Business resort Paris Pleyel: metal structures made by SMB and waterproofing by Soprema Entreprises

The hotel component (4*) of this ambitious complex, designed by architect Sretchko Markovic (163 Ateliers), will be delivered in the spring of 2024, at the dawn of the Paris Olympic Games. It includes the major restructuring and conversion of the emblematic Pleyel business tower, which will house nearly 700 rooms, operated by the German brand H-Hotels, catering areas, a bar and a panoramic swimming pool on the 40th floor at more 130 m high. Two new tertiary buildings, each over 18.000 m2, are under construction at the same time. The first of 6 floors, called "Music-Hall", is located at the foot of the historic tower. The second, “Maestro”, is a new 25-storey tower. The conference center, common base for these two new buildings, will offer a multifunctional and modular reception area of ​​8.000 m2, capable of accommodating up to 2.500 people.

For this major urban metamorphosis, SMB, a soon-to-be-hundred-year-old Breton company, is undertaking all the metal framework work:

• On the Pleyel tower, 3 additional levels, including the one dedicated to the swimming pool, have been added to reach 41 floors in total. Between 6 and 9 workers erected the 250-tonne metal cap between July and December 2022. The access conditions and the vertiginous height of this heavy rehabilitation were integrated from the study phase by reducing the weight and length of the structural elements. . This new stylized structure allows the installation of the glass walls of the rooftop offering a breathtaking view of Paris.
• The supporting structure of the 25-storey Maestro tower has been rising from the ground since November 2022 and should be completed in 2024. It is the only 100% metal* high-rise building currently under construction in France. This exoskeleton with original architecture reaches a total weight of nearly 5.000 tonnes. The metal boxes forming the diagonals, 18 to 20 m long**, are linked together by X-shaped or K-shaped knots. Each of these knots represents a technical feat requiring up to 1.500 hours of manufacture and nearly 600 kg of filler metal per part for the most complex. The complex geometry of the structure imposed manufacturing and installation tolerances close to one millimetre. The frame has a white finish echoing the new aluminum envelope of the tower.

The SOPREMA Entreprises agency in Paris was chosen for the waterproofing package for the entire program. It has been taking place since the beginning of the year and the end of the work is scheduled for the first quarter of 2024. In the historic tower, 4 professionals have implemented 1.400 m2 of waterproofing in PVC membranes (FLAG from SOPREMA) for the sprinkler basins in the 1st, 2nd and 4th basements which protect the building in the event of fire. The technical rooms were sealed with resin (ALSAN® 500 from SOPREMA) on levels 1 and 2 of the basement and on the 25th floor, for a total area of ​​around 1.800 m2. The flat roofs are treated with bituminous waterproofing. Those inaccessible to the two high-rise towers will be covered with protection by slabs on studs to respond to the problem of the wind, i.e. a total surface area of ​​1.600 m2. That of Music-Hall, the new U-shaped building at the foot of the tower, will be protected by gravel over 3.000 m2. On this building, the inaccessible terraces of the double glass skin of the facade will be sealed with resin and covered with gratings.

* Only a concrete core for the elevators.

** Section of 800 x 800 mm, reconstituted and welded in S355 or S460 sheets up to 150 mm thick.

Complex study for the steel exoskeleton

The SMB design office produced advanced calculation models to define the behavior of the building, including its metal part. The mechanical verifications of the sections and the stability of the building locally and globally required integrating all the external parameters influencing the structure: foundations, stiffness of the base, rigidity of the core, overall settlement and temperature gradients.

Several issues made the exercise more complex:

• the differential deformations of the structure under the effect of the temperature between the steel of the exoskeleton and the concrete of the core,
• the phenomenon of opening of the structural model generated by the discontinuities of the path of efforts at the core,
• the deformations caused by the structural differences between the levels,
• the structural work base structure which could not absorb the forces brought by the exoskeleton and bring sufficient stiffness to the overall stability of the tower.

All the skills and expertise of the SMB design office were put to use on this project. The calculations and drawings will have mobilized nearly 5 calculators and 7 designers between the end of 2021 and this summer of 2023.

Accessibility of the complex site

The complexity for SMB lay in the way of designing and manufacturing the elements of the structure which could not be mounted to the top floors by an external crane, the main tower being 130 meters high. The team had to evolve with reduced means. In particular, it used a spider crane and lifts to hoist and then fix the metal posts and diagonals (HEA 500) which were not to exceed a length of 3,5 m and a weight of 10 tons, whereas they usually measure between 6 and 12m in length.

Fabrice BEASSE, Business Manager at SMB: “The elements had a weight of 250 kg/m linear. They were assembled over 130m high using large M30 bolts. At this height, we completely lose the usual landmarks! »

For SOPREMA Entreprises, the materials were taken by lift to the 40th floor of the Pleyel tower. They were then hoisted to the top floors using a small crane. When installing waterproofing on the roof terraces, the SOPREMA Entreprises team had to take the wind into account.

The many construction sites in progress in the surrounding area, linked to the profound transformation of the district and in particular to the future holding of the Olympic Games, also impose additional constraints in terms of storage. All deliveries pass through a logistics base located in Gennevilliers (92). SMB, like SOPREMA Entreprises, works just in time. Deliveries are scheduled to the nearest hour depending on the availability of the only crane serving the Pleyel tower.

Project actors

• Developer/Investor - Project management: Pleyel Investissement (subsidiary of the life insurance company, based in Strasbourg: AFI.ESCA - Burrus Group) - owner of the whole
• AMO: Financière des Quatre Rives, represented by Boris LITTY, Managing Director - Founder - Liberg Group
• MOE: Pangea Design and Engineering
• Architect: Sretchko Markovic (163 Workshops)
• Operator of the hotel and the conference center: H-Hotels (1st establishment of the German brand in France)
• Interior designer of the hotel: Agence Axel Schoenert architectes
• Waterproofing and steel structures packages: SOPREMA Entreprises and its steel structure subsidiary SMB