Armin Mehrabi

Pile splicing is generally considered in construction because of transportation limits, length requirements, construction means and methods, and strength capacity. A major challenge in the use of precast prestressed UHPC piles is the lack of efficient and effective splicing solutions. To address the problem, this study evaluated different pile splicing methods for UHPC H-piles and their constructability. The analysis and design for strength capacity and detailing presented here are based on relevant established guidelines and design codes for UHPC. This study assessed two pile splicing methods: epoxy-bonded dowels and near-surface mounted bars (NSMBs). The analysis demonstrated that the epoxy-bonded dowel method provides a moment capacity that is 127% of the pile moment capacity in the strong direction and 139% of the pile moment capacity in the weak direction. In comparison, the NSMB method achieved 121% in the strong direction and 106% in the weak direction. Both methods developed the established strength capacity requirements. The constructability of both pile splicing options was evaluated to provide practical guidelines for their preparation in preplanned and unplanned situations. The results reported are for 18-inch UHPC H-piles; however, the construction and analytical approach applies to other pile sizes as well. The pile splicing options developed are recommended for further experimental investigations.

The state-of-the-art literature in engineering provides information on the current state of technical subjects, shapes the understanding of relevant research, and communicates potential next directions for future exploration in relation with condition and risk assessment and sustainable maintenance of post-tensioned (PT) concrete bridges. However, the formulation of a quantitative methodological framework in selecting suitable safety assessment and management techniques for in-service PT concrete bridges is insufficient in the current literature. The absence of such a framework could render ineffective the sustainability of bridge maintenance strategies. In addition, the failure of structural assets due to deterioration and lack of proper maintenance is regarded as an important risk aspect. This is because structural failure often results in adverse economic, environmental, and safety outcomes. To underscore this, formulating mitigation strategies through sustainable asset maintenance programs is consequential. In recognition of the current limitation, this paper proposes a new framework with a structured methodology for the risk assessment and management of PT concrete bridges. This framework helps the bridge practitioners to navigate through design, inspection results, environmental factors, estimation of probability of failure, and corresponding consequences to calculate the risk and decide on the maintenance. It encompasses the decision on the type and interval of the inspection regime, repair and strengthening, and potentially replacing existing work. The presentation of this framework is original in that it carries the stochastic approach through all steps of risk assessment and maintenance decision making while allowing room for the inclusion of evolving methods. The proposed framework can be used for the development of a complete guide capable of stochastic, reliability-based, data-driven, and quantitative risk assessment and maintenance management for PT concrete bridges.

Bridges and other structures that support critical services necessary for communities constitute an important part of surface infrastructure

This study investigates damage detection in the tendons of post-tensioned segmental box girder bridges, focusing on the vibration-based technique and its application in conjunction with the Precursor Transformation Matrix (PTM). Due to the critical role of bridge tendons in structural integrity, efficient and timely detection methods are essential. The methodology combines theoretical modeling with Finite Element Method (FEM) simulations and empirical data collection to evaluate the PTM’s effectiveness in identifying tendon damage. Key results indicate that the PTM, when paired with vibration analysis, enhances the identification and localization of damage, proving to be a robust method in structural health monitoring. This approach not only speeds up damage detection but also potentially lowers maintenance costs by pinpointing specific damage sites, thereby preventing widespread structural failures. The findings offer a promising tool for ensuring the longevity and safety of post-tensioned bridges.

Skewed supports complicate load paths in continuous steel I-girder bridges, causing secondary stresses and differential deformations. For a continuous bridge where tensile stresses are developed in the top flange of the steel girders over the intermediate supports, these effects may exacerbate potential fatigue issues for the top flanges. There is a gap in knowledge regarding the level of stress one can expect at these locations, and the stress level can render the problem either serious or trivial. This paper has been successful in providing this information, which was not available before. The study examines the fatigue performance of the top flange in girders over skewed supports. Results are presented from a detailed investigation consisting of 3D finite element modeling to evaluate 26 skewed bridges in the State of Florida that represent the wide range of geometries found in practice. The analysis focused on stress ranges in the top flanges and axial demands on end cross-frame members under fatigue truck loading. A preliminary analysis helped to select the appropriate element type and support conditions. The maximum factored stress range of 3.63 ksi obtained for the selected group of bridges remains below the 10 ksi fatigue threshold for an AASHTO Category C connection, alleviating the concerns about the fatigue performance of the continuous girder top flange over the intermediate pier. Hence, fatigue is unlikely to be a concern in the flanges at this location. Statistics on computed stress ranges and cross-frame forces that provide an understanding of the expected values and guidance for detailing practices are also presented. A limited comparative refined FE analysis on two different types of end cross-frame to girder connections also provided useful insight into the fatigue sensitivities of the skew connections. Half-Round Bearing Stiffener (HRBS) connections performed better than the customary bent plate connections. The HRBS connection reduces girder flange stress concentration range by at least 18% compared to the bent plate connection. The maximum stress concentration range in bent plate components is significantly higher than in the HRBS connection components. The work documented in this paper is important for understanding the fatigue performance of the cross-frames and girders in support regions in the upcoming 10th edition of the AASHTO Bridge Design Specifications that may include plate stiffeners oriented either normally or skewed to the girder web, or Half-Round Bearing Stiffeners.

Fiber-Reinforced Polymer (FRP) composites have emerged as a promising alternative to conventional steel reinforcements in concrete structures owing to their benefits of corrosion resistance, higher strength-to-weight ratio, reduced maintenance cost, extended service life, and superior durability. However, there has been limited research on non-destructive testing (NDT) methods applicable for identifying damage in FRP-reinforced concrete (FRP-RC) elements. This knowledge gap has often limited its application in the construction industry. Engineers and owners often lack confidence in utilizing this relatively new construction material due to the challenge of assessing its condition. Thus, the main objective of this study is to determine the applicability of two of the most common NDT methods: the Ground-Penetrating Radar (GPR) and Phased Array Ultrasonic (PAU) methods for the detection of damage in FRP-RC elements. Three slab specimens with variations in FRP type (glass-, carbon- and basalt-FRP, i.e., GFRP, CFRP, and BFRP, respectively), bar diameter, bar depths, and defect types were investigated to determine the limitations and detection capabilities of these two NDT methods. The results show that GPR could detect damage in GFRP bars and CFRP strands, but PAU was limited to damage detection in CFRP strands. The findings of this study show the applicability of conventional NDT methods to FRP-RC and at the same time identify the areas with a need for further research.