Welding Acceptance Criteria Statically or Cyclically Loaded Structures

[Chappie]

With regard to specifying weld acceptance criteria in AWS D1.1 you need to determine whether the structure is statically loaded or cyclically loaded...Does anyone know how exactly it is determined whether a structure is statically or cyclically loaded?

For a building for example, standard office floor loads I would say are static, and wind loads are probably also considered static - since that's how we usually design for them. Can wind ever be considered as a cyclic load?

Many thanks!

 

[Ron]

Under AWS, the division is generally buildings (static) or bridges (cyclic/fracture critical). Building loads,though sometimes cyclic in nature, do not have the frequency of loading to be considered cyclic with respect to fracture criticality or fatigue influence. There are some localized exceptions, but that is the general breakdown.

 

[ishvaaag]

Where wind is the main load, such in boards over highways, advertising panes, poles for lighting or traffic lights, wind better is considered as a dynamic force. It breaks on fatigue bolts, baseplates, and welds.

Not far from this are the many times underdesigned respect lateral stiffness industrial buildings, where it also would be soud to safeguard against the same effects.

Also, anywhere that we use high pressure or suction forces, connections be better designed for that "overexposure situation" where many times cladding or waterproofing elements are thrown off their junctions by the strong winds.

There are many other situations where the dynamical aspects of wind need be considered, mainly highrise, detail, and less mid-rise.

 

[InDepth]

Take a look at AISC's "A Fatigue primer for structural engineers (free if you are an AISC member). I believe they cite criteria for determining high cycle fatigue limits, and when connections need special detailing.

http://www.aisc.org/store/p-1590-a-fatigue-primer-for-structural-engineers.aspx

You may also want to look at the Blodgett books.


For low cycle fatigue in seismic regions, its kind of left to the AWS D1.8 code.

 

[HgTX]

@Ron: building/bridge is D1.1 vs. D1.5. However, that doesn't account for the static/cyclic distinction within D1.1.

Hg

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