CA1186359A - Bearings for structures - Google Patents
Bearings for structuresInfo
- Publication number
- CA1186359A CA1186359A CA000403688A CA403688A CA1186359A CA 1186359 A CA1186359 A CA 1186359A CA 000403688 A CA000403688 A CA 000403688A CA 403688 A CA403688 A CA 403688A CA 1186359 A CA1186359 A CA 1186359A
- Authority
- CA
- Canada
- Prior art keywords
- layer
- plate member
- bearing
- members
- plate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D19/00—Structural or constructional details of bridges
- E01D19/04—Bearings; Hinges
- E01D19/041—Elastomeric bearings
-
- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D19/00—Structural or constructional details of bridges
- E01D19/04—Bearings; Hinges
- E01D19/042—Mechanical bearings
- E01D19/047—Pot bearings
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Architecture (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Bridges Or Land Bridges (AREA)
Abstract
Abstract of the Disclosure A supporting bearing for the support of a structure such as a bridge or elevated roadway from a supporting pier or embankment has two systems for accommodating misalignment of the bearing with the expected direction of longitudinal move-ment of the structure and/or non-linear movement such as may be obtained with a curved bridge. These systems may be used alternatively or in addition to one another. In the first system longitudinal guide means which are provided between two relatively longitudinally-movable plate members of the bearing are resiliently mounted to one of the plate members and accommodate the misalignment or non-linear movement by deformation of the resilient mounting, which preferably comprises strips of resilient material interposed between strips of low-friction material and respective edges of the plate members. In the second system the bearing comprises two plate members having between them a layer of resilient material which accommodates vertical, horizontal, rotating and tilting forces between the two members; such as a bearing has a layer of low friction material interposed between the layer of resilient material and the plate member which transmits the load to the resilient layer, so as to facilitate movement between them accommodating the said misalignment and non-linear movements.
Description
I~IP~OV~MF.NTS IN BEARINGS FOR STRUCTURES
~ield of the Invention _ _ . _ The present invention is concerned with improvements in or rela-ting to bearings for structures, such as bridges and elevated roadways.
~eview of the Prior ~rt My prior U.S. Patent specificationsSerial Nos: 3,806,975 and 3,921,240 disclose and claim a high load structural bearing which includes a layer of an elastomer between two parallel plates to acccmmodate vertical, horizontal, tilting and rotation forces applied to the bearing by the struc-ture which it supportsO
Excessive horizontal shear forces applied to the elastomer layer are resisted by a shear restricting element~ while expected horizon-tal longitudinal movements of the supported structure are accommodated by sliding movement that takes place between two bearing members arranged for that purpose. These bearings have now obtained complete engineering and commercial acceptance, and are used extensively in many different kinds of s-tructures, principally bridges and ele~ated roadways.
While such a bearing is being installed it is essential that the direction of sliding which it is designed to permit be aligned accurately with the expected direction of movement of the supported structure, since otherwise there is a danger that excessive sideways forces, sufficient to cause binding of the sliding members, will be applied to the bearing. Even when the installation is performed by skilled and conscien-tious operators there is a danger of misalignment occuring, for example while the surrounding cement is being poured if the bearing is not held rigidly in position cluring the operation.
In recent years the designers o~ bridge structures and the like llave become more venturesome in curving the structures for both practical and aesthetic reasons, and are attempting designs with an amoun-t and/or degree of curvature that would not previously have been contemplated. ~his has placed a requirement on the bearings to accommodate the resulting non-linear movements of the structure, e.g. with temperature changes. Moreover, it is difficult to predict in practice with any degree of accuracy the average direction of such movements, adding to the above-mentioned difficulty of ensuring -that the bearing has been installed wi-th the optimum alignment for free sliding.
Definition of the Invention It is therefore an object of the invention to provide a new bearing for structures able to accommodate a degree of misalignment that would damage or disable a prior art bearing.
In accordance with the present inven-tion there is provided a supporting bearing for the support of a structure such as a bridge or elevated roadway, the bearing comprising:
a first plate member movable with the structure and on which -the s-tructure rests for support thereby;
a second plate member on which the first plate member rests for reLative longitudinal slidinc~ movemen-t between them upon corresponding movemen-t of the first plate member ~ith the structure; and longitudinal guide means comprising spaced longitudinal guide members resiliently mounted to one of the said first and second plate members and operative between the t~"o plate members to constrain the other plate member for the said relative longitudinal slidi:ng movement between them and against relative -transverse movement transverse to said longitudinal movement, the resilient mounting of the guide members permitting a small -transverse deviation relative movement in the said relative longitudinal sliding movement accommodating misalignment and/or non-linear movement between the firs-t and second plate members.
