Bridge Expansion Joint for Bridges with Curved Girders

Bridges with horizontally curved girders experience multi-directional thermal movements that are more complex than the primarily longitudinal movements of straight bridges. The expansion joint must accommodate these multi-directional movements while maintaining waterproofing and structural integrity. Thermal movement of curved girder bridges is directed along the radius of curvature, not along the bridge axis. For a bridge with a horizontal curve radius of 300 meters and a total length of 150 meters, the thermal movement at the end joint has both longitudinal and lateral components. The lateral component may be 30-40% of the total movement. Girder rotation at the end of a curved bridge creates an angular movement at the joint location. As the curved girder expands thermally, the end of the girder rotates about the center of curvature. This rotation creates a change in the angle between the two edge beams, which the joint must accommodate. Edge beam geometry for curved bridge joints must follow the curve of the bridge. The edge beams are curved in plan to match the bridge geometry, requiring custom fabrication. The anchor bolt pattern must be adjusted to maintain the required spacing along the curved edge beam. Movement calculation for curved bridge joints must use vector analysis to determine the total movement at each joint location. The longitudinal, lateral, and rotational components must be combined to determine the resultant movement vector. The joint must be capable of accommodating this resultant movement in all directions. Seal selection for curved bridge joints must consider the multi-directional movement. Standard strip seal profiles are designed for primarily longitudinal movement and may not perform well under combined longitudinal and lateral movement. Custom seal profiles or modular joint systems may be required for bridges with large lateral movement components.