Structure is the way a work of literature is organized and its relationship to the moral of the story.
The structure of "The Story of an Hour" changes as does the mood of the recently widowed wife, Louise Mallard. The paragraphs are at first short and quick, not too much detail or depth. The paragraphs resemble the way Louise has felt her life has been lived. She hasn't fully lived life, ergo the empty and short paragraphs.
Once Louise looks out that window and sees a whole life ahead of herself, the structure changes. To mirror the mood of Louise, the paragraphs pick up speed and depth ,"She said it over under her breath: 'free, free, free!'". This is also the first time there is dialogue in the story. With freedom finally given to her, Louise is able to speak.