e-mosty March 2018. Naeem Hussain. Bridges. Naeem Hussain. Bridges. | Page 10

A. Bishopthorpe Bridge (River Ouse Bridge) York England (1971-76) Figure 1: Model of the bridge The River Ouse Bridge was the first reasonably sized bridge on which I had a chance to deploy my newly acquired knowledge of prestressed concrete. Of course it was not just about the engineering but also the environment and looks of the bridge that made it an exciting bridge to work on under the leadership of Jorgen Nissen. It is near the Archbishop of York’s Palace and carries the A64 Bypass across the river at about 45° skew angle to the alignment of the river, as shown in the model, Figure 1. There are bridle paths on both banks of the river frequented by hikers and visitors to the Palace. The local authority wanted a bridge that would be in keeping with the Palace and invited Arup to design the bridge. Figure 2: Undulating earthworks around the abutments 1/2018 With its low height the bridge would have been an unwelcome visual intrusion into the open and pleasant aspect of the river. In order to overcome the visual intrusion the abutments of the bridge are set well back from the river´s edge with landscaped undulating earthworks around the abutments, Figure 2. So as not to visually overwhelm the pedestrians walking along the river banks, the box girders carrying each carriageway are separated and have a curved parabolic soffit. The parabolic soffit visually reduces the mass of the box girders, and separation between them allows sunlight to filter through and lighten what would otherwise have been a dark unwelcome space below the bridge, Figure 3. Figure 3: Parabolic soffit and separation of box girders makes a lighter space under the bridge