© EN 1537 states that the characteristic anchorage capacity shall be the minimum of the capacity from a geotechnical calculation of the grout/ground interface resistance and the tensile capacity of the tendon. EN 1537 implies that the tendon capacity should govern the design.

© ENs 1997-1 and 1537 provide different values for Ya. Work is underway in the relevant CEN technical committees to resolve these differences.

© It is normal to use a larger-diameter tendon in investigation tests than for the working tendon to ensure that where failure occurs it is between the grout and the tendon or the grout and the ground, not the tendon itself.

© EN 1537 provides upper limits for the test load based on the tendon capacity.

© The investigation test failed at 580kN (less than the proof load), which confirms that the capacity of the grout/ground interface is at least as large as the calculated value of 559kN.

© EN 1537 recommends that the lock-off load P0 be a maximum of 0.6Ptk. Typically, P0 is between 40 and 60% of Ptk.

© EN 1537 recommends these limits for suitability tests coupled with correlation factors for three or more tests. Both ENs 1997-1 and 1537 recommend that at least three suitability tests are performed.

® If EN 1537's value of Ya is used, the suitability results indicate that the anchor does not meet requirements.

© The recommendation of Frank et al.18 — that the proof load for acceptance tests should not exceed 1.15 RgLS, where RgLS is the anchor load derived from a serviceability limit state calculation of the retaining wall — has not been adopted here.

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