Etabs: Irregular Loading Etbs

[Meekis]

I am working on a project with irregular loading on Etabs. It is just a simple model at the moment, with just gravity loading and seimic loading. I made a load combination of the two loading and run an analysis. I noticed that if I varied the loading it had no impact on the story drift, which makes me think that Etabs is not analysising the effect of the dead+seimic together. Any ideas in what I am doing wrong?

 

[slickdeals]

That's not possible. Do you have the right mass source chosen?

 

[Meekis]

Could you explain what you mean by "Mass Source"

 

[jdgengineer]

It's under define --> mass source. The mass source is what the program uses when calculating seismic forces.

 

[johnbridge231]

If the a load that is included in the mass source is changed, the stiffness of the building is modified accordingly, so the drifts will change.
Otherwise, no effect on story drifts will take place.

Analysis and Design of arbitrary cross sections
Reinforcement design to all major codes
Moment Curvature analysis

http://www.engissol.com/cross-section-analysis-design.html

 

[slickdeals]

@john,
The stiffness of the building is independent from the mass. However, the building's time period depends on both mass and stiffness. Higher the time period - lower the seismic forces.