Hotel Sheraton Malpensa

Milan / Italy / 2010

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14 Love 8,283 Visits Published
Una facciata curva, realizzata con un materiale high-tech realizzato ad hoc, 14 metri d’altezza e 450 d’altezza distribuiti su tre livelli, 436 camere, caffetteria, ristoranti e Centro Conferenze da 2000 mq per un costo complessivo di 67 milioni di euro: sono queste le caratteristiche principali del costruendo hotel Sheraton di Malpensa, progettato dallo studio d’architettura romano King Roselli su commissione della Sea.

La data d’inaugurazione della struttura, quasi del tutto ultimata per una superficie totale di 55mila mq, è fissata a luglio 2011. Costata mille euro a metro quadro, la struttura alberghiera sorge su di un’area di 24.750 mq di superficie già edificata, ospitante l’autorimessa multipiano che sorge in posizione frontale all’aeroporto di Malpensa. Il primo piano è a quota +6,25 metri e ingloba una porzione dell’ultimo livello del parking.

Elemento distintivo dell’edificio sarà l’involucro esterno: “una grande pelle che si piega e che avvolge i corpi che contengono le camere. Tutte le installazioni sono nascoste sotto la sua copertura e respirano attraverso diverse aperture. Nell’insieme, la struttura ricorda più un oggetto di design che un edificio”, ha spiegato l'arch. Riccardo Roselli.

La struttura interna del volume è in acciaio, per la pelle esterna è stato impiegato un composito a base di vetroresina realizzato ad hoc dall’azienda milanese Pcr – Progettazione costruzione ricerca chiamato “pultruso”. La finitura al quarzo, idrorepellente, è rivestita con una pellicola di colore bianco-grigio.

Il nuovo materiale è stato preferito dal team di progetto rispetto ad altre soluzioni più diffuse nella realizzazione delle facciate come le membrane liquide a spruzzo e policarbonato: “Benché alcuni di questi materiali fossero adatti alla termoformatura, presentavano limiti per quanto riguarda la saldatura e non soddisfacevano tutti i requisiti prestazionali. Le membrane liquide a spruzzo, potevano coprire con un unica pellicola tutto l’edificio in modo uniforme, ma l’edificio era semplicemente troppo grande perché questa soluzione potesse funzionare”, ha spiegato Roselli.

L’involucro avvolge diversi edifici, situati in sequenza a intervalli irregolari, in modo da creare un fronte esterno allungato e ritmato. I volumi sono raccordati da basamento, copertura e scale di emergenza.

Architectural design of building volume, from initial concept phase (winner of competition held by SEA), planning permission, detailed design of exterior cladding systems and site supervision. Interiors of entrance and lobby spaces. On site from 2007 completion- October 2010.

We were commissioned to design the exteriors of this large hotel in front of Malpensa International Airport as a result of our competition winning entry for the overall design of the building. Despite its size (420m long, 64m wide, 21m high) the building was conceived as a design object. Partly because Milan is Italy's design capital, and partly because we were interested in investigating the technical and architectural properties of a skin or membrane to be perceived dynamically as façade not only on its four sides but also the roof- visible from the access road to the airport complex.

The hotel itself is set on an existing base consisting of a huge car park over the railway that passes underground. The hotel has 430 rooms, a conference centre, a spa accessible directly from the airport via an existing connecting bridge over the surrounding ring road. The car park is to be clad with a grille open for natural ventilation but opaque from the outside, to create a solid base.

The building is enclosed in a membrane to be realised in either titanium-zinc, Corian (more like a design object) and finally pultruded fibreglass which establishes its lower datum above the existing car park, wraps around the three storeys of the hotel, producing a series of curved facades, facing the airport, and inner cut-out courtyards and finishes parallel to the starting edge. The ends are left empty to emphasis the horizontality of the volume with shallow water pools connected along the front lower ledge of the facade.

All the plant extracts and ventilation “breath” through the vents cut into the top part (roof) of the membrane.

The layout of the rooms are organised around the courtyards which give a comb-like form to the plan and avoid a direct view from the airport into guest rooms.

