An optimized structural concept achieved through Form-Finding
The adopted structural system consists of a continuous curved arch with two intermediate supports. Due to the curved alignment and the small eccentricity between the deck and the arch in the plane, the deck functions in tension. A form-finding method was used to determine the geometry of the funicular polygon under permanent loads.
The location of the two intermediate supports is governed by two main considerations/constraints: firstly, the longitudinal positioning is defined by the need to balance the main span and the side spans. Specifically, the aim was to (1) minimize the bending moments in the side spans, (2) reduce the extent of earthworks, and (3) comply with the clearance requirements of the main span.
The transverse positioning of the two intermediate supports relative to the deck is determined by the goal of minimizing the corresponding horizontal reactions. Thus, the center of mass lies on a virtual chord passing through these two intermediate supports. This approach results in a lightweight and efficient structure while maintaining a dynamic appearance.
The superstructure is designed as a composite box girder. The primary objective is to maintain a simple and repetitive construction process. Accordingly, the steel box girder located beneath the concrete deck features a constant cross-section along its entire length, with thickness variations only in the end spans. The diagonals connecting the deck to the arch are aligned in radial planes and all exhibit a consistent inclination of 31° relative to the vertical axis. This arrangement positions the arches on a conical surface. Consequently, the entire steel structure can be fabricated using plates that are either flat or curved in only one direction.
The bridge is fully integrated with its intermediate supports and abutments, eliminating the need for bearings and expansion joints, along with their associated maintenance. The curved form allows a bridge of this length to be integral: thermal expansion and contraction can occur radially without imposing significant stress on the superstructure or the foundations.
