Hello, I've been trying to analyse some sentences pattern wich have catenative verbs in them.

I.e. "The president declined signing the biodiversity act"

I don't think I'm wrong about this type of analysis and I see it from 2 different approaches:
1. "The president" Subject
"Declined" Verb, transitive
"Signing the biodiversity act" Object, direct (as a non-finite clause)
2. "The president" Subject
"Declined signing" Verb, catenative, complex (with more than 1 full verb), tran
"The biodiversity act" Object, direct.

First of all, I would like you to tell me if this analysis is correct. If so, then I have problems with sentences like the following:

"They helped us to move the piano"

The subject is obvious, but then, considering both of the latter approaches, how do I analyse it? is "us" the indirect object? can I consider "helped to move" as a catenative verb phrase, which has been split.
From another point of view, this time not considering the verb phrase as catenative, is it right to say that "us to move the piano" is the direct object with the form of a to infinitive clause?

Please help me