Autodesk Developer Network 2011
Autodesk
Updates to Revit Structure API
§AnalyticalModel now derived from Element, not IDisposable
§AnalyticalModel object is DB resident
§Analytical model curve only included in AnalyticalModel instance
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§New RebarHostData methods
§GetExposedFaces()
§GetCommonCoverType()
§GetRebarsInHost(), GetAreaReinforcementsInHost(), GetPathReinforcementsInHost()
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§NewBeamSystem() now requires Level or SketchPlane argument
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§NewTruss() requires SketchPlane input
Because of the split between the analytical model and physical model of structural components in RST product,
one impact on API is that the AnalyticalModel object is now a database resident. It is now derived from Element class, instead of IDisposble interface. The methods and properties of class AnalyticalModel are not changed, so in existing add-ins are unaffected.

Another impact is that the Analytical model curve is only included in AnalyticalModel instance. In previous versions, the analytical curves was included in both the Geometry property and the AnalyticalModel instance. If your code reads analytical curve from the Geometry property, you would have to update it to read analytical curve from the analytical model.

RebarHostData contains more powerful APIs. Calling GetExposedFace method you can get all faces that have an associated CoverType, and GetCommonCoverType method gets the common CoverType of the host.
GetRebarsInHost method can return all rebars in the host structural component. GetAreaReinforcementsInHost and GetPathReinforcementsInHost can return area reinforcement and path reinforcement data respectively.

The family of NewBeamSystem() methods has changed. Previously curves could be input without a sketch plane or level as input, and the orientation of the active view would determine the orientation of the resultant beam system. Now, there are overloads accepting either the sketch plane or the level and those inputs are required. The overloads of NewBeamSystem() now check that the input profile curves lie properly in the sketch plane or level. They also check to ensure that the profile forms a closed loop.

The SketchPlane input for NewTruss() method is now required. Previously null could be input, and the orientation of the active view would determine the orientation of the resultant truss.