Bridge over the Serio river in Ponte Nossa (BG)

The bridge cross with a single 60 m span the Serio river in Ponte Nossa connecting the village on the right orographic side with the industrial area located on the left side.

The carriageway is composed of a 3.5 m wide single lane for each direction with side 1m wide banquettes with edge guard rails that bound bycicle paths 2 m wide.

The selected solution is a structure with a couple of extradosed arches with equilibrated thrusts.

The above said configuration eliminates piers in the river bed, allows for the necessary gap over the possible swollen flood and keeps the deck at the same level of the riverside roads therefore avoiding large dimensions of the access ramps.

The arch center lines follow a 3rd order parabola and the relevant sections are hexagonal with a depth of 0.90 m and a width of 0.60 m.

The arches lean slightly towards the longitudinal axe and are connected at mid span by a double Y shaped truss built with square hollow steel sections.

The thrusts are resisted by tie beams featuring the same arch section and located outside the deck in the arch planes.

These beams are suspended from the arches with MacAlloy 460 type bars that are not prestressed because by a control during the erection phase of the theoretic deck sag the correct action distribution can be achieved.

A steel-concrete composite structure supports the deck and is constituted by transverse I shaped steel beams with variable web depth and flange width and set at 4m center lines.

A 0.22 m deep concrete plate is cast over 0.06 m deep prefabricated slabs.

All the steel works are of class S355 J0 and welded.

The abutments are supported by drilled piles and resist the seismic actions.