Noise barriers play a crucial role in mitigating railway noise, with the aerodynamic pressure exerted by passing trains being a key factor in their structural design, particularly for those installed along high-speed railways. While previous studies have focused on the effects of train speed, geometry, and distance from the track centre, and have developed models incorporating these factors, limited attention has been given to the impact of bilateral layouts and barrier height on this pressure. Quantitative assessments of these two factors remain scarce, and existing pressure calculation models inadequately address their influence. This study addressed these gaps by employing computational fluid dynamics (CFD) simulations, validated by field test data, to qualitatively and quantitatively analyze the effects of barrier layout and height on the aerodynamic pressure acting on vertical noise barriers. The results demonstrate that two distinct transient pressure fluctuations over time are generated by the train’s nose and tail, in agreement with the findings of the field tests. A bilateral layout increases peak pressure by up to 8.5%, particularly as the distance to the train centreline decreases. Moreover, increasing barrier height from 2 to 4 m resulted in a maximum pressure amplification of 13.23%, though the amplification rate diminished with further height increases. To address the limitations of existing pressure calculation models, an exponential model was developed to account for the amplification effect of bilateral layouts, while a logarithmic correction factor was introduced to account for barrier height. These models were integrated into a comprehensive aerodynamic pressure calculation framework, effectively capturing the combined impacts of barrier layout and height. Validated through simulations, the proposed model offers a more accurate and practical approach for predicting train-induced aerodynamic pressure on noise barriers, providing valuable insights to inform their structural design.

The use of digital twin (DT) technology within the engineering and construction (E&C) industry is valuable for practical applications in asset management of structures. Functional DT in E&C, however, are still in initial stages of development. Efforts towards standardization of concepts and procedures are necessary to build on existing knowledge and drive progress further on functional DT. This paper proposes a DT of a snow gallery, part of the Iron Ore railway in northern Sweden. The gallery was instrumented with a structural health monitoring (SHM) system that feeds data in real time to the DT, which also includes a 3D model of the gallery. The proposed methodology can be replicated to different structures and scaled for larger amounts of data. The SHM data and the 3D digital model of the snow gallery are connected in a single, integrated platform that enables improved decision-making for maintenance of the gallery. To promote clarity and progress within the field, the proposed DT’s maturity level is classified in terms of autonomy, intelligence, learning, and fidelity. The snow galleries, the SHM system, and the proposed DT are all presented and discussed, following a brief review on DT, the importance of level classification, and predictive maintenance.

Railway noise barriers are an essential piece of infrastructure for reducing noise propagation. However, these barriers experience aerodynamic loads generated by high-speed trains, leading to dynamic effects that may compromise their fatigue capacity. The most common structural design for railway noise barriers consists of vertical configurations of posts and panels. However, there have been few dynamic analyses of steel post/wood panel noise barriers under train-induced aerodynamic loads. This study used dynamic finite element analysis to assess the dynamic behavior of such noise barriers. Analysis of a 40-m-long noise barrier model and a triangular simplified load model, the latter of which effectively represented the detailed aerodynamic load, were first used to establish the model and input of the moving load during dynamic simulation. Then, the effects of different parameters on the dynamic response of the noise barrier were evaluated, including the damping ratio, the profile of the steel post, the span length of the panel, the barrier height, and the train speed. Gray relational analysis indicated that barrier height exhibited the highest correlations with the dynamic responses, followed by train speed, post profile, span length, and damping ratio. A reduction in the natural frequency and an increase in the train speed result in a higher peak response and more pronounced fluctuations between the nose and tail waves. The dynamic amplification factor (DAF) was found to be related to both the natural frequency and train speed. A model was proposed showing that the DAF significantly increases as the square of the natural frequency decreases and the cube of the train speed rises.

This paper investigates the current landscape of multiscale studies in concrete composites incorporating molecular dynamics (MD) methods. Through a thorough literature analysis, it was determined that finite element, discrete element, homogenization, microphysical characterization, and machine learning methods are better suited for integration with MD in multiscale studies of concrete composites. The paper delves into MD's application characteristics and the selection of force fields in multiscale studies and provides a summary of the combined applications between MD and various methods. Challenges identified include the optimization of MD simulations and the appropriate selection of combined methods. The conclusions underscore the growing recognition of MD's significance, advocating for rational multi-method integration in multiscale approaches to effectively advance research on concrete composites.

