Hi everyone,
Is there anyone who modeled SDOF system considering soil structure interaction and using non dimensional parameters such as the non-dimensional frequency as an index for the structure-to-soil stiffness ratio?
Thanks
Soil structure interaction
Moderators: silvia, selimgunay, Moderators
Re: Soil structure interaction
Hi,
As I understand your question, you are interested in frequency domain analysis of soil-structure interaction which is valid only in Linear soil-structure system. On the other hand OpenSees is designed/tailored for time domain analysis of non-linear soil-structure system, to be useful in performance based earthquake engineering.
You can use constant spring and damper parallel material to represent (very very approximately, provided these constants are chosen calling for great engineering judgement and experience) the far field soil in an OpenSees (or many other commercial softwares) model, which essentially remain elastic, provided your near-field soil domain is sufficiently large (with increased computational 'cost'). These 'constant' spring-damping parameters may be taken judiciously from appropriate models (such as BEM, SBFEM, Cone-models etc., Literature is quite voluminous). Out of these, cone models are the easiest conceptually and also at implementational level; MATLAB or Scilab may be a better option to use in such case to find the impedance functions.
For homogeneous half space, simple expressions given by Gazetas (1991, ASCE Geotech Jnl, 117(9), 1991) may be used, which are also adopted by FEMA later. However, in principle, frequency dependance cannot be handled directly in time-domain, unless the structure-soil system is perfectly elastic (so-called elasto-dynamic solution, using IFFT).
On the other hand, for direct analysis of the nonlinear soil-structure system in time domain, fulfilling the radiation condition exactly is a tremendously difficult problem, more so in case of seismic excitation because of many other issues involved. Thus, the present state of the art is to have a coupled FEM-BEM/ FEM-SBFEM analysis using sub-structuring.
To keep it straight, the problem you mentioned, I believe, is not conducive for modelling directly, using OpenSees only, irrespective of whether the structure is SDOF or MDOF.
Hope this clarifies.
Regards.
As I understand your question, you are interested in frequency domain analysis of soil-structure interaction which is valid only in Linear soil-structure system. On the other hand OpenSees is designed/tailored for time domain analysis of non-linear soil-structure system, to be useful in performance based earthquake engineering.
You can use constant spring and damper parallel material to represent (very very approximately, provided these constants are chosen calling for great engineering judgement and experience) the far field soil in an OpenSees (or many other commercial softwares) model, which essentially remain elastic, provided your near-field soil domain is sufficiently large (with increased computational 'cost'). These 'constant' spring-damping parameters may be taken judiciously from appropriate models (such as BEM, SBFEM, Cone-models etc., Literature is quite voluminous). Out of these, cone models are the easiest conceptually and also at implementational level; MATLAB or Scilab may be a better option to use in such case to find the impedance functions.
For homogeneous half space, simple expressions given by Gazetas (1991, ASCE Geotech Jnl, 117(9), 1991) may be used, which are also adopted by FEMA later. However, in principle, frequency dependance cannot be handled directly in time-domain, unless the structure-soil system is perfectly elastic (so-called elasto-dynamic solution, using IFFT).
On the other hand, for direct analysis of the nonlinear soil-structure system in time domain, fulfilling the radiation condition exactly is a tremendously difficult problem, more so in case of seismic excitation because of many other issues involved. Thus, the present state of the art is to have a coupled FEM-BEM/ FEM-SBFEM analysis using sub-structuring.
To keep it straight, the problem you mentioned, I believe, is not conducive for modelling directly, using OpenSees only, irrespective of whether the structure is SDOF or MDOF.
Hope this clarifies.
Regards.
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With Regards,
sb1966
With Regards,
sb1966