Post-tensioning at the edges of the walls and embedding the tendons in the foundation soil.
Ground acceleration creates inertia of the mass, inertia with height and articulation create torque, torque creates rotation.
But what does the torque rotate? Does it rotate the entire building or does it rotate the walls and columns?
There are the walls and columns that are vertical and there are the beams and slabs that are horizontal.
All of them are connected together at the nodes.
The rotation of the trunk of the walls also lifts the beams upwards.
If the beams resist lifting the building and turning it around on itself then there will be building overturning.
Usually this overturning occurs in buildings with very small footprints, many floors and with strong walls and beams.
But if the walls and beams do not have the strength to rotate the building, then the entire area of the base of the building remains on the ground and what rotates is each wall and column of the structure, sometimes to the right and sometimes to the left.
This wall rotation breaks the beams and the building collapses.
The elastic or inelastic deformation of the frame of the walls and columns affects and elastically or inelastically deforms the beams to which they are connected at the nodes and is the second reason for the deformation of the beams that cause them to break and the structure to fall. So 1. the bending of the walls and columns and 2. the elastic or inelastic bending of the trusses is what breaks the beams.
If we want to stop the collapse of structures we must do the following.
1.Embed the walls in the foundation soil with ground anchors to stop them from rotating and breaking the beams.
2.We need to apply artificial compression to the walls, through post tensioning, to make them stiff to prevent them from easily deforming and transferring moments to the beams, and dynamic to resist the moments.
These are two simple things I do, and it is my recommendation that civil engineers do them as well, and no structure will ever be brought down by an earthquake again.
To embed in the ground we need strong anchors and I am trying to perfect these experimentally.
https://www.youtube.com/watch?v=XsHC9WJwgyU&t=450s
https://www.youtube.com/watch?v=3Tc-otj0E7g
Dear Doctor
I do hope you read this article as as I see notable contribution and do wait your opinions.
Go To
Seismic behavior of unbonded post-tension wall with replaceable energy dissipator
Peng Mi , Ping Tan , Yiming Li , Xiaofeng Zhao , Mengxiong Tang
Soil Dynamics and Earthquake Engineering
Volume 166, March 2023, 107737
https://doi.org/10.1016/j.soildyn.2022.107737
[Abstract
Unbonded post-tension (UPT) precast concrete shear walls achieve better recentering capacity with little residual drift but less energy dissipation capability. To improve the situation, a steel-reinforced UPT precast concrete wall with replaceable low-yield-point steel plates as energy dissipators (PEWs) is developed. The proposed wall is a load bearing-energy dissipation dual function system with two seismic lines of defense. A design approach is proposed to determine the damper force under a certain energy-dissipation moment ratios. The wall behavior is analyzed concerning four performance states under combined gravitational and lateral loads using an elaborate fiber model developed in OpenSsees. Lateral bearing yield strength and peak resistance increased under monotonic and cyclic loading respectively. All the relative energy-dissipation ratios of the PEW at different cycles are greater than 0.125, as recommended by ACI ITG T5.1. The performances of two eight-story frame shear wall structures with and without energy dissipators devices subjected to 22 the maximum considered earthquake records are compared. The base shear forces, roof displacement response and story drift of the PEW reduced significantly. The PEW specimens exhibited superior behavior in terms of lateral resistance and energy dissipation.]
Dear Dr. Sundus F Hantoosh
Rocking Wall Design and the ultimate seismic system I am proposing look the same but they are very different because they have basic differences in their operation.
Rocking Walls create energy dissipation by creating openings in the tread of the wall replacing the leaks and plastic joints of conventional housing. Also at the nodes they create joints replacing the dips of conventional buildings to create and wrestling openings at the junction of the node replacing the leaks and plastic joints of conventional housing in the beams. Basically Rocking Walls seek energy dissipation without failures in the structural elements.
The ultimate seismic system allows for neither plastic joints nor openings in the wall tread. It does not allow any inelastic failure at any large acceleration.
It does not change the existing seismic design, but enhances it.
Key differences between Rocking Wall and the absolute seismic system are.
1.Rocking Walls create energy dissipation by creating openings in the tread of the wall replacing the leaks and plastic joints of conventional housing.
1.α. The absolute seismic system allows neither plastic joints nor openings in the tread of the wall because the post-tensioning at the ends of the wall stringers makes them rigid, while increasing their dynamic and load-bearing capacity without increasing the mass. Setting the wall on the ground along with the wall tie beams stops the wall from recoiling, and transferring the moments to the nodes.
