Influence of geometry and configuration of the spherical sliding layer of bridge bearings on the structure working capacity

Spherical bearing contact units consist of an upper steel plate with a spherical segment, a lower steel plate and antifriction polymer sliding layers (spherical and flat). Manufacturers produce the units with different positions of the flat and spherical sliding layer relative to the steel plates of the bearing. However, the effect of the antifriction layer position in the contact unit on the deformation behavior of the structure has not yet been evaluated. In this paper, the influence of the spherical sliding layer position relative to the steel structural elements on their frictional interaction is considered. Two variants associated with the position of the spherical antifriction layer are examined: the sliding layer is applied to the spherical steel segment, and it is located in the spherical notch of the lower steel plate. The design of the spherical bearings includes an interlayer made of radiation-modified fluoroplastic F-4 (no filling). The support unit with an interlayer located in the lower steel plate corresponds to the bearing model L-100 manufactured by AlfaTech LLC (Perm). The L-100 bearing is designed for a normative vertical load of 1000 kN. The maximum length and height of the structure are 155 and 54 mm, respectively, and the interlayer thickness is 4 mm. The support unit with an interlayer applied to the spherical segment is modeled with geometrical dimensions similar to those of the L-100. The standard angle of inclination of the antifriction layer end face is 30°. It was found that the detachment of the mating surfaces by more than 2% of the contact area occurs at a standard angle of the sliding layer end face in the case when the layer is applied to the spherical segment. Therefore, the influence of the inclination angle of the antifriction layer end face on the bearing deformation is considered within the framework of this work. The advantages of the spherical bearing classical design were established in a series of numerical experiments: a more uniform distribution of contact parameters over the mating surfaces, a large area of complete adhesion of the mating surfaces, small deformation of the end face of the sliding layer, etc. Based on the obtained results, the angles of inclination of the end face of the sliding layer were determined, which made it possible to achieve optimal distribution of the parameters of contact zones and the deformation characteristics of the bearings with two variants of the antifriction layer positions.