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Old Posted Feb 21, 2014, 7:49 AM
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seismic seismic is offline
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Static loads are loads.
The vertical prestressing load is also a load
The static loads of a structure, containing inert intensity
Loads of prestressing not contain inert intensity.

This makes the difference in deformation.
If you see the video towards the end, the beams of seismic base, tend to rise upwards from the torque of the model.

If the buildings are not anchored to the ground at the end become like this

This torque is destructive for the building (not compacted building) because once the oscillation lift the unilateral model, the loads of the building creates a torque on all nodes, which breaks the columns and beams.
If the model is anchored, loads are balance because it does not lift unilateral, the loads are balanced by the reaction of the seismic base, and we have no torque at the nodes.
Now let's see what is best for the building;
a) The embedding of the building be applied between the base and the ground;
b) The embedding of the building, be applied between the roof and the ground;
c) or is it better instead of embedding the roof and the ground to apply a little pretension between base and roof, and at the same time and an embedding with the same mechanism between base and ground;

a) For me better than nothing, is the embedding of the building to be done between base and ground.
b) Too much better, the anchoring of the building to be done .. between roof and ground.
c) And even better, well, when you apply a little pretension between base and roof,
and at the same time and an embedding with the same mechanism between base and soil.
I'll tell you an example to understand my view.

If you have a wooden stick and shake it back and forth by hand, we will see that the top of the rod will oscillate more than the bottom.
Rod has clamping down on our hands, but the oscillation does not stop. Oscillation = deformation, deformation = damage or collapse.
Now if the stick is not elastic (short-pillar section) but we had in our hand a thicker wood (large diameter column)
if you swing with your hand then it will be stiff. (And by simply clamping, soil - the base.)...
If now, with this rod, build an arc, with the help of a string (tying rampant) would observe that as to shake our hand oscillation of the rod will be the same at its top, and its base.
That zero deflection of the vertical axis of the rod, when zero deformations and faults in construction.
For the third case now.
If you have a stick and put it horizontally on two bricks that wood be supported at its ends.
If we give the wood one punch (karate) will hurt a little, but eventually the wood will break in two.
If you now push the wood with a big vise, at its ends, and give a punch .... the wood will break your hand
So does the pretension on the pillars or walls ... powerful sections with respect to the cutting.
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