Search Results (25)

Vertical joints are commonly required in precast concrete shear walls when large wall panels are divided for fabrication, transportation, and erection. To reduce on-site work and improve assembly efficiency, this study proposes and investigates a hybrid steel–grout vertical joint, namely a steel-anchor-ring grouted connection, which uses embedded threaded sleeves, steel anchor rings, an inserted vertical bar, and high-strength grout to transfer shear between adjacent wall panels. Monotonic direct shear tests, cyclic shear tests under normal tension and compression, and cyclic loading tests on precast shear wall specimens were conducted to investigate its mechanical behavior. The load–slip behavior, observed interface debonding, and final shank fracture in the direct shear tests suggested that grout–panel interface bond contributed substantially to the pre-peak response, whereas anchor-ring action became increasingly important after bond degradation. Comparison of the cyclic shear specimens suggested that normal tension promoted interface opening and bond degradation, leading to slip-dominated behavior, whereas normal compression enhanced interface contact and post-peak stability. For the specimens tested, the measured-to-calculated resistance ratios based on the code-based expression were 1.97–2.70 under direct shear and compression–shear conditions, but decreased to 1.20–1.31 under tension–shear loading. Wall-level demand analysis showed that the shear transferred across the vertical joint was significantly affected by both joint location and wall shear span ratio; larger shear span ratios increased the joint shear demand, whereas offset joint layouts reduced the demand. The wall specimens, designed relative to the code-based resistance, exhibited limited joint-related cracking and stable hysteretic behavior, and failed by wall-base flexural damage, indicating the shear-transfer effectiveness of the proposed joint under the tested configurations. Full article

This study investigates the flexural behavior, load-carrying capacity, and crack propagation of concrete beams reinforced with hybrid glass-fiber-reinforced polymer (GFRP) and steel bars. To evaluate the structural performance, concrete beam specimens with cross-sectional dimensions of 150 mm × 300 mm and a total length of 2050 mm were fabricated using a design concrete compressive strength of 35 MPa and tested under flexural loading. Each tested specimen featured a distinct hybrid reinforcement configuration to investigate the influence of bar arrangement on the mechanical behavior. Flexural cracks were systematically monitored using a crack-width comparator gauge at specific loading stages, accounting for key milestones such as ultimate load capacity and sudden load drops. The experimental findings were complemented by an analytical model to validate the performance parameters and predict the ultimate capacity. The results demonstrate that the specific configuration and arrangement of hybrid reinforcement significantly influence the post-cracking stiffness and crack growth. Specifically, the hybrid configuration effectively balances the ductile response of steel with the brittle behavior of GFRP, achieving significant control over serviceability crack widths and an enhanced ultimate load-carrying capacity. Experimental results indicated that for elements exhibiting identical axial stiffness, the reinforcement layering configuration provided a 66% improvement in the deformability factor alongside a 10% enhancement in the load-carrying capacity. It is recommended that the steel tension reinforcement be positioned in the inner layer at a spacing of about two times the GFRP bar diameter to mitigate corrosion risks. Additionally, it was established that the theoretical load capacity accounted for 70% to 86% of the experimental load capacity. Full article

Glass fiber–reinforced polymer (GFRP) reinforcement provides an effective alternative to conventional steel in concrete structures due to its corrosion resistance. Nevertheless, the lower elastic modulus of GFRP necessitates careful consideration of serviceability behavior in GFRP-reinforced concrete members. This study presents a numerical sectional analysis model for predicting the flexural response and ultimate capacity of hybrid reinforced concrete beams incorporating embedded GFRP profiles in combination with either mild steel or GFRP reinforcement bars under monotonic static loading. The proposed model employs realistic nonlinear stress–strain relationships for concrete and steel, together with secant moduli of elasticity evaluated at different loading stages. Particular emphasis is placed on detailed stress distribution in flexural sections, including the contribution of tension stiffening in the post-cracking regime. The formulation integrates nonlinear constitutive material behavior with theoretical sectional equilibrium to evaluate the effective flexural secant stiffness. For practical serviceability assessment and to reduce dependence on complex analytical procedures, strain vectors and stiffness matrix components are derived using elasticity coefficients that reflect modulus degradation obtained from numerical analysis. The accuracy of the model is verified through comparison with experimental results, including ultimate flexural capacity and moment–deflection responses. Many crucial parameters were studied, such as the longitudinal reinforcement ratio, type of reinforcement, concrete compressive strength, position of the I-GFRP profile, and rotation of the I-GFRP profile. The results of this study demonstrated that both the longitudinal reinforcement ratio and the rotation of the I-GFRP profile have a significant influence on the ultimate load capacity and deflection behavior. The close agreement between numerical predictions and experimental observations demonstrates the reliability and applicability of the proposed model for structural engineering analysis and design. Full article

