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Does ETABS amplify accidental torsional eccentricity
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by 1.5
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, as required by IS:1893?
A: Currently it is not implemented for statically applied lateral loads due to EQ. For dynamic analysis accidental torsional eccentricity need not be enhanced and hence no further work is required if you are doing only a spectrum analysis. However if you are doing a static analysis where you need to enhance accidental torsion for the inherent torsional eccentricity, then first compute the eccentricity in a story by seeing the CM and CR locations and next workout the coordinate of the point which will define enhanced eccentricity correctly. Finally define another quake type lateral load but use only user load options and in the dialog box use new coordinate of point of application of load and Answer: ETABS does not automatically amplify accidental torsion. Dynamic analysis need not amplify the accidental torsion which results from eccentric application of lateral earthquake loading. For static analysis, accidental torsional eccentricity may be amplified manually through the following process:
- Compute geometric eccentricity by locating the centers of mass and rotation within a story.
- Locate the coordinate where enhanced eccentricity will be defined.
- Define an additional lateral load case of QUAKE type. Use only the User Load options, then in the dialog box, use the coordinate calculated as the point of load application, and enter the value of story shear.