Structure in Canada
Structure in Canada
(OP)
We're bidding on structures in Canada that will be fabricated in the U.S. so we will be using U.S. procured steel such as ASTM A36, A992, and A500 Gr B. The minimum temperature at the site is -45C. These will be unheated, sometimes open structures (think pipe racks). I'm concerned these steels won't be suitable for this low of a temperature, so my first questions is have these steels been used successfully at this temperature? Are there supplements we should specify to make them suitable? If we bought steel that met Canadian specs. (whatever is equivalent to ASTM) would that simplify things since I presume low temperature is just a given up there? Are there other structural steels for wide flanges and HSS sections available in the U.S. that would be more suitable?
I know it's a lot of questions. I'm just trying to foresee some options. Thanks.
I know it's a lot of questions. I'm just trying to foresee some options. Thanks.






RE: Structure in Canada
That being said. We often find ourselves using US designated steel due to availability. I cannot see the change in grade being a huge deal as long as the designer is aware prior to fabrication.
We for standard rolled shapes we use 350W steel yield strength 350 MPa, Ultimate strength 450 MPa.
If your designer has accounted for the major temperature swings then I cannot see you having any problems.
RE: Structure in Canada
It depends what your loading looks like. For outdoor industrial structures we'll often use standard grade steel, but you start to see these steels acting in a much more brittle way when you start drifting a bit below freezing. This isn't wonderful in normal service but it becomes critical in fatigue and impact scenarios. Your fatigue service life with normal grade steel drops significantly once you get into these temperature ranges and you run the risk of a brittle fracture under impact loads.
So at a minimum, I'd normally specify a 350WT or other WT grade steel for critical areas of structures that see this kind of loading (including lifting lugs and maybe other members that could see an impact high in their stress range during lifting). It ensures you don't have a material that will see a brittle fracture in cold conditions. Some owners actually have specifications that call for this in all outdoor structures that see below a certain temperature, but that's somewhat rare in my experience.
So depending on whether you're planning on seeing a lot of vibration, or if you've got transient loads you're restraining, or have other similar load conditions there may be areas you want to consider this failure mechanism and maybe look at alternate materials.
Basically, it's a steel that has the normal requirements for a weldable grade structural steel with additional charpy impact test requirements.
RE: Structure in Canada
Dik
RE: Structure in Canada
http://files.engineering.com/getfile.aspx?folder=5...
RE: Structure in Canada
Thanks for the answers so far. Very helpful. I'm still curious about using steel that conforms to US standards. Anybody use that in Canada?
RE: Structure in Canada
http://en.wikipedia.org/wiki/U.S._state_temperatur...
Note that many record low temperature are below -45C, so there should be some US standards that cover this.
It is not unheard of in Canada to use ASTM to specify material. I think the fabricator should be able to determine which are equivalent.
I'm not familiar with the US codes, but I suspect the difference in final design would be minor/subtle if you did two different designs with the Canadian vs US codes/standards...maybe someone who uses both codes on a regular basis could comment on that.
RE: Structure in Canada
RE: Structure in Canada
Also, be careful at interfaces where some things are done in the American shop and some are done at the Canadian site. Also, check your contract with the owner and any design specs they have. They may have specs that require Canadian certifications for various things, which could get you into trouble. Remember that if you're doing things like site welding you'll be using Canadian welders with Canadian certifications and materials. If you're doing concrete foundations are you using Canadian or American steel?
On an unrelated note, watch that you leave space for thermal expansion on pipe racks up there. The swing in temperature over the year is easily -40 to +35 Celcius and then unpainted steel can heat up an extra 10 to 15 degrees no problem.