On the behavior of sole plates in steel girders

Elastomeric bearing systems (elastomeric bearing pads or steel-reinforced elastomeric bearings) are used widely as a low cost option as well as for minimal maintenance. In elastomeric bearing components, the sole plates are important so as to resist not only compression but also flexural stresses due to bending of bridge girders and local stress concentration near the load-bearing diaphragm. In steel box and/or plate girders, the bottom flange and the sole plate may act together in dispersing concentrated stresses. In concrete girders, however, a major role of the sole plate is to spread the stresses into a finite area to make sure that the direct bearing stress acting on the concrete is within the allowable value specified. Although the sole plate is an important component of a bearing system, past studies have been focused on the elastomer or steel reinforcement in the elastomeric bearing system. No specific requirement is provided for the determination of the sole plate thickness in any standard specifications throughout the world. The behavior of the sole plates in the elastomeric bearing system has been investigated by a series of finite element analyses. Based on the analysis results, a simple design equation to determine the sole plate thickness is proposed. Finally, the reliability and rationality of the proposed equation is demonstrated through examples.