Wrong kind of material parameter when exporting from Revit to FEM-Design

I have a structural material assigned to an element but I cannot export it due to Lack of structural material assign to an element.

UPDATE: September 10th 2014
When using Revit StruXML Add-In in version 1.1.002, structural material for Beams, Columns, Isolated foundations can be both Instance and Type parameter.
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The reason user may receive the warning about a missing material, even though the element has a material assigned to it, is a wrong kind of Structural Material parameter. 

Structural material has to be an Instance parameter in case of:

• Beams,
• Columns,
• Isolated foundations,

and a Type parameter in case of:

• Floors,
• Walls,
• Wall foundations
• and Foundation Slabs. 

Example:

Structural Material of a column is a Type parameter -  this column will not be exported due to lack of material that cannot be recognized.

The solution is to edit the column family and change the parameter from Type to Instance. Follow the steps:

• select the physical column, 
• chose Edit Family button,

• chose Family Types button: 

• select the Structural Material parameter,
• press Modify button, 
• chose Instance parameter, 
• Ok, 
• Ok,

• press Load into Project and select the desired project. 

• chose to overwrite the elements and its parameters.

The Structural Material will appear as an Instance parameter: