1.) I am using RAM Concept to model a seismic footing under a shear wall. This wall is carrying high seismic shear and moment but has relatively low axial load, so it is tending to overturn. One option is to make the footing larger and pick up nearby columns for additional gravity load. Alternative is to use soil anchors to hold down the footing. I can use point springs in RAM Concept, but I would like to model the anchors as taking tension only. Is it possible to create tension-only springs in RAM?
2.) I am using area springs to model the soil under the footing. I am running a Zero Tension analysis, however I find that the analysis is still producing tension in some of the soil springs; physically this is not possible. Is this simply because I need to increase the number of iterations in the solver? Currently doing 8 iterations on the zero tension solver.
Thanks,
Andrew
1) Point springs in Concept are always linear-elastic. You could remove a small area of the area spring (which is compression-only) to makeup the difference.
2) Probably yes. The program is performing an iterative approach to reach the no tension solution. In a system subject to overturning a solution may take many iterations, or may not even be possible. Besides adjusting the zero tension criteria, you might also refine (shrink) the mesh to give you more springs to work with or add some stabilizing loads.
Answer Verified By: Andrew Seeton
Thanks Seth
1.) Makes sense. Would be a great feature to add tension-only springs to RAM Concept.
2.) Makes sense. In my case the structure is actually unstable due to the large moment and low axial load. Interestingly the program does not identify this instability unless I do sufficient iterations for it to converge to having less than 25% area in contact, in which case it then issues a warning of potential instability. Users need to be aware of this when viewing their analysis results.