Lengthening and Reinforcement of Underpasses on the North Highway - A1 – Feira / Carvalhos Sub-stretch

The widening of the A1 North Highway to 2x3 lanes, with a future widening to 2x4 lanes foreseen, forced the extension, by about 5 m on each side, of eight Underpasses and structural reinforcement in five of them, in the Sub- Feira/Carvalhos section (six on the IC24/Carvalhos section and two on the Feira/IC24 section)

THE  enlargement solution  developed by PC&A consisted of the creation of three-span decks, supported on micropiles driven into the back of the existing wing walls. Thus, the new decks were designed with a geometry similar to the transom of the porticos but with a much larger span, being therefore longitudinally prestressed.

In this way, the intervention in the existing works was limited to the demolition of the edges of the decks to make the geometric compatibility with the new structures and the new layout and in the crowning of the wing walls in the widening strip, to allow the insertion of the new decks.  

The existing significant backfill increased by the reprofiling of the motorway, led to the need to  structural reinforcement  of some works:

- PI`s 421, 422 and 426 (Section IC24/Carvalhos) – These were ribbed frames with insufficient strength on the deck. The developed solution consisted of the application of  external prestressing , with cables installed on the side of the ribs, with derailleurs made up of metallic pieces fixed to the ribs and anchor blocks executed on the back of the uprights.

- PI 426 (Section IC24/Carvalhos) – This work had an insufficient resistance capacity in terms of the connection between the transom and the uprights, at the base of the uprights and in the foundations, which were made up of piles. The reinforcement solution passed through the application of  carbon fibers , installation of  prestressing bars  in the mullions, in holes with a depth of about 9.0 m, at the entire height of the mullions and also the execution of  concrete struts  between the faces of the foundation blocks.   

- PI`s 405 and 408 (FeiraIC24 Section) – Laminar frames with insufficient resistance capacity at the level of the transom and uprights. Reinforcement was carried out with  carbon fibers, slab thickening  of the transom in the connection to the new structures and execution of concrete struts between the faces of the foundation foundations in PI 405.

Client:  Brisa, Auto Estradas de Portugal, SA.

Section IC24/Carvalhos

Project: 1998

Entry into service: 2000

Excerpt Fair/IC24
Project: 2003
Entry into service: 2006