Lapping – what is it?
It’s got nothing to do with being over taken on the F1 track. Lapping refers to the “overlapping” of reinforcement with another section of reinforcement.
Why do we lap?
- It gives greater structural integrity to the structure you are fabricating. What does this mean? It means that when you lap, your concrete will be stronger, and will be better able to withstand loads/weights. In other words, a lapped structure will be more sturdy that unlapped structures.
- AS 2870 requires that we lap.
Lapping Requirements?
Trench Mesh Laps
- If they are overlapping at T or L intersections, then overlap the full width of the mesh.
- When end to end, they need to be at least 500 mm.
Please see below:
Square mesh lap
- These need to be lapped by 225 mm minimally.
Very similar to the above – please refer to that diagram.
Reinforcing Bar Laps
- Lapping needs to be at minimally: 500 mm.
Please see below:
I hope this helps you. Any questions? Feel free to ask. I may even write up another post if the question is good enough.
Why in practise one of the lapped bar is straight while the other is a little bent?
Hi Ken – are you able to elaborate a little more? I have no answer to your question as it stands. rgds, Koshy
Thanks for your reply. Actually I saw it from a figure below:
https://holland.pk/4o85szkn
It appears that one of the lapped bar is bent while the other isn’t. Or is it just a drawing convention problem?
And just one more question if you don’t mind:
I don’t get why the lapped bars have to be positioned differently when placed on the top vs at the bottom in order to ensure that the concrete thickness will not reduce, as stated in the figure. My thought is that both positioning ways occupy the same volume.
Thank you very much!
Hi there Ken
I have whipped up an answer to your question: you can find it here: http://www.tek1.com.au/concrete-cover-important/ any further questions ask away. rgds, Koshy