Search Results (1,306)

Suspension bridges, as a type of long-span bridge, usually have a larger longitudinal displacement at the end of the beam (LDBD). LDBD can be used to evaluate the safety of bridge components at the end of the beam. However, due to factors such as sensor failure and system maintenance, LDBD in the bridge health monitoring system is often missing. Therefore, this study reconstructs the missing part of LDBD based on the long short-term memory network (LSTM) and various data. Specifically, first, the monitoring data that may be related to LDBD in a suspension bridge is analyzed, and the temperature and beam end rotation angle data (RDBD) at representative locations are selected. Then, the temperature data at different places of the bridge are used as the input of the LSTM model to compare and analyze the prediction effect of LDBD. Next, RDBD is used as the input of the LSTM model to observe the prediction effect of LDBD. Finally, temperature and RDBD are used as the input of the LSTM model to observe whether the prediction effect of the LSTM model is improved. The results show that compared with other parts of the bridge, the prediction effect of the temperature inside the box girder in the main span as the model input is better; when RDBD is used as the input of the LSTM model, it is better than the prediction effect of temperature as the model input; temperature and RDBD have higher prediction accuracy when used as the input of the LSTM model together than when used separately as the input of the LSTM model. Full article

Articulated Tugs and Barges (ATBs) are increasingly recognised for their effectiveness in transporting chemicals, petroleum, bulk goods, and containers, primarily due to their exceptional flexibility and fuel efficiency. Recent projections indicate that the ATB market is on track for significant growth, which is expected to lead to an increase in the annual growth rate from 2025 to 2032. This study aims to analyse the current advancements in ATB technology and provide insights into the ATB fleet and the systems that connect tugboats and barges. Furthermore, it highlights the advantages of this transportation system, especially regarding its role in enhancing energy efficiency within the maritime transport sector. Currently, there is limited information available in the public domain about ATBs compared to other commercial vessels. The analysis reveals that much of the required information for modern ATB design is not accessible outside specialised design companies. The study also focuses on conceptual design aspects, which include the main dimensions, articulated connections, propulsion systems, and machinery, concluding with an evaluation of economic viability. Special emphasis is placed on defining the main dimensions, which is a critical part of the complex design process. In this context, the ratios of length to beam (L/B), beam to draft (B/D), beam to depth (B/T), draft to depth (T/D), and power to the number of tugs cubed (Pw/N³) are established as design control parameters in the conceptual design phase. This aspect underscores the novelty of the present study. Additionally, the economic viability is analysed in terms of both CAPEX (capital expenditures) and OPEX (operational expenditures). While CAPEX does not significantly differ between the methods used in different types of commercial ships, OPEX should account for the unique characteristics of ATB vessels. Full article

Convective updrafts are one of the main characteristics of convective clouds, responsible for the convective mass flux and the redistribution of energy and condensate in the atmosphere. During the early stages of their lifecycle, convective clouds experience rapid cloud-top ascent manifested by a decrease in the geostationary IR brightness temperature ($T{B}_{IR}$). Under the assumption that the convective cloud top behaves like a black body, the ascent rate of the convective cloud top can be estimated as (${\displaystyle \frac{\partial T{B}_{IR}}{\partial t}}$), and it can be used to infer the near cloud-top convective updraft. The temporal resolution of the geostationary IR measurements and non-uniform beam-filling effects can influence the convective updraft estimation. However, the main shortcoming until today was the lack of independent verification of the strength of the convective updraft. Here, Doppler radar observations from the ESCAPE and TRACER field experiments provide independent estimates of the convective updraft velocity at higher spatiotemporal resolution throughout the convective core column and can be used to evaluate the updraft velocity estimates from the IR cooling rate for limited samples. Isolated convective cells were tracked with dedicated radar (RHIs and PPIs) scans throughout their lifecycle. Radial Doppler velocity measurements near the convective cloud top are used to provide estimates of convective updrafts. These data are compared with the geostationary IR and VIS channels (from the GOES satellite) to characterize the convection evolution and lifecycle based on cloud-top cooling rates. Full article

