Viaduct, Overbridges and Underbridges, A4 Motorway
The A4 motorway in northern Portugal connects the cities of Oporto and Amarante. The motorway has a number of bridges and flyovers. This flyover is of special interest due its curvature on plan and to the use of tridimensional pre-stress.
The flyover has five spans in a total length of 140 metres. Of the total length only 22 metres are straight. The bridge has a single carriageway with walkways in both sides. The deck section is a flat tee with two to four central void formers to reduce the self weight.
The profiles of the post tensioned cables are curved in three dimensions. The profiles were chosen to reduce the torsion effects caused by the curvature on the plan.