50 KSI Beams, When?
50 KSI Beams, When?
(OP)
I am checking an existing (25-year old) seed corn tower supporting (4) surge bins. The problem I have is that I cannot get the existing support beams to check out. They fail under flexure at 150% using 36ksi steel. If I check with 50ksi they just barley work 103%. However, I do not believe (no drawings) 50ksi was that readily available 25-years ago...
These beams also support the 4" thick concrete surge bin roofs/upper floor. I typically design these floors for 100 to 125psf (IBC - light manufacturing). They are typically only used for equipment access. We typically classify these seed toweres upper floors as equipment access to keep overall structure sq footage down trying to avoid sprinklers.
Does anyone else work on the these seed towers, if so what do you use for your upper floor live loads? 125psf seams heavy, 60psf seams light. I would prefer 100psf and use that for a minimum. However, the code has no good classification for seed towers.
Thanks,
Jeff
These beams also support the 4" thick concrete surge bin roofs/upper floor. I typically design these floors for 100 to 125psf (IBC - light manufacturing). They are typically only used for equipment access. We typically classify these seed toweres upper floors as equipment access to keep overall structure sq footage down trying to avoid sprinklers.
Does anyone else work on the these seed towers, if so what do you use for your upper floor live loads? 125psf seams heavy, 60psf seams light. I would prefer 100psf and use that for a minimum. However, the code has no good classification for seed towers.
Thanks,
Jeff






RE: 50 KSI Beams, When?
RE: 50 KSI Beams, When?
RE: 50 KSI Beams, When?
Mike McCann
MMC Engineering
RE: 50 KSI Beams, When?
RE: 50 KSI Beams, When?
RE: 50 KSI Beams, When?
Is there anything reasonable??
RE: 50 KSI Beams, When?
RE: 50 KSI Beams, When?
RE: 50 KSI Beams, When?
RE: 50 KSI Beams, When?
I don't trust any of the in-situ testing methods yet. Hardness tests would not make me confident enough to use more than 36 ksi... I need to see better research on in-situ methods that proves they are reliable.
RE: 50 KSI Beams, When?
civilperson, I know where you are coming from by stating 103% is OK by you. How will you answer lawyers if you are on the stand when they ask you if 103% is per code! I am not making this up. This is the trend my friends. No code will stand by you either in stating that 103% is OK. The code will say that you are overstressing the structural element more than allowable! I would make sure that my stress is right at 100% of the allowable.
Regards,
Lutfi
RE: 50 KSI Beams, When?
I now have another structure (different location) with beams at 158% (36ksi) and 200% (50ksi) as it currently sits, before we touch it. Also over 1/2 of the bracing is missing... Am I just lucky, or are other structurals running into these inadequate existing facilities.
Jeff
RE: 50 KSI Beams, When?
Just a quick point to address Lufti's 103% comment... I will often accept stress checks that exceed up to 5%, however if I am accepting a solution which has shown 105% check, I only do this after a review of my input assumptions. Often you have more than 5% in your back pocket from your assumed weight of the floors, self weights, etc.
I strongly agree with Lufti: Lawyers will twist the rationale into the seemingly implausible and irresponsible, and then sell it to the judge/jury. The important thing is that your calcs NEVER say "overstress accepted/ok", but rather say "I have been conservative in my dead load assumptions, thus this is actually an artificially high check, and by verification show Demand/Capacity < 1.0"
Just my two thoughts... Otherwise an interesting conversation!
Cheers,
YS
B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...
RE: 50 KSI Beams, When?
RE: 50 KSI Beams, When?
RE: 50 KSI Beams, When?
I have talked to the lawyers on the stand and when they are shown the variability and the significant figures upper and lower limits used in arithmetic they understand that loads and strengths do not have that much accuracy to state stresses to three significant figures.