Ji Young Choi

The objective of this study is to provide a process that can be applied in preparation for the introduction of an efficient and systematic pavement management system. This process includes features for selecting pavement segmentation (for management) and priority based on a cumulative difference approach(CDA), starting from the development of an index that reflects the pavement condition and current distribution status. For the index, which can reflect the current pavement conditions of sections to be managed, this study proposes a basic model form and establishes a simple modeling plan that uses only 3 points (maximum value, minimum value, and management standard) for typical flaws. For pavement segmentation, this study establishes a plan that uses a moving average combined with a minimum maintenance length standard to reflect existing condition distribution characteristics as much as possible. Finally, for priority, this study establishes a plan that performs selections using the averages of the index values of the sections that require maintenance, as determined via the segmentation step.

A non-destructive evaluation method is proposed to identify the sectional loss of the external tendon of prestressed concrete structures by detecting the change of the magnetic flux in the external tendon exposed to a magnetic field. The method uses a solenoid-shaped device with two coils: a primary coil for producing magnetic field and secondary coil for damage detection, wrapping the external tendon. A current applied to the primary coil in the device causes the magnetic field. Then, the change in the magnetic flux by the damage in the external tendon is detected by the variation of the voltage in the secondary coil in the device as the device moves along the tendon. An alternating current is applied to the primary coil to minimize the effect of the moving speed of the device. As a result, the damaged area can be detected with a low-level energy current. In addition, a wrapping solenoid-shaped device that is easy to disassemble and assemble was developed for in situ inspection. The measured signal from the secondary coil has a sinusoidal form with the same frequency as the applied current to the primary coil, and the peak curve of the measured signal provides enough information to detect the damage. It is shown that the proposed method can quantitatively identify one or multiple damaged-tendon locations as well as damages of at least 2 cm.

With premature deteriorations and performance limitations of hot-mix asphalt (HMA) pavements, innovative solutions are needed to enhance fatigue life or rut-resistance of HMA. Various reinforcing methods are widely utilized such as installing geogrid, geocomposite, or geomembrane layers at the bottom HMA to improve the structural integrity of HMA pavement. Such layered systems sometime improve the field performance of HMA; however, such solutions may not enhance toughness, tensile strength, or shear strength of HMA itself due to the location of interlayer systems. A new mono-strand fiber reinforcing material for HMA is proposed in this study to effectively reinforce the HMA not only at the bottom but also inner-side. Adding a small amount of fiber into HMA leads to significant increases in the phenomenological fatigue life of fiber-reinforced HMA compared to the conventional HMA, and four-point bending beam and indirect tensile tests are performed to observe the effect of fiber reinforcement.