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LS Dyna

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  3. How to mimic 1D site response analysis in 2D without using *CONSTRAINED_NODE_SET

How to mimic 1D site response analysis in 2D without using *CONSTRAINED_NODE_SET

    • May 15, 2026 at 2:10 am
      muhsinacarr
      Subscriber

      Hi everyone,

      I’m running a 2D plane-strain site response analysis of a soil basin. To handle the side boundaries, I meshed 1D columns (local periodic boundaries) on the far left and right edges, and connected them to the main basin using dashpots.

      During gravity initialization (Dynamic Relaxation), I use a *BOUNDARY_SPC_SET_BIRTH_DEATH to lock the basin edges horizontally so a gap doesn't form. DR converges perfectly, and the mesh sits completely flush.

      I am also applying sigma_xx and tau_zx  form elout to the inner sides of main model which are on the boundary between far side columns and main domain. 

      I am still not capturing uniform free field response on the surface. 

      How can I mimic the free field case just like a 1D site response analysis? (I cant want to use *CONSTRAINED_NODE_SET as I will non-flat non-uniform geometry affects in future) 

      Best,

      Muhsin

       

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