The corrosion of prestressed tendons in concrete structures remains a major durability concern, especially for post-tensioned members exposed to aggressive environments. High-strength aluminum alloy (AA) bars exhibit favorable characteristics such as corrosion resistance, low density, and high ductility and may therefore provide an alternative or supplementary prestressing material in durability-oriented structural design. In this study, a bonded post-tensioned T-shaped concrete beam with hybrid prestressing combining prestressed steel (PS) strands and 7075 AA bars was investigated. A refined finite element model was developed by considering the bond-slip relationship between the AA tendons and grout inside corrugated tubes. The flexural behavior of the beam was analyzed through a combination of finite element simulation and sectional theoretical analysis. In addition, a fatigue-life assessment framework was established based on vehicle fatigue loads and material fatigue constitutive models, and the fatigue performance of the proposed hybrid beams was compared with that of conventional prestressed concrete beams. The theoretical predictions agreed reasonably well with the numerical results. Results indicated that partial replacement of PS strands with corrosion-resistant AA bars could alter the governing fatigue failure mode and improve the fatigue durability of prestressed beams under corrosive conditions. These findings highlight the potential of hybrid AA–PS prestressing as a durability-oriented strategy for concrete beams in corrosive environments. Full article

Corrosion concerns motivate the use of alternatives to conventional steel reinforcement in RC beams. This review evaluates fiber-reinforced polymer (FRP) bars and hybrid steel–FRP composite bars (SFCBs) used for durability-critical applications. We conducted a structured literature search focused on 2010–2025 and included seminal pre-2010 studies for context. Experimental studies and code provisions were screened to synthesize evidence on load–deflection response, cracking, and failure, with brief notes on UHPC systems. FRP-RC offers corrosion resistance but limited ductility and an abrupt post-peak response. Steel is ductile and provides warning before failure. SFCB combines durability with steel-core ductility and yields gradual softening and higher energy absorption. Practice should select reinforcement based on stiffness–ductility–durability trade-offs. Current codes only partially cover hybrids. Key gaps include standardized bond–slip and tension-stiffening models for SFCB and robust data on long-term performance under aggressive exposure. Full article

This study proposes a precast concrete bridge pier system designed to enhance seismic resilience and post-earthquake reparability. The structural configuration integrates ultra-high-performance concrete (UHPC), externally replaceable steel-angle energy-dissipating components, and unbonded post-tensioned tendons. The seismic performance of the system was evaluated through quasi-static tests under cyclic loading. Experimental results demonstrated that the proposed pier exhibited stable hysteretic behavior and minimal residual displacement, effectively concentrating damage within the intended plastic hinge region. The superior strength of UHPC further contributed to improved load-bearing capacity and less localized concrete compressive damage at the rocking interface. The external steel angles improved the energy dissipation capacity of the precast column significantly, and its external arrangement made the post-earthquake replacement much easier as compared to internal energy dissipation bars. The feasibility of the proposed seismic-resilient pier system was successfully validated, offering a promising solution for bridge design in high-seismic-intensity regions. Full article

This paper reports a statistical analysis of a database archiving information on the strengths of the materials in existing Italian bridges having pre- and post-tensioned concrete beams. Data were collected in anonymous form by analyzing a stock of about 170 bridges built between 1960 and 2000 and located in several Italian regions. To date, the database refers to steel reinforcing bars, concrete, and prestressing steel, whose strengths were gathered from design nominal values, acceptance certificates, and in situ test results, all derived by consulting the available documents for each examined bridge. At first, this paper describes how the available data were collected. Then, the results of a statistical analysis are presented and commented on. Moreover, goodness-of-fit tests are carried out to verify the assumption validity of a normal distribution for steel reinforcing bars and prestressing steel, and a log-normal distribution for concrete. The database represents a valuable resource for researchers and practitioners for the assessment of existing bridges. It may be applied for the use of prior knowledge within a framework where Bayesian methods are included for reducing uncertainties. The database provides essential information on the strengths of the materials to be used for a simulated design and/or for verification in the case of limited knowledge. Goodness-of-fit tests make the collected information very useful, even if probabilistic methods are applied. Full article

The construction of highway bridges using continuous precast prestressed concrete girders provides an economical solution by minimizing formwork requirements and accelerating construction. Different ways can be used to integrate bridge continuity and enable the development of negative bending moments at piers. Continuous bridge connections enhance structural integrity by reducing deflections and distributing loads more efficiently. Research has led to the development of various continuity details, categorized into partial and full integration, to improve performance under diverse loading conditions. This review summarizes studies on both partial and fully integrated continuous bridges, highlighting improvements in connection resilience and the incorporation of advanced construction technologies. While extended deck reinforcement presents an economical solution for partial continuity, it has limitations, especially in longer spans. However, full integration provides additional benefits, such as further reduced deflections and bending moments, contributing to improved overall structural performance. Positive-moment connections using bent bars have shown enhanced performance in achieving continuity, though skewed bridge configurations may reduce the effectiveness of continuity. Ultra-High-Performance Concrete (UHPC) has been identified as a superior material for joint connections, providing greater load capacity, durability, and seismic resistance. Additionally, mechanical splices, such as threaded rod systems, have proven effective in achieving continuity across various load types. The seismic performance of precast prestressed concrete girders relies on robust joint connections, particularly at column–foundation and column–cap points, where reinforcements such as steel plates, fiber-reinforced shells, and unbonded post-tensioning are important for shear and compression transfer. Full article

