While the Alamillo Bridge is dramatic and widely acclaimed aesthetically, an analysis of its structural engineering show that it has an inefficient dynamic structural form because of the lack of backstays or anchorage to provide a restoring force under changing loads.
One indication of this is the extreme weight of the pylon member needed in the Alamillo Bridge compared with other cable-stayed bridges such as the Erasmus Bridge in Rotterdam, which has a backward-inclined pylon and backstays.
 The total mass of the pylon of the Alamillo Bridge is over 10 times the pylon mass of the Erasmus Bridge, which has even a longer span than the Alamillo.
While the Alamillo Bridge is dramatic and widely acclaimed aesthetically, an analysis of its structural engineering show that it has an inefficient dynamic structural form because of the lack of backstays or anchorage to provide a restoring force under changing loads. One indication of this is the extreme weight of the pylon member needed in the Alamillo Bridge compared with other cable-stayed bridges such as the Erasmus Bridge in Rotterdam, which has a backward-inclined pylon and backstays.  The total mass of the pylon of the Alamillo Bridge is over 10 times the pylon mass of the Erasmus Bridge, which has even a longer span than the Alamillo.
Alamillo Bridge