Further, in accordance with the present inven-tion there is provided a supporting bearing for -the support of a structure such as a bridge or elevated roadway, the bearing comprising:
a plate member on which -the structure rests for support thereby;
another plate member;
a radially-unconstrained layer of resilient material interposed between the first-mentioned and another plate member and supporting the latter from the former for vertical, horizontal, tilting and rotational movemen-ts, the layer of resilient material being surrounded at least at its junction with the first~men-tioned and another plate member wi-th respective restraining rings upstanding from the plate members for restraining the extent of transverse movement be-tween the layer of resllient material and tl~e respective plate member;
horizontal shear restricting means extending between the first-mentioned and another plate member for preventiny the application of excessive horizontal shear forces to the La~er of resilient material as the result of ho:rizontal movements between the plate members; and a layer of low-friction material interposed between one of the plate members and the layer of resilient material to facilitate transverse movement of the respective plate member relative to the layer of resilient material upon application of horizontal misalignment forces thereto.
- 3a -Ic~cr~ t-;oll (? ~ t~ ' Dl^a~ JS
. . . ~
i'.lrt-icul~lr ~rc:~erred embodiTnen~s o~ thc invention ~/ill now be described, by way o~ example, with reEerence to the accom~anying diagrammatic drawings, wherein:-E~IGURE 1 is a plan view of a first embodiment, parts thereof being broken away as necessary to show -the construction thereof;
FIGURE 2 is a section taken on the line 2-2 of Figure 1, FIGURE 3 is a section taken on the line 3-3 of Figure l;
FIGURE 4 is a section similar to Figure 2 of a second embodiment;
FIGURE 5 is a section similar to Figure 2 of a third embodiment;
FIGU~E 6 is a cross-section of a small portion of a guide means of the structure of any of Figures l - 5 to show a modification; and FIGURE 7 is a similar cross-section to Figure 6 of another modification.
Description of the Preferred Embodiments Referring now to Figures l to 3 a first embodiment particularly suitable for use as a bridge bearing consists of a lower plate lO, usually of circular shape in plan~ The plate usually is embedded in the concrete work (not shown) of the bridge structure and is provided with a single axially-disposed, downwardly-extending anchor pin 12 for embedding in that concrete.
An annular bearing element 14 of a suitable elastomeric material i~ s<~ncl~iched betweell ~he lowel- pl.~lt,C 10 alld an upper beariny plate 16 which is of rectan~ul.lr i}-~apc in plan, the element 14 being surrounded at its circumferential boundaries with the respective plates by respective circular limiting rin~s 18 and 20 that extend toward one another. A horizontal shear restrict-ing mechanism as disclosed in my prior patents Serial Nos.
3,806,975 and 3,921,240, consists of a pin 22 extending upward axially from the lower plate 10 and embraced by a sleeve 24 extending downward from the upper plate 16; this mechanism permits vertical, tilting and rotational movements between the two plates 10 and 16 under control of the element 14 and also a limited amount of horizontal movement, while preventing the application of excessive horizontal shear forces to the element~
The unavoidable longitudinal movements of the structure supported by the bearing are accommodated by permitting longitudinal sliding movement between the upper bearing plate 16 and an uppermost plate 26 the latter plate being fixed rigidly to the supported structure; in this embodiment is is provided with a plurality of parallel upwardly-extending anchor pins 28 which are embedded in the said supported structure. The two plates 16 and 26 have sandwiched between themselves a layer 30 of a low-friction material, such as polytetrafluroe-thylene and a thin sheet 32 of highly polished stainless steel, the latter being fastened as by continuous welding to the under surface of the uppermost plate 26. The plates 16 and 26 are constrained in their relative movement along a longitudinal axis 34 by downwardly-extending ~s~
guide bars 36 fixed ~o the undersurface of the uppermost plate, the opposed vertical edge faces of the plate 16 and the guide bars 36 being provided with respective strips 38 and 40 of low friction material e.g. polytetrafluorethlyene.
The bearing is provided at each end with a buffer stop consisting of a buffer support 54lfastened to the plate 26, a buffer plate 56 that is disposed to engage the facing edge of the plate 16, and a buffer pad 58 of-elastomeric material interposed between the support 54 and plate 56. As the bearing reaches its extreme position at either end the plate 16 engages t~e plate56 , which moves toward the support 54 compressing the pad 58, the plate being guided in such movement by rods 60 moving in correspond ing bores in the support.
Any misalignment between the axis 34 and the actual direction of attempted sliding movement of the plate 26 over the plate 16 would~ in the absence of the invention, cause unaccept-able binding between the plate 16 and the bars 36 to an extent that could seriously damage and eventually even destroy the bearing. This is prevented in accordance with the i~vention by mounting the low friction strip 38 on a thin metal backing strip 42, which is in turn mounted on a strip 44 of an elastomeric material that is thus interposed between the respective opposed vertical edges of the guide ~ar ~6 and the plate 16 along the whole length of the plate. If there is any small misalignment of the sliding movement for the reasons explained above, or such misalignment appears because the sliding movement is along a non-linear path, then this is accommodaked by expansion or compression in the elastomeric strips 44, so that th~ slidin~ tak~s ~ ~; ,, ~lace without binding.
