A reinforced structural assembly (10) is provided including a hollow structure (12) having a cavity (14) with a hole (15). A bag (16) is inserted into the cavity using a tube (17). The bag has an end (18) with an opening (20) extending out of the cavity through the hole. A device (22) injects a structural foam (26) such as a two-part epoxy into the bag. The bag is closed and the end of the bag is inserted into the cavity. A cap (30) is installed over the hole. The foam expands to fill the cavity but is contained within the bag thereby providing localized reinforcement in the desired area. <IMAGE>