The seaside walk between Praia Formosa and Ribeira dos Socorridos, in Funchal, was originally built in 2005/2006 to provide a recreational pedestrian route, offering local residents and the many tourists who visit daily stunning views of the Madeira coastline.

The structure of the promenade runs beneath cliffs, along the beach, and by the sea, consisting of isostatic slab decks with prestressed longitudinal beams supported on cantilevers atop pillars, arranged along both straight and curved paths. The route includes four framed sections, interspersed with resting platforms supported by reinforced concrete walls, with stairways providing access between the pathway and the beach.

Intervention goal

The first structural inspection was carried out by the Regional Civil Engineering Laboratory (LREC) in 2021, when the structure was just over 15 years old. Two further inspections followed in 2022 and 2024, revealing a rapid progression in the deterioration of the structure’s condition, which was classified as alarming.

The degradation was primarily attributed to high concentrations of chlorides, resulting from the aggressive marine environment, given the proximity to the sea and the low elevation of the decks, exposing them to alternating wet/dry cycles and the splash zone from tidal and wave action. Additionally, there is a possibility that some of the construction materials originally used were sourced from the sea, contributing to the chloride presence within the concrete.

Certain sections of the promenade are subject to significant hydrodynamic forces, evidenced by severe abrasion on some plinths and footings, with uncertainty regarding whether these loads were properly accounted for in the original structural design.

Intervention stages and techniques

The rehabilitation of the promenade was carried out in phases, prioritizing the sections deemed most urgent by the LREC. The key interventions included:

1. Excavation to fully expose the height of pillars and footings;
2. Repair of footings through reinforcement replacement and micro-concrete casting;
3. Strengthening of the shafts and pillars with new reinforcement, and interior/exterior encasement using dry-mix shotcrete applied with low-output, double-chamber equipment;
4. Injection of pillars with compensated-shrinkage cement grout to consolidate the entire section;
5. Strengthening of slab and beam sections with new reinforcement, covered internally and externally with dry-mix shotcrete;
6. Construction of new prestressed cantilevers to transfer deck loads to new support bearings;
7. Application of a waterproof cementitious coating across the entire structure;
8. Protection against carbonation and chloride penetration on tidal-exposed surfaces using epoxy-based paint;
9. Protection of non-tidal-exposed surfaces with acrylic paint against carbonation and chloride ingress;
10. Installation of new anti-lifting devices on the deck trays.

Results

The rehabilitated sections of the promenade now comply with the structural safety assumptions of the original design, with the added benefit of improved protection against the harsh marine environment to which the structure is exposed.

Additional information

All rehabilitation works were carried out within the tidal zone and during the winter period. The often adverse sea conditions led to multiple work stoppages and repetitions, particularly in the excavation of pillars and footings, as wave action continually displaced materials – both light and heavy – back onto the beach and against the structure.