RE: Implementation of surface load surfaceload

[ryancwl95]

Hi,

I'm currently working on a 1D consolidation soil problem with a 1x1x10 (x,y,z) soil column. The analysis involves applying a load in the z-direction at the top surface of the soil column.

For this analysis, I'm using an SSPbrickup element with 8 nodes, each having 4 degrees of freedom (DOF).

Initially, I implemented the load by placing a nodal load on one of the nodes at the top (master node) of the soil column and using the Equaldof command to tie all the nodes at the top to this master node. The results obtained were satisfactory.

However, I recently came across the surfaceload command and decided to implement it in the same scenario. Unfortunately, the output results showed unequal z-direction displacement, which seems unlikely given that this was the only load applied. Additionally, I encountered the following error while running the analysis in OpenSees:

"WARNING FE_Element::setID() - numDOF and number of DOF at the DOF_Groups"

Attached is a photo showing the unequal displacement at the top of the soil.

Screenshot 2024-03-08 180429.png (150.56 KiB) Viewed 4171 times

I would greatly appreciate any insights or suggestions on resolving this issue.

Thank you.

[ryancwl95]

Hi,

Upon further investigation, I've discovered that the results are as expected when a SSPbrick element type was used.

I've achieved equal z-direction displacements when using an SSPbrick element instead of an SSPbrickup element.

I would still like to use SSPbrickup element types to monitor pore pressure dissipation, is there a way to do so?

Thank you for your assistance.

[STKO Team]

To check if it is an incompatibilty between the surface load and the SSPBrickUP, try to use the FaceForce automation in STKO:
It allows you to input a pressure and it will be converted into equivalent (lumped) nodal laods.
Which is exactly what the surfaceload would do in OpenSees