Search Results (190)

Background: Perianal Crohn’s disease (pCD) is one of the most disabling complications of inflammatory bowel disease, characterized by fistulas and abscesses that demand precise imaging for diagnosis, treatment planning, and follow-up. Magnetic resonance imaging (MRI) is considered the reference standard, but endoanal ultrasound (EAUS) with high-frequency 360° probes provide a readily available, cost-effective, and repeatable alternative. Methods: We performed a narrative review of the literature, evaluating studies on the EAUS technique, diagnostic applications, distinguishing features of Crohn’s-related fistulas, and comparative analyses with MRI. Consensus documents and structured reporting initiatives were also included. Results: EAUS provides high-resolution visualization of the anal sphincter complex and intersphincteric space, enabling the reliable detection of fistulas and abscesses. Characteristic features such as tract width > 4 mm, bifurcation, hyperechoic debris, the Crohn’s Ultrasound Fistula Sign (CUFS), and the rosary sign assist in differentiating Crohn’s from cryptoglandular fistulas. EAUS is well-suited for serial monitoring, perioperative seton guidance, and therapeutic decision-making. Emerging tools such as Doppler and shear wave elastography provide additional information on activity and fibrosis. MRI remains indispensable for supralevator disease, deep pelvic sepsis, and standardized activity indices. Comparative studies indicate similar sensitivity for simple fistulas, with MRI superior in complex cases; combining both modalities maximizes accuracy. Conclusions: EAUS is a practical and repeatable imaging tool that complements MRI in the multidisciplinary management of perianal Crohn’s disease. Advances such as 3D imaging, contrast enhancement, and elastography may enable validated activity scoring—for example, a future PEACE (Perianal Endosonographic Activity in Chron’s Evaluation) Index—further strengthening its role in longitudinal care. Full article

This study investigates the effects of air pressure, glue pressure, and viscosity on atomization characteristics through experimental and simulation methods, aiming to reveal gas–liquid interaction mechanisms and optimize process parameters. The rheological parameters of aqueous polyurethane adhesives with varying viscosities were characterized. Spray characteristics, including spray angle, cured film diameter, and thickness, were quantitatively measured under different operating conditions. The internal flow field and droplet dynamics were numerically analyzed. The results indicate the following: Increasing the air pressure (from 0.3 to 0.7 MPa) enlarges the spray angle and film diameter while reducing the film thickness. In contrast, increasing the glue pressure enlarges all three parameters: spray angle, film diameter, and film thickness. Furthermore, increasing the viscosity within the test range reduces the spray angle, film diameter, and film thickness. These effects stem from enhanced gas kinetic energy and shear intensity (promoting liquid film fragmentation), an increased fluid flow rate with glue pressure, and strengthened droplet resistance to breakup with suppressed spreading at higher viscosities. This research provides useful criteria for nozzle design and the optimization of industrial atomization processes involving non-Newtonian adhesives. Full article

Ultra-High-Performance Concrete (UHPC) jacketing is an effective and innovative strengthening method in the renovation projects of concrete bridges. In December 2021, the UHPC-jacketing method was first applied to rehabilitate a seriously damaged bridge in the Changzhou Bridge rehabilitation project in Guangzhou, China. However, the interfacial shear behavior between the Normal Reinforced Concrete (NRC) substrate and UHPC is a crucial factor for the effectiveness of the UHPC-jacketing strengthening method. Therefore, four push-out specimens were designed in this paper to investigate the effects of the embedded bolt diameter (12 mm and 16 mm) and construction method (cast-in-place UHPC layer (ZJ group) and precast UHPC panels with infilled high-strength mortar (GJ group)) on the shear behavior of the NRC–UHPC interface. The results indicated that with the increased bolt diameter from 12 mm to 16 mm, the first peak load (P₁) rose from 920.17 kN to 1048.07 kN (+13.9%) in the ZJ group and from 838.08 kN to 1204.20 kN (+43.7%) in the GJ group. The residual loads (P_r) of the GJ group were smaller than those of the ZJ group, at 41.9% and 30.2% lower for bolt diameters of 12 mm and 16 mm, respectively. The construction method of high-strength mortar filling was significantly influenced by the bolt diameter, with a diameter of 16 mm required to fully utilize its shear resistance. Predictions from ACI 318-19 underestimated experimental shear capacity by 70.6% on average, while AASHTO (2017) and Fib provided accurate estimations (within 9.8–10.9% of experimental values). Full article

