Soil Anchors for seismic footings - tension-only springs?

Re: Soil Anchors for seismic footings - tension-only springs?

Andrew Seeton — Sat, 19 Oct 2013 04:26:06 GMT

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.

Re: Soil Anchors for seismic footings - tension-only springs?

Seth Guthrie — Sat, 19 Oct 2013 04:01:52 GMT

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.