Broken Strands
Broken Strands
(OP)
Background:
-Cast in-situ viaduct, spans ~42m
-3 webs
-6 anchorage in a web
-31 strands in an anchorage (all fixed at one end)
-Day 1, stress to 50% design stress for all anchorages
-Day 2, 5 strands in an anchorage were broken while stressing in
Any suggestions to this issue?
-Cast in-situ viaduct, spans ~42m
-3 webs
-6 anchorage in a web
-31 strands in an anchorage (all fixed at one end)
-Day 1, stress to 50% design stress for all anchorages
-Day 2, 5 strands in an anchorage were broken while stressing in
Any suggestions to this issue?





RE: Broken Strands
RE: Broken Strands
If broken then as BigH says small knicks in the wire, or even sparks/molten metal from nearby welding or gouging operations can damage the wires.
Then as also mentioned corrosion can be a serious problem, was the strand delivered in good condition, stored well and stressed immediately after installation?
If all else fails then send a sample of strand for a tensile test and check against the certificates you received.
Zambo
RE: Broken Strands
Both calcs should give similar results, if not it is likely that the ducts were damaged with consequent leaking of concrete grout into the duct, restricting the elongation of the tendons.
If this is the case stressing the cables to a predetermined elongation will overstress the tendons.
Another possibility is damaged wedges cutting into the outer strands thereby causing failure.