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Post by roke on Aug 1, 2007 22:24:20 GMT -5
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Post by CentreHice on Aug 2, 2007 3:07:52 GMT -5
You just never know.....no matter who's to blame, those people are gone. What are the odds of:
1. a bridge collapsing....
and
2. when you're driving on it?
Two years ago, the top part of a big old maple tree decided to break off and fall on my car as I was driving down a country road. BANG! Right on the hood and roof. One second I see road and countryside, the next second nothing but branches and leaves. I was unhurt. $6000 damage to the car. Again, what are the odds? If I'd been driving a convertible...I likely wouldn't be typing this right now.
It's bad enough we have to put up with tailgaters, zig-zaggers, and speed demons on the road.....but bridges and overpasses (like the one in Quebec a while back) collapsing shouldn't have to be a worry.
My heart goes out to those families.
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Post by Disgruntled70sHab on Aug 2, 2007 6:42:17 GMT -5
I can't recall having any close calls like the one you had, CH. The ones I remember was when I was younger, more stupid and saw the world through a different set of eyes. Still here though.
Oddly, I only thought of this after seeing some photos of the wreckage. But, they reminded me of driving through Montreal actually. It can be pretty confusing the first time going through the city via the freeways. However, even back in the early 80's the system of overpasses and underpasses all looked pretty old. I'm not as nervous driving through Montreal as I used to be, but that freeway system still spooks me.
Was just listening on the radio and they're saying it's too early to determine just how it happened; foul play, or a structural flaw.
There's only two bridges I have to cross in order to get to work and both of them are rather small. I'd hate to have to cross a high, long bridge every day. Sort of reminds me of a few in Montreal.
Cheers.
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Post by clear observer on Aug 2, 2007 9:12:30 GMT -5
I can't recall having any close calls like the one you had, CH. The ones I remember was when I was younger, more stupid and saw the world through a different set of eyes. Still here though. Oddly, I only thought of this after I seeing some photos of the wreckage. But, they reminded me of driving through Montreal actually. It can be pretty confusing the first time going through the city via the freeways. However, even back in the early 80's the system of overpasses and underpasses all looked pretty old. I'm not as nervous driving through Montreal as I used to be, but that freeway system still spooks me. Was just listening on the radio and they're saying it's too early to determine just how it happened; foul play, or a structural flaw. There's only two bridges I have to cross in order to get to work and both of them are rather small. I'd hate to have to cross a high, long bridge every day. Sort of reminds me of a few in Montreal. Cheers. Driving through Philadelphia several years ago spooked me; the Benjamin Franklin bridge had pot-holes the size of volkwagens! |
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Post by BadCompany on Aug 2, 2007 10:09:28 GMT -5
I used to do bridge inspections...
Let's just say the only surprise I have is that it doesn't occur more often.
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Post by SiR on Aug 2, 2007 12:18:28 GMT -5
I used to do bridge inspections... Let's just say the only surprise I have is that it doesn't occur more often. Yikes. I'll never drive on a bridge again. |
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Post by clear observer on Aug 2, 2007 13:25:41 GMT -5
I used to do bridge inspections... Let's just say the only surprise I have is that it doesn't occur more often. uh...thx... ...thx alot for that |
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Post by Tattac on Aug 7, 2007 3:03:22 GMT -5
A day before this collapse we were driving across the Chesapeake Bay Bridge talking about what would happen if it collapsed under our car. Now I feel really bad about it.
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Post by Disgruntled70sHab on Aug 7, 2007 6:24:47 GMT -5
I used to do bridge inspections... Let's just say the only surprise I have is that it doesn't occur more often. This is the thing, BC. I don't know what condition the Montreal freeway system looks like today but I remember seeing large chips in the concrete on some of the supporting pillars. That still remains with me today actually. A day before this collapse we were driving across the Chesapeake Bay Bridge talking about what would happen if it collapsed under our car. Now I feel really bad about it. Good to see you checking in, tattac. When going into the States we usually take the long bridge at Hill Island (I think that's the crossing; haven't been to the States in a while). I've been alright with bridges in the past but this recent disaster concerns me. I haven't been up on it recently but I read last week about a land shift or something that had to do with this collapse. Guess we'll know the final outcome when the investigation is over. Cheers. |
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Post by Skilly on Aug 7, 2007 10:36:15 GMT -5
I thought for sure we had a thread on the bridge that collapsed last year near Montreal, but I can't find it .... I remember pposting what I thought caused it.
Well I think the same thing occurred here. Concrete just doesn't fail like that. Concrete shows signs of failing ... structural cracks, patterns of cracking, deflections, etc. With a good inspection and evaluation program (I do bridge inspection and evaluations) you can predict the life of a bridge pretty accurately and you can catch a potential problem years in advance. As an aside, engineers in Canada used to have to design a bridge to last for 50 years, with the new edition of the Canadian Bridge Code that was increased to 75 years. So bridge design engineers (ie . .. me) are on the hook for 75 years for their designs. Any design flaw found in that time span and we are liable. So, bridges are invariably over designed, especially concrete and even when concrete shows signs of weakness thats what rebar is for ... to take the stress away from concrete and produce gradual failures.
From the pictures of both these bridges, they both look like pretressed, drop panel type bridges. I believe Newfoundland only has one of them now ...... and it has been monitored extensively since the Montreal collapse. The problem with these bridges is not the concrete or even the superstruture design (to a degree) ... it is the expansion joints. These bridges are supported by a "lip" of concrete about 500 millimeters in thickness, but the way they are constructed it is hard to inspect this area of the bridge. The water/salt gets inside the expansion joints and leaches at the concrete and they fail at the lip ... which causes the entire bridge to fall in one slab (which is unusual for concrete believe it or not).
Now, speaking of close calls. I was on a bridge construction job 5 years ago. (I posted a picture one time). The bridge was build as a cantilever. Well while I was on the bridge we heard a "sonic boom". Everyone thought the bridge was going to fail, so 30 men were scurrying off the bridge as fast as they could (steel workers can certainly move fast). Well as we are all taught in high school, energy can only be released in two ways - heat and sound. When building the bridge in place, bolts are only to be hand snug (as opposed to when you build a bridge on land and launch it they can be torqued). The steel workers were torquing the bolts and after a while the strained of all the weight in cantilever built up energy that was released in a huge sonic boom. Once the steel workers started to hand tight the bolts we had no problem.
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Post by Skilly on Aug 9, 2007 10:04:24 GMT -5
From the pictures of both these bridges, they both look like pretressed, drop panel type bridges. Saw a news item on CNN yesterday where they are issuing a warning to bridge designers to take into account the extra weight of rehabs on bridges during design and evaluations. The Minneapolis bridge was not a concrete drop panel type like I thought .... from the aerial cameras of the wreckage it looks like a steel superstructure. Interesting .... I wonder when the last time the steel was visually inspected or had ultrasonic testing. |
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