In the software industry, we call a step to building a software "architecture". I always take "architecture" as "structure". So for me, software architecture = software structure. Is that right?
2 the complex or carefully designed structure of something: the chemical architecture of the human brain
the conceptual structure and logical organization of a computer or computer-based system.
1 the arrangement of and relations between the parts or elements of something complex
Notice the reference to structure in the definition of architecture.
Architecture & structure mean the same in software as elsewhere -- structure is what it is (or turns out to be), architecture is what has been done to it. You may 'architect' a humanoid and it may turn out to be a frankenstein's 'structure'.
For the more domain-specific significance of structure, see Structured programming on WP.
"architecture" and "structure" are different aspects everywhere, you create architecture for the initial structure you have planned for. In software programs, Structure is how it is supposed to be written, say a class in java has a defined structure, where as 8086 micro processor has an architecture and can have different structure. Software developers uses structures to build classes, methods where as a software architect creates frameworks where these structures can be easily implemented.
There is a lot of confusion about this in the IT industry as Architecture and Structure are considered to be basically the same thing, whereas they are recognised as being very different in the Building and Construction industry. The Architecture is what you can see, feel and experience; the Structure is how the Architecture is realised and what holds it all up. Architecture is designed by an Architect, Structure is designed by an Engineer.