Wind load on lattice framework

[cgstrucg]

Hello everyone,

I am struggling to find the wind load on a stair-platform assembly. I am using ASCE7-05 and lattice framework procedure and I am stuck in calculating Cf factors. As shown in the attached figure, the platform has long legs going down and it has stairs. Stairs have stringer designed as channels and all other members of the structure are HSS. Can someone please tell me how to find out Cf factor using Figure 6-22 for this model.

I know I have to find out 2 Cf factors based on HSS and Channels that too in 2 directions. But the epsilon value which is basically solid area/gross area is something I am not able to justify. Looking in one direction, Is gross area going to be full stair assembly with 2 channels and those bracings or is it going to be seperate for stringers and separate for stringer bracings. If separate then what's going to be the gross area for the individual steel members?

Any guidance would be appreciated. Thank You.

 

[JStephen]

I don't know that it meets the intent of "lattice framework". I note that for epsilon less than 0.1 for flat sided members, Cf is 2.0 per 6.22, and per Figure 6.21, for a long square shape, Cf is also 2.0, so that would be my first choice.