I don't have my steel book near me but I'm pretty sure they are the same. It's just aashto's designation/equivalent. The A709 is included since it requires the charpy test where as A588 doesn't.
They are the same. Word for word, except for whether metric or English units are primary. The only potential difference is that AASHTO M 270 follows the changes in ASTM A 709, and AASHTO ballots once a year while ASTM ballots whenever they feel like it, so M 270 might be a version or two behind A 709. Also since AASHTO uses the same words but doesn't directly republish the document, there is always the possibility that the person who edits the M 270 document might introduce some typos when transcribing the changes made by ASTM.
(Can you tell I am not a fan of M 270? I tried for years to get them to just get rid of it and go direct to ASTM A 709, but turf is turf.)
Until a few years ago, the words were not exactly the same, but the meaning was the same. The common misperception was that ASTM did not specify Charpy testing while AASHTO did, and perhaps this is still the misperception, but it was not correct then and it is not correct now. The reason for the misperception was that AASHTO put the requirement in the body of the spec ("For tension members, specify Supplemental Requirement S83") whereas ASTM put it in the supplemental requirement itself ("this supplemental requirement shall apply to tension members"). Then people got tired of the confusion and changed the specs so they were both the same. And they will remain the same until the AASHTO committee goes back to being lazy about keeping up with ASTM and then M 270 will be two years behind A 709 again.
Thanks for the responses. I've heard the misperceptions in the past and vaguely recall reading that the AASHTO M270 was "prequalified" for charpy and weldability while the ASTM A709 was not??? However, everytime you see a reference to bridge structural steel, you'll see AASHTO M270/ASTM A709 which to me means they are one in the same.
