The acceleration of the ground, the mass of the structure, and the height of the mass from the ground, are the three factors that create the magnitude of the lateral seismic force. This lateral seismic force tends to overturn the walls of the building. The walls of the high-rise floors are rigid, and drop heavy torques at the base. Question If, with unrelated tendons, we apply pre-tension to a wall between, the upper ends of its sides and the foundation ground, then, it will lower torques at the base;
I believe that torque does not exist at the base, only with compressive intensities at the two opposite ends of the wall (up - down). In order to have torque at the base, one side must be stretched. There is no tension because the unrelated tendon picks it up from the top and deflects it into the ground.
If force from tendons will be applied in the wall axis (without eccentricity), compressive stresses should increase, but not bending monents (torques) at the base.
https://www.researchgate.net/post/Why_not_remove_large_bases_in_width_by_replacing_them_with_deep_bases
Dear Piotr Bętkowski
BENDING TORQUE AND OVERTURNING TORQUE
All torques come from the lateral force of the earthquake or the wind in the construction.
Any change in the vertical axis of the walls either by bending or by overturning also affects the curvature of the beam logs since they are connected at the nodes. If by pre-tensioning on the sides of the walls we reduce the bending, and by lowering the walls to the ground, we prevent their overturning before the stresses go to the beams, the beams will take on less tension.
However, each construction reacts differently.
1) If the construction is not high and has elongated walls properly dimensioned, then the base is large on its own anyway (due to double lever arm) and the elasticity - bending moment is very small.
2) In these large elongated walls if we add piles below the base then we further strengthen the reaction of the wall to the overturning.
3) The piles have resistance to the compressive loads of the construction, but very low strength (in soft soils) in terms of traction. In order to receive both the traction and to prevent the wall from tipping over, we need to make piles that have the ability to expand (like swivels) and anchor strongly to the ground and the rock, taking on greater traction and compression forces.
4) If with expansion piles, we fasten the base of the wall on both sides, it is impossible to overturn it
5) If instead of fastening the base with expansion piles, we create pre-tension on the sides of the walls between the top edge of the wall and the expansion piles, then we have prevent both wall overturning and bending moment.
This means zero deformation in the wall trunk, zero torques at the joints and avoiding tipping over. That is, we defeated the earthquake.
What am I trying to stop with the method of seismic planning that I propose?
I try to stop the distortion. That is, the inelastic displacement.
I try to stop the moments at the nodes that break the cross sections that create the node.
I try to strengthen the loose foundation ground.
I achieve all this by pre-tensioning + anchoring all the sides of the walls with the foundation ground.
If the earthquake is large and lasts and coincides, the construction period and the ground and coordination occurs, then no regulation is sufficient to deal with it without at least serious damage to the construction.
Only the design method I suggest. It can even stop the coordination of the construction in each charging cycle.
There are too many unbalanced factors that can cause disaster in most modern seismic structures.
Basically, the factors that determine the seismic behavior of structures are numerous, and in part probable. (The direction of the earthquake is unknown, the exact content of the seismic excitation frequencies is unknown, its duration is unknown.) Even the maximum possible accelerations given by seismologists, and determine the seismic design factor, have a probability of exceeding more than 10%.
The correlation of quantities such as "inertial stresses - damping forces - elastic forces - dynamic construction characteristics - construction ground interaction - imposed ground motion" is non-linear.
According to modern regulations, the seismic design of buildings is based on the requirements of adequate design and plasticity.
The inevitable inelastic behavior under strong seismic excitation is directed at selected elements and failure mechanisms.
In particular, the lack of adequate design of the nodes and the clearly limited plasticity of the elements lead to fragile forms of failure. The purpose of modern seismic regulation is to build structures that:
a) In frequent earthquakes with a high probability of occurrence will not suffer anything,
b) In medium probability earthquakes will suffer small, repairable damage and
c) In very strong earthquakes with a small probability of happen we will not have loss of human lives.
So we should not use the term "absolutely" in seismic constructions.
We should use the term "quality" constructions which means application of at least the requirements of all modern regulations.
The quality of constructions and their safety is also a function of the economic situation of the countries, among other factors.
Understandably, poor countries cannot be compared to countries with strict modern anti-seismic regulations.
Conclusion… there is no absolute seismic design today, and we should not refer to absolute seismic design.
So there is a great need today to invent a more modern anti-seismic design that meets the ultimate anti-seismic design, with lower construction costs.
And that represents the design method I suggest.
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