Search Results (201)

This study systematically investigates the plastic deformation behavior and load-bearing mechanisms of micropiles through integrated scaled physical modeling and nonlinear finite element analysis, with particular emphasis on quantifying plastic hinge characteristics. The development of plastic deformation in laterally loaded micropiles was analytically described using plastic hinge theory, complemented by experimental-numerical validation. The key findings demonstrate the following points. (1) Existing empirical formulas for plastic hinge length, based on sectional parameters, show significant discrepancies, with experimental calibration establishing an optimized length of 2D. (2) Parametric FEM studies of three diameter groups (3–7% longitudinal reinforcement ratio) reveal that cross-sectional geometry and reinforcement configuration collectively govern nonlinear ultimate capacity, where ≤0.1% reinforcement ratio variation induces <5% bearing capacity deviation. (3) Square sections exhibit 12–18% higher capacity than circular equivalents of the equivalent dimensions, with this advantage amplifying with increasing pile size. (4) While excessive reinforcement ratios (>6%) impair structural performance, emergent scale effects effectively mitigate associated capacity reduction. These findings provide critical insights for optimizing micropile design in geotechnical applications through coordinated consideration of geometric, material, and scale parameters. Full article

The objective of this study was to examine the seismic behavior of steel buildings equipped with linear and nonlinear viscous dampers that may exhibit variable capacity. More specifically, nonlinear time history analyses were conducted on two three-dimensional steel buildings utilizing a number of recorded seismic motions. Initially, it was assumed that the distribution of viscous dampers was uniform along the height of the building and, thus, the damping coefficients used to size the viscous dampers were derived. Subsequently, nonlinear time history analyses were performed assuming either linear or nonlinear viscous dampers, which may operate at 80%, 100%, and 120% of their capacity. The response parameters extracted by these analyses included the base shear (structural and inertial), the inter-story drift ratio (IDR), the residual inter-story drift ratio (RIDR), the absolute floor accelerations, the formation of plastic hinges, and the forces experienced by the dampers. On the basis of these response parameters, the most appropriate type of viscous dampers was indicated. Full article

To systematically study the mechanical behavior of a steel fiber-reinforced concrete (SFRC) pier under bending–torsion coupling, three pier specimens with a clear height of 1200 mm, a diameter of 300 mm, and an SFRC height of 300 mm in the plastic hinge region were designed and fabricated. Quasi-static tests were carried out to observe the damage patterns and failure modes of the specimens. On this basis, multiple finite element models were established using the ABAQUS 2018 software to study the influence of the torsion–bending ratio and SFRC height on the seismic performance of the pier. The results show that the bending–torsion coupling effect leads to a decrease in the bending and torsion capacities of the pier. The presence of torque causes the plastic hinge position to move up and the plastic hinge area to expand. Adding SFRC at the bottom of the pier can effectively improve the bearing capacity of the pier under earthquake action. The optimal height of SFRC is half of the clear height of the pier under the common torsion–bending ratio, which can not only improve the seismic performance of the structure but also avoid material waste. Full article

Corrosion in steel girder ends, progressing from localized thinning of the web and the lower flange to severe perforation in severe cases, can significantly affect structural integrity. This study evaluates the effects of severe corrosion, including web–lower flange disconnection and transverse flange perforation combined with web damage, on the residual shear strength of steel girder end web panels through experimental and numerical methods. Results indicate that when only the web is affected, post-buckling strength starts to decline by corrosion damaging the plastic hinge on the tension flange, disrupting the tension field action. Conversely, in cases involving simultaneous web and lower flange damage, localized yielding at fracture points near the flange damage leads to the abrupt rotation of the tension field inclination angle, causing an earlier and more pronounced decline in post-buckling strength compared to web-only damage scenarios. Full article

