#look. I reblogged this before without any commentary beyond some zip tie jokes and didn't add this then

[screambirdscreaming]

I would hesitate to assume concrete in a structural column is a facade. The point of reinforced concrete is that the steel and concrete work together in a way that makes both stronger: concrete is excellent at carrying compressive load but fails quickly under tension (you might think a column would be fine - but if the load is not perfectly balanced and vertical, there's a bending component, which causes tension in part of the column.) Steel is equally strong in tension and compression, but is prone to deforming out of shape, which makes it unable to continue supporting the load. In reinforced concrete, the steel rebar carries the tension load, while the concrete keeps the steel held in place.

However: concrete cracks. It's brittle, this is pretty unavoidable. To a certain extent, concrete cracking is normal and fine - as long as it stays put. But if the crack starts to open, you've got problems. First of all: if chunks fall off, you've lost structural material, which means you've lost strength. Second of all, if it's not holding the steel in place, you've lost strength. And third of all, cracks can let water in to corrode the steel. (Weird fact: concrete also protects steel from corrosion, somewhat, by being very alkaline. This only gets you so far, though, especially by the ocean - saltwater is crazy corrosive, even as airborne spray.)

With this in mind, the steel straps around the column are more effective than they might seem: they keep the concrete held in place, which keeps the steel held in place, which retains structural function. As a temporary fix, it's pretty good! The fact that it's been painted over like it's a permanent solution, however...... I don't like that....

For one thing, there's the question of how it cracked like that in the first place. At first glance, it looks like the crack runs vertically near one edge of the column, which is weird. But on closer look, there's diagonal cracks starting farther in on the column. Now: bear in mind i am not a structural engineer. But it looks to my inexpert eye that those cracks are consistent with a bending load on the column. If the load was purely horizontal, you'd expect cracks at 45 degrees. But the column is also under compression, which pushes the failure angle steeper. I would guess that the diagonal cracks run out to the edge of the rebar cage, and then run together vertically where the reinforcing steel ends.

That would suggest that the load being transferred to the column is much more on one side than the other, and not in a way that it's designed for. What's up with that? Was it a one-time thing or is it ongoing? Is the steel strap repair enough to handle it?

On the whole I'd say this doesn't look like it's in immediate danger of collapse. But it sure doesn't inspire confidence either.

As I gaze at the structural column in Copley Station, cracked nearly in two and held together with zip ties that have been carefully painted over to match the column underneath, I feel my soul intertwined with that of a small Italian boy of days gone by, who also stopped to look up at a large, groaning, newly painted tank full of molasses