Earthquake safety precautions for a grand piano?
Ralph Becker-Szendy
seismology, architecture, and mechanical engineering: How to secure a
grand piano in an earthquake-safe manner.
Details. My piano at home is 5' wide, 6' long, and weights about 850
pounds. The weight is all in the top part (imagine a grand piano),
distributed (pretty evenly) on three legs, about 2' tall. The legs
have casters, but grand pianos typically don't roll well (the casters
are far too small and the typical floors to soft for that). The legs
clearly can handle the weight of the piano, and are even sturdy enough
to allow rolling the piano over onto its side very slowly (with three
burly movers supporting it), but are clearly not designed to handle
major horizontal shock.
We currently live 10 miles from the Loma Prieta epicenter, and
more-or-less 8 miles from the San Andreas fault, but we are planning
to move up in the mountains, closer to the fault line. Clearly this is
earthquake country (but around northern California, what isn't). So
here is the question: What (if any) can one do to protect the grand
piano and the house in the case of an earthquake.
There are two issues, closely related: (a) protecting the grand itself
(it is relatively valuable), and (b) protecting the structure of the
house (wouldn't want the piano to take out a wall or fall through the
floor).
The first concern is obviously floor loading. That can be dealt with
with adequately engineered joists and extra support between them. For
example, triple the joists around the legs, and put 4x blocking
between them. Also, to reduce local floor loading, "saucers" can be
used (right now the piano is standing on 6" dia. 1/8" thick aluminum
disks with rubber padding). The support would have to be engineered
for at least twice the static weight plus safety margin (I vaguely
remember that one has to design for an extra 1g of acceleration in any
direction).
Much more worrisome is horizontal motion. If that 1g persists
horizontally for 1/2 second, the piano will be rolling (flying?)
sideways at 17 ft/sec (about 11 mph) relative to the ground (maybe
relative to the structure), and has traversed 4 feet in the first half
second. None of this is new to earthquake-safe structures, but 800lbs
coming at the wall at 11 mph are worrisome. In particular since the
piano may have sheared its legs off, and will now crash from two feet
elevation onto the floor. In the situation of 1g horizontal the piano
might be the least of my worries, but there are also earthquakes come
in all sizes, with all directions of motion.
What does one do about this (short of buying insurance, but I'd rather
prevent the problem)? I would think that simply securing the bottom of
the legs (the casters) to the floor would not be a good idea, since it
will make sure that the body of the piano will get going sideways and
shear off the legs (probably already in a mild shaker). For a small
tremble, the best thing might be to let the piano walk a bit, and put
up with cosmetic damage on the walls, floor and the piano itself. The
only idea I have (which is probably terrible overkill) is to engineer
the floor under the piano to take the load of the instrument in all
directions (even horizontal), and then hold it down with six steel
guywires (one pair strung and tightened crosswise across each pair of
legs) to prevent the body of the piano from moving independent of the
floor. Like that, the legs are always loaded in compression, and the
wires take the shear load. Mounting the wires on the frame of the
piano is no problem (there are about 2" of wood all the way around),
and in the floor appropriate supports can be built in. Clearly, this
solution reeks of unelegant overkill.
Any experiences? Any suggestions? Is there literature on this subject?
There must be thousands of grand pianos in seismically interesting
areas.
--
Ralph Becker-Szendy RA...@SLAC.STANFORD.EDU
Stanford Linear Accelerator Center RA...@SLACVM.BITNET
M.S. 95, P.O. Box 4349, Stanford, CA 94309 (415)926-2701
My opinion. This is not SLAC, Stanford U, or the US DoE speaking. Just me.
Marc T. Kaufman
>Here is a question which is on the borderline between music,
>seismology, architecture, and mechanical engineering: How to secure a
>grand piano in an earthquake-safe manner.
The informed opinion of a piano technician I trust is: don't bother. The
legs will NOT shear off (they are mounted to the piano with very large bolts).
The best thing for stress on the piano is to let it move horizontally on the
floor. The soundboard and harp are much more rugged than your walls. You
may sustain cosmetic damage to the case if it moves a lot, but in a *REALLY*
big earthquake the house will fall down on the piano, which renders all
stabilization techniques questionable.
--
Marc Kaufman (kau...@CS.Stanford.EDU)
Terence T. Lung
>Details. My piano at home is 5' wide, 6' long, and weights about 850
>There are two issues, closely related: (a) protecting the grand itself
>(it is relatively valuable), and (b) protecting the structure of the
>house (wouldn't want the piano to take out a wall or fall through the
>floor).
>might be the least of my worries, but there are also earthquakes come
>in all sizes, with all directions of motion.
>Any experiences? Any suggestions? Is there literature on this subject?
>There must be thousands of grand pianos in seismically interesting
>areas.
Easy.
Option 1: Take the piano off its legs and put it outside away from
anything that can fall on it.
