Wind loads for Exposed portal frame per 1170.2-2011 Appendix E

[hrbrt372]

Hi All,

I am currently working on a project to be built in Darwin. It is a skillion roof structure with no walls, 42m wide x 105m length with 6m clear height at the low side. It has 16 portal frames spaced at 7m and a 800WB member size. Following the guidelines listed in Appendix E of 1170.2 I am getting considerably high loads. Approx 4.6kN/m wind load along the portal frame profile. The total loads are way more than compared to a fully enclosed condition. Has anyone here had a similar job? Are there any ways to reduce the loads from exposed steel members that is acceptable?

pu: 2.78kPa
Ki: 1.0
Kar: 1.0
Ksh: 1.0
Cfx: 2.05
Cfig: 32.8 (considering 16 portal frames)

Thanks in advance for the responses!

hrbrt372

 

[asixth]

The 4.6kN/m seems reasonable for a design. For an open structure I use a minimum design of 0.35kPa for serviceability and 0.75kPa for ultimate designing assumming that the structure is hypothetically enclosed. The Cfig of 32 doesn't sound right.

 

[hrbrt372]

Thanks for the reply asixth.

I have 16off portal frames and each portal frame has cfig1 = 2.05. On equation E2(5) in AS 1170.2 Cfig is equal to the summation of Cfig1 of each portal frame.