Hasil untuk "Bridge engineering"

M. Geers, V. Kouznetsova, W. Brekelmans

R. Esteban, A. Borisov, P. Nordlander et al.

Electromagnetic coupling between plasmonic resonances in metallic nanoparticles allows for engineering of the optical response and generation of strong localized near-fields. Classical electrodynamics fails to describe this coupling across sub-nanometer gaps, where quantum effects become important owing to non-local screening and the spill-out of electrons. However, full quantum simulations are not presently feasible for realistically sized systems. Here we present a novel approach, the quantum-corrected model (QCM), that incorporates quantum-mechanical effects within a classical electrodynamic framework. The QCM approach models the junction between adjacent nanoparticles by means of a local dielectric response that includes electron tunnelling and tunnelling resistivity at the gap and can be integrated within a classical electrodynamical description of large and complex structures. The QCM predicts optical properties in excellent agreement with fully quantum mechanical calculations for small interacting systems, opening a new venue for addressing quantum effects in realistic plasmonic systems. As lengthscales in plasmonic structures enter the sub-nanometre regime, quantum effects become increasingly important. Here, a quantum-corrected model is presented that addresses quantum effects in realistic-sized plasmonic structures, a situation not feasible for full-quantum-mechanical simulations.

G. Mavroeidis, A. Papageorgiou

Zijian Zhou, Lijiao Yang, Jinhao Gao et al.

Magnetic nanoparticles (MNPs) have been extensively explored as magnetic resonance imaging (MRI) contrast agents. With the increasing complexity in the structure of modern MNPs, the classical Solomon–Bloembergen–Morgan and the outer‐sphere quantum mechanical theories established on simplistic models have encountered limitations for defining the emergent phenomena of relaxation enhancement in MRI. Recent progress in probing MRI relaxivity of MNPs based on structural features at the molecular and atomic scales is reviewed, namely, the structure–relaxivity relationships, including size, shape, crystal structure, surface modification, and assembled structure. A special emphasis is placed on bridging the gaps between classical simplistic models and modern MNPs with elegant structural complexity. In the pursuit of novel MRI contrast agents, it is hoped that this review will spur the critical thinking for design and engineering of novel MNPs for MRI applications across a broad spectrum of research fields.

Youngjib Ham, Kevin K. Han, Jacob J. Lin et al.

Over the past few years, the application of camera-equipped Unmanned Aerial Vehicles (UAVs) for visually monitoring construction and operation of buildings, bridges, and other types of civil infrastructure systems has exponentially grown. These platforms can frequently survey construction sites, monitor work-in-progress, create documents for safety, and inspect existing structures, particularly for hard-to-reach areas. The purpose of this paper is to provide a concise review of the most recent methods that streamline collection, analysis, visualization, and communication of the visual data captured from these platforms, with and without using Building Information Models (BIM) as a priori information. Specifically, the most relevant works from Civil Engineering, Computer Vision, and Robotics communities are presented and compared in terms of their potential to lead to automatic construction monitoring and civil infrastructure condition assessment.

Shuoqing Zhao, Ziqi Guo, K. Yan et al.

Abstract With the growing demand for high-energy-density lithium-ion batteries, layered lithium-rich cathode materials with high specific capacity and low cost have been widely regarded as one of the most attractive candidates for next-generation lithium-ion batteries. However, issues such as voltage decay, capacity loss and sluggish reaction kinetics have hindered their further commercialization for decades. Intensive investigations have been devoted to developing high-performance lithium-rich cathode materials, highlighting the importance of improvement strategies as a potential approach. Herein, we summarize various strategies for improving performances of layered lithium-rich cathode materials for next-generation high-energy-density lithium-ion batteries. These include surface engineering, elemental doping, composition optimization, structure engineering and electrolyte additives, with emphasis on the effect and functional mechanism of corresponding techniques. In the subsequent section, we illustrate opportunities and challenges for designing high-performance lithium-rich cathode materials and bridging the gap between the laboratory and practical applications.

