Search Results (100)

Channels with three standard symmetrical sections and one asymmetric section are mounted as cantilever beams with the web oriented vertically. A classical solution to the analysis of stress in each thin-walled cantilever channel is provided using the principle of wall shear flow superposition. The latter is coupled with a further superposition between axial stress arising from bending and from the constraint placed on free warping imposed at the fixed end. Closed solutions for design are tabulated for the net shear stress and the net axial stress at points around any section within the length. Stress distributions thus derived serve as a benchmark structure for alternative numerical solutions and for experimental investigations. The conversion of the transverse free end-loading applied to a thin-walled cantilever channel into the shear and axial stress that it must bear is outlined. It is shown that the point at which this loading is applied within the cross-section is crucial to this stress conversion. When a single force is applied to an arbitrary point at the free-end section, three loading effects arise generally: bending, flexural shear and torsion. The analysis of each effect requires that this force’s components are resolved to align with the section’s principal axes. These forces are then considered in reference to its centroid and to its shear centre. This shows that axial stress arises directly from bending and from the constraint imposed on free warping at the fixed end. Shear stress arises from flexural shear and also from torsion with a load offset from the shear centre. When the three actions are combined, the net stresses of each action are considered within the ability of the structure to resist collapse from plasticity and buckling. The novelty herein refers to the presentation of the shear flow calculations within a thin wall as they arise from an end load offset from the shear centre. It is shown how the principle of superposition can be applied to individual shear flow and axial stress distributions arising from flexural bending, shear and torsion. Therein, the new concept of a ‘trans-moment’ appears from the transfer in moments from their axes through centroid G to parallel axes through shear centre E. The trans-moment complements the static equilibrium condition, in which a shift in transverse force components from G to E is accompanied by torsion and bending about the flexural axis through E. Full article

Collar monopile foundation is a new type of offshore wind power foundation. This paper explores the horizontal bearing performance of collar monopile foundation in saturated cohesive soil through a combination of physical experiments and numerical simulations. After analyzing the deformation characteristics of the pile–soil system under horizontal load through static load tests, horizontal cyclic loading tests were conducted at different cycles to study the cumulative deformation law of the collar monopile. Based on a stiffness degradation model for soft clay, a USDFLD subroutine was developed in Fortran and embedded in ABAQUS. Coupled with the Mohr–Coulomb criterion, it was used to simulate the deformation behavior of the collar monopile under horizontal cyclic loading. The numerical model employed the same geometric dimensions and boundary conditions as the physical test, and the simulated cumulative pile–head displacement under 4000 load cycles showed good agreement with the experimental results, thereby verifying the rationality and reliability of the proposed simulation method. Through numerical simulation, the distribution characteristics of bending moment and the shear force of collar monopile foundation were studied, and the influence of pile shaft and collar on the horizontal bearing capacity of collar monopile foundation at different loading stages was analyzed. The results show that as the horizontal load increases, cracks gradually appear at the bottom of the collar and in the surrounding soil. The soil disturbance caused by the sliding and rotation of the collar will gradually increase, leading to plastic failure of the surrounding soil and reducing the bearing capacity. The excess pore water pressure in shallow soil increases rapidly in the early cycle and then gradually decreases with the formation of drainage channels. Deep soil may experience negative pore pressure, indicating the presence of a suction effect. This paper can provide theoretical support for the design optimization and performance evaluation of collar monopile foundations in offshore wind power engineering applications. Full article

