CA2909698A1

CA2909698A1 - Structural sliding bearing and dimensioning method

Info

Publication number: CA2909698A1
Application number: CA2909698A
Authority: CA
Inventors: Christian Braun; Johann Distl
Original assignee: Maurer Soehne Engineering GmbH and Co KG
Current assignee: Maurer Soehne Engineering GmbH and Co KG
Priority date: 2013-04-24
Filing date: 2014-03-28
Publication date: 2014-10-30
Anticipated expiration: 2034-03-28
Also published as: EP2989254A1; RU2651686C2; KR20160003742A; WO2014173622A1; KR102254214B1; JP6535656B2; RU2015147606A; CA2909698C; JP2016524664A; EP2989254B1; CL2015003123A1; MX2015014736A; ES2629520T3

Abstract

The invention generally relates to structural sliding bearings which comprise at least a first bearing part, to which at least one sliding element is fastened, and a second bearing part which is arranged relatively displaceably thereto and which, in conjunction with the contact surface AK of the sliding element, forms a sliding surface which allows a sliding movement between the two bearing parts. What characterises the invention is that the shape of the contact surface (AK) of the sliding element (20) is configured such that a desired coefficient of friction (Y) is set in the sliding surface (30). Furthermore, a method is shown by means of which the coefficient of friction (Y) in the sliding surface (30) is set while taking into account a shape factor (S). Furthermore, a dimensioning method is presented in which the coefficient of friction is set in a targeted manner while taking into account a shape factor.

Description

STRUCTURAL SLIDING BEARING AND DIMENSIONING METHOD
The invention relates to a structural sliding bearing having at least one first bearing part to which at least one sliding element is attached and a second bearing part displaceable arranged relative thereto and which in combination with a contact surface of the sliding element forms a sliding surface that allows sliding movements between the two bearing parts. The invention further relates to a method for dimensioning a structural sliding bearing.
Structural sliding bearings are a special design of a structural bearing.
Structural bearings, also called bearings in the building industry, generally are for the defined support of any structures such as bridges, girders, buildings, towers, or parts thereof, if possible without constraints. That is, they allow relative movements between two components of the concerned structure. In accordance with the European rule EN 1337 various designs and operations are known. Depending on the design and operation the structural bearings have a different construction and a different number of degrees of freedom.
Structural sliding bearings, in the following briefly also referred to as sliding bearings, have at least one first bearing part to which at least one sliding element is attached and a second bearing part that is arranged displaceable relative thereto. The second bearing part in combination with the contact surface of the sliding element of the first bearing part forms a sliding surface allowing sliding movements between the two bearing parts.
Typically, the sliding element is made of a sliding material. As the sliding material various plastics having low friction such as for example PTFE,

- 2 -UHMWPE, or polyamide are used. Also, composite materials such as CM1 and CM2 given in EN 1337-2 are employed.
In order that the desired properties regarding sliding behavior, durability etc. are achieved in the whole sliding surface the surface of the second bearing part typically has a special surface coating, such as for example a hard-chrome plating, if it directly interacts with the sliding element.
However, the second bearing part may also indirectly interact with the sliding element in that it additionally has a mating sliding element. This may be a so-called sliding plate, e.g. made of an austenitic steel sheet, that has been applied to the second bearing part and that in its turn has a defined surface quality.
EN 1337 contains regulations how to realize the sliding element, the optional mating sliding element as well as the associated mounting elements and bearing parts. There is aimed a sliding resistance as low as possible upon a relative displacement or twisting of the structure or parts of the structure separated by the sliding bearing. However, for dimensioning the sliding bearing as well as the structure generally an upper dimensioning value of the coefficient of friction is used to be on the safe side. Here, the sliding resistance is defined via the coefficient of friction. The coefficient of friction is the quotient from the force required for the movement toward the sliding movement and the force acting in a right angle to the sliding surface.
In addition to the movable support of structures sliding bearings for some time are also used to separate structures or parts thereof from further surrounding structures and/or from the ground. The aim of such a separation may be for example to prevent structural damages due to earthquakes. A particular design of such a sliding bearing for separation is

