Critical failure area is the cross-sectional area of a rod that breaks when bent.
In this area that breaks, a compressive tension is created on one side of the rod and a tensile tension on the other side.
We know that the compressive tendency is created when two opposing forces tend to compress a body and the tension is created when two opposing forces tend to lengthen a body.
Let's take the tensile. We said opposite forces in a different direction. Nice!
Somewhere at the point of intersection of the rope these opposing forces must separate their direction. If a rope is pulled by 10 people at one end and ten other people at the other end, the rope will break in the middle between these two groups of people.
This area where the rope will break is the critical failure area.
The critical failure area receives the greatest stresses and is the point at which the opposite tensile forces separate their direction to lengthen the body.
That is, if two groups of people pull a rope, another is the direction of the forces of these people pulling from the right and another of these people pulling from the left.
The rope - reinforcing steel, is very strong because it withstands tensile.
The hands try to pull the rope and if the force is great they can not because they can not withstand the friction or otherwise the shear stresses that develop on the surface of the rope and hands.
That is, the mechanism of relevance is destroyed by the high resistance of the rope (or reinforcing steel) to tension.
What does Potential Difference mean?
The friction between the hands and the rope as well as the force developed on the left side where only one person pulls one end of the rope is not the same as that developed on the right side when more people pull. So there is a potential difference in the forces and the mechanism of relevance.
Relevance
The cooperation between concrete and steel is achieved through the mechanism of relevance. When we say the mechanism of relevance we mean the combined action of the mechanisms which prevent the relative sliding between the bars of the steel reinforcement and the concrete that surrounds them. The mechanism of the connection consists of the adhesion, the friction and in the case of steel bars with embossed shape, the resistance of the concrete which is trapped between the ribs. <The combined action of these mechanisms creates a radial development of shear stresses applied to the concrete and steel interface.> When these stresses reach their limit value, the correlation mechanism is destroyed, with the concrete breaking along the steel bars, and the steel detaching from the concrete.
After what has been mentioned above, let 's talk practically It is often more difficult in a research to identify problems than to find the solution. Steel withstands tensile and concrete withstands mechanical compression.
A reinforced concrete wall when it receives lateral external seismic loads creates a force of its overturning and a bend in its trunk.
In both cases of bending and compression, one side of the wall receives compressive loads and the other side tensile loads.
The concrete takes the compression on one side of the wall and the steel the tension on the other side of the wall.
The cooperation of concrete and steel is achieved through the mechanism of relevance.
Shear stresses are created on the interface of the two materials.
Here we see that the concrete receives the compressive strengths of the wall but also receives strong shear stresses from the steel that pulls it.
The question is whether the concrete withstands the strong shear stresses imposed on it by the pull of steel? No it can not withstand and for this reason we have the pulling or otherwise slipping of steel through the concrete, and the destruction of the coating concrete around the steel.
That is, if you put steel in butter, there will never be cooperation because butter does not withstand the pull of steel.
If you put more pieces of steel in the butter or concrete you will have greater strength; Is it a Question?
Bending always creates tension on one side of the wall, and a critical area of failure.
What do we mean by critical failure area? Mechanical stress is created when two forces are opposite and tend to compress the body and tensile is created when two opposite forces tend to lengthen the body. The critical failure area is the area where the compressive and tensile forces separate their direction.
In this area of the wall cross-section (the critical failure area) the maximum intensities are created and the result is that the failure is created in this area.
In a beam the main critical area of failure due to bending, appears in its center while in a high-rise construction of a high-rise building the critical area of failure appears in the cross section of the wall near the base.
This means that there is a potential difference in the adhesion of concrete and steel as well as the forces are greater, from the critical failure zone and above that of the critical failure zone and below.
It is as if we have ten people pulling a rope on one side and one person pulling on the other. Potential difference is created at both ends of the rope in friction and traction
Combine now the potential difference I mentioned, with the inability of the concrete to absorb the shear forces that develop on the steel and concrete surface, to understand the inability of the two materials to work together, which use the co-operation mechanism of relevance.
