NBCC Formulations for Wind Accelerations
NBCC Formulations for Wind Accelerations
(OP)
I am in the process of developing a worksheet to calculate the along-wind and across-wind response of tall buildings subject to wind loads.
The NBCC formulation has a gust factor gp that is calculated based on various parameters, one of which is the fundamental frequency in the along-wind direction.
This gust factor is then used in calculating across and along-wind accelerations aw and ad, in conjunction with along-wind and across-wind fundamental periods.
My questions are thus:
1. Do you compute two gust factors, one each for wind along X axis and Y axis, with appropriate building period?
Assuming a building is rectangular in plan 100' x 50', with period of T1 = 5s along short direction and T2=3.5s along long direction, you will have gust factor based on T1 and T2...right?
2. You will then use these gust factors and apply them in the acceleration formulas using the appropriate along-wind and across-wind periods...right?
Appreciate your inputs.
Also, does anyone have a similar worksheet to compute ballpark acceleration values to see if your building is in trouble prior to heading to the tunnel?
The NBCC formulation has a gust factor gp that is calculated based on various parameters, one of which is the fundamental frequency in the along-wind direction.
This gust factor is then used in calculating across and along-wind accelerations aw and ad, in conjunction with along-wind and across-wind fundamental periods.
My questions are thus:
1. Do you compute two gust factors, one each for wind along X axis and Y axis, with appropriate building period?
Assuming a building is rectangular in plan 100' x 50', with period of T1 = 5s along short direction and T2=3.5s along long direction, you will have gust factor based on T1 and T2...right?
2. You will then use these gust factors and apply them in the acceleration formulas using the appropriate along-wind and across-wind periods...right?
Appreciate your inputs.
Also, does anyone have a similar worksheet to compute ballpark acceleration values to see if your building is in trouble prior to heading to the tunnel?






RE: NBCC Formulations for Wind Accelerations
RE: NBCC Formulations for Wind Accelerations
Are you suggesting that I should use the higher Gust Factor value for both directions, but use the appropriate fundamental frequency for along-wind / across-wind?
RE: NBCC Formulations for Wind Accelerations
RE: NBCC Formulations for Wind Accelerations
RE: NBCC Formulations for Wind Accelerations
RE: NBCC Formulations for Wind Accelerations
In Appendix G "Accelerations for Wind Sensitive Structures" AS1170, there is a formula for calculating along-wind accelerations.
It uses
Δz = height of the section of the structure upon which the wind pressure acts
I don't quite understand what Δz is. Is this equal to the height of the structure above ground, or in other words equal to "h"?
RE: NBCC Formulations for Wind Accelerations
RE: NBCC Formulations for Wind Accelerations