The diagnosis of post-stressed anchor rods is essential for maintaining the service and ensuring the safety of Electricité de France (EDF) structures. These rods are critical for the mechanical strength of structures and electromechanical components. Currently, the standard method for estimating the effective tension of post-stressed tie rods with a free length involves measuring the residual force using a hydraulic jack. However, this method can be costly, impact the structure’s operation, and pose risks to employees. Until now, there has been no reliable on-field approach to estimating residual tension using a lightweight setup. This research introduces a nondestructive method using multimodal ultrasonic guided waves to evaluate the residual tension of anchor rods with a few centimeters free at one end. The methodology was developed through both laboratory experiments and simulations. This new method allows for the extraction of dispersion curves for the first three modes, bending, torsional, and longitudinal, using time–frequency analysis and enables the estimation of the steel bar’s properties. Future work will focus on applying this methodology in the field. Full article

Sandwich panels, consisting of two concrete wythes that encase an insulating core, are designed to improve energy efficiency and reduce the weight of construction applications. This research examines the thermal and flexural properties of a novel sandwich panel that incorporates ultra-high-performance fiber-reinforced concrete (UHPFRC) and cellular lightweight concrete (CLC) as its core material. Seven sandwich panel specimens were tested for their thermo-flexural performance using four-point bending tests. The experimental parameters included variations in UHPFRC thickness (20 mm and 30 mm) and different shear connector types (shear keys, steel bars, and post-tension steel bars). The study also assessed the effects of adding steel mesh reinforcement to the UHPFRC layer and evaluated the performance of UHPFRC box sections without a CLC core. The analysis concentrated on several critical factors, such as initial, ultimate, and serviceability loads, load–deflection relationships, load–end slip, load–strain relationships, composite action ratios, crack patterns, and failure modes. The thermal properties of the UHPFRC and CLC were evaluated using a transient plane source technique. The results demonstrated that panels using post-tension steel bars as shear connectors achieved flexural performance, and the most favorable composite action ratios reached 68.8%. Conversely, the box section exhibited a brittle failure mode when compared to the other sandwich panels tested. To effectively evaluate mechanical and thermal properties, it is important to design panels that have adequate load-bearing capacity while maintaining low thermal conductivity. This study introduced a thermo-mechanical performance coefficient to evaluate both the thermal and mechanical performance of the panels. The findings indicated that sandwich panels with post-tension steel bars achieved the highest thermo-mechanical performance, while those with steel connectors had the lowest performance. Full article

In practical engineering, due to quality inspections of connections between prefabricated components and construction errors, reserved reinforcing bars in the transition layer may be partially insufficient or even completely absent. This defect significantly impacts the structural performance of sleeve connections, particularly under tensile or shear forces. This paper proposes a novel reinforcement method to address the connection issues caused by the absence of reserved reinforcing bars in the transition layer and verifies its feasibility through systematic experiments. To this end, this paper proposed a novel reinforcement method of grouting sleeve connection considering the absence of reserved bars in the transition layer, and 45 specimens with different reinforcement parameters were fabricated and tested under tension. Before verifying the reliability of the novel reinforcement method, nine specimens were fabricated and tested to verify the weldability of grouting sleeves and reinforcing bars. According to the test results, the fully grouted sleeves, including Grade 45 steel and Q345, showed good weldability with the HRB400 steel bars, while the ductile iron grouted sleeve showed poor weldability. When the single-sided welding length was greater than or equal to six times the diameter of the post-retrofitted connecting steel bar (D₂), the primary failure mode observed in specimens utilizing the novel reinforcement method was the fracture of the prefabricated steel bar. The novel reinforcement method could be used to repair the defect of the grouting sleeve connection considering the absence of reserved reinforcing bars in the transition layer. When the single-sided welding length was 4D₂, with a relative protective layer thickness of 2D₂, and using C60 grade reinforcement material, this combination of conditions represented the critical condition to avoid weld failure between the grouting sleeve and the post-retrofitted connecting steel bars. In practical reinforcement projects, it is suggested that the single-sided welding length should be 5D₂, the relative protective layer thickness should be 3D₂, and the reinforcement material strength should be C60. Full article

