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| Thread ID: 141816 | 2016-03-04 21:14:00 | Darwin Rules ! | Terry Porritt (14) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 1416927 | 2016-04-16 02:50:00 | just reading through www.beehive.govt.nz and www.beehive.govt.nz llapse%20of%20a%20Balcony%20at%20598%20Castle%20St reet,%20Dunedin.pdf a couple of quirks in the report. "Inspection and testing of the joists that failed has not identified any concerns about the standard of timber used in the construction,” Dr Smith says." but the report says "Two timber samples and a series of photos were sent to SCION Research Institute to try and identify the grading and treatment properties of the timber joists from the recovered remains of the balcony. MBIE is awaiting the results of these tests." apart from the obvious we havn't got results yet, they are not even testing the timber for strength. its a fairly poor investigation if they don't bother to do any critical material testing. its not that hard to go put one of the joists in a rig and see what weight it can handle before it breaks. tho it is good to see that they will review the standards decks are built to, after all a deck is a deck. also testing of the effect of notching. tho i would be interested in the differences in the old design (fixed notched joists) and the current design (free float non-notched joists). As a former certified mechanical tester, for heavy duty wood/corrugated board/plastics , sometimes we found the breaking strength (tensile strength) was not useful. Sometimes the strongest product, failed (or displayed visual failure), than similar products with lower breaking strength, depending what type of loads/forces it was subjected to: Sudden impact, vibration frequencies, progressive "creep" failure, lateral - flex forces, etc. It could be a bit of a challenge to asses relative strength and to outline the type of testing, and whether if need to be repetitive, cyclic, hysteresis - memory - moisture effects, and determining at what deflection-load points compared relative to final failure. Static vs Dynamic testing. I once tested a product over 5 days (flexed it 100's of times - non destructive testing) working with DSIR/IRL, Massey Uni, etc, to prove it was superior to repeated loading, but yet had relatively low tensile and tear strength against other products. One product could be weaker at certain applied forces, but much more durable to varying load types, over time before it actually breaks. Most tests start with Tensile, because it's well documented (with spec figures/Units available for many materials, and easy to set up. But not entirely meaningful... |
kahawai chaser (3545) | ||
| 1416928 | 2016-04-16 06:20:00 | absolutely. thats why i can't understand why they don't take the timber used and test that with conditions it was exposed to. eg very dry timber can have a tenancy to snap. especially with all the load going to a single point that the deck had. at the very least it would be good to simply rule out a possible material failure or a material thats changed and now out of the spec used in the design. |
tweak'e (69) | ||
| 1416929 | 2016-04-16 06:49:00 | Instead of all this attempted “buck passing”, why not just award the 16 responsible their Darwin Awards, along with the account for the repairs, and get on with life. | B.M. (505) | ||
| 1416930 | 2016-04-16 09:13:00 | blaming the students before finding out the exact cause is 'passing the buck". i don't think you guys realize how low the deck standard is. two medium to big guys standing on the deck having a beer and the misses walks over with a plate......thats actually over the spec. i'm 100kg. so two of me standing next to each other is the limit. what about two big guys at 150kg each. now they are 100kg over the spec. 100kg person walks up to them and now thats 400kg, which is the estimated weight which caused the deck failure. |
tweak'e (69) | ||
| 1416931 | 2016-04-16 20:38:00 | blaming the students before finding out the exact cause is 'passing the buck". i don't think you guys realize how low the deck standard is. two medium to big guys standing on the deck having a beer and the misses walks over with a plate......thats actually over the spec. i'm 100kg. so two of me standing next to each other is the limit. what about two big guys at 150kg each. now they are 100kg over the spec. 100kg person walks up to them and now thats 400kg, which is the estimated weight which caused the deck failure. For goodness sake, there were 16 of them jumping up and down so it’s anyone’s guess what the peak load was at any given time. As well as that there are a number of decks, exactly the same, built at the same time, in the same complex, probably from the same packet of timber, that are still standing. Now let’s give the whole sixteen of these idiots their Darwin Awards that they so richly deserve, along with the repair bill. :) |
B.M. (505) | ||
| 1416932 | 2016-04-16 22:51:00 | blaming the students before finding out the exact cause is 'passing the buck". i don't think you guys realize how low the deck standard is. two medium to big guys standing on the deck having a beer and the misses walks over with a plate......thats actually over the spec. i'm 100kg. so two of me standing next to each other is the limit. what about two big guys at 150kg each. now they are 100kg over the spec. 100kg person walks up to them and now thats 400kg, which is the estimated weight which caused the deck failure. Er, the sums are a bit out there tweak'e. The design load is 2kPa which being translated is 204 kgf/m². The balcony is 1.23m x 4m =4.9m², so design loading is 204x 4.9= 999kg. If average weight of students is 75kg that works out at 13 students, could be more or could be less. The report says there were 18. 18 students makes the balcony pretty well crammed full, which in itself should have caused a bit of concern among them except for the group dumbing down effect. BM: Whilst initial reports said there was jumping up and down, the video shows only rhythmic movement before the collapse. Though there is the report from the singer of a warm up band who said they were jumping and causing the balcony to flex up and down, and she warned the students of the danger. This was sometime before the lead band started playing and the collapse. |
Terry Porritt (14) | ||
| 1416933 | 2016-04-17 00:20:00 | BM: Whilst initial reports said there was jumping up and down, the video shows only rhythmic movement before the collapse. Though there is the report from the singer of a warm up band who said they were jumping and causing the balcony to flex up and down, and she warned the students of the danger. This was sometime before the lead band started playing and the collapse. Well it doesn’t really matter which band was playing, or what they were playing, when the damage was done. Early reports put the number on the balcony at 40 at one stage, so if that report was anywhere near correct the damage/weakening could have been done then and some other event collapsed it completely later on as you point out in your post #55. “If the balcony was already weakened because of what had gone on before then just a bit of rhythmic body movement in unison could well have been the cause. It is too much of a coincidence that it collapsed just as the band started”. Also, it is not unreasonable to think that the actual number on the deck was varying continuously as people had toilet stops and grog replenishment needs, but the bottom line is the idiots caused the problem and should be held to account. However, the chance of actually finding those that caused the problem is fairly slim, unless of course they come forward to collect their Darwin Award. :) |
B.M. (505) | ||
| 1416934 | 2016-04-17 01:15:00 | This video, www.stuff.co.nz of "Scarfies" breaking roofs and falling through, a few years earlier, perfectly illustrates how group intelligence takes a nose dive. You can hear one idiot crying out "my leg, my leg", pity it wasn't his neck :clap |
Terry Porritt (14) | ||
| 1416935 | 2016-04-17 03:43:00 | Er, the sums are a bit out there tweak'e. The design load is 2kPa which being translated is 204 kgf/m². The balcony is 1.23m x 4m =4.9m², so design loading is 204x 4.9= 999kg. you missed the bit out people standing close together. so 3 people within 1m² which is easily done. you only need two of me standing next to each other to reach the design limit of 204 kgf/m². heavier people would be over the limit. as the design is a max weight limit shouldn't they be using a max weight of a person rather than an average weight of a person? while it may sound like splitting hairs, the deck broke at one end first. it wasn't just the total weight that broke it, rather the point loading. |
tweak'e (69) | ||
| 1416936 | 2016-04-17 04:26:00 | I see your point. The lesson is that such balconies need to have a much bigger maximum design load, especially in student accommodation, so that even with crowding and jigging up and down the structure is still safe. | Terry Porritt (14) | ||
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