A CASE STUDY OF CONCRETE DECK BEHAVIOR IN A FOUR-SPAN PRESTRESSED GIRDER BRIDGE: CORRELATION OF FIELD TESTS AND NUMERICAL RESULTS. FINAL REPORT

Cracking at the top of bridge decks exposes the top mat of reinforcing bars to chloride attack, which is a major cause of the deterioration of bridge decks. The top mat of reinforcement is required by the current AASHTO design code, in which the influence of girder flexibility on deck behavior is not considered. However, it has been observed that girder deflection reduces the tensile stresses developed at the top of bridge decks. As a result, the need for top reinforcing bars is questionable. To explore the possibility of eliminating top reinforcing bars and, thereby, reducing the vulnerability to deterioration, the behavior of a four-span highway bridge is being investigated. In the four-span bridge deck studied, one span has an experimental deck which has no top reinforcement, while the remainder has both top and bottom reinforcement, which conforms to AASHTO Specifications and serves as a control. The response of the bridge deck under a test truck, which was 47% heavier than a standard HS20 truck, was monitored with imbedded strain gages. It was found that the peak transverse tensile strains developed at the top of the deck were less than 30% of the cracking strain. The behavior of the bridge deck under the test truck has also been analyzed with the finite element method. The numerical results correlate well with the test results. The response of the deck under general truck loads has been analyzed with the validated numerical model, and the numerical results show that the tensile stresses developed at the top of the deck always tend to be much less than the modulus of rupture of the deck concrete. This study confirms the feasibility of eliminating most of the top reinforcement in bridge decks.