I was in a group line once, and the guy in front of me said "drain" just as I saw it, seemingly under my front wheel.
It was the wide slot type that will never go out of vogue here. Somehow, my front wheel rode the iron, but not the back.
Like one of DD's employer's anchors, it dropped, I stopped. Scratch one rear wheel, probably a Matrix, on my Trek 510.
One of my friends, who's forgotten more about bikes than I'll ever know, took me to his house,
and we laced in a Weinman concave. I still have flashbacks of that whenever I see one of those grates.
Since then, I've never ridden the concrete edge, always the asphalt road portion.
I'm glad you're somewhat all right, and the frame's not toast. It seems they could have angled those slots.