On the open side these blocks of rooms articulate the façade in an irregular sequence of solid and void. The solids in turn are articulated by a series of thick sculptural PVC blackout curtains which give both depth and a dynamic to the overall elevation.

Technical Review by Donna Dawson Composites Technology Magazine (USA) August 2010

Design Overview•
Design goal : a continuous wrap-around façade for the new Sheraton Malpensa, having no visible joints or fasteners, and demonstrating thermal stability in temperatures varying by 70°C/126°F and in winter snow and ice conditions.

Result was a sequence of thin pultruded fiberglass sheets, called membranes, curved around a subframe of pultruded structural profiles and steel arches, wrapping the entire length of each bay, or module of the hotel in a smooth, continuous skin.

The Sheraton Milan Malpensa Airport Hotel & Conference Centre in northern Italy, scheduled for completed in October 2010, presents the visitor with a continuously smooth wrap-around façade originates from the idea of a large folding skin wrapping the modules containing the rooms and public areas forms two continuous edges the whole length of the building. The desired effect was a perfectly smooth surface with hardly perceptible joints, which could keep the weather out and was stable in temperature differences of 70°C/126°F, and that could be laid almost flat on the roof—which is visible from the airport access road—and then curve around the fold. Working drawings were prepared for versions in zinc-titanium, Corian and similar solid surfacing, sprayed polyurethane damp-proof membranes, and hydro-repellent concrete-resin based finishes. In the end, the final solution wrapped up the hotel’s offices, cafes and restaurants, 430 rooms and a 2,000 m2 / 21,528 ft2 conference center, with more than 53,000 linear meters/173,884 feet of pultruded fiberglass composite profiles designed and manufactured by Progettazione Costruzione Ricerca (Project Construction Research, or PCR) based in Bernareggio (Milan), Italy.

The main challenge was to design the composite parts in front of a continuous façade with no visible joints on such a large surface, and which accommodates bi-directional curves on top of the roof through the total 420m/1,378 ft length of the hotel, and, further, has a low coefficient of expansion for thermal stability in extreme temperatures and weather changes. The length of the hotel comprises seven bays separated by courtyards, with the curved facades facing the airport, and the rooms looking out on the courtyards. The front line of the hotel is left open to emphasis the horizontality of the volume with shallow water pools set into the lower level.

Allowed only three months for the design phase, PCR began with finite element analysis (FEA) of design loads, and finite element modeling (FEM), using CATIA V5 from Dassault Systems (Vélizy Villacoublay, France). Specified design loads were F = 15,000 N (kg m/s2)—281 lb-force feet/in.—distributed force and wind loads of 0.001 MPa/0.145 psi. Due to the relatively low weight of the pultruded structure, a specific structural analysis for earthquake loads was not required, separate from earthquake calculations for the main building structure to which the composite panels are attached.

Analysis and modeling led PCR to a design solution based primarily on a sequence of pultruded fiberglass membranes. In architecture, a membrane structure is defined as a structure with a thin, flexible surface (membrane) that carries loads primarily through tensile stresses. Tensile strength in a composite structure is provided by the unidirectional fibers, and since pultrusion is basically a unidirectional process, relying primarily on unidirectional (longitudinal) fibers to pull the part through the die, the pultruded membranes provide high tensile strength.

For fiber strength, PCR chose Advantex fiberglass reinforcements from 3B Fibreglass (Battice, Belgium), pultruding 9600 tex (9600 g/km linear density) direct roving for tensile strength with continuous strand mat for off-axis strength and impact resistance. Advantex—a registered trademark of Owens Corning produced by 3B under license—is a boron-free E-glass that also offers significant corrosion resistance, in accordance with ASTM D578 and ISO 2078 standards. 3B was formed in 2007 as a result of divestiture of Owens Corning’s fiberglass manufacturing businesses in Battice, Belgium, and Birkeland, Norway.

Additional corrosion resistance, water resistance and fire resistance are provided by an unidentified polyester resin system. Marenzi says the special polyester formula meets M1F0 fire ratings of the Association Francaise de Normalisation (La Plaine Saint-Denis Cedex, France), AFNOR Standard NF F 16 101/102. The pultruded profiles are also water resistant, but drainage posed a challenge because “the architectural design vetoed the use of over-lapping edges or any adhesive or silicon sealing,” Marenzi explains. The hotel is very close to the Alps, and adequate drainage is essential as winter snow and ice may remain for days or even weeks on the building before melting. PCR’s solution was to add a small profile on the back of the vertical panels, where they join, which allows collected water to drain off the building.

