(05) Системы преднапряжения / (3) Freyssinet - Домкраты и элементы (eng)

Grouting operation

•External prestressing tendon

–Wax injected further « circulaire n° 2001 » - a1 type

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Good practice in PT works

1.Duct Installation

1.1Important aspects:

•Following the design profile and securing the position of the duct

•Maintaining the original shape of the duct during installation and concreting

•Proper duct connections

•Good design coordination the post tensioning and reinforcement

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Good practice in PT works

1.Duct Installation

1.2Possible problems

•Friction points

•Deformation of duct cross section

•Damage of the duct

•Improper duct connection

•Duct displacement

•Clashing of rebar and duct

•Clashing of ducts

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Good practice in PT works

1.Duct Installation

1.3Preventive measures

•Sufficient duct supports

•Duct connections

•Connection to the trumplate

•Thorough check of the duct before casting of concrete

•Monitoring the tendons during and immediately after casting

•Order of design

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Good practice in PT works

3.Stressing

3.1Important before commencement:

• Inspection of concrete surrounding the stressing zones

•Friction test

•Inspection of blocks, wedges

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Good practice in PT works

3.Stressing

3.2Possible problems:

High elongation before achieving the required force:

•Slippage of wedges

•Broken wires or strands Insufficient elongation of tendon

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Good practice in PT works

3.Stressing

3.3Preventive measures:

•Experienced operators and good equipment

•Steady application of force and monitoring of results

•Good coordination between stressing teams

•Monitoring of tendon during stressing

•Monitoring of tendon after stressing

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Good practice in PT works

4.Grouting

4.1Preparation for grouting:

• Cutting of strand over-length

Testing of tendon:

•All vents are clear

•Tendon is clear and propulsive

Sealing of anchorage zone:

•Secondary concrete

•Temporary grout caps

•Permanent grout caps

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