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Design Approach 2 (summary)

Verification of rotational stability Nominal depth of embedment dnom = 7.49 m kNm m

Rotational equilibrium MEd = 9519-

Degree of utilization

Design is unacceptable if the degree of utilization is > 100%

Anchor must be designed to carry force Fd = 267-

kNm m m

Degree of utilization m

Wall section must be designed for...

Maximum bending moment of Md max = -819-

Maximum shear force of Vd max = -257-

kNm m

Design Approach 3 (summary)

Verification of rotational stability Nominal depth of embedment dnom = 5.85 m kNm m

Rotational equilibrium MEd = 4969-

Degree of utilization

Design is unacceptable if the degree of utilization is > 100%

Anchor must be designed to carry force Fd = 184-

kNm m m

Degree of utilization m

Wall section must be designed for...

Maximum bending moment of Md max = -503-

Maximum shear force of Vd max = -176-

kNm m

© Earth pressure coefficients are taken from Annex C of EN 1997-1.

© Applying the 'Single-Source Principle' (see Chapter 3) results in the unfavourable partial factor on actions being applied to both active and passive pressures.

© The 'Single-Source Principle' should be applied to pore water pressures as well as earth pressures, resulting in the unfavourable partial factor on actions being applied to the water pressures on both sides of the wall.

© Design Approach 1, Combination 2 (DA1-2) gives the most critical result, indicating that the design length of wall is just sufficient to meet the requirements of Eurocode 7.

© When considering the forces in the anchor, Design Approach 1 Combination 1 (DA1-1) suggests that a negative anchor force is needed to maintain horizontal equilibrium! This arises because passive pressures have been multiplied by yg = 1.35, enhancing their effect and reducing the need for support from the anchor. A more sensible calculation for DA1-1 (given on the book's website - see details below) would be for an embedment d = 4.35m. With this length, the degree of utilization for DA1-1 is 100% and the anchor force needed increases to 181 kN/m.

© Once the minimum wall length has been obtained, further analysis is required to establish the maximum bending moment Mdmax and shear force Vd,max in the wall (to allow selection of an appropriate wall section). Combination 2 gives Mdmax = 503 kNm/m and Vdmax = 176 kN/m (whereas a similar calculation for Combination 1 gives 450 kNm/m and 172 kN/m, respectively, both of which are smaller than for Combination 2). Furthermore, an additional calculation with all partial factors set to 1.0 should be performed to check that a more onerous anchor force is not obtained under serviceability conditions.

© The results for Design Approaches 2 and 3 are presented in summary only. The full calculations are available from the book's website at www.decodingeurocode7.com.

Design Approach 2 applies factors greater than 1.0 to action effects (i.e. active earth pressures) and resistance (i.e. passive earth pressures). The depth of embedment needed to obtain a degree of utilization of 100% is 7.49m, which is longer than for DA1. The maximum bending moment and shear force in the wall are 819 kNm/m and 257 kN/m and the anchor force required is

267 kN/m - all of which are considerably greater than for Design Approach 1, because the wall is so much longer.

Design Approach 3 applies factors greater than 1.0 to structural actions and material properties. Earth pressures arising from the self-weight of the ground are treated as a geotechnical action and factored by yg = 1.0; earth pressures arising from the surcharge are treated as structural and factored by Yq = 1.5 (versus 1.3 in DA1-2). The depth of embedment needed to obtain a degree of utilization of 100% is 5.85m, which is identical to DA1-2. The maximum bending moment and shear force in the wall and the required anchor force are also identical to Design Approach 1, Combination 2.

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