There is something worse that develops on the walls, and that is the lever arm mechanism, created by the relevance mechanism.
Lever arm is any pillar or wall that extends from the base to the roof. We know that the lever arm of the wall, lowers large torques at the base which are impossible to receive without failing the lower cross sections of the load-bearing elements.
Conclusion
1) The multiplication of the stresses created by the wall lever arm mechanism, 2) in combination with the difference in traction potential and the difference in forces developed around the critical failure area and 3) the inability of the concrete to pick up the Shear forces developed on the concrete and steel surface create a combined explosive failure resulting in the destruction of the the mechanism of relevance. The shear failure occurs both in the coating concrete and in the entire cross section of the wall near the base. See the photo.
The forces that develop in the structure during the oscillation caused by the earthquake, exist but appear as a result of the failure. The response of structures to seismic shifts depends on where we plan to deflect or otherwise drive the developing seismic forces. Modern seismic design regulations use cross-sections of load-bearing elements to resist seismic forces.
That is, they send forces to the cross sections. If the earthquake has a high acceleration and duration and the construction does not have mechanisms for damping seismic energy, then the construction will not stand in this earthquake.
It is a design error of modern regulations to direct seismic forces only on the cross sections of the bearing elements. Some of the seismic forces could be absorbed by mechanisms that convert seismic kinetic energy into thermal energy and designed to deflect seismic forces out of the structure by driving them into the foundation soil. This design requires union all the upper edges of the siding walls, with the foundation soil, using anchoring and seismic damping mechanisms. ( two in one )
This design method could work together with the cross sections of the supporting elements to increase the response of the structure to seismic forces.
The solution to the mentioned problems
There are two main forces that contribute to the destruction of the building. The others are their components. One force comes from the earthquake, which the earthquake imposes on the structure down at its base because it displaces it with an acceleration (a) and the other from the inertia of the mass of the building. These two forces together create the overthrow of the walls and even the overthrow of the whole building, which I try to stop by imposing opposing forces with the help of the anchoring mechanism, which forces the anchoring mechanism take them from the ground.
See the figure.
The displacement of the ground (A) creates the inertia force (B) which creates the overturning moment of the wall (Γ) with the help of the joint which allows the rotation. This tipping moment creates two forces. The force (1) which is directed through the cross section of the wall diagonally down to the joint and balances with the reaction of the ground The other force is upward (2) and rises from the cross section of the other side of the wall. The upward force (2) contrasts with the static loads of the structure and creates tensile strength.
I place a tendon (3) which freely penetrates the side of the wall as well as the length of a bore under the sole of the base. The lower end of the tendon is anchored to the ground using an anchoring mechanism, and the upper end of the tendon is anchored to the top level of the side of the wall with a screw.
I take a force from the ground and transfer it to the highest level of the wall of the wall so that this force opposes the upward force (2) and prevents the wall from tipping over and its trunk from bending. This stops the deformation of the whole construction.
If we control the deformation we will not have failures. It is like putting a finger on the top of the wall to stop the wall from tipping over. If it is useful we can impose prestressing loads on the cross section of the wall. But this is not very necessary if we do not want to lose plasticity or part of it. Without tension there is no bending, there is no critical failure area.
Without relevance there is no shear failure (on the concrete-steel surface) due to the tensile strength of the steel. Without torque of the wall and bending of the trunk, there are no large moments in the nodes. There is no longer a potential difference.
Concrete receives only compressive forces and steel only tensile forces.
With the method of designing, prestressing and anchoring the sides of the walls from their upper ends to the foundation ground, using unrelated tendons, which at the ends have ground anchoring mechanisms as well as prestressing mechanisms, I hope to change the direction of forces and to transport them through the tendons and the vertical large and strong cross-sections of the walls into the ground, preventing them from turning and bending the trunk, which cause the deformation of the bearing organism which is directly connected with the construction failures in the earthquake. In any case, this extra reaction that the cross-sections need to successfully deal with the earthquake could be derived from the proposed design methodology.
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