Structural Analysis for Revit is no longer available
On 30 June, 2018, Autodesk discontinued sales and support for Structural Analysis for Revit® software.
Consider moving to Robot Structural Analysis Professional
You can get similar functionality with Robot Structural Analysis Professional, which lets you test the effects of structural loads and verify code compliance using advanced BIM (Building Information Modelling) tools. The software, which integrates with BIM workflows, is available only in the Architecture, Engineering & Construction Collection.