- 3 -the so-called sliding isolation pendulum bearing. In this, at least one sliding surface is curved. The curvature of the sliding surface results in that at horizontal deviation re-centering forces are generated. Regulations for such bearings are given for example in the European rule EN 15129.
If in such an application not only the movement of the structure should be made possible, but also energy generated by the earthquake should be dissipated, then a certain numerically defined friction behavior in the sliding surface is required. In sliding bearings dissipation of energy may take place in the sliding surface by the friction between the bearing parts that occurs upon movement. In addition to the desired effect of energy dissipation at the same time the friction causes that reaction forces are applied to the structure. With increasing friction, both reaction forces and dissipated energy increase. Since on the one hand high reaction forces are to be avoided, but on the other hand it is desired to eliminate a large amount of energy, a structure-related optimum has to be sought between the reverse effects.
A decisive parameter for the friction between two moving objects is, as mentioned, the friction coefficient. According to the current state of the art, the friction coefficient is substantially controlled by the choice of the sliding and mating material, the type of lubrication of the sliding surface as well as the contact pressure.
It is a problem with the prior art sliding bearings that depending on the desired purpose and minimum or maximum friction desired or required therefor the sliding bearing has to be individually designed for the respective purpose. Against the background of the partially reverse design objectives it is not easy to dimension and adapt the bearings. So, for example there have already been attempts with sliding isolation pendulum

- 4 -bearings in which a first lubricated sliding material was used in a first sliding surface and an unlubricated second sliding material in a second sliding surface. The first sliding material is to ensure the movement of the bearing parts during normal usage if possible without constraints, that is, to generate a low friction. The second sliding material is for providing a high energy dissipation in case of an earthquake, that is, should have a great friction.
However, coordination of the sliding properties and the use of different sliding materials is not trivial. On the one hand, EN 1337-2 only provides guidelines for the use of PTFE that has to be lubricated in certain manner.
If one wants to use another sliding material or modify the lubrication special tests for suitability have to be performed that are very complex and expensive. Also, the use of different sliding materials, lubrications, surface qualities etc. in the manufacture is extremely complex.
Thus, it is the object of the present invention to provide a structural sliding bearing that is easily adaptable in view of its frictional properties and can be manufactured as simple and economical as possible.
The solution of said problem according to the invention is achieved with the structural sliding bearing invention according to claim 1 as well as the dimensioning method according to claim 17. Suitable further developments of the sliding bearing and the dimensioning method, respectively, are described in the sub-claims.
That is, the structural sliding bearing according to the invention is characterized in that the shape of the contact surface of the sliding element is configured such that a desired friction coefficient is established in the sliding surface. The invention is based on the finding that the

- 5 -friction coefficient with the same sliding material changes with the shape of the contact surface of the sliding element and this behavior can be used to specifically adjust the friction coefficient and thus, also the friction of the structural sliding bearing. That is, the frictional behavior of the sliding bearing not as previously common is adjusted by the choice of the sliding and mating material, the way of lubricating the sliding surface as well as the contact pressure. Rather, by specifically shaping the contact surface of the sliding element the friction coefficient is influenced in the desired manner and thus, by a further decisive parameter. Tests of the applicant have shown that in structural sliding bearings different deformation behaviors of the sliding material in the center of the contact surface and at the edge of the contact surface adjust the sliding resistance and this effect can be specifically used to adjust a desired frictional behavior in the sliding surface.
In a suitable further development of the structural sliding bearing the desired friction coefficient in the sliding surface is adjusted depending on the circumferential length and/or the ground plan type of the contact surface and/or the sliding slit height and/or the orientation of the edges of the contact surface with respect to the sliding direction. So, it is conceivable that edges extending in parallel to the sliding direction have a minor influence on the friction coefficient than edges that orthogonally extend to the friction direction. Accordingly, a defined orientation of the free circumferential surface toward the various degrees of freedom of the structural sliding bearing causes that different friction coefficients and thus, friction resistances are present toward the various degrees of freedom. Moreover, it is conceivable to represent the influence of the individual shaping of the sliding surface ground plan on the friction coefficient via a shape coefficient. Here, it may be relevant whether the sliding surface ground plan rather has chubby outline edges or sharp