In some alternative embodiments each low friction strip 38 is bonded directly to the elastomer strip 44, and in others the strips simply lie alongside one another and are fastened in place by bolts that are threaded into the plate 16-~ lter~ t-ivcly, or in acldil-ion, a~ e1aitomer s~ri may be interposed between the low friction strip ~0 and -the respective guide 36, as illustrated in broken lines in Figure 2.
The invention is illustra-ted as applied to a bearing in which straight-line sliding is provided between straight sliding surfaces, bu-t it will be apparent to those skilled in this particular art that the invention is also applicable to designs with which the sliding surfaces are curved.
In the embodiment of Figure 3 each strip or elastomer ma~erial is semi-confined within a longitudinal slot 46 in the respective vertical edge of the plate 16, while in the embodiment oE Figure 4 each strip 4~ is ~holly confined within its slot ~6, the strip and the slot being of substantially the same cross-sectional dimensions; in some embodiments the unconfined elastomer strip may be larger in cross-section than the slot so that it must be compressed for insertion therein and is therefore precompressed to a corresponding extent.
In a commercial range of bearings for load capacities from 100 to 8,000 KIPS the upper plate 16 varies in width from 18.1 cm to 162.6 cm, and in thickness from 1.27 cm. to 5.08 cm respectively, while the elastomeric layer 1~ varies in thickness from about 1.3 cm to about 10.1 cm. The elastomer strips vary in thickness from about 1.2 cm to 3 cm and are intended to accommodate deviations of up to about +15 degrees each, based on a permitted compressability o~ about * 15~. A suitable material for the unconfined structure o Figures 1 and 2 is a urethane of about 95 Durometer hardness and about 15,00Q p.s.i. strength.
Other materials such as polyethers can be usecl. The semi-confined and confined structures of ~igures 3 and 4 respectivel~ permit the use of lower hardness materials such as chloroprene, natural rubber and ethylene propylene materials. For example, a fully confined structure can use na~ural rubber of about 50 Durometer and 1500 p.s~i., Other values for bearings of the load range indica~ed above can be calculated by those skilled in the art~
In some embodiments it may be desired to use a material of strength and hardness that for the preferred dimensions of the strips 44 does not give the required amount of deflection, and in such cases ~he modification of Figure S or 6 may be used.
Figure 5 shows an arrangement in which each strip 44 is provided with a plurality of spaced bores such as 47 extending from the surface contactins the plate 16 to that contacting the low friction s-trip 40, while Figure 6 shows an arrangement in which the face of the strip 44 contacting the plate 16 is provided with a plurality of spaced recesses 480 In both of these arrangements the shape factor and the deflection characteristic of the strip is altered by the presence of the bores or recesses~ Yet other embodiments may use a mixture of bores and recesses~
It is preferred that the amount of misalignment accommo-dated by the resilient mounting of the guide means be not greater than about 1 - 2 degrees, since otherwise the amount of deformation of the low friction rubbing strlps 38 and ~0 that is required becomes somewhat largex than is considered desirable~
~ 3~
~lowcver there is still the possibility that the arnount of mis-alignment encountered in practice exceeds this figure, and such greater misalignmellt ~referably i5 met in a bearing in accorclance with the invention by another system to be described below.
S Thus, it is found with bearings of my prior invention that with the structure illustrated, in which the annular bearing element 14 is confined around its circumferential boundary by limiting rings 18 and 20, that there is no need to fasten the bearing element to the plates 16 and 26, the load of the supported structure being ample to retain the element in its operative position~
Normally the friction between the materials of the element 14 and the cast steel surface of the plates 16 a/nd 26 is qui-te high and, in accordance with this invention this friction is reduced to a low value, for example as illustrated, ~y`, interposing between the element and the plate 16 a low-fiction layer, consisting in this embodiment of a thin layer of polished stainless steel 50 fastened to the surface of the plate 16, as by continuous welding, and a thin layer 52 of a low friction material, such as polytetrafluorethylene, affixed to the immediately adjacent surface of the element 14, so that the layers 50 and 52 are in sliding contact with one another. If now a larger mis--alignment is encountered that cannot be accomodated by the resilient mountings 44, then the plate and the element 14 are able to slide relative to one another without damage to the element.
