WO1996007000A1

WO1996007000A1 - Sand-skeleton in hydraulic torus buffer, functioning by way of supporting element as long as the protected structure is subjected to wind load only and no earthquake exists

Info

Publication number: WO1996007000A1
Application number: PCT/NL1995/000290
Authority: WO
Inventors: Hendrik Lenten
Original assignee: Hendrik Lenten
Priority date: 1994-08-31
Filing date: 1995-08-30
Publication date: 1996-03-07
Also published as: NL9401418A; AU3266695A

Abstract

The invention is intended to improve the so-called hydraulic torus buffer as described for example in the USA-patent 4,887,398, in such a way that the horizontal soil movements during earthquakes do not affect the supported building (10), but wind load cannot effectuate breaking adrift due to a consolidated sand-skeleton (1) inside, bearing the structure (10) in the absence of wind load. The skeleton (1) can also function as an isolated earthquake protecting system, whether or not enveloped by a torus buffer or any other wrapping, while granulated and fluidum-like materials (4) different from sand (6) are also suited for the above-mentioned purpose.

Description

- 1 -

Sand-skeleton in hydraulic torus buffer, functioning by way of supporting element as long as the protected structure is subjected to wind load only and no earthquake exists

The substance of the invention relates to an improvement of the so called "torus buffer" as described in the USA-patent number 4,887,398, since such a eathquake protecting device is subjected to wind load, causing the supported structure to move in the horizontal plane, proportionally with acting gusts, in other words: the floating building is breaking adrift within the maximum stroke allowed by the free buffer displacement as during earthquakes. The sand-skeleton according to the invention is consolidated between the upper supporting disc and the lower bottom disc by draining, rusulting in compression of the sand-water- compound within that drum-like space. This sand-skeleton however becomes disturbed immediately by vibration and trembling as occuring during earthquakes because of its low resistence against sheare stress, which frictional power under normal condition should be in equilibrium with the expected maximum wind load in the region under consideration.

As soon as disturbtion takes place, the sand-water- compound is behaving itself as a liquid; a process called liquefying, frequently underlie of damagings when occuring beneath the foundation of buildings rised on soil becoming saturated during tremblings. Within the so called torus buffer however, this phenomenon is converted into an advantage, meaning: the transition from a sojid mass into liquid allows the supported building to float during earthquakes and will not be affected by pushing from the moving earth within the maximum allowable amplitude of the protecting system. Summarizing: The sand skeleton of the invention remains solid during gales and becomes lquefied during quakes. After the quake the upper(supporting) plate can be lifted by water suppletion, facilitating the water-sand-compound to accumulate within the drum-like space beneath it, while reforming takes place successively by draining and the sand skelelon exists again, consolidated enough to withstand windload and being disturbed when an eathquake takes place again. Since liquefying and sand skeletons can be taken for granted, the description is restricted to this special application as a regulating system within the so called hydraulic earthquake torus buffer.

Another advantage related to the invention is the guarantee of fully support of the building in case the torus buffer should be callapsed due to sabotage by pearcing or otherwise Such crimes are also feasible when using different devices and even when applying no protecting devices at all. It has to be clearly emphasized that the invention does not hinder functioning of afore mentioned torus buffer in any way, because the consolidated sand skeleton becomes liquefied as soon as the earth beneath the foundation is subjected to tremblings or vibrations.

During quakes part of the released kinetic energy will be converted into heat, causing a certain temperature rise, resulting in dilatation. This dilatation tends to lift the upper supporting plate(discl) of the torus buffer, clearing more space between this upperplate and the ground plate, although facilitating reforming of the sand-water-compound without artificial re-activating or at least reducing such. Since the compressibillity of the sand-water-compound is inconsiderable, the temporary situation of the upper disc being tilted up can be expressed in just some milimeters. This means also that such elevations can not harm the supported construction at all, provided the total lift will be such as to compensate vertical ground displacements, eventually by supplementary self-regulating system, either electronically or pneumatically.