The design method of applying artificial compression to the ends of all longitudinal reinforced concrete walls and, at the same time, connecting the ends of the walls to the ground using ground anchors placed at the depths of the boreholes, transfers the inertial stresses of the structure in the ground, which reacts as an external force in the structure’s response to seismic displacements. The wall with the artificial compression acquires dynamic, larger active cross-section and high axial and torsional stiffness, preventing all failures caused by inelastic deformation. By connecting the ends of all walls to the ground, we control the eigenfrequency of the structure and the ground during each seismic loading cycle, preventing inelastic displacements. At the same time, we ensure the strong bearing capacity of the foundation soil and the structure. By designing the walls correctly and placing them in proper locations, we prevent the torsional flexural buckling that occurs in asymmetrical floor plans, and metal and tall structures. Compression of the wall sections at the ends and their anchoring to the ground mitigates the transfer of deformations to the connection nodes, strengthens the wall section in terms of base shear force and shear stress of the sections, and increases the strength of the cross-sections to the tensile at the ends of the walls by introducing counteractive forces. The use of tendons within the ducts prevents longitudinal shear in the overlay concrete, while anchoring the walls to the foundation not only dissipates inertial forces to the ground but also prevents rotation of the walls, thus maintaining the structural integrity of the beams. The prestressing at the bilateral ends of the walls restores the structure to its original position even inelastic displacements by closing the opening of the developing cracks.
All of these in the proposed method have greater performance when placed in shear precast walls than when placed in an elastic support with columns.
As you can see in this video experiment on the rocking table, there is neither failure nor base recall https://www.youtube.com/watch?v=Q6og4VWFcGA&t=6s
When I want to apply seismic energy dissipation I apply other design methods.
This design method https://www.youtube.com/watch?v=IO6MxxH0lMU&t=37s includes a flexible structure with columns and within or outside this flexible structure we place one or more independent rigid wall structures with appropriately shaped plan cross-sections and with prestressed ends connected to the ground.
We place horizontal seismic isolation at the base to prevent high accelerations.
We place strong damping tyres for the smooth absorption of the impact between the diaphragms of the slabs and the walls which occurs due to the difference in the displacement phase of the two independent structures.
In this method, the displacements of the two independent structures cancel each other out reason of impact, and the inelastic deformation of the elastic structure with columns it is prevented.
At their upper ends, the walls have hydraulic jacks connected to the prestressing tendons. When the wall tends to deform due to displacement, the fluids in the hydraulic jacks are heated because they prevent deformation by converting the kinetic force of displacement into heat, creating a smooth elastic seismic damping.
The diversion of seismic forces to the ground and the high stiffness of the walls and the bearing capacity of the foundation soil is given and is due to the pre-stressing and the connection of the edges of the walls to the ground.
More
https://www.scirp.org/journal/paperinformation?paperid=130175
Dear Dr. Sundus F Hantoosh
Questions Answers why I do this and not that
1.Why am I pressing the wall into the foundation soil?
Answer. To stop it from turning around its base. The turning of the wall occurs when it receives the lateral force of inertia of the floors. The magnitude of this torque force that rotates the wall depends on the weight of the mass, the height at which the mass is located, and the acceleration of the ground displacement under the structure. the rotation of the wall breaks the beams to which it is connected at the nodes. If we do not want to break the beams, we must stop the wall from bending. I accomplish this by embedding all the ends of the wall with mechanical anchors to the ground.
And even the ground compacting with expanding anchors, compacts the soil in all directions increasing the bearing capacity of the soil before the construction is done. The borehole that we drill before placing the anchor mechanism also reveals the quality of the soil and any hazards such as hidden caves under the footings.
2.Why am I pressing the wall into the foundation ground using anchors and not pressing it into the base with the connecting beam and cavity?
Answer. Civil engineers to stop the wall from bending press the wall into the base with the tie beam, joists and cavity paving. In large earthquakes the moments that the stiff wall is lowered and called upon to take up by the connecting beam and joists are too great, causing the connecting beams and joists to break and the house to collapse.
Does the footing with the connecting beam stop the bending of the wall? Yes, it stops it up to 0.36g and that's a lot to say.
From 0.36g to 3g, which is the acceleration of the earthquake, the connecting beam breaks easily.
Imagine a six-storey building of 100 sq m area with an acceleration of 1g is subjected to a lateral force equal to four times the total weight of the building, and the moment that the wall is lowered and the connecting beam is called upon to take up is 18 times the lateral force of the earthquake.
The footing in the ground that I apply with ground anchors sends these wall-down moments into the ground and dissipates them.
The footing of the wall with in the connecting beams and girders sends the moments into their cross sections and breaks them.
When we say footing in the ground we mean that the ground as an external force participates in the response of the bearing capacity of the structure to the earthquake. Without anchorage the ground does not participate and all the moments are directed to the cross sections at the nodes. With the ground anchorage the downward moments are shared with the connecting beams and girders, doubling the earthquake bearing capacity of the structure.
3.Why do I then apply tension to all ends of the walls?
Answer
Deformation of the beams is not only caused by the wall rotation but also by the bending moment which bends the wall members and this bending is transferred to the beams to which they are connected at the nodes. The bending moment also stresses the wall itself with tensile stresses which are transformed into cracks. If we want to eliminate the cracks in the walls and beams, we have to eliminate, together with the overturning moment of the walls, the deformation of their frames caused by the bending moment.
