..and filed in the travel section, which says something.
It's a shame from the reaction, comment threads and elsewhere, that plenty of people evidently never heard about this when it happened, and it's only now that a new wave of the same questions are being asked all over again.
I guess that's a consequence of the lack of coverage until someone's unexpectedly turned up with a video that can be used to shock people.
DOC has finally responded to my OIA request after I poked them again. The request for photos was really overtaken by events given we've already seen that video, but they also helpfully sent me this report which I hadn't previously seen in media:
https://drive.google.com/file/d/0B3dCYSB9HiWPWVJ3S3dVWkpIUkRyVjdKNXRsNm9YY3JWcTE4/view?usp=sharing
Note that this was authored prior to DOC's later media release of 24-sep, which labelled the issue as quench cracks and embrittlement.
Notable things:
* The bridge was built by the 2nd Engineer Regiment of the NZ Army to a DOC design. Building Consent and a Code Compliance Certificate were issued by the Wairoa District Council.
* All materials were sourced new.
* The bridge was upgraded in 1999 to increase its load capacity to '10 person'. The upgrade was designed by a consulting engineer and fully consented by the Wairoa District Council.
* The bridge was inspected by DOC asset inspectors every two years and a Chartered Professional Engineer every 6 years since building.
* It's been load tested to its full design load capacity twice since being built. Most recently in 2009, tested to 2.5 tonne and well in excess of the normal service loading.
* There was "no evidence that this failure was about to occur that could have been observed during inspections or load tests".
* The immediately noted cause of failure was "a broken 24mm diameter link in a length of premium quality high-strength heat treated chain connecting the downstream main cable to the ground anchor rod."
* The chain was stripped of its anticorrosian Densotape coating, and initial visual inspections showed no significant rust or deterioration.
* DoC didn't see evidence that closure of other bridges was required, but had intended to complete load testing of the remaining nine bridges on that Great Walk by 21st September.
* A further contractor visit will be removing the chains, installing new cable strops in their place, and from there the bridge can be thoroughly re-inspected, repaired, load-tested and recommissioned.
@izogi
Bloody well done mate - and very interesting. Confirms our earlier speculation that it was probably a manufacturing defect.
This post has been edited by the author on 15 October 2015 at 16:09.
Thanks. Would you have any thoughts on the apparent plan to replace the chains with new cable-strops and then re-commission the bridge?
I can't imagine it being done if it weren't thought to be safe, but it seems a bit weird to me. I'd have thought some of the other components might have been put under unexpected stress from this mishap.
No I don't think so. That is the beauty of wire rope is that being so flexible it is very unlikely to have been damaged - and if it were - there would be immediately visible broken, abraded, kinked strands and the like.
Or to put is another way, the failure modes of wire rope is either repetitive bending fatigue, which is not applicable here - OR tensile stress beyond it's rated limit, which is not likely the case either.
http://products.asminternational.org/fach/data/fullDisplay.do%3Fdatabase%3Dfaco%26record%3D1779%26trim%3Dfalse
This post has been edited by the author on 15 October 2015 at 16:08.
@izogi, cheers for the report.
Very interesting. Thanks.
Here is the StreetView rendition of the pre-collapse Hopuruahine Bridge, which gives a good view of the sort of river underneath as well as the bridge construction. I guess they were fortunate that they landed in the water and that it wasn't in flood!
https://goo.gl/maps/h6U5HEvRs2o
Also, maybe we can make it break again if we cross it enough times.
