I always think that we can use "v-ing" to combine two phrases when two interconnected activities are going on.
For example : In sentence two, "explainig situation" and "having a hard time" is a interconnected activiy, happining at the same time. So I can combine "explaining situation" with my main clause "have trouble".
Is there some kind of special name for this usage? What is the logic behind that usage? It is like reduced adverbial clauses but I know it isn't.
1- I still have trouble expressing myself.
2- She had a hard time explaining the situation.
3- I always feel comfortable doing research there.
4- People sometimes have problems reading my writing.