Search Results (153)

To investigate the influence of transverse confinement on the bond performance between glass-fiber reinforced polymer (GFRP) bars and concrete, an experimental study involving 28 beam-type bond specimens was designed and conducted. The effects of key parameters, including the spacing of transverse stirrup confinement (60, 80, and 120 mm), concrete strength (C30 and C50), concrete cover thickness (1.5d and 2.5d), surface characteristics of GFRP bars (ribbed and sand coated), bar diameter (16 and 20 mm), and bond length (5d and 10d), on the bond-slip behavior and failure modes were systematically examined. The results indicate that transverse stirrup confinement effectively restrains the development of splitting cracks, thereby significantly enhancing bond strength and improving the ductility of the bond interface. Both the bond strength and residual bond strength increase as stirrup spacing decreases. Under confined conditions, the bond strength of ribbed GFRP bars is 17.26% to 41.72% higher than that of sand-coated bars. Additionally, bond strength increases with higher concrete strength and greater concrete cover thickness but decreases with longer bond lengths. This study provides an experimental basis and theoretical reference for the design of GFRP-reinforced concrete structures that consider the transverse confinement effect. Full article

Background: Fragility fractures of the pelvis (FFP) are an increasing challenge in aging societies. Among these, FFP type 4B (“H-shaped” sacral fractures) represent the most unstable subtype, characterized by bilateral sacral ala fractures with transverse dissociation. Optimal fixation strategies remain debated, as spinopelvic fixation provides maximal stability but is invasive, while iliosacral screws often fail in osteoporotic bone. Trans-sacral bar (TSB) fixation has been proposed as a less invasive alternative, though evidence for its use in FFP 4B remains limited. Methods: We conducted a retrospective single-center study of 31 elderly patients (mean age 77.9 years; 87.1% female) with CT-confirmed FFP type 4B fractures treated between 2015 and 2022 using navigation-guided TSB constructs. Surgical configurations included hybrid fixation (TSB + bilateral iliosacral screws, n = 25) and dual-bar fixation (n = 6). Outcomes included perioperative complications, implant survival, radiographic healing, pain, and mobility at 3 and 12 months. Opportunistic CT-derived Hounsfield units (HU) were used to assess bone quality. Results: All patients had severe osteoporosis (mean HU 75.8 ± 30.1). Mean operative time was 71 min, and mean hospitalization was 9.1 days. No intraoperative or postoperative complications occurred, and no implant loosening, migration, or revision surgeries were required. At 3 months, mean pain score was 1.9, further decreasing to 1.1 at 12 months; 60.9% of patients reported complete pain resolution. Mobility improved in most cases, with 80.6% discharged with a walker or crutches. Radiographic follow-up confirmed stable healing in all patients. Conclusions: Navigation-guided TSB-based fixation provided stable osteosynthesis with excellent implant survival, significant pain relief, and early mobilization in elderly patients with FFP type 4B fractures. Hybrid and dual-bar constructs both achieved reliable outcomes. TSB fixation thus represents a safe and effective alternative to spinopelvic fixation in this fragile population. Larger multicenter prospective studies are warranted to confirm these findings and refine fixation strategies. Full article

This work presents a new insight into the buckling phenomenon to approach the calculation of the compressed bar with the following firm supports: bi-pinned, bi-fixed, and fixed-pinned. Buckling is redefined as the result of second-order deformations in the real bar by gradually applying the compression load, thus dismissing Euler’s critical load. The analytical results are obtained from the differential equation of the directrix beam with sinusoidal deformation associated with each type of support. The bending moment is generated only by the compression load acting on the initial geometric imperfection. These analytical solutions are associated with first-order effects, applying the entire compressive load, and with second-order effects, applying the load gradually. The analytical solutions are continuous functions. In this paper, the Finite Transfer Method was applied to obtain numerical results. The bending moments, transverse displacements, and normal stresses are presented as the results. Beams with different initial imperfections in the directrix are studied: with sinusoidal deformation, with deformation produced by a specific transverse load, and with deformation produced by a uniform transverse load. The results obtained through the analytical expressions derived from the gradual application of the load are compared with those results obtained numerically when calculating the beam under second-order conditions. It is concluded that in structural practice, they are equivalent. Full article

