I've looked and looked for an engineering definition of a "cyclic load", particularly as it applies to the AWS D1.1 Structural Welding Code. I know that cyclic loading basically means loads recurring in cycles, and I know that structural steel subjected to cyclic loading have more restrictions in the code than structural steel subjected to static loading. I guess that's primarily due to the repeated shock that's being imposed on the welds.
Older editions of D1.1 (example, my 1980) had provisions applying exclusively to buildings (static loading), and bridges (dynamic loading), but later versions referred to static and cyclic, with no mention of bridges, since a bridge code exists. (Anyone know when the first D1.5 was released?)
My take is that most of the structural buildings we fabricate are probably statically loaded, but I don't really know that. To help me understand, can anyone give any examples of cyclically loaded buildings? Would a building with crane systems be cyclic? Would the fatigue category determine cyclic or static? Any comment would be appreciated.
The foreword of D1.5 gives a comprehensive historical timeline, but the first bridge code was published in 1988.
I don't typically think of buildings as either static or cyclic buildings, but rather understand that while nearly all structures are generally static they may have some components or members subjected to cyclic loads. It is the responsibility of the EOR to identify those components or those members which are subjected to cyclic loads and our job is to apply the D1.1 code's cyclic requirements to just those members.
If fatigue is brought up then you can assume it is a cyclic situation. If cyclic is mentioned then you should also be checking fatigue requirements. If the situation is limited to static loads then fatigue is not a concern. Cyclic and fatigue go hand-in-hand.
The fatigue tables in D1.1 start at 10,000 cycles.
Best regards - Al
Good information Al, where did you get it?
From figure 2.1.
Best regards - Al
Referenced should have been to Figure 2.11, I think.
So by the same logic the fatigue tables stop at 100,000,000 cycles?
I think we can extrapolate at both ends if necessary, the table is just a graphically plot of the requirements in Table 2.4. I think the ranges were selected to be wide enough to show the break in the the F(x).
You're right, it was 2.11.
I'm going to blame it on my Apple MacBook Pro. It is without a doubt the worst computer I've ever owned.
I have to proof read every line because the keyboard skips letters and numbers. It drives me nuts. Even the MicroSoft Office for Mac doesn't translate all my existing MSWord and PowerPoint files. Anything with an embedded photo or graphic is going to have serious problems. A lot of software available for PCs is not availble for the Mac. They don't even make a docking station for it. I have cables coming and going everywhere.
I haven't had it for a full month, but I could purchase a few PC laptops for the lost productivity I've had with this machine, no, make that "TOY". I refuse to call it a computer any longer. It definately is not buines machine.
Excuse me, I have to go on-line to find a real computer to replace this door stop.
Best regards - Al
If you are trying to identify statically loaded vs. cyclically loaded welds for the purpose of acceptance criteria, the "Engineer" is supposed to identify that for you (either in drawings or specifications). See paragraph 1.4.1 (6):
"1.4.1 Engineer's Responsibilities. The Engineer shall
be responsible for the development of the contract documents
that govern products or structural assemblies produced
under this code. The Engineer may add to, delete
from, or otherwise modify, the requirements of this code
to meet the particular requirements of a specific structure.
All requirements that modify this code shall be incorporated
into contract documents. The Engineer shall
determine the suitability of all joint details to be used in a
welded assembly.
The Engineer shall specify in contract documents, as
necessary, and as applicable, the following:
(1) ...
(6) For nontubular applications, whether the structure
is statically or cyclically loaded."
I agree that the EOR should identify this in the job specifications, but I've never seen anything in a spec on any job that states whether the structure is to be subjected to either static or cyclic loads. That's what's so frustrating. All I've ever seen is that welding is to be in accordance with AWS D1.1 Structural Welding Code, which with all things considered, is a pretty broad statement. A couple things come to mind immediately. Backing issues (5.10.4, 5.10.4.1), and if holes are to be plugged, do we use our WPS or do we have to get approval from the EOR (5.26.5). I always have to go through the process of asking these questions when it would be so much easier for static or cyclic to be indicated in the contract documents. End of gripe.
we have a customer that lists it as an extension of the welding symbol. the second line lists the aws joint designation TC-U4b-GF, and the third line lists 100% UT (cyclic)
Topic American Welding Society Services / Technical Standards & Publications / Cyclic and Static Loading
