Answer:

Steel pipe in length direction is curved, expressed its curve degree with numbers is called bending degrees. By the standard of the degree of curvature  generally falls  into the following two kinds:

the following two kinds:
 
A、Local flexibility: with one metre long straightedge by the amount of steel tube bend, measuring its largest string high (mm), namely for local flexibility, its numerical unit is mm/m, said methods such as 2.5 mm/m. This method is also applicable to the pipe end of curving degrees.

B.The total length of bending: with a string, tighten the two ends of the tube, 
measuring the maximum chord pipe bend (mm), and degree of conversion growth (in 
meters) of the percentage, is the pipe length of the total length of bending.

For example: pipe length is 8m, the measured maximum chord height 30mm, the bending 
of the tube length should be:

0.03÷8m×100%=0.375%