Brescia, pedestrian overpasses undergoing extraordinary maintenance

Brescia, The municipal administration has planned the verification and overall maintenance of all 19 pedestrian overpasses in via Michelangelo, via Raffaello and via Tiziano, dividing the various works into several sections that allow the expense to be supported in different years. The interventions began starting from the R2 bridge in via Raffello which, in June 2019, had been hit by a vehicle which had damaged the intrados of the deck, causing the detachment of a portion of the concrete cover and the breaking of a piece of iron. of longitudinal reinforcement of the structure.
The works on the bridge affected by the accident (started on 16 September 2019 and concluded on 15 October 2019 with a total cost of 39.328,70 euros plus VAT) were used to verify the real state of conservation of these artefacts, in order to define the best methods of intervention for subsequent excerpts.
On 30 October 2019, the executive project of the first section was approved, relating to the overpasses of via Raffaello and via Tiziano for a total of ten bridges (from R1 to R5 and from T1 to T6) drawn up by the technicians of the Social Housing Sector of the Municipality of Brescia. Due to the COVID-19 emergency, the works started on 8 June 2020, with an estimated duration of 330 consecutive calendar days.
The executing company (FL Costruzioni & Autotrasporti Srl), ahead of schedule, formally communicated that it had completed the works on 9 November 2020. The overall cost of this excerpt amounts to 243.607 euros plus VAT.
In recent days, the executive project (drawn up by the technicians of the Municipality of Brescia, Arch. Rodolfo Eoli, Eng. Luca Filippini and Arch. Gianluigi Barucco, coordinated by the Sole Manager of the Procedure, Eng. Silvia Foini) for the second excerpt was approved by the Municipal Council. , concerning the eight overpasses (from M1 to M6, R6 and C1) of via Michelangelo, via Raffaello and via Carpaccio. The total amount to be used as a basis for the tender is 290.288,41 euros plus VAT.
In the coming months the negotiated procedure for the assignment of the works will be activated with the aim of starting the works by next summer and completing them by 2021.

STATE OF THE ARTICLES
The walkways are made up of two load-bearing beams in reinforced concrete acting as parapets, between which the walkway slab was placed, also made of solid section reinforced concrete.
The walkways have a clear span between the supports of approximately 8.60 meters and a U-shaped section with wings 135/140 centimeters high and a base of 180 centimetres. The thickness of the wings is approximately 20 centimeters while that of the walkway slab is approximately 15 centimeters.
The walkways rest on the south-west side on a structure made up of a ramp and piles of rectangular section in reinforced concrete, measuring 180x20 centimetres, which discharge directly into the foundation.
Due to the reduced concrete cover of the reinforcing bars, the age of the construction and the continuous exposure to atmospheric agents, the carbonation of the concrete has reached such depths that the steel reinforcing bars are no longer in a state of passivation. The bars are therefore no longer protected against corrosion, which is evident in several places.

TYPE OF INTERVENTIONS
To preserve the structures and prevent rapid degradation, which would have led to a notable reduction in the resistance characteristics of the materials over the course of a few years, it was considered essential to carry out extraordinary maintenance work with the following:
restore the passive condition of the reinforcements in the concrete;
redo the expansion joints of the structure and waterproofing covering of the walkway;
paint with a colored resin protector;
carry out a new waterproofing of the pedestrian surfaces with a bituminous sheath to protect against rainwater infiltration, which would compromise the extrados concrete cover of the walkway and ramps;
demolish the existing flooring (cement and PVC rubber tiles and related screeds);
redo the final walking surface in bituminous conglomerate (with a three centimeter thick wear surface), laid on a new structural lightweight concrete screed, made with an adequate slope to allow the correct flow of rainwater to the drains increased exhaust;
carry out a protective and colored repainting of the existing handrails and other iron elements such as railings, plates, etc., which are part of the overpasses themselves;
completely arrange the access staircase on the C1 bridge of via Carpaccio near the bus stop of urban line 16, with the methods previously described. (2nd phase in the procurement phase with completion expected in 2021).

PREVIOUS INTERVENTIONS

The maintenance intervention was necessary due to the state of widespread degradation and obsolescence of the materials and the general appearance of the pedestrian overpasses of via Michelangelo, via Raffaello, via Tiziano and via Carpaccio. Since they were built (in the first half of the 80s), they had never been the subject of overall redevelopment interventions, but only small specific structural interventions (in 1990 the R1, M2 and M5 bridges were subjected with plates connecting the gangway ramp) and of a functional type (in 1998 handrails were added on all the ramps in the western section and in 2018 the flooring of the M3 bridge was resurfaced and the PVC was replaced with asphalt binder).