QUESTION: Where is the LBC default library located?
ANSWER: When working in OpenBridge Designer (OBD) the default library for LEAP Bridge Concrete (LBC) is located in corresponding to the version you are using. For example, for OBD 10.12.1.73 the "default.lbclib" is located in "C:\ProgramData\Bentley\LEAP Bridge Concrete OBD 10.12.01\Lib" folder.
Please, note that the library should be at the ProgramData, and not at the Program files. Moreover, usually, the ProgramData is a hidden folder. So, make sure to select the right one checking the name and the version.