Folks,

Thanks for the feedback on the leveling screws for my seismometer.

Now here is a question regarding a shake table.  =20

I currently have a small shake table that has a 10" base plate which I =
use in the public schools to help kids understand the relationship of =
building structure and materials to earthquake damage.  I divide the =
kids up into teams to construct their "buildings" and then individually =
set them on the shake table.  Because only one building can be tested at =
a time it is more time consuming and less "fun" for the kids because =
they can't easily see how their building measures up to another team's =
building.

So, I am constructing a larger shake table with a 30" base that can hold =
four buildings.  This lets a class divide up into four teams and then =
the entire class can watch their buildings shake at once.

Say an actual building has a footprint of 100 feet square.  Relative to =
a model building which has a footprint of 12 inches square, the width is =
a factor of 100.  I have a variable frequency motor to which I am =
attaching off center cams to create the vibration movement.  Springs =
pull back the base towards the drive shaft with the cams.

So, here is my question.  Has anybody experimented with a shake table of =
this size?  What displacements should I design the cams to create?  I =
could use different size cams to create different "magnitude" =
earthquakes.  Also, what frequencies should I set the motor to run.

Thanks for any help that you might offer.

Kay







Folks,
 
Thanks for the feedback on the leveling screws =
for my=20
seismometer.
 
Now here is a question regarding a shake=20
table.   
 
I currently have a small shake table that has a =
10" base=20
plate which I use in the public schools to help kids understand the =
relationship=20
of building structure and materials to earthquake damage.  I divide =
the=20
kids up into teams to construct their "buildings" and then individually =
set them=20
on the shake table.  Because only one building can be tested at a =
time it=20
is more time consuming and less "fun" for the kids because they can't =
easily see=20
how their building measures up to another team's building.
 
So, I am constructing a larger shake table with =
a 30" base=20
that can hold four buildings.  This lets a class divide up into =
four teams=20
and then the entire class can watch their buildings shake at =
once.
 
Say an actual building has a footprint of 100 =
feet=20
square.  Relative to a model building which has a footprint of 12 =
inches=20
square, the width is a factor of 100.  I have a variable frequency =
motor to=20
which I am attaching off center cams to create the vibration =
movement. =20
Springs pull back the base towards the drive shaft with the =
cams.
 
So, here is my question.  Has anybody =
experimented=20
with a shake table of this size?  What displacements should I =
design the=20
cams to create?  I could use different size cams to create =
different=20
"magnitude" earthquakes.  Also, what frequencies should I set the =
motor to=20
run.
 
Thanks for any help that you might =
offer.
 
Kay