Some transverse distortion of the element 14 will ta~e place, but it is circular in plan and such distortion therefore takes place in a chord-shaped portion thereof, so that a very sub-I () stantial misalignment must be present before any appreciablearea of the element is adversely affected. Even this small transverse distortion can of course be avoided by providing a suitably-sized gap between the element edge and the riny 18 where the distortion is anticipated. It will be noted that the low-friction layer 52 extends over the edge of the element 14 where it contacts the limiting ring 18, so as to facilitate rotation between the element 14 and the plate 16 that will usually result from misalignment and accompany the above-described trans-verse distortion~
If the polished metal layer 50 is provided only a thinlayer is required, for example about 1.5 mm thick. The degree of polish required is at least about 10 RMS, and it may be possible instead to polish the surface of the plate 16 to the required degree~ However, in commercial practice it will usually be more economical to provide the polished sheet as a separate light-weight element rather than attempt to polish the surface of a relatively heavy disc. The low friction material suggested for the element 52 and the strips 38 and 40 is polytetrafluorethylene since this is now a widely commercially-available material, but in some embodiments it may be preferred to use a filled one of these materials because of its increased load capacity, despite the usual increase in friction coefficient for such materials; the higher friction can in some embodiments be reduced by use of a suitable grease between the metal and low friction layers~
In some embodiments of the invention it may be pre-ferred ~o employ the low friction layer 52 between the plate 16 -- lL -~ L~ 3~
and eleillellt 1~ in place of ~he resilient mountin~ of the lo~
friction la~7ers 38 and/or 40 as the methoc! of accornmodating the expected misalignment.
~ield of the Invention _ _ . _ The present invention is concerned with improvements in or rela-ting to bearings for structures, such as bridges and elevated roadways.
~eview of the Prior ~rt My prior U.S. Patent specificationsSerial Nos: 3,806,975 and 3,921,240 disclose and claim a high load structural bearing which includes a layer of an elastomer between two parallel plates to acccmmodate vertical, horizontal, tilting and rotation forces applied to the bearing by the struc-ture which it supportsO
Excessive horizontal shear forces applied to the elastomer layer are resisted by a shear restricting element~ while expected horizon-tal longitudinal movements of the supported structure are accommodated by sliding movement that takes place between two bearing members arranged for that purpose. These bearings have now obtained complete engineering and commercial acceptance, and are used extensively in many different kinds of s-tructures, principally bridges and ele~ated roadways.
While such a bearing is being installed it is essential that the direction of sliding which it is designed to permit be aligned accurately with the expected direction of movement of the supported structure, since otherwise there is a danger that excessive sideways forces, sufficient to cause binding of the sliding members, will be applied to the bearing. Even when the installation is performed by skilled and conscien-tious operators there is a danger of misalignment occuring, for example while the surrounding cement is being poured if the bearing is not held rigidly in position cluring the operation.
In recent years the designers o~ bridge structures and the like llave become more venturesome in curving the structures for both practical and aesthetic reasons, and are attempting designs with an amoun-t and/or degree of curvature that would not previously have been contemplated. ~his has placed a requirement on the bearings to accommodate the resulting non-linear movements of the structure, e.g. with temperature changes. Moreover, it is difficult to predict in practice with any degree of accuracy the average direction of such movements, adding to the above-mentioned difficulty of ensuring -that the bearing has been installed wi-th the optimum alignment for free sliding.
Definition of the Invention It is therefore an object of the invention to provide a new bearing for structures able to accommodate a degree of misalignment that would damage or disable a prior art bearing.
In accordance with the present inven-tion there is provided a supporting bearing for the support of a structure such as a bridge or elevated roadway, the bearing comprising:
a first plate member movable with the structure and on which -the s-tructure rests for support thereby;
a second plate member on which the first plate member rests for reLative longitudinal slidinc~ movemen-t between them upon corresponding movemen-t of the first plate member ~ith the structure; and longitudinal guide means comprising spaced longitudinal guide members resiliently mounted to one of the said first and second plate members and operative between the t~"o plate members to constrain the other plate member for the said relative longitudinal slidi:ng movement between them and against relative -transverse movement transverse to said longitudinal movement, the resilient mounting of the guide members permitting a small -transverse deviation relative movement in the said relative longitudinal sliding movement accommodating misalignment and/or non-linear movement between the firs-t and second plate members.
Further, in accordance with the present inven-tion there is provided a supporting bearing for -the support of a structure such as a bridge or elevated roadway, the bearing comprising:
a plate member on which -the structure rests for support thereby;
another plate member;
a radially-unconstrained layer of resilient material interposed between the first-mentioned and another plate member and supporting the latter from the former for vertical, horizontal, tilting and rotational movemen-ts, the layer of resilient material being surrounded at least at its junction with the first~men-tioned and another plate member wi-th respective restraining rings upstanding from the plate members for restraining the extent of transverse movement be-tween the layer of resllient material and tl~e respective plate member;
horizontal shear restricting means extending between the first-mentioned and another plate member for preventiny the application of excessive horizontal shear forces to the La~er of resilient material as the result of ho:rizontal movements between the plate members; and a layer of low-friction material interposed between one of the plate members and the layer of resilient material to facilitate transverse movement of the respective plate member relative to the layer of resilient material upon application of horizontal misalignment forces thereto.