Conventional bolts frequently fail under large deformations due to stress concentration in soft rock tunnels. In contrast, yielding bolts incorporate energy-absorbing mechanisms to sustain controlled plastic deformation. This study employed FLAC3D to numerically investigate the pull-out, shear, and bending behaviors of yielding bolts, evaluating their support effectiveness in soft rock tunnels. Three-dimensional finite difference models incorporating nonlinear coupling springs and the Mohr–Coulomb criterion were developed to simulate bolt–rock interactions under multifactorial loading. Validation against experimental pull-out tests and field measurements confirmed the model accuracy. Under pull-out loading, the axial forces in yielding bolts decreased more rapidly along the bolt length, reducing stress concentration at the head. The central position of the maximum load-bearing capacity in conventional bolts fractured under tension, resulting in an hourglass-shaped axial force distribution. Conversely, the yielding bolts maintained yield strength for an extended period after reaching it, exhibiting a spindle-shaped axial force distribution. Parametric analyses reveal that bolt spacing exerts a greater influence on support effectiveness than length. This study bridges critical gaps in understanding yielding bolt behavior under combined loading and provides a validated framework for optimizing energy-absorbing support systems in soft rock tunnels. Full article

The prefabricated concrete channel, constructed by integrating factory-based prefabrication with on-site assembly, offers enhanced quality, reduced construction time, and minimized environmental impact. To promote its application in water conservancy projects, an innovative concrete joint combining semi-grouting sleeves and shear-resistant steel plates was proposed. Its seismic performance was assessed through a 1:3 scale low-cycle reversed loading test, focusing on failure mode, hysteretic behavior, skeleton curves, stiffness degradation, ductility, and energy dissipation. Results show that the joint primarily exhibits bending–shear failure, with cracks initiating at the sidewall–base slab interface. Also, the sidewall and base slab are interconnected through semi-grouting sleeves, while the concrete bonding is achieved via grouting and surface chiseling at the joint interface. The results indicated that the innovative concrete joint connection exhibits satisfied seismic performance. The shear-resistant steel plate significantly improves shear strength and enhances water sealing. Compared with cast-in-place specimens, the prefabricated joint shows a 16.04% lower equivalent viscous damping coefficient during failure due to reinforcement slippage, while achieving 16.34% greater cumulative energy dissipation and 52.00% higher ductility. These findings provide theoretical and experimental support for the broader adoption of prefabricated channels in water conservancy engineering. Full article

In order to investigate the mechanical behavior of a novel pre-tensioned polygonal prestressed T-beam subject to combined bending, shear, and torsion, this study meticulously designed and fabricated a full-scale specimen with a calculated span of 28.28 m, a beam height of 1.8 m, and a top flange width of 1.75 m. A systematic static loading test was conducted. A multi-source data acquisition methodology was employed throughout the experiment. A variety of embedded and external sensors were strategically arranged, in conjunction with non-contact digital image correlation (VIC-3D) technology, to thoroughly monitor and analyze key mechanical performance indicators, including deformation capacity, strain distribution characteristics, cracking resistance, and crack propagation behavior. This study provides valuable insights into the damage evolution process of novel polygonal pre-tensioned T-beams under complex loading conditions. The experimental results indicate that the loading process of the specimen when subjected to combined bending, shear, and torsion, can be divided into two distinct stages: the elastic stage and the crack development stage. Cracks initially manifested at the junction of the upper flange and web at the extremities of the beam and at the bottom flange of the loaded segment. Subsequently, numerous diagonal and flexural–shear cracks developed within the web, while diagonal cracks also commenced to form on the top surface, exhibiting a propensity to propagate toward the support section. Following the appearance of diagonal cracks in the web concrete, both stirrup strain and concrete strain demonstrated abrupt changes. The peak strain observed within the upper stirrups was markedly greater than that measured in the middle and lower regions. On the front elevation of the web, the principal strain peak was concentrated near the connection line between the loading bottom and the upper support. In contrast, on the back elevation of the web, the principal tensile strain was more pronounced near the connection line between the loading top and the lower support. Full article

