Short answer is No. You can't do this out of the box -
See the following Oracle Support Document 1618479.1 (Limiting Number of Sessions per User ID) can be found at: https://support.oracle.com/epmos/faces/DocumentDisplay?id=1618479.1
As Joel said, I never heard anything related to that.
The authentication logic doesn't really check existing sessions as the concept of "session" itself could be quite relative and not so easy to define.
Therefore it doesn't prevent to use the same login if somebody else with that login is connected.
As a workaround to avoid people doing that you could implement a proper SSO which means users aren't going to enter login/password anymore as their session will come from the SSO (and this means you are moving the issue somewhere else asking the SSO to take care of that blocking logic).
As I already stated over on StackOverflow:
OBIEE is an analytical platform and you have to think about connections in a different way.
1.) take a step back
2.) think about what you want to do
3.) learn and comprehend how the tool works and does things
4.) decide on how you implement and control things by matching #2 and #3
Just to be clear here. The discussion continued on SO:
The problem is, that the "requirement" makes no sense whatsoever in an analytical environment since analytics is not OLTP.