Fans tearing down goal posts after their team wins a football game is more likely to occur if their team wins a significant game, or they defeat an important rival institution, or snaps a losing streak of some magnitude.
An immediate consequence of Ohio State winning the national football championship in early January, 2015 was that some of its fans set nearly 90 fires in garbage cans, dumpsters, and sofas. They also tore down a goal post in Ohio Stadium. Police used tear gas and pepper spray on the unruly crowd, making several arrests in the process.
The goal post so abused was a temporary one used for high school games played in Ohio Stadium on the OSU campus.
The National Championship game itself was played earlier in Arlington, Texas; but the goal post torn down was in Columbus, Ohio. The goal posts in Texas were unmolested; but Big Ten fans are resourceful; and one goal post is just as good as another!
As to what happens to the goal posts afterward, it's hard to say. Most often they're left behind because of their weight. But one so taken down by jubilant Northwestern fans was thrown out of the stadium and then dumped into Lake Michigan!
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