Henri-IV Highway

Repair two bridges on Autoroute Henri-IV while keeping traffic running, above an active CN rail line, on a site spread over two seasons and divided into phases.

The challenge was not any one temporary structure, but the sequence they formed. Fourteen separate mandates were carried out on this structure, from deck jacking to work decks above the tracks: each phase released one portion of the structure and constrained another, and every temporary work had to fit into the phasing without blocking the next one.

Deck jacking — Lifting structures at axes 1, 4 and 10, east and west, with the support benches and the reinforced concrete corbels carrying the jacking loads.

Verification of the lifting corbels — Non-linear finite element modelling of the reinforced concrete, alongside conventional calculation, for corbels cast against existing columns.

Monitoring of the lifts over time — Repeated position surveys after each lift, axis by axis, continued for months through to final lowering.

Work decks above the CN tracks — Three separate decks and suspended platforms between axes 7 and 10, designed to railway clearance envelopes.

Temporary retaining walls — Retaining walls at the abutments and between phases, in concrete blocks or soldier-pile-and-lagging depending on the sector.

Temporary bridge and stair towers — Design of the temporary bridge and of the stair towers serving the site, including the one at the St-Louis overpass.

Diaphragm analysis — Verification of the axis 4 diaphragm under the forces induced by jacking.

Certification and site supervision — Certificate of conformity for every temporary work before it was put into service: support benches, lifting structures, platforms, retaining walls, corbel reinforcement, stair towers.

Autoroute Henri-IV is the gateway to the Capitale-Nationale region. Working on it means accepting that nothing closes: not the highway above, not the rail line below.

This project ran for two years, and the mandate did not end when the load was transferred. Position surveys continued for months after each lift: this is the kind of project where the value shows up long after the drawing is issued.

Thanks to EBC.