## damping ratio (beta) for use in calculating gust effect factor (G)

## damping ratio (beta) for use in calculating gust effect factor (G)

(OP)

I am referring to ASCE 7-02, Section 6.5.8.2, Gust Effect Factor for Flexible or Dynamically Sensitive Structures.

The equation for the gust effect factor (G) includes the variable R, or resonant response factor.

The equation for R includes the variable beta which is a damping ratio.

As far as I can tell, there is nowhere in the code where it gives any equation or values for this damping ratio, beta.

Does anyone know how this value is calculated? Thanks for your assistance.

The equation for the gust effect factor (G) includes the variable R, or resonant response factor.

The equation for R includes the variable beta which is a damping ratio.

As far as I can tell, there is nowhere in the code where it gives any equation or values for this damping ratio, beta.

Does anyone know how this value is calculated? Thanks for your assistance.

## RE: damping ratio (beta) for use in calculating gust effect factor (G)

Interesting to note is this states ratios of 0.15% to 0.5% for signs are typical but the guide to the use of ASCE 7-02 sample problem for a sign uses 1%.

With that said I may have missed something

## RE: damping ratio (beta) for use in calculating gust effect factor (G)

## RE: damping ratio (beta) for use in calculating gust effect factor (G)

You know 7-02... 7-05... whatever it takes

## RE: damping ratio (beta) for use in calculating gust effect factor (G)

## RE: damping ratio (beta) for use in calculating gust effect factor (G)

Meca, the structure I am analyzing is a 7 story concrete office building. I have it modeled in RAM and it has a natural frequency of 0.7 Hz.

I am trying to calculate the wind pressure on the penthouse and screen walls on top of the structure.

## RE: damping ratio (beta) for use in calculating gust effect factor (G)

## RE: damping ratio (beta) for use in calculating gust effect factor (G)

I calculated the gust effect factor for rigid buildings across a range of heights for each exposure (B,C,D) and I am getting a factor that is above 0.85 mostly for heights under 400 ft. Is this true? Because if it is then the 0.85 default value isn't conservative. I've double checked my math and it looks ok but it doesn't make sense when ASCE-7 05 says that 0.85 is a conservative value.