Very few large things make it into the fossil record ( https://news.ycombinator.com/item?id=16837795 ), and a small fraction of those are discovered. It's possible, but I-beams are rare compared to plastic particles, which are basically carpeting the seabeds, rivers and beaches now.

"microplastics everywhere". http://www.bbc.co.uk/news/science-environment-43363545

"Microplastic pollution in oceans is far worse than feared, say scientists", "pervasive and persistent nature" https://www.theguardian.com/environment/2018/mar/12/micropla...

"The deep sea is a major sink for microplastic debris" http://rsos.royalsocietypublishing.org/content/royopensci/1/...

We don't know what the effect of millions of years on this debris will be, but I am suggesting that due to the fact of the human species as a geological force, most of the rocks from this era will be a bit unusual in composition.