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vertical acceleration - modal analysis
folks,
i have a question pertaining to the vertical accelerations per ubc 97.
in section 1631.2 - 5, it states that vertical accelerations can be defined by scaling the horizontal accelerations by 2/3.
in section 1630.1.1, a ev factor is used to include the vertical effects.
my question is thus:
i have performed a modal analysis and need to scale my base shears to 90% of the static base shear.
can this be done in any one of the options i list below?
option 1. compute e using equation 30-1 including the effects of vertical acceleration. scale the response spectrum results to 90% of the above computed value in both directions and not use section 1631.2-5
option 2. compute e using equation 30-1 but without the vertical effects. scale the response spectrum to the static values in x and y direction, and use a 2/3 factor on these scale factors for vertical excitation. etabs for example has a uz excitation component. i am plugging the 2/3 horizontal value into this input box for each direction separately.
please let me know if this approach is right.
thanks

2009-09-16, 06:15 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	vertical acceleration - modal analysis vertical acceleration - modal analysis folks, i have a question pertaining to the vertical accelerations per ubc 97. in section 1631.2 - 5, it states that vertical accelerations can be defined by scaling the horizontal accelerations by 2/3. in section 1630.1.1, a ev factor is used to include the vertical effects. my question is thus: i have performed a modal analysis and need to scale my base shears to 90% of the static base shear. can this be done in any one of the options i list below? option 1. compute e using equation 30-1 including the effects of vertical acceleration. scale the response spectrum results to 90% of the above computed value in both directions and not use section 1631.2-5 option 2. compute e using equation 30-1 but without the vertical effects. scale the response spectrum to the static values in x and y direction, and use a 2/3 factor on these scale factors for vertical excitation. etabs for example has a uz excitation component. i am plugging the 2/3 horizontal value into this input box for each direction separately. please let me know if this approach is right. thanks __________________ 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]