In this study, an effective strengthening method was investigated to improve the seismic performance of masonry brick walls. The strengthening method comprised the use of shotcrete, which was applied in both glass fiber-reinforced and unreinforced forms for steel plates and tie rods. Thirteen wall specimens constructed with vertical perforated masonry block bricks were tested under diagonal compression in accordance with ASTM E519 (2010). Reinforcement plates with different thicknesses (1.5 mm, 2 mm, and 3 mm) were anchored using 6 mm diameter tie rods. A specially designed steel frame and an experimental loading program with controlled deformation increments were employed to simulate the effects of reinforced concrete beam frame system on walls under the effect of diagonal loads caused by seismic loads. In addition, numerical simulations were conducted using three-dimensional finite element models in Abaqus Explicit software to validate the experimental results. The findings demonstrated that increasing the number of tie rods enhanced the shear strength and overall behavior of the walls. Steel plates effectively absorbed tensile stresses and limited crack propagation, while the fiber reinforcement in the shotcrete further improved wall strength and ductility. Overall, the proposed strengthening techniques provided significant improvements in the seismic resistance and energy absorption capacity of masonry walls, offering practical and reliable solutions to enhance the safety and durability of existing masonry structures. Full article

Reinforced concrete (RC) deep beams constructed with low-strength concrete are susceptible to sudden splitting failures in the strut region due to shear–compression stresses. To mitigate this vulnerability, various strengthening techniques, including steel plates, fiber-reinforced polymer sheets, and cementitious composites, have been explored to confine the strut area. This study investigates the structural performance of RC deep beams with low-strength concrete, strengthened externally using an Engineered Cementitious Composite (ECC) layer. To ensure effective confinement and uniform shear distribution, shear reinforcement was provided at equal intervals with configurations of zero, one, and two vertical shear reinforcements. Four-point bending tests revealed that the ECC layer significantly enhanced the shear capacity, increasing load-carrying capacity by 51.6%, 54.7%, and 46.7% for beams with zero, one, and two shear reinforcements, respectively. Failure analysis through non-linear finite element modeling corroborated experimental observations, confirming shear–compression failure characterized by damage in the concrete struts. The strut-and-tie method, modified to incorporate the tensile strength of ECC and shear reinforcement actual stress values taken from the FE analysis, was used to predict the shear capacity. The predicted values were within 10% of the experimental results, underscoring the reliability of the analytical approach. Overall, this study demonstrates the effectiveness of ECC in improving shear performance and mitigating strut failure in RC deep beams made with low-strength concrete. Full article

In order to enhance the seismic performance of existing masonry structures and optimize the thickness of the strengthening layer, ultra-high-performance concrete (UHPC) can be used as an enhancement material. Based on current concrete strengthening methods, the bearing capacity and seismic behavior of existing masonry structures strengthened with UHPC were investigated numerically. The effects of the strengthening layer thickness and reinforcement ratio on the structural strengthening results were analyzed numerically. The structural behaviors before and after an earthquake, with various strengthening methods, were compared and discussed. The results show that the ratio of axial resistance to shear resistance increases linearly with the resistance ratio. The seismic performance of damaged masonry walls can be improved by about 150% and 250% when 20 mm thick double-sided plain UHPC layers and 30 mm thick double-sided plain UHPC layers are used for strengthening, respectively. The axial compression ratio of masonry walls can be reduced by about 60–70% when double-sided plain UHPC layers are used for strengthening. Full article

Reinforced concrete structures often require retrofitting due to damage caused by natural disasters such as earthquakes, floods, or hurricanes; deterioration from aging; or exposure to harsh environmental conditions. Retrofitting strategies may involve adding new structural elements like shear walls, dampers, or base isolators, as well as strengthening the existing components using methods such as reinforced concrete, steel, or fiber-reinforced polymer jacketing. Selecting the most appropriate retrofit method can be complex and is influenced by various factors, including initial cost, long-term maintenance, environmental impact, and overall sustainability. This study proposes utilizing an artificial neural network (ANN) to predict sustainable and cost-effective seismic retrofit solutions. By training the ANN with a comprehensive dataset that includes jacket thickness, material specifications, reinforcement details, and key sustainability indicators (economic and environmental factors), the model was able to recommend optimized retrofit designs. These designs include ideal values for jacket thickness, concrete strength, and the configuration of reinforcement bars, aiming to minimize both costs and environmental footprint. A major focus of this research was identifying the optimal number of neurons in the hidden layers of the ANN. While the number of input and output neurons is defined by the dataset, determining the right configuration for hidden layers is critical for performance. The study found that networks with one or two hidden layers provided more reliable and efficient results compared to more complex architectures, achieving a total regression value of 0.911. These findings demonstrate that a well-tuned ANN can serve as a powerful tool for designing sustainable seismic retrofit strategies, helping engineers make smarter decisions more quickly and efficiently. Full article

