Intermediate Diaphragm and Temperature Effects on Concrete Bridge Performance

A study was conducted to determine the effects of intermediate diaphragms on bridge superstructure performance, combined with actual bearing stiffness and thermal changes. Parameters studied included the presence of intermediate diaphragms, rises and drops in temperature, and increase in bearing stiffness. A finite element model of a bridge superstructure containing Florida Bulb Tee 78 girders was created using ANSYS software. This model was subjected to HL93 truck load as suggested by the AASHTO load and resistance factor design specifications. The results indicate that intermediate diaphragms have the positive effect of reducing the maximum deflections and stresses for the bridge system. The expansion of the bridge due to a positive temperature change was shown to decrease midpoint deflections, and vice versa. The combined effect of intermediate diaphragms and temperature changes increases the effect brought about by the temperature changes.