Author: L. Hurst and A. Dutton (Consultants, Hurst Peirce + Malcolm LLP)
1st July 2015
First published: 1st July 2015
Standard: £9 + VAT
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L. Hurst and A. Dutton (Consultants, Hurst Peirce + Malcolm LLP)
Post-tensioned (PT) concrete floors are now widely used in the UK, particularly for high-rise buildings. This article provides information on how to scheme a PT slab and how the use of post-tensioning affects the rest of the structure. A more detailed guide to the design of PT floors can be found in The Concrete Society's Technical Report 43 (TR43): Post-tensioned concrete floors: Design handbook.
This article suggests ways in which readily available technology (a smartphone or tablet) can provide engineers and construction professionals with a simple tool to test vibrations. This is demonstrated on the new feature staircase (a lightweight and unusual structure) at the Institution's HQ in London. A free-to-download vibration testing app (beta version) has been developed by Expedition, and is introduced here.
In conservation work and like-for-like repair on older masonry, lime mortar is the only recommended material. The thick, plain or lightly punctured walls that make up most historic buildings have few concentrations of load. Calculations of stress in such cases are often needless and, subject perhaps to the check of any critical element, we can generally lay aside our concerns about mortar strength.
In contrast, the need to maintain a balance of moisture and flexibility in the body of an old wall is essential. Ignoring this will lead to the classic error of repointing old structures in brittle, impermeable Portland cement
(OPC) mortar. The mortar provides the route for evaporation from the core and should be more permeable than the brick or stone. To reverse this by sealing the joints with a hard finish can only lead to trouble.