How to calculate overlapping length for beam and column

How to calculate overlapping length for beam and column, in this topic we know about how to calculate overlapping length of beam and column. we know that beam and column is RCC structure of any building in which reinforcement of concrete is provided.

According to design of structure we form column and beam, as we know that length of one piece reinforcement Steel is about 12 metre, if we have 3 storey 5 storey and multi storey building structure then we require overlapping of reinforcement.

The purpose of overlapping length is to retain the continuation of the steel bars to securely transmit the load from one steel bar to another bar. To securely transmit the load one bar is overlapped with another steel bar and length of smaller length of bar is taken as lap length.

Now question is arises how we calculate minimum overlapping length of column and beam

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overlapping length for column

1) overlapping length is also known as lap length

2) lap length for column depends on Grade of concrete which was used and grade of Steel, as per IS code there is no any specific rule to provide how much length of lap length

3) lap length for column should be 24d to 40d according to concrete of grade and grade of Steel which was provided, generally we take 40d for column where d is stand for diameter of reinforcement, if there is reinforcement dia 12 mm then overlapping length of column should be 40×12 = 480 mm

For 12 mm, 40×12 = 480 mm lap length

For 16 mm, 40×16 = 640 mm lap length

For 25 mm, 40×25 =1000 mm lap length

4) lap length should be provided in centre of column not in upper L/4 and lower L/4 structure length of beam. Because of maximum tension present in upper and lower part of column reinforcement.

5) in overlapping length of column lateral ties should be more nearer to one another it should have 100 mm spacing which prevent from buckling of reinforcement in column.

6) lap length provided in reinforcement of column should be placed alternately.

how to calculate overlapping length for beam

1) we know that beam is horizontal RCC structure put over column

2) in RCC beam lap length should be in between 24d to 45d, where is d is diameter of reinforcement which was provided in beam structure

3) in RCC beam lap length should not be provided in centre of beam because of maximum compression and tensile zone it should be provided in column and beam junction and start of beam structure and in first part and last L/4 effective length of beam.

4) upper reinforcement provided in beam is in compression zone, for compression zone reinforcement lap length should be 24d and for lower reinforcement provided in beam is in tensile zone for tensile zone reinforcement lap length should be 45d

If reinforcement dia which was provided in tensile zone of beam is 12 mm then lap length should be, 12×45 =540 mm

If reinforcement dia which was provided in compression zone of beam is 10 mm then lap length should be,10×24=240 mm