ELASTOMERIC BEARINGS

DEFINITION

Elastomeric bearings for bridges are construction elements formed by elastomer layers internally reinforced by steel sheets, forming a single compact block.

The bearings allow large structures to be accommodated, supporting different loads and allowing movements and rotations that converge on the structures so that they are not damaged.

Descargar Catálogo
Descargar Breve Catálogo

The elastomeric bearings have excellent features mechanical, since they take advantage of the low deformation modulus of this material (both for compression purposes and tangential stresses). These characteristics, together with their durability and resistance, make them essential for large civil works infrastructures, mainly bridges, viaducts, buildings, industrial warehouses and others...

To understand its behavior, we must take into account that the rubber it has no mechanisms, it in itself constitutes a complex mechanism, which allows the superstructure to move in all directions.

FUNCTION

The function of elastomeric bearings is multiple:

  • Conect the substructure and superstructure of the bridge.
  • Accommodates and transfers dynamic forces and vibrations without causing wear or destroying the substructure.
  • Allows movements (translational, vertical or rotational) of the bridge structure in reaction to the loads acting on it.
  • Control the movement of the bridge structure, the direction and degree of rotation.
  • Assures that the deformation, which occurs in the bridge superstructure, does not lead to large forces and/or moments in the substructure.
  • Can be used to adjust properties dynamic of the bridge.
  • The bearings reduce the shears at the head of the piers, viaducts or abutments.
  • They act as protectors anti-seismic.

Interbuna elastomeric bearings are installed in infrastructures of more than 30 countries.

The quality of its materials, its careful design and its controlled manufacturing together with a constant process supervision and optimization, has generated a prestige which has allowed its important presence international.

ADVANTAGES OF ELASTOMERIC SUPPORTS

They are cheap, due to the simplicity of its design, the ease of manufacturing and the relatively low cost of the raw materials, rubber and steel. 

They are effective, because they transfer loads very well and absorb the irregularities of the surfaces between which they are located, they absorb slopes of up to 2%.

They are resistant, because properly designed elastomeric bearings support compression loads as high as those required for concrete. In the same way, they withstand the deformation due to the stresses of the structure that take place in the former. 

They are durable, because on the inside the natural rubber (NR) has excellent mechanical characteristics, and on the outside the rubber, which can also be polychloroprene rubber (CR), combines with the properties of NR a great resistance to weathering, ozone, it is self-extinguishing and withstands high temperatures. Both rubbers also have the advantage of being highly compatible, behaving as one before, during and after the vulcanization process. Both also withstand extremely low temperatures of up to -40ºC.

They hardly require maintenance. The elastomeric bearings for bridges manufactured by Interbuna do not deteriorate, and only periodic monitoring is necessary. They are replaceable bearings and can be changed very easily.

TYPES OF STANDARD ELASTOMERIC SUPPORTS

  • They are elastomeric bearings reinforced with a single sheet.
  • Have two layers of elastomer between which a very resistant steel sheet is inserted.
  • They have a thickness fixed of 10mm.
  • They are used for center loads of prefabricated parts and compensate its lack of parallelism.
  • The load admissible work load is 15N/mm2 and the displacement maximum is 5,6mm.
  • They are also used for absorb small defects on concrete surfaces.
  • The armed bearings are laminated supports manufactured with layers of elastomer, which are interspersed with highly resistant steel sheets, joined by a careful vulcanization process.
  • They support loads verticals of up to 15,000 kN, as well as displacements and turns in all directions.
  • They are used in bridges concrete and metal of all kinds, industrial buildings and warehouses, warehouses and silos.
  • The maximum load of work is from 10 to 15 MPa depending on its size.
  • The displacement allowable varies from 50% to 70% of its net rubber thickness.
  • Anchored supports type C2
    • They are reinforced supports vulcanized with steel plates on their external faces to be anchored to the structure and prevent lateral displacements.
    • The exterior steel plates or anchor plates can be embedded to be anchored by thread or cantilevered to be anchored by welding or by means of a screwed connection. 
    • They are designed for concreting in situ to the anchoring plates of the supports.
  • Supports with key type C4
    • They consist of a type C2 support with embedded plates joined in turn to another pair of external plates flown by means of shear discs.
    • It prevents sliding due to horizontal forces to a certain extent.
  • Embossed supports type C5
    • They are similar in the C2 supports, but with the outer plates with a drawing.
    • They are indicated when they are glued with resin or mortar to the structure.
    • They are mainly used in prefabricated pieces, although they can also be used for in-situ concreting.
    • It should only be used for structures with not very high horizontal loads.
  • They support vertical loads of up to 20,000 kN, as well as movements and rotations in all directions.
  • All except type C5 accept guides, locks, etc.
  • They are used when the minimum vertical load does not guarantee that sliding will not occur due to lack of friction. Also when traction efforts occur.
  • It is an armed bearing with a vulcanized Teflon surface.
  • Its dimensions are determined according to the existing displacements and efforts.
  • They are always associated with an upper sliding surface that consists of a thin sheet of polished stainless steel that is welded to a steel plate of a significantly greater thickness that allows them to work.
  • They support vertical loads of up to 20,000 kN, as well as movements and rotations in all directions.
  • It is a bearing anchored with a honeycomb Teflon sheet embedded in a plate vulcanized to the support. Its dimensions are determined according to the existing displacements and efforts. They can have guides, locks and all the accessories that non-sliding anchored bearings accept.
  • They are always associated with an upper sliding surface that consists of a thin sheet of polished stainless steel that is welded to a steel plate of a significantly greater thickness that allows them to work.
  • They support vertical loads of up to 20,000 kN, as well as movements and rotations in all directions.
  • They are manufactured only with elastomer, and their allowable working load ranges from 1.5 to 5 N/mm2. They are commonly used in buildings, stairs and roofs of industrial warehouses to support not very heavy prefabricated concrete pieces. It is recommended, as in type A elastomeric bearings, that they be about 20 mm smaller than the work surfaces in contact with them. They are very suitable for point loads of up to 150 kN.