Leaf spring-type flexible hinges serve as critical transmission components in kilogram quantization energy balance systems. Investigating their bending behavior is crucial for enhancing measurement accuracy and ensuring structural reliability. This work employs molecular dynamics simulations to analyze the mechanical properties and deformation characteristics of such hinges under varying bending rates. The findings reveal a significant correlation between the bending rate and the hinges’ plastic deformation and microstructural evolution, indicating the presence of a critical bending rate. When the bending rate is below the critical threshold, the hinges exhibit excellent structural stability, characterized by low dislocation density, reduced von Mises stress, and limited temperature rise, making them suitable for long-term use. Conversely, when the bending rate exceeds the critical threshold, the hinges undergo significant plastic deformation, including notable increases in stress and temperature concentration, as well as microstructural alterations. Specifically, the initially stable crystal structure is disrupted, leading to the formation of numerous defect structures. These changes result in localized instability and elevate the risk of fatigue damage. This work comprehensively elucidates the mechanical responses and failure mechanisms of flexible hinges, providing valuable data and guidance for their optimized design and application. Full article

The world is facing climate change, biodiversity loss, and pollution, significantly impacting lower-middle-income countries like Egypt, Morocco, and Tunisia, which depend heavily on tourism. Poor waste management, unclear responsibilities, and weak policies contribute to environmental degradation. Tourism, a key economic driver, also increases the problem by high plastic use and waste generation during peak seasons. This study evaluates current waste management practices in Alexandria (Egypt), Essaouira (Morocco), and Hammam Sousse (Tunisia) and proposes improvements using a newly developed “Extended Sector Responsibility” (ESR) model, which introduces an innovative organizational approach to waste management in touristic destinations. Using a combination of desk research, questionnaires, waste sorting analyses, and expert interviews, our research identifies systemic deficiencies. None of the studied locations have formal source separation systems, and waste management heavily depends on the informal sector. Hotels exhibit limited capacity for effective waste practices due to the lack of municipal infrastructure for separate collection. Economic analysis of the ESR model, which involves the establishment of a new waste recovery facility, demonstrates that while such facilities can generate revenue exceeding operational costs under specific scenarios, their long-term viability hinges on additional funding, possibly through Extended Producer Responsibility (EPR) mechanisms. Although Egypt and Tunisia have EPR legislation, implementation remains inadequate, and Morocco lacks such frameworks. The study emphasizes the critical need for investments in municipal waste management infrastructure, including logistics, sorting, and recycling systems. It also highlights actionable opportunities for the tourism sector to reduce waste by minimizing single-use plastics and food waste. By adopting the ESR model, the tourism sector can play a pivotal role in transitioning to a circular economy, ultimately mitigating environmental impacts and enhancing sustainability in the region. Full article

To enhance the standardization and construction efficiency of prefabricated steel structures and to promote the application of cold-formed steel tubes with the advantages of high standardization, superior mechanical properties, and fast processing speeds, two types of composite beam to concrete-filled cold-formed high-strength square steel tubular column joints with different connection forms were designed in this study: the external diaphragm joint (ED joint) and the through diaphragm joint (TD joint). These joints were subjected to cyclic loading tests to evaluate the influence of the connection designs on key seismic performance parameters, such as failure modes, load-bearing capacities, the degradation of strength and stiffness, ductility, and energy dissipation capabilities. The results show that both the ED and TD joints experienced butt weld fractures at the bolted-welded connections on the beam, effectively transferring the plastic hinges from the joint zone to the beam and demonstrating good seismic performance. The ED joint specimen JD1 and the TD joint specimen JD2 exhibited similar load-bearing capacity, stiffness, strength degradation, and energy dissipation capacity. However, the TD joint showed lower ductility compared to the ED joint due to premature weld fractures. A nonlinear finite element model (FEM) was developed using MSC.MARC 2012, and the numerical simulation showed that the FEM could effectively simulate the hysteresis performance of the composite beam to concrete-filled, cold-formed, high-strength, square, steel tubular column joints with external and through diaphragms. Full article

In order to discuss the calculation model and design method of double-row sliding piles without a connected beam, a laboratory simulation test was carried out. According to pile top displacement, pile body deformation, and pressure distribution, the ratio of landslide thrust sharing between front and back piles is about 1:1.6. It is found that the thrust of the landslide behind the pile is triangular, and the total resistance is parabolic. A calculation model is presented which takes the plastic hinge above the slip plane as the zero shear directional support. The pile is divided into two parts, the upper part and the lower part, and the cantilever pile method and the finite difference method are used for calculation, respectively. This method can calculate the internal force accurately, and it is verified by an engineering example. Full article

Due to its high axial bearing capacity and good ductility, the embedded steel plate composite shear wall structure has become one of the most widely used lateral force-resisting structural members in building construction. However, bending failure is prone to occur during strong earthquakes, and the single energy dissipation mechanism of the plastic hinge zone at the bottom leads to the concentration of local wall damage. To improve the embedded steel plate composite shear wall structure, the plastic hinge zone of the composite shear wall is replaced by fiber-reinforced concrete (FRC) and analyzed by ABAQUS finite element simulation analysis. Firstly, the structural model of the embedded steel plate composite shear wall structure with FRC in the plastic hinge zone is established and the accuracy of the model is verified. Secondly, the effects of steel ratio, longitudinal reinforcement ratio, and FRC strength on the bearing capacity of composite shear walls are analyzed by numerical simulation. Finally, a method for calculating the embedded steel plate composite shear wall structure with FRC in the plastic hinge zone is proposed. It is shown that the displacement and load curves and failure modes of the model are basically consistent with the experimental results, and the model has high accuracy. The axial compression ratio and FRC strength have a great influence on the bearing capacity of composite shear walls. The calculation formula of the normal section bending capacity of the embedded steel plate composite shear wall structure with FRC in the plastic hinge zone is proposed. The calculated values of the bending capacity are in good agreement with the simulated values, which can provide a reference for its engineering application. Full article

For allowable defect analyses, the fracture toughness of materials needs to be accurately predicted. In this regard, a lower fluctuation of fracture toughness can lead to reduction in safety and economic risks. Crack tip opening displacement (CTOD), which is the representative parameter for fracture toughness, can be measured by various methods, such as the ${\mathsf{\delta }}_5$, the J-conversion method, the single clip gauge method, and the double clip gauge method. When calculating CTOD from test results, the principle of similar triangles, which adopts the plastic hinge model, is influenced by the rotation factor, $r_p$. Therefore, in order to reduce the fluctuation of CTOD, the exact value of $r_p$ must be defined. This study investigates various methods to predict fracture toughness in metallic materials, and assess the pros and cons of each method. Moreover, the equation of $r_p$ is modified by using a double clip gauge in compact tension (CT) to reduce the fluctuation of CTOD. The $r_p$ value is derived from 0.55 to 0.68, using the double clip gauge method. Finite element analysis is used to derive the $r_p$ values, which range from 0.50 to 0.66, in order to verify the validity of the derived $r_p$ values. This ensures the validity of the $r_p$ value derived from the experiment. In addition, the fluctuation of CTOD, based on the modified equation of $r_p$, is lower than that using the single clip gauge method, according to BS 7448. Full article

This study investigates the mechanical behavior of cover-plate reinforced connections in steel frames with I-section columns and middle- or wide-flange H-beams, addressing gaps in current design standards. Finite element analyses validated by experimental data were employed to explore the effects of cover-plate geometry—shape, length, and thickness—on seismic performance. Results demonstrate that cover plates improve load-bearing capacity and ductility by relocating plastic hinges outward from joint regions. Specifically, cover-plate connections increased ductility by 25%, yield moment by 15%, and initial rotational stiffness by 7% compared to non-reinforced connections. The shape of the top cover plate had minimal impact on mechanical behavior. The cover-plate length and thickness significantly influenced seismic ductility and load-bearing capacity. The cover-plate thickness should be at least 0.3 times the beam flange thickness (not less than 6 mm) while ensuring the combined thickness of the cover plate and beam flange does not exceed the column flange thickness. These recommendations address the conservatism of existing standards, balancing material efficiency and seismic performance. Optimal cover-plate lengths of 0.7 to 0.9 times the beam depth were also identified. These findings provide practical guidelines for designing resilient steel frame connections in seismic regions. Full article