This study evaluates the effectiveness of rigid node connection prototypes for joining bamboo, in response to the growing need for sustainable construction solutions. Considering the superior mechanical properties of bamboo, including its flexibility and strength, the research focuses on the design and testing of nine connection prototypes subjected to compression, shear, and tensile tests in a laboratory. The results obtained demonstrate that the prototypes significantly exceed the established minimum strength criteria, with average maximum loads of 62.19 kN in compression tests, 10.16 kN in shear tests, and 25.41 kN in tensile adhesion tests. These findings not only confirm the viability of bamboo as a sustainable construction material but also highlight the need to develop efficient connection methods that integrate bamboo’s flexibility with the strength of other materials. Through these connections, bamboo presents itself as a solid alternative to address housing deficits and promote responsible construction practices. The research suggests continuing additional studies to strengthen knowledge about bamboo’s behavior in different construction contexts, thereby contributing to a more sustainable future in building. Full article

To address the existing challenges of lacking a unified and reliable shear capacity prediction model for fiber-reinforced polymer (FRP)-strengthened reinforced concrete beams (FRP-SRCB) and the excessive experimental workload, this study establishes a shear capacity prediction model for FRP-SRCB based on machine learning (ML). First, the correlation between input and output parameters was analyzed by the Pearson correlation coefficient method. Then, representative single model (ANN) and integrated model (XGBoost) algorithms were selected to predict the dataset, and their performance was evaluated based on three commonly used regression evaluation metrics. Finally, the prediction accuracy of the ML model was further verified by comparing it with the domestic and foreign design codes. The results manifest that the shear capacity exhibits a strong positive correlation with the beam width and effective height. Compared to the ANN model, the XGBoost-based prediction model achieves determination coefficients (R²) of 0.999 and 0.879 for the training and test sets, respectively, indicating superior predictive accuracy. Furthermore, the shear capacity calculations from design codes show significant variability, demonstrating the superior predictive capability of ML algorithms. These findings offer a guideline for the design and implementation of FRP reinforcement in actual bridge engineering. Full article

Türkiye, a country that suffers significant structural damage from earthquakes, was struck by two major quakes on 6 February 2023, centered in Pazarcık (M_w = 7.7) and Elbistan (M_w = 7.6) in Kahramanmaraş. These earthquakes caused extensive damage and destruction to urban concrete structures, significantly contributing to the loss of life. Inadequate designs in columns, which are meant to maintain structural integrity and transfer forces, were a primary cause of the structural damage. This study provides information about these catastrophic earthquakes, focusing on the detailed examination of damages in reinforced-concrete (RC) columns. Structural analyses were conducted on a selected RC building, taking into account the primary causes of column damage: low-strength concrete and insufficient transverse reinforcement. Five different concrete classes and two transverse reinforcement spacing options were considered to analyze the impact of concrete strength. To address the exceeded shear forces in the columns, a fiber-reinforced polymer (FRP) wrapping method was employed for strengthening. Initially, a reinforcement analysis was performed on a single column that exceeded shear force limits, followed by strengthening applications on all columns exceeding the limit shear force. The results demonstrated that carbon fibers have a significant impact on the shear forces in columns. The conclusion of the research is that FRP increases the ductility of concrete columns, enabling them to withstand seismic forces more effectively. This is vital in ensuring the integrity of structures in earthquake-prone areas. Using FRP materials can also significantly reduce the carbon footprint associated with concrete construction by minimizing the need for maintenance and extending the lifespan of structures. FRP presents a sustainable and effective solution for addressing failures in reinforced concrete columns. Its unique properties not only enhance strength and durability but also significantly improve the resilience of structures against corrosion, seismic events, and overload conditions. Full article

Beam–column joints in reinforced concrete frames are subjected to complex forces and are prone to damage under seismic actions. This paper proposes a method to strengthen beam–column joints using angle steel and split bolts. The hysteretic performance of the strengthened components is investigated through test and finite element numerical simulation. The influencing parameters, including concrete strength grade, axial compression ratio, stirrup characteristic value, angle steel leg length, and angle steel leg thickness, are analyzed. The results show that angle steel can simultaneously enhance the strength and stiffness of the strengthened joints. With an increase in concrete strength grade, the load-carrying capacity of the strengthened components continuously increases. However, when the axial compression ratio exceeds 0.6, the load-carrying capacity of the strengthened components significantly decreases. The size of the stirrup characteristic value has little influence on the shear resistance of the strengthened joints. The leg length and leg thickness of the angle steel have certain effects on the strengthening effectiveness. The method of outward movement of plastic hinges can effectively improve the seismic performance of bi-directionally loaded spatial joints. Full article

