Details about desired overlapping length in beam, column and slab
In this construction video tutorial, you will get some useful information on working out the overlapping length of steel for beam, column and slab.
The purpose of overlapping length is to retain the continuation of the bars to securely transmit the load from one bar to another bar. To securely transmit the load one bar is overlapped with another bar and length of smaller dia is taken as lap length.
Lap length varies in column, beam and slab as follow :-
- According to IS code 456-2000 overlapping length should not be under 75 mm.
- For column, usually, 24d to 40 d is taken, where d denotes diameter of bar.
Given below, some vital points about lapping :-
- Lapping should be arranged at the midpoint of the column.
- Lapping of bars should be arranged alternatively.
- Lateral ties should be placed narrowly in lapping zone.
- For beam, usually, 24d is chosen for compression zone and 45d for tensile zone.
- Lapping should not be arranged at the midpoint of beam rather it should be arranged at the meeting point of column & beam or in L/4 length from the casting face of column.
- The stirrups should placed narrowly at lapping zone.
- Lapping of bars should be arranged alternately.
- For slab, lap length should be chosen as 50d where d denotes diameter of bar.