This study focuses on the development of lignin-based carbon-fiber-reinforced laminated veneer lumber (LVL) beams for garden timber structures, addressing wood shortages and environmental concerns. The research consisted of three main phases: the extraction and characterization of the lignin from corn stalks; the preparation and characterization of lignin-based carbon fibers; the fabrication and testing of reinforced LVL beams. Lignin was extracted from corn stalks using a deep eutectic solvent, followed by the preparation of lignin-based carbon fibers through electrospinning. These carbon fibers were integrated with poplar veneers to create reinforced LVL beams. The test results demonstrated significant improvements in mechanical properties, with the reinforced LVL beams exhibiting a 17% increase in elastic modulus and a 30% enhancement in flexural strength compared with conventional LVL beams. Notable improvements were also observed in tensile strength, compressive strength, and shear strength. This research provides a novel approach for producing high-value-added carbon fibers from agricultural waste, advancing the development of sustainable building materials. Full article

Based on the engineering background of a new type of segmental-assembled steel temporary beam buttress, the fatigue strength evaluation method of the steel box girders with open longitudinal ribs was taken as the research objective. The fatigue stress calculation analysis and the full-scale fatigue loading test for the steel box girder local component were carried out. The accuracy of the finite-element model was verified by comparing it with the test results, and the rationality of the fatigue strength evaluation methods for welded joints was deeply explored. The results indicate that the maximum nominal stress occurs at the weld toe between the transverse diaphragm and the top plate at the edge of the loading area, which is the fatigue-vulnerable location for the steel box girder local components. The initial static-load stresses at each measuring point were in good agreement with the finite-element calculation results. However, the static-load stress at the measuring point in the fatigue-vulnerable position shows a certain decrease with the increase in the number of cyclic loads, while the stress at other measuring points remains basically unchanged. According to the finite-element model, the fatigue strengths obtained by the nominal stress method and the hot-spot stress method are 72.1 MPa and 93.8 MPa, respectively. It is reasonable to use the nominal stress S-N curve with a fatigue life of 2 million cycles at 70 MPa and the hot-spot stress S-N curve with a fatigue life of 2 million cycles at 90 MPa (FAT90) to evaluate the fatigue of the welded joints in steel box girders with open longitudinal ribs. According to the equivalent structural stress method, the fatigue strength corresponding to 2 million cycles is 94.1 MPa, which is slightly lower than the result corresponding to the main S-N curve but within the range of the standard deviation curve. The research results of this article can provide important guidance for the anti-fatigue design of welded joints in steel box girders with open longitudinal ribs. Full article

To address the issue of deformation mismatch between the exterior wall panels and the resilient frame structure under large deformations, two novel flexible devices (FDs) with different working principles are proposed in this paper. These FDs enable the exterior wall panels to achieve cooperative deformation with frame columns or beams under horizontal loads, thus improving the seismic performance of the frame structure with additional exterior wall panels. This study begins by explaining the specific design thought of the FDs based on examining the deformation characteristics of frame structures. Then, a series of low-cycle loading tests are conducted on frame specimens to demonstrate the effectiveness of the FDs. The experimental results indicate that the FDs can improve the interaction between the exterior wall panels and the main frame, reduce plastic damage to the wall panels, and increase the peak load-bearing capacity of the overall structure by approximately 17–21%. In addition, a refined finite element modeling method for the proposed FDs is presented using the ABAQUS software, providing a basis for further research on frame structures with additional exterior wall panels. Full article