- 6 -corners as well as the respective number of edges as well as their distance and orientation to the sliding surface center of gravity. Also, the sliding slit height may be used to influence the friction coefficient in the sliding surface. So, for example it is conceivable that for large sliding slits due to the flow of the sliding material at the edge of the sliding surface the friction coefficient decreases, but also with very low sliding slits the effect of an influence of the friction coefficient is only partially established.
Accordingly, depending on the desired effect on the friction coefficient an optimum sliding slit height may exist.
Since sliding elements of structural sliding bearings cannot be of any desired shape it is possible to adjust the friction coefficient by designing the shape of the sliding element especially by adjusting the ratio of contact surface to free circumferential surface. Here, free circumferential surface means the surface that can freely deform in the sliding slit between the first bearing part and the second bearing part at the circumferential side of the sliding element, that is exposed. In the case of an embedded support of a sliding disc that fits completely flat to the opposite side this is the circumference multiplied with the height of the sliding disc minus the depth of the embedding. Contact surface means the proportion of the surface of the sliding element that totally contacts the second bearing part. If the free circumferential surface is decreased at constant contact surface by increasing the circumference of the contact surface at constant height of the sliding slit, then the friction increases.
By specifically influence of the frictional behavior of the sliding bearing by shaping the sliding element the sliding bearing can very easy be adapted to different problems and application purposes. And this without complex tests for suitability or having to request special approvals. Rather, this way different problems can be solved with one and the same sliding

- 7 -material for which for example an approval as sliding material has already been achieved. So, on the one hand it is possible to construct normal sliding bearings with the material or an earthquake isolator that in comparison should have an increased friction in the concerned sliding surface by increasing the proportion of the circumferential surface of the sliding element. Moreover, the invention has the effect that in manufacture there must no longer be stored different materials. This reduces the storage costs, prevents confusion of bearings in manufacture, and brings advantages in purchasing. That is, the bearing according to the invention can be prepared considerably easier and more cost-effectively.
An advantageous further development of the invention provides that the friction coefficient in the sliding surface is adjusted as function of a form factor considering the ratio of contact surface to free circumferential surface of the sliding element. Here, the form factor is a quotient of the contact surface to the free circumferential surface, wherein, as already mentioned, the free circumferential surface is the length of the circumference of the contact surface multiplied with the height of the sliding slit. Suitably, the size of the contact surface of the sliding element has been optimized depending on the form factor, preferably minimized, such that the desired friction coefficient in the sliding surface is achieved without a change of the pressure. In this way, the structural sliding bearings for the respective application purpose may be made smaller and thus, more economical.
In particular, if the sliding bearing is intended for use in earthquake isolation it is suitable to shape the sliding element such that the amount of the friction coefficient in the sliding surface has been maximized depending on the form factor. Thus, for practical application that means that by increasing the free circumferential surface at the same contact

- 8 -surface for the structural sliding bearing a greatest possible friction coefficient and thus, also a greatest possible dissipation capacity can be achieved. For example, the increase of the free circumferential surface can be done by changing the shape of the contact surface. For example, the contact surface may have an oval or star-shaped shape or any other conceivable shape that results in a larger free circumferential surface.
Preferably, in such applications the structural sliding bearing is designed as a spherical bearing, in particular as a sliding isolation pendulum bearing. Typical of spherical bearings is that they have at least one curved sliding surface, whereas sliding isolation pendulum bearings have several curved sliding surfaces. So, it is conceivable that the friction coefficient in different sliding surfaces is specifically adjusted differently, but consisting of the same sliding material as described above. So, one sliding surface may be designed for normal use as a conventional sliding bearing with low friction, whereas a second sliding surface especially in view of an earthquake is designed with an increased friction coefficient, that is, an increased dissipation capacity.
In a further development the contact surface of the sliding element is formed of two, in particular more than four partial contact surfaces.
Subdivision of the contact surface into partial contact surfaces causes an increase of the free circumferential surface of the sliding element. Such a subdivision can be effected by several sliding elements or by notching or the like. Here, subdivision facilitates fabrication since it can be easily generated and needs to be changed little on the basic geometry of the sliding element or its initial materials (often plates of a certain thickness made of a sliding material).

