DETERMINING TRANSVERSE DESIGN FORCES FOR A NEXT-D BRIDGE USING 3D FINITE ELEMENT MODELING

This thesis looks into the use of 3D Finite Element Modeling to determine the transverse design forces for short-span bridges built using the Northeast Extreme Tee with integral deck (NEXT-D) beam. Models were built using either solid elements or shell elements to represent the bridge deck, and the results were compared. The stiffness of the shear keys were taken into account during the modeling process. Results were compared to the AASHTO strip width method for design bridge decks, and the results showed that the strip width method would not be adequate for the design of NEXT-D bridges, so specific live and dead load demands were recommended for the design of short-span NEXT-D bridges

Refractory corrosion by slag under an applied voltage

The effect of an applied voltage on the dissolution rate of MgO refractory in two steelmaking type slags has been investigated. It was found that the MgO corrosion in a CaO-SiO2-Al2O3 based slag proved insensitive to an applied voltage over the voltage range –0.5 to 0.3V. The corrosion rate of the dense MgO in a CaO-SiO2-Fe2O3-FeO-MgO slag showed a maximum corrosion rate at –0.45V. This effect has been explained by considering the consequences of an applied voltage on the rate of Marangoni flow at the slag-refractory-gas interface and in turn, the flow effect on the rate of the mass transfer controlled MgO dissolution reaction

The effects of an applied voltage on the corrosion characteristics of dense MgO

In a recent investigation Mills and Riaz [1] showed that industrial oxide refractory corrosion by liquid oxides could be changed by the application of a small voltage across the liquid oxide-refractory interface. They ex-plained their result in terms of penetration of the refractory pores with liquid oxide. Their analysis of the corrosion effect was to some degree limited by the use of an industrial refractory material in the study. Fur-ther, it was not clear whether their findings were limited to solely industrial refractories or had wider ranging application to more dense ceramic type solid oxide systems. In this study, a simpler and more easily charac-terized solid oxide (dense MgO) has been used to examine the effects of an applied voltage on the solid ox-ide in a liquid oxide melt. The dissolution rate of an MgO ceramic in a CaO-SiO2-Al2O3 and CaO-SiO2- Fe2O3-FeO-MgO liquid oxide composition at various applied voltages has been measured at 1540°C. It was found that the MgO corrosion in the CaO-SiO2-Al2O3 system was insensitive to an applied voltage over the voltage range –0.5 to 0.3 V. In the CaO-SiO2-Fe2O3-FeO-MgO liquid oxide system the MgO corrosion rate showed a maximum at –0.45 V. This effect has been explained by considering the consequences of an ap-plied voltage on the rate of Marangoni flow at the liquid oxide-refractory-gas interface and in turn, the flow effect on the rate of the mass transfer controlled MgO dissolution reaction