My problem comes to this: either use addendum 1 values and not use an cost efficient tower, or use addendum 2 and have a design that "follows the code" but may be unsafe. Compressive strength is minor compared to flexure ( <5% ) which applies to both addenda as does the 2nd order analysis. But even with this discussion, I still don't understand how using Addendum 2 I can have a acceptable design while using Addendum 1 I can have an over-stressed design with the same material properties and loading. It may be along the idea of the wind load application and the return periods, but it just seems odd that the effective stress would be increased rather than the return period lowered. That's an interesting discussion on the table although it may be a discussion for addendum 1 which was published in 2007, Addendum 2 was published 2010. I will be using the plastic modulus in subsequent calculations
The section modulus is not used in the development of the effective yield stress. The in the previous addendum, the ratio's lower limit was 1.17 with a corresponding F'y = Fy whereas in addendum 2, the lower limit and F'y equation is as referenced above. RE: TIA-222-G-2 Polygonal Monopole Design danismyname (Structural) The idea with monopoles is that you rely on your 2nd order analysis to give you amplified moments (due to the presence of axial force) and then you check the monopole's flexural capacity. only individual members in a lattice type pole. My belief is that this was done because you don't check compressive strength for monopoles. But, does it also apply to compressive strength? Section 4.5.4.1 of addendum 2 seems to be missing the reference to table 4-8 for polygonal tubes! That seems to indicate that this is really related to the efective yield stress for flexure (to be used in section 4.7.4). The ASCE 48 equations should be extended in the compact regions limited to a nominal strength equal to the yield strength times the plastic section modulus "Z". this is not the case with the TIA-222-G standard (200 to 1000 year returns) as demonstrated for circular shapes. The additional strength capacity was not used by ASCE 48 ias the strength levels in ASCE48 were intended to be limited to first yield to avoid permanent deformation under the NESC loadign conditions (50 year return extreme wind condition). This is supported by the test data used for the equations in table 4-8. I found some meeting minutes from a 2006 committee meeting which said the following:Ĭompact Polygonal Shapes and Effective Stress Equations, Table 4-8:Ĭompact polygonal shapes should be treated in a similar manner as compact circular shapes and be able to develop their full plastic moment capacity.
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