- 9 -An advantageous further development of the structural sliding bearing provides that the sliding element has at least one sliding disc with the contact surface being formed of at least a part of the surface of the at least one sliding disc. The sliding element also has a conventional sliding disc known per se or may even completely consist thereof.
In this case it is suitable if at least a part of the surface of the at least one sliding disc by at least one recess is subdivided into partial contact surfaces. So, friction can be increased in comparison to a conventional sliding disc of the same material. For example, such a recess may be one or more grooves that are applied to a part of the surface of the at least one sliding disc. Applying said one or more grooves can be effected for example by milling into a part of the surface of the at least one sliding disc.
Applying recesses to the sliding material is a particularly economical method to generate partial contact surfaces. Generally, the width of the recess is between a few millimeters and twice the thickness of the first bearing part to ensure on the one hand a sufficient support of the sliding material and on the other hand uniformly distribute the pressure in the adjacent components. Subdividing at least a part of the surface of the at least one sliding disc in turn causes that the free circumferential surface of the sliding element increases relative to the contact surface and thus, the form factor is affected.
Basically, the at least one recess may be of any desired shape to produce arbitrary partial contact surfaces. However, preferably the recess is designed such that it is oblong or has the shape of a circle, ring, or a segment of any of them. For that, fabrication methods such as turning or milling due to their high flexibility are suitable. However, alternatively the

- 10 -recess may also already be prepared in the manufacture of the sliding element, for example when casting or sinter-pressing into plate shape.
In particular, if the sliding bearing or the sliding material of the sliding disc, respectively, is exposed to high pressures it is suitable that at least one spacer is inserted into at least one recess. Inserting a spacer into the recess ensures that the sliding material of the sliding disc at the edge of the partial contact surfaces cannot laterally swerve under the load. In analogy to the embedded support of the sliding element in the first bearing part the sliding disc is embedded to the inside. By the inner embedding at the same load the sliding discs and the structural sliding bearing may be made smaller or with the same size of the sliding disc higher loads can be taken up with the structural sliding bearing.
In an advantageous further development of the structural sliding bearing the sliding element has a number of sliding discs. In this way, on the one hand the sliding element can be composed of equally and/or differently shaped sliding discs and on the other side also the sliding element can be variably constructed from different sliding materials by using sliding discs.
Further, it also becomes possible to compose large and/or individually shaped sliding elements from a number of standardized sliding discs, whereby the production of the structural sliding bearing according to the invention becomes particularly economical.
Preferably, the contact surface and/or at least a partial contact surface have the shape of a circle, ring, or a segment of any of them. Said shaping has the advantage that only a few or no corners are formed that would result in a selective increase of the friction. That is, said shaping helps to keep wear low.

-11 -An advantageous further development of the structural sliding bearing provides that the sliding element and/or at least one sliding disc of the sliding element is held embedded in the first bearing part. By the embedded holding of the sliding element or the at least one sliding disc flowing of the sliding material due to the pressure generated from structural loads is reduced. Moreover, the type of embedding has influence on the size of the free circumferential surface, since this depends on the height of the sliding slit, in other words the height of the projection of the sliding element above the first bearing part.
If needed it may be suitable that at least one spacer is arranged between two sliding discs. Generally, said spacer has a width between a few millimeters and twice the thickness of the first bearing part. In this way, it is ensured that on the one hand a sufficient support or inner embedding of the sliding material against flowing is guaranteed. On the other hand, it is ensured that the pressure is uniformly distributed in the adjacent components.
Preferably, the sliding element and/or at least one sliding disc at least partially consists of a sliding material, in particular a thermoplastic sliding material. Thermoplastic materials can be readily poured into molds that may already have webs to produce recesses for subdivision into partial contact surfaces, for example.
Particularly preferably, the sliding element and/or at least one sliding disc at least partially consists of PTFE, UHMWPE, polyamide, and/or a combination of at least two of such materials. Here, both the sliding element and the at least one sliding disc may consist of the mentioned materials in the pure form or alternatively of a material mixture of two or more of such materials. It is also conceivable that several sliding discs of

