03-19-2010, 11:10 AM
Actually, you were asking about soil-pile interaction and how to apply it as a macro element in order to run global analysis of structure using software.
What you need to do is modeling a pile carrying axial compression and lateral loads. It is modeled as a system of rigid elements (like column but no flexural) connected by springs and the soil resistance by external non-linear springs. Each spring has 2 stiffness in vertical/lateral deformations which is defined by t-z curve (or p-y curve) - a force-deformation curve. To develop the t-z or p-y curve you may use the program or manually iteratively calculate using theory presented in
"Pile Foundations in Engineering Practice" by Prakash & Sharma, Pubs:Wiley.
"Pile Design & Construction Practice" by Tomlison & Wodward, Pusb: Taylor & Francis (I think this forum has the link).
The above springs can be linear and nonlinear. However, linear is enough in design practice (exclude pushover analysis). In ETABS, linear model can be represented directly using spring support that connecting each rigid elements of a pile. Hence u just need to key-in the spring stiffness (calculate from t-z curve). Whilst, nonlinear model uses spring as zero-length element connecting each rigid elements of a pile. Then apply t-z or p-z curve for vertical and lateral rigidity whereas the rest of deformations assume in fixed condition.
That is general idea of soil-pile interaction. Sorry for lengthy words.
I hope it will help you and all of the reader regarding this topic.
Adekajeng
What you need to do is modeling a pile carrying axial compression and lateral loads. It is modeled as a system of rigid elements (like column but no flexural) connected by springs and the soil resistance by external non-linear springs. Each spring has 2 stiffness in vertical/lateral deformations which is defined by t-z curve (or p-y curve) - a force-deformation curve. To develop the t-z or p-y curve you may use the program or manually iteratively calculate using theory presented in
"Pile Foundations in Engineering Practice" by Prakash & Sharma, Pubs:Wiley.
"Pile Design & Construction Practice" by Tomlison & Wodward, Pusb: Taylor & Francis (I think this forum has the link).
The above springs can be linear and nonlinear. However, linear is enough in design practice (exclude pushover analysis). In ETABS, linear model can be represented directly using spring support that connecting each rigid elements of a pile. Hence u just need to key-in the spring stiffness (calculate from t-z curve). Whilst, nonlinear model uses spring as zero-length element connecting each rigid elements of a pile. Then apply t-z or p-z curve for vertical and lateral rigidity whereas the rest of deformations assume in fixed condition.
That is general idea of soil-pile interaction. Sorry for lengthy words.
I hope it will help you and all of the reader regarding this topic.
Adekajeng
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