Base Isolation Bearings & Expansion Joints

Bearings and Expansion Joints
Bridge superstructures have to be designed to permit thermal and live load strains to occur without unintended restraints. Bridge bearings have to transfer forces from the superstructure to the substructure, allowing all movements in directions designed by the designer. The two functions – transfer the loads and allow the movements only in the required directions for a long service time with little maintenance are not easy to fulfill. Different bearings for different purposes and requirements have been developed so, that the bridge designer can choose the most suitable one.
By the movement of a bridge, gaps are necessary between superstructure and substructure. Expansion joints fill the gaps, allowing traffic loads to be carried and allowing all expected displacements with low resistance. Expansion joints should provide a smooth transition, avoid noise emission as far as possible and withstand all mechanical actions and chemical attacks (de-icing) for a long time. A simple exchange of all wearing parts and the entire expansion joints should be possible.

In BUET, we study the subject to develop local expertise for quality control and quality assurance of rubber bearings and expansion joints. Maintenance, durability, life cycle analysis, replacement techniques of joints and bearings are also the points interests to address.

Base Isolation Bearings

Base isolation bearings have designed flexibility under lateral load and stiffness under vertical load. The damping characteristics in the bearings are ensured by use of either lead-plugs or high damping rubbers. We study the hysteretic behavior of high damping rubber bearings (HDRB) and lead rubber bearings (LRB) to design the hysteresis behavior and incorporation in the earthquake resistant design of structures. Not to mention, such research and development activities are closely related with the fundamental mechanics of rubber and its constitutive behavior. See further details in the section: Constitutive Model for Rubber.