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Bearings

Bridges neoprene bearings

Neopren bearings are elements that ensure the transmission of requests of any nature from the superstructure to the infrastructure. This neopren bearings  must be so constructed as to allow the translation and rotation movements of the superstructure within certain limits without creating unforeseen demands in any of the bridge elements.

Neoprene bearings are made up of successive layers of neoprene and fret, vulcanized in a mold under high temperature and high pressure conditions.
Neoprene support devices for railroad and road bridges consisting of polychloroprene rubber (Neoprene) or natural rubber scrubbed with steel sheets (frets) are for reactions ranging from 200 KN to 5000 KN.

The temperature variation considered for the calculation of such neoprene devices is between -35 ° C and + 50 ° C. Within the load and displacement capabilities, these neoprene devices can also be used to support other industrial applications.

The dimensioning is done taking into account vertical and horizontal loads, linear deformations, spins, so that the neoprene supports support the conditions of resistance and stability.
The thickness of the neoprene intermediate layers will be 8.12 mm, recommending the minimum thickness. The reinforcement of these neoprene devices is made of OL37 sheets with thickness between 2 mm and 4 mm depending on the size of these devices.
The physical and mechanical characteristics of the neoprene blend must meet the conditions set out in the table below:

neopren bearings  characteristics Admissibility conditions
Hardness (degrees Shore A) 60 ± 5
Minimum tensile strength (N/mm2) 12
Minimum elongation at break (%) 400
Maximal residual deformation at compression (%) 10
Accelerated aging resistance: – maximum loss in breaking strength (%) – maximum drop in elongation at break (%) – maximum hardness increase (Shore A grade) 153010
Variation of Physical and Mechanical Characteristics after Immersion in Oil No. 1: – Hardness (Shore A) – maximum breaking strength (%) – maximum breaking strength (%) ±5-15-15
Temperature limit of unfractionality -35
Ozone resistance After 100 hours, do not crack
Minimal adhesion of the rubber to the metal when assembled between two parallel metal plates (N/mm2) 1.7

Neoprene bearings or container bearings are a verified type of bridge bridges, used for a long time in bridge construction around the world. Due to the uncoated (natural rubber) rubber-to-steel / rubber-to-steel combination (container), it is possible to transfer advanced vertical weights to a small area. The size of the construction of these bearing / container bearings depends on the pressure allowed in the rubber and, above all, the pressure allowed in the concrete.
Gumba container bearings are of different sizes and are manufactured in accordance with EN 1337-5 and EN 1337-2. All Gumba container bearings are CE certified.

How Gumba Container Bearings Work

The rubber support in the bearing steel of the bearing is incompressible and at high pressures the support behaves like a liquid. Its deformation capacity allows tilting / folding around its axes.
Our three-sealing system prevents dust and moisture from entering and leakage of pressurized rubber. This system consists of:
– the brass gasket – it is located between the container and the container shell and holds the rubber inside the container when pressurized.
– special synthetic gasket – it is placed over the brass gasket and provides extra protection against moisture. This is a significant improvement compared to other container bearings, since the internal bearing surfaces of the container bearings have no corrosion protection.
– external cut – it prevents the entry of dust and spraying water.
Different types of container bearings (multi-directional, one-way and fixed motion) are determined by the construction of the container shell. Cell duplicate disc is made of PTFE with lubricant reservoir and a sliding surface of the lapping 1.4404 stainless steel (austenitic stainless steel C? 0.03%, Cr = 16.5 ÷ 18.5%, Ni = 11 to 14%, Mo = 2 ÷ 2.5%). The dimensions and location of the mobile pairs comply with the requirements of EN 1337-2.

Container bearings are usually not fixed with the construction parts around, as the minimum weight is in most cases high enough to keep them in position. Fastening can be done by adding anchor plates, if the actual weight requires fixing.
The dimensions of the standard bearings allow the anchor plates not to require simultaneous effects of the vertical and horizontal forces.

Standard types bearings with slide containers:

Neoprene bearing devices TGa – multi-directional slip bearings
TGe – uni-directional slip bearings
TF –fixed bearings
Maximum weight max.Nz,d =1000-12000 kN max.Nz,d =1000-12000 kN max.Nz,d =1000-12000 kN
Minimum weight min.Nz,d =0,4 x max. Nz,d min.Nz,d =0,4 x max. Nz,d min.Nz,d =0,4 x max. Nz,d
Horizontal force Vy,d= 0,1 x Nz,d Vy,d= 0,1 x Nz,d
Displacement longitudinal : ± 50 mmpana la ± 100 mmtransversal : ± 20 mm longitudinal = ±50 mmsi: ± 100 mm
Angle of rotation 0,01 rad 0,01 rad 0,01 rad
Pressure on concrete min. concrete quality C30/37 min. concrete quality C30/37 min. concrete quality C30/37

Neoprene bearings or ball bearings are ball bearings made of steel. Their unique concept allows the transfer of vertical forces, displacement / pushing of motion and longitudinal and transverse rotation. Adding the control conductors is also possible to support horizontal forces.
Ball bearings ELA-Bruckenlager are manufactured and dimensioned to EN 1337-7 and EN 1337-2. All bearings ELA-Bruckenlager bear CE mark.

