Can CI deals with Condition1 AND (Cdt3 OR Cdt3)

Hello CIers
When I tried to use AR to deal with complex queries(e.g. condition 1 AND ( condition 2 OR condition 3 ) ), it failed;
cuz CI ended up with query: condition 1 AND condition 2 OR condition 3...
So, I tried to use my customed query;
My question: Is there any way for AR to do query -> condition 1 AND ( condition 2 OR condition 3 );

THX