Dear all,
I am modelling a tunnel structure (rectangular) using Soil-Structure Interaction in SAP2000. Which model is better for soil-structure interaction in SAP 2000 joint-springs or Link element?
Thank you very much for your helps.
Joint spring is effective for SSI, link will help you only in use of dampers or isolators effectively..
Dear Prof. Iolanda-Gabriela Craifaleanu,
Thank you so much for your advice.
Joint spring is an elastic element, so you can use it as far as your soil remains elastic or you want to assign equivalent elastic properties of the soil. But for more rigorous analysis you need to explicitly consider nonlinear behavior of the soil and model it through Link elements (Multilinear-plastic link works good in this case).
Link elements are needed. Be sure to address shear and friction. Other forms of FEA may be more suitable.
I think link elements are better if you want to take into account non-linear soil behavior.
Another good option are the Gap elements because allow you to consider stiffness just for compression as well as it works in the really.
CSI Software models soil-structure interaction using a one-parameter Winkler soil model. Soil modeling is demonstrated in the example problem, Beam on elastic foundation, available within the software interface through Help > Contents and Index > Example Problems > Problem J. This example problem, along with the hyperlinks below, present the concepts and techniques associated with modeling soil-structure interaction.
One modeling feature useful to soil-structure interaction is the gap (compression-only) link object, which enables foundation uplift without the development of tensile forces. Note that gap objects exhibit nonlinear behavior, and therefore require a nonlinear load case during analysis
https://wiki.csiamerica.com/display/kb/Soil-structure+interaction
Both links and springs are available for modeling in sap2000, though links are more powerful because they enable nonlinear behavior and may be used either as supports or as connections between two non-grounded joints. Nonlinear link properties are only active when running a nonlinear load case.
this depend on which analysis you want to do i.e. if you want a static analysis you can settle for using springs in the three direction taking inconsideration the stiffness of each spring direction (i x, y, z), but if you want a dynamic analysis and take in your consideration the nonlinear behavior of the soil you can use links (ie dash-pot and multi linear spring)
The link element in SAP should be considered in one direction or three direction ?
Hi Bipin,
It is available for definition of link elements in 3 directions
Multi linear-plastic link element in SAP2000 for defining nonlinear behavior,how to assign the properties in SAP2000 window ? What are the values for soft soil?
If you are using multi linear springs (elastic or plastic) links. How is it possible to make SAP2000 take that into account in its Modal analysis to find the natural frequency in a structure ?
Modal analysis is a linear analysis, so SAP 2000 would use the defined effective stiffness in the Multilinear plastic, rather than the inserted numbers in the table. Effective stiffness itself depends on the maximum displacement of the Link which is unknown at the first place. So a try and error procedure should be used to find the effective stiffness.
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