I am trying to design a steel structure frame, like this:

steel structure frame

Obviously, I can model individual beams of different length and arange them, however, it feels like there should be an easier way.

My second attempt was to use a curve and extrude along path (as in Extrude along path), which works well, except that a curve can not have a three-junction, and corners look weird: enter image description here

Is there some way to get this right? Maybe a special form of the wireframe modifier, which allows me to give a bevel object, just as I do with the curve?