The vehicle lateral position within a lane is critical in road safety, particularly on curved sections, where excessive deviations are often associated with crashes. This study analyses the effect of three traffic-calming measures on the lateral position of vehicles on curves with varying radii and turning directions. The experiment was conducted using a driving simulator with the participation of 48 drivers, assessing two leading indicators: the vehicle’s mean lateral position (LP) and the standard deviation of that position (SDLP). The results showed that, in curves, male drivers tended to drive further from the centre of the lane compared to female drivers. Additionally, female drivers exhibited less weaving in their trajectories (lower SDLP). Older drivers adopted more centred trajectories; however, SDLP increased with age. Drivers with higher annual exposure tended to drive further from the lane centre in curves. Among the traffic-calming measures, red-coloured transverse bands (CTB) reduced the lateral position by approximately 0.12 m in left curves. In contrast, red peripheral transverse bars (PTB) proved most effective in lowering lateral variability (SDLP). Geometric differences were also observed: greater curve radii were associated with lower SDLP values. Full article

This paper outlines a structural qualification process to assess the use of newly developed high-modulus (HM) glass fiber-reinforced polymer (GFRP) bars with headed ends in the joint between concrete bridge barriers and decks. The main goals of the study are to evaluate the structural performance of GFRP-reinforced TL-5 barrier–deck systems under transverse loading and to determine the pullout capacity of GFRP anchorage systems for both new construction and retrofit applications. The research is divided into two phases. In the first phase, six full-scale Test-Level 5 (TL-5) barrier wall–deck specimens, divided into three systems, were constructed and tested up to failure. The first system used headed-end GFRP bars to connect the barrier wall to a non-deformable thick deck slab. The second system was similar to the first but had a deck slab overhang for improved anchorage. The third system utilized postinstalled GFRP bars in a non-deformable thick deck slab, bonded with a commercial epoxy adhesive as a solution for deteriorated barrier replacement. The second phase involves an experimental program to evaluate the pullout strength of the GFRP bar anchorage in normal-strength concrete. The experimental results from the tested specimens were then compared to the factored applied moments in existing literature based on traffic loads in the Canadian Highway Bridge Design Code. Experimental results confirmed that GFRP-reinforced TL-5 barrier–deck systems exceeded factored design moments, with capacity-to-demand ratios above 1.38 (above 1.17 with the inclusion of an environmental reduction factor of 0.85). A 195 mm embedment length proved sufficient for both pre- and postinstalled bars. Headed-end GFRP bars improved pullout strength compared to straight-end bars, especially when bonded. Failure modes occurred at high loads, demonstrating structural integrity. Postinstalled bars bonded with epoxy performed comparably to preinstalled bars. A design equation for the barrier resistance due to a diagonal concrete crack at the barrier–deck corner was developed and validated using experimental findings. This equation offers a conservative and safe design approach for evaluating barrier–deck anchorage. Full article

Bond behavior between steel bars and concrete is fundamental to the structural integrity and durability of reinforced concrete. However, corrosion-induced deterioration severely impairs bond performance, highlighting the need for advanced and reliable assessment methods. This paper pioneers an algorithm for an advanced ensemble learning framework to predict bond strength between corroded steel bars and concrete. In this framework, a novel Stacked Boosted Bond Model (SBBM) is developed, in which a Fusion-Based Feature Selection (FBFS) strategy is integrated to optimize input variables, and SHapley Additive exPlanations (SHAP) are employed to enhance interpretability. A merit of the framework is that it can effectively identify critical factors such as crack width, transverse confinement, and corrosion level, which have often been neglected by traditional models. The proposed SBBM achieves superior predictive performance, with a coefficient of determination (R²) of 0.94 and a mean absolute error (MAE) of 1.33 MPa. Compared to traditional machine learning and analytical models, it demonstrates enhanced accuracy, generalization, and interpretability. This paper provides a reliable and transparent tool for structural performance evaluation, service life prediction, and the design of strengthening measures for corroded reinforced concrete structures, contributing to safer and more durable concrete structures. Full article

