Simply put. A reinforced concrete structure consists of vertical parts ( columns, walls, large walls, shafts ) and horizontal parts ( beams and slabs ) connected at the nodes.
In an earthquake the inertia of the slab and beams creates a lateral force which pushes the walls and columns
The walls and columns resist this lateral force which tries to overturn them on one side and bend them on the other.
Their reaction to bending is due to their connection to the beams at the nodes to prevent them from overturning and to the reaction of their trunk to prevent them from bending.
So the dynamics of the walls and columns are due to the strength of their cross-section and the strength of the beams.
Walls and columns primarily have a tendency to overturn but they are held by the beams and then the trunk starts to bend.
The bending moment and the overturning moment of the walls create moments at the nodes which deform the beam trunk and break it.
Here we see that the reaction of the structure to the earthquake comes from the wall and beam cross sections around the nodes.
In large earthquakes this reaction is not enough and the cross sections usually of the beams break.
Another failure can come from wall buckling and from inadequate strength of the materials.
So then we have a big problem because the walls are failing. If the beams fail, the house doesn't fall because the reinforcement holds it together.
But if the walls fail and even if the crack is oblique the house will collapse.
This is why civil engineers build weaker beams so that they break first and energy is dissipated.
And I come up with the following suggestion.
In order for a structure not to collapse in an earthquake, it must
1.Increase the strength of the cross-sections without increasing the mass.
2.Stop the bending of the walls which breaks them and transfers moments to the nodes and also breaks the beams
3.Stop the bending of the walls that breaks the beams.
If the walls have strong cross sections and do not break, if they do not bend, and if they do not overturn, then they will not break the beams.
So then we'll have defeated the earthquake.
To make the wall frame strong so it doesn't break and bend, I apply compression to both ends by applying pre-tension with tendons and hydraulic jacks.
To keep the walls from toppling, the same pre-tension tendons that apply compression are, for the first time in the world, embedded into the earth's soil using a large twist-off.
In this way the wall is self-contained and does not need the beams to prevent it from overturning and bending.
On the other hand, the beams are not stressed by the bending and twisting of the wall, so they do not break.
For the first time the ground participates in receiving the forces of inertia by preventing 80% of the earthquake tensions circulating in the body of the load-bearing structure.
It also increases the wall strength by 31% with respect to the base shear stress.
Maybe if you paint the walls it will improve their kinetic strength. But don't try pink paint because it will make people think they are in Florida.
Dear Dr. James E. Larsen
I'm not aware of any seismic coloring. But I do have data on prestressing in conjunction with the ground bearing of the tendons placed at the ends of the walls which I am submitting.
1. Elasticity vs Stiffness
I agree that elasticity and stiffness have opposing characteristics, which is why a collaborative approach is required. My proposal is based on creating independent systems: an elastic structural frame for energy absorption and a rigid wall system that is fully anchored to the ground. This ensures:
- Distribution of seismic energy in two phases: initial absorption by the elastic frame and displacement limitation by the rigid system.
- Instead of competition between the two systems, there is cooperation.
2. Moments at Connections
It is true that stiffness increases moments at the connections. However, my proposal addresses this issue through:
- Relieving the walls of static loads: The walls take on only seismic forces, reducing compressive stresses.
- Absorbing moments in the ground: Anchoring the walls to the ground diverts the moments, protecting beams and joints.
This way, the accumulation of moments at the connections is avoided.
3. Uneven Participation of Columns and Walls
You correctly highlight the problem of uneven load distribution when elastic columns and rigid walls are combined. In my proposal:
- The two systems are completely independent. They do not share loads but cooperate through controlled collision within the gap using elastic material.
- The elastic material acts as a damper, minimizing uneven distribution and reducing stresses on the walls.
4. Anchoring Proposal
Anchoring the walls to the ground offers the following benefits:
- Increased load-bearing capacity of the ground through compaction and anchoring.
- Deflection of seismic moments into the ground, reducing stress on other structural elements.
- Enhanced overall dynamic response of the structure.
5. Innovative Seismic Design
My proposal to use independent systems specifically addresses the issues you mentioned:
- The elastic structural frame absorbs energy, protecting joints from excessive stresses.
- The rigid system provides stability and strength, preventing large displacements.
- The combination of these elements achieves:Balanced load distribution. Reduced need for over-dimensioning structural elements. Improved overall performance under seismic conditions.
6. Documentation and Calculations
I am happy to present detailed calculations for:
- The reduction of moments at joints through anchoring.
- The increase in the load-bearing capacity of the ground.
- The balance of displacements and improved cooperation between elastic and rigid systems.
Thank you for the opportunity to present my proposal in more detail. I look forward to continuing this discussion.
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