Modularised wall panels are increasingly used in building and construction. A new double-skin composite (DSC) wall system technology uses clinch seams to combine two roll-formed open section profiles into a hollow steel shell that is then filled with a light-weight concrete foam and can provide a fire-rated DSC solution for use in commercial and high-rise buildings. One important material parameter for the application is the panel performance in wind loading. This study presents a first fundamental analysis of the structural behaviour of the new DSC wall panel relevant to wind loading. For this, 3-point and 4-point bending tests combined with in situ camera analysis are performed and complimented with the analysis of seam strength and the concrete material parameters. The experimental results provide the first experimental evidence that the aerated concrete core material of the DSC panel only has a minor effect on the wall performance in bending. Most of the bending loads are absorbed by the tensile and compressive deformation of the steel outer shell and the shear deformation near the clinch seam. In this way, failure at maximum load is not initiated by concrete cracking but by steel sheet buckling or a mixed failure mode that combines steel buckling and seam opening. Full article

This paper proposes a hybrid steel plate–bolt dry and wet jointing method, where the dry jointing part is a steel plate–bolt connector joint and the wet jointing part is a cast-in-place concrete. The novel precast concrete shear wall (PCW) combines the advantages of both dry and wet connections. A steel plate–bolt dry–wet hybrid connection shear wall model was developed using the finite element method, and a low circumferential reciprocating load was applied to the PCW. By analyzing the force and deformation characteristics of the wall, the results showed that the failure mode of novel PCWs was bending-shear failure. Compared to the concrete wall (CW), the yield load, peak load, and ductile displacement coefficient were 6.55%, 7.56%, and 21.49% higher, respectively, demonstrating excellent seismic performance. By extending the wall parameters, it was found that the increased strength of the novel PCW concrete slightly improved the load-bearing capacity, and the ductility coefficient was greatly reduced. As the axial compression ratio increased from 0.3 to 0.4, the wall ductility decreased by 22.85%. Increasing the reinforcement rate of edge-concealed columns resulted in a severe reduction in ultimate displacement and ductility. By extending the connector parameters, it was found that there was an increased number of steel joints, a severe reduction in ductility, enlarged distribution spacing, weld hole plugging and bolt yielding, reduced anchorage performance, and weakening of the steel plate section, which reduced the load-bearing capacity and initial stiffness of the wall, with little effect on ductility. Full article

Despite the widespread use of precast concrete segmental bridges (PCSBs), concerns persist regarding their structural reliability, particularly due to the interruption of longitudinal reinforcement at joints. To address this, a novel approach based on the Grid Shear Reinforcement Theory is proposed, featuring precast segmental beams with continuous longitudinal reinforcements across joints. Experimental tests were conducted on one monolithic beam and two segmental beams under combined bending and shear with joint types as the primary variable. Key performance metrics included crack propagation, reinforcement strain, failure modes, stiffness, and load-bearing capacity. Results show that continuous longitudinal reinforcement effectively resists axial tension from shear forces, contributing to shear resistance comparable to stirrups. It also restrains diagonal crack propagation and limits main crack widths, significantly improving shear stiffness. Reinforced joints adhered to the plane section assumption and exhibited monolithic beam behavior throughout loading. These findings highlight the critical role of continuous longitudinal reinforcement in segmental beam joints. The study further compares shear reinforcement design approaches in European Codes, ACI, AASHTO, GB, JTC, and the Grid Shear Reinforcement Theory. Practical construction methods for implementing continuous longitudinal reinforcements are also proposed, offering valuable insights for engineering applications. Full article

The synergistic application of ultra-high-performance concrete (UHPC) and bamboo scrimber provides innovative solutions for sustainable structural engineering. In this study, the structural response mechanism of the combined beams under the steel plate–screw composite connection system was systematically investigated by designing three shear connection gradient specimens (TS200/300/400) to address the key scientific issues of the mechanical behavior of the bamboo–UHPC interface. Based on the unidirectional compression tests of bamboo–UHPC composite shear connections and four-point bending tests of composite beams, the damage modes, load-mid-span deflection relationship, bending stiffness, bamboo–UHPC slip and normal lift were evaluated for all the composite beams with the shear connection gradient as a parameter. The results showed that the flexural performance of the composite beams went through three stages: elastic behavior, damage development and final damage. The interfacial slip and interfacial lift-off have more obvious asymmetric spatial distribution characteristics, and increasing the shear joint degree can delay the separation between the UHPC and the bamboo layer, thus enhancing the structural integrity. Typical features of the final damage are the bending damage of ultra-high-performance concrete and bamboo fiber damage. This study highlights the potential of UHPC–bamboo composite beams for sustainable construction and emphasizes the importance of optimizing shear connection for improved performance. Full article

