Expert: Dan Griffin - 4/2/2010

Question
Respected Sir,
I want to know that whether it is encouraged to tie up reinforcement of concrete column continuously without providing laps (upto 2,3,4 or more floors)? Some say laps are essential, some say laps are provided where we have to cut the reinforcement and then continue again for the next upcoming floor, some say laps are neccessary as it gives seismic resistance! (As far as seismic resistance is concerned columns are designed by applying seismic factors)
I just want to know a concrete reason behind it.
(Kindly note that all the questions asked are based on construction site queries. Referring building codes is not actually the answer i want).

Thanks.
I am anxiously waiting for your reply.

Answer
Haider, I am not a structural engineer.

I am not aware of any reasons for non continuous steel reinforcement in columns.  Bridges are very commonly held up by very tall columns.  Horizontal beams are often over 40 feet.   The limiting factors that I see would be the lengths of steel available and the ability and equipment to deal with the lengths.  Form work must be much stronger as the height increases.

there is usually concern about concrete quantity, sufficient cover, and potential for honeycomb where steel is lapped as it can be quite difficult for the aggregate to get past some of the restrictions.  I wish I had better answers for  you.