V. Gharehbaghi, E. Noroozinejad Farsangi, M. Noori et al.

Huan Yang, Lanqian Gong, Hongming Wang et al.

Nickel–iron composites are efficient in catalyzing oxygen evolution. Here, we develop a microorganism corrosion approach to construct nickel–iron hydroxides. The anaerobic sulfate-reducing bacteria, using sulfate as the electron acceptor, play a significant role in the formation of iron sulfide decorated nickel–iron hydroxides, which exhibit excellent electrocatalytic performance for oxygen evolution. Experimental and theoretical investigations suggest that the synergistic effect between oxyhydroxides and sulfide species accounts for the high activity. This microorganism corrosion strategy not only provides efficient candidate electrocatalysts but also bridges traditional corrosion engineering and emerging electrochemical energy technologies. Developing facile strategies to realize the precise construction of Ni-Fe structures is of significance for water oxidation. Here, the authors demonstrate a universal microorganism-assisted corrosion strategy for preparing highly efficient Ni-Fe composites towards oxygen evolution.

Lemeng Wu, Chengyue Gong, Xingchao Liu et al.

AI-based molecule generation provides a promising approach to a large area of biomedical sciences and engineering, such as antibody design, hydrolase engineering, or vaccine development. Because the molecules are governed by physical laws, a key challenge is to incorporate prior information into the training procedure to generate high-quality and realistic molecules. We propose a simple and novel approach to steer the training of diffusion-based generative models with physical and statistics prior information. This is achieved by constructing physically informed diffusion bridges, stochastic processes that guarantee to yield a given observation at the fixed terminal time. We develop a Lyapunov function based method to construct and determine bridges, and propose a number of proposals of informative prior bridges for both high-quality molecule generation and uniformity-promoted 3D point cloud generation. With comprehensive experiments, we show that our method provides a powerful approach to the 3D generation task, yielding molecule structures with better quality and stability scores and more uniformly distributed point clouds of high qualities.

Matteo Marra, Emma Ghini, Giada Gasparini et al.

Abstract The serviceability of pedestrian bridges may be affected by the discomfort due to vibrations felt by the users crossing the deck. Design guidelines recommend avoiding critical frequency ranges and provide acceptance criteria for maximum accelerations to assess user discomfort for serviceability conditions. The paper presents selected results from an experimental campaign on a two-hinged steel arch pedestrian bridge, analysing its dynamic response to both ambient and human-induced vibrations. Activities such as walking, running, and jumping are investigated. In this field, many research works are available in the scientific literature, but the vibration analysis of a steel arch footbridge with tapered truss cross-section is still missing. The first six vibration modes of the bridge are identified using the Frequency Domain Decomposition technique, while damping ratios are estimated through Enhanced Frequency Domain Decomposition. Walking and running tests reveal a small shift in the bridge's forced response frequencies compared to its free response. Jumping tests are analysed by isolating specific modal responses and estimating modal damping ratios based on free vibration data after the jump. The study also compares the maximum vertical accelerations recorded during these tests with the acceptance limits provided by technical standards. Overall, the paper provides insight into the vibration assessment of a steel arch footbridge with tapered truss cross-section and offers practical indications for field-data interpretation, as well as reference values of natural frequencies, damping ratios and accelerations for this common kind of infrastructures.