Bending without the presence of tension does not exist. So if we want to make the wall more rigid and dynamic without increasing its mass, which incidentally increases the earthquake loads, we have to balance the tensile stresses with artificially imposed compressive stresses on the wall sections. I do this by post tensioning and stopping the large deformation in the wall and beam frames.
In addition to failures due to bending moment, the walls have other failures due to shear forces acting on the wall frames. One such large force is the base shear which cuts the wall cross-section like scissors near the base and has a force equal to the force of inertia of the structure. Another shear force occurs at the concrete and steel interface when the steel starts to flex which breaks the concrete overlay and thus the steel and concrete cooperation is rendered useless and the structure collapses. Other similar shear stresses occur originating from the oblique tension in the wall sections, which result in the oblique shear failure of the wall section. All these shear stresses create shallow oblique and transverse cracks and failures in the concrete overlay. Post-tensioning increases the frictional strength of the concrete and neutralizes these shear forces as well as those that destroy the concrete and steel cooperation.
4.Why don't I apply only one post tensioning in the center of the walls?
Answer
I have to apply only one post tensioning in the centre of the columns because of their square cross-section.
Elongated walls have two lever arms The one of height which multiplies the overturning and bending moments, and the one of width which reduces the overturning and bending moments.
I do this both to reduce the moments that the ground anchors have to take and to more easily reduce the bending moment .
Если не брать в расчет ударную нагрузку, а только упругие колебания. то нужно делать конструкцию предотвращающую наклон здания и его раскачивание. Т.е. фундамент должен быть плавающим.
Dear Dr. s. N. Mulev
2.1. Methods of Anti Seismic Building Design
There are two options for seismic design using the proposed method.
1) Absolute dynamic design.
2) Dynamic design combined with seismic damping mechanisms.
1) Absolute dynamic design methods using longitudinal walls prestressed and anchored at their ends to the foundation soil by expanding piles [1] [2] .
The longitudinal walls are large rigid lever arms at height which multiply to the maximum the downward moments at the base, compared to the elastic columns. However, in addition to the height lever arm, the walls also have a width lever arm which reduces the overturning moments, and the columns do not have this width lever arm, nor do they have a large dynamics. The width lever is a major advantage of the walls because it greatly reduces the overturning forces that the method’s mechanisms have to absorb, as well as the cost of application, since it reduces the anchoring operations on the ground.
As the simulation showed, the prestressing of the vertical support elements increases the load bearing capacity of the structure and their capacity to shear reaction to the base.
2) Dynamic design combined with seismic damping mechanisms.
The main dilemma facing a structural engineer tasked with ensuring superior seismic resistance of a building is how to minimize the acceleration of the floors. Large displacements between floors cause damage to non-structural elements and to the structural elements that connect floors together. Deformations can be minimized by stiffening the structure, achieved through the use of walls, but this leads to an amplification of ground motion, which leads to high floor accelerations that can damage sensitive interior equipment and the structure. The installation of many strong walls results, due to their high stiffness, in a significant reduction of the fundamental eigenmodes of the structure. This, combined with the q = 1 consideration, leads to a correspondingly large increase in the seismic loads of the structure. In this respect, it should not be overlooked that it is precisely because of the many strong walls that the strength of the section increases in seismic loads. High accelerations contribute to damage to sensitive internal equipment and structure.
The acceleration of floors can be reduced by making the system more flexible, but this leads to large movements between floors. The only practical way to reduce the mentioned problems is discussed below.
There are five factors that increase the earthquake loads on a structure.
1) Ground acceleration;
2) Mass weight;
3) Mass height;
4) Ground—structural coordination;
5) Duration.
These factors increase the earthquake loads on a structure. The structure must counter these forces with proportional compensating forces and the materials must have the necessary strength to receive them.
Still, various other techniques dampen the displacements by reducing the deformation that causes inelastic failures and deflecting the inertia forces into the ground.
These seismic design techniques will be discussed in my next proposal.
This design method [3] includes a flexible structure with columns and within or outside this flexible structure we place one or more independent rigid wall structures with appropriately shaped plan cross-sections and with prestressed ends connected to the ground.
We place horizontal seismic isolation at the base to prevent high accelerations.
We place strong damping tyres for the smooth absorption of the impact between the diaphragms of the slabs and the walls which occurs due to the difference in the displacement phase of the two independent structures.
In this method, the displacements of the two independent structures cancel each other out reason of impact, and the inelastic deformation of the elastic structure with columns it is prevented.
At their upper ends, the walls have hydraulic jacks connected to the prestressing tendons. When the wall tends to deform due to displacement, the fluids in the hydraulic jacks are heated because they prevent deformation by converting the kinetic force of displacement into heat, creating a smooth elastic seismic damping.
The diversion of seismic forces to the ground and the high stiffness of the walls and the bearing capacity of the foundation soil is given and is due to the pre-stressing and the connection of the edges of the walls to the ground. Article The Ultimate Anti-Seismic Design Method
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