Q. Reinforced concrete design?

In BS8110 for reinforced concrete design, it is stated that longer tension lap lengths have to be provided at the top of concrete members. The motive behind this is that the amount of compaction of the top of concrete members at the time of concrete placing is more supposed to be less than the remaining concrete sections. Furthermorebecause of the possible effect of segregation and bleeding, upper layer of concrete section likely to be of lower strength when compared with other locations.  

When the lap lengths are placed at the corners of concrete members, degree of confinement to the bars is supposed to be less than that in other locations of concrete members. As such, by taking into account the smaller confinement which result in lower bond strength, a factor of 1.4 (means 40% longer) is applied to calculated lap length.