Prabal Kandel, Jiadong Wang, Jian Deng

This review synthesizes the state of the art in flapping foil technology and bridges the distinct engineering domains of bio-inspired propulsion and power generation via flow energy harvesting. This review is motivated by the observation that propulsion and power-generation studies are frequently presented separately, even though they share common unsteady vortex dynamics. Accordingly, we adopt a unified unsteady-aerodynamic perspective to relate propulsion and energy-extraction regimes within a common framework and to clarify their operational duality. Within this unified framework, the feathering parameter provides a theoretical delimiter between momentum transfer and kinetic energy extraction. A critical analysis of experimental foundations demonstrates that while passive structural flexibility enhances propulsive thrust via favorable wake interactions, synchronization mismatches between deformation and peak hydrodynamic loading constrain its benefits in power generation. This review extends the analysis to complex and non-homogeneous environments and identifies that density stratification fundamentally alters the hydrodynamic performance. Specifically, resonant interactions with the natural Brunt–Väisälä frequency of the fluid shift the optimal kinematic regimes. The present study also surveys computational methodologies and highlights a paradigm shift from traditional parametric sweeps to high-fidelity three-dimensional (3D) Large-Eddy Simulations (LESs) and Deep Reinforcement Learning (DRL) to resolve finite-span vortex interconnectivities. Finally, this review outlines the critical pathways for future research. To bridge the gap between computational idealization and physical reality, the findings suggest that future systems prioritize tunable stiffness mechanisms, multi-phase environmental modeling, and artificial intelligence (AI)-driven digital twin frameworks for real-time adaptation.

Kai Wang, Gang Liu, Congquan Wang et al.

In order to achieve rapid bridge construction, on-site wet joint joining techniques for prefabricated bridge decks are commonly used. The primary method involves mainly lap welding, but this form poses some drawbacks such as difficult lap jointing of two steel bars and a hefty welding workload. To address these issues, this study conducts model experiments on the unwelded structure of loop joints. We compare and analyze the displacement, crack distribution, crack development process, and strain variability of loop joints across three different overlap lengths, along with one type of straight bar lap-welded wet joints. It is observed that, despite the comparable ultimate tensile capacity of loop joints with the main rib to that of the welded wet joint with the main rib, the failure mode varies, and the crack direction changes with the overlap length. From a structural stress perspective, if the U-bar of the loop joint meets a specific overlap length, the wet joint adequately fulfills stress requirements and can be applied in practical engineering.

YUAN Jianbo, YIN Chan, FENG Xinjun et al.

To improve the comprehensive performance of desulfurized rubber asphalt, the asphalt was modified by using desulfurized crumb rubber and polyphosphoric acid. Based on the response surface method, the preparation parameters of the composite modified asphalt were optimized. In addition, four types of modified asphalt were prepared by using ordinary rubber, desulfurized rubber, composite polyphosphoric acid/ordinary rubber, and composite polyphosphoric acid/desulfurized crumb rubber. Their performance was compared. The results show that compared with ordinary rubber asphalt, the asphalt modified by desulfurized rubber has lower viscosity, significantly lower mixing and compaction temperatures, and more stable compatibility between rubber powder and asphalt in the system, which facilitates the preparation, storage, transportation, and construction process of rubber asphalt. In terms of road performance, the high-temperature deformation resistance of asphalt modified by polyphosphoric acid/desulfurized crumb rubber shows a level similar to that of ordinary rubber asphalt, and its creep ability is more excellent in low-temperature environments. Among the four types of modified asphalt, the asphalt modified by polyphosphoric acid/desulfurized crumb rubber has more obvious performance advantages and is suitable for promotion and application.

WANG Haitao, LU Jianghua, LIU Yang et al.

This study aims to address poor adaptability and timeliness in the design of smooth blasting hole parameters in the past. With the drilling and blasting method-based construction of large cross-section tunnels in Botanggou and Tielugou along the Zunhua‒Qinhuangdao Expressway as the research background and Ⅲ and Ⅳ grade surrounding rocks of porphyritic granite as the research object, statistical regression analysis and theoretical derivation were conducted on the measured data during on-site drilling according to the rock solidity coefficient. Based on this, a simple parameter design method for a smooth blasting layer based on the drilling speed index of an air leg anchor rod drill was proposed, and the relationship between the drilling speed and the parameters of the smooth blasting layer hole was obtained. The research results indicate that there is a good correlation between the drilling speed and parameters such as the spacing between surrounding holes and the thickness of the smooth blasting layer. Based on the engineering conditions of the Botanggou and Tielugou tunnels, a parameter design table was calculated for the drilling speed of the drill rod, the spacing between surrounding holes, and the thickness of the smooth blasting layer. Through on-site practice, this method achieves good smooth blasting results, with a hole trace rate of over 90%. The research findings can provide a theoretical basis and reference for the design of smooth blasting parameters of tunnels in similar geological conditions.

