Ultra-High Performance Fibre-Reinforced Concrete (UHPFRC) was selected as the defining material for the Museum of European & Mediterranean Civilisations (Mucem)– the first national museum to be built in France outside of Paris. Durability was a key design issue given the building’s location on the seafront of Marseille; this and the aesthetic benefits of the material being the main reasons for its selection.

Cover picture MuCEM-Copyright Ian Han

  • Name of the owner
    Opérateur du Patrimoine et des Projets Immobiliers de la Culture (OPPIC)
  • Name of the client
    French Communication and Culture Ministry
  • Delivery date of the project
    2013
  • Partners of the project
    Architect: Rudy Ricciotti Structural
    Main contractor: Dumez-Freyssinet JV
    Engineer: SICA SA
    Building services engineer: Garcia Ingenierie
    UHPFRC prefabrication: Bonna Sabla
Key figures

Tree-shaped concrete columns

While the museum itself is a simple 50 m-square form on plan, the columns which support the facade were conceived by architect Rudy Ricciotti as a forest of tree-shaped elements precast in UHPFRC and prestressed across their full height.

UHPFRC was also specified for two footbridges linking to the building; at the time incorporating the longest span built in this novel material.

  • 450
    Volume of ultra-high performance fibre-reinforced concrete (m3)
  • 309
    Number of precast UHPFRC columns
  • 76.5
    Length of UHPFRC footbridge main span (m)

Innovative isolation system for the MUCEM UHPFRC columns

The desire to make extensive use of UHPFRC, particularly in the columns, prompted an assessment by the French technical agency “Centre Scientifique et Technique du Bâtiment” in relation to seismic loading, and fire resistance specifications. No structural codes for UHPFRC existed at the time.

This assessment led to ball joints being added at the top and bottom of the columns to isolate them from seismic and wind loading; analysis of the response to fire was identified as the defining criteria for the design of prestressing for the columns.

The dual demands placed on the tree-like building columns required innovative solutions from Freyssinet experts – not only in terms of how to manage the sometimes-conflicting design criteria, but also in forming and assembling these elements.

 

Isolation system
UHPFRC columns assembly challenge

UHPFRC columns assembly challenge

The traditional procedure of building columns to support girders for each floor level was simply not possible at Mucem. Each of the ‘tree’ structures in the forest of UHPFRC columns is formed of three precast units stacked one on top of the other – and the branching form of the design means that adjacent columns are also interconnected.

The introduction of ball joints at the top and bottom of each column, to isolate them from seismic events, exacerbated the assembly challenge. No load transfer could be carried out until every column had been installed to its full height of up to 21 m or three floors of the building.

An unprecedented level of precision for the MUCEM

Hence the floor girders of the building were first erected on temporary props, and the ring beam cast to provide a structure to support the precast column units during assembly. This required an unprecedented level of precision in the construction of the main beams.

Prestressing tendons run the full height of each column, and must connect each branch, creating a complex network of ducts and cables. The substantial joints that connect the columns to the floor beams were subsequently enclosed in precast UHPFRC shells

MUCEM- Un unprecedent level of precision
MUCEM- World record for a high-strength footbridge

World record for a high-strength footbridge

Freyssinet’s scope of work also covered design and construction of two slender footbridges built in UHPFRC, linking the new museum to Fort Saint-Jean and beyond to the church of Saint Laurent with lengths of 112 m and 69 m respectively. Segments were precast using moulds from a previous project, and assembled on site.

The Fort Saint-Jean footbridge has a main span of 76.5 m, which at the time was the longest to be built in this material; this was one of the first elements constructed, and had to be erected on temporary supports while a permanent water feature was excavated below.

 

A phased assembly

Once again Freyssinet had to turn traditional procedure on its head to facilitate construction of a multi-span structure which had very slender flanges,making it impossible to deviate tendons over the supports.

Phased assembly was the answer, with the main isostatic span tensioned first; the shorter side spans were then put into continuity by tensioning tendons across the full bridge length.

Footbridge phased assembly

I appreciated Freyssinet’s contribution. They integrated the innovative techniques necessary for calculation, prefabrication, and assembly of the UHPFRC columns and footbridges within millimeter-accuracy.

Jacques Portelatine -  
Former project manager

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