Search Results (2,105)

On 7 January 2025, at Beijing time, an M_w7.1 earthquake occurred in Dingri County, Shigatse, Tibet. To accurately determine the fault that caused this earthquake and understand the source mechanism, this study utilized Differential Interferometric Synthetic Aperture Radar (DInSAR) technology to process Sentinel-A data, obtaining the line-of-sight (LOS) co-seismic deformation field for this earthquake. This deformation field was used as constraint data to invert the geometric parameters and slip distribution of the fault. The co-seismic deformation field indicates that the main characteristics of the earthquake-affected area are vertical deformation and east-west extension, with maximum deformation amounts of 1.6 m and 1.0 m for the ascending and descending tracks, respectively. A Bayesian method based on sequential Monte Carlo sampling was employed to invert the position and geometric parameters of the fault, and on this basis, the slip distribution was inverted using the steepest descent method. The inversion results show that the fault has a strike of 189.2°, a dip angle of 40.6°, and is classified as a westward-dipping normal fault, with a rupture length of 20 km, a maximum slip of approximately 4.6 m, and an average slip angle of about −82.81°. This indicates that the earthquake predominantly involved normal faulting with a small amount of left–lateral strike–slip, corresponding to a moment magnitude of M_w7.1, suggesting that the fault responsible for the earthquake was the northern segment of the DMCF (Deng Me Cuo Fault). The slip distribution results obtained from the finite fault model inversion show that this earthquake led to a significant increase in Coulomb stress at both ends of the fault and in the northeastern–southwestern region, with stress loading far exceeding the earthquake triggering threshold of 0.03 MPa. Through analysis, we believe that this Dingri earthquake occurred at the intersection of a “Y”-shaped structural feature where stress concentration is likely, which may be a primary reason for the frequent occurrence of moderate to strong earthquakes in this area. Full article

The structural integrity of offshore wind turbine monopiles is critical for ensuring operational stability and long-term performance under varying environmental and aerodynamic loads. However, transient load conditions during different operational phases, such as start, normal stop, and emergency stop, can significantly impact structural behavior, influencing fatigue life and dynamic stability. This study investigates the dynamic structural response of a 15 MW offshore wind turbine monopile, incorporating modal analysis and transient simulations to assess deflection, forces, moments, and rotational displacements at the mud-line. The modal analysis revealed natural frequencies of 0.509492 Hz, 1.51616 Hz, and 3.078425 Hz for the blade’s flap-wise modes, while side-to-side modes for the combined tower and monopile structure were identified at 0.17593 Hz, 0.922308 Hz, and 1.650862 Hz. These frequencies are crucial in evaluating resonance risks and ensuring dynamic stability under combined aerodynamic and hydrodynamic forces. The transient analysis demonstrated that lateral force (F_y) variations peaked at −2500 kN during emergency stop, while moment fluctuations (My) reached ±100,000 kNm, reflecting the monopile’s high dynamic sensitivity under sudden aerodynamic unloading. Rotational displacements also showed significant variations, with θx oscillating up to ±0.0009 degrees and θy between −0.0022 and −0.0027 degrees. These findings provide valuable insights into optimizing monopile design to mitigate resonance effects, improve fatigue performance, and enhance structural resilience for large-scale offshore wind turbine support systems. Full article

In order to improve the technical economy of steel-reinforced concrete structures and to promote the development of prefabricated concrete structures, a new type of partial precast steel-reinforced concrete column (precast stratified concrete composite column with inserted steel tube, PSCCST column) was proposed and studied in this paper. Six PSCCST column specimens were tested to investigate their behavior under eccentric loading. The failure state, ultimate bearing capacities, load–strain relationship, as well as load-deflection curves were emphatically investigated. The failure modes of the PSCCST columns under eccentric compression and corresponding bearing capacity N_u calculation methods were proposed based on experimental research and analysis. The results of the study indicated that there are three main failure modes, which are compressive-type failure mode, total-yield-type failure mode, and tensile-type failure mode. The first two modes are preferable due to their more effective material utilization. The N_u of the PSCCST column was found to decrease obviously with the increase of eccentricity e. The deformation capacity denoted by the horizontal lateral deflection corresponding to N_u increased with the increase of e. Moreover, the proposed N_u calculation methods were proven to have high accuracy by the comparison with the experimental results (the average ratio of the calculated values to the experimental values was 0.95). Full article

