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Santa Maria Misericordia Hospital Laboratory: ArcelorMittal SFB beams optimise an anti-seismic structure
The service centre and laboratories of Santa Maria Misericordia Hospital in Udine, Italy is an example for the use of innovative steel and concrete composite construction in a seismic area. ArcelorMittal's slim floor solution, SFB beams, was used to support the floor slabs. This solution ensured that the floor height could be maximised and no intermediary columns were necessary.
The laboratory building & its structural design
The building houses laboratories for research activities of different kinds: pathological diagnosis, clinical analysis, and areas for specialised and pharmaceutical industries.
Rectangular in plan, measuring 64 x 74 m, the building consists of four levels and a technical floor on the top. The compact volume, a parallelepiped, has two interior courtyards placed in a central position. Along the perimeter, a continuous portico contains a metal grill walkway dedicated to maintenance service. The outer cladding consists of two layers: an interior blind wall clad with enamelled glass and strip windows and an exterior layer made of expanded metal, to provide shade, dimensioned and positioned to ensure optimum solar radiation in all seasons.
The four staircases are located along the short side of the building whereas the lifts, the landscaped courtyards, and the toilet installations are arranged symmetrically in the building's centre.
The main structure consists of a central core made of reinforced concrete, working as a seismic bracing system, and framing structure of steel-concrete composite elements for the vertical loads. The floors are made of self-supporting, hollow core concrete slabs, finished on site. The beams are continuous along the pillars and their junctions are made where there are no stress forces.
During the construction phase, the weight of the floors was only supported by the metal frame.
After hardening of the concrete, the beams show the typical behaviour of a composite structure.
Slim floor beams by ArcelorMittal
The constructive solution used for the flooring system is called slim floor and it is promoted by ArcelorMittal Commercial Long in Turin, Italy, who also provided technical assistance in the design phase.
The key of the slim floor solution is the asymmetric SFB beam that consists of an H section with a lower flange that is wider than its upper flange. This is achieved by welding a plate under the lower flange which allows to support for the concrete slab. Stud connectors were welded to the beams' webs to ensure perfect connection of the steel structure and the concrete poured on site. The beams were prepared and finished for connection with the columns.
The vertical structural elements are made of composite HPR columns, composed of H sections partially encased in concrete poured on site. This coating increases the columns' normal stress resistance and protects them against fire.
The profiles are fitted with bolts welded onto their webs, which have the dual purpose of counteracting the sliding between the two materials and preventing the buckling of the plates with reinforced concrete coated webs. The columns were prepared for the nodal connections with the beams. In the execution phase, the company (Rizzani de Eccher) particularly appreciated the reduction of construction time which was estimated around 25 % compared to the realisation of traditional concrete structures.
As construction came to an end, the reduction of structural limitations for both horizontal and vertical structural elements became obvious and turned into a distinctive feature of the building.
Thanks to the use of composite steel and concrete solutions such as slim floor, it was not necessary to install additional supporting floor beams thereby facilitating the passage of the technical installations and maximising the floor height.
Similarly, the use of composite columns made of S355M grade steel resulted in an overall reduction of the columns' sizes (from 0.8% to 0.25% of the total surface) which means that around 25 square metres of additional space could be gained.
The technical solution adopted allowed for savings of material for fire protection, taking into account that the composite solution for this project reaches an intrinsic fire resistance up to R90.
L+ Partners, Milano
- Engineering office:
Studio d’ingegneria Suraci, Udine – ing. Giuseppe Suraci
ATON per il progetto S.r.l.
Siram S.p.A., Rizzani de Eccher S.p.A.,
CPL Concordia Soc. Coop., AR.CO. Lavori S.C.C.
Ing. Giuseppe Suraci "Prefabbricazione strutturale negli edifici civili" (shortened & adapted)