Performance of Concrete Bridge Deck Slabs Using Isotropic and Standard AASHTOProcedures. University-Based Research, Education, and Technology Transfer Program

摘要

Bridge decks are generally designed using the accepted practices of theconventional American Association of State Highway and Transportation officials (AASHTO) code. The current AASHTO design code, however, usually overestimates the stresses in the steel reinforcement of bridge decks; therefore, an alternate means of reducing the amount of reinforcement without sacrificing the integrity of serviceability and strength of the decks could result in considerable cost reduction and efficient solution. This reduction in steel reinforcement may be achieved by the use of isotropic decks that are designed using the empirical procedure. The fundamental concept in the isotropic deck design is based in the 'arching' effect that takes place in the concrete deck between the short spans of the beams. As a result, the steel reinforcement experiences insignificant flexural stress. The arching effect causes the deck slab to fail in punching shear rather than flexural failure, which is the basis of the design of conventional AASHTO deck slabs, therefore, shear and temperature governs the amount of reinforcement needed. To use this concept successfully in the construction of bridge decks, Pennsylvania Department of Transportation (PENNDOT) conducted an experimental demonstration project in which bridge decks were designed, and then they were evaluated over a five-year period. Evaluation of the performance of the decks is based on field monitoring reports, which give details of crack occurrence, spalling of the decks, and general condition of the bridge deck slab with actual field visit to various sites and comparing field behavior.