Dear all,
I'm desperately in need of help. is there a way in opensees i can introduce the earthquake-induced force time history to the system?
I have modeled a soil-structure system and also calculated the time history of forces caused by the input motion. now, as far as i see it is quite easy to introduce the acceleration, velocity or displacement time history as the input motion to the system. but not yet have i could found a way to introduce the force time history as the input to run the analysis. What should i do?
I greatly appreciate kind helps.
B. JavidSharifi
shaking force time history
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javidsharifi
- Posts: 66
- Joined: Sat Oct 06, 2012 11:08 am
- Location: shiraz university of technology
Re: shaking force time history
define what you mean by force time history and were you would apply the loads. if simply a time varying nodal load, apply a 1.0 value for the reference load and use the Path time series for the time series. of course, if the loads at the different nodes change by a different amount at each time step you would need a pattern and time series for each load and possibly one for each nodal dof.
the alternative is to simply write source code to do what you want.
in future, only post the same question in one forum!
the alternative is to simply write source code to do what you want.
in future, only post the same question in one forum!
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javidsharifi
- Posts: 66
- Joined: Sat Oct 06, 2012 11:08 am
- Location: shiraz university of technology
Re: shaking force time history
Dear Professor,
Thanks a lot.
of course. Sorry.
what I have is interaction forces on the nearfield and farfield interface nodes. Just like when we introduce the acceleration motion to the system and it is applied to fixed nodes of the system (as far as i know), now i have calculated the interaction forces using convolution integrals and having the unit impulse response and effective input motion to the system. the aim is to calculate the nonlinear-plastic SSI response of an RC building. Through the convolution integral I have a force for each time step in which there is an acceleration record. Thus if for example there are 5000 time steps with recorded accelerations, there will be 5000 equivalent forces which are irregular. I am also looking into the matter to see if I should distribute the force to the interface nodes or it is constant for all of them.
maybe it can be a good idea to divide the force vector by the mass of the whole system to have at hand the acceleration time history and then it can be used as the earthquake excitation?
Thanks a lot.
of course. Sorry.
what I have is interaction forces on the nearfield and farfield interface nodes. Just like when we introduce the acceleration motion to the system and it is applied to fixed nodes of the system (as far as i know), now i have calculated the interaction forces using convolution integrals and having the unit impulse response and effective input motion to the system. the aim is to calculate the nonlinear-plastic SSI response of an RC building. Through the convolution integral I have a force for each time step in which there is an acceleration record. Thus if for example there are 5000 time steps with recorded accelerations, there will be 5000 equivalent forces which are irregular. I am also looking into the matter to see if I should distribute the force to the interface nodes or it is constant for all of them.
maybe it can be a good idea to divide the force vector by the mass of the whole system to have at hand the acceleration time history and then it can be used as the earthquake excitation?
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javidsharifi
- Posts: 66
- Joined: Sat Oct 06, 2012 11:08 am
- Location: shiraz university of technology
Re: shaking force time history
in fact i am truncating the far field and replacing it with the forces it causes to the system. it is sort of substructure method for SSI. the effect of the farfield which is linear elastic is being superposed to the nearfield and the structure. this can only be done when internal forces replace the truncated part.