Concrete-filled steel tube (CFT) columns are increasingly used in high-rise structures due to their improved resilience to lateral loads. However, the behavior of multi-cell CFT columns, connected with different tie bar spacings, has been under-considered. This study aims to investigate the performance of simple and four-cell CFT columns with tie bars at different spacings. Seven columns with different tie bar spacings (100, 300, and 500 mm) were examined under axial compression. The load–displacement curve, failure pattern, and concrete core failure characteristics were described. A calculation model for the axial pressure field of simple and four-cell CFT columns with tie bars at varying spacings was constructed using a finite element analysis software. The results showed that the axial compression load capacity of confined CFT columns was significantly higher in four-cell composite specimens, where the capacity increased by 15.6% and 33% with tie bar spacings of 500 mm and 300 mm, respectively. Also, compared to simple CFT specimens, the capacity increased by 14.7%, 27.8%, and 42.6% with tie bar spacings of 100 mm, 300 mm, and 500 mm, respectively. Full article

Flight tests and wind tunnel experiments face difficulties in investigating the impact of aircraft carrier air-wake on the landing process. Meanwhile, numerical methods generally exhibit low overall computational efficiency in solving such problems. To address the computational challenges posed by the disparate spatiotemporal scales of the ship air-wake and aircraft motion, a domain precursor inflow method is developed to efficiently generate unsteady inflow boundary conditions from precomputed full-domain air-wake simulations. This study investigates the aerodynamic variability of carrier-based aircraft during landing through the turbulent air-wake generated by an aircraft carrier, employing a hybrid RANS-LES methodology on dynamic unstructured overset grids. The numerical framework integrates a delayed detached-eddy simulation (DDES) model with a parallel dynamic overset grid approach, enabling high-fidelity simulations of coupled aircraft carrier interactions. Validation confirms the accuracy of the precursor inflow method in reproducing air-wake characteristics and aerodynamic loads compared to full-domain simulations. Parametric analyses of 15 distinct landing trajectories reveal significant aerodynamic variability, particularly within 250 m of the carrier, where interactions with island-generated vortices induce fluctuations in lift (up to 25%), drag (18%), and pitching moments (30%). Ground effects near the deck further amplify load variations, while lateral deviations in landing paths generate asymmetric forces and moments. The proposed methodology demonstrates computational efficiency for multi-scenario analysis, providing critical insights into aerodynamic uncertainties during carrier operations. Full article

Shells are significant structural components that are extensively utilized in numerous engineering fields, including architectural and infrastructural projects. These components are employed in the construction of domes, water tanks, stadiums and auditoriums, hangars, and cooling towers. Significant research efforts have been dedicated to the analysis of vibrations and dynamic behaviors of shells, due to their distinctive capacity to efficiently bear loads through their geometry rather than mass. Additionally, a vast array of shell theories and computational methods have been proposed and developed by researchers. This paper represents a continuation of research initiated begun in a 2009 paper by Elishakoff, wherein the suggestion was made to disregard an energetic term in the dynamic analysis of Timoshenko–Ehrenfest beams, wherein the suggestion was made to disregard an energetic term in the dynamic analysis of Timoshenko–Ehrenfest beams. The resulting reduced theory was found to be both more straightforward and more reliable than the complete, classical approach. While the original idea was heuristically justified, a more sound variationally consistent theory was proposed in the papers of De Rosa et al. concerning the dynamic analysis of the Timoshenko-Ehrenfest beams and later extended to the case of the Uflyand-Mindlin plates. In accordance with the proposal put forth in those works, we initially delineate the classical shell theory and subsequently propose two alternative hypotheses that give rise to two distinct aspects of the energy terms. By employing the variational approach, we derive two novel boundary problems, which are direct generalizations of those previously considered. Both theories can be readily specialized for beams and plates, and the theory can also be specialized for the case of cylindrical shells. Full article

