Anchorage Component Mismatch and Abnormal Wedge Pull-In
During post-tensioning of a 20 m span transfer girder, the inspector notices that one 12-strand tendon using 15.2 mm strand takes 12 mm of wedge pull-in at the live end, while the other five tendons take 5-6 mm. The tendon is specified as a 15.2 mm system, but the wedge marks on the strand are shallower and the anchor head has a different stamp than the approved submittal. The supplier says the wedges are 'equivalent' and provides a catalog page without a system certificate. The stressing gauge read 2,344 kN, matching the specified 0.75fpu force for 12 strands; elongation was 2% low. No strand fracture has occurred, but the tendon is holding at load. The tendon has not been grouted.
1. Is the 12 mm pull-in a normal seating allowance? What does the wedge marking pattern suggest?
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Typical wedge seating pull-in for a 15.2 mm strand is on the order of 5-6 mm, so 12 mm is roughly double the other tendons and indicates slip or incorrect wedge/strand engagement, not normal seating. The shallower wedge marks suggest the wedges did not bite as expected, and the different anchor-head stamp indicates a component that is not the approved system. Post-tensioning anchorage behavior depends on the matched strand, wedge, anchor head, and bearing plate. A catalog page claiming equivalence is not a system qualification or an approved substitution. The low elongation (2%) is within a typical ±5% band, but elongation is not sufficient to accept an anchorage with abnormal pull-in. The tendon should not be grouted or locked off as accepted.
2. What traceability and acceptance requirements apply to the anchorage system?
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The approved submittal should identify the complete anchorage system, including strand type, wedge, anchor head, bearing plate, and supplier, with qualification test data for the system. Each component should be traceable to the approved system and to the heat/lot. Field acceptance includes verifying the stamp, checking that wedges match the strand diameter, confirming the installation orientation, and comparing elongation and pull-in with the approved system. Substitutions require engineer approval and, where required, system qualification testing. The inspector should compare the delivered components with the approved submittal, not with a generic catalog description. Missing system certification and mismatched stamps are nonconformances even if the tendon is holding load.
3. What immediate action is appropriate?
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Stop stressing on that tendon and do not grout. If it is safe to do so under the engineer's direction, de-tension the tendon slowly and replace the unapproved wedges/anchor with the specified matched system. Inspect the strand for notch marks, flattening, or broken wires; replace any damaged strand. Re-stress with a calibrated gauge, measure elongation and pull-in, and compare with the approved system. If de-tensioning is not safe because of the structure's condition, the engineer must evaluate the temporary condition and approve a controlled procedure. Issue an NCR, quarantine the nonconforming components, and verify other tendons for the same stamp. Acceptance of the tendon requires the engineer's review, not just a satisfactory gauge reading.