Aluminium alloy (AA) bars have emerged in structural engineering applications mainly to reduce deterioration caused by corrosion. However, research on AA-reinforced concrete (RC) beams has been limited, despite RC beams reinforced with AA bars providing a study area with great potential. Therefore, this study mainly aims to investigate the behaviour of AA RC deep beams. The investigated parameters include concrete strength, tension reinforcement ratio, beam size, a/d ratio, and transverse reinforcement ratio, most of which have not yet been thoroughly studied. A finite element (FE) model was developed to obtain accurate predictions. The developed FE model predicted the actual load-bearing capacity with a mean value of 1.00. The findings indicated a clear trend in which shear force capacity increased from 124.1 to 181.4 kN with increasing concrete compressive strength from 20 to 40 MPa. A strong relationship between the reinforcement ratio and failure mode was obtained. The shear strength decreased from 2.95 to 2.1 MPa as the effective depth increased from 175 to 350 mm. An increase in transverse reinforcement ratio instigated an enhancement in shear force capacity. Finally, the applicability of the design models in the current literature was evaluated. The design formulations gave accurate predictions with an error of 3%. Full article

Traditional methods of construction for reinforced concrete columns utilize longitudinal steel bars and transverse ties. Field experience has shown that such a transverse reinforcement method is labor-intensive, time-consuming, and prone to inconsistencies in quality. Welded wire reinforcement (WWR) offers a prefabricated alternative, forming a closed cage that simplifies installation and speeds up the fabrication process. This study investigates the potential of using WWR as a replacement for conventional ties in reinforced concrete columns in pure compression. To achieve this objective, eight one-third-scale columns (1000 mm height, 200 × 200 mm cross-section) were tested under concentric axial loading inside a Universal Testing Machine. Four of the specimens contained WWR, while the other four had conventional ties. The variables that were considered in this study include the concrete compressive strength (34.3 and 43.5 MPa) and the grid size of the WWR (25 and 50 mm). This study investigated the influence of the type of transverse reinforcement on the strength, modulus of elasticity, and ductility of the confined concrete within the core. The findings of the study showed that lateral reinforcement in the form of WWR can increase the concrete core strength by 2.7% relative to corresponding columns employing ties when f′_c = 34.3 MPa was used. Conversely, the utilization of ties proved to be more effective than WWR in improving concrete core strength by an average of 28.8% when f′_c = 43.5 MPa was used. Additionally, WWR reinforced columns demonstrated a marginal 2.0% rise in the modulus of elasticity and a remarkable 21.0% increase in the ductility of the confined concrete core compared with corresponding tied columns. Theoretical predictions of the axial compressive capacity of WWR reinforced columns subjected to concentric loading based on the ACI-318 code provisions underestimated the experimental results by 20%. These findings demonstrate that WWR can serve as an effective substitute for conventional ties, particularly in cases where rapid installation and reduced labor costs are prioritized. Full article

