Viaduct over the Alpera valley

Alpera - Alicante

Structural typology: RAILWAY BRIDGES
Date: April, 2001
Scope: Detail Design and Technical Support

This structure consists of 11 spans of 30.00 + 9 x 45.00 + 30.00 metre spans. The bridge is 13.00 m wide which allows its hosting of a two-way high-speed railway platform.

Its Structural Type is that of a continous beam post-tensioned of box cross-section. The depth of its deck is of constant 3.20 m which results in 1/14 of the main span.

The great height of approximately 17.00 m of abutment 2 and the importance of horizontal actions induced by breaking and seism condition the chosen typologies for the abutments. From an economic and a structure behavioural point of view, it seems more adequate that these horizontal forces of breaking and seism should only be transferred to the lower abutment 1. That is the reason for choosing the closed abutment Structural Type for the lower one (E-1) and the open version for the higher one (E-2).

The open abutment 2 has two shafts of variable depth placed below the supports of the deck and founded directly to the land. In order to avoid the transmission of great horizontal forces from deck to abutment, sustainment by means of POT supports was chosen which allows the gliding of the deck once the horizontal force is higher than the value of teflon friction, that is, a 5% of the vertical load.

Abutment 1 is closed with buttresses and directly founded to the ground by footing. The sustainment of the deck is also done by means of POTs as for the transmission of horizontal forces gadgets are supplied which allow slow movements and are able to act as dampers against breaking impact (which permits the deck to stay fixed to the abutment) and as dissipaters of energy against seism.

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