- 3a -Ic~cr~ t-;oll (? ~ t~ ' Dl^a~ JS
. . . ~
i'.lrt-icul~lr ~rc:~erred embodiTnen~s o~ thc invention ~/ill now be described, by way o~ example, with reEerence to the accom~anying diagrammatic drawings, wherein:-E~IGURE 1 is a plan view of a first embodiment, parts thereof being broken away as necessary to show -the construction thereof;
FIGURE 2 is a section taken on the line 2-2 of Figure 1, FIGURE 3 is a section taken on the line 3-3 of Figure l;
FIGURE 4 is a section similar to Figure 2 of a second embodiment;
FIGURE 5 is a section similar to Figure 2 of a third embodiment;
FIGU~E 6 is a cross-section of a small portion of a guide means of the structure of any of Figures l - 5 to show a modification; and FIGURE 7 is a similar cross-section to Figure 6 of another modification.
Description of the Preferred Embodiments Referring now to Figures l to 3 a first embodiment particularly suitable for use as a bridge bearing consists of a lower plate lO, usually of circular shape in plan~ The plate usually is embedded in the concrete work (not shown) of the bridge structure and is provided with a single axially-disposed, downwardly-extending anchor pin 12 for embedding in that concrete.
An annular bearing element 14 of a suitable elastomeric material i~ s<~ncl~iched betweell ~he lowel- pl.~lt,C 10 alld an upper beariny plate 16 which is of rectan~ul.lr i}-~apc in plan, the element 14 being surrounded at its circumferential boundaries with the respective plates by respective circular limiting rin~s 18 and 20 that extend toward one another. A horizontal shear restrict-ing mechanism as disclosed in my prior patents Serial Nos.
3,806,975 and 3,921,240, consists of a pin 22 extending upward axially from the lower plate 10 and embraced by a sleeve 24 extending downward from the upper plate 16; this mechanism permits vertical, tilting and rotational movements between the two plates 10 and 16 under control of the element 14 and also a limited amount of horizontal movement, while preventing the application of excessive horizontal shear forces to the element~
The unavoidable longitudinal movements of the structure supported by the bearing are accommodated by permitting longitudinal sliding movement between the upper bearing plate 16 and an uppermost plate 26 the latter plate being fixed rigidly to the supported structure; in this embodiment is is provided with a plurality of parallel upwardly-extending anchor pins 28 which are embedded in the said supported structure. The two plates 16 and 26 have sandwiched between themselves a layer 30 of a low-friction material, such as polytetrafluroe-thylene and a thin sheet 32 of highly polished stainless steel, the latter being fastened as by continuous welding to the under surface of the uppermost plate 26. The plates 16 and 26 are constrained in their relative movement along a longitudinal axis 34 by downwardly-extending ~s~
guide bars 36 fixed ~o the undersurface of the uppermost plate, the opposed vertical edge faces of the plate 16 and the guide bars 36 being provided with respective strips 38 and 40 of low friction material e.g. polytetrafluorethlyene.
The bearing is provided at each end with a buffer stop consisting of a buffer support 54lfastened to the plate 26, a buffer plate 56 that is disposed to engage the facing edge of the plate 16, and a buffer pad 58 of-elastomeric material interposed between the support 54 and plate 56. As the bearing reaches its extreme position at either end the plate 16 engages t~e plate56 , which moves toward the support 54 compressing the pad 58, the plate being guided in such movement by rods 60 moving in correspond ing bores in the support.
Any misalignment between the axis 34 and the actual direction of attempted sliding movement of the plate 26 over the plate 16 would~ in the absence of the invention, cause unaccept-able binding between the plate 16 and the bars 36 to an extent that could seriously damage and eventually even destroy the bearing. This is prevented in accordance with the i~vention by mounting the low friction strip 38 on a thin metal backing strip 42, which is in turn mounted on a strip 44 of an elastomeric material that is thus interposed between the respective opposed vertical edges of the guide ~ar ~6 and the plate 16 along the whole length of the plate. If there is any small misalignment of the sliding movement for the reasons explained above, or such misalignment appears because the sliding movement is along a non-linear path, then this is accommodaked by expansion or compression in the elastomeric strips 44, so that th~ slidin~ tak~s ~ ~; ,, ~lace without binding.
In some alternative embodiments each low friction strip 38 is bonded directly to the elastomer strip 44, and in others the strips simply lie alongside one another and are fastened in place by bolts that are threaded into the plate 16-~ lter~ t-ivcly, or in acldil-ion, a~ e1aitomer s~ri may be interposed between the low friction strip ~0 and -the respective guide 36, as illustrated in broken lines in Figure 2.
The invention is illustra-ted as applied to a bearing in which straight-line sliding is provided between straight sliding surfaces, bu-t it will be apparent to those skilled in this particular art that the invention is also applicable to designs with which the sliding surfaces are curved.
In the embodiment of Figure 3 each strip or elastomer ma~erial is semi-confined within a longitudinal slot 46 in the respective vertical edge of the plate 16, while in the embodiment oE Figure 4 each strip 4~ is ~holly confined within its slot ~6, the strip and the slot being of substantially the same cross-sectional dimensions; in some embodiments the unconfined elastomer strip may be larger in cross-section than the slot so that it must be compressed for insertion therein and is therefore precompressed to a corresponding extent.
