we have some .mxd file and want to open in AECOsim. please advise.
No we cannot directly open .mxd files in AECOsim (or MicroStation). We can open ESRI shapefiles and numerous other geographic formats.
For more specialist answers please ask about this in the Bentley Map | OpenCities Map forum.
This Bentley Communities search links to previous questions on this topic.
This third-party webpage has some general information about .mxd files that may be useful.
Marc