Is it possible to generate workload for hammerora (hammerdb for oracle) from AWR tables?
In short I would say: NO.

If you want to invest lot's of time ... you could generate SQL's and usage frequencies from awr sql history tables but the parameters will be the same for all occurences of an SQL since the bind variables are not recorded for every execution.
I am not sure about hammerora but from swingbench I know you can create your own transactions and for that you could use awr sql history as a guide on how many tx/s to generate. It still remains a synthetic load.

Smarter would be to capture the databases input from a proxy between the application server and the database. 

Oracle Replay has a price, for a reason.