AASHTO’s Load and Resistance Factor Design Specifications for Transverse Braces: Adverse Effects on Integrity and Durability of Reinforced Concrete Deck Slabs

The transverse bracing provisions (diaphragms, cross-braces, crossframes, and so on) of the 1998 AASHTO load and resistance factor design (LRFD) bridge design specifications for the design of deck-type highway bridges are examined. This examination suggests that implementation of these provisions not only will have an adverse effect on the integrity and durability of reinforced concrete deck slabs, and consequently on life-cycle bridge costs; implementation of such provisions also has the potential to affect the desirability of steel bridge construction adversely. Instead of avoiding the use of midspan braces, as implied by LRFD provisions, it is urged that midspan braces be more generally recognized as primary elements of complex superstructure structural systems and thus be sized and spaced to function not only as transverse flange braces but also integrally with concrete deck slabs to distribute vehicular loads laterally. Such a practice not only will yield more efficient higher-quality structural systems capable of functioning effectively for 100 years or more, thus doubling their presently expected lives, but it will also help extend the service lives of the more vulnerable reinforced concrete deck slabs.