COMPONENTS AND MATERIALS OF ELASTOMERIC BEARINGS

The materials used for the elastomeric bearings are S235JR quality steel, natural rubber (NR) and polychloroprene rubber (CR). In this sense, it should be noted that there are three qualities of rubber: natural rubber (NR), polychloroprene rubber (CR) and NR lined with CR.

Reinforced elastomeric bearings are always manufactured with one or several highly resistant steel sheets, depending on the model. These steel sheets are joined to the metal thanks to a careful vulcanization process. In the case of elastomeric supports without assembling the
only material is elastomer. The interior steel plates are always completely covered, thus preventing rust.

All the materials used for the elastomeric bearings that we use are adapted to the special requirements of the EN 1337-3 standard and PTFE adapted to the requirements established by EN 1337-2, unless a different grade is specified.

At Interbuna, the traceability of all components can be followed.

Quality and certificates that accredit it

All our elastomeric supports for bridges are certified within the ISO-9000 standard of the general quality system.

In elastomeric bearings, as in the rest of the infrastructure supports that we manufacture, we carry out the actual control on the piece, as required by the European standard EN-1337-3, with tests on the finished support. This certificate is marked by the European Union for elastomeric bearings of all types A, B, C, D, E and F.

We also manufacture elastomeric bearings in accordance with all international and customer-specific standards in force in the market: Europe and Africa (BS 5400, DIN 4141, Norway, Belgian and Dutch); America (AASHTO [ASTM], MCV 05, Mexican, Colombian and Peruvian); ASIA: (NH STD, NIS [INDIA]).

Elastomeric bearings are manufactured according to the dimensions of each specific project, taking into account that they must withstand high vertical and horizontal loads and movements. The calculation of the reinforced elastomeric bearings must take into account the following basic considerations:

  • The maximum compression load should not exceed 100 – 150 Kg/cm², depending on the dimensions of the support.
  • The maximum deformation of the support resulting from vertical loads must not exceed 15% of the initial net rubber thickness of the support.
  • The horizontal displacement, in permanent deformations, must not exceed 70% of the net rubber thickness of the support.
  • The height of the rubber as a whole must not exceed 25% of the measurement of the smallest side of the structural support or of the diameter.
  • To prevent it from moving on the structure, the minimum load pressure on a structural support must be 30 Kg/cm² or 50 Kg/cm2 if its plan surface is greater than that of a circle with a diameter of 350mm. Otherwise, it is recommended to install Type C anchored bearings.

INSTALLATION, INSPECTION AND MAINTENANCE

The bearings must be placed on a horizontal and dry surface. For in situ installation, the support must be protected to avoid contact of its faces with mortar or cement.

  • Elastomeric bearings are normally placed, without anchoring, on a bed of smooth and level mortar (high compressive strength cement mortar). When placing the support, make sure that the base is absolutely horizontal.
  • The formwork for the construction of the leveling layer must be very tight to prevent the mortar or cement from spilling over the sides, so that it can subsequently affect the movement capacity (tilt, twist) of the support. The formwork should be easy to remove (styrofoam or expanded polystyrene is the most suitable material for the task).
  • After installation, it is advisable to carefully remove the polystyrene after the structure has set. It must be cleaned with a suitable detergent to avoid any eventual contamination that may have occurred with the cement or mortar. The means used must not damage the elastomeric bearings in any case.
  • The metal parts of the bearings exposed to the elements must be coated with a suitable anti-corrosion coating system according to EN 1337-9.
  • Elastomeric bearings should generally be positioned so that they can be replaced without difficulty.

Inspection and maintenance of elastomeric bearings for bridges

Our elastomeric bridge bearings are manufactured so that frequent and costly maintenance is not necessary under normal conditions.

However, the following points must be checked during the bridge inspection:

  • Position of the elastomeric bearing.
  • Contact area between the elastomeric bearing and the surfaces of the structure.
  • Surface condition of the elastomeric bearing (cracks, deflection).
  • Permanence of the horizontal displacement within the permitted tolerances.
  • Permanence of rotation within permitted tolerances.
  • Condition of sliding surfaces.
  • Corrosion protection status (1).

Professional assessment of the condition of elastomeric bridge bearings requires a high degree of knowledge and experience, and can only be performed by a qualified person.

It must be taken into account that the useful life of a structure can sometimes be
considerably longer than the useful life of the structural supports. Fortunately, today, the design of supports in accordance with the EN 1337 standard allows in many cases the exchange of each component of the support. Therefore, currently it is not usually necessary to change all the bridge supports.

(1) Simultaneous movement of the retention systems and guides may cause abrasion of the lining system. This abrasion is normally limited to the top layer and is not considered a defect.)

PROJECTS

OUR FLEXIBILITY GOES FAR:
LEARN ABOUT THE PROJECTS WE HAVE ALREADY CARRIED OUT
IN MORE THAN 30 COUNTRIES.

See the projects

CONTACT

WE ARE HERE
TO ADVISE YOU

If you want to know how we can help you or have any questions about our products or services, write to us. We will study your case to design the solution that best suits your project.

A Cacesa commercial that emerged in the late 90s
with a clearly international character and basically focused
in elastomeric bearing and expansion joints for bridges.

© 2021 INTERBUNA – Legal notice | Política de privacidad | Cookies policy | Política de calidad