In a commercial range of bearings for load capacities from 100 to 8,000 KIPS the upper plate 16 varies in width from 18.1 cm to 162.6 cm, and in thickness from 1.27 cm. to 5.08 cm respectively, while the elastomeric layer 1~ varies in thickness from about 1.3 cm to about 10.1 cm. The elastomer strips vary in thickness from about 1.2 cm to 3 cm and are intended to accommodate deviations of up to about +15 degrees each, based on a permitted compressability o~ about * 15~. A suitable material for the unconfined structure o Figures 1 and 2 is a urethane of about 95 Durometer hardness and about 15,00Q p.s.i. strength.
Other materials such as polyethers can be usecl. The semi-confined and confined structures of ~igures 3 and 4 respectivel~ permit the use of lower hardness materials such as chloroprene, natural rubber and ethylene propylene materials. For example, a fully confined structure can use na~ural rubber of about 50 Durometer and 1500 p.s~i., Other values for bearings of the load range indica~ed above can be calculated by those skilled in the art~
In some embodiments it may be desired to use a material of strength and hardness that for the preferred dimensions of the strips 44 does not give the required amount of deflection, and in such cases ~he modification of Figure S or 6 may be used.
Figure 5 shows an arrangement in which each strip 44 is provided with a plurality of spaced bores such as 47 extending from the surface contactins the plate 16 to that contacting the low friction s-trip 40, while Figure 6 shows an arrangement in which the face of the strip 44 contacting the plate 16 is provided with a plurality of spaced recesses 480 In both of these arrangements the shape factor and the deflection characteristic of the strip is altered by the presence of the bores or recesses~ Yet other embodiments may use a mixture of bores and recesses~
It is preferred that the amount of misalignment accommo-dated by the resilient mounting of the guide means be not greater than about 1 - 2 degrees, since otherwise the amount of deformation of the low friction rubbing strlps 38 and ~0 that is required becomes somewhat largex than is considered desirable~
~ 3~
~lowcver there is still the possibility that the arnount of mis-alignment encountered in practice exceeds this figure, and such greater misalignmellt ~referably i5 met in a bearing in accorclance with the invention by another system to be described below.
S Thus, it is found with bearings of my prior invention that with the structure illustrated, in which the annular bearing element 14 is confined around its circumferential boundary by limiting rings 18 and 20, that there is no need to fasten the bearing element to the plates 16 and 26, the load of the supported structure being ample to retain the element in its operative position~
Normally the friction between the materials of the element 14 and the cast steel surface of the plates 16 a/nd 26 is qui-te high and, in accordance with this invention this friction is reduced to a low value, for example as illustrated, ~y`, interposing between the element and the plate 16 a low-fiction layer, consisting in this embodiment of a thin layer of polished stainless steel 50 fastened to the surface of the plate 16, as by continuous welding, and a thin layer 52 of a low friction material, such as polytetrafluorethylene, affixed to the immediately adjacent surface of the element 14, so that the layers 50 and 52 are in sliding contact with one another. If now a larger mis--alignment is encountered that cannot be accomodated by the resilient mountings 44, then the plate and the element 14 are able to slide relative to one another without damage to the element.
Some transverse distortion of the element 14 will ta~e place, but it is circular in plan and such distortion therefore takes place in a chord-shaped portion thereof, so that a very sub-I () stantial misalignment must be present before any appreciablearea of the element is adversely affected. Even this small transverse distortion can of course be avoided by providing a suitably-sized gap between the element edge and the riny 18 where the distortion is anticipated. It will be noted that the low-friction layer 52 extends over the edge of the element 14 where it contacts the limiting ring 18, so as to facilitate rotation between the element 14 and the plate 16 that will usually result from misalignment and accompany the above-described trans-verse distortion~
If the polished metal layer 50 is provided only a thinlayer is required, for example about 1.5 mm thick. The degree of polish required is at least about 10 RMS, and it may be possible instead to polish the surface of the plate 16 to the required degree~ However, in commercial practice it will usually be more economical to provide the polished sheet as a separate light-weight element rather than attempt to polish the surface of a relatively heavy disc. The low friction material suggested for the element 52 and the strips 38 and 40 is polytetrafluorethylene since this is now a widely commercially-available material, but in some embodiments it may be preferred to use a filled one of these materials because of its increased load capacity, despite the usual increase in friction coefficient for such materials; the higher friction can in some embodiments be reduced by use of a suitable grease between the metal and low friction layers~
In some embodiments of the invention it may be pre-ferred ~o employ the low friction layer 52 between the plate 16 -- lL -~ L~ 3~
and eleillellt 1~ in place of ~he resilient mountin~ of the lo~
friction la~7ers 38 and/or 40 as the methoc! of accornmodating the expected misalignment.
