huangyhg

50 ksi w-shapes
i am working on an existing structure with no structural drawings to be found on file.
what year did 50 ksi steel w-shapes become widely accessible and required? also, does anyone know of a cheap standard test that can determine if an in-place w-shape is 36 or 50 ksi?
thank you,
mlm
find a job or post a job opening
my guideline is pre-mid 1990's use 36 ksi, post-mid 1990's use 50 ksi. don't know of any non-destructive test you can do to determine the grade.
agree with arlord.
do you know the year the building was built? if it was built before 1994, i would definately assume 36 ksi. if it was built in 2000 or later, i would assume 50 ksi. if between 1994 and 2000, it might be either, but i would assume 36 ksi to be safe.
i do not know of a non-destructive test for this either, but if you really want to know, there are surely places on a building you can take a sample cuopon of material from and test it. places might be flanges at ends of beam where the moment capacity is not longer required, very tops of column flanges above the last framed in roof
p.s.
a co-worker just handed me a print out from the steel solution center. it states that 1997 was the year aisc released 'technical bulletin no. 3' which provided the requirements for astm a572 grade 50 steel. the effect of the bulletion was ' to create an early version of astm a992, which was released in 2000'.
on occasion, i have seen the size and grade stamped on the
lkjh345, a572 grade 50 was widely used before 1997. the technical bulletin you are referring to only provided supplementary requirements (for use in special moment frames after the northridge earthquake). the changes essentially set a max cap of 65 ksi for the yield strength and a max ratio of 0.85 for yield strength-to tensile strength.
it was closer to 1999 or 2000 that they started making wf out of a992 and stopped making out of a36
actually, many steel producers in the early 90's started "dual certifying" their steel so that it satisfied the minimum requirements of both a36 and a572. that way they didn't have to produce and stock two different grades. so even though many engineers still specified a36 wide flanges, chances are fair that they ended up with a yield strength of over 50 ksi anyway. if the numbers don't work out with assuming a conservative strength, a testing lab can take a coupon sample from a low-stress region and tell you what the actual strength is.
hardness testing might give some indication- perhaps more useful if comparing samples of two different materials. but as pointed out above, much of the steel is either dual-certified, or at least has yield strength quite a bit higher than the minimums, it could be hard to tell that way. even testing coupons, you have no way of knowing if the next beam over is the same material, same heat, etc.
thank you all for your time and answers.
mlm
here's a link to the ryerson warehouse stocklist which indicates to me that there still could be a lot of a36 being shipped. any opinions?
regards,
-mike

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