Seismic response coefficient Cs 3

[structuralnerd]

Can anyone tell me what the seismic response coefficient of a structure means (Cs)? What does it represent? I know that V=CsxW, but does anyone know an explanation for Cs?

 

[dougantholz]

Cs is the the equivalent lateral load factor.
The dynamic character of seismic loads is simplified to a horizontal force in the equivalent lateral load proceedure. Because the amount of force is dependent on the mass of the object (W), the code simplifies the calculation to be a certain percent of W. We call that Cs. Cs is dependent on five things:
Geography or simply the ground acceleration (Sds & Sd1).
The response modification factor (R)
The importance factor of your structure (I)
The approximate fundamental period of your structure(Ta, but also CuTa)
The long period (only valid for 05 ASCE 7 and later).

 

[UcfSE]

It's the "a" in F=ma.

 

[jnadeau]

Great analogy, UcfSE. I would just clarify that the acceleration Cs is in units of g because W is the seismic weight, not mass.