Seismic

[Sammy001]

It is my understanding that with earthquakes, lighter structure behaves better. And with hurricane and wind, heavier structure is preferred. Is this correct? If yes, does that mean rigid frame (lighter, flexible) perform better than concrete shear wall during earthquake? Thanks!

 

[dauwerda]

No, I would not agree with your first statement as written.

It is true that in a given seismic event, a heavier structure will result in larger lateral (and vertical) forces due to the accelerations experienced by the building. After all, force is equal to mass times acceleration. So if your accelerations a equal, a larger mass will result in a larger force. This does not mean a lighter structure behaves (performs) better than a heavier structure. That is determined by the structural design and detailing. A heavy structure can be designed to outperform a light structure (and vice versa).

The force of wind is largely unaffected by the mass of a structure.
A heavy structure may resist sliding, uplift, und overturning with its own self weight rather than needing to depend on more robust foundations (and anchoring to foundations). Would I say that that is preferred or better behavior - no, not necessarily.

 

[Sammy001]

So, for seismic if we are comparing rigid frame vs light concrete wall, is one better/more often used than the other? For instance, one of the disadvantages of the wall is it prohibits a lot or big openings unlike rigid frame.

And in terms of wind: what causes building to likely to overturn? Is it wind on the corner of the buildings? Or on the roof? Wind causes uplift on the roof, does uplift cause overturn?