The main objective of proton beam therapy is to precisely irradiate diseased tissue while minimizing damage to healthy cells. For effective treatment, the linear energy transfer (LET) is a key parameter in ensuring the destruction of diseased cells, and both the dose and LET are typically represented as functions of depth. The distribution of dose and LET in the target depends on the beam properties, including beam energy, energy spread, beam size, and beam emittance. The aim of this work is to present the method used to characterize the proton beam properties obtained from the machine employed in the simulation and to determine the dose and dose-averaged LET (LET_d) values, including their peak positions in depth. These results are used to predict the dose and LET_d at different depth positions under experimental conditions. We utilized GEANT4, a Monte Carlo (MC) simulation-based software, to examine the integral depth-dose position and the peak position of the LET_d. The proton source was obtained from a cyclotron accelerator, specifically the Varian ProBeam Compact spot scanning system at King Chulalongkorn Memorial Hospital in Bangkok, Thailand. The system provides proton energies ranging from 70 MeV to 220 MeV. In this study, four proton energies—70 MeV, 100 MeV, 150 MeV, and 220 MeV—were chosen to characterize the beam properties. The 80%–20% distal fall-off obtained from the simulation was used to determine the energy spread for each selected energy by matching the depth-dose peak with the measurement data. The optimal energy spreads were found to be 1.5%, 1.25%, 1%, and 0.5% for proton energies of 70 MeV, 100 MeV, 150 MeV, and 220 MeV, respectively. These energy spreads ensure that the difference in the depth-dose profile is below 1% when comparing the simulated and measured depth-dose profiles. Furthermore, the peak LET_d was found to be approximately 1 mm away from the R₈₀ position, a depth that corresponds to 80% of maximum dose, for each energy. This information can be used to guide the desired LET_d position by utilizing the R₈₀ depth position. Full article

This study investigates how different longitudinal steel rebars influence the flexural performance and cracking mechanisms of reinforced ultra-high-performance concrete (UHPC) beams, combining axial tensile tests using acoustic emission monitoring with standard four-point bending tests. A series of experimental assessments on the flexural behavior of UHPC beams reinforced with various types of longitudinal reinforcement was conducted. The types of longitudinal reinforcement mainly encompassed HRB 400, HRB 600, and NPR steel rebars. The test results revealed that the UHPC beams reinforced with the three types of longitudinal steel rebar exhibited distinctly different failure modes. Compared to the single dominant crack failure typical of UHPC beams reinforced with HRB 400 steel rebars, the beams using HRB 600 rebars exhibited a tendency under balanced failure conditions to develop fewer main cracks (typically two or three). Conversely, the UHPC beams incorporating NPR steel rebars exhibited significantly more cracking within the pure bending zone, characterized by six to eight uniformly distributed main cracks. Meanwhile, the HRB 600 and NPR steel rebars effectively upgraded the flexural load-bearing capacity and deformation ability compared to the HRB 400 steel rebars. By integrating the findings from the direct tensile tests on reinforced UHPC, aided by acoustic emission source location, this research specifically highlights the damage mechanisms associated with each rebar type. Full article

Drilling oil and gas wells is a complex process that requires a combination of several parameters to dig into the ground. Inappropriate drilling parameter settings and reaction forces can lead to unwanted vibrations, which can negatively impact the drill string and cause damage to drill bits. To reduce unwanted oscillations, drilling vibration modeling is the first approach used to determine the behavior of the drill string under various conditions. Natural frequencies, one of the modal characteristics of a vibrating drill string, can be estimated by analytical or numerical models. However, as the field conditions become more complicated, analytical models become increasingly difficult to use, and alternative approaches must be adopted. The main objective of this paper is to investigate the natural frequencies of drill strings with real geometry under coupled vibration modes using both analytical and finite element methods. This study bridges the literature gap in modeling stepped drill string geometries, which are usually represented as uniform beams. This paper used analytical and finite element models to determine the drill string’s lateral, axial, and torsional natural frequencies under varying lengths of drill pipes and drill collars. To assess the reliability of finite element models under complex geometry, the drill string was approximated as a stepped beam rather than a uniform beam. Then, a comparison was made with analytical models. The results showed that the length of drill pipes has a pronounced effect on the natural frequencies of the overall drill string for the three vibrational modes, while drill collar length only has a notable impact on the torsional mode. These findings contribute to drilling systems’ reliability and efficiency in the oil and gas energy sector. Full article

This study addresses the water basin effect in the underwater sand layer of steel pipe pile cofferdams by integrating the concept from building foundation pits to cofferdam foundation pit analysis. A theoretical derivation is presented for the deformation evolution of steel pipe piles and bottom seals within the cofferdam pit. The cofferdam construction dewatering process is divided into four stages: riverbed excavation for bottom sealing, dewatering to the second support, dewatering to the third support, and dewatering to final bottom sealing. The steel pipe piles are modeled as single-span or multi-span cantilever continuous beam structures. Using the superposition principle, deformation evolution equations for these statically indeterminate structures across the four stages are derived. The bottom seal is simplified to a single-span end-fixed beam, and its deflection curve equation under uniform load and end-fixed additional load is obtained via the same principle. A case study based on the 6# pier steel pipe pile cofferdam of Xi’an Metro Line 10 Jingwei Bridge rail-road project employs FLAC3D for hydrological–mechanical coupling analysis of the entire dewatering process to validate the water basin effect. Results reveal a unique water basin effect in cofferdam foundation pits. Consistent horizontal deformation patterns of steel pipe piles occur across all working conditions, with maximum horizontal displacement (20.72 mm) observed at 14 m below the pile top during main pier construction completion. Close agreements are found among theoretical, numerical, and monitored deformation results for both steel pipe piles and bottom seals. Proper utilization of the formed water basin effect can effectively enhance cofferdam stability. These findings offer insights for similar engineering applications. Full article

This study applied precast engineered cementitious composite (ECC) shells to replace conventional concrete in precast assembled monolithic composite beams to enhance mechanical performance. A new type of precast monolithic ECC composite beam was proposed. Five ECC composite beams and one reinforced concrete (RC) composite beam were designed and fabricated for the experimental study. The failure pattern, failure mechanism, load-bearing capacity, deformability, and stiffness degradation were quantitatively analyzed through the tests. The main findings were as follows: ECC composite beams developed finer and more densely distributed cracks compared to RC composite beams, without significant concrete spalling. The peak load of ECC composite beams was 8.2% higher than that of RC composite beams, while the corresponding displacement at peak load increased by 29.3%. The ECC precast shell delayed crack propagation through the fiber bridging effect. The average load degradation coefficient of the ECC composite beams was 8.2% lower than that of the RC beam. The stiffness degradation curve of ECC composite beams was more gradual than that of RC composite beams, providing an optimization basis for the design of precast beams in structures with high seismic demands. As the shear span ratio increased from 1.5 to 3, the load-bearing capacity decreased by 32.0%. When the stirrup ratio increased from 0.25% to 0.75%, the ultimate load-bearing capacity improved by 28.8%. Furthermore, specimens with higher stirrup ratios showed a 40–50% reduction in stiffness degradation rate, demonstrating that increased stirrup ratio effectively mitigated brittle failure. Full article

The goal of this study is to evaluate how the inclusion of synthetic wax, added in 0.5% increments from 1.5% to 3.5%, affects the characteristics of PMB 45/80-65 (polymer-modified bitumen) during both short-term (RTFOT) and long-term (PAV) aging processes. Tests were carried out to assess the fundamental properties of the binder, leading to the determination of the penetration index (PI) and the plasticity range (PR). The binder’s properties were examined at below-freezing operating temperatures, with creep stiffness measured using a bent beam rheometer (BBR) at −10 °C, −16° C, −22 °C, and −28 °C. The rheological properties of the asphaltenes were evaluated based on both linear and nonlinear viscoelasticity. The experimental study explored temperature effects on the rheological properties of composite materials using a DSR dynamic shear rheometer at 40 °C, 60 °C, and 80 °C over a frequency range of 0.005 to 10 Hz. The main parameters of interest were composite viscosity (η*) and zero shear viscosity (η₀). Viscoelastic parameters, including the dynamic modulus (G*) and phase shift angle (δ), were determined, and Black’s curves were used to illustrate the relationship between these parameters, where G*/sinδ was determined. The MSCR test was employed to investigate the impact of bitumen on the asphalt mixture’s resistance to permanent deformation and to assess the degree and efficacy of asphalt modification. The test measured two parameters, irreversible creep compliance (J_nr) and recovery (R), under stress levels of 0.1 kPa (LVE) and 3.2 kPa (N-LVE). The Christensen–Anderson–Marasteanu model was used to describe the bitumen behavior during binder aging, as reflected in the rheological study results. Ultimately, this study revealed that synthetic wax influences the rheological properties of PMB 45/80-65 polymer bitumen. Specifically, it mitigated the stiffness reduction in modified bitumen caused by polymer degradation during aging at an amount less than 2.5% of synthetic wax. Full article

Timber–steel hybridisation offers a balanced approach by capitalising on the high strength-to-weight ratio and sustainability of the timber while also benefiting from the high stiffness and ductility of the steel, contributing to the improved performance of hybrid structural elements. This paper reviews key aspects of timber–steel hybridisation, with a particular emphasis on the connection methods between timber and steel, including adhesive bonding and mechanical fastening, as well as the different types of reinforcement configurations. In particular, this review covers two main types of adhesives used in timber–steel hybrid systems, namely, epoxy and polyurethane, and two primary types of mechanical fasteners, namely, bolts and screws. The mechanical performances of all hybridisation methods are reviewed. The importance of surface treatments, such as shot blasting for steel and mechanical abrasion for timber, is also discussed as a key factor in optimising adhesive bonds. Furthermore, various reinforcement configurations, including top, bottom, side, and embedded arrangements, are evaluated for their impact on the structural efficiency and fire performance. To support this evaluation, calculations have been carried out to illustrate how different reinforcement configurations influence the stress distribution in timber–steel hybrid beams. By providing detailed insights into these critical aspects, this paper serves as a valuable decision-making tool, offering guidance for researchers and industry professionals for selecting the appropriate bonding techniques and configurations to meet specific structural objectives and advance sustainable construction practices. Full article

In this paper, a new approach to topology optimization using the parameterized level set function and genetic algorithm optimization methods is presented. The impact of a number of parameters describing the level set function in the representation of the model was examined. Using the B-spline interpolation function, the number of variables describing the level set function was decreased, enabling the application of evolutionary methods (genetic algorithms) in the topology optimization process. The traditional level set method is performed by using the Hamilton–Jacobi transport equation, which implies the use of gradient optimization methods that are prone to becoming stuck in local minima. Furthermore, the resulting optimal shapes are strongly dependent on the initial solution. The proposed topology optimization procedure, written in MATLAB R2013b, utilizes a genetic algorithm for global optimization, enabling it to locate the global optimum efficiently. To assess the acceleration and convergence capabilities of the proposed topology optimization method, a new genetic algorithm penalty operator was tested. This operator addresses the slow convergence issue typically encountered when the genetic algorithm optimization procedure nears a solution. By penalizing similar individuals within a population, the method aims to enhance convergence speed and overall performance. In complex examples (3D), the method can also function as a generator of good initial solutions for faster topology optimization methods (e.g., level set) that rely on such initial solutions. Both the proposed method and the traditional methods have their own advantages and limitations. The main advantage is that the proposed method is a global search method. This makes it robust against entrapment in local minima and independent of the initial solution. It is important to note that this evolutionary approach does not necessarily perform better in terms of convergence speed compared to gradient-based or other local optimization methods. However, once the global optimum has been found using the genetic algorithm, convergence can be accelerated using a faster local method such as gradient-based optimization. The application and usefulness of the method were tested on typical 2D cantilever beams and Michell beams. Full article

In this work, we address the task of monitoring Powder Bed Fusion–Laser Beam processes for metal powders (PBF-LB/M). Two main contributions with practical merit are presented. First, we consider the comparison between a large deep neural network (VGG-19) and a small model consisting of, among others, four convolutional layers. Our study shows that the small model can compete favorably with the big model, which takes advantage of transfer learning techniques. Secondly, we present a filtering method using a semantic segmentation approach to preselect a region for the classification algorithm. The region is selected based on post-exposure images, and preselection can be easily adopted for any machine independently of the software used for the translation of process input files. To consider the task, a master dataset with over 260,000 samples was prepared, and a detailed process of preparing the training datasets was described. The study demonstrates that the classification time can be reduced by a factor of 4.51 while still maintaining the model’s necessary performance to detect errors in a PBF-LB process. Full article