NL9401418A - Sand skeleton in hydraulic, toroidal earthquake buffer, functioning as a carrier as long as the earth is at rest under the buffer. - Google Patents

Description

Sand skeleton in hydraulic, toroidal earthquake buffer, functioning as a carrier as long as the earth is at rest under the buffer.

The invention relates to an essential improvement of the toroidal earthquake buffer as described in U.S. patent 4,887,398, in which buffer transverse forces due to wind loading cause the supported structure to drift within the buffer-tolerated soil displacement limits.

The sand skeleton according to the invention is built up between the pressure plate and the base plate, by filling the drum-shaped space between them with a water-sand compound, which does not take place after filling with water. By now allowing so much water to escape through the valves that the pressure plate rests on the sand bed, a tight skeletal structure is formed, so that it is as if the building rests entirely on sand.

However, the sand skeleton is immediately disturbed by vibrations and shocks; the "package" collapses, as it were, and behaves through the turbulent water column under hydraulic pressure, as buoyant, running or tumbling sand, depending on the type of sand used. Blowing sand - this is very fine sand mixed with loam - is particularly suitable for this.

Similar conditions as achieved artificially in the so-called torus buffer according to the said US patent can also arise spontaneously and often without human intervention, due to the specific soil conditions under a building. If such situations occur, there is always a situation that is not or very difficult to control, which can have a counterproductive effect under a combination of unfavorable factors, namely: arbitrary structural differences under the various supports of the foundation and the non-centripetal imposition. , in no way guarantee a homogeneous, load-bearing soil, nor that the building is protected from permanent deformation. The sand skeleton according to the invention, however, meets these drawbacks, but can also be repaired after every earthquake, if not spontaneously, by water and / or sand replacement or by hydraulic reformation with simultaneous lifting of the foundation. Namely, after subsequent tapping, the pressure plate of the hydraulic toroidal buffer spring will rest on the sand skeleton. Since the formation of a sand or grain skeleton is sufficiently known from the literature, this patent application will not go into this further.

An additional and, under certain circumstances, equal advantage of the sand skeleton between the pressure plate and the base plate of the torus buffer according to the aforementioned US patent is the vandalism or sabotage-preventive effect. Deliberate damage to the buffer does not cause the support to subside. This makes it especially sensory objection to the use of the so-called torus buffer obviated. This is emotional because recent acts of sabotage under the foundations of structures have shown that malicious people with explosives can also cause rigid foundations to collapse, while, if only destructive targets are intended, the damage caused above the foundation is considerably easier.

It will be clear that the toroidal buffer provided with this invention according to said US patent does not lose its effectiveness, because the water-sand compound behaves like a liquid during quakes and only forms a skeleton when the earth is at rest.

During a quake, some of the energy of movement in the hydraulic buffer will be converted into heat, mainly by fluid friction. Although the temperature gradient is relatively small, due to expansion of the solid and liquid components, the printing plate will undergo a vertical displacement; in other words, the drum-shaped space between the fixed top or printing plate and the shape-changing base or bottom plate, is enlarged within the imaginary cylinder jacket by a radius equal to the radius of the printing plate. This increase in volume will allow the settling sand to form a layer under the pressure plate which is as thick as the original or substantially as thick.

In most cases, therefore, artificial restoration of the layer thickness for the purpose of the sand skeleton can be omitted.

If this is nevertheless necessary, this can be done by lifting the pressure plate by temporary water replenishment, followed by hydraulic or mechanical reformation by the two valves arranged on the torus, which make a larger passage especially desirable for this purpose. Because the compressibility of a water-sand compound is low, in practice the temporary lifting will only be a few millimeters and will not affect the supported structure, at least not to an extent that causes damage to the structure.

The invention will be elucidated on the basis of the drawing, which represents a cross-section over the torus buffer according to US patent 4,887,398, with a sand skeleton built up under the pressure plate.

The sand skeleton 1, being a compressed and consolidated primer layer of a given composition compressed by the pressure plate 2, remains intact as long as no significant forces act in the horizontal plane 3. In order to promote the construction of the sand skeleton 1, the toroidal space 4 also partly filled with sand. The saucer-shaped cross-section of this torus 4 and its large radius 5 will force the sand 6 in the direction of the pressure plate 2 during an earthquake. Depending on the floating components and grain size, but also on the specific gravity of the solid components in the sand 6, over time, but in any case quite soon after the quake, sufficient sand 6 will have settled, after the pressure plate 2, to restore the sand skeleton 1.

Very gradually acting transverse forces as a result of wind load 7, during the load increase from zero to maximum, the skeleton 1 will continuously enable the equilibrium condition of gripping and reaction forces to be met, because the occurring shear stresses can be assumed from the grain stresses present perpendicular to the surface considered in the sand skeleton 1. Moreover, due to the horizontal component 8 of the directionally and magnitude of the engaging force 9 on the skeleton 1, also in a direction parallel to the horizontal pressure component 8, compression of the sand 6 will occur, because the gradualness of that engagement force due to the wind load 7 permits this. The compression proceeds quite differently if the factor "time" in the time-settlement course is negligibly small and there is no question of "settlement", which is the case during earthquakes or earthquakes. In that case, the eigengen mass inertia of the structure 10 supported by the buffers prevents it from following the movements of the ground 11 under the buffer 12, due to the low liquid friction between the pressure plate 2 and the shape-changing, flexible and adaptable to the bottom profile. base plate 13.

As soon as the sand skeleton 1 is disturbed, the spaces bounded by the torus 4 and the top plate or pressure plate 2, together with the bottom plate 13, can communicate freely with each other. This unobstructed communication is not affected by any inclination of the flexible bottom plate 13 with respect to the printing plate 2.

In order to prevent the pressure plate 2 from coming into contact with the bottom plate 13 during a violent earthquake, the skeleton 1 and the distance between the plates determined thereby must be sufficient.

The sand skeleton according to the invention can be used with particular advantage for buffering pillars under bridges and viaducts, because without this provision the toroidal buffer could, due to the joint centrifugal force of the traffic in curves, create an unacceptable tensile stress in the attachments, which the sand skeleton 1 is prevented.

Also with a view to the "drift effect", the sand skeleton is not necessary, but still very desirable.

The filling 14 serves to prevent displacement of the foundation 10 over the pressure plate 2.

Claims (6)

Sand skeleton in hydraulic, toroidal earthquake buffer, as defined in U.S. Patent 4,887,398, characterized in that the supporting skeleton is disrupted by tremors or vibrations under the buffer and functions thereon as a liquid until the earth is at rest again and the skeleton recovers over time, whether or not in combination with artificial reformation. At rest, however, the support is stable and is not affected by wind force, at least not to the extent that the supported structure or technical work of art becomes adrift about the amplitude permitted by the toroidal buffer. Skeleton according to claim 1, characterized in that instead of sand, another granular substance serves to form the load-absorbing member in the absence of earthquakes. Skeleton according to claim 1, characterized in that a fluid substance replaces the water and also serves to form the load-absorbing member in the absence of earthquakes. In distinction from a solids that behave as a liquid in general, the fluid has all the features of the specific sand skeleton structure, except for granular dimensions. Skeleton according to claim 3, characterized in that the air is evacuated from the toroidal buffer and the ambient pressure compresses the mass into a solid, compact member, which is aerated by tremors or vibrations via a rupture disc or otherwise and immediately as liquid again while such a solution can for instance be used advantageously if the wind load on the structure to be supported is disproportionately large in relation to its cross-section over the base. Sand skeleton according to claim 1, characterized in that antifreeze is added. Sand skeleton according to claim 1, characterized in that a heating source prevents freezing.