Cast-in Channels
The use of cast-in channels is widely recognised as a fast and efficient way of fixing the facade brackets tot he slab, as it is never easy to use post-fix anchors when you must consider the implications of striking reinforcing bars within the concrete, or more importantly, the restriction of drilling the slab within the location of pre-tensioning rods.
There are therefore items that you must be aware of when designing or using cast-in channels, a few of which I will list as follows:
1. The position of the cast-in channel is critical when considering its distance from the edge of the slab, as this distance will affect the load being transferred to the channel
2. The position of the cast-in channel is critical in regard to its effective level to the surface of the slab. If it is too deep you will need to use shim plates to ensure the load from the bracket is directly transferred to the channel, if it is too high, the channel can become effectively redundant.
3. Cast-in channels which are located within the air line of the building will normally be hot dip galvanised. This is good practice as the bi-metallic reaction between aluminium and zinc is negligible in dry condition.
4. Cast-in channels which are located outside the air line of the building should be stainless steel.
The normal positioning tolerances for cast-in channels would be +/-25mm in X and Y direction, and +/-2mm to the surface of the slab (note this is not a tolerance to the slab level relevant to the theoretical, it is strictly the deviation between the channel and the actual poured slab surface).
Channel Designs:
Depending on the intended applied load and the intended concrete construction, there are variations for cast-in channels which begin with the typical welded studs of varying depths as required, then there is an option for welded I-shape anchors, and also there is an option for welded straps, often referred to as ski's.
The ski option whilst more expensive, is much better suited to steel deck slab construction since it serves two great services, the first that it is simple to install as it will simply sit on the deck, the second, is that if you extend the front ski, you can guarantee that the distance from slab edge to channel centre is always the same. The only thing to be careful when designing for this option, is that you make consideration for the raised nibs on a typical deck profile.
Very good sources of information for cast-in channels can be found at both the following links:
http://81.167.44.246/pdf_eng/jta.pdf (Jordhal anchor fixings)
http://www.halfen-fixings.co.uk (Halfen anchor fixings)
There are therefore items that you must be aware of when designing or using cast-in channels, a few of which I will list as follows:
1. The position of the cast-in channel is critical when considering its distance from the edge of the slab, as this distance will affect the load being transferred to the channel
2. The position of the cast-in channel is critical in regard to its effective level to the surface of the slab. If it is too deep you will need to use shim plates to ensure the load from the bracket is directly transferred to the channel, if it is too high, the channel can become effectively redundant.
3. Cast-in channels which are located within the air line of the building will normally be hot dip galvanised. This is good practice as the bi-metallic reaction between aluminium and zinc is negligible in dry condition.
4. Cast-in channels which are located outside the air line of the building should be stainless steel.
The normal positioning tolerances for cast-in channels would be +/-25mm in X and Y direction, and +/-2mm to the surface of the slab (note this is not a tolerance to the slab level relevant to the theoretical, it is strictly the deviation between the channel and the actual poured slab surface).
Channel Designs:
Depending on the intended applied load and the intended concrete construction, there are variations for cast-in channels which begin with the typical welded studs of varying depths as required, then there is an option for welded I-shape anchors, and also there is an option for welded straps, often referred to as ski's.
The ski option whilst more expensive, is much better suited to steel deck slab construction since it serves two great services, the first that it is simple to install as it will simply sit on the deck, the second, is that if you extend the front ski, you can guarantee that the distance from slab edge to channel centre is always the same. The only thing to be careful when designing for this option, is that you make consideration for the raised nibs on a typical deck profile.
Very good sources of information for cast-in channels can be found at both the following links:
http://81.167.44.246/pdf_eng/jta.pdf (Jordhal anchor fixings)
http://www.halfen-fixings.co.uk (Halfen anchor fixings)