A group of structural engineering experts led by the Institution of Structural Engineers (IStructE) has compiled a free new guide to help building designers, contractors, and assessors better understand the complexities of a common solution in building design – the transfer slab.
“Design of transfer slabs” has been created by AECOM, IStructE, MPA The Concrete Centre, and Imperial College London, with technical reviews provided by Buro Happold and Simpson TWS.
The technical guide is intended for the design of new transfer slabs. The assessment of existing slabs is not covered.
It provides guidance on concept design, design for robustness, and suitable methods for the assessment of punching shear in transfer slabs. The recommended punching shear assessment methods differ significantly from the methods used in typical flat slabs.
Despite being a widespread typology, the document suggests that there is currently a lack of understanding, robustness and consistency in the design approaches adopted for transfer slabs. Industry should be pushing for designers, contractors and assessors to understand the inherent complexities, safety implications, and sustainability issues of adopting this construction method.
Patrick Hayes, Technical Director at IStructE says: “At present, there is no industry-wide guidance for the design of a transfer slab, especially for punching shear. To do this work successfully, an engineer needs to have a great understanding of the behaviours of concrete, how column shears interact, disproportionate collapse, and construction sequence effects. It’s a complex process.
“We’ve therefore worked together with industry on this guide to fill a significant knowledge gap in the design of reinforced concrete (RC) buildings with transfer slabs that has a potentially major impact on safety.”
To raise awareness on this important topic further, IStructE ran an event “Transfer slabs: getting it right from the start” on 22 October 2024. Patrick Hayes and Emily Halliwell, Senior Structral Engineer at MPA The Concrete Centre spoke at the event and it is available on demand here: https://www.istructe.org/events/hq/2024/transfer-slabs-getting-it-right-from-the-start/
A related online event Transfer slabs: focus on punching shear design is on the 19 November 2024. Book here: https://www.istructe.org/events/hq/2024/transfer-slabs-punching-shear-design/
What is a transfer slab? A transfer slab takes the load from columns that sit above the slab and transfers it to supporting columns placed underneath without the provision of transfer beams.
They are commonly used in reinforced concrete (RC) buildings throughout the world to facilitate a change in column grid, for example as ground floor podium slabs in mixed-use tower blocks, or at high level to allow for a step back in a building for architectural reasons.
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For further information please contact:
The Institution of Structural Engineers (IStructE) Newsroom on +44 (0)7930 53 45 43.
Notes to Editors
Important notes about the guidance
- As with all aspects of RC design in the UK, transfer slabs should be designed and detailed in accordance with BS EN 1992-1-1.
- The guide is limited to buildings of 15 storeys or fewer.
About the Institution of Structural Engineers (IStructE) https://www.istructe.org/
The Institution of Structural Engineers dates to 1908 and is now the world’s largest membership organisation dedicated to the art and science of structural engineering.
It has over 29,000 members working in 138 countries around the world. Professional membership is one of the leading global benchmarks of competence and technical excellence. Members undergo rigorous technical assessment and commit to continual learning and development.
The Institution drives higher standards and shares knowledge because its members’ work is vital to public safety and meeting the challenges of the future. The Institution provides a voice for its members, promoting their contribution to society as innovative, creative problem solvers and the guardians of public safety.