BIM FOR THE NEW POLCEVERA VIADUCT
In the wake of the tragic collapse of the so-called Morandi bridge on 14 August 2018, Italferr has been assigned the executive design of the new Viaduct over the Polcevera river in Genoa, Italy.
The Società Consortile Pergenova consortium has nominated Italferr as Designer of the new infrastructure, based on the architectural design developed by the firm “Renzo Piano Building Workshop”.
The tight schedule for the development of the project, necessary in view of restoring Genoa’s traffic flow and therefore the city’s economic and social balance as quickly as possible, has established the need to address the task with special means, so as to ensure extraordinarily fast action and decision-making.
With a specific organizational order, a dedicated Task Force was put together that, coherently with the work plan approved by the Extraordinary Commissary for Reconstruction, has been charged with the task of developing the executive design in about three months.
The Polcevera Viaduct is a fundamental junction and transport element for the city of Genoa, for the Liguria region and for Italy as a whole, seeing that it is the final section of the A10 motorway limited, on the East side, by the interchange with the A7 (called ‘Genova Ovest’) and, on the West side, by the entrances to the tunnels that lead to the interchange called ‘Aeroporto’.
The Executive design envisages that the infrastructure will overlap the same attitude of the Morandi Bridge, with the necessary regulatory adaptations to the cross-section of the deck and of the radii of curvature of the exit and entry interchanges. The design principle is based on simplicity: the bridge will be discrete and sombre in appearance, thereby renouncing self-celebratory monumentality.
3D view - BIM of the New Polcevera Viaduct
Based on the architectural design developed by the Renzo Piano firm, the bridge will comprise reinforced concrete piers with an elliptical cross-section positioned at constant 50 m intervals, except for three spans – the ones actually crossing over the Polcevera river – and the two adjacent ones, for which the C/C distance rises to 100 m. The main deck will consist of a continuous main beam 1,067.17 m overall consisting of a total of 19 bays.
Longitudinal view - BIM of the New Polcevera Viaduct
To this deck is structurally connected a steel/concrete 3-span slab 109.91 m long overall. The piers are to be made of reinforced concrete, with constant cross-section for their full height.
The viaduct will feature considerable technological contents in order to enhance the work’s architectural style and its environmental sustainability in terms of energy consumption, and will be made so as to ensure very high levels of road traffic safety and maximum durability of the structures and systems.
Technological content of the New Polcevera Viaduct at the slab insert point
BIM (BUILD INFORMATION MODELING)
In the executive design phase, Italferr implemented the BIM (Building Information Modeling) model of the viaduct so as to guarantee very high design standards based on the following principles.
DESCRIPTION OF THE SOLUTIONS
Before proceeding with the modelling activities and its components, an Information Management Plan (pGI in Italian) was prepared in order to establish from the start the operational methods and contents of the BIM information model for the Polcevera Viaduct.
Subsequently, in order to boost data and information exchange between the various parties involved, a common data environment was prepared in which a structure of worksheets was organized, so that each discipline could have its own work space.
The structuring of the common data environment for the BIM model of the new Polcevera Viaduct was organised to foresee the assembly of many models coming from the various specialised divisions.
For each component of the BIM model, upstream from the modelling process, a minimal set of information was set, including:
WBS identification code
Main dimensions (Length, Surface area, Volume, etc.)
Starting from the modelling of the individual components, an information model was generated that would allow to assemble everything with extreme precision and dynamism. Keeping these aspects in sight, it was decided to use in an innovative manner, compared to the usual standards, computational modelling systems that could guarantee versatility and speed in re-aligning the model with any design changes.
Using computational modelling based on code blocks, it was possible to develop scripts aimed at optimising and automating the manual processes that would traditionally take a long time to be completed. After defining the library of components, using these scripts a model assembly phase was launched, allowing for the dynamic management of its parametric content. The scripts are connected to a calculation sheet that contains all of the basic information required to define the model. By acting precisely on each single cell, it was possible to automatically update the model without it being necessary to act manually on the modelling.
In this design phase, the fact of having the information model at one’s disposal allowed us, at operational level, to carry out a whole set of dimensional and geometry checks so as to guarantee the correct positioning of the elements in space, also in function of the transfer of information to those who will then have to put in place the complex structure of the viaduct. To this end, the clash detection activity and the parameter checks conducted on the model during the various phases of updating the individual components, gave the structure an added value in terms of coherence and of constructability.
Another use made of the BIM concerns the 4D dimension by which the work plan was associated to the digital model. It was thus possible to simulate the work construction phases and identify beforehand the especially critical work processes and situations.
3D detail - BIM of the New Polcevera Viaduct for Maintenance
The achievement of this goal will allow to put in place an infrastructure whose BIM model is the linking element between a first time-limited phase of design and definition of the structure, and the certainly more important phase of operation and management of the structure.