What are the Center of Mass and Center of Rigidity?
Centre of Mass
For any given load case or combination, all gravity loads (self weight, slab dry, live, etc.) applied to a given floor have a center of action (or centre of mass), a point about which the loads would balance if a pinned support were positioned at this location in plan.
You can graphically review this for each floor and each loadcase/combination. By hovering the cursor over the center of mass a tooltip displays its coordinates.
This can be displayed by ticking Centre of Mass in the Scene content and cycling through the loadcases or combinations.
Centre of Rigidity
Any given floor has a center of rigidity or bending stiffness based on the stiffness of the structure that supports it (i.e. the columns, walls etc. below).
Its location can be rapidly approximated “on the fly” for each floor - you will see the position constantly changing as the model develops - and by hovering the cursor over it, approximate coordinates can also be displayed.
The calculation of the centre of rigidity is only approximate (as shown in the tooltip text) and intended to give a broad idea of its location per level; Tekla Structural Designer uses a simple and approximate method for the summation of lateral stiffness of walls, braces, etc.
The centre of rigidity is reported for information purposes only and is not used in any manner in the analysis and design processes; the complex nature of the calculation would unnecessarily extend the overall model solution time.
This can be displayed by ticking Centre of Rigidity in the Scene content