The six story mechanical systems frame will be concrete post and beam with diagonals for rigidity. The concrete posts and beams on the levels involving the structure of the living quarters will be detailed into the mass walls of the living quarters structure for detail/weather reasons while strucurally designed as an independent six story post and beam structure.
The angled roof cap of the six story structure will be steel "I" beam type structure simply sitting (with appropriate anchorage) on the top level of the six story concrete post and beam structure. The steel is best for this angled roof structure due to the many attachments of the mechanical system components.
Cat walks detailed out of steel will be structured in to allow maintenance access to all utility components.
All three structures will use local ( NYC) consulting structural engineers for design of the three independent but very basic structures. Wind, earthquake, and fire will all be considered in the structural design of these three independent structures.