Hi, I would like to determine the bearing capacity of mat foundation in PLAXIS 3D. I have tried two methods, one where I applied a surface displacement along the z axis (free along the x and y axis), the other where I applied a prescribed surface load along the z axis followed by a strength reduction phase (I would obtain the bearing capacity by multiplying surface load by MSF obtained). The results obtained are different.
Can i check what is the difference between both methods mathematically? Which method would be the correct method to determine the bearing capacity of a mat foundation? When applying the prescribed load, should I add a dummy element to model the mat foundation?
Hi Alvin,
When a prescribed displacement (displacement control) is applied, it is considered for a rigid footing, or the surface to be applied displacement has the same displacement. Therefore, when you use the load (load control), please make sure that the surface has also the same displacement, so, use very stiff footing for example. If not, it is a flexible footing, resulting in different load-settlement response. So, basically both approaches are fine but should be consistent when comparison.
When you apply a plate (or volume) for the load control, it should be very stiff to make sure it is a rigid footing.
Can I check that for both displacement control and load control, given the same boundary conditions and soil type, the load-settlement response will be different but the ultimate bearing capacity generated will be the same?
If you can make sure the same behavior or mechanism failure, the ultimate bearing capacity should be the same