Hello Dear researchers:
In a mouvement equation for a multistory building how we determine the {r} vectore or [r] matrix that distribute the ground acceleration on each floor (see the equation):
[M]x'' + [C]x' + [K]x = [M]{r}x''g
where X''g is the ground acceleration
best regards
dear mehdi:
since the earthquake force affect each floor, the r is a vector of value=1 and dimension of the number of floor.
Dear Nassim;
that vectore of value =1 is not 100% representatif of the real distribution, i've see that on a chaking table.
regardes
what you observed is the response of your model and not the ground input motion.
from shaking table you have an input (base input) and the response that you record. how did you observe the r vector?
Dear Ali,
Let us assume for a moment that I've NOT seen anything on shake table, and start this discussion afresh, as there are many other reasons for such a behaviour, most important being the mode shape.
I was tring to understand the vibrations of upper stories of a MDof System, and while developing the equations of motion for higher stories (>1), I got stuck in the input or exciting acceleration for these stories. What I feel is that the vibrations of higher stories are calculated on the basis of vibration of the storey below them and not on the groung motion. Thus the "Ground Motion Influence Vector cannot be equal to {1}.
dear mehdi:
this document is useful for you
DEFINITION OF THE INFLUENCE VECTOR IN EARTHQUAKE
ANALYSIS
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