Structural Modeling Components are disabled by default. You can enable it by following ways:

1. Launch OpenPlant Project Administrator
2. Select OpenPlant Modeler in Workset node.
3. Go to Properties pane and check the check box for Enable Structural Modeling Components
4. Save
   

You can also enable it through Modeler.cfg.

1. Open Modeler.cfg file. For example, for Imperial Workset it is located at "C:\ProgramData\Bentley\OpenPlant CONNECT Edition\Configuration\WorkSpaces\OpenPlantExample\WorkSets\Imperial\Standards\OpenPlant\Modeler"
2. Set OPM_ENABLE_SMC =1