Minimal percentage of shear reinforcement (9.2.2(5))

The minimal percentage of shear reinforcement should not exceed minimal value defined in 9.2.2(5). Check looks as follows. Calculation of percentage of shear reinforcement from defined reinforcement is done according to formula 9.4.

ρ_w = A_sw / (s ∙ b_w ∙ sin(α))

where

• A_sw - Cross - sectional area of shear reinforcement
• b_w - shear effective width of cross-section
• s - longitudinal spacing of shear reinforcement
• α - angle between shear reinforcement and longitudinal axis of the member

 

Furthermore minimal allowed percentage of shear reinforcement is calculated as follows (see formula 9.5N).

ρ_w,min = 0.08 ∙ √f_ck / f_yk

where

• f_ck - characteristic cylinder strength of concrete member
• f_yk - characteristic yield strength of reinforcement material

Finally unity check is calculated as follows:

UC_9.2.2(5) = ρ_w,min / ρ_w

Clause 9.2.2.(5) - Minimal percentage of shear reinforcement for National annex

There are the following differences in particular NA.

National annex	formula 9.5N
Standard NA	0.08 ∙ √fck / fyk
German DIN-EN NA	0.16 ∙ fctm / fyk
Austrian ÖNORM-EN NA	0.15 ∙ fctm / fyd