Cast-in channel was invented almost 100 years ago in 1913 by Anders Jordahl and in the time since then it has become established as one of the most efficient and reliable means of connecting things to concrete. As can be seen from the original patent paper, the principle is largely unchanged.
Historically, most channels used in UK were manufactured by two German manufacturers, and their range of channel profiles is virtually identical. They published loading data based on their own tests, allowing users to select a suitable product for a given situation. However, as there were no laid down procedures for the testing or the interpretation of the test results, we had the undesirable position where two apparently identical profiles could have somewhat different published capacities. Until recently there were no standards or agreed rules governing the design of channels.
Two recent events prompted action on this situation. Firstly, cheap clones of profiles came in from the Far East. These often suffered from quality problems and do not have the technical backup of the main manufacturers.
For example, if the material is too thin then the lips can bend under load, and if too thick, cracking can occur during rolling causing longitudinal failure.
Secondly, the standard BS EN 1992-1-1:2004 – Eurocode 2: Design of concrete structures .General rules and rules for buildings (EC2) was published, and has now taken over from BS8110 as the principle design standard covering concrete structures. This states in clause 2.7 that “The performance of fasteners should comply with the requirements of a CEN standard or should be demonstrated by a European Technical Approval (ETA)”. In simple terms this means that using a channel without an ETA will result in a non-compliant design. This could have significant implications for insurers of projects and the liability of designers and suppliers.
To address this, the major channel manufacturers began a process in 1999 to evolve a completely new, comprehensive test and design method.
The old loading data was based on uncracked concrete and included limitations on parameters such as edge distance, corners, concrete depth, centres of fixing etc. If the minimum values given were not achieved, then no solution was found. The new methods go far beyond this.
A new Standard, CEN/TS 1992-4-3:2009 - Design of fastenings for use in concrete Part 4-3: Anchor channels was developed and the UK version published by BSI in 2009. This sets out the factors that have to be applied to characteristic resistances under differing circumstances. The actual characteristic resistances and the reduction factors are established by very extensive testing.