introducing initial condition

[bavafa612006]

Dears,

I want to model free vibration of 2 adjacent building with initial opposite displacement, it means we have 2 buildings which have equal displacement but in opposite direction of each other, then we will release them to start colliding till they stop. the question is how it is possible to model this free vibration and define these initial conditions?

Thanks

[seismosoft]

You ca do this with dynamic time-history analysis by appyling a gradually increasing force at the begining that suddently goes to zero.
The time-history of the force would be something like:

0.1 sec 100kN
0.2 sec 100kN
0.1 sec 0kN
10.0 sec 0kN

Note that the application (icrease) of the force should be done in a gradual manner, so that not to introduce important dynamic effects.
The free vibrations can be observed after 0.2sec.

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