It is used in construction when you are working with
reinforcement steel. when you are at the end of any bar and
it has to be further extended to some more distence then
you are supposed to join it with an other bar (what ever
may be the dia) to this job simply we cannot do it. there
is a design and it depends on the location and design. in
most of the cases it is 50 times the diameter of the bar
which you are laping in some cases it may be 40times the
dia and in some drawings base on the requirementt and
design it will be a standardlength (300mm,400mm soon....)
the length of lap joint from joggle joint(where bar is
usually bend for lap) to end of bar is 48 times of diameter
of bar.but due to arises of problems in field is can be
taken as 50 times of diameter of bar.
dURING STEEL BINDING IN CONSTRUCTION ACTIVITY,AT SOME POINT STEEL BAR END COMES AND WE HAVE TO JOINT AN OTHER STEEL BAAR.How to overlap the steel baars at whic length?after seeing the ACI code ,seeing the dia of the bar,rferences in ACI code we get the formula to find the joint of the two bars(lap length,over lapping) is 50times dia of bar.