Life-cycle Fire Performance Assessment and Enhancement of Reinforced Concrete Bridges in Chloride-laden Environments
Dr. Ji Yun Lee
Dr. Xianming Shi
Bridge fires have increased in frequency with the growing use and transportation of highly flammable liquids and large-size batteries. The increasing frequency, intensity, and duration of wildfire as a result of changing climate may pose an even more serious fire threat to bridges. Furthermore, reinforced concrete (RC) bridges in coastal environments or cold climates are at the risk of chloride-induced corrosion of the reinforcing steel, which degrades their fire resistance significantly over time. In response to these needs, new materials have been introduced and utilized in bridge construction to improve the fire resistance of RC bridges. However, their time-dependent behavior under the combined effects of fire and corrosion has not been extensively studied. In addition, aleatory and epistemic uncertainties in material properties and performance assessment as well as deep uncertainties arising from climate change and the use of new materials have not been well characterized in the time-dependent performance assessment models of RC bridges.
The overarching goal of this proposed project is to assess and enhance the life-cycle fire performance of RC bridges in chloride-laden environments. Specifically, we will consider climate change impact on chloride-induced deterioration and subsequent effects on the fire performance of two types of reinforced concrete: ordinary Portland cement concrete (OPCC) and fly-ash-based geopolymer concrete (GPC). First, we will evaluate the fire performance of both reinforced OPCC and reinforced GPC through experiments and stochastically model their time-dependent fire performance in chloride-laden environments over their service lives. Then, we will quantify the life-cycle fire performance of these two types of RC bridges (i.e., OPCC and GPC) under deep uncertainties. Finally, we will develop a dynamic rolling-horizon model that can optimize the timings of implementing fire-performance-enhancing strategies. The results from this project will provide useful information on which type of RC bridge has a higher long-term fire resistance and is more robust against uncertain future and how life-cycle fire performance can be enhanced by dynamically optimized maintenance schedule.