Corrosion of steel reinforcement in concrete is a significant cause of structural failure, particularly in environments exposed to chloride ions and mechanical stress. The passivation film on steel reinforcement, composed of hematite or magnetite, plays a crucial role in protecting the steel from further corrosion. However, the intrusion of harmful ions or mechanical stress can compromise the film’s integrity, transforming it into a loose structure and accelerating the corrosion process, leading to structural failure. This study investigates the mechanical behaviors at the interfaces between corrosion products (hematite and magnetite) and C-S-H using reactive molecular dynamics. C-S-H and interfacial models incorporating hematite and magnetite were developed, with stress–strain analysis refined by filtering raw data and using true strain rather than engineering strain to improve the precision of the stress–strain responses. The results indicate that the Magnetite-CSH interface is more prone to loosening under external forces compared to the Hematite-CSH interface, thereby reducing its corrosion resistance. Structural evolution analysis under uniaxial tension highlights the detrimental effects of passivation film degradation on interfacial mechanical properties. This study contributes to improving the precision of stress–strain responses in MD models and facilitates comparison of mechanical properties at the nanoscale with results from other scales. The findings provide valuable guidance for improving the durability and performance of construction materials in corrosive environments, helping to bridge the gap between molecular-level simulations and macroscopic experimental data.

A carefully studied evaluation was necessary to replace an existing pre-stressed concrete box girder bridge that had been in service for over 60 years, in Kalix, Northern Sweden. The bridge was 283.6 m long divided into five spans, and it was constructed using the balanced cantilever method. The decision to replace the old bridge created the need to evaluate a demolition procedure for it, one carefully designed not only to avoid damaging the newly built bridge or creating stability-related issues, but also to prevent any debris from falling into the Kalix River, which is part of a Natura 2000 protected area. This article focuses on the comprehensive methodology, on the demolition design, and on the observations related to residual prestress levels in the bridge, indirectly obtained through a reversed-engineering FEM process and on the limitations of the demolition technology to be used in these specific cases. Several variables were monitored during the deconstruction process, to control the structural stability better during all the phases of the project. The main outcome of the full condition assessment is that it provides the information needed to make informed decisions for interventions on these types of structures.

Molecular dynamics simulations have been increasingly employed to investigate the mechanical properties of cement hydrates at the nanoscale. This technique deepens the understanding of cement-based materials, yet correlating these nanoscale findings with larger scale experiments remains a challenge, particularly due to scaling effects. This study focuses on the scaling impact on calcium silicate hydrate (C-S-H). Two types of C-S-H models were constructed: one with defective silicate chains and the other without. Each model includes three sub-models of varying sizes. Under uniaxial tension along silicon chain direction, the stress and strain responses were recorded. The results show that at the nanoscale, model correction such as silicon chain breakage has a greater impact on the elastic modulus and tensile strength than model size. Additionally, the stress–strain curve obtained during the tension process needs to be corrected before comparison with stress–strain on other scales. The findings provide crucial insights into the mechanical behavior of C-S-H at the nanoscale and offer a theoretical basis for bridging the gap between nanoscale simulations and larger scale experimental results. 

In this study, tension-tension fatigue tests were conducted to investigate the residual stiffness degradation of carbon fiber-reinforced polymer (CFRP) tendons. Different stress levels were used in the tests, and measurements of residual stiffness and the number of loading cycles were taken. Based on experimental data for CFRP tendons, a quantitative residual stiffness model was developed by modifying Yao's model. This model is applicable to various stress levels. To assess its accuracy and applicability, the predicted results of this model were compared with those of cited models from other researchers. The findings revealed a three-stage degradation of residual stiffness in CFRP tendons under different stress levels. Furthermore, it was observed that the proportion of fatigue life accounted for by Stage III decreased with smaller stress ranges, while the proportion accounted for by Stage II increased. The proposed quantitative residual stiffness model was verified using both experimental and cited data. Tension-tension fatigue tests of CFRP tendons were conducted at various stress levels. A quantitative model was proposed based on the residual stiffness of the CFRP tendon. Stress level influence on stiffness degradation of composite material was discussed. Model accuracy was verified against experimental and cited data.

The snow galleries along the Iron Ore railway line in northern Sweden have facedproblems in recent years due to increasingly large snow loads, and several gallerieshave been damaged. These incidents motivated an evaluation of the maximumload supported by the galleries before collapse, which is presented in this study. In2021, a monitoring system was installed in one of the main frames of two snowgalleries built in the 1950s to follow up with temperature and displacements,including a trigger that sends out a warning message when a critical load isreached. A literature review on snow loads was performed, followed bycalculations on snow distribution on the galleries based on the Eurocodes andNational Swedish Standards. Finite element 2D and 3D models were created usingAxisVM to accurately assess the efforts in the structural elements. Analysis anddiscussion are complemented by observations from site visits. It