- 12 -different of such materials in the pure form and/or different mixtures of such materials are composed to a sliding element.
The method for dimensioning a structural sliding bearing according to the invention provides that the friction coefficient in the sliding surface is adjusted by considering a form factor. Unlike in the prior art, where the friction coefficient and thus, also the friction of the structural sliding bearing are influenced by the choice of the sliding and mating material, the type of lubrication of the sliding surface as well as the contact pressure, the approach according to the invention is based on the fact that the friction is specifically adjusted by affecting the shape of the contact surface, that is not by affecting material or unit stresses but by affecting geometrical parameters. Accordingly, by shaping the contact surface of the sliding element the friction coefficient can be affected in a surprisingly simple and highly flexible manner.
Preferably, dimensioning of the structural sliding bearing is performed in that the desired friction coefficient in the sliding surface is adjusted depending on the circumferential length and/or the ground plan type of the contact surface and/or the sliding slit height and/or the orientation of the edges of the contact surface with respect to the sliding direction. For calculating the friction coefficient it is conceivable that in the calculation methodology of the friction coefficient the influence from the circumferential length, ground plan type of the contact surface, sliding slit height and orientation of the edges to the direction of displacement via individual coefficients is considered.
An advantageous further development of the method according to the invention provides that the friction coefficient in the sliding surface is adjusted as function of a form factor considering the ratio of contact

- 13 -surface to free circumferential surface of the sliding element. As already mentioned above, the form factor is a quotient of the contact surface to the free circumferential surface.
In a further development, the size of the contact surface of the sliding element is optimized, preferably minimized, depending on the form factor such that the desired friction coefficient in the sliding surface is achieved.

In this way, the structural sliding bearings for the respective application purpose may be made smaller and simultaneously more economical.
Alternatively or additionally, the amount of the friction coefficient in the sliding surface may be maximized depending on the form factor. This especially makes sense if the bearing has to be designed for earthquake isolation.
Preferably, dimensioning is performed such that the material combination in the sliding surface is kept constant during optimization. This allows a simplified dimensioning of the sliding bearing.
In the following the invention is explained in detail with the help of the drawings. Here:
Fig. 1 schematically shows a section through a first example of a structural sliding bearing according to the invention with a flat sliding surface;
Fig. 2 schematically shows a detail from a section through a second example of a sliding bearing according to the invention with a curved sliding surface;
Fig. 3 schematically shows a detail from a section through a third example of a sliding bearing according to the invention;

- 14 -Fig. 4 schematically shows a detail from a section through a fourth example of a sliding bearing according to the invention;
Fig. 5 schematically shows a section through a fifth example designed as a sliding isolation pendulum bearing of a sliding bearing according to the invention;
Fig. 6 schematically shows a section A-A of the sliding isolation pendulum bearing shown in Fig. 5;
Fig. 7 schematically shows the top plan view of the contact surface of a sliding disc in a sixth embodiment;
Fig. 8 schematically shows the top plan view of the contact surface of a sliding disc in a seventh embodiment;
Fig. 9 schematically shows a measuring chart illustrating the friction coefficient Y as a function of pressure X; and Fig. 10 schematically shows a measuring chart illustrating the friction coefficient Y as a function of the product of form factor and pressure.
In the figures same reference numbers are used for identical parts.
Fig. 1 shows a first example of a structural sliding bearing 10 according to the invention. As to construction it basically corresponds to the structural sliding bearings described in EN 1337. It has a first bearing part 15, a sliding element 20 attached thereto and a second bearing part 25. The second bearing part 25 in turn has a mating surface 55 that in the present case is designed as a hard chromium coating, but may also consist of a sliding plate of austenitic steel or the like. The first bearing part 15 and the second bearing part 25 are designed displaceable relative to each other, so that a sliding surface 30 is formed from the combination of the present flat surfaces of the sliding element 20 and the mating surface 55.
In the present case, the sliding element 20 consists of a flat sliding disc