This paper investigates, experimentally and numerically, the shear strengthening of Normal Concrete (NC) beams using post-tensioning steel bars and Engineered Cementitious Composite (ECC) reinforced with chemically cured Palm Fronds (PFs). The benefits of strain-hardening ECC and the tensile strength of PFs cured with 6% wt Alkali NaOH solution beside post-tensioned bars have been employed herein. Seven full-scale Reinforced Concrete (RC) beams were fabricated and experimented with under three-point loading until failure. The test parameters include the strengthening technique, type, and configuration of the material used for strengthening. The strengthening process has been implemented through two techniques: Externally Bonded Reinforcement (EBR) and Near-Surface Mounted (NSM) Reinforcement. The strengthening materials have been configured and placed in horizontal, vertical, and inclined positions. The effectiveness of the strengthening methods has been evaluated by examining their cracking propagations, load-deflection responses, collapse modes, elastic stiffness, and absorbed energy. It was found that the proposed strengthening systems could significantly control the crack pattern and failure mode, and they could enhance the ultimate load amplitude up to 37% and 50% for NSM ECC with PFs and EBR post-tensioning steel bars, respectively. Nonlinear three-dimensional finite element models of the tested beams were developed and validated with the test data, where it was found that finite element models predict the structural performance of tested beams with a maximum error of only 2%. Full article

This research aims to present a new generation of seismic-resisting systems designed for precast reinforced concrete (RC) bridge piers in modern sustainable cities to withstand moderate to high seismic activity. The proposed system consists of two self-centering (SC) systems operating in parallel to bring together all features of the required resiliency during a seismic action. The first/main system is a hollow core precast segmental bridge column, and the second is composed of an SC precast unit and energy dissipation (ED) steel reinforcements positioned in the main pier segment’s hollow core. To study the performance of the proposed system, a finite element model was first developed to capture the behavior of experimentally tested precast bridge columns. After validation, the created model was systematically studied to investigate the performance of the entire proposed system under cyclic loading. The effects of three parameters related to the ED system were investigated, including the reinforcement ratio, the unbonded length of ED bars, and the SC post-tensioned force ratio. Furthermore, the impact of FRP wrapping on the lower part of the core column of the ED system was also investigated. An analytical model predicting the characteristic points of the lateral response of the proposed system based on the superposition concept is also proposed. The FE results showed that the entire proposed system is a new design-based resilient system with the ability to dissipate energy without compromising the SC capacity of the main resisting system. Compared to the typical precast hollow core segmental column, a 6% reinforcement ratio of the ED unit can cause a 60% increase in lateral resistance and a 220% increase in the ED capacity. The analytical model can successfully be applied in the design of the proposed system to provide customized ED capabilities and controlled lateral resistance. Full article

This article expounds on the problem of the use of de-icing salts in the corrosion of steel rebars in bridge decks and their effect on post-tensioning elements. In particular, this paper focuses this problem on structures affected by an aggregate–alkali reaction and without any waterproof treatment using the example of one structure whose repair was carried out in 2020. In this structure, the internal stresses due to the aggregate–alkali reaction caused longitudinal cracks in the upper face of the deck, through which the penetration of chloride ions was concentrated, causing, finally, the brittle fracture of the steel bars and the corrosion of the prestressing elements. This article also explains some conclusions about the most probable mechanisms that resulted in the brittle fracture of the steel bars due to the extraordinary and unexpected nature of this phenomenon. Full article

Bar splicing is considered an essential part of the construction process of reinforced concrete (RC) due to the ease of installation in construction, transportation constraints, and restricted length of reinforcing bars. Splices serve the primary role of joining reinforcement bars in standard RC elements such as columns, walls, beams, slabs, and joints. Bond behavior between the bars and the concrete is one of the fundamental qualities required for appropriate RC structure design and analysis, as it affects serviceability and ultimate limit states. The most common failure found in lap splice locations is debonding, which occurs at the splice region and insufficient lapped length is considered as the primary cause because of design or construction mistakes, design by outmoded code, and natural catastrophes. As a result, strengthening existing substandard splices in RC structures is critical. The purpose of this research is to analyze and summarize experimental strengthening solutions for inadequate splices. The most common methods are confining spirals, confining with internal or external steel stirrups or carbon fiber reinforced polymer (CFRP), concrete jacketing, fiber reinforced polymers (FRP), post-tensioning prestressed RC, external confining with CFRP, near surface mounted (NSM) techniques, ultra-high-performance concrete (UHPC), fiber reinforced concrete (FRC) and combinations of two methods. Each method of strengthening is evaluated based on its performance, benefits, drawbacks, application-specific elements, and variables influencing the design and scope of applicability. A comparison of the key methodologies was also carried out. The most recent studies and recommendations for improving inadequate lapped splices are provided. Full article