Despite the many advantages of tube systems with braces, known as trussed tubes, no specific seismic design criteria exist in the current regulations to design them, and practitioners utilize common methods used for common building structures to deal with designing such systems. The aim of this study is to investigate the performance of a 31-story steel trussed-tube building designed according to the customary design provisions. To evaluate the performance of the code-conforming designed structure, a three-dimensional nonlinear static (pushover) analysis is employed, and the acceptance criteria corresponding to different performance levels are examined. The obtained performance-based results are then compared with the design based on the customary guidelines, and the shortcomings of common design regulations in the design of trussed-tube buildings are highlighted. By observing the state of the plastic hinges, as well as force-controlled joints at two distinct earthquake hazard levels, it is found that the structure under study, which was loaded, analyzed, and designed exactly in compliance with the requirements of the regulations and standards, does not satisfy the performance criteria. In a typical nonlinear brace hinge, for instance, the results indicate that the LS acceptance criterion has been exceeded by approximately 30 percent at the BSE-1 hazard level. Also, the drifts surpass the 1% limit at specific levels, with the maximum drift reaching approximately 1.4%. As a result, the design of trussed-tube systems based on common codes and regulations can lead to an unsafe design that lacks the expected performance intended in their service life. Full article

This study explores the behavior of exposed column bases in concrete-filled steel tubular (CFST) and steel structures, with a focus on cases where base plates yield due to out-of-plane deformation. Understanding these mechanisms is crucial for improving the design and safety of these structures. Experimental tests and numerical analyses were conducted on four specimens to investigate their lateral load versus drift angle behavior. The tests demonstrated that base plates exhibited sufficient deformation capacities and enhanced hysteresis characteristics. Finite element method (FEM) analysis successfully traced the load–deformation relationships observed in the tests, providing detailed insights into stress distribution on the base plates. Based on these analyses, a simplified calculation method was proposed to evaluate the horizontal strength of exposed column bases. The proposed method showed excellent agreement with the test results, highlighting its potential as a practical tool for structural design. Full article

Ultra-high performance concrete (UHPC) combined with shorter stud shear connectors (h/d < 4) presents challenges that existing analytical models for stud connectors cannot adequately address. This study enhances the elastic foundation beam model to better accommodate these material and dimensional changes. Key improvements include the analytical calculation of equivalent foundation stiffness, which incorporates the rotation of the stud head—an aspect often neglected in previous research—and considers the post-yield plastic hinge at the stud weld. The proposed analytical model effectively captures variations in stud diameter and concrete elastic modulus, providing a load–slip curve with broader applicability than traditional empirical formulas. Validation against experimental data from 21 push-out specimens of varying diameters shows strong agreement, confirming the accuracy of the method. Moreover, a parametric study based on the analytical model reveals the sequential relationship between the formation of plastic hinges at the stud weld and the development of plastic regions in the concrete. This relationship is influenced by factors such as stud diameter, yield strength, and concrete strength. Notably, an increase in concrete strength significantly enhances the shear force at the stud root at the point when the concrete reaches its compressive strength. This explains why high-strength concrete specimens exhibit lower ultimate slip. These findings provide a crucial basis for understanding the behavior of stud shear connectors in composite structures. Full article

Reinforced concrete (RC) structures are vulnerable to damage under dynamic loads such as earthquakes, necessitating innovative solutions that enhance both performance and sustainability. This study investigates the integration of Engineered Cementitious Composites (ECC) in RC frames to improve ductility, durability, and energy dissipation while considering cost-effectiveness. To achieve this, the partial replacement of concrete with ECC at key structural locations, such as beam–column joints, was explored through experimental testing and numerical simulations. Small-scale beams with varying ECC replacements were tested for failure modes, load–deflection responses, and crack propagation patterns. Additionally, nonlinear quasi-static cyclic and modal analyses were performed on full RC frames, ECC-reinforced frames, and hybrid frames with ECC at the joints. The results demonstrate that ECC reduces the need for shear reinforcement due to its crack-bridging ability, enhances ductility by up to 25% in cyclic loading scenarios, and lowers the formation of plastic hinges, thereby contributing to improved structural resilience. These findings suggest that ECC is a viable, sustainable solution for achieving resilient infrastructure in seismic regions, with an optimal balance between performance and cost. Full article