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It is important to draw a distinction between problems that need attention, and problems that may indicate imminent structural failure.

Another engineer brought my attention to this. I thought it was unusual but he said.

Your picture South Bridge16 is very concerning to me. Where did you take that picture. It appears as thought the bearing that allows the bridge to thermally expand/contract has been replaced by a few boards? These bearings allow the steel to expand and contract and reduce stress in the bridge. If they are locked solid or do not function, you could see some very high local stresses in the bridge that were not designed for. That scares me a lot more than the number of vehicles that cross the bridge every day.

So last night I went down to the base of the bridge and took more pictures and found Eight (8) places where the bearing has been removed and steel plates put in their place. Can I bother you two to give me a quick opinion on this. All of a sudden the thruway authority is all over these bridges inspecting them. I will be curious as to their findings.

More pics here.

Actually, that is not at all unusual. As I have mentioned several times, EVERY bridge I have ever inspected (or supervised the inspection of) has expansion joints that don’t work or don’t work well. That alone is not the reason for the failure. It may have contributed to the failure (the straw that broke the bridges back), but it did not do it alone.

There have been many attempts to design expansion joints that work, but to my knowledge, none have succeeded. What he sees there is not “boards”. They would crush in an instant. It looks from the photos that they are stainless-steel sliding plates (they don’t rust very fast and allow movement longer).

The oldest expansion joints I have seen are rockers on really OLD bridges. They were heavy, expensive, cast steel sections of a wheel. Later, they cut down the rockers to just a small part of a very large circle. The problems with both of these is that they concentrate the load in a VERY small area. This area deforms plastically and doesn’t move after that.

Then they went to steel on steel flat-plates. They spread the load out further so the load per square inch was less. However, it rusted, even those that were galvanized. Next came the same thing in stainless steel. These last longer without rusting. There have been several attempts to use Teflon or other plastics, but the loads are too high — they extrude out too quickly.

The latest I have seen is a wideflange beam in the weak direction inside a corrugated metal tube to allow flex. I don’t know how they will do in the future, but nothing has worked very well so far.

The bearing plates aren’t that scary. Like Jim says, where can they go?

That concrete scares me.

The only thing holding that pier together is the rebar inside. Or the steel beam inside.

The concrete is effectively shattered.

The steel is inside where we can’t see it.

But we know what’s happening to it.

It’s rusting and the rust is running out the cracks and down the outside of the pier.

How much steel is left?

That pier is supporting two spans of bridge.

The shattered concrete atop that pier is holding nothing.

The steel inside is all that’s holding up those spans.

How much steel is left?