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ASCE 7-05 Wind Load - Simplified Methods by S.K. Ghosh in

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Tuesday, May 08, 2007


I was reviewing the two part series in the Structural Magazine by S.K. Ghosh, SE, PhD titled “Professional Issues: Searching for simplicity” . At the end of the article for Part 2 there was a comparison for wind loads on a multi-story concrete structure between the 97 UBC and the 2006 IBC. The 97 UBC was more conservative by less than 10% in each level. My question is this;

The determination for wind loading (the example was taken in Los Angeles for an 85 mph wind in exposure B) is much easier to calculate in the 97 code. I am hung up on the ASCE 7-06 section 6.8.2 calculation for n1 – the natural frequency of the building. In none of the literature from ASCE or in the IBC does it explain how to calculate the actual Natural Building Frequency (based on a PDF search of both files as I have the IBC 2006 code that I purchased). If my outcome is simplier to calculate in the 97 code, why can’t I take the more conservative approach OR am I missing something?

The new version of TEDDS 10 provides the Wind Load analysis based on ASCE 7-05 Chapter 6, but does not provide a comment for n(sub1). If I want to find out more from the ASCE website I have to become a member to access the library of information and I don’t believe this is ethical. I’ve already purchased the documents and now to find out more detailed information I have to become a member of ASCE or of the SEI to obtain additional help on calculating the wind load in the next code that California will use?


Maybe I am being unreasonable, but my budget is limited for a small sole proprietorship and I have already spent a fortune for subscriptions to software and for copies of codes that I had expected to find information on each code section. However, the IBC 2006 does not provide the ASCE 7-05 information other than a reference and I have to them purchase another book and possibly become a member of ASCE to be allowed access of how to use the new code.


Okay! I don’t mean to bitch about this, but it is frustrating. Can anyone lead me to the proper design information to calculate the building natural frequency for a flexible structure? OR, can you tell me if I am being conservative but reasonable to stick with the 97 Wind load calculations. It seems that even TEDDS had some trouble determining how to calculate n(sub 1) and did not provide an example or reference to where it can be explained.


I would appreciate any help I can get on this. Are other’s experiencing the same frustration I am in trying to interprete the new code. S.K. Ghosh’s articles have been the most informative and I appreciate this, but if I have to spend a few hundred dollars to attend a webcast of his lectures on the new code, I would like to know that these jewels of information will be disclosed for those of us too far from a major city to attend in person.


Sorry about the outburst, but I can use any help I can get on this.






Dennis S. Wish, PE

California Professional Engineer

Structural Engineering Consultant

C-41250 (Exp. 3/31/09)




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