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Uniaxial rotation bearings of the rocker and roller types have long played a significant role in the design and construction of bridges. With their cylindrically shaped rocking/rolling surfaces, they are able to facilitate high rotations about one axis while transferring large loads normal to that axis in a linear fashion – unlike “round” bearings such as RESTON®SPHERICAL and RESTON®POT whose core parts are essentially as wide as they are long. This feature of rocker and roller bearings can come in very useful in bridges whose superstructures do not experience rotations about their longitudinal axis, if the space available for bearings is limited in the direction of the bridge’s span. However, the high pressures arising along the line of contact between the curved rocker/roller element of traditional designs and the flat surface it presses against can result in damage to the bearing, in particular to sliding surfaces, requiring the bearing to be repaired or replaced.
Avoiding the high stresses that can arise along the line of contact, the RESTON®CYLINDER bearing accommodates rotations not by rocking or by rolling on a flat surface, but by sliding on a curved surface. This spreads the load not along a narrow strip but over a much larger area, the size of which can be adapted to carry higher loads simply by increasing the length of the bearing. The sliding interfaces above and below the central rotation element are equipped with mageba’s high-performance ROBO®SLIDE sliding material, which is twice as strong as PTFE and many times more durable.
To further increase the usefulness and functionality of the RESTON®CYLINDER bearing, mageba has developed the DUPLO version, which has two curved rotation surfaces, distinguishing it from the original MONO version (described above) which has only one. As well as being able to accommodate rotations about any horizontal axis, the DUPLO version is additionally not exposed to transversely eccentric loading because the rotating central element remains centred in the curved surfaces that confine it above and below. The RESTON®CYLINDER “DUPLO” bearing may thus present an interesting alternative to other bearing types in many cases – in particular, where a longitudinally-shaped bearing is preferred to a “square” one.
Like the MONO type, the new RESTON®CYLINDER bearing of the DUPLO type facilitates translations in the x and y directions, and rotations about the y axis, but additionally (thanks to the curvature of the upper sliding surface) allows rotations about the x axis and thus a restraint-free load introduction
In the design of a RESTON®CYLINDER bearing of the DUPLO type, the radius of the upper sliding interface is fully independent of the radius of the lower sliding interface, enabling eccentricities in the direction of the bearing’s transverse axis to be minimised – an advantage that can be very important in a bridge’s design