Precast panels are heavy.
Cranes are used to lift the panels into place into their appropriate place. Because the mass involved is significant, it is very important that all the components of the lifting system are properly engineered and designed. If this is not the case then the panel could fall – and that can be lethal.
In those post we will be focusing on lifters.
This is how we denote a lifter:
This is how a lifter anchor looks like in real life.
Let us explain everything in detail – the purpose and what it does.
- The Void
Precast panels are made in moulds. Items are placed in the mould and wet concrete is poured into it. The concrete is like water. You can’t have anything projecting out of the mould – everything must be contained within the mould itself. In other words, you need to provide a hook or latch onto the panel if you want to lift it. And the hook cannot project out of the panel because then it would be very hard to cast such a panel.
Imagine if someone fabricated the above panel – you will notice that the lifter is sticking out of the panel. This would be very hard to fabricate. Because it would require a hole to be exposed within the wet concrete for the lifter to protrude out from. Consequently, lifters are placed within the panel outline. And in order to facilitate the ability of a lifting system to latch onto the panel, a small depression and hook is provided within the panel. In reality, the panel will look something more like this:
You will notice that the actual concrete panel follows the white outline above, and that there is a depression in the panel. In addition – and this is not shown in the above diagram, there is a loop like feature on the end of the lifter which allows one to use it to haul the entire panel up into the sky etc. e.g. notice the hole at the top of the lifter shown below. It is this hole that is used to affix the lifter/panel to suspension systems.
- The Tail bar and reo – it’s importance in the safety/stability of the lifting system
The second thing to note in the above diagram is the tail bar and reo. Why is this important? It’s important if you want to be able to safely lift the panel. If you forget to add the tail bar and reo, and simply add a lifter without those items – then when you attempt to lift the panel, the concrete will simply break off where the lifter is and the panel will fall to the ground – potentially killing people under the panel as it is being hauled up.
The tail bar and reo provide very important friction which ensures that the panel is safely secured to the lifter when it is in the concrete. Without it, the weight of the panel will simply cause it to separate from the lifter as it is being hauled up.
Generally Tek1’s practice is to draw the lifter only. It is assumed to be standard factory knowledge that the tail bar should be added when the panel is cast. We make assumptions that the guys on the factory know what they are doing.
- Mesh
The mesh is what gives the concrete some additional strength. It’s important.
In tomorrow’s post we will more closely investigate the lifter and certain matters pertaining to lifting.