- 15 -made of a sliding material and is held in the first bearing part 15 by means of embedding. However, additionally according to the invention the geometry of the sliding plate 20 in the ground plan here not illustrated is star-shaped, so that a relative large circumferential surface with respect to the contact surface is established, whereby an increased friction coefficient is established in the sliding surface 30 in comparison to a circular sliding plate.
In Fig. 2 there is shown a schematic section through a second example of a structural sliding bearing 10 according to the invention with a curved sliding surface 30. Also, this example has a first bearing part 15, a plate-like sliding element 20 and a second bearing part 25 displaceable relative thereto. The sliding element 20 contacts the second bearing part 25 via the contact surface AK of the sliding element 20. Since here, the sliding element 20 is also held embedded in the first bearing part 15 the free circumferential surface Am results from the product of the circumferential length with the height of the sliding slit h, that is, the thickness of the plate-like sliding element 20 tp minus the depth of the embedding.
Fig. 3 is a detail from a section through a third structural sliding bearing 10 according to the invention. It can be seen the first bearing part 15 and the second bearing part 25 with a mating surface 55. The sliding element 20 in the illustrated first embodiment is composed of several sliding discs 35. The sliding discs 35 are held embedded in the first bearing part 15.
For this to work spacers 45 are located between the sliding discs 35 of the sliding element 20 that keep the sliding discs at a constant distance to each other and at the same time provide for an inner embedding between the sliding discs 35. In this way, the contact surface AK is interrupted in the sliding surface 30 and the proportion of the free circumferential surface Am is increased over the contact surface AK of the sliding element.

- 16 -So, by geometrically design of the surface of the sliding element 20 the form factor S may be affected. As a result, with a sliding element having a number of sliding discs 35 and spacers 45 the friction coefficient Y is increased in comparison to a continuous sliding disc. As an alternative to the inserted spacers 45 there can also be present a web on the first bearing part 15 in a material-closed manner.
Fig. 4 is a top plan view of a section through a fourth example of a structural sliding bearing 10 with a sliding element consisting of a single curved sliding disc 35 the surface of which is subdivided into several partial contact surfaces by recesses 40. Recesses 40 are applied to the surface of the sliding disc 35 such that they interrupt the surface of the sliding disc 35. In this way, the contact surface AK in the sliding surface 30 is subdivided and the size of the free circumferential surface Am of the sliding disc 35 or sliding element 20, respectively, is increased. In this way, by geometrically design of the surface of the sliding disc 35 or sliding element 20, respectively, the form factor S may be affected. As a result, the friction coefficient Y is increased.
In fig. 5 a sliding isolation pendulum bearing is illustrated which has two sliding surfaces 30 and two sliding elements 20 each having a contact surface AK. Both contact surfaces of the sliding element 20 may be designed such that a desired friction coefficient is established in the respective sliding surfaces 30. One of the sliding elements 20 consists of several sliding discs 35. An intersection line A-A is passed through said sliding element 20 that indicates the section through the sliding element 20 and the sliding discs 35.
Fig. 6 shows the section along the line A-A through the sliding element 20 indicated in fig. 5. In said section several sliding discs 35 can be seen of

- 17 -which the two outer sliding discs 35 have an angular shape and the inner sliding disc 35 has a circular shape. In fig. 6 there can also be seen the first bearing part 15 that includes and embeds the outer sliding disc 35.
Moreover, the individual sliding discs 35 are kept evenly spaced by spacers 45. Accordingly, the spacers 45 cause an inner embedding of the sliding element 20 composed of sliding discs 35, so that it can completely be held in the bearing part 15 in an conventional manner, that is embedded. The part of the sliding discs 35 protruding over the spacers 45 acts as the free circumferential surface AM and thus affects the form factor S. In addition to the illustrated representation of a sliding element it is also conceivable that the sliding element 20 is not only composed of angular or circular sliding discs 35. Rather, it is conceivable that the sliding discs 35 may take any shape and form an arbitrarily shaped sliding element 20.
In fig. 7 there is illustrated a further example of a sliding element 20 consisting of a single sliding disc 35. In addition to a variation of the circumferential shape also the surface of the sliding disc which as contact surface AK in the sliding surface 30 contacts the second bearing part 25 may be varied. In figure 7 a sliding disc 35 is illustrated that has recesses 40 so that the contact surface AK is composed of a number of partial contact surfaces 50. In the illustrated example the partial contact surfaces 50 are circular. Here, the sum of the partial contact surfaces 50 forms the contact surface AK of the sliding disc. Further, application of a recess 40 to the sliding disc 35 causes that the partial contact surfaces 50 protrude above the recess. In this way, the free circumferential surface Am of the sliding disc 35 is increased and the form factor S is affected such that the friction of such a sliding plate is increased in comparison to one with a continuous contact surface.

