Strip Seal Expansion Joint Design for Curved Highway Bridges

Curved highway bridges experience multi-directional thermal movements that must be accommodated by the expansion joint. Unlike straight bridges where movement is primarily longitudinal, curved bridges also experience lateral and rotational movements that complicate joint design. The thermal movement of a curved bridge is directed along the radius of curvature, not along the bridge axis. For a bridge with a horizontal curve radius of 500 meters and a total length of 200 meters, the thermal movement at the end joint has both longitudinal and lateral components. The lateral component may be 20-30% of the total movement, which must be accommodated by the joint. Strip seal joints can accommodate limited lateral movement through the flexibility of the EPDM seal. The seal can deflect laterally while maintaining waterproofing, but the lateral movement capacity is limited by the seal geometry. For curved bridges with significant lateral movement, the joint must be designed with a wider seal to accommodate the combined longitudinal and lateral movement. The edge beam geometry must be modified for curved bridges. The edge beams follow the curve of the bridge, requiring custom fabrication to the correct radius. The anchor bolt pattern must be adjusted to maintain the required spacing along the curved edge beam. The seal groove must be machined to the correct radius to ensure proper seal seating. Rotational movement at the joint occurs when the two bridge spans rotate relative to each other due to differential thermal expansion or differential live load deflection. This rotation creates a change in the angle between the two edge beams, which the seal must accommodate. For most highway bridges, the rotational movement is small and can be accommodated by standard seal profiles. Movement calculation for curved bridges 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.