Typical for the media. They rarely understand that in professional context, a term will often have a very specific meaning.

In this case, a structural deficiency identified on a report does not necessarily rise to the status of hazardous. If it does, the reporting engineer will have a special category for that condition, for example, he might say "hazardous". If he does not, he means "something that does not present imminent danger to life, limb, or property but must get fixed before it gets worse."

In New York City, if you live in a building more than 6 stories tall, your building probably has structural deficiencies on record and with luck they are called "SWARMPs"- Safe With A Repair and Maintenance Program".

The DOB will not condemn your building because it has a crack in the wall.

Same with bridges.

So what we want to know, then, is what the media has not told us: How were these structural deficiencies in the bridge described on the report, and were terms like "UNSAFE" or "HAZARDOUS" used?

Ben
Who makes a pretty decent living off structural deficiencies.

Mary asks:

I was wondering if there's any code that engineers use to tell the difference between a structure that's currently in danger of imminent catastrophic collapse, as the Pulaski is, from the ones that are just unsafe or "structurally deficient." Is "hazardous" the worst of the worst?

Ben:

It's the worst "official" comment, although one might consider it even worse if even a structural engineer is afraid to approach it.

How they tell: Physical examination and math. All structural "elements", beams, columns, cables, whatever, have a known strength based on their cross sectional area and the known physical properties of the material. Engineers examine to see what percent of the original structure is left, and recalculate from that. Structures are built with a big safety margin on the assumption that some of the strength will be lost over time, so just because a big beam has lost some of its meat to corrosion does not mean it will fail.

The most likely point of failure is always the connection.

We have a completely unofficial, discussed around the lunch table consensus on the most probably cause for the bridge collapse: Jack hammering of concrete in the sections under repair transmitted vibrations, causing overly brittle welds to crack.

Brittle welds are a recurring issue. They sunk the Titanic.

Ben