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SOLUTION
1. Inaccurate tension, over-tensioning/under-tensioning
Problems include: inaccurate pressure gauge, oil pump leak, uncalibrated jack, and large reading deviations.
Solutions : 1. Calibrate the jack and pressure gauge together; recalibrate every 6 months or 200 tensioning cycles. 2. Before tensioning, vent air and check the seals; replace the oil seal immediately if there is an oil leak. 3. Strictly calculate the tension force according to the calibration curve, not based on experience.
2. Elongation value exceeds the standard (too high/too low)
Most common, most troublesome
Solution: - Clear and clean holes beforehand - Ensure straight wire strand threading, no twisting - Adjust anchor plate position to ensure alignment
>+6%: - Actual elastic modulus is too low - Loose tensioning end, wedges not properly engaged - Excessive retraction
Solution: - Calculate theoretical elongation based on measured elastic modulus - Check wedge hardness and limit plate height - Hold load for 3-5 minutes after tensioning before top anchoring
3. Wire Slippage and Breakage
Problems: Wire slippage with a "click" sound during tensioning; significant shrinkage after anchoring; even wire breakage.
Solutions:1. Wedges must be qualified and free of cracks; replace worn wedges immediately.2. Limiting plates must be supplied with the manufacturer's specifications; do not use interchangeable ones.3. Degrease and remove rust from the steel strand.4. Slow oil return; avoid sudden oil return.
4. Anchor plate cracking and concrete spalling
Anchor plate cracking and concrete spalling
Solutions: 1. Tensioning must be performed only after the concrete has reached its design strength (≥90%) and reached the required curing age. 2. Intensify the spiral reinforcement under the anchor plate to ensure bearing capacity. 3. Ensure the anchor plate is level and centered during installation, avoiding any gaps.
5. Unsynchronized Tensioning (Tensioning at Both Ends)
Unsynchronized Tensioning (Tensioning at Both Ends)
Large pressure difference between the two ends, elongation values do not match.
Solution:
1. Use hydraulic pumps and jacks of the same model and calibration.
2. Unified command, synchronous and graded pressurization.
3. Real-time communication between the two ends, unified load holding.
6. Incomplete grouting, voids, and grout leakage in the ducts
The biggest quality hazard in post-tensioning
1. Ensure accurate cement grout mixing ratio, controlling fluidity to 14-18 seconds.
2. Use vacuum-assisted grouting, with a negative pressure of -0.06 to -0.08 MPa.
3. Ensure consistent grout consistency at the outlets before sealing.
4. Arrange vent pipes and grout outlet pipes appropriately, with venting at high points.
7. Excessive retraction of steel strand
Standard retraction is generally ≤6mm
Solutions: 1. Replace with qualified clamping plates 2. Adjust the height of the limiting plate 3. Tension to the design force and then anchor with top pressure.
8. Common problems with front-mounted jacks (the 27t/30t jacks you asked about earlier)
Common problems with front-mounted jacks (the 27t/30t jacks you asked about earlier)
→ Apply anchor release agent, replace tool anchor regularly; slow oil return.
2. Insufficient tensioning stroke
→ Calculate the total elongation in advance; if insufficient, use secondary tensioning.
3. Oil leakage, lack of power
→ Replace the seal ring, clean the piston.
9. Common Safety Accidents (Must Pay Attention)
Common Safety Accidents (Must Pay Attention)
2. Steel strand rebound → Install protective barriers.
3. High-pressure oil pipe rupture → Regular inspection, do not exceed pressure limits.
4. Insufficient nighttime lighting → Blind tensioning is prohibited.
CONTACT US
Email : wangpengchao@tuoxinjs.cn
Add : No. 3, Minhe Road, Jinming Industrial Park, Nanyuan Street, Gulou District, Kaifeng City, Henan Province
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