Hi Ravichand,
You can get the data within BTadminI by using the relations from BTAdminH
By using the relation BTHeaderItemsExt of BTAdminH you would get BTItems.
Then use the relation BTOrderItemAll of BTItems to get BTAdminI or any relevant relation if required.
You can check these relations in the Tcode GENIL_MODEL_BROWSER and if you are not aware of getting the related entity from a parent entity, I would suggest you to go trough the BOL Programming Guide at this link : http://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/e0ddd4e6-32f9-2c10-9d88-d993c4b0008d?QuickLink=index&overridelayout=true
Regards
Vinod