In my ETABS model, the first mode appears as a torsional mode. The structure is symmetric in both directions. There are two opposing U-shaped shear walls located at the center of the building, connected by a coupling beam. What could be the reason for the first mode being torsional?
Eng-Tips is the largest forum for Engineering Professionals on the Internet.
Members share and learn making Eng-Tips Forums the best source of engineering information on the Internet!
-
Congratulations JStephen on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
First mode torsional
- Thread starter Civilboy
- Start date
JoshPlumSE
Structural
There is no way to know based on the information provided. I like to look at the mode shapes graphically.... It helps me to understand what aspects of the structure are affecting them.
FWIW, it ALWAYS comes down to either mass or stiffness.
By stiffness, I mean that some structural elements may not be connected properly or their stiffness properties are not defined properly. In a way that emphasizes the torsional mode.
By mass, I mean that the loading used for mass could be defined in a way that emphasizes torsion.
FWIW, it ALWAYS comes down to either mass or stiffness.
By stiffness, I mean that some structural elements may not be connected properly or their stiffness properties are not defined properly. In a way that emphasizes the torsional mode.
By mass, I mean that the loading used for mass could be defined in a way that emphasizes torsion.
Similar threads
- Question
- Question