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Eurocode 2 provides specific guidance on the design of foundations for punching shear, and this varies from that given for slabs. In Eurocode 2 the shear perimeter has rounded corners and the forces directly resisted by the ground should be deducted (to avoid unnecessarily conservative designs). The critical perimeter should be found iteratively, but it is generally acceptable to check at d and 2d. Alternatively, a spreadsheet could be used (e.g. spreadsheet TCC81 from Spreadsheets for concrete design to BS 8110 and Eurocode 27). The procedure for determining the punching shear requirements is shown in Figure 4.
Table 6
vRd,c resistance of members without shear reinforcement, MPa
Table 6
vRd,c resistance of members without shear reinforcement, MPa
Ri |
Effective depth, d (mm) | |||||||
300 |
400 |
500 |
600 |
700 |
800 |
900 |
1000a | |
0.25% |
0.47 |
0.43 |
0.40 |
0.38 |
0.36 |
0.35 |
0.35 |
0.34 |
0.50% |
0.54 |
0.51 |
0.48 |
0.47 |
0.45 |
0.44 |
0.44 |
0.43 |
0.75% |
0.62 |
0.58 |
0.55 |
0.53 |
0.52 |
0.51 |
0.50 |
0.49 |
1.00% |
0.68 |
0.64 |
0.61 |
0.59 |
0.57 |
0.56 |
0.55 |
0.54 |
1.25% |
0.73 |
0.69 |
0.66 |
0.63 |
0.62 |
0.60 |
0.59 |
0.58 |
1.50% |
0.78 |
0.73 |
0.70 |
0.67 |
0.65 |
0.64 |
0.63 |
0.62 |
1.75% |
0.82 |
0.77 |
0.73 |
0.71 |
0.69 |
0.67 |
0.66 |
0.65 |
>2.00% |
0.85 |
0.80 |
0.77 |
0.74 |
0.72 |
0.70 |
0.69 |
0.68 |
k |
1.816 |
1.707 |
1.632 |
1.577 |
1.535 |
1.500 |
1.471 |
1.447 |
Key a For depths greater than 1000 calculate vRd,c directly. Notes
1 Table derived from: vnc = 0.12 k (100ri fc,)M > 0.035 k15 f,0-5 where k = 1 + -/(200/d) < 2 and pi = V(pY +Riz) < 0.02,
2 This table has been prepared for fc, = 30;
Key a For depths greater than 1000 calculate vRd,c directly. Notes
1 Table derived from: vnc = 0.12 k (100ri fc,)M > 0.035 k15 f,0-5 where k = 1 + -/(200/d) < 2 and pi = V(pY +Riz) < 0.02,
2 This table has been prepared for fc, = 30;
fck |
25 |
28 |
32 |
35 |
40 |
45 |
50 |
Factor |
0.94 |
0.98 |
1.02 |
1.05 |
1.10 |
1.14 |
Shear checks for pad foundations Figure 3 Shear checks for pad foundations |
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