I posted this in the general forum but it probably belongs here.(adsbygoogle = window.adsbygoogle || []).push({});

This is a tricky one!

I'm unsure about the forces on the ground level.

The problem is a 2-spring-damper system with three levels. A ground level, level 1 and level 2. Then a force is applied to the ground level simulating an earth quake (eg the force could be sinusoidal). See the attachment for a diagram.

These are the forces I have resolved:

-level 2 mass:

gravitational force, m0*g (down)

Spring Force2, K1*(x1-x0) (up)

Damper Force2, b1*(x1'-x2') (up)

Inertial Force, m*x0'' (down)

-level 1 mass:

gravitational force, m*g (down)

Spring Force1, K1*(x2-x1) (up)

Damper Force1, b1*(x2'-x1')(up)

Inertial Force, m*x1'' (down)

Spring Force2, K1*(x1-x0) (down)

Damper Force2, b1*(x1'-x2') (down)

-level ground mass:

driving force (earthquake) = some function eg sine

g-force, mg (down)

Spring Force1, K1*(x2-x1) (down)

Damper Force1, b1*(x2'-x1')(down)

Inertial Force = m*x2'' (down)

I have tried to solve this using simulink, but for the positions of each level they fall towards negative oblivion. I am thinking I either have forgotten some force added too many.

Have I left anything out? *thinking*

James

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# Homework Help: Multiple mass-spring-damper system

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