C&E Ingénierie

Using Advance Design, read how C&E Ingénierie provided its expertise to ensure the safety and reliability of several structures for the opening ceremony of the Paris 2024 Olympic Games.

Company: C&E Ingénierie
Software used: Advance Design
Location: Paris, France

A team of passionate and dedicated experts

The C&E Ingénierie team, composed of Jeanne Le Jossec, Lucie Hascoet, Sarah Robinet, Vincent Barazutti, Andrea Llorens Garcia, and Yanni Zhao, working under the direction of Jean-Marc Weill (CEO of C&E Ingénierie), contributed their expertise to ensure the safety and reliability of several iconic structures in Paris during the opening ceremony of the Olympic Games.

Jeanne Le Jossec, an engineer and architect specializing in geo- and bio-based materials, worked intensively on the Tournelle and Change bridges, where she assessed their capacity to support spectator stands. “Participating in a project of this scale, where technical precision and innovation are essential, has been an enriching and stimulating experience for me,” says Jeanne.

Lucie Hascoet, project director, collaborated with Jeanne on reinforced concrete calculations, particularly for the Tournelle Bridge. “This project required a strict methodology and strong collaboration between the technical teams. The complexity of the calculations and verifications demanded total commitment,” explains Lucie.

Sarah Robinet, architect and engineer, worked on the Pont des Arts and the Debilly footbridge, focusing on the dynamic analysis of these metal-framed structures, which served as performance venues during the opening ceremony. “For such an ambitious project, every detail matters. Advance Design was a valuable ally in understanding and simulating the overall behavior of these structures, which was essential to ensure their stability during the artistic performances,” adds Sarah.

A dive into the archives to understand the design secrets of historic bridges

To carry out their studies successfully, the team had to travel back in time and consult valuable archival documents.

Jeanne explains: “Before starting the modelling and calculations, we conducted an investigative study at the Archives of the City of Paris. This allowed us to find calculation notes and original plans dating back to the time of the bridges’ construction. These historical documents, such as those concerning the Pont de la Tournelle built in 1906, revealed calculation methods different from those used today.”

The plans and period photographs allowed the engineers to better understand the structural functioning of the bridges and identify the methods used at the time to size the structures.

“For the Pont de la Tournelle, for example, we discovered that it consisted of reinforced concrete arches with a hollow rectangular section, which were simplified to I-sections in the calculations of the time. This type of information is invaluable for modelling the structures as accurately as possible with modern methods,” adds Jeanne.

This archival work enabled the team to faithfully recreate the original structural behaviours, relying on the modelling techniques of Advance Design. “We used fictitious sections in Advance Design, integrating the correct inertia and area, which allowed us to model the behaviour of the arch of the Pont de la Tournelle as accurately as possible in our analyses,” explains Lucie.

The Data Transmission by Paname 24: An Essential Flow of Information

To ensure precise analysis, the team relied on data transmitted by Paname 24, the event’s organising body. This information included schematic plans and specific artistic directives, derived from the vision of Thomas Jolly, the artistic director of Paris 2024, and served as the foundation for defining the calculation assumptions.

Jeanne recalls: “The schematic plans and the data provided allowed us to adjust our assumptions and verify the feasibility of each proposed stage installation. This partnership was essential for refining our studies as the artistic adjustments were made.”

Complex modeling made easy by Advance Design

To carry out detailed analyses and anticipate the behaviour of the structures, the team used the GRAITEC Advance Design software, which proved crucial for modelling dynamic loads.

Sarah explains: “With Advance Design, we were able to simulate the effect of dynamic loads induced by the choreographies, particularly on the Debilly footbridge, which is a wrought iron structure dating back to the early 20th century. The software allowed us to replicate the geometric properties of the historic sections and test the different load scenarios corresponding to the artistic wishes of Paname 24.”

This flexibility allowed the models to be adjusted based on the information obtained and real-world conditions. “We were able to faithfully recreate the structures, with a level of precision that allowed us to anticipate potential risks related to resonance effects,” adds Jeanne. “Advance Design not only saved time but, when combined with on-site testing, also provided reliable results to make decisions based on accurate data.”