Yan Wang, Yu-Long Zhang, Rui Zhang et al.

Longquan Mountain, located east of the Chinese city of Chengdu, is characterized by a barren red sand soil. For the construction of Longquan Mountain Forest Park, ecological restoration was carried out, which involved mixing pastoral soil and biochar into the milled shale, introducing earthworms, and phytoremediation. This study examined changes in the physicochemical properties and microbial communities of soils through ecological restoration. There was a significant increase in organic matter, total phosphorus, available iron, and total nitrogen, as well as a notable decrease in soil calcium content, resulting in a substantial enhancement of soil quality. Ecological restoration significantly optimized the community structure and diversity of bacteria, but with minor shifts in the composition and structure of fungi. Verrucomicrobia, Chloroflexi, Acidobacteria, and Planctomycetes were enriched in restored soils and functioned in the hydrolysis of polysaccharides and organic acids, as well as in the degradation of plant residues, plant-derived polymers, and bacterial-derived exopolysaccharides. Another dominant bacterium in the restored soil, Gemmatimonadetes, may have contributed to the soil’s adaptation to the seasonally dry environment of the restoration area. In addition, fungi may participate in ecological restoration activities by assisting bacteria, particularly Sordariales, which were once decomposers of decaying matter. Interactions between soil microorganisms, plants and soil nutrients have transformed Longquan Mountain’s ecosystem into a virtuous cycle, with survival rates of vegetation reaching more than 90 percent after two years and significant reductions in harmful substances in the soil. This study provides both a theoretical basis and an engineering demonstration for ecological restoration efforts in degraded or poor soils.

LI Jing, LIU Linlin, ZHU Qiyang et al.

To enhance the performance of recycled high-elastic modified asphalt binder and achieve high-quality and high-content utilization of RAP fine materials in the design of stress absorbing layers, a highly permeable recycled high-elastic modified asphalt (ZGT-R) was prepared by adding SBS modifier, light component oil, and penetrant to replenish the degraded SBS molecules and reduce intermolecular forces. The conventional properties, elastic recovery, degree of fusion between new and aged asphalt, rheological properties, and micro-modification mechanism of ZGT-R and ordinary recycled high-elastic modified asphalt before and after the addition of the rejuvenator were analyzed. The results show that, compared with the two types of ordinary recycled high-elastic modified asphalt, the penetration and ductility of ZGT-R increase by 51.6% and 22.4%, respectively, and the elastic recovery also improves, demonstrating excellent anti-reflection cracking performance and regeneration effect. The higher viscosity ratio also proves that ZGT-R breaks through the limitation of the degree of fusion between new and aged asphalt. In terms of rheological properties, when the aged asphalt content is between 35% and 55%, ZGT-R exhibits lower temperature sensitivity and stress sensitivity and overall shows better anti-deformation ability. Regarding the micro-modification mechanism, the SBS in ZGT-R exhibits a dense spatial cross-linked network structure, proving the full swelling and diffusion of SBS and providing a new idea for the design of high-elastic modified asphalt for recycled stress absorbing layers.

Xiaofeng Cui, Jin Wang, Bing Liu et al.

Development of visible-light photocatalytic materials is an ultimate goal for solar-driven CO2 conversion. Au nanoclusters (NCs) may potentially serve as components for harvesting visible light but can hardly perform solar-driven CO2 reduction due to the lack of catalytic sites. Herein, we report an effective strategy for turning Au nanoclusters catalytically active for visible-light CO2 reduction, in which metal cations (Fe2+, Co2+, Ni2+, and Cu2+) are grafted to the Au NCs using l-cysteine as a bridging ligand. The metal-S bonding bridge facilitates the electron transfer from Au NCs to metal cations so that the grafted metal cations can receive photoinduced electrons and work as catalytic sites for CO2 reduction. The varied d-band centers and binding energies with CO2 for different metal cations allow tuning electron transfer efficiency and CO2 activation energy. Furthermore, the photostability of Au NCs-based catalyst can be significantly enhanced through the encapsulation with metal-organic frameworks. This work opens a new door for the photocatalyst design based on metal clusters and sheds light on the surface engineering of metal clusters toward specific applications.

