Local ductility of walls

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Local ductility of walls

For ductile wall Ec8 prescribes a lot of detailing rules in §

In the critical region of the wall the width Lc of the confined boundary zones (see below figure) must be not lesser than 0.15 lw and  of 1.5 b, and the minimum longitudinal reinforcement ratio is 0.005.






For large lightly reinforced walls the length Lc of the boundary zones should extend (in lw direction) for a value not less than b or  2 ·b·scm/fcd  where scm is the mean value of the compressive stress.

The local ductility check to perform for the ductile walls in the critical region is ensured by the following relation:



         α wwd30 mf (nd + wv) εsy bc/b0 - 0.035                        (5.20) EC8


in cui:


α        = αs · αn  = confinement effectiveness factor in Lc end zoned (as in the in previous topic)        

wwd        =  (Ast,x/(sb0) + Ast,y/(s h0)) · fyd/fcd   = wx + wy

mf          required curvature ductility factor to calculate with (5.4) or (5.5) EC8 where q0 is amplified with the factor MEd/MRd

wv          = mechanical ratio of vertical web reinforcement (rv fyd/fcd).


wwd ≥ 0.08 in CDM class and  0.12 in CDH class.


It should also be checked for length Lc of the areas confined primarily considering the length of the compressed area xu ULS (see figure) after spalling of the concrete cover:

         xu = (nd + wv) lw b/b0


where lw is the width of the section and b0 is the thickness of the confined end zones.

Lc must be ≥  L'  length where concrete strain  if greater than 0.0035 :

                   Lc ≥ L'  = xu (1-εcu2/εcu2,c)



εcu2 =0.0035

εcu2 = 0.0035 + 0.1 α wwd