A permit truck which exceeds the predefined limit of 108 kips is defined as a superload in Indiana. This study was conducted to examine the long-term effects of superload trucks on the performance of typical slab-on-girder bridges and to assess the likelihood of causing immediate damage. Typical steel and prestressed concrete slab-on-girder type bridges were analyzed using both beam line analysis and detailed finite element models. Furthermore, one prestressed concrete bridge and one steel bridge were instrumented using more than 50 sensors each. Strains and deflections were measured during a live load test, and each bridge was monitored for more than six months. Capacities of the investigated bridges were calculated and compared with the demands generated by various groupings of typical superload trucks. Analysis of the steel and prestressed concrete bridges demonstrated that typical superload trucks up to a gross vehicle weight of 500 kips are not expected to cause any damage or impair the long term performance of the investigated bridges. Serviceability limit states of the prestressed concrete bridges controlled the rating, and the bridges had adequate strength to accommodate all superloads included in the database. However, strength limit states controlled the rating of steel bridges. Long term monitoring of a continuous and a simple span bridge indicated that strains comparable to those of a 366-kip superload truck can be generated by regular truck traffic. The field measurements also demonstrated that the in-service behavior was different than the design assumptions. Fixity due to integral abutments, effectiveness of the continuity joint in continuous prestressed concrete bridges and contribution of the secondary members lead to notable differences between the expected and the anticipated behavior. Furthermore, the AASHTO girder distribution factor equation was found to be conservative for the investigated bridges. Use of a more accurate method such as FEA or the spring analogy method is recommended for the evaluation of bridges traversed by very heavy superload trucks.

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Superload, truck, fatigue, bridge, steel, concrete, girder, strain measurements, load rating, remaining life, SPR-2793

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Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, IN

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