table partitions

 hi i have some partitioned tables in our database which needs to be expanded( i need to add more partitions to the table because they are rang partitions  and running out of time.)
last time i did so many object (perhaps depended objects) became invalid which caused too much trouble(many objects got invalid
and their compiling caused too much blockers in system and application's response time got extremely slow)  .i was wondering how i can do it without down time .
i was said use update indexes at end like below but this one did not worked as well.
kindly advice