Turn triple window into one bow window, structural concern?
I can't think of any window that offer support. The frames are typically too weak and cannot handle the weight. The common framing for a door or window has a king stud (full height), then a crippler stud (shortened to support the header), a header (similar to a beam) over the opening, and at the bottom of the opening is a single 2xx4 or 2x6 depending on the framing, and the supporting studs below it. See picture below and how it disperses the load.

So, between your 3 windows are a crippler, king, king, crippler and are there to support the structure. Hopefully, this answers your question.
FYI - What the diagram calls jack studs, I know as cripplers.