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| PERI: self-levelling slab tables without intermediate props  A customised, innovative PERI slab table system is ensuring very fast shuttering times and reduced material requirements at the Canadian South Health Campus medical centre near Calgary. For building contractor, Ellis Don, the formwork and scaffolding specialist PERI developed a tailored solution to match the special project requirements in order to be able to construct the 200,000 m² of floor space as cost-effectively as possible. The almost 90 m² tables only have four corner supports so that all the loads can be carried by the reinforced concrete columns without the need of any intermediate supports – and thus transferred without re-shoring measures into the lower floors. The so-called PERI DCS system (Deflection Compensating System) automatically levels the deflections which occur during concreting. In addition, the tables can be moved manually resulting in simple and fast moving procedures.Modern formwork systems allow an efficient and economical sequence of operations and provide the highest possible level of safety on the construction site. For forming the floor slabs, the contractor not only has conventional girder slab formwork but also panel slab formwork such as PERI SKYDECK and pre-assembled slab tables at his disposal. Interestingly enough, a few years ago PERI developed the SKYTABLE slab table in order to efficiently move up to 150 m² in only one crane lift. However, for the Canadian hospital project with its special requirements regarding slab dimensions, construction time and progress, a PERI special proposal proved to be the most cost-effective option. The main building of the medical facility is currently under construction and features two basement and eight upper levels each with around 20,000 m² of slab area. The 25 cm to 30 cm thick storey slabs are supported on 762 square-shaped reinforced concrete columns which are arranged in an unchanging grid formation of 9.60 m by 9.60 m. Standard storey height is 4.50 m. The construction schedule has been designed to ensure that building work takes place on several levels at the same time. On the basis of standard system components, engineers in Weissenhorn – in close co-operation with PERI Canada and project contractor Ellis Don – developed a special version of slab table through which the entire loads are transferred into the structure via only four corner supports in the area of the previously constructed concrete columns. This means that no shoring and re-shoring measures are required within the slab area resulting in significant workload savings as well as considerable reductions in material requirements. Loads of up to 237 kN per table support are directly transferred into the building structure by means of a clamping frame with swivel-mounted brackets. Additional mounting parts on the columns are not necessary here. A self-levelling system, comprised of sensors and hydraulic cylinders, guarantees that the slab table remains level when loaded: five sensors on each table record the respective deflections during concreting – depending on the measurement results, the hydraulic cylinders "react" accordingly and automatically raise the formwork back into an exact horizontal position. The system functions here with a tolerance of around 2 mm. Up to ten slab tables can be controlled at the same time through a common hydraulic unit. One big advantage was that PERI engineers could tap into the know-how and components used in the RCS self-climbing technology, also regarding the hydraulic control system. This is one of the reasons why PERI was in the position to deliver the first tables to the construction site after only needing a three-month planning, development and testing phase. Altogether 57 of these high-tech slab tables are currently in use which means an impressive 2,800 m² of slab area is completed each week. Specially-designed trolleys allow the tables to be easily and quickly moved in both longitudinal and lateral directions by hand without any additional means. These are likewise equipped with hydraulic cylinders in order to relieve and – after the brackets have been swivelled at the column frames – lowered by about 40 cm. The hospital complex, situated to the south of Calgary, is currently the largest construction site in Canada. The ground-breaking ceremony took place in 2007 and the structural work for the main building is part of Phase One which is scheduled to be finished at the end of 2011. Work on the entire campus will continue until 2018. South Health Campus is a community project of the Alberta Health Services and the Alberta government. Equipped with state-of-the-art technology, the facility will redefine the way patients, families and visitors experience health care services. In so doing, the client has also taken into consideration alternative healing methods and will be providing a very pleasant environment for the patients. When completed, the medical centre will have 644 in-patient beds and cater for 800,000 outpatient visits. write your comments about the article :: © 2010 Construction News :: home page |