Ph.D. Final Defense – Ernesto Pérez-Claros

Innovative Reinforcement in Structural Transportation Elements to Improve Their Capacity, Durability, and Resilience

Advisor: Professor Bassem Andrawes

Abstract

The long-term operability of reinforced concrete (RC) transportation infrastructure depends largely on the ability of structural components to resist deterioration mechanisms and withstand severe environmental conditions and increasing live loads. Reinforcement systems play a crucial role in achieving these objectives; however, conventional approaches have limitations that can compromise structural integrity and create challenges for construction, maintenance, and rehabilitation. In response to these limitations, innovative reinforcement technologies have emerged as potential solutions for enhancing the performance of concrete members. Among these, textured epoxy-coated (TEC) reinforcing bars and shape memory alloys (SMAs) offer opportunities to improve bond characteristics, control the development of cracks, and introduce localized prestressing forces. To further understand these technologies, this doctoral research investigates their structural behavior and practical applicability through a series of six experimental studies involving RC bridge decks, prestressed concrete railroad crossties, and RC columns. Specifically, the studies examine bond properties and transverse crack control in bridge decks, crack mitigation and durability enhancement in railroad crossties, and active confinement in concrete columns.

The first two studies examine the use of longitudinal TEC reinforcement to improve bond behavior and control transverse cracking in RC bridge decks. Conventional epoxy-coated (EC) bars provide corrosion protection but can exhibit reduced bond performance due to lower friction with the surrounding concrete, potentially contributing to wider cracks. TEC bars feature a modified surface texture intended to enhance mechanical interlock with the concrete. The first study evaluates large-scale composite bridge deck specimens reinforced with TEC and conventional EC bars under drying shrinkage, thermal variations, and flexural loading. The second study investigates a commercially available generation of TEC bars through surface characterization and bond testing, followed by an assessment of their behavior under high-cycle repeated flexural loading using large-scale bridge deck specimens. Together, these studies provide insight into the influence of reinforcement surface characteristics on bond behavior, transverse cracking, and bridge deck durability. The third study shifts to the rehabilitation context and assesses an SMA-based external technique for mitigating transverse cracking in EC-reinforced bridge decks. SMAs exhibit a shape memory effect that enables them to recover a previously established configuration upon thermal activation, generating recovery stresses that can introduce prestressing forces and promote crack closure. Building on this principle, the experimental program for this stage was designed to investigate a newly proposed coupled prestressing plate system, which is intended to reduce the width of existing cracks and partially restore the structural properties of bridge decks. The fourth and fifth studies extend the use of SMAs and explore their ability to serve as longitudinal reinforcement in prestressed concrete railroad crossties, focusing on localized prestressing and crack closure. Specifically, in the fourth study,

different NiTiNb- and FeMnSi-based reinforcement configurations are evaluated in full-scale crosstie specimens to investigate the feasibility of introducing localized prestressing forces in regions susceptible to cracking while maintaining the required flexural performance. The fifth study builds on the previous application by evaluating the crack-closure capabilities of longitudinal SMA reinforcement embedded in full-scale prestressed concrete crossties with pre-existing damage. The specimens undergo low-cycle repeated flexural loading to widen existing cracks, followed by thermal reactivation of the SMAs and additional loading to assess crack closure and changes in stiffness. Together, these investigations demonstrate the potential of SMA reinforcement to mitigate cracking and enhance the durability of railroad infrastructure. Lastly, the sixth study examines the use of SMAs as internal transverse reinforcement in RC columns designed for new construction. Unlike conventional external SMA confinement techniques, this approach uses internally embedded SMA reinforcement to generate active confinement within the concrete members. Experimental observations are complemented by three-dimensional finite element modeling to evaluate the confinement mechanism and its implications for the behavior of columns in regions susceptible to seismic demands.

Overall, this doctoral research advances the understanding of alternative reinforcement technologies for concrete transportation infrastructure. By examining the bond and crack-control characteristics of TEC bars used as longitudinal reinforcement and the prestressing, crack-closure, and confinement capabilities of SMAs used as longitudinal and transverse reinforcement, the investigation establishes an experimental basis for assessing the applicability of these innovative materials in practice. The findings contribute to the development of reinforcement strategies aimed at mitigating deterioration, improving structural behavior, and extending the service life of transportation infrastructure.