18-02

Bridges are critical structures, serving an important function that is vital to the safe and economical conveyance of people and goods throughout Georgia. They are designed with specifications to carry loads including their self-weight and a design vehicle load, among others, when they are in service. Satisfying all design specifications is crucial to the structure’s strength, stiffness, stability, and durability throughout its lifetime. In addition to the in-service dead and live load conditions, bridges are also designed to accommodate various loading conditions during the construction process. In some cases, these construction load and associated stability requirements are the governing load conditions for some of the bridges’ components. Georgia Department of Transportation (GDOT) has recently allowed the substitution of steel diaphragms for concrete diaphragms in its bridges. This substitution is gaining popularity among contractors for its ease of construction and subsequent reduction of cost. Currently, there is no standardized design for GDOT steel diaphragms, and contractors are allowed to produce their own designs based on loading scenarios currently specified in the 2018 GDOT Bridge and Structures Design Manual. These scenarios include full long-term wind loadings and are thought to be overly conservative because the actual loads to which the bridges are subjected during the construction process are poorly understood. This project seeks to provide the data and recommendations for a more efficient, yet safe, steel diaphragm design. Specifically, this project will (1) observe and measure GDOT construction practices through visual observations by experts and by electronic sensors, (2) quantify the effects of the construction practices in terms of loadings via observations and computational models, (3) assess the overall impact of construction load variations on bridge designs, and (4) make recommendations to GDOT for loading specifications and for a standardized steel diaphragm design.