This has been kind of a common question for some time, even today when Advance Steel is considered to be as known of an application as Revit itself, there's still several who are uncertain about Advance Steel role in the world of structural design, since Revit Structure is actually regarded as quite a complete solution already.

Perhaps for those already proficient in Revit Structure there's really not much of an argument, as they can probably move around the tools for getting whatever suit their needs. But for those relatively new to these 2 applications or even intermediate users, the scene can be somehow confusing, specially when mixed with structural analysis software.

And indeed here's where the first clarification should be made. Not Revit Structure nor Advance Steel are considered to be structural analysis applications. So while you can assign load cases to an Analytical Model, you can't in fact perform an actual analysis of a structure (or its connections for that matter) under different loads and stresses. At least not directly within the software tools, as there's actually a cloud solution for Static Analysis, but nothing we can compare with specialized applications.

You can however design the structure and its details from the data provided through a previous, or perhaps subsequent, structural analysis performed by a third party application (SAP, STAAD Pro or Autodesk RSA).

Now the second, and perhaps more obvious, difference is that Advance Steel greatly focuses on the designing, detailing and documenting of steel connections, providing flexible, precise and powerful tools, thus making this particular task way more efficient than in Revit Structure. Plus Advance Steel works over AutoCAD's interface giving it a nice touch in the realm of flexibility

But again and for those more knowledgeable of Revit Structure, the latest versions now provide enough support for the designing of steel connections for making this gain in efficiency somehow questionable.

So where's the edge in Advance Steel exactly?

Remember when we mentioned "precise"? While Revit Structure does provide families of connections, it has nothing to say in regard if the chosen design is or not appropriate for creating the connection between 2 or more members.

Advance Steel has two main ways of helping with this; first the design of the connections doesn't depend on a family particular set of parameters (in spite of these being 100% editable), but on the chosen members particular type of profile, so Advance Steel does suggest an overall design. And second, and perhaps most importantly, the Verification of the Connections based upon the actual internal forces resultant of the diverse loads and stresses to which the structure is being subjected.

This is perhaps one of the most, if not the most relevant aspect of Advance Steel as a structural design software. But if Advance Steel isn't a Structural Analysis software, how is this performed?

When we say "verification" it simply means that the connection's design will be verified based on the required (provided) internal forces; shear, bending moment and axial force. And not necessarily that these data will be generated by the program itself, software like Autodesk RSA (Robot Structural Analysis Professional) or CSI SAP2000 could work for this purpose.

So once a design is proposed Advance Steel will look at the provided information (internal forces) and perform the proper verification. This by itself isn't a small deal! As it will greatly help in obtaining reliable connections between all the members in the structure.

Aside from this though, there's other options within Advance Steel which focuses more on productivity, as the Drawing Style Manager and some other documenting tools.

This of course doesn't signify that Advance Steel is a replacement for Revit Structure, as this last still provides way more design flexibility, specially if you work with Reinforced Concrete structures, but that you should see it as it was meant to, one of the most efficient tools for the designing and detailing of steel structures and their connections. And at the very least, a solid extra tool for every structural engineer.

You may find further information about Advance Steel and Revit Structure in both this an the respective official websites.