In the field of liquid composite moulding (LCM) simulations, a long-standing assumption has dominated–the belief in constant resin viscosity. While effective in many cases, this assumption may not hold for the infusion process, which lasts for an extended period. This impacts the mechanical properties of the cured epoxy, which are crucial for load transfer in polymer structures. The majority of epoxy resins operate on a bipartite foundation, wherein their viscosity undergoes dynamic alterations during the process of cross-linking. Temperature and cross-linking intricately interact, with elevated temperatures initially reducing viscosity due to kinetic energy but later increasing it as cross-linking accelerates. This interplay significantly influences the efficiency of the infusion process, especially in large and intricate moulds. This article explores the significant temperature dependence of epoxy resin viscosity, proposing an accurate model rooted in its non-linear evolution. This model aligns with empirical evidence, offering insights into determining the optimal starting temperature for efficient mould filling. This study presents an advanced infusion model that extends existing non-linear dual-split viscosity approaches by incorporating the experimental validation of viscosity variations. Unlike previous models that primarily focus on theoretical or numerical frameworks, this work integrates experimental insights to optimize infusion temperature for efficient resin infusion in large and complex parts. Building on these findings, a novel mould-filling technique is proposed to enhance efficiency and reduce material waste. Full article

The traditional Malay house is a significant component of the Malay cultural heritage and a key example of vernacular architecture. It is characterised by its outstanding design and the various styles across Malaysia. Traditional Malay houses experience deterioration and damage due to various threats, resulting in many houses being abandoned. A thorough structural evaluation is crucial for preserving the traditional Malay house. This research aimed to develop guidelines for the global structural evaluation of the Malay house. A case study approach was adopted in this research. Site visits, visual surveys, geometrical surveys, and dilapidation surveys were also employed. The research involved structural analysis using SAP2000. The results revealed the vulnerability of the houses to lateral forces, sliding, and differential settlement under scouring. The key structural members have adequate load-bearing capacity, which might be compromised under certain conditions, as in the case of deterioration. These results helped identify potential safety concerns and led to the development of guidelines for the global structural evaluation of Malay houses. The guidelines cover analysis inputs and modelling techniques in terms of material, geometry, joints, and foundations. They address load criteria and the impacts of flooding and scouring on the structural behaviour of the traditional Malay house. The guidelines, finally, recommend that structural checks be considered. This research contributes to traditional Malay house preservation by providing an evidence-based approach to designing preservation measures. Full article

Background: The objective of this study was to compare the outcomes between patients undergoing mechanically aligned conventional total knee arthroplasty (MA-CTKA) and functionally aligned robotic-arm-assisted TKA (FA-RTKA). Methods: We reviewed a prospectively collected database of consecutive patients who underwent primary total knee arthroplasty (TKA) for knee osteoarthritis between June 2022 and May 2023. Patients were divided into two groups—MA-CTKA (n = 50) and FA-RTKA (n = 50)—based on the introduction of a robotic-arm-assisted system during the study period. The hip–knee–ankle (HKA) angle, joint line orientation angle (JLOA) relative to the floor, and weight-bearing line (WBL) ratio were evaluated using full-length standing hip-to-calcaneus radiographs to compare the conventional mechanical axis (MA) and the ground mechanical axis (GA) passing through the knee joint between the groups. Clinical outcomes were also compared between the two groups. Results: There were no significant differences in the postoperative HKA angle between the groups, due to discrepancies in the targeted alignment strategies (FA-RTKA: 2.0° vs. MA-CTKA: 0.5°; p = 0.001). The postoperative JLOA in the FA-RTKA group was more parallel to the floor, whereas the MA-CTKA group showed a downward angulation toward the lateral side (0.6° vs. −2.7°; p < 0.001). In the FA-RTKA group, the GA passed through a neutral position when accounting for the calcaneus, while the MA-CTKA group showed a more lateral GA position (48.8% vs. 53.8%; p = 0.001). No significant differences in clinical outcomes were shown between the FA-RTKA and MA-CTKA groups, with the FA-RTKA group demonstrating higher Forgotten Joint Scores and a greater range of motion (all p < 0.05). Conclusions: Functionally aligned TKA demonstrated improved joint line parallelism to the floor and more neutral weight-bearing alignment in the GA compared to mechanically aligned TKA. These findings indicate a more balanced load distribution across the knee, which may contribute to the superior clinical outcomes observed in the functionally aligned group. Full article

