its a frame
eiffel tower is a frame structure.
sheel
the Eiffel tower is a definite frame. if the tower had something over the frame it would be a mass so the Eiffel tower would never be a shell if it had the framing still inside of it.
frame structure
correct me if wrong (i havent done alot of research yet) the leaning tower of pisa doesnt have an exact structure. it was built to be straight but proboably had some faults which caused it to start leaning. designers most of thought that the lean was going to be more popular and different than a normal building so they connected wires that held and still holds up the tower today.
It is a shell because the structure is with a hallow, curved shape
A shell structure supports its self and a frame structure does not support it self.
A tent is a frame structure
frame structure
It is a shell structure so that it can hold stuff.
The cn tower is a shell structure, but it is also has materials piled up together so it is a shell structure and a mass structure.
Shell structure