The access logs contain the session ID as the final parameter now (this change was made sometime during 13.x, I'm not sure which version exactly).
The session ID alone cannot be used to identify someone, but if you gather them from the logs and check the CMN_SESSIONS and/or CMN_SESSION_AUDITS tables before the records are removed again, you can then perform a lookup through the USER_ID to the CMN_SEC_USERS table for the information.
There is a Log Analyzer Package that - if/when it is available (it isn't currently) - may perform this work and provide this information using this method, but the release of this is undetermined currently. You may wish to follow updates on this thread to see when an update on that can be given: Log Analyzer Package (aka Apache Tomcat Log Analysis Package)