Tension elimination
Tension elimination - tension at elastic foundation resulting in a shear is eliminated by means of iterative process. The elastic foundation with taking in to account tension elimination is global defined, means it is working in direction of global axis system. Common used elastic foundation is working local to the member while tension elimination substitution of the elastic foundation is global defined:
Tension elimination by nodal spring value
Tension elimination substitution by the nodal spring value for a very small element is done by using of the single nodal global oriented FE has an axial stiffness only (no length, no support, while no 2nd node).
Members with any Alpha inclination angle (excluding Alpha = ±90° and Alpha = ±270°) have Z spring applied, while members of Alpha = ±90° or Alpha = ±270° – x spring substitution of elastic foundation with tension elimination.
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Z spring: any Alpha (excluding Alpha = ±90° or Alpha = ±270°) |
X spring: Alpha = ±90° or Alpha = ±270° |
Placement of elastic foundation for vertical members
The placement of elastic foundation for the vertical members (walls) depends on local member direction. For the down-top oriented members ground is applied right side the wall, while for the top-down oriented members – left side the wall. This presumption gives influence on elastic foundation with tension elimination only. Elastic foundation with tension elimination local direction for vertical members (walls):
Use cases
1. Calculation without tension elimination
Usual case with compression and tension (could be eliminated) zones of the elastic ground is acting. Zone, where displacement of the beam is top oriented and bending moments acting on top side of the beam is representing tension of the ground what isn’t reliable for real life modeling.
2. Calculation with tension elimination
Usual case with compression and tension (could be eliminated) zones of the elastic ground is acting. Zone, where displacement of the beam is top oriented and bending moments acting on top side of the beam is representing tension of the ground what isn’t reliable for real life modeling.
3. Calculation with only compression on the elastic ground is acting
Tension zone of the elastic ground is eliminated during NL calculation process. No ground left under construction. Structure is representing big displacements. Results are not reliable.
4. Calculation with only tension on the elastic ground is acting
Tension zone of the elastic ground is eliminated during NL calculation process. No ground left under construction. Structure is representing big displacements. Results as moments etc. are not reliable.
5. Calculation of a tunnel using elastic foundation on vertical walls
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| Improper modeling of vertical walls | Proper modeling of vertical walls |