General authority dressing points from my style consultation-
Jacket/tailoring
Well chosen jewellery/accessories/glasses
If not a jacket, something with a collar eg shirt
Tidy hair (not fluffy/messy)
Lipstick if you go for make up
Block colours and element of dark/contrast
Don't wear cardigans
But also, you need to look authentic and comfortable, as far as possible, not like you've dressed up as Cruella de Vil, and about the right level of formality or slightly smarter.
I'm a civil engineer too, it's not as bad as it used to be but there are these pockets of the 1970s about.
It probably helps to wear something that makes it clear you are on the technical team, not just a smart project manager for example . Also make it clear at introductions what your role is, "I'm Shortass and I'm bridges team leader on this project, Joe and Bill here are in my team" . I wish my company did a shirt with my job title! I hope it's a ladies fit polo too. On the bottom I'd suggest navy camel or cream trousers in the shape that suits you best and smart boots or loafers. Boden /Hobbs type stretch tailored trousers, not jeans or chinos. I prefer to cover my legs up at work unless it's a heatwave.
If you get an inappropriate comment in a meeting I have a phrase "Oh dear, I think you need to go on the diversity training after that comment" said in a way that could be light-hearted. Then if they apologize you can smooth over, if they dig in "I don't bother with that rubbish" you can say, " I wasn't joking, but anyway let's move on".
I've found once people know me I get respect for technical knowledge, but it's hard with people new to the company who may have worked in different cultures.
Some people just have more natural authority than others. If you are short, feminine and have a naturally soft/dainty or young look, you may have to compensate a bit with how you present yourself at work - no harm trying.