This study investigates the surrounding rock failure caused by the fracture line of the main roof above the gob-side roadway during fully mechanized top-coal caving mining in a 19 m thick coal seam. As mining progresses, stress concentration occurs in the roadway roof. Furthermore, the fracture line of the main roof above the roadway poses a significant threat to the structural stability of the gob-side roadway, leading to the localized failure of the roof structure, which consequently affects the safe and efficient production of the mine. This study investigates the shear failure mechanism of the roadway top coal and analyzes the failure characteristics and stress evolution law of the surrounding rock when the main roof fracture line (MRFL) is located above the roadway through three integrated approaches: theoretical analysis, numerical simulation, and physical similarity modeling. To effectively mitigate damage to the top coal, it is proposed to implement a five-hole tray coupled with high-strength prestressed anchor cables for reinforcing the surrounding rock, while compact wooden piles in combination with single pillars are employed to strengthen the roadway support control measures. It is verified by field tests that these control methods significantly improve the stability of coal above the entry and greatly mitigate the likelihood of surrounding rock failure. Full article

Cu-based alloys and composites are popular to prepare electroconductive parts. However, their processing can be challenging, especially in case of composites strengthened with oxides. To save the necessary time and costs, numerical simulations can be of help when determining the deformation behaviour of (newly introduced) materials. The study presents a combined method of strengthening of Cu by adding 5 wt.% of La₂O₃ particles and performing shear-based deformation by equal channel angular pressing (ECAP). The effects of the method on the microstructure, mechanical properties, and thermal stability of the composite are examined both numerically and experimentally. The results showed that the La₂O₃ addition caused the maximum imposed strain to be higher for the composite than for commercially pure Cu, which led to the development of subgrains and shear bands within the microstructure, and a consequent increase in microhardness. The numerical predictions revealed that the observed differences could be explained by the differences in the material plastic flow (comparing the composite to commercially pure Cu). The work hardening supported by the addition of La₂O₃ led to a significant increase in stress and punch load during processing, as well as contributed to a slight increase in deformation temperature in the main deformation zone of the ECAP die. Certain inhomogeneity of the parameters of interest across the processed workpiece was observed. Nevertheless, such inhomogeneity is typical for the ECAP process and steps prospectively leading to its elimination are proposed. Full article

To investigate the reinforcement effects of different reinforcement methods including basalt fibers on unreinforced masonry walls (UMWs), this study examined three reinforcement methods: ordinary mortar, basalt fiber mortar, and basalt fiber mesh mortar. Three masonry wall specimens were designed: ordinary mortar surface-strengthened masonry wall (O-MW), basalt fiber mortar surface-strengthened masonry wall (BF-MW), and basalt fiber mesh mortar surface-strengthened masonry wall (BFM-MW). Quasi-static tests were conducted to analyze the failure phenomena, hysteresis curves, backbone curves, energy dissipation capacity, and stiffness degradation. The results show that, compared to O-MW, BF-MW exhibited a 10.3%, 1.5%, and 28.1% increase in cracking load, peak load, and energy dissipation capacity, respectively. Meanwhile, BFM-MW showed more pronounced improvements, with cracking load and peak load increasing by 41.6% and 3.9%, respectively, and initial stiffness rising by 32.8%. However, this method shifted the failure mode of masonry walls from flexural failure to shear failure. Both basalt fiber mortar reinforcement methods outperformed ordinary mortar, each demonstrating distinct characteristics that can be selected based on practical application requirements. Full article

Epoxy asphalt, as a thermosetting and thermoplastic polymer composite material, has been widely used for steel bridge decks and specialty pavements due to its road performance, thermal stability, rutting resistance, and durability. However, the poor compatibility between epoxy resin binder and asphalt, due to the difference in chemical structure, polarity, and solubleness, severely restricts their practical applications in the construction of bridges and roads. Herein, we proposed a facial method to strengthen their compatibility by blending the poly(styrene-butadiene-styrene)-modified carbon nanotubes (SBS-CNTs) in the composite. The SBS-CNTs were found to evenly disperse in epoxy asphalt matrix with the epoxy resin contents of 10%–30% and could form the three-dimensional bi-continuous cross-linked structure at 30%. Moreover, the addition of epoxy resin increased the glass transition temperature (Tg) and enhanced the high-temperature shear capacity and tensile strength (over an order of magnitudes) of SBS-CNT-modified asphalt, which showed high potential for applications in the construction of bridges and roads, providing an alternative approach for improving the performance of epoxy asphalt. Full article