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IKEA Commercial Centre, Cyprus: A visible steel structure with long span ACB® beams
Completed in 2007, the new IKEA store in Nicosioa was realised according to the concept that characterises the IKEA buildings all over the world. ArcelorMittal ACB® cellular beams were used as a light and transparent solution for long span structures. Applying the Natural Fire Safety Concept approach, the nature of a fire in the store could be calculated and the architectonic concept could be mantained: the absence of passive fire protection permits a fully visible steel structure.
The structural solution
From an architectonic point of view, the building is composed of three parts: the store (two blocks placed side by side) with an underground car park, an additional underground car park completely detached from the main structure, and a building for offices and service installations. The structures of these three parts are physically separated by joints.
From a structural point of view, the buildings must resist seismic actions. For this reason they present three-dimensional steel-concrete frames integrated with horizontal and vertical braces respectively arranged on the roof and the facades. Concrete columns and walls support the ground floor with multidirectional curved neoprene supports, discs in PTFE, and stainless steel disposed on the perimeter while the supports are fixed in the central area.
The two upper levels have a steel-concrete structure, with steel columns and beams and floors made of steel decking profiles and concrete fill. The main and secondary beams are continuous, respectively with 8 and 16 m spans. The slab made with decking profiles presents a 4 m span between the secondary beams.
The roof is a structure composed of continuous IPE 750x137 beams with 16 m span and a secondary structure built with ArcelorMittal ACB® cellular beams characterised by a double slope with a central span of 8 m. They are continuous on 24 and 16 m spans.
ACB® beams: Light, resistant, & cost-efficient
The cellular beams were realised according to the ArcelorMittal patent technique starting from hot rolled profiles with an H section (HE650AA) oxy-cut and then welded in precise points, in order to obtain beams with a final height of one and a half of the initial one (999 mm) and large circular holes.
The choice to use ArcelorMittal's ACB© beams for the roof was influenced by the economic convenience offered by this light and resistant system: its ability to cover largespans. The ACB© solution has demonstrated in fact to be the most effective compared to other solutions such as structures made with normal profiles of 900 m section height (HE900AA). Although the cellular beams reflected an increased cost due to the transformation made in the workshop, the profit in terms of weight - and therefore material savings - considering the same span and loads placed on the beam is huge (123.3 kg/ml for the cellular beams against 198 kg/ml of HE900AA profiles). The roof consists of decking profiles (205 mm).
An installation platform with U cross section and reticular beams, measuring 24 m x16 m, was developed on top of the roof. The reticular beams are made by two trunks welded directly in the workshop and assembled to the structure on site by bolts.
The structure joints have been designed so as to assure the continuity of the main and secondary beams in correspondence with the columns and the secondary beams. Additionally, a metallic reinforcement was inserted into in the structural slab in these areas.
The metallic structure was constructed within 8 months (from July 2006 to March 2007) while the entire construction was completed in June 2007.
Fire safety considerations: Natural Fire Safety Concept
The steel and concrete structure, two and partly three storeys high, is one of the most common in shopping centres: It is particularly efficient from a structural point of view, but it is also aesthetically interesting as it is completely visible. It is necessary to ensure that such a structure is safe in case of fire in order to allow evacuation and guarantee the adequate safety for fire rescue workers. In these cases, it is necessary therefore to verify, and to certify, the resistance of the structure joints.
In this particular case study, the evolution of the temperature produced from a natural fire had been studied carefully. The result stated that the the amount and type of combustible material, the ventilation conditions, and the geometric characteristics of the compartment, the insulation properties of the materials, and the dimensions of the openings have a possible influence in the fire scenario.
The analysis carried out allowed for the verification of two scenes: the first one in which a fire spread in a local sale environment bounded by walls with openings, and one in which an uncontrolled general fire covering the entire surface developed. The study had thus calculated the changes of temperatures and materials in order to determine the characteristics of resistance.
Therefore, it was possible to verify that the structural solutions adopted in this IKEA building fulfilled the requirements of the fire safety norms, responding appropriately to incidents involving fire even at the structural level.
22 000 m2
Steel frame: 4 720 000 Euro
Total: 23 000 000 Euro
Maratheftis Yiannouris - Architects Engineers
Project Architect: Pavlina Kalatha - Cyprus
- Engineering firms:
Redesco Srl - Gian Carlo Giuliani Engineer - Italy (concept and executive design)
Konstantinos Yiannouris, Eng.
Elioforou & Zinieris Meltec (electromechanical engineering)
General Contractor: Iordanou Loizos Ikodomikes Epichirisis
Contractor: Vert & Blanc - Cyprus
Steel Fabricator: C+P Industriebau GmbH & Co. KG-Germania