Two new species from the Yellow Sea, Hypodontolaimus minus sp. nov. and Bolbolaimus distalamphidus sp. nov., are described in this study. Hypodontolaimus minus sp. nov. is characterized by a relatively small body length, a cuticle with two longitudinal lateral differentiations connected with transverse bars, four files of sublateral somatic setae, a pharynx with an anterior and posterior bulb, L-shaped spicules, a slightly swollen proximal end, a distal end tapered with a posterior pointed hook, and a gubernaculum with dorsal caudal apophysis. Bolbolaimus distalamphidus sp. nov. is characterized by a relatively small body size, a strongly annulated cuticle, six short outer labial sensilla and four long cephalic setae, an amphideal fovea unispiral oval that is far from the anterior end, slightly curved spicules, gubernaculum with anterior-pointed apophysis, and a conical tail. Phylogenetic analyses within the family Chromadoridae and the superfamily Microlaimoidea based on combined rDNA sequences confirmed the placement of Hypodontolaimus minus sp. nov. and Bolbolaimus distalamphidus sp. nov. The subfamily of Chromadorinae is shown as a monophyletic clade, the genera of subfamily Hypodontolaiminae are shown as a paraphyletic group, and the genus of Ptycholaimellus shows high intraspecific diversity. The placement of genera Aponema and Molgolaimus within the superfamily Microlaimoidea is discussed based on combined rDNA sequences. Full article

Traffic accidents remain a leading cause of mortality worldwide. In Spain, a total of 9666 accidents occurred on curves in 2023, highlighting the need for effective speed management strategies. This study analyses, using a driving simulator, the effectiveness of three low-cost traffic calming measures—checkerboard patterns, red peripheral transverse bars, and red coloured transverse bands—on vehicle speed through curves of varying radii and directions. Additionally, it examines the influence of driver characteristics (age, gender, and experience) and road geometric features (curve radius and direction) on driving behaviour. The simulated road included ten curves with radii ranging from 26 to 190 metres (operating speeds of 30–70 km/h) with traffic calming measures placed at the tangents before the curves. The sample consisted of 48 drivers. Men exhibited faster speeds than women, while younger drivers were faster than seniors. Increased driving experience (annual distances) correlated with higher speeds. Additionally, smaller radii resulted in lower speeds. Regarding the traffic calming measures, significant differences were found mainly where the road markings were placed (tangent) and in the initial phases of the curve. Checkerboard patterns performed better in curves with smaller radii. In contrast, red coloured transverse bands showed the best performance in larger radius curves. Full article

Reinforced concrete (RC) columns are structural components that carry loads and are vulnerable to damage and possible failure under blast loads. Understanding how damage accumulates and cracks propagate in these structural members is essential for improving their resilience and designing blast-resistant buildings. This study introduces an experimental approach to mitigate the fireball and fumes generated by an explosion, allowing for a more precise structural response assessment. With the help of high-speed cameras, this study experimentally investigates the real-time damage progression and crack formation in RC columns. To explore these failure mechanisms, laboratory-scale RC columns with a low reinforcement ratio are intentionally designed to experience significant damage, providing deeper insights into concrete-specific failure patterns. The tested columns are 1800 mm long and have a 100 mm diameter. Each specimen is reinforced with 3 mm longitudinal reinforcement bars and 2 mm transverse bars. An explosive driven shock tube (EDST) is used to apply blast loads, targeting the mid-height of the columns. High-speed digital image correlation (DIC) tracks the overall structural response. A numerical simulation is developed in LS-DYNA and compared with experimental data for validation. The findings demonstrate that the proposed FE model accurately simulates both the applied blast load and the resulting failure patterns. The difference between the mid-span lateral displacement predicted by the numerical simulation and the average experimental measurements remains within 15%. Full article

