Estimating Sheet

# Some common mistakes for lapping length in RCC column

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Mr. Sami Ullah, the renowned engineer comes with another useful tutorial for civil engineering students. In this video, one can learn some common mistakes for lapping length in RCC column in raft or mat foundation.

The civil engineers should be aware of these mistakes in the construction site.

The video focuses on the following topics :-

1. Lapping length for RCC column
2. Computation for Lapping length for column
3. How to calculate lapping length
4. Lapping length for beam
5. Lapping length for slab

The amount of overlapping among two bars is known as “lap length”. Lapping is generally provided where minimum bending stress exists. Normally, lap length is 50d i.e. 50 times the bar diameter, if both bars contain equivalent diameter.

Because of the limited length of bar, lapping of bars are necessary in a member with length in excess of 12m.

The purpose of lap length is to transmit the stress securely. It based on the grade of steel and diameter of bar. Not over 50% of bar should be lapped at one location.

With adherence to IS 456 : Plain and reinforcement concrete, the lap length should be at least equivalent to development length alias Ld. Since bond stress fluctuates for tension and compression, the lap length should be different for bars in tension and compression.

1. Lap length for tension members = 40d.2. Lap length for compression members = 50d.

D denotes the diameter of the bars to be lapped simultaneously. So if it is required to lap 20 mm dia column bars , you need to provide a lap of minimum 50 x20 = 1000 mm.

To get more detail on lapping length, go through this exclusive video tutorial.

Video Source: Sami Ullah