Pedestrian walkway over the Alenta Stream (BN) made of P-TREX pultruded profiles.

A structure made of pultruded fiberglass profiles, P-TREX, parallel to a bridge span damaged by rain events, was created for the crossing of utilities (water, gas, and sewerage) and for the safe execution of their maintenance.

The restoration intervention of a reinforced concrete bridge over the Alenta Stream in the municipality of Ponte, Benevento, which became impassable due to exceptional rainfall in October 2015, provided an opportunity to construct a pedestrian walkway in composite material adjacent to it for the passage of some utilities.

The flood caused by the exceptional rainfall had damaged the bridge and the attached infrastructure, prompting an urgent intervention by the municipality. In addition to restoring the bridge for vehicular passage, the reconstruction of the damaged infrastructure included the construction of a structure using pultruded fiberglass profiles, P-TREX, positioned parallel to the bridge span. This structure was designed to allow the crossing of utilities (water, gas, and sewerage) and enable their maintenance to be carried out safely.

The choice of pultruded material was based on its lightweight characteristics, reduced loads on the structure, high resistance to corrosion, atmospheric agents, and UV rays, resulting in greater durability and effectiveness of the intervention.

The walkway structure consists of a single-span truss structure with a span of 28,700 mm. It comprises two parallel Warren trusses with a height of 1,600 mm, spaced at a distance of 1,000 mm and connected by connecting cross-members and diagonal tie rods.

The truss is assembled using pultruded fiberglass profiles (P-TREX) with bolted connections and steel plates. The base of the end supports is anchored to reinforced concrete foundation footings using steel anchor bolts. The lower and upper chords and the end supports are composed of coupled C300 pultruded profiles, while the diagonals are made from coupled C200 pultruded profiles, inclined at 38° from the horizontal. Additionally, there are intermediate vertical supports (two per side) made of steel tubes with a diameter of 168.3 mm and a thickness of 10 mm to provide torsional rigidity to the structure and facilitate installation.

The bracing system consists of “X”-shaped horizontal tie rods and “V”-shaped vertical tie rods. At the level of the upper chord, IPE150 pultruded elements are installed to support the future installation of a G.F.R.P. (Glass-Fiber-Reinforced Polymer) grating walkway.

All metal elements are made of S275JR steel (UNI EN 10027-1:2016), and the connections are made using M16 cl.8.8 bolts (UNI EN 14399-4:2015). The G.F.R.P. composite profiles belong to the E23 category (UNI EN 13706-3:2003).

Construction details:

PROJECT NAME: Restoration of the Alenta Stream Bridge

CLIENT: Municipality of Ponte (BN)

RESPONSIBLE FOR THE PROJECT: Eng. Giovanna Colangelo

DESIGNER: Eng. Annamaria Zotti

ASSISTANCE TO STRUCTURAL DESIGN: Eng. Allen Dudine, Fibre Net S.p.A.

G.F.R.P. WALKWAY CONSTRUCTION: Fibre Net S.r.l.,

Udine TIMELINE: 2017-2018