Strengthening lapped spliced reinforced concrete (RC) beams using tiny-diameter steel wires as near-surface-mounted (NSM) rods has not been carried out previously. Thus, the purpose of this work is to examine the behavior of RC beams with insufficient lap splices that are strengthened by NSM steel wires with different schemes to improve durability, efficiency, and effectiveness. At the middle of the beam, a splice length equal to 25 times the diameter of the rebar was used to join two tension bars. Many different schemes were implemented in strengthening the splice region, such as attaching longitudinal wires to the sides and/or bottom of the beam in different quantities with/without end anchorage, placing perpendicular and inclined U-shaped wires at the splice region in different quantities, and implementing a network of intersecting and opposite wires in two different directions. The effect of variables on the behavior of strengthened beams was studied. The findings proved that when the longitudinal wire reinforcement-to-lapped rebars area ratio was 9.4%, 18.7%, and 28%, the ultimate load of the beams was improved by 15.71%, 71.43%, and 104.57%, respectively. When the transverse U-shaped wire reinforcement ratio was 0.036, 0.051, 0.064, 0.075, and 0.150, the ultimate load of the beams was improved by 3.7%, 20%, 31.4%, 50%, and 80%, respectively, and the ultimate deflection was enhanced by 2%, 32%, 19%, 67%, and 62.4% compared to the unstrengthened beam. Full article

This study aims to investigate the bending load-bearing capacity of precast hollow composite slabs composed of ultra-high-performance concrete (UHPC) and Normal Concrete (NC). Through finite element numerical analysis and verification, this study analyzes various key factors influencing the performance of the composite slab, including the wall thickness of the square steel tube, the diameter of transverse reinforcing bars, the thickness of the precast bottom slab, and the strength grade of the concrete. The results indicate that the use of UHPC significantly enhances the bending performance of the composite slab. As the wall thickness of the square steel tube and the strength of UHPC increase, both the yield load and ultimate load capacity of the composite slab show considerable improvement. By conducting an in-depth analysis, this study identifies different stages of the composite slab during the loading process, including the cracking stage, yielding stage, and ultimate stage, thereby providing important foundations for optimizing structural design. Furthermore, a set of bending load-bearing capacity calculation formulas applicable to UHPC-NC precast hollow composite slabs is proposed, offering practical tools and theoretical support for engineering design and analysis. The innovation of this study lies not only in providing a profound understanding of the application of composite materials in architectural design but also in offering feasible solutions to the energy efficiency and safety challenges faced by the construction industry in the future. This research demonstrates the tremendous potential of ultra-high-performance concrete and its combinations in modern architecture, contributing to the sustainable development of construction technology. Full article

This paper introduces a new concept of random Sehgal contraction in the setting of random cone metric spaces. We explore the modern advancements of traditional fixed-point theorems in a random setting, elaborating on the Sehgal–Guseman fixed-point theorem within the realm of random cone metric spaces. A significant aspect of our research is the interplay between symmetry and randomness; while symmetry provides a framework for understanding structural properties, randomness introduces complexity, which can lead to unexpected behaviors. Our research provides a deeper understanding of the classical results and incorporates a detailed example to illustrate our findings. In addition, major random fixed-point results are also established, which could be applied to nonlinear random fractional differential equations (FDEs) and integral equations as well as to random boundary value problems (BVPs) related to homogeneous random transverse bars. Full article

This article presents a new parametric method for shaping flat transverse frame structural systems supporting thin-walled roofs made of flat sheets folded unidirectionally and transformed elastically to various shell forms. The parameterization was limited to one independent variable, that is the stiffness of the support joints. For different discrete values of simulated stiffness, the surface areas of the cross sections of the tensile and compressed elements and the section modulus of the bending elements were calculated so as to obtain the optimized work of the frame and its elements in the assumed load environment. The developed method allows for optimizing the work of frames considered as flat bar structural systems of building halls, taking into account the ultimate and serviceability limit states. The operation of the method is illustrated with an example concerning the formation of a flat frame working under a load characteristic for buildings located in a lowland area in a moderate climate. The authors intend to successively extend the method with new types of frame systems so as to obtain increasingly accurate and universal models defined by means of an increasing number of independent variables. These parameters are related to different forms and inclinations of columns and girders, and different external load types. The successive increase in the parameters defining the computational parametric model of the frame requires the use of increasingly advanced artificial intelligence algorithms to describe the static and strength performance of the buildings shaped, which makes the proposed method universal and the created structural systems effective in various external environments. Full article