Figure

Procedure for determining vertical shear reinforcement

START

Determine VEd where VEd = design shear stress [VEd = VEd/bwZ = vEd/(0 9 bwd)]

Determine the concrete strut capacity vrj, max cot q = 2.5 from Table 7

Determine the concrete strut capacity vrj, max cot q = 2.5 from Table 7

(cot e = 2.5)

Determine e from:

Y = 0.5 sin-1

VEd

0.20fck (1 -fck/250)

Calculate area of shear reinforcement: Asw _ vEd bw s _ fywd cot Y

Check maximum spacing for vertical shear reinforcement: M.max = 0-75 d

Table 7

Minimum and maximum concrete strut capacity in terms of stress

Table 7

Minimum and maximum concrete strut capacity in terms of stress

|/ck

1 VRd,max cot O = 2.5

1 VRd,maxcot O = 1.0 |

2G

2.54

3.68

25

3.1G

4.5G

28

3.43

4.97

3G

3.64

5.28

32

3.84

5.58

35

4.15

6.G2

4G

4.63

6.72

45

5.G8

7.38

5G

5.51

8.GG

Eurocode 2 offers various methods for determining the stress-strain relationship of concrete. For simplicity and familiarity the method presented here is the simplified rectangular stress block, which is similar to that found in BS 8110 (see Figure 3).

Eurocode 2 gives recommendations for the design of concrete up to class C90/105. However, for concrete greater than class C50/60, the stress block is modified. It is important to note that concrete strength is based on the cylinder strength and not the cube strength (i.e. for class C30/37 the cylinder strength (fck) is 30 MPa, whereas the cube strength is 37 MPa).

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