Six smooth miles
A total of six smooth miles of pultruded profiles wrap up the bays of the hotel. Pultruded membranes 1m x 22m / 3.28 x 72 ft were designed to extend under the bottom floor of each bay, curve upward around the 13.8 m/45.28 ft high emergency escape stairwells on the back of the bay, and then run out along the essentially flat roof toward the front of the hotel, forming a smooth, continuous skin, or façade. The curve is a minimum radius of 2.5m/8.25 ft from the first level to the top of the third level. Around this end curve, the membranes are supported by a subframe made of pultruded square sections and steel arches. These large membranes—6,500m/21,325 ft in all—join to 3,500m/11,483 ft of 1.4m x 6m / 4.6 x 19.7 ft pultruded panels for the fascias. The fascias join orthogonally to the large membranes on the roof, around the end curve and under the bottom floor.

Membranes and fascia are joined end-to-end and face-to-face without overlapping, adhesives, or visible joints or fasteners—a feat accomplished by means of the steel and composite subframe and the assistance of more than 43,000m/141,076 ft of various other pultruded profiles, notably hollow squares, corners, flats and grids plus the metal hardware needed to facilitate efficient construction.

All utilities and equipment, including ventilation, heat and air conditioning units, are hidden beneath the composite cover.

The next step was to validate the design through prototype manufacture and testing. “PCR is highly and vertically integrated, which lets prototypes flow easily from the CATIA CAD down to the shop floor for making temporary tooling, and which in turn enables rapid assembly of a first mock-up of the construction,” Marenzi points out. “This philosophy of keeping our focus in-house, from concept solution through design through production, allows us to quickly prove the design and obtain customer approval.”

Pultruding the profiles
To pultrude the membrane and fascias, PCR pulls the fiberglass roving and mat—and a non-woven surfacing veil for ultraviolet protection—through polyester resin and cures the wet bundle in a 120°C/248°F heated die. Pulling speed is 300mm/12 in. per minute for the largest profiles and up to 600mm/24 in. per minute for smaller shapes. After cure, the exterior membranes are sprayed with a quartz finish and a final white-grey surface finish by on-line integrated spray systems. No post-cure is required. PCR designs and builds its own special pultrusion machines, material guidance systems and die molds.

Molding the bi-directional curves
The same composite materials were used for manufacture of two separate molded parts to achieve the bi-directional curves for the roof vents. One molding is at each end of the roof vent, where the curved sections of the roof vent cover meet the membrane on the flat plane of the roof. The other is a section that joins the roof vent to the membrane on the curved façade.

Schedule
The installation and manufacture of the pultruded panels required a lot of fine tuning for this application in a building context.This was carried out during the detail drawing stage by Riccardo Roselli from the architectural point of view and by the technical office of PCR. With many 3D simulations in CATIA. In this way 90 percent of the problems had been resolved before going on site.

PCR warrants the pultruded panel structure for 10 years, plus durability of the panels for 30 years.

The advantages of this technology, until now rarely used in building, are due to its lightness and precision, enabling the manufacture of lengths up to 22m/72 ft of sheeting with almost invisible joints. Reduced costs and construction times coupled with the inherent qualities and finish of the material have proved to be decisive in achieving the desired result in this project.
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    Una facciata curva, realizzata con un materiale high-tech realizzato ad hoc, 14 metri d’altezza e 450 d’altezza distribuiti su tre livelli, 436 camere, caffetteria, ristoranti e Centro Conferenze da 2000 mq per un costo complessivo di 67 milioni di euro: sono queste le caratteristiche principali del costruendo hotel Sheraton di Malpensa, progettato dallo studio d’architettura romano King Roselli su commissione della Sea.La data d’inaugurazione della struttura, quasi del tutto ultimata per una...

    Project details
    • Year 2010
    • Client Sea
    • Status Current works
    • Type Hotel/Resorts
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