Option 2: Just make sure nothing can fall on the piano. For the
house, consider designing it with shear walls--so the walls move
as "units" rather than as individual elements that wind up in
different positions after your dynamical input. Don't use bricks
in the house's construction. Minimize the amount of concrete and
other "rigid" structural components. Allow it to be as flexible
as possible.
Option 3: Don't worry about it. My grand piano (actually my mom's)
has been sitting in a house in the SF Bay Area for 20 years now.
No problems...yet
Terence
i
Virgil Champlin
lb horizontally moving piano could do. It might be a bit more than
cosmetic. -virgil
--
Virgil Champlin cham...@pa.dec.com
Palo Alto, CA
I like satire. I'm just not very good at it.
Bernd Reh (DA Drechsel)
>Here is a question which is on the borderline between music,
>seismology, architecture, and mechanical engineering: How to secure a
>grand piano in an earthquake-safe manner.
>We currently live 10 miles from the Loma Prieta epicenter, and
>more-or-less 8 miles from the San Andreas fault, but we are planning
>to move up in the mountains, closer to the fault line. Clearly this is
>earthquake country (but around northern California, what isn't). So
>here is the question: What (if any) can one do to protect the grand
>piano and the house in the case of an earthquake.
Dear Ralph,
I've got 2 advices for you:
1.) Buy a insurance
2.) See a psychist immedeately
If you do not have any monet for this:
3.) Don't move in areas where erthquakes are likely to happen
Bernd
- -- -
-- - ---
Th s _____
i is a
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rthsh e aime
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John Dooley
>seismology, architecture, and mechanical engineering: How to secure a
>grand piano in an earthquake-safe manner.
>
>more-or-less 8 miles from the San Andreas fault, but we are planning
>to move up in the mountains, closer to the fault line. Clearly this is
>earthquake country (but around northern California, what isn't). So
>here is the question: What (if any) can one do to protect the grand
>piano and the house in the case of an earthquake.
Move to another state.
John D.
Alan Bryce
>>We currently live 10 miles from the Loma Prieta epicenter, and
>>more-or-less 8 miles from the San Andreas fault, but we are planning
>>to move up in the mountains, closer to the fault line. Clearly this is
>>earthquake country (but around northern California, what isn't). So
>>here is the question: What (if any) can one do to protect the grand
>>piano and the house in the case of an earthquake.
Get insurance.
--
===============================================================================
Alan Bryce
Product Assurance
Auspex Systems Inc.
Carl E. Grigorian
>
>horizontally for 1/2 second, the piano will be rolling (flying?)
>sideways at 17 ft/sec (about 11 mph) relative to the ground (maybe
>relative to the structure), and has traversed 4 feet in the first half
>second.
An acceleration of 1g lasting for .5 seconds is a bit outlandish
for any earthquake to generate in a building floor. I know of only
one earthquake record in CA that has had such peak accelerations.
That is the Pacoima Dam record and that is a disputed record. Even
if it happens it lasts for a fraction of a second. It will most
likely be a sharp spike.
>None of this is new to earthquake-safe structures, but 800lbs
>coming at the wall at 11 mph are worrisome. In particular since the
>piano may have sheared its legs off,
If you indeed fix the legs to the floor, it would be very likely that
your piano's legs would fail as this would generate large moments at
the section where the legs join the piano. Those legs weren't designed
for resisting moments.
>and will now crash from two feet
>elevation onto the floor. In the situation of 1g horizontal the piano
>might be the least of my worries, but there are also earthquakes come
>in all sizes, with all directions of motion.
>
>What does one do about this (short of buying insurance, but I'd rather
>prevent the problem)? I would think that simply securing the bottom of
>the legs (the casters) to the floor would not be a good idea, since it
>will make sure that the body of the piano will get going sideways and
>shear off the legs (probably already in a mild shaker). For a small
>tremble, the best thing might be to let the piano walk a bit, and put
>up with cosmetic damage on the walls, floor and the piano itself.
The best solution may be to lubricate your casters. This would
effectively isolate your piano from the floor. The less resistance
your piano has to horizontal motion, the better IMHO. It may 'walk'
a foot or so, but it shouldn't pick up enough kinetic energy to to
do physical harm to anyone. If you are too worried about it walking
away, put a concave dish under each caster. This might not look very
pretty, but it will result in a centering mechanism. Such systems
are used for seismic isolation of real structures.
>--
>Ralph Becker-Szendy RA...@SLAC.STANFORD.EDU
>Stanford Linear Accelerator Center RA...@SLACVM.BITNET
>M.S. 95, P.O. Box 4349, Stanford, CA 94309 (415)926-2701
>My opinion. This is not SLAC, Stanford U, or the US DoE speaking. Just me.
CEG
PS Given the mass of the piano and knowing the radius of curvature
of the dish, you should be able to figure out the natural frequancy
of your isolated piano (Its a pendulum problem). For best results
you want a natural frequency less than 1 Hertz . It should work either
way...