This study investigates the dynamic response of large-diameter monopile foundations subjected to ice loads, emphasizing sustainable design in cold-region offshore wind energy development. Through a combined ice–structure–soil model test and subsequent development of a three-dimensional ice–OWT–soil system model using Abaqus software 2022, this research addresses the sustainability of infrastructure exposed to harsh environmental conditions. The dynamic ice loads are simulated using the coupled CEM–FEM approach, while the Mohr–Coulomb model calculates soil–structure interactions. The calibration and verification processes include comparisons of simulated ice forces, ice-crushing processes, and pile deflections with experimental results. This study comprehensively assesses the effects of ice velocity and thickness on ice actions, as well as the monopile’s top displacement, shear force, and bending moment. The findings indicate that ice thickness significantly influences the dynamic response more than ice velocity, guiding the design toward more sustainable and resilient offshore wind infrastructures. Additionally, a semi-empirical calculation method incorporating the aspect ratio effect is proposed, enhancing the predictive accuracy and sustainability of large-diameter monopile foundations, as validated against field monitoring data from the Norströmsgrund lighthouse. Compared to traditional ice pressure calculation methods, the proposed approach focuses on the influence of the aspect ratio of large-diameter monopile foundations, enabling a more realistic and objective assessment of ice load calculations for OWTs in cold regions. The results demonstrate the efficacy of the proposed approach and offer a new perspective for the design of OWT structures under ice loads. Full article

Connecting diaphragm walls as permanent components of underground spaces in relation to basement sidewalls is an effective method for enhancing structural stability, reducing structural footprint, and improving waterproofing performance. To investigate the influence of connection methods between diaphragm walls and sidewalls on the mechanical performance of combined walls and to determine the differences in mechanical behavior between combined and composite walls, four–point bending experiments were conducted based on static loading systems and digital imaging technology. The cracking characteristics, strain response, load–bearing capacity, displacement ductility, and interface mechanical behavior of a combined wall with interface roughening and rebar anchoring, a combined wall with shear grooves, and a composite wall with a high–density polyethylene waterproof layer were comparatively analyzed. The results showed that for the combined walls with interface roughening and rebar anchoring or with shear grooves, through–thickness cracks extended across the interface, with no interfacial slipping failure observed. The combined wall with shear grooves exhibited noticeable through–thickness cracks. For the composite wall, cracks were staggered on both sides of the interface, with significant interface slipping failure. Compared to the composite wall, the combined walls demonstrated superior overall performance with fewer cracks. Additionally, the load–bearing capacity and displacement ductility of the combined wall with interface roughening and rebar anchoring were significantly higher than those of the combined wall with shear grooves and the composite wall. The composite wall exhibited the lowest load–bearing capacity, while the combined wall with shear grooves demonstrated the least displacement ductility. Full article

Micropiles are a new type of retaining structure widely used in slope engineering due to their small footprint, low vibration and noise emissions, and simple construction process. This study aims to investigate the dynamic response and failure mechanisms of micropiles used in retaining accumulation landslides under seismic loading through shaking table tests and numerical simulation. The failure process, observed phenomena, and bending moments of micropiles in the test were discussed, and the shear force distribution of micropiles was thoroughly analyzed based on numerical simulation. The findings reveal that the natural frequency of the entire landslide system exhibits a gradual decrease and tends to stabilize under sustained earthquake excitation. The bending moment of micropiles follows an “S” shape, with a larger magnitude at the top and a smaller one at the bottom. Additionally, the shear force distribution exhibits a “W-shaped” pattern. Damage to micropiles mainly includes the flexural shear combination failure at the load-bearing section (which occurs within 1.4–3.6 times the pile diameter above the sliding surface) and the shear failure near the sliding surface. This study provides significant insights into the strengthening mechanisms of micropiles under seismic action and offers valuable guidance for the design of slope support. Full article

