47 The Decomo Ltd’s Project at One Coleman Street, London, in the heart of the city’s financial centre, is both unusual and striking in appearance. The building was designed by David Walker Architects in association with Swanke Hayden Connell and, on plan, is ovoid in shape. In keeping with many of the surrounding buildings, the original design, visualised the use of natural Portland Stone or Reconstructed Stone. The final solution, however, actually incorporates quite deeply ground and polished Precast Architectural Concrete columns and spandrels resulting in a more prominent degree of aggregate exposure. Whilst the building clearly has its own impressive identity, it is still very much in harmony with its surroundings. During 2005, representatives of the Client, along with key members of the Design Team, visited a number of specialist Precast Architectural Concrete Companies and their respective facilities both in the UK and on the Continent. The purpose of these visits was to find and select a ‘Partner’ who was able to provide the technical expertise and manufacturing quality required on such a prestigious Project. Decomo, clearly, ‘fitted the bill’ and was proud to have been awarded the order for the works. In arriving at their final selection, the Client and Design Team, placed much emphasis, not only upon the Company’s overall expertise and reputation for quality, but, in particular, upon the level of confidence, which they had felt, in Decomo’s ability to interpret the complexity of the building’s geometry and to develop this into a practicable and effective solution. At the core of this feeling of confidence were the demonstrable capabilities of Decomo’s, in-house’ Design Office and their use of the AllPlan drawing programme. This was used to ‘crack the geometrical code’ and to produce a 3-Dimensional simulation of a typical bay on the building. Once the Project got underway, much hard work and many meetings were required in order to translate the whole of the building into a complete 3-Dimensional model, thus ensuring that all lines, angles and interfaces could be accommodated, within the design and detailing, without mistakes and oversights, and that once, on site, the ‘pieces of the puzzle’ could be fitted together without problems. This especially applied to the steel backing structure, which was also modelled in 3-Dimensions to highlight any potential clashes with the rear faces of the Precast components and to avoid these within the final design/detailing. In all, the interesting shape of the building, together with the complex angular geometry of the individual elements, meant that, of the 425 No units, no single element was repeated more than six times. The largest elements were the ‘double storey’ columns, which were over 6.5 Metres high and weighed over 7.5 Tonnes. Each element type had to be detailed on ‘Production’ drawings, from which they were manufactured in Decomo’s factory. These were produced by, again, utilising the global 3-Dimensional model and ‘lifting off’ the individual components and creating fully dimensioned sections and views. The reinforcement design also had to be incorporated and, here, the All Plan programme proved invaluable. As the bending schedule is automatically generated, by the programme, the unique shapes required for the bending of links and the like could be clearly and accurately shown, without the need for the draughtsman spending much time on lengthy and tedious calculations, which could be prone to error. The Allplan programme was also used to create information incorporated into presentations, given by Decomo, to the Project Team to demonstrate how the components would be transported and installed. For the manufacture of the components, Decomo had to design and develop adjustable moulds that could be adapted for the casting of each element. The steel moulds consisted primarily of two main bottom shutters that could be fixed on a sub-frame in varying positions and planes to suit the unique angular geometry of the individual elements. Once cast, the components were ground and polished in the main Decomo’s automated polishing machines. Where necessary, small areas were finished using hand-held equipment. The Company also developed special rotisserie-like revolving frames to hold the components perfectly vertical or horizontal during polishing: this was critical to ensure consistency in the depth of grinding/ polishing and hence uniformity of appearance. The shape of the building, coupled with the individuality of the precast elements, placed much emphasis on the importance of accurate setting out and positioning of the units on the structure. This was carried out by erection specialists PCE Ltd, on Decomo’s behalf, using an ‘EDM Total Station’ working to coordinates generated by the Allplan programme. After installation, which was completed ahead of programme, the position of each element was checked relative to allowable tolerances, as was the width of each unit to unit joint. Following these checks, final grouting of connections took place and sealant works were undertaken. Comprehensive procedures were put in place for recording and hand over of the ‘as built’ situation appertaining to each window opening and this information was passed on to the glazing subcontractor for whom Decomo had cast fixing inserts into the units. A minimum period of 21 days was required from sealant application to installation of the windows to allow for curing of the sealant prior to loads being applied to the precast units. Decomo UK Ltd is very pleased to have been associated with this most prestigious building, which they firmly believe exemplifies exactly what can be achieved with the use of Architectural Concrete, when initial vision and coordinated design development, with a specialist sub-contractor, combine at an early stage in a project. Decomo UK Ltd’s works were completed ahead of programme and without the occurrence of any unforeseen problems, either within the fabrication or the, on site, installation of the components. This was due, in no small part, to the benefits of using the Allplan programme in the interpretation, design and detailing of Decomo’s works package. Client: Stanhope plc Architects: David Walker Architects Ltd/Swanke Hayden Connell Architects Engineer: Arup Façade Engineering Contractor: Bovis Lend Lease Precaster: Decomo Ltd Erector: PCE Ltd One Coleman Street
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