Complex sentence: A large plaster version was placed on the top of the Arc de Triomphe from 1882 to 1986 until it crumbled and a version in bronze which could have endured exposure to the elements was never commissioned.
Split into simpler sentences: A large plaster version was placed on the top of the Arc de Triomphe from 1882 to 1986 until it crumbled. Sadly a version in bronze, which could have endured exposure to the elements, was never commissioned.