The concrete industry has long been adding discrete fibers to cementitious materials to compensate for their (relatively) low tensile strengths and control possible cracks. Extensive past studies have identified effective strategies to mix and utilize the discrete fibers, but as the fiber material properties advance, so do the properties of the cementitious composites made with them. Thus, it is critical to have a state-of-the-art understanding of not only the effects of individual fiber types on various properties of concrete, but also how those properties are influenced by changing the fiber type. For this purpose, the current study provides a detailed review of the relevant literature pertaining to different fiber types considered for fiber-reinforced concrete (FRC) applications with a focus on their capabilities, limitations, common uses, and most recent advances. To achieve this goal, the main fiber properties that are influential on the characteristics of cementitious composites in the fresh and hardened states are first investigated. The study is then extended to the stability of the identified fibers in alkaline environments and how they bond with cementitious matrices. The effects of fiber type on the workability, pre- and post-peak mechanical properties, shrinkage, and extreme temperature resistance of the FRC are explored as well. In offering holistic comparisons, the outcome of this study provides a comprehensive guide to properly choose and utilize the benefits of fibers in concrete, facilitating an informed design of various FRC products.

Performance assessment of a transportation network is naturally a complicated problem. This is mainly due to the fact that such a spatially distributed network is subjected to a variety of natural hazards and environmental stressors while it consists of a range of components with different ages. Among various components of a transportation network, bridges are known to be the most important but vulnerable components. Previous efforts to investigate the functionality of transportation networks, especially after earthquake events, have proven that damage to highway bridges may directly cause a major degradation in the functionality of the entire network. Considering the extensive socioeconomic consequences of network disruptions, the main focus of the current study is on the seismic resilience assessment of highway bridge networks exposed to deterioration processes. While this study provides a comprehensive computational framework to include several sources of uncertainty that must be taken into acc...

Collision of vehicles into RC bridge columns can result in significant damage to individual bridge components, leading to partial or full collapse of the entire bridge. Among various alternatives to RC columns, concrete-filled steel tubes (CFSTs) have received growing attention because of their rapid construction, reduced labor requirement, and reasonable material cost. Despite the promise of this alternative, however, there is a gap in the existing literature concerning the measures that can be used for the analysis and design of this important category of bridge columns subjected to impact loads. To address this gap, a detailed investigation is conducted in the current study, using a set of impact simulations. For this purpose, representative finite-element (FE) models are developed and validated with the experimental test results. To make a direct comparison possible, the numerical simulations include both CFST and RC columns under a range of vehicle impact scenarios. The structural performance is evaluated using a comprehensive set of measures, including peak dynamic force (PDF) and equivalent static force (ESF). On establishing the necessary metrics, the current study provides a systematic effort to examine the contribution of the main analysis and design parameters to the impact response of the columns under consideration. Based on the simulation results, the sufficiency of the current specifications is evaluated, and a generalized equation is proposed to predict the ESF for CFST columns.

Fiber-reinforced concrete (FRC) is a promising construction material mainly because of the crack-controlling mechanisms that discrete fibers can impart to inherently brittle concrete. Macrofibers, in particular, have been proven effective for providing post-crack ductility and toughness, while synthetic fibers are a promising solution to avoid corrosion-related durability issues. To assess the performance enhancement provided by macro-synthetic concrete fibers, this study performs flexural tests on FRC beams containing three different types of macro-synthetic fibers. The selected fibers include polypropylene (PP), polyvinyl alcohol (PVA), and alkali-resistant glass (ARG) macrofibers mixed at volume fractions of 0.5%, 1.0%, and 1.5%. Static and dynamic fresh properties are monitored using the vibrating Kelly ball (VKelly) test. Beam specimens are then placed under a third point bending configuration, as per ASTM C1609 Standard, to measure load versus mid-span deflection. Strength and toughness parameters are derived from the load–deflection data to assess the flexural performance of the FRC composite systems under consideration. The parameters of interest include first peak strength (pre-crack flexural strength) and post-crack residual strength and toughness provided by fiber addition. Of the mixtures tested, ARG fiber mixtures show the highest residual strength and toughness values, followed by PP and PVA fiber mixtures. ARG fibers produce the most workable mixtures at all fiber volumes, while PVA fibers show a tendency to encounter dispersion issues at higher volume doses. The outcome of this study is expected to facilitate the selection of fibers by giving insight into their relative contribution to fresh and hardened flexural properties of FRC.