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Design of flat slab floors

Flat slabs design is appropriate for most floor situations and is also suitable for irregular column layouts, curved floor shapes, ramps etc. The benefits of choosing flat slabs include a minimum depth solution, speed of construction, flexibility in the plan layout (both in terms of the shape and column layout), a flat soffit (clean finishes and freedom of layout of services) and scope and space for the use of flying forms. The flexibility of flat slab construction can lead to high economy and yet allow the architect great freedom of form.

For many years, CIRIA Report 110 has been the standard document for the design of reinforced concrete flat slabs. Over that time analysis methods have changed and new construction methods have been developed. In the past few years there has been a significant increase in the use of finite element software packages both for the analysis and design of flat slabs. However, there is very little supporting information to allow engineers to understand the whole design process or verify the results of FEA. The publication of Eurocode 2 introduced changes in the design methods for flat slabs especially for punching shear. In addition the Designer is required to take greater responsibility for the Health and Safety implications of the method of construction. Many flat slabs are designed in an environment where the contractor should be involved. In the light of these various factors, The Concrete Society has published Technical Report 64, Guide to the design and construction of reinforced concrete flat slabs. The guidance in the Report is in accordance with Eurocode 2 (BS EN 1992) and the National Structural Concrete Specification.

The Report is intended for use by designers who already have basic understanding of structural behaviour. Besides design, the report covers typical behaviour, detailing and construction issues. A design example using FEA is given in one appendix. The scope includes flat slabs with orthogonal and irregular layouts of columns, plain soffits, waffle slabs, voided slabs and slabs with edge beams. It should be noted that solid flat slabs with a flat soffit are the most popular.

This Report does not cover the design of prestressed post-tensioned slabs; for such slabs reference should be made to Concrete Society Technical Report 43, Post-tensioned concrete floors: Design handbook.

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Solid flat slab

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