road and rail bridges over the rhône at st-triphon

client :

cantons of valais and vaud

programme :

road and rail bridges

dates :

competition, 2017

integration in the landscape

when looking at the landscape, the main collombey-ollon road and the railway are perceived as a single linear element. similarly, the proposed bridge is a single body, made up of two members: the road bridge and the railway bridge, with their shared geometry in relation to the river, maintain a close relationship, using the same structural language while responding individually to the specific loads to which they are subject.

expression

the silhouette of the bridge faithfully expresses the forces acting on it, while the geometry of the lateral beams follows the lines of the bending moments, creating beams that alternate above and below the deck. these beams also vary in thickness, from 40cm where the stresses are low to 90cm at the locations of the prestressing cables, enabling the materials to be utilised to full effect and giving the structure a sculptural character.

structural design

each bridge comprises two lateral prestressed beams and a reinforced concrete deck. the deck is horizontal and capable of taking compression, while the prestressing cable with tensile strength has a variable geometry perfectly adapted to the bending stresses. where the cable intersects with the deck, resistance of the section to bending is provided by passive reinforcement. each bridge is a beam on three supports, with the central pier forming the fixed point and the ends supported by sliding elements located in the abutments.

the tensioning of the prestressing is carried out entirely within the abutments, where the mobile anchors are accessible from cable shafts within the abutments.