Diaphragms are approved in concrete box girder bridges to shift loads from bridge decks to bearings. The depth of diaphragms in general exceeds width by two times; they are regularly designed as deep beams. However, diaphragms might not be necessary in case bridge bearings are located directly under webs since loads in bridge decks be able to be directly transferred to bearings based on Jorg Schlaich & Hartmut Scheef in 1982. This arrangement suffers from downside that changing of bearings through future maintenance operation is additional difficult.

In fact, diaphragms also contribute to provision of tensional restraint to bridge deck.