Browsing by Subject "Reinforced concrete"

Now showing 1 - 3 of 3
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    Effect of Reinforcing Bar Chemical Composition on Corrosion Resistance
    (Minnesota Department of Transportation, 1994-10) Leon, Roberto T.; Jeon, Moon-Gu
    This research report looks at the chemical composition of reinforcing bars, and the sulfur content in particular, and their influences on the corrosion resistance of rebar. The research supports the original hypothesis--which suggests that the reduction in sulfur inclusions would benefit corrosion resistance. The reduction could result in significant savings that would more than offset the higher initial costs for these bars. To test the hypothesis, the study examined the corrosion resistance of four kinds of steel reinforcing bars; ordinary, low sulfur, copper and tungsten, and nickel. As in other series in the past, this research indicates conflicting results for different measurement techniques used to quantify corrosion rates. In addition, the mechanism that results in low sulfur bars showing a three-fold increase in corrosion life are not clear and need more study. The report recommends a long-term follow-up study on the use of both small cube and slab specimens in the laboratory, as well as full-scale specimens in the field.
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    Load Rating Assessment of Three Slab-Span Bridges Over Shingle Creek
    (Minnesota Department of Transportation, 2022-08) Hill, Kendall A.; Dymond, Benjamin Z.; Hedegaard, Brock D.; Linderman, Lauren E.
    Three slab-span bridges crossing Shingle Creek in Brooklyn Center, Minnesota, have poor American Association of State Highway and Transportation Officials (AASHTO) load rating factors for certain truck configurations. Characterization of load distribution is useful for determining the load rating of bridges, but results in the literature have shown that the AASHTO code results in conservative load rating factors. The focus of this study was to determine if the load rating of the three concrete slab-span bridges was conservative and could be improved using results from live load testing and finite element analysis. Field testing used a suite of instrumentation that included displacement transducers, strain gauges, accelerometers, and tiltmeters. A three-dimensional solid-element finite element model was used to determine an expected range of behaviors and corroborate the field data regarding how load distributed when placed near and away from a barrier. In addition, a method for developing a simple plate model of slab span bridges was developed considering in-situ material properties and effects of secondary elements such as barriers. Results indicated that the AASHTO load rating was conservative, and an improved rating factor could be obtained considering the field test data and computational modeling results.
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    A two-scale thermomechanical computational model for reinforced concrete frame structures
    (2014-09) DesHarnais, Marie Gisele
    A two-scale numerical model is developed to study the behavior of reinforced concrete (RC) frame structures subject to fire loading. In this model, various structural components, such as beams, columns, and beam-column joints, are modeled by elastic elements connected by a set of nonlinear cohesive elements, which represent the potential damage zones. The thermo-dependent constitutive behavior of each cohesive element is determined by nonlinear finite elements (FE) simulations of its corresponding potential damage zone under different loading modes at different temperatures, where the thermo-dependent material properties for the FE simulations are determined based on the existing literature and a set of high-temperature experiments on concrete. The proposed two-scale model is used to simulate the behavior of a RC frame subassemblage under thermomechanical loading and the simulation results are further compared with the prediction by using the conventional finite element model. It is shown that the present model can well capture the nonlinear behavior of RC frame structures under thermomechanical loading, and due to its computational efficiency, the model provides us an efficient means to investigate the global behavior of large-scale RC frame structures under fires.