steel construction - need some validation/opinion
steel construction - need some validation/opinion
(OP)
Hi, just yesterday I posted a thread about what do you guys usually do when your expectations dont meet analysis results. In this case I was expecting larger dimensions of steel beam (HEB 240). Its a barn construction (Wolf system) but instead of glulam roof beams I have to make it all in steel. I cant get a second opinion in my company about this at the moment so I hope you guys can help me with some opinions on this.
Barn construction: 10 steel frames in transverse direction that are aprox. 5 m apart. Bases of all columns pinned. Moment connections between top of outer columns and beam and in the ridge.


Loads on a single frame:
https://res.cloudinary.com/engineering-com/image/upload/v1513151791/tips/loads_rsqkeg.pdf
Envelope of bending moments:

I was comparing a stiffnes of standard glulam (GL28h) beam used by Wolf system - cross section dimensions of 14/48 cm with a steel beam and I have figured that stiffnes of steel beam is higher so based on that it should be allright.
Esteel = 21000 kN/cm2
Etimber = 1260 kN/cm2
Isteel (HEB 240) = 11260 cm4
Itimber (14/48 cm) = 129024 cm4
Esteel x Isteel = 21000 kN/cm2 x 11260 cm4 = 236460000 kNcm2
Etimber x Itimber = 1260 kN/cm2 x 129024 cm4 = 162570240 kNcm2
Still Id like to hear some opinions on this.
Barn construction: 10 steel frames in transverse direction that are aprox. 5 m apart. Bases of all columns pinned. Moment connections between top of outer columns and beam and in the ridge.


Loads on a single frame:
https://res.cloudinary.com/engineering-com/image/upload/v1513151791/tips/loads_rsqkeg.pdf
Envelope of bending moments:

I was comparing a stiffnes of standard glulam (GL28h) beam used by Wolf system - cross section dimensions of 14/48 cm with a steel beam and I have figured that stiffnes of steel beam is higher so based on that it should be allright.
Esteel = 21000 kN/cm2
Etimber = 1260 kN/cm2
Isteel (HEB 240) = 11260 cm4
Itimber (14/48 cm) = 129024 cm4
Esteel x Isteel = 21000 kN/cm2 x 11260 cm4 = 236460000 kNcm2
Etimber x Itimber = 1260 kN/cm2 x 129024 cm4 = 162570240 kNcm2
Still Id like to hear some opinions on this.






RE: steel construction - need some validation/opinion
I'm also not a giant fan of only a 240 deep beam spanning the 8.43m, that's an L/d of 35. A little higher than I would typically go. I'd be looking at something in the 350 deep range.
RE: steel construction - need some validation/opinion
I have checked drift. In a model I have taken into account that outer columns are fixed with 20% fixity of column stiffnes. I have also modeled haunch that is 2 m in lenght from the face of a column.
Drift for load combinations without earthquake:
Drift for earthquake load combinations:
The bending moments, shear and axial forces arent that big... as I said... the beam is not even close to be at max utilization...
But still I feel uneasy with a beam being only 240 mm.
id like to see more opinions.
thanks
RE: steel construction - need some validation/opinion
When I was comparing stiffnes of timber beam to steel beam I found that the steel beam is even stiffer at a hight of just 240 mm.
REPOST:
Esteel = 21000 kN/cm2
Etimber = 1260 kN/cm2
Isteel (HEB 240) = 11260 cm4
Itimber (14/48 cm) = 129024 cm4
Esteel x Isteel = 21000 kN/cm2 x 11260 cm4 = 236460000 kNcm2
Etimber x Itimber = 1260 kN/cm2 x 129024 cm4 = 162570240 kNcm2
Have I missed something?
ALSO, if I choose IPE 330 that has similar moment of inertia (Iy = 11770 cm4 ) as HEB 240 (Iy =11260 cm4) I get better L/d ratio but as far as stiffnes go its pretty much the same... So if Id change a section Id use IPE 330 instead of HEB 240 but I dont really see a reason to do so?! What do you think?
RE: steel construction - need some validation/opinion
RE: steel construction - need some validation/opinion
IPE 330: 49,10 kg/m
Its cheaper - you got that right!
But as far as stiffnes goes Its pretty much the same.
looks like Id change it to IPE.
RE: steel construction - need some validation/opinion
RE: steel construction - need some validation/opinion
BA
RE: steel construction - need some validation/opinion
RE: steel construction - need some validation/opinion
Its strange since calculations shows that a steel beam with height of just 240 mm is sufficient (HEB 240), but it kinda doesnt feel right for a span like that. But if I substitute it with beam that has height of 330 mm (IPE 330) I have pretty much the same stiffnes but it looks much better. IPE 330 is also much lighter so thats a plus, but I have to check buckling first.