Considering the influence of high-speed obstacle avoidance trajectory in the optimization design stage of intelligent bus aerodynamic shape. A collaborative optimization method aiming at aerodynamic structure and trajectory control system for intelligent bus rollover stability is proposed to reduce the interference of lateral aerodynamic load caused by large bus side area on driving stability and improve the rollover safety of intelligent bus in high-speed obstacle avoidance process. At the conceptual design stage, a multidisciplinary co-design optimization frame of aerodynamics/dynamics/control is built, and an adaptive Gaussian Process Regression approximate modeling method is proposed to establish an approximate model of high-precision and high-efficiency rollover evaluation index with rollover stability as the optimization objective and obstacle avoidance safety and resistance to crosswind interference as constraints. Taking rollover stability and obstacle avoidance safety as the optimization objectives, the integrated design of static structural parameters and dynamic control parameters of intelligent buses is carried out. The results show that the proposed MDO method can obtain the aerodynamic shape of the vehicle body with low crosswind sensitivity and a safe and stable obstacle avoidance trajectory. Compared with the initial trajectory, the peak lateral load transfer rate during the obstacle avoidance process decreases by 33.91%, which significantly reduces the risk of rollover. Compared with the traditional serial optimization method, the proposed co-design optimization method has obvious advantages and can further improve the driving safety performance of intelligent buses. Full article

In order to study the horizontal bearing characteristics of large-diameter rock-socketed rigid pile and flexible pile, two lateral loading tests in which the pile lengths are 5.2 m and 11.07 m were carried out. Unidirectional multi-cyclic loading was applied to the piles during the tests, with the maximum load reaching 3500 kN. The measured results are compared with the calculated results of Zhang’s method, m-method and the rigid pile method in the design codes. It is indicated that if the characteristic values of the horizontal bearing capacity of the large-diameter rock-socketed rigid pile and flexible pile are determined by the same horizontal displacement of the pile head, some risk will be brought to the design of the rigid pile. Compared with the rigid pile method, the m-method is more suitable for calculating the rotation angle of the pile head. In terms of the maximum bending moment of the large-diameter rock-socketed flexible pile under the critical load, the calculated result of Zhang’s method is less than the measured result, while the calculated result of the m-method is the largest. However, for the rigid pile, both Zhang’s method and m-method underestimate the maximum bending moment of the pile body. In summary, when a large-diameter rock-socketed pile is designed, reasonable calculation method and failure discrimination standard should be chosen according to the actual conditions. Full article

Fatigue causes the lower limb to land in an injury-prone state, but the underlying neuromuscular control changes remain unclear. This study aims to investigate lower limb muscle synergies during landing in basketball players, both before and after fatigue, to examine alterations in neuromuscular control strategies induced by fatigue. Eighteen male recreational basketball players performed landing tasks pre- and post-fatigue induced by 10 × 10 countermovement jumps. Electromyographic (EMG) data from eight muscles, including the erector spinae (ES), rectus abdominus (RA), gluteus maximus (GM), rectus femoris (RF), biceps femoris (BF), lateral gastrocnemius (LG), soleus (SM), and tibialis anterior (TA) muscles, were analyzed using non-negative matrix factorization to extract muscle synergies. Post-fatigue results revealed significant changes: synergy primitive 1 decreased before landing (18–30% phase) and synergy primitive 2 decreased after landing (60–100% phase). Muscle weights of the LG and SM in synergy module 2 increased. Fatigue reduced synergistic muscle activation levels, compromising joint stability and increasing knee joint loading due to greater reliance on calf muscles. These changes heighten the risk of lower limb injuries. To mitigate fatigue-induced injury risks, athletes should improve thigh muscle endurance and enhance neuromuscular control, fostering better synergy between thigh and calf muscles during fatigued conditions. Full article

Timber construction experiences a growing trend in different countries due to its inherent environmental benefits and proven lateral load performance. However, most of the previous studies on structural and seismic performance have focused on undamaged structures without any signs of deterioration. This paper focuses on the analysis of the effects of the initial damage state on the seismic response and fragility of a five-story CLT building designed under a force-based approach. A detailed 3D finite element model was developed and validated through experimental data in order to perform incremental dynamic analyses that considered different arbitrarily imposed initial damage states. The residual response and the fragility functions are analyzed to characterize the impact of the initial state on seismic behavior. The results of this work highlight the need to properly consider the effect of previous load actions for the seismic performance evaluation during the operating life of CLT structures. Findings suggest that the initial state can significantly modify the probability of reaching a given limit state. Moreover, it was found that if the initial damage is defined as severe, the collapse margin ratio is reduced by 58.8% compared to the case in which the initial state is undamaged. Full article

This paper presents a dual-loop control system designed for three-level three-phase T-type converters, optimizing their performance in the hybrid operation of Power-to-X systems. Due to the increasing of distributed power generation based on renewable energy sources, Power-to-X systems convert surplus renewable energy into other forms of energy, such as hydrogen, synthetic fuels, or chemical storage, which can be stored and later converted back to electricity or used in other applications. Bidirectional converters play a crucial role in hybrid system operation, which requires an efficient and reliable power conversion to maintain stability and performance. The proposed dual-loop control system includes an inner current loop for fast current regulation and an outer voltage loop to maintain stable voltage levels, ensuring precise control of the output of the converter and enhancing its response to dynamic changes in load and generation. Additionally, the control system incorporates a technique to balance the split DC-link capacitors voltages, a major challenge in three-level converters. Comprehensive simulation and experimental results demonstrate the efficacy of the proposed control system in maintaining high power quality and supporting the hybrid operation of Power-to-X systems. Full article

Background/Objectives: The Agenesis of maxillary lateral incisors occurs with a variable prevalence in different ethnic groups, and there is a need for a temporary replacement until maturity has been reached in patients for whom the replacement solution has been chosen. This study aims to analyze the scientific evidence available to date concerning the use of mini-screw implant (MSI)-supported pontics for the transitional management of permanent maxillary lateral incisors’ agenesis in developmental age subjects. Methods: Electronic research was conducted using four databases: PubMed, Clarivate Analytics/Web of Science Core Collection, Scopus, and the Wiley/Cochrane Library. Six studies were included in the final review. Data were extracted based on the first and second author, year of publication, study design, sample characteristics, mini-screw implant (MSI) characteristics, MSI insertion and loading protocol, characteristics of the prosthetic component, and outcomes during the follow-up time. Results: Clinical outcomes were proven positive in all studies. In only one study did MSIs show mobility and consequent failure after one month. Discoloration of the prosthetic part proved to be the main complication. Conclusions: The comparison with conventional removable prostheses and fixed dental prostheses revealed that MSI-supported pontics are a viable alternative and a promising temporary solution until the end of growth. Further studies to standardize protocols and assess long-term outcomes are needed. Full article