The invention shall be detailled described with reference to the drawing, representing a vertical cross section of the torus buffer according to the aforesaid USA-patent but in this situation provided with a sand-skeleton.

The sand-skeleton 1 remains consolidated as long as the upper-disc 2 is bearing the partial load of the supported structure and no considerable forces are acting in the horizontal plane 3.

In order to stimulate the forming of sand-skeleton 1, the torus itself is also filled with a sand-water-compound 4.

The dish-shaped space of this section, together with its relative large radius 5 will force the sand mass 6 into the drum-like space below the upper-disc 2 during an earthquake.

Depending on the grain size, suspended components and specific gravaty, after a certain periode of time the sedimentation(sedimentation rate!) i.e accumulated sand 6 will be such as to allow the down comming upper-disc 2 to restore the skeleton 1.

Relative smooth applicated forces by windload 7, increasing from 0 to maximum over a much longer periode of time in comparison with by jerks applicated forces by earthquakes, allow the skeleton 1 continiously to comply with acting shear stress in its considered plane. Apart from this, the horizontal derived force 8 of the alterating applicated force 9 on the sand-skeleton 1, tends to press together also the skeleton 1 in a direction parallel to component 8, because the smooth applicated windload such allows.

Completely different situation occurs during earthquakes because of quick increasing stress inside the skeleton 1, causing its callapsing since the supported structure is not enabled to follow these movements due to its own mass- inertia 10. In other words: The mass 10 cannot be pushed by the moving soil 11 beneath the buffer 12.

The liquid-friction between upper-disc 2 and groundplate 13 can be neglected.

As soon as the sand-skeleton becomes disturbed, the drum¬ like space between upper-disc and flexible ground plate, 105 communicates unhampered with the torus in its circumference, not affected in any way by obliqueness of ground plate 13 with respect to upper-disc 2.

In order to avoid damaging of ground plate 13 - which is made from reinforced rubber but not backed by a steel plate

110 like the upper-disc - the distance between those plates shall be such as to garantee free movement, even during severe earthquakes.

Application of the sand-skeleton according to this invention for earthquake isolating of bridges does have the advantage

115 that no extra stress will act along bendings caused by centrifugal forces of heavy traffic.

The angle of friction between the upper-disc and the part of the foundation being in contact with it shall be sufficient to avoid displacement during tremblings; eventually by

120 means of extra material in the circumference of that contact area, for example poured concrete 14.

Claims

C L A I M S

1. Sand-skeleton within hydraulic torus buffer, having the behaviour to bear the supported structure in the absence of vibrations and tremblings, but being disturbed when an earthquake takes place, from that moment acting as a liquid

5 does until the earth beneath the bottom side of the buffer becomes stabilized again, allowing reforming of the skeleton after a certain periode of time, wether or not by the help of artificial intelligence or auxiliary devices such as pumps, effectuating a certain lift of the upper-disc by extra

10 temporally water supply, facilitating and shortening the restoring proces, avoiding the protected building from breaking adrift when subjected to wind load as long as the earth beneath the buffers remains unmoved.

2. Sand-skeleton according to claim 1, 15 c h a r a c t e r i z e d i n that another granulated material different from sand is used to form the required skeleton, bearing the supported construction in the absence of earthquakes and consolidated such as to withstand shear from wind load.

20 3. Sand or any granular skeleton according to aforesaid claims 1 and 2 respectively, c h a r a c t e r i z e d i n that another fluϊdum different from liquid like water is used to achieve the aforesaid properties.

25 4. Skeleton according to claim 3, c h a r a c t e r i z e d i n that the trapped air will be evacuated, allowing the atmos¬ pheric pressure to compress the fluidum in the same way as vacuum packed coffee, being vented as soon as an earthquake " 30 takes place, for example by means of a vibration sensitive valve. Such a from the original invention derived system can be preferred in case of large surface subjected to wind load related to the horizontal cross section of the structure being protected against damaging from earthquakes.

35 5. Above claims provided with frost protection.