Info

Ribbed wires

|55|

I 50 |

I 45 |

| 40 |

| 35 |

| 30 |

(4) The design value lbpd is to be taken at 0,8 or 1,2 l^p whichever is less favourable for the effect considered.

(5) Transmission length, anchorage length and dispersion length are to be taken from the start of effective bond.

Start of effective bond should take account of:

— tendons purposely debonded, at the end

— a neutralised zone lbpo in the case of sudden release

(6) For rectangular cross-sections and straight tendons, situated near the bottom of the section, the dispersion length can be established as:

(7) The anchorage of pretensioning tendons in flexural members at the ultimate limit state is influenced by the condition, cracked or uncracked, of the anchorage zone. The part of the beam where tendons are anchored [Figure 4.9 a)] may be considered as uncracked if the concrete tensile stress at the ULS (flexural and principal stresses) does not exceed fctd, taking, account of the relevant value of Pd (See 2.5.4).

(8) If the tensile stress does not exceed fct 0.05, the conditions of anchorage may be assumed to be fulfilled without further checks.

(9) If the tensile stress exceeds fct 0.05, it should be shown that the envelope of the acting tensile force according to Figure 5.11 does not exceed the resisting tensile force provided by the tendons and the reinforcing steel within the anchorage zone. The ultimate resisting force Fpx of the tendons according to Figure 4.9 c) may be determined as:

Po as defined in 2.5.4.2 P(1) lbpd as defined in (4) above.

4.2.3.5.7 Anchorage zones of post-tensioned members

P(1) The design of anchorage zones shall be in accordance with the procedures in this section and those in 2.5.4, 4.2.3, 5.4.6 and 5.4.8.

P(2) When considering the effects of the prestress as a concentrated force on the anchorage zone, the characteristic tensile strength of the tendon shall be used.

(3) The bearing stress behind anchorage plates should be calculated in accordance with 5.4.8.

(4) Tensile forces due to concentrated forces should be assessed by a strut and the tie model, or other appropriate representation (see 2.5.3.6.3 and 2.5.3.7.4). The resulting reinforcement should be detailed in accordance with 5.4.6, assuming that it is acting at its design strength.

(5) The prestressing force may be assumed to disperse at an angle of spread 2" (see Figure 4.10), starting at the end of the anchorage device, where " may be assumed to be arc tangent 2/3.

Column Chart Eurocode
Figure 4.9 c) — Derivation of Equation (4.14)
Column Chart Eurocode
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