the weld as if it were concentric.

Per who??

 

[nutte]

Per AISC, based on its negligible effect and historical success with connections of these types. In the 2005 specification, it's in section J1.7.