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horizontal irregularity 1a (asce7-05)
does anyone know of an exception based on the magnitude of the story drift? i have a two-story building with special concentric braced frames relatively symmetrical, seismic design category d. when i calculate the torsional irregularity, i am outside of the 1.2 limit, but the seismic drifts are very small, around h/600.
for example: assume 18 feet from the second floor to the roof. one corner has a story drift of 0.36", the other corner drifts 0.23". the average drift x 1.2 = 0.354". this would be defined as torsionally irregular even though the maximum story drift is less than 3/8". that seems ridiculous. am i missing something? seems like there should be an exception for when the magnitude of the story drift is very small.

2009-09-09, 05:01 PM	#1
huangyhg 超级版主注册日期: 04-03 帖子: 18592 精华: 36 现金: 249466 标准币资产: 1080358888 标准币	horizontal irregularity 1a 9asce7-050 horizontal irregularity 1a (asce7-05) does anyone know of an exception based on the magnitude of the story drift? i have a two-story building with special concentric braced frames relatively symmetrical, seismic design category d. when i calculate the torsional irregularity, i am outside of the 1.2 limit, but the seismic drifts are very small, around h/600. for example: assume 18 feet from the second floor to the roof. one corner has a story drift of 0.36", the other corner drifts 0.23". the average drift x 1.2 = 0.354". this would be defined as torsionally irregular even though the maximum story drift is less than 3/8". that seems ridiculous. am i missing something? seems like there should be an exception for when the magnitude of the story drift is very small. __________________ 借用达朗贝尔的名言：前进吧，你会得到信心! [url="http://www.dimcax.com"]几何尺寸与公差标准[/url]