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Building effect in psuedostatic analysis

Building effect in psuedostatic analysis

Building effect in psuedostatic analysis

(OP)
There is a building basement in the back of a slope. The basement penetrates the whole height of the slope. I believe there is some effect on the slope stability from the building inertia. But in limit equilibrium analysis, the software cannot consider the inertia coming out of sliding body. If I apply the inertia manually, how to calculate the inertia force induced by the building? Thanks.

RE: Building effect in psuedostatic analysis

Consider a free-body diagram of the building.  There's a horizontal backfill on one basement wall and a sloping backfill on the "slope" side.  Calculate the at-rest earth pressures from these two conditions (just use 1.5 times the active earth pressure and DM-7.2 for formula).  The difference between the at-rest earth pressures would be this "inertia" if I understand your question.

Now consider the base shear acting on the basement and the isolated column footings (if any).  There will be some resitance to the unbalanced earth pressure from these reactions.

Whatever's left over would contribute to slope forces.  I'd bet their trivial.

f-d

¡papá gordo ain’t no madre flaca!

RE: Building effect in psuedostatic analysis

(OP)
Sorry I didn't write clearly. Please see attached figure. I am doing psuedostatic analysis of the slope stability. I want to find the effect of the building on the slope stability under seismic load.

RE: Building effect in psuedostatic analysis

Assuming that the sketch is to scale, my initial thought is that the building would not contribute much of anything to the load on the retaining wall or to instability of the slope above the wall, unless maybe the building fails structurally.  Look elsewhere on eng-tips for discussion of Mononobe-Okabe method for seismic loads on walls.  That's basically Coulomb active pressure with a horizontal component instead of just gravity.  With no horizontal component, the base of the active wedge is very steep, getting flatter with a steeper slope above the wall, and higher acceleration.  Unless the acceleration is quite high, it probably wouldn't flatten out enough to reach the building.  M-O is not an exact model of reality, but is a reasonable approximation.  Another consideration is that the building and the air that it contains most likely weigh much less than an equivalent volume of soil, so you would not expect it to have any worse effect on the slope than if it was level ground.

Regards,
DRG  

RE: Building effect in psuedostatic analysis

(OP)

The foundation pressure is 7.5ksf and the foundation depth is 40 ft. The building is actually much heavier than the soils. That's the reason I want to check the building inertia effect on the fill slope. I don't think the slip surface under soil gravity and inertia can reach the basement, however with consideration of building inertia I am not sure. And also the building's acceleration may higher than soils.  

Thanks.

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