International Concrete Abstracts Portal

This study examines the lateral cyclic response of a repaired damaged bridge pier originally reinforced with fiber-reinforced polymer (FRP) bars, particularly glass FRP (GFRP), as a corrosion-resistant and durable alternative to traditional steel. An as-built large-scale hybrid (GFRP-steel) reinforced concrete (RC) column had an outer cage reinforced with GFRP bars and an inner cage reinforced with steel reinforcing bars. The columns were first tested under cyclic lateral loading, where the hybrid specimen demonstrated ductility and energy dissipation capacity comparable to the conventional single-layer steel RC column. Following these initial tests, both specimens were repaired using FRP wraps and retested under the same loading protocol, resulting in a total of four tests. Enhanced structural integrity and energy dissipation demonstrate the effectiveness of innovative repair techniques in seismic engineering. These findings provide a blueprint for resilient infrastructure in earthquake-prone areas and contribute to advancements in bridge design and repair strategies.

This paper presents the interface shear between ordinary concrete and ultra-high-performance concrete (UHPC) connected with glass fiber-reinforced polymer (GFRP) reinforcing bars. Following ancillary tests on reinforcing bar fracture under in-plane shear loading, concrete-reinforcing bar assemblies are loaded to examine capacities and failure modes as influenced by the size, spacing, and number of the reinforcing bars. While the shear behavior of bare reinforcing bars is primarily governed by the orientation of the load-resisting axes in the glass fibers and their volume, the size and spacing of the reinforcement largely control the interface capacity by affecting the load-transfer mechanism from the reinforcing bar to the concrete. The degree of stress distribution affects the load-displacement response of the interface, which is characterized in terms of quasi-steady, kinetic, and failure regions. The primary failure modes of the interface comprise rebar rupture and concrete splitting. The formation of cracks between the ordinary concrete and UHPC results from interfacial deformations, leading to spalling damage when applied loads exceed service levels. An analytical model is formulated alongside an optimization technique. The capacities of the interface in relation to the reinforcing bar rupture and concrete splitting failure modes are predicted. Furthermore, a machine learning algorithm is used to define a failure envelope and propose practice guidelines through parametric investigations.

This paper presents the behavior of anchorage zones, also known as end zones, with discrete reinforcing bars and continuous meshes. To examine the implications of various reinforcing schemes on the capacity, cracking, and failure of end zones, 50 block specimens are loaded, and their responses are analyzed. Test parameters include the types of reinforcing bar materials (steel and glass fiber-reinforced polymer, (GFRP)) and the configurations of the reinforcing bars and steel meshes (single and multiple placements). In terms of load-carrying capacity, the specimens embedded with the GFRP rebars outperform those with the steel reinforcing bars and meshes by 14.0%. The post-peak load drop of the blocks with the steel and GFRP reinforcing bars is analogous due to distributed axial stresses in the unreinforced concrete region, differing from the abrupt drop observed in the specimens with the steel meshes that intersect the concrete in orthogonal directions. While concrete splitting originates from local tension generated near the axial compression, the location of cracking is dominated by the path of stress trajectories related to the number of reinforcing bars, which is not recognized in the case of the meshed specimens. The pattern of the isostatic lines of compression clarifies the development of bursting forces that cause cracking in the concrete. A two-stage analytical model is formulated to predict the magnitude of bursting forces and determine the effects of several parameters on the response of the end zones. The applicability of existing design expressions is assessed, and the need for follow-up research is delineated.

This study investigated the shear bond behavior, with and without optimized interfaces, between conventional and geopolymer steel fiber–reinforced concretes. Sixteen prismatic and eight cylindrical composite specimens were cast with interface inclination angles of 45° and 27°, respectively. In prisms, the inclined interface area was varied: eight were optimized by 50% to balance compressive and shear stresses, allowing a more accurate determination of cohesion and friction coefficients under steel fiber effects. Fiber volume fractions of 0.0, 0.5, 1.0, and 1.5% were tested, and the influence of epoxy at the interface was also assessed. Optimized prisms exhibited adhesive failure along the interface, matching the internal friction angle, whereas non-optimized prisms showed cohesive failure with a friction angle deviating from the interface. Increasing fiber content improved performance, especially when combined with epoxy. A new bond shear strength model is proposed, incorporating friction, cohesion, and fiber effects.

The challenges of deterioration and increasing maintenance costs in steel-reinforced concrete railway sleepers emphasize the urgent need for innovative, durable, and sustainable alternatives. This study evaluated the shear strength of precast concrete sleepers prestressed with basalt fiber-reinforced polymer (BFRP) rods, using normal self-consolidating concrete (NSCC) and fiber-reinforced self-consolidating concrete (FSCC). Seven full-scale specimens, each 2590 mm (8 ft, 6 in.) in length and prestressed to 30% of the tensile strength of BFRP rods in accordance with the Canadian Highway Bridge Design Code (CHBDC), were tested to assess cracking loads, ultimate strength, bond behavior, and failure mechanisms. All tests were conducted in accordance with the American Railway Engineering and Maintenance-of-Way Association (AREMA) guidelines. The results indicate that all specimens met AREMA design load requirements without visible cracks or slippage based on a train speed of 64 km/h (40 mph), annual traffic of 40 MGT (million gross tons), and sleeper spacing of 610 mm (24 in.). Comparative analysis using CSA S806-12 (R2021) design standard and ACI 440.4R-04 (R2011) design guide revealed that predictions based on CSA S806-12 (R2021) were less conservative than those from ACI 440.4R-04 (R2011) for the shear strength of BFRP prestressed sleepers. The BFRP rods exhibited excellent tensile performance, with minimal prestress losses, and their sand-coated surface ensured efficient load transfer by preventing slippage and enhancing the bond strength. FSCC specimens demonstrated delayed cracking, enhanced crack control, and ductility compared to NSCC specimens. These findings highlight the potential of BFRP prestressed concrete sleepers, particularly when combined with FSCC, as a sustainable solution for railway infrastructure, emphasizing the need for a design code refinement for BFRP applications.