Center of rigidity

[siuceric21]

When calculation the torsional moment on a structure, is the center of rigidity calculated the same way for multi-story buildings compared to single story buildings.

 

[ash060]

Yes it can be calculated the same way

 

[siuceric21]

Ok well thank you to me it doest make sense to assume the center of rigidity would be in the same location for a two story building.

 

[ash060]

The C.R. is where it is calculated to be where it will be. It is just a tool to distribute your lateral loads to your walls and frames. If you have a different shear wall configuration it will be different at each level, but shear walls should go to the ground.

For a two story building I don't see a problem with calculating the C.R. at each level.

 

[siuceric21]

alright well thank you very much for your input i am doing some research and i am going to run finite element software to see if i find any error developing in the method.

 

[JoshPlumSE]

In hand calculations, yes the center of rigidity would be calculated the same way for multi-story buildings. But, it is quite possible that a more accurate FEM type analysis could provide significantly different results. Especially in these cases:

1) Lateral force resisting system is signicantly different from one level to another.

2) Stiffness of the system (due to brace size, story height, or thickness or nailing of shear wall) varies significantly from one floor to another.

3) A floor where this is a discontinuity in the lateral force resisting system.... i.e. a braced frame or shear wall terminates and that force has to be dragged through a collector element or diaphragm to another lateral frame or wall.

 

[siuceric21]

ya i am thinking there will be a considerable error developed for certain cases...thank you very much for all your input.