Zhijia Xue, Wenfeng Zhu, Liangchen Li et al.

During the highway construction in the soft loess region of Northwestern China, there are always tens of thousands of cement mixing piles were used. Which generates a large amount of carbon emissions, thereby affecting the environment. The Simplified Energy and Emissions Assessment Model (SEEAM) is used to quantify carbon emissions considering monitoring data of IoT (Internet-of-Things) system. To reduce the error of the carbon emissions of large samples, Monte Carlo simulation was used to quantify carbon emissions based on the small samples. The results showed that cement had a 47,530.78 t carbon missions contributing the 95.64 % of the total carbon emissions. To concurrently ensure strength and reduce carbon emissions, this study investigates the unconfined compressive strength variations in white mud-cement composite material solidified soft loess. It indicated that 10 % and 20 % white mud provided an alkaline environment and nucleation sites for cement hydration reactions, combining the filling voids. According to the observation results of TG and SEM, the content of 10 % white mud increased the quantity of early hydration product CSH in cement. Which maintained a high level of strength by comparing the cement solidified soft loess. In addition, when the white mud content is 50 %, the white mud-cement composite material reduced 576 % carbon emissions in the cement mixing pile engineering. This study can provide guidance for the selection of engineering construction design schemes, as low-carbon emission schemes are conducive to green and sustainable development of the environment.

C. Ye, Liam J. Butler, Bartek Calka et al.

© International Workshop on Structural Health Monitoring. All rights reserved. Bridges are critical infrastructure systems connecting different regions and providing widespread social and economic benefits. It is therefore essential that they are designed, constructed and maintained properly to adapt to changing conditions of use and climate-driven events. With the rapid development in capability of collecting bridge monitoring data, a data challenge emerges due to insufficient capability in managing, processing and interpreting large monitoring datasets to extract useful information which is of practical value to the industry. One emerging area of research which focuses on addressing this challenge is the creation of 'digital twins' for bridges. A digital twin serves as a virtual representation of the physical infrastructure (i.e. the physical twin), which can be updated in near real time as new data is collected, provide feedback into the physical twin and perform 'what-if scenarios for assessing asset risks and predicting asset performance. This paper presents and broadly discusses two years of exploratory study towards creating a digital twin of bridges for structural health monitoring purposes. In particular, it has involved an interdisciplinary collaboration between civil engineers at the Cambridge Centre for Smart Infrastructure and Construction (CSIC) and statisticians at the Alan Turing Institute (ATI), using two monitored railway bridges in Staffordshire, UK as a case study. Four areas of research were investigated: (i) real-time data management using BIM, (ii) physics-based approaches, (iii) data-driven approaches, and (iv) data-centric engineering approaches (i.e. synthesis of physics-based and data-driven approaches). A framework for creating a digital twin of bridges, particularly for structural health monitoring purposes, is proposed and briefly discussed.

You Dong

Abstract Ultra-high performance concrete (UHPC) as a novel concrete material is associated with very high strength and low permeability to aggressive environment. There have been many studies focusing on the development of UHPC materials. More studies are needed to implement the knowledge obtained from material level into the structural design and construction level. This paper emphasizes on the structural modeling and performance assessment of bridge girders made of UHPC considering the major improvements in terms of structural performance, durability, environmental impacts, and cost-effectiveness in a long-time interval. Additionally, the effect of the concrete strength increase on the life-cycle environmental impact and cost is assessed on a structural scale. An illustrative example is established to demonstrate the use of UHPC within precast-prestressed girder bridge. It is found that the use of UHPC can result in a significant reduction of concrete volume and CO2 emissions compared with conventional bridge with the same span length. Additionally, the life-cycle cost and equivalent annual cost associated with these two bridges are compared. This study aims to aid the development and adaptation of novel materials within civil engineering to make optimal use of the favorable material properties.