Lever arm limit as per BS 8110

[kchadee]

BS 8110 limits the depth of lever arm to maximum 0.95 the effective depth. One reason i could find is because the top layer of concrete is usually of poor quality due to bleed water accumulating on top, therefore this limit on lever arm. Still having some doubts. Maybe someone can help

 

[1freewun]

I seem to remember the la is to the centre of the stress block if it became 1.0 you would have no stress block. There is also some merit in assuming surface concrete may not be as sound as internal material.

 

[ukengineer58]

interestingly eurocode puts no such limit. i do neverless