Concrete cellular structures are used extensively for residential buildings. In concept they are structurally simple but they require attention to detail to realise the benefi ts of ease of construction and economy. This guide is written for the structural engineer who has knowledge of building structures in general but who has limited or no experience of designing concrete cellular structures. It highlights areas that require close coordination between the structural and services engineers, the architect and importantly the system supplier.
It also provides guidance on selecting an appropriate solution, sizing the structure and carrying out detailed design. Detailing considerations are explained, some of which have to be considered at the early stages of a project to achieve an effi cient building confi guration. Imagine some boxes, stacked upon one another, to gain a good impression of a cellular building (see Figure 1.1). Each box can be considered to be a cell with walls, a soffi t and a fl oor. The term cellular structures refers to cellular buildings where the walls of the cells are structural elements.
Cellular buildings are particularly effi cient for residential sectors such as: apartments hotels student residences key-worker accommodation prisons military barracks. Where the building use leads to clearly defi ned, permanent walls, cellular structures are very effi cient. In addition to carrying the vertical and horizontal loads the concrete walls can meet the following requirements: provision of fire resistance and compartmentation provision of acoustic separation concealed electrical services distribution minimal finishes to walls thermal mass, which can be used as part of a fabric energy storage (FES) design.
In addition, the systems in this guidance document have been refi ned to provide the following benefi ts: fast construction thin structural zone because the floors span on to line supports (150 to 250 mm depending on floor span) party walls as slim as 150 mm (depending on the solution adopted). There are three main systems of concrete construction available for cellular structures: tunnel form, crosswall and twinwall. With all these systems the early involvement of the specialist manufacturer or supplier will bring benefi ts in the form of expert advice and experience.
They will be able to maximise the effi ciency, productivity, buildability and cost-effectiveness of their systems for your project. The various systems are all described below and further expanded in subsequent chapters. An alternative system available for prisons comprises four individual cells cast as one volumetric unit complete with all furniture, sanitary ware and services. This is a specialist product, for which all the design and detailing is undertaken by the supplier. Further information is provided in Appendix A.
Tunnel form is a formwork system used to form cellular structures from in-situ concrete (see Figure 1.2). The system consists of inverted L-shaped ‘half tunnel’ forms which, when fi tted together, form the full tunnel. The system also incorporates gable-end platforms and stripping platforms for circulation and to strike the formwork. The cellular structure is formed by pouring the walls and slab monolithically. The system uses a 24-hour cycle.
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