ASCE 7-05 13.3.1 Seismic Design Force - z/h Question
ASCE 7-05 13.3.1 Seismic Design Force - z/h Question
(OP)
I have a question regarding the z/h term in equation 13.3-1 for calculating the seismic design force for nonstructural components.
I think I understand the definitions of z and h and the purpose of the z/h term in the equation. However, what I find unclear is why the increase in the seismic design force for a nonstructural component on the 2nd floor of a 4 story building is the same as if the same component is located on the 4th floor of an 8 story building. It seems the absolute height above the base of the structure would have some affect on the seismic design force.
What am I missing here? Any input is greatly appreciated.
I think I understand the definitions of z and h and the purpose of the z/h term in the equation. However, what I find unclear is why the increase in the seismic design force for a nonstructural component on the 2nd floor of a 4 story building is the same as if the same component is located on the 4th floor of an 8 story building. It seems the absolute height above the base of the structure would have some affect on the seismic design force.
What am I missing here? Any input is greatly appreciated.





RE: ASCE 7-05 13.3.1 Seismic Design Force - z/h Question
Another is that the z/h factor is trying to consider the whipping action of a building...sort of like if you've ever snapped a wet towel at someone -the tip of the towel (z/h = 1) moves at incredible speeds while the part halfway down the length (z/h = 0.5) is considerably slower. So a 3 ft. towel vs. a 6 ft. towel may not produce all that much different velocity.
Now...no bathroom humor is allowed after this post
RE: ASCE 7-05 13.3.1 Seismic Design Force - z/h Question
RE: ASCE 7-05 13.3.1 Seismic Design Force - z/h Question
I was once in a room when a mild one struck(Richter magnitude around 4.5). Yes, everything in the room including my skull was whipped and I can clearly understand your point of view now.
respects
ijr