Claims (20)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:-
1. A supporting bearing for the support of a structure such as a bridge or elevated roadway, the bearing comprising:
a first plate member movable with the structure and on which the structure rests for support thereby;
a second plate member on which the first plate member rests for relative longitudinal sliding movement between them upon corresponding movement of the first plate member with the structure; and longitudinal guide means comprising spaced longitudinal guide members resiliently mounted to one of the said first and second plate members and operative between the two plate members to constrain the other plate member for the said relative longitudinal sliding movement between them and against relative transverse movement transverse to said longitudinal movement, the resilient mounting of the guide members permitting a small transverse deviation relative movement in the said relative longitudinal sliding movement accommodating misalignment and/or non-linear movement between the first and second plate members.
a first plate member movable with the structure and on which the structure rests for support thereby;
a second plate member on which the first plate member rests for relative longitudinal sliding movement between them upon corresponding movement of the first plate member with the structure; and longitudinal guide means comprising spaced longitudinal guide members resiliently mounted to one of the said first and second plate members and operative between the two plate members to constrain the other plate member for the said relative longitudinal sliding movement between them and against relative transverse movement transverse to said longitudinal movement, the resilient mounting of the guide members permitting a small transverse deviation relative movement in the said relative longitudinal sliding movement accommodating misalignment and/or non-linear movement between the first and second plate members.
2. A bearing as claimed in claim 1, wherein said longitudinal guide means comprise a pair of spaced guide structures mounted by the first plate member and between which the second plate member slides, and cooperating longitudinal guide members of low friction material mounted on the edges of the second plate member for respective operative engagement with the said spaced guide structures, and wherein said means resiliently mounting the longitudinal guide members comprise respective resilient members interposed between the low friction guide members and the edges of the second plate member and mounting the low friction guide members thereon so as to be movable transversely toward and away from the edges of the second plate member.
3. A bearing as claimed in claim 2, wherein the said longitudinal guide members of low friction material have the form of elongated strips thereof each mounted on a respective vertical edge of the second plate member, and wherein the said resilient members comprise respective elongated strips of resilient material each mounted on one vertical edge of the second plate member and having the respective strip of low friction material mounted thereon.
4. A bearing as claimed in claim 1, wherein said longitudinal guide means comprise a pair of spaced guide structures mounted by the first plate member and between which the second plate member slides, and respective longitudinal guide members of low friction material mounted on the guide structures for operative engagement with respective edges of the second plate member, and wherein said means resiliently mounting the longitudinal guide members comprise respective resilient members interposed between the low friction guide members and the guide structures and mounting the guide members on the guide structures so as to be movable toward and away from the guide structures.
5. A bearing as claimed in claim 4, wherein the said longitudinal members of low friction material have the form of strips thereof each mounted on a respective vertical edge of the guide structures, and wherein the said resilient members comprise respective strips of resilient material each mounted on one vertical edge of the guide structures and having the respective guide member strip of low friction material mounted thereon.
6. A bearing as claimed in claim 2, wherein the said resilient members are mounted unconstrained on the vertical edges of the second plate member.
7. A bearing as claimed in claim 2, wherein the said resilient members are each mounted in a respective recess in the vertical edges of the second plate member.
8. A bearing as claimed in claim 4, wherein the said resilient members are each mounted in a respective recess in the vertical edges of the said guide structures.
9. A bearing as claimed in claim 4, wherein the said resilent members are mounted unconstrained on the respective vertical edges of the said guide structures.
10. A bearing as claimed in claim 1, and including:
a third plate member;
a layer of resilient material interposed between the third and second plate members and supporting the latter from the former for vertical, horizontal, tilting and rotational movements;
horizontal shear restricting means extending between the second and third plate members for preventing the application of excessive horizontal shear forces to the layer of resilient material as the result of horizontal movements between the second and third plate members; and a layer of low-friction material interposed between one of the second and third plate members and the layer of resilient material to facilitate transverse movement of the respective plate member relative to the layer of resilient material upon application of horizontal misalignment forces thereto.
a third plate member;
a layer of resilient material interposed between the third and second plate members and supporting the latter from the former for vertical, horizontal, tilting and rotational movements;
horizontal shear restricting means extending between the second and third plate members for preventing the application of excessive horizontal shear forces to the layer of resilient material as the result of horizontal movements between the second and third plate members; and a layer of low-friction material interposed between one of the second and third plate members and the layer of resilient material to facilitate transverse movement of the respective plate member relative to the layer of resilient material upon application of horizontal misalignment forces thereto.
11. A bearing as claimed in claim 10, wherein the said layer of low-friction material is a layer of polytetrafluorethylene and the surface of the respective plate member engaged by the low-friction material is polished.
12. A bearing as claimed in claim 11, wherein the said polished surface of the respective plate member is provided by a thin metal layer fastened to the respective surface of the respective plate member.
13. A bearing as claimed in claim 10, wherein the layer of resilient material is surrounded at least at its junction with the second and third plate members with respective restraining rings upstanding from the plate members for restraining the extent of transverse movement between the layer of resilient material and the respective plate members.
14. A bearing as claimed in claim 13, wherein the layer of low-friction material extends over the respective edge of the layer of resilient material to facilitate rotation of the respective plate member relative to the layer of resilient material.
