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Civil Engineering - Interview Questions
What are the general rules for lap length?
When the bars of different diameters are to be spliced the lap length is calculated considering the smaller diameter bars. 
 
* Suppose you are constructing a column, from bottom 20 mm diameter bar is coming and from here 16 mm diameter bar has to be spliced then for calculating lap length 16 mm diameter should be considered and not 20 mm.
 
* If the diameter of the bar is more than 36 mm then lapping should not be done instead of lapping, this bar should be welded. 
 
* But when welding is not possible then lapping can be permitted for bars larger than 36 mm but in this case, additional spirals shall be provided around the lapped bar.
 
* Lapping should be done in a staggered manner. These laps should not be given at the same level to avoid buckling. The stirrup shall be closely spaced in the lapping portion. 
 
* It’s because when we provide lapping in concrete members the strength of the member slightly reduces. Hence, we need to provide more numbers of stirrups in this portion.
 
* In the case of bundled bars, lap splices of bundle bars shall be made by splicing one bar at a time. Such individual splices within a bundle shall be staggered.
 
* In this image you can see some amount of rebar is left for future construction with extra rebar will be needed for tying bars of the column. This extra length of rebar is also called lap length. 
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