UWOVenky
Geotechnical
- Apr 21, 2015
- 30
In Abaqus, I have an octagonal foundation resting on soil. I am required to produce a Vertical-Horizontal (VH) loading failure envelope for this system. A VH failure envelope for a circular footing resting on soil has been attached. I am describing briefly how this is achieved by using finite element method or Abaqus
All the foundation elements are constrained using rigid body constraint to a reference point (RP)- middle of the base of foundation. This RP is subjected to concentrated load- vertical load (+ Z dir) and hor load(+X dir). I have created a path of centreline nodes on top of soil surface which are in contact with bottom of foundation i.e. these nodes form the foundation-soil interface. The value of load (vertical or hor) are calculated by averaging the value of S33 or S11 resp. These loads are used for calculating the bearing capacity factor or N which in graph ranges from 0 to 1 for horizontal loading and 0 to 6.3 for vertical loading (refer the figure).
When I am doing my analysis, the S33 values which I obtain are okay i.e. the N value is ranging from 0 to 6.3 but the S11 values are also in the same range. This means that the S11 values are also very high. They should be actually low around 6 times less than S33 values. I am not able to understand how to solve it.
In my analysis, I applied a geostatic step first, then gravity load of the foundation and then finally the vertical-hor loading step. I have always got correct results for vertical stress S33, however with S11 how not finding the way out? Anyone has an idea on this?
Thanks.
All the foundation elements are constrained using rigid body constraint to a reference point (RP)- middle of the base of foundation. This RP is subjected to concentrated load- vertical load (+ Z dir) and hor load(+X dir). I have created a path of centreline nodes on top of soil surface which are in contact with bottom of foundation i.e. these nodes form the foundation-soil interface. The value of load (vertical or hor) are calculated by averaging the value of S33 or S11 resp. These loads are used for calculating the bearing capacity factor or N which in graph ranges from 0 to 1 for horizontal loading and 0 to 6.3 for vertical loading (refer the figure).
When I am doing my analysis, the S33 values which I obtain are okay i.e. the N value is ranging from 0 to 6.3 but the S11 values are also in the same range. This means that the S11 values are also very high. They should be actually low around 6 times less than S33 values. I am not able to understand how to solve it.
In my analysis, I applied a geostatic step first, then gravity load of the foundation and then finally the vertical-hor loading step. I have always got correct results for vertical stress S33, however with S11 how not finding the way out? Anyone has an idea on this?
Thanks.