Not all stories follow a 3-act structure. As an example, Les Misérables is rather episodic in its nature: first there's the story of Bishop Myriel and how he meets Jean Valjean, then there's Fantine's story, then Cosette's, then we have Marius who encounters now-adult Cosette, then there are multiple climaxes.
For a film example, there's My Neighbour Totoro, which too is constructed of semi-separate episodes, rather than one overarching story.
(Some more examples include Shmuel Yosef Agnon's Only Yesterday, Boris Pasternak's Dr. Zhivago, Marion Zimmer-Bradley's Mists of Avalon, and I suppose quite a few others.)
Some "rules" are maintained even when the 3-act structure is replaced with a more episodic narrative. For example, exposition and setups are kept to approximately the first 30% of the story, while payoffs come later. In quite a few cases, though not universally, there's also rising tension: later "episodes" are tenser and with higher stakes than earlier episodes. (However, each episode would have its own denouement.)
Trouble is, the 3-act structure is very useful in terms of providing a measure of guidance to pacing: I know I should have something dramatic happen by about this point, should have a major turning point by about that point, etc.
What could guide me in similar fashion if I eschew the 3-act structure, and follow instead a more episodic path? Suppose, for the sake of the argument, that I'm trying to write Les Misérables (that's the example that I suppose would be most familiar to people)? How do I keep track of my pacing? How do I "know" when there's something wrong with the pacing and how it could be corrected? (Other than by trial and error and gut-feeling, that is?)