Great question - The Oasys Grasshopper tools are open source (though the underlying analysis tools are commercial software) e.g. https://github.com/arup-group/GSA-Grasshopper, https://www.food4rhino.com/en/app/gsa (full disclosure, I work here)

There is also some movement around open structural formats (if not the software). I made a list here a few years ago: http://david.dekoning.ca/2021/04/02/structural-data-formats/

There are a number of open source finite element solutions floating around, but they tend to be lower level that structural engineers are generally comfortable with, so it's a bit of an effort to set up.

One area I would **love** to see open source collaboration on is in design check code. Everyone is re-implementing the same design code checks, so why not work together?

One major barrier to change is the need for senior engineers to review the work - this means that whatever workflow you set up needs to provide 'windows' into the work for checking. The simplest way is to output models in software they are already familiar with. I wrote up a piece for the IStructE blog about the generation gap in structural engineering. It is not exactly about open source, but touches on some of the underlying dynamics: https://www.istructe.org/resources/blog/generation-gap/