|USING BAR ELEMENTS
Bar elements in CRISP carry axial forces only. Bar elements may be used to represent ties, pin-ended struts (ie no bending moment) and geotextile memberane.
How do I create bar elements?
When do I use 2-noded bar elements as opposed to 3-noded elements?
If the element representing the bar is meant to be embedded between the two adjacent 2D elements, then it would have to be a 3-noded bar. This would insure that the mid-side node of the bar is the same node as the mid-side nodes of the two adjacent 2D elements. Geotextile memberane may be represented by a 3-noded bar element as can be seen in the image below:
|If the bar is to represent a strut (or tie) connecting two points, then a 2-noded bar would be appropriate. For example you might wish to fix a wall against a point on the boundary of the mesh using pin-joints in which case a single 2-noded bar would be sufficient. You must avoid using a 3-noded bar if it is not embedded in soil (or between two 2D elements) as the unrestrained mid-side node of the bar would create ill-conditioning in the stiffness causing the program to stop.
Why do I get axial force for bars in KN/m2 per meter run in the stress output section?
For bars, the output stresses are in fact forces in KN per meter run.
How do I model prestresed force which is in tension in the anchor but pushing (compression) towards the wall?
Let's say you are installing a pre-stressed anchor, modelled very crudely by a 2-noded bar. The diagram below shows a bit of a wall, and a bit of the retained soil in which the fixed length of the anchor terminates. '*' indicates which nodes the bar will be attached to (e.g. nodes 31 and 264 respectively).