Go to Edit> Set Up> Mass Props and enter the density from the material you look up on www.matweb.com.
Maybe someday PTC will include a scraped data link from them or something but I guess they don't include a lot of default material properties for legal reasons. Like if you calculated the strength of the catwalk of the Hyatt Regency using their steel materials properties and then it wasn't exactly the same as the actual beam material used in construction then the dirty lawyers would be able to get them.
In Reply to Terry Thomas:
I would like to measure weight and other info but I do not have a database to do an anaylsis. does someone have on that they can share as well as tell me where to install it?