Cracks in pedestrian bridge possible root of failure

Cracks found in a Florida pedestrian bridge prior to its collapse, killing six, might have indicated the upcoming failure.

A key concrete support truss in the doomed Florida International University pedestrian bridge developed worrisome cracks 10 days before the structure was lifted into place over the Tamiami Trail, photographs and an internal email unintentionally released by the school show.

The documents, released in response to public records requests from the Miami Herald, show that FIU’s construction and engineering team discovered potentially problematic cracks in the bridge earlier than officials have previously acknowledged.

Because of the ongoing investigation we do not yet how the engineering company building the bridge responded to the cracks. They might have analyzed them and dismissed them. Or the might have ignored them entirely.

Collapsed bridge did not have tower and suspension cables

The coming dark age: The Miami pedestrian bridge that collapsed yesterday only five days after installation did not have its required tower and suspension cables in place.

Engineering experts say investigators looking into the collapsed ‘instant’ bridge in Miami will want to know why a central tower which is usually built to support a suspension bridge was not in place when it collapsed onto Tamiami Trail on Thursday afternoon.

Last week, Florida International University’s official Twitter account posted a rendering of the bridge in its completed form as envisioned by the planners before its opening to foot traffic in early 2019. The rendering shows a tall central column with cables connecting it to the main span. Engineers say the design is known as a ‘cable-stayed bridge,’ which is a kind of suspension bridge, according to USA Today.

The bridge did not have the central tower in place, even though experts say it is usually placed at the early stages of construction. In the absence of a tower, there is usually a temporary support, though in this case it is unclear what the builders were using in the absence of a central structure.

I have never heard of any kind of suspension bridge ever being built in this sequence. Such bridges always install the towers and the cables, then the roadbed. Here, it increasingly looks like they put up the road bed before the tower and cables, an approach that practically guarantees the bridge will fail.

The images at the link show the presence of temporary support structures under the bridge, so it could be that the builders were using these to support the bridge until the central tower and cables could be installed. However, the bridge was made of concrete, which is far heavier and does not have the same structural strength as steel. It could be they overestimated the ability of this concrete structure to stand, without the cables.

Only five days after installation pedestrian bridge in Florida collapses

The coming dark age: Less than five days after it was installed at Florida International University a pedestrian bridge has collapsed, trapping and possibly killing an unknown number of people below it.

The story from the weekend describes the bridges construction and installation.

This is a horrible story. Does it, as does the Australian train story from yesterday, indicate a trend? Sadly, I worry that it does. For engineering to fail this badly, this quickly, indicates a level of incompetence or corruption at so many levels it is downright appalling.