Roof Bracing with Large Building Length to Width Ratio
Roof Bracing with Large Building Length to Width Ratio
(OP)
I am currently designing a building addition located in Arkansas. The building footprint is approximately 440'x128', giving it a length to width ratio of 3.44. In AISC Steel Design Guide 7, James Fisher recommends a maximum length to width ratio of 3.00 for both diaphragm and horizontal bracing design. He says if the ratio is larger than 3.00, an alternate bracing method is recommended. Unfortunately, there is no mention of any alternate bracing methods. I considered placing a braced frame down the center of the building to give the diaphragm a two-span condition, but I would imagine the owner would not be happy with that idea. Does anyone have any other recommendations?
On a side note, I found an article in Structure Magazine's Engineer's Notebook which was written by James Fisher in May of 2004. This article gives a maximum length to width ratio of 4.00 for diaphragm and horizontal bracing design.
On a side note, I found an article in Structure Magazine's Engineer's Notebook which was written by James Fisher in May of 2004. This article gives a maximum length to width ratio of 4.00 for diaphragm and horizontal bracing design.






RE: Roof Bracing with Large Building Length to Width Ratio
Find the loads and forces and then design accordingly...
RE: Roof Bracing with Large Building Length to Width Ratio
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Roof Bracing with Large Building Length to Width Ratio
With a "bending" diaphragm, many of the center columns will have greater lean, and thus greater PDelta forces that will add to your lateral resisting system design. Keep those effects included in your calculations.
RE: Roof Bracing with Large Building Length to Width Ratio
RE: Roof Bracing with Large Building Length to Width Ratio
RE: Roof Bracing with Large Building Length to Width Ratio
I would have some big frames in the 128' directions. Break up the diaphragm until it is what you want it to be. Metal building guys do that kind of stuff all the time
RE: Roof Bracing with Large Building Length to Width Ratio