The bolts in question were made by an american company. The same issue happened with another bridge before. See https://news.ycombinator.com/item?id=9695276 ht

The bolts in question were made by an american company. The same issue happened with another bridge before. See https://news.ycombinator.com/item?id=9695276 https://news.ycombinator.com/item?id=9695276