Simulation of the show and behavioural impact on the structure

The analyses carried out in Advance Design highlighted potential risks related to the choreographies planned for the Debilly footbridge.

Sarah Robinet explains: “Initially, we had the input data that there would be 250 dancers positioned on the central span, under the main arch. The team at Paname 24 also wanted them to dance in synchrony. The choreographer of the show provided, from the outset of our work, the rhythm at which the dancers would dance and jump. By using the temporal dynamic load modelling features of Advance Design, we were able to simulate the dynamic actions exerted by the dancers in a precise and faithful manner to what was desired.”

However, initially, we calculated, using the software, the frequencies of the footbridge to identify the sensitive modes of the structure. This preliminary study allowed us to conclude that there were sufficiently low frequencies in the footbridge that could coincide with the rhythm of the dancers, potentially risking a resonance effect on the structure.

“Thus, in a second step, we decided to push the analysis further by precisely modelling the dynamic loads corresponding to the dancers. This second study allowed us to conclude that there was indeed too great a risk of resonance between the dancers and the catwalk. These analytical results, coupled with the in-situ tests, allowed the organizers of the show to reorient the planned painting on Debilly.”

Dynamic testing and adjustments for a safe ceremony

The analytical results from Advance Design underlined the importance of additional tests in real conditions.

The real tests played a key role in validating the numerical simulations and adjusting the artistic choices, taking into account the structural constraints. “The dynamic test carried out on the Debilly footbridge involving 50 dancers revealed significant oscillations, confirming that the structure reacted in accordance with our calculations, with vibrations sensitive to the frequency of the dancers’ movements,” explains Sarah.

Jeanne adds: “These in-situ tests allowed us to visualize on the structure of the footbridge the oscillation modes given by the dynamic modelling on Advance Design. We found the same behaviour under the solicitations induced by the dancers.”

Lucie emphasises the importance of this step: “It was essential to confirm our hypotheses. Our results helped the art teams to better understand the technical constraints and adapt their paintings accordingly.”

Faced with these results, the organisers first decided to reduce the number of dancers to 100 people. However, the continuation of C&E Ingénierie studies showed that the subjects of resonance persisted with 100 dancers. The artistic direction of the ceremony finally chose to move this dance tableau initially planned to a floating platform and to develop a more static tableau on the Debilly footbridge. This adaptation ensured safety while preserving the excellence of the show.

Constant support from GRAITEC experts

Through this project, the engineers of C&E Ingénierie have benefited from the continuous assistance of GRAITEC experts to optimise the use of Advance Design. “The regular exchanges with the GRAITEC experts have been very useful, especially for complex technical questions. The software is constantly evolving and each update brings improvements that better meet our needs,” comments Lucie.

A successful global event thanks to a cutting-edge team and software

On the day of the opening ceremony, the C&E Ingénierie team was able to admire the result of their work, in complete peace. Jeanne says: “I was present on the banks of the Seine and I felt immense pride in seeing that our recommendations had been taken into account. Seeing the artistic performances live and knowing that our calculations had contributed to the safety of the event was extremely gratifying. For the stands installed on the bridges, the decision to distribute them on the piers made it possible to guarantee optimal stability and maintain a high level of safety.”

For C&E Ingénierie, this project highlighted not only their expertise but also Advance Design’s capabilities in extreme conditions. “This software was a real asset for conducting our analyses and communicating transparently with our partners. Thanks to the visuals and 3D animations, we were able to exchange more easily with the Paname 24 teams on the dynamic behaviour of the footbridge and the associated risks,” concludes Jeanne. This testimonial illustrates how technological innovation and human expertise combined to ensure the success of an international event.

The C&E Ingénierie team is proud to have contributed to a historic moment, ensuring that every structure, every bridge, and every walkway meets the highest safety standards, while meeting the unique artistic requirements of the Olympic Games.

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