This paper tests the capability of a simplified model to predict major trends in the dynamic structural response of monopile offshore wind turbines. For this purpose, the results of two numerical models of different levels of complexity are compared: the advanced time-domain multi-physics tool OpenFAST and a simplified static-equivalent model based on beam elements and concentrated masses. The IEA-15-240-RWT reference wind turbine is considered as a benchmarking problem. The comparison between the two structural models is presented in terms of their fundamental frequencies and through the analysis of shear forces and bending moments under wind-only and combined wave and wind load scenarios. The results show that the simplified model can adequately represent the system’s mass and stiffness characteristics, as well as the impact of soil–structure interaction effects on its fundamental frequency. Turbulence and wind velocity have a significant impact on internal forces and on the ability of the simplified model to reproduce their values. Despite the large differences obtained for highly turbulent scenarios, the acceptable accuracy obtained for relevant load scenarios and the conservative nature of the simplified model make it a viable option for preliminary large-scale studies that prioritize efficiency and efficacy over high-precision. Full article

The integration of cutting-edge technologies into reinforced concrete (RC) design is reshaping the construction industry, enabling smarter and more sustainable solutions. Among these, machine learning (ML), a subset of artificial intelligence (AI), has emerged as a transformative tool, offering unprecedented accuracy in prediction and optimization. This study investigated the flexural behavior of steel rebar RC beams, focusing on varying concrete compressive strengths via theoretical, experimental and ML analysis. Nine steel rebar RC beams with low (SC20), moderate (SC30) and high (SC40) concrete compressive strength, measuring 150 × 200 × 1100 mm, were produced and subjected to three-point bending tests. An average error of less than 5% was obtained between the theoretical calculations and the experiments of the ultimate load-carrying capacity of reinforced concrete beams. By combining three-point bending experiments with ML-powered prediction models, this research bridges the gap between experimental insights and advanced analytical techniques. A groundbreaking aspect of this work is the deployment of 18 ML regression models using Python’s PyCaret library to predict deflection values with an impressive average accuracy of 95%. Notably, the K Neighbors Regressor and Gradient Boosting Regressor models demonstrated exceptional performance, providing fast, consistent and highly accurate predictions, making them an invaluable tool for structural engineers. The results revealed distinct failure mechanisms: SC30 and SC40 RC beams exhibited ductile flexural cracking, while SC20 RC beams showed brittle shear cracking and failure with sudden collapse. Full article

To achieve the assembled connection between dovetail profiled steel sheets and the boundary members in dovetail profiled steel concrete composite shear walls (DPSCWs), self-tapping screws were employed. Three DPSCW specimens connected with self-tapping screws were tested under combined axial and cyclic lateral loads to evaluate their hysteretic response, focusing on the influence of the number of self-tapping screws and the axial compression ratio. The self-tapping screw-connected DPSCWs exhibited a mixed failure mode, characterized by shear failure of the profiled steel sheets and compression-bending failure of multiple wall limbs divided by ribs on the web concrete. Except for slight deformation at the screw holes located on the profiled sheets at the corners of the wall, the connections exhibited minimal visible damage. The yield drift ratio of the DPSCW specimens in the test ranged from 1/286 to 1/225, and the ultimate drift ratio ranged from 1/63 to 1/94, both meeting the relevant deformation standards specified in the “Code for Seismic Design of Buildings. Increasing the number of self-tapping screws enhanced the development of local tensile fields on the profiled steel sheets, thereby improving the wall’s load-carrying, deformation, and energy dissipation capacities. However, increasing the axial compression ratio improved the initial stiffness of DPSCWs but reduced their load bearing and deformation capacity. Moreover, a design method for the self-tapping screw connections in DPSCWs was proposed. Full article