- 18 -Fig. 8 shows a further example of a sliding disc 35 according to the invention in which the recesses 40 are applied to the sliding disc 35 in the form of straight grooves or rings. In this way, the contact surface AK of the sliding disc 35 can be subdivided into angular faces and/or circles as well as ring segments and/or circle segments can be formed.
In fig. 9, the measuring results of a test series are represented during which structural sliding bearings 10 with an unlubricated circular sliding element 20 made of the sliding material UHMWPE have been studied.
During the test series at a constant sliding slit height on the one hand the diameter of the circular sliding element was varied and also the pressure of the sliding element. It was proven on the one hand that a sliding element of a diameter of 80 mm at the same pressure has a markedly higher friction coefficient than a comparable circular sliding element of 120 mm in diameter. The circular sliding element of 120 mm in diameter in turn has a markedly higher friction coefficient than a comparable circular sliding element of 300 mm in diameter. It can also be seen that the friction coefficient for a circular sliding element with a constant diameter at increasing pressure decreases. Obviously, the different deformation behavior of the sliding material in the center and at the edge of the contact surface AK affects the sliding resistance. With an increasing diameter of the circular sliding element the contact surface AK increases disproportionately to the free circumferential surface Am. The friction coefficient decreases accordingly.
In practice, this phenomenon for example can be used to increase the friction coefficient Y for a sliding element 20 with the same contact surface AK by subdividing the contact surface AK into several partial contact surfaces 50 that in sum of the same have the same contact surface AK. However, because in this way the size of the free

- 19 -circumferential surface is increased the friction coefficient of the structural sliding bearing is increased accordingly.
Fig. 10 shows the connection between friction coefficient and form factor S at constant pressure X determined in tests, wherein the abscissa shows the product of form factor S to the power of 0.6 multiplied with pressure X.
It has shown in the tests that with increasing form factor, that is a growing proportion of the contact surface AK in relation to the free circumferential surface Am, the friction coefficient Y decreases. The test results show that the friction coefficient Y for the tested UHMWPE can be given with sufficient accuracy as function of pressure and form factor S and pressure X for example as follows.
Y = 34 . S- .78 *X-13 + 0.02 In the shown formula the form factor S is non-dimensional. However, pressure X due to the exponent has dimensions. Thus, the illustrated connection requires input of pressure in [Nlimm2]. Form factor S is calculated as follows (U is the circumferential length of the contact surface AK):
S = AK ./. Am = AK .1. (U h) The effect of the form factor is shown when replacing a circular sliding element of a diameter D1 by four discs of a diameter D2, wherein D2 = 1/2 Dl.
It turns out that with an identical contact surface AK the form factor is halved by the subdivision into four individual discs. In the present practical example, by such a subdivision the friction in the sliding surface can be

- 20 -increased by up to 60% without a change of the material properties, or there can be achieved the same friction coefficient at an almost double pressure as a result of a reduction of the contact surface AK. This enables a higher energy dissipation with structural sliding bearings. Alternatively, said effect may be used to significantly reduce the sliding contact surface AK at the same friction coefficient and thus make the structural sliding bearing more economical.

- 21 -List of Reference Numbers = structural sliding bearing = first bearing part 5 20 = sliding element = second bearing part = sliding surface = sliding disc = recess 10 45 = spacer = partial contact surface = mating surface Y = friction coefficient 15 AK = contact surface Am = free circumferential surface S = form factor h = height of the sliding slit X = pressure 20 Tp = thickness of the sliding element 25 or sliding disc 35

Claims

1. A structural sliding bearing (10) having at least one first bearing part (15) to which at least one sliding element (20) is attached and a second bearing part (25) that is arranged displaceable relative thereto and which in combination with a contact surface (A K) of the sliding element (20) forms a sliding surface (30) allowing sliding movements between the two bearing parts (15, 25), characterized in that the contact surface (A K) is subdivided into several partial contact surfaces and that the shape of the contact surface (A K) of the sliding element (20) is designed such that a desired friction coefficient (Y) is established in the sliding surface (30), wherein the friction coefficient (Y) in the sliding surface (30) is adjusted as function of a form factor (S) considering the ratio of contact surface (A K) to the free circumferential surface (A M) of the sliding element (20).

