The roof for the shaft in which the TBM used for the construction of urban high-speed railway tunnel in Girona was assembled consists of a series of isostatic Warren steel trusses, whose span is 24.15 m.

Trusses depth, measured as the distance between top and bottom chords, is constant and equal to 1670 mm.
Longitudinally, trusses are placed each 1.50 m.

A 4 cm depth steel grating (“tramex”), with an allowable load of 5 kN/m2, is placed on the trusses.

Trusses are entirely built using square hollow sections, braced by pairs also with transverse square hollow sections welded in the joints. Additionally, between top chords, a bracing consisting of a triangulation using L steel sections is designed.

Trusses are supported by elastomeric bearings.