Getting Spring constants from Plaxis 2D when piles are modelled using embedded beams

Hi there, I am trying to use Plaxis 2D model to derive spring constant values for piles. Piles have been modelled using embbeded beam elements. Can anyone explain me how to derive spring constant values along the pile length? I thought I should devide the additional horizontal pressre on soil due to lateral loaded piles by corrosponding horizontal deformation of soil. But some people say spring constnats can be estimed from pile shear force devide by the corropoinding lateral deformation.

Can any one give me anwer please?

  • Dear Namal,

    For example for a Winkler beam which is supported by springs (with all assumptions considered): 
    dQ/dx +f = k*u, where Q is shear force, f is the external load and k*u is soil reaction.
    As we have no external load f, the soil reaction k*u should be in equilibrium with derivative of Q. So, one can calculate k from the (change of) dQ/dX divided by (change of) u.

    On another approach, PLAXIS provides results for skin and lateral forces (reaction: r) on the pile. These can be used also as, r = k*u 
    Of course, if linearity is assumed, using the pile's deformation (u) the spring stiffness can be calculated. 

  • Hi Stefanos,

     

    Thanks for your response. It is really helpful.

     

    In your second paragraph, you are basically saying, spring stiffness is equal to (lateral force of the embedded beam/lateral deformation). Is that correct?

     

    Now I have to do an assessment for the existing bridge abutment which has got some cracks. I have to model the existing conditions as it is and then to provide the spring constant values to the bridge engineering for this model. I am planning to do a Plaxis 3D model with embedded beams or volume elements.

     

    I am trying to use above approach as you mentioned. Can you please provide me any examples calculations/papers or expand your answer with more details.

     

    Many thanks for your help.

     

    Regards,

    Namal