15. A supporting bearing for the support of a structure such as a bridge or elevated roadway, the bearing comprising:
a plate member on which the structure rests for support thereby;
another plate member;
a radially-unconstrained layer of resilient material interposed between the first-mentioned and another plate member and supporting the latter from the former for vertical, horizontal, tilting and rotational movements;
the layer of resilient material being surrounded at least at its junction with the first-mentioned and another plate member with respective restraining rings upstanding from the plate members for restraining the extent of transverse movement between the layer of resilient material and the respective plate member;
horizontal shear restricting means extending between the first-mentioned and another plate member for preventing the application of excessive horizontal shear forces to the layer of resilient material as the result of horizontal movements between the plate members; and a layer of low-friction material interposed between one of the plate members and the layer of resilient material to facilitate transverse movement of the respective plate member relative to the layer of resilient material upon application of horizontal misalignment forces thereto.
a plate member on which the structure rests for support thereby;
another plate member;
a radially-unconstrained layer of resilient material interposed between the first-mentioned and another plate member and supporting the latter from the former for vertical, horizontal, tilting and rotational movements;
the layer of resilient material being surrounded at least at its junction with the first-mentioned and another plate member with respective restraining rings upstanding from the plate members for restraining the extent of transverse movement between the layer of resilient material and the respective plate member;
horizontal shear restricting means extending between the first-mentioned and another plate member for preventing the application of excessive horizontal shear forces to the layer of resilient material as the result of horizontal movements between the plate members; and a layer of low-friction material interposed between one of the plate members and the layer of resilient material to facilitate transverse movement of the respective plate member relative to the layer of resilient material upon application of horizontal misalignment forces thereto.
16. A bearing as claimed in claim 15, wherein the layer of low-friction material is a layer of polytetrafluorethylene and the surface of the respective plate member engaged by the low-friction material is polished.
17. A bearing as claimed in claim 16, wherein the polished surface of the respective plate member is provided by a thin metal layer fastened to the respective surface of the respective plate member.
18. A bearing as claimed in claim 15, wherein the layer of low-friction material extends over the respective edge of the layer of resilient material to facilitate rotation of the respective plate member relative to the layer of resilient material.
19. A bearing as claimed in claim 15, wherein a thin metal layer is interposed between the layer of resilient material and the layer of low friction material, the surface of the thin metal layer contacting the layer of resilient material being roughened to increase the friction between the layers sufficiently to inhibit transverse spreading of the resilient material layer.
20. A bearing as claimed in claim 1, and including a buffer stop at each end of the said first plate and engaged by the said second plate at the end positions of its movement relative to the said first plate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US27175581A | 1981-06-09 | 1981-06-09 | |
| US271,755 | 1981-06-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1186359A true CA1186359A (en) | 1985-04-30 |
Family
ID=23036938
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000403688A Expired CA1186359A (en) | 1981-06-09 | 1982-05-25 | Bearings for structures |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1186359A (en) |
| GB (2) | GB2099932B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8400773D0 (en) * | 1984-01-12 | 1984-02-15 | Ae Plc | Structural bearings |
| DE3517895A1 (en) * | 1985-05-17 | 1986-11-20 | Friedrich Maurer Söhne GmbH & Co KG, 8000 München | Cap-type sliding bearing |
| NZ524611A (en) * | 2003-03-07 | 2005-09-30 | Robinson Seismic Ltd | Bearing assembly with sliding member between upper and lower bearing seats with elastic self-centering sleeve around seats |
| NZ535137A (en) * | 2004-09-07 | 2007-08-31 | Robinson Seismic Ip Ltd | Energy absorber |
| CN110863419B (en) * | 2019-11-29 | 2022-03-04 | 成都科利特机械制造有限公司 | Mobile trestle for underpass tunnel and construction method thereof |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1759755C3 (en) * | 1968-06-05 | 1974-04-18 | Fa. Friedrich Maurer Soehne, 8000 Muenchen | Rubber cup bearings for structures, especially for bridges |
| DE2007767B2 (en) * | 1970-02-20 | 1974-01-03 | Andrae, Wolfhart, Dr.-Ing., 7000 Stuttgart | Slide and tilt bearings for bridges and similar structures |
| US3924907A (en) * | 1974-10-29 | 1975-12-09 | Felt Products Mfg Co | Bearing pad and bridge construction |
| GB1530270A (en) * | 1974-12-27 | 1978-10-25 | Kober Ag | Bearings for bridges or similar structures |
-
1982
- 1982-05-25 CA CA000403688A patent/CA1186359A/en not_active Expired
- 1982-06-08 GB GB8216588A patent/GB2099932B/en not_active Expired
-
1983
- 1983-07-22 GB GB08319851A patent/GB2122276B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2122276A (en) | 1984-01-11 |
| GB2099932A (en) | 1982-12-15 |
| GB8319851D0 (en) | 1983-08-24 |
| GB2099932B (en) | 1985-06-05 |
| GB2122276B (en) | 1985-05-30 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |