the strengthening of the Ferpècle bridge (Les Haudères, Switzerland) with an innovative intervention involving Ultra-high-performance Fiber-Reinforced Cementitious Composite (UHPFRC), which was realized in 2023. The structure, built in 1958, is one of the first prestressed concrete bridges in the country, with a single span of 35 meters. The original intervention involves clamping the supports to transform the static scheme and widening the bridge from 5.3 to 7.9 meters with UHPFRC to accommodate new traffic demands. The bending and shear capacities were increased by 47 and 49 %, respectively. 

UHPFRC is used to clamp the boundary condition and thus transform the static scheme of the bridge. The widening is also made of UHPFRC to reduce the additional self-weight. The intervention is regenerative as it aims to both increase the load-bearing capacity, rehabilitate the existing-structure durability and minimize future maintenance by removing joints.

The UHPFRC intervention allows for the strengthening and widening of the bridge while intervening only on the top of the deck. Prestressed girders are thus not modified, which significantly facilitates the construction works, accelerates the works and reduces costs. Moreover, it allows an intervention in two phases (upstream and downstream), maintaining the bridge open for one road lane during the entire construction with alternating traffic.

The life-cycle analyses shows a reduction of envionmental impacts by 55 % and costs by 42 %. 

Existing structure examination

Intervention conceptual design

Intervention design with numerical simulations

Monitoring campaign and data interpretation

Life-cycle cost and environmental analyses

The new Chaumény footbridge is a new flyover the railway line in Montreux, Switzerland. The elegant structure is a 22.5-meter-span trough girder, resting on one abutment and a pier with a 9-meter cantilever staircase.

The structure is made of several precast elements that were assembled by post-tensioning. In this way, a monolithic structure (without mechanical bearings) was obtained, rigid enough to avoid any vibration or deflection issues despite the relatively low weight of the footbridge. 

By choosing post-tensioned UHPFRC as the main structural material, the footbridge design has a unique aesthetic, especially due to the spectacular cantilever staircase of 9 meters. This project expands the current boundaries of design possibilities of UHPFC structures.

Numerical analysis of the pile 

Verification of the bridge design

Verification of bridge installation

The Aiguillon Bridge is the second railway bridge worldwide made of UHPFRC. A key requirement from bridge owners is that the replacement should be made as quickly as possible to minimize the disturbance on the traffic. Additionally, the bridge has difficult access, and the depth of the bridge was constrained due to the road below.

Due to these constraints, a bridge structure entirely in UHPFRC has been designed. This design was cheaper than a steel bridge and easier to install than a concrete structure as elements are thinner. The structure is made using two slender precast elements, and a keying joint is cast next to the bridge location. The design of the keying joint is of particular interest. 

A full-scale laboratory experiment has been made at EPFL. The behavior of the joint has been monitored using state-of-the-art sensing technologies. The experiment has validated the unique structural design. This project shows the importance of the collaboration between industrial partners and academia to propose original designs.

Design of the keying joint

Verification of element preparation and bridge installation

Laboratory experiment

This pharmaceutical building spreads over three floors of 3300 m2 built in the 1970’s. As the company wanted to increase the living loads from 5 to 9 kN/m2, the existing structure was structurally insufficient. In particular, the concrete columns below the last floor presented a risk of punching-shear failure.

This project is one of the first applications worldwide of UHPFRC for punching-shear strengthening. The intervention involves casting a new layer of 60 mm of UHFRC reinforced with steel rebars. Thanks to the mechanical property of the material, the UHPFRC layer simultaneously strengthens the punching-shear and bending resistances of the existing structure with a minimal space height loss.

With this intervention, the inclusion of punching-shear heads in the existing slab was avoided, significantly reducing the construction time and project costs. This project shows the potential that offering new materials for the minimal-impact rehabilitation of existing structures. These new technologies help design low-impact interventions.

Contribution: Design of the intervention