2. The structural sliding bearing according to claim 1, characterized in that the desired friction coefficient (Y) in the sliding surface (30) is adjusted depending on the circumferential length and/or the ground plan type of the contact surface (A K) and/or the sliding slit height (h) and/or the orientation of the edges of the contact surface (A K) with respect to the sliding direction.

3. The structural sliding bearing according to claim 1 or 2, characterized in that the size of the contact surface (A K) of the sliding element (20) has been optimized, preferably minimized, depending on the form factor (S) such that the desired friction coefficient (Y) in the sliding surface (30) is achieved.

4. The structural sliding bearing according to any of the preceding claims, characterized in that the amount of the friction coefficient (Y) in the sliding surface (30) has been maximized depending on the form factor (S).

5. The structural sliding bearing according to any of the preceding claims, characterized in that it is designed as a sliding isolation pendulum bearing.

6. The structural sliding bearing according to any of the preceding claims, characterized in that the contact surface (A K) is formed of two, in particular more than four partial contact surfaces.

7. The structural sliding bearing according to any of the preceding claims, characterized in that the sliding element (20) has at least one sliding disc (35), wherein the contact surface (A K) is formed of at least a part of the surface of the at least one sliding disc (35).

8. The structural sliding bearing according to any of the preceding claims, characterized in that at least a part of the surface of the at least one sliding disc (35) is subdivided into partial contact surfaces (50) by at least one recess (40).

9. The structural sliding bearing according to claim 8, characterized in that the recess (40) has the shape of a circle, a ring, or a segment of any of them.

10. The structural sliding bearing according to claim 8 or 9, characterized in that in at least one recess (40) at least one spacer (45) is arranged.

11. The structural sliding bearing according to any of the preceding claims, characterized in that the sliding element (20) has a number of sliding discs (35).

12. The structural sliding bearing according to any of the preceding claims, characterized in that the contact surface (A K) and/or at least one partial contact surface (50) has the shape of a circle, a ring, or a segment of any of them.

13. The structural sliding bearing according to any of the preceding claims, characterized in that the sliding element (20) and/or at least one sliding disc (35) of the sliding element (20) is held embedded in the first bearing part (15).

14. The structural sliding bearing according to any of the preceding claims, characterized in that at least one spacer (45) is arranged between two sliding discs (35).

15. The structural sliding bearing according to any of the preceding claims, characterized in that the sliding element (20) and/or at least one sliding disc (35) at least partially consists of a sliding material, in particular a thermoplastic sliding material.

16. The structural sliding bearing according to any of the preceding claims, characterized in that the sliding element (20) and/or at least one sliding disc (35) at least partially consists of PTFE, UHMWPE, polyamide, and/or a combination of at least two of such materials.

17. A method for dimensioning a structural sliding bearing (10) according to any of the preceding claims, characterized in that the friction coefficient (Y) in the sliding surface (30) is adjusted by considering a form factor (S), wherein the friction coefficient (Y) in the sliding surface (30) is adjusted as function of a form factor (S) considering the ratio of contact surface (A K) to the free circumferential surface (A M) of the sliding element (20).

18. The method for dimensioning a structural sliding bearing according to claim 17, characterized in that the desired friction coefficient (Y) in the sliding surface (30) is adjusted depending on the circumferential length and/or the ground plan type of the contact surface (A K) and/or the sliding slit height (h) and/or the orientation of the edges of the contact surface (A K) with respect to the sliding direction.

19. The method for dimensioning a structural sliding bearing (10) according to claim 17 or 18, characterized in that the size of the contact surface (A K) of the sliding element (20) has been optimized, preferably minimized, depending on the form factor (S) such that the desired friction coefficient (Y) in the sliding surface (30) is achieved.

20. The method for dimensioning a structural sliding bearing (10) according to any of claims 17 to 19, characterized in that the amount of the friction coefficient (Y) in the sliding surface (30) is maximized depending on the form factor (S).

21. The method for dimensioning a structural sliding bearing (10) according to any of claims 17 to 20, characterized in that the material combination in the sliding surface (30) is kept constant during optimization.