Uap

4.2.3.5.6 Anchorage zones of pretensioned members

(1) Where tensile forces can occur, they should be carried by additional reinforcement.

(2) A distinction has to be made (see Figure 4.9 a) between:

i) transmission length lbp, over which the prestressing force (Po) from a pretensioned tendon is fully transmitted to the concrete.

ii) dispersion length lp.eff over which the concrete stresses gradually disperse to a linear distribution across the concrete section.

iii) anchorage length lba, over which the ultimate tendon force (Fpu) in pretensioned members is fully transmitted to the concrete (see 2.5.3.7.4).

The zones interact.

Eurocode Reinforcing Mesh

(3) The transmission length l^p is influenced by the size and type of tendon, the surface condition of the tendon, the concrete strength, the degree of compaction of the concrete. Values should be based on experimental data or experience with the type of tendon to be used. For design purposes, [Figure 4.9 b] the transmission length is defined as a multiple of the nominal diameter (0) of the strand or wire:

For strands having a cross-sectional area < 100 mm2, and for indented wires with diameter < 8 mm, all complying with surface characteristics specified in relevant Standards and tensioned according to the values given in 4.2.3.5.4, the "b values given in Table 4.7 may be adopted. The concrete strength taken should be that at the moment of transfer. Where the use of ribbed wires is proposed, with diameter < 12 mm, values for should be based on test data; as a guide, the values in Table 4.7 may be adopted.

Table 4.7 — Factor to be taken for transmission length of prestressing strands and wires (smooth or indented) in relation to concrete strength at the moment of transfer

Table 4.7 — Factor to be taken for transmission length of prestressing strands and wires (smooth or indented) in relation to concrete strength at the moment of transfer

Actual concrete strength at transfer (N/mm2)

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