the "compression members" - the lower outside horizontal pieces

[GoodTaste]

Does "members" mean "parts"?

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Cooper refused to supervise the construction on site, claiming ill health, and trusted Peter Szlapka, who was little more than a desk engineer. By the summer of 1907 the consequences of Cooper's design and of the lack of leadership on the site began to show up on the structure itself, especially in the "compression members" - the lower outside horizontal pieces running the length of the bridge.

Source: The Canadian Encyclopedia
https://www.thecanadianencyclopedia.ca/en/article/quebec-bridge-disaster-feature

 

[Charlie Bernstein]

In that context, members means parts.

Also, notice that compression both pressure grow out of the word press.

The compression members are usually the lowest parts of a structure. They bear the most weight and are subject to the most pressure. So they're the most likely to fail.

 

[GoesStation]

"Compression members" has a specific meaning in mechanical engineering and architecture. You can look up the term in those contexts to learn more about it.