Here is a section view of a sample and I indicated the connection
What type of connection elements are used there? Anything
related will be helpful.
From the title of your question I guess you assume the bolted element is a HPC rotor, and you might be wondering why a rotor would be bolted to a stationary element, the fan frame.
In effect, this question is related to In a turbofan what holds the spinning axis?. This question has an excellent answer that closely relates to this question (but isn't a duplicate). The following figure is re-posted for a relevant answer. Credits go to user mins.
HP rotors of CFM56-7B. Adapted from CFM56-7B Familiarization Manual
This answer hints to ...