Curved Canopy - Beam Capacities
Curved Canopy - Beam Capacities
(OP)
Hi,
I am currently modeling a curved canopy. The RISA model is attached. The member named "Curved Beam" is giving me high D/C ratios. at the tail end of the canopy (0.81 for envelope). The suggested design members seem unrealistically large. On the detail report I am seeing that equation H1-1b is controlling for the code check. However, when I do this code check with my enveloped Mz, My and A, I get that it should actually be closer to 0.17. Can someone let me know if there is anything wrong which I am doing in the model? Also, of note, I set my unbraced lengths to 0 at the top and bottom of the beams.
Thanks
I am currently modeling a curved canopy. The RISA model is attached. The member named "Curved Beam" is giving me high D/C ratios. at the tail end of the canopy (0.81 for envelope). The suggested design members seem unrealistically large. On the detail report I am seeing that equation H1-1b is controlling for the code check. However, when I do this code check with my enveloped Mz, My and A, I get that it should actually be closer to 0.17. Can someone let me know if there is anything wrong which I am doing in the model? Also, of note, I set my unbraced lengths to 0 at the top and bottom of the beams.
Thanks





RE: Curved Canopy - Beam Capacities
however did you also set your unbraced length for axial to zero (or near zero) if you're trusting both your top and bottom flanges to be fully laterally supported.
RE: Curved Canopy - Beam Capacities
http://files.engineering.com/getfile.aspx?folder=c...
I have both axial and flexural set to near zero.
RE: Curved Canopy - Beam Capacities
As for the overall analysis, were you intending on doubling up your wind loads? LC 5 and 6 both account for Wind A and B. That means on the back half of your canopy you're pushing 160 PSF downward wind force at service levels. Seems extreme. Due to this, you're getting deflections under factored loading in excess of 5" (@ N342 and N348) which could be some of the cause of the code check issues.
Just my 2 cents.
RE: Curved Canopy - Beam Capacities
Now, if you do not believe these warping stresses are real (or want to account for it in a different way) you can turn off this effect by going to the solution tab of the (Global) model settings and unchecking the checkbox that says Torsional Warping. This affects the stiffness of the model as well as the stress calculations.
Warping is a tough concept and RISA accounts for it in an imperfect way. Better than most structural programs, but certainly not perfect. So, if torsion because an important part of your project, it is always a good idea to take a closer look at those forces / stresses and make sure you agree with them. In your case, I wonder if your connections are really going to be detailed out in a way which will impart torsion into those beams.
RE: Curved Canopy - Beam Capacities
RE: Curved Canopy - Beam Capacities