How do these devices work in neoprene or ball bearings?

Neoprene or ball bearings (ball bearings) consist of a flat, hard, convex, chrome plated calotte, placed in a convex steel mount, which contains a PTFE disc with lubrication tanks. This allows folding / inclining in all directions. Another PTFE disc with lubrication tanks is located at the top of the cap. The duplicate is a sliding plate made of 1.4404 stainless steel (austenitic stainless steel C = 0.03%, Cr = 16.5 ÷ 18.5%, Ni = 11 ÷ 14%, Mo = 2 ÷ 2.5%) and resistant to the shearing effort of another steel plate at the top of the cap. The dimensions and location of the mobile pairs comply with the requirements of EN 1337-2.
To prevent the entry of dust and moisture, a guard is used instead of the application. We support bearings or ball bearings with multi-directional and one-way movements are provided with a motion viewing scale. Supporting devices (Spherical bearings) are usually not fixed with the construction parts around, as the minimum weight is in most cases high enough to keep them in position. Fastening can be done by adding the so-called anchoring plates if the actual weight requires fastening. The dimensions of the standard spherical bearings allow the anchor plates to not require simultaneous effects of the vertical and horizontal forces.

Standard types of spherical sliding bearings:

Bearings KGa – multi-directional slip ball bearings
KGI/KGq –uni-directional slip ball bearings
Kf – fixed ball bearings
Maximum weight max.Nz,d =1000-20000 kN max.Nz,d =1000-20000 kN max.Nz,d =1000-20000 kN
Minimum weight min.Nz,d =0,4 x max. Nz,d min.Nz,d =0,4 x max. Nz,d min.Nz,d =0,4 x max. Nz,d
Horizontal force KGI: Hx,d= 0,1 x Nz,dKGq : Hy,d= 0,1 x Nz,d Hxy,d= 0,1 x Nz,d
Displacement longitudinal : ± 50 mmpana la ± 150 mmtransversal : ± 20 mm KGI: Vy,d= ±20 mmKGq: Vx,d= ±50 mmpana la: ± 150 mm
Angle of rotation 0,01 rad 0,01 rad 0,01 rad
Pressure on concrete min. concrete quality C30/37 min. concrete quality C30/37 min. concrete quality C30/37

The reinforced elastomeric supports are made of a special rubber compound and are equipped with an armored steel sheet during the manufacturing process, so-called vulcanization. Steel sheets provide the necessary rigidity. Strong elastomeric supports are noted for their low maintenance and durability. Besides this, some types of elastomeric supports can be used under certain conditions without the additional steel (limiting) structure.

The elastomeric part of the support is elastically deformable. The degree of deformation in vertical direction (deflection) under permanent load is calculable and remains constant. The influences of dynamic loads are generally small and the additional temporary deflections caused by the dynamic loads are small and will not cause problems for most structures.

There are different types of reinforced elastomeric supports. Various types are defined in EN 1337-3. The most common types are:

Elastomeric support type B (1) – hardened elastomeric support, fully covered with elastomer and containing at least two reinforced steel plates. Permanent pregnancy must be sufficient to prevent slippage.

Elastomeric Type B / C (1/2) – Elastomeric support reinforced with an external steel plate on one of the surfaces. The steel sheet allows the use of any slip protection methods such as dowels, threaded rods, screws, etc. The only slip protection on one side allows easy installation of the stand and replacement. Anti-slip protection is required at a pressure lower than the minimum support pressure. The type of reinforced elastomeric support B / C can be installed if the construction is secured in its position, e.g., by a support which is fixed in all directions or transversely.

This type of reinforced elastomeric support has always been used in German railway bridges, regardless of the actual load situation. An additional application for this type of support is the use as anchored buffer eg for buildings.

The elastomeric C (2) support – reinforced elastomeric support, both substrate surfaces are made of steel plates to protect against slipping. Replacement of hardened elastomeric supports of this type is difficult to do without additional measures. As a floating support, this type may, depending on the rigidity, transfer horizontal loads (breaks, etc.)

The elastomeric C-type (5) support – hardened elastomeric support, both surfaces of the substrate are protected against sliding of profiled steel sheets. (eg grooves, slip resistant steel plates). However, due to the fact that the required tasks can not be precisely defined, it should be used only for structures with minor loads or for building construction. Because of the profiled surfaces it can not be equipped with limiting structures.

Fire behavior
Strengthened elastomeric supports made of chloroprene rubber are slightly flammable. The fire extinguishes itself after the flame has been extinguished.

The limiting structures are steel components that surround reinforced elastomeric supports. They transmit the horizontal load from the superstructure to the substructure.

Among the current horizontal loads are the wind, the resetting forces from translation, breaking, friction, and centrifugal forces at curved bridges.

Depending on the type of limitation, the brackets on the top and bottom bracket may transmit particular loads such as:

Fx = the longitudinal force (kN)
Fy = transverse forces (kN)

Vx= moving in the direction x (mm)
Vy = moving in the direction y (mm)

Note: In practical application “x” is always the main direction (longitudinal direction) of the bridges.

Bridge limiting structures for bridges are divided into Group I and Group II. Group I (with sliding pair – steel / steel) are manufactured for travel? 50 mm (SLS) or railway bridges with a prolonged length of? 25 m. Limiting structures for Group II bridges (sliding pair – stainless steel / sliding material) are applicable to structures where Group I can not be used.

The sizing of bridge limiting structures is based on the available structural values. The limiting structures are adapted to the structural site (site conditions, installation height, etc.)

Elastomeric reinforced supports with the most common limitation structures:

Fixed longitudinal structures

– the support is fixed in the direction of longitudinal construction. Forces in this direction are transmitted.

Cross-fixed limitation structures
– the support is fixed in the direction of cross-construction. Forces in this direction are transmitted.

Restriction structures fixed in all directions
– the support is fixed in the longitudinal and transverse construction directions. The forces in these directions are transmitted.

For the choice of the support plane, that is, the type and position of the limiting structures, it must be taken into account that the bridge or the structure as a whole must be able to expand without limitation.

The superstructure and the substructure can be connected in various ways. The type of the limiting structure is irrelevant to the login method.

Vertical combined loads and horizontal forces can be transmitted with limiting structures. When horizontal forces are high, it is often more economical to direct horizontal forces into the substructure by means of horizontal load carriers and directional supports.
Horizontal loading supports transmit the longitudinal and / or transverse forces. The guide supports allow both horizontal axle and horizontal displacement supports on the other axis. In addition, vertical displacements may optionally be absorbed by both supports to meet specific structural requirements.
A significant advantage is that horizontal load carriers absorb the horizontal forces even under changing load conditions, thus eliminating additional structural methods (stabilizing the position of feathers, etc.).
Horizontal loading supports and directional supports are manufactured to EN 1337-8.

The limits of the elastomeric supports on the ability to withstand large, rare or single horizontal displacements can be improved by using an adjustable support. The adjustable holder is an elastomeric support with an additional adjusting device.
With the adjusting device, the elastomeric support can be moved in the horizontal direction without lifting the superstructure. Rare or unique construction changes (fixed point modification, concrete deformation or contraction, changes to the foundation) are thus transferable with lower elastomeric supports. The elastomeric support only transfers shifts and short and long rotation (wind, traffic, temperature fluctuations, deformation and contraction).

Separation of loads can reduce drastic support height and in some unfavorable conditions the adjustable support can be the only economically or technically possible solution.
Practically adjusting the support takes place before allowing traffic on the structure. Pre-setting the support (considering the actual actual building temperature) is done in accordance with the expected residual displacements.
In time (after months), the reglabioll deforms the initial position, and the support allows short and seasonal movements as well as rotations.
The adjustable deformation supports extend the limited performance of the elastomeric supports as far as the absorption of non-recurrent, or less recurrent, horizontal movements.
Effects due to movement, strain, temperature, produce non-recurrent movements that often lead to excessively high elastomer supports and, implicitly, very high recovery forces. The adjustable supports allow the elastomer support to be moved to the initial position (zero position or below, without the structure being raised, even under active loads.

Strong tension supports allow absorption of tension forces and, if necessary, horizontal movements, but can not absorb vertical loads. If necessary, strong tensioning supports must be installed besides compression supports as they are supported with a wide structural potential.

Mounting brackets are supports used to center tasks and achieve parallelism. The mounting brackets are made of metal plates inside which are mounted the neoprene bearings.
Mounting brackets with seating metal plates vary in size depending on the size of the neoprene support device and are designed for the type of support and modulin that is used.

Types of metal plates for mounting brackets:

Free metal plates for mounting brackets
– They are used for multi-directional support devices.

Metal plates with longitudinal or transverse locking
– They are used for unidirectional motion devices.

Metal plates with locks for mounting brackets
– They are used for fixed support devices.

Plates with free standing
– They are placed on a bed of epoxy resin or on a special mortar that ensures their flatness

Metal plates with anchoring possibilities
– The metal plates are anchored in the provided space, on the saw or on the bottom and on the upper beam. Neoprene supports can not be mounted without fixing them in these metal mounts.