I got an onsite interview for a structures engineer just out of college. The interview started with me presenting a short technical presentation on something I did. From there I was sat down in a room to interview one on one with who ever was interested. The first interview was basically a quiz of some basic statics problems you should have remembered from school, shear and moment diagrams free body diagrams, stuff like that. They then turned into more complicated thought experiments like how to design the optimum beam for a certain load, what material and what shape should it be, it's not so much that you get the right answer but how you got there. The interview then continued with several short, 20 min or so, one on one interviews from a bunch of different people. Everyone had their one or two trick questions to ask on everything from vibration modes to computer programming. They then asked you about your experience and what you've done in the past, pretty much whatever you put on your resume. By the end of the day you might have zero interviews or you might have 10, you interview with whoever is interested in talking to you and it takes as long as it takes, mine took over 7 hours total. In the end your exhausted but you get a very good feeling about how the company operates and if its something your interested in.