AWS D1.8 Seismic Supplement

Date 08-23-2007 16:20

I've been reading this forum for a few months and am extremely impressed by the level of knowledge and dedication to producing quality products displayed by the posters. At times it's even a bit humorous!
Our company is preparing to bid on a structure (ethanol plant) with seismic elements associated with it. We bought a D1.8 Seismic Supplement, and 6.3.2 states that the diffusible hydrogen levels of our electrodes & electrode/flux combinations shall meet the requirements for H16. Now, for fracture critical work, these things must meet the requirements for H8. The question: If the electrodes & electrode/flux combinations meet the requirements for H8, do they then also meet the requirements for H16? The definition of the diffusible hydrogen number is "X mL maximum diffusible hydrogen per 100 grams (of) deposited weld metal". Am I correct in assuming (I hate that word) that the electrodes and electrode/flux combinations that we use for FC projects will meet the requirements for a seismic project?

Dan

By js55

Date 08-23-2007 19:32

Dan,
"If the electrodes & electrode/flux combinations meet the requirements for H8, do they then also meet the requirements for H16?"...........Yes, 8 ml will of course be less than 16 ml and would therefore exceed the H16 requirement.

And I haven't read D1.8 yet but if thats the language I'm surprised. It seems the language should have stated something along the lines of equal or exceed, or minimum or something of greater clarity. But then if they made it too clear we wouldn't need consultants. OK, thats my sarcasm for the day.

"Am I correct in assuming (I hate that word) that the electrodes and electrode/flux combinations that we use for FC projects will meet the requirements for a seismic project."........Yes......As long as the diffusable hydrogen desginator of the fillers you have equals or exceeds the requirement.
All of course in my opinion.

By G.S.Crisi (****)

Date 08-23-2007 19:35

A word of warning from one who's erected an oil refinery in a Class 4 seismic area (the one in which the worst earthquakes on earth can happen).
The whole steel structure, including its concrete foundations, must be anti-seismic, not just the welds. AISC must have some written material on that.
Giovanni S. Crisi
Sao Paulo - Brazil

By Bob Garner (***)

Date 08-28-2007 21:07

AISC publishes the Seismic Design Manual for structural steel in seismic areas but that document essentially covers design of the structure. The engineers should have used this document in the design of the structure so that should "take care of it". There are some CVN requirements, etc. in the Seismic Design Manual but I believe all the seismic weld requirements are better covered in the AWS document. The Seismic Design Manual does require that demand-critical welds be identified so that should tell you which welds need to be seismic quality. It also covers some QA/QC issues also.

I haven't seen where engineers have been identifying demand-critical welds on the design drawings I've seen, so I think they need to get up to speed on this.

Bob