I'm not a structural engineer, but I've put in quite a few bridges, and 174' is a long single span. It looks like the ties to the pier column were essential to the integrity of the bridge. As humpy said, I would imagine they needed supports below it. I'd be interested in seeing exactly how it was setup.
This failure will have been caused by an error chain. A series of semi related events that if a single one was interrupted would have prevented the failure.
An example of this was he Hyatt Regency Skywalk Collapse in 1981. The hotel added a suspended skywalk on the 4th and 2nd floors that were directly above each other. During a party with many people on each skywalk the structure failed and the top skywalk collapsed onto the lower skywalk and then into the floor killing 114 people.
The investigation found the following:
- The design called for steel rods to be threaded from the ceiling down through each skywalk where a nut and washer would support each load
- The design was later shown to only provide about 60% of the capability building codes required.
- This design was too challenging for the contractor to build so they modified it. The modification resulted in the upper washer and nut supporting the weight of both skywalks.
- The design and construction also put most of the weight on a weld.
- These changes reduced the load capacity of the skywalk to just bit more than it’s own weight.
- The contractor did not relay this change to the engineering firm. Nor did the engineering firm check on the construction.
If any of those links had been broken there would have been no collapse.
This bridge collapse will almost certainly follow the same pattern as do all engineering and construction failures.
- If the engineer had a design that was able to be built it wouldn’t have failed
- If the design was up to code it likely would have had enough margin to survive even with the construction modification
- If the contractor had been able to build it as designed it wouldn’t have failed
- If the contractor had discussed the changes with the engineering firm the flaw would have been caught.
In hindsight the links are easy to see. At the time they happen not so much.
This failure will have been caused by an error chain. A series of semi related events that if a single one was interrupted would have prevented the failure.
An example of this was he Hyatt Regency Skywalk Collapse in 1981. The hotel added a suspended skywalk on the 4th and 2nd floors that were directly above each other. During a party with many people on each skywalk the structure failed and the top skywalk collapsed onto the lower skywalk and then into the floor killing 114 people.
The investigation found the following:
- The design called for steel rods to be threaded from the ceiling down through each skywalk where a nut and washer would support each load
- The design was later shown to only provide about 60% of the capability building codes required.
- This design was too challenging for the contractor to build so they modified it. The modification resulted in the upper washer and nut supporting the weight of both skywalks.
- The design and construction also put most of the weight on a weld.
- These changes reduced the load capacity of the skywalk to just bit more than it’s own weight.
- The contractor did not relay this change to the engineering firm. Nor did the engineering firm check on the construction.
If any of those links had been broken there would have been no collapse.
This bridge collapse will almost certainly follow the same pattern as do all engineering and construction failures.
- If the engineer had a design that was able to be built it wouldn’t have failed
- If the design was up to code it likely would have had enough margin to survive even with the construction modification
- If the contractor had been able to build it as designed it wouldn’t have failed
- If the contractor had discussed the changes with the engineering firm the flaw would have been caught.
In hindsight the links are easy to see. At the time they happen not so much.
I could be wrong, but I don't think most (here at least) are criticizing the modular construction, more that it looks like parts just weren't included, specifically the primary support rigging infrastructure. I can imagine it wasn't included because of a) cost, or b) what looks like a turn lane underneath the bridge, as seen here:
You should love it, it’s what hannity does when he connects Hillary to Russians and then you spew it here.
Here in FL DOT uses a lot of preformed spans, however, they all have support ribbing along the bottom which this structure is completely devoid of.
Generally ABC is actually much more expensive in real dollars. It is "cheaper" because it causes much less disruption to the roadway. States calculate a cost associated with added traffic delays, and damage done to detour routes, it is "soft costs" that generally make ABC a viable construction method. There are definitely much cheaper ways to build a two span, 300 foot pedestrian bridge than what they were doing there, but those would've likely resulted in the road being closed and or at least taken down to half its normal lanes for extended periods of time.
That doesn't make sense, you don't test bridges by dropping things on them from a crane, and you sure as hell don't do that with an open roadway underneath. Impact loads can be massive and are very heard to calculate, the only thing you test with impact load are impact failure cases, which isn't done on real world bridges. Seems much more likely that a piece of equipment was dropped onto the bridge on accident, which may have coincided with them doing some other type of test or inspection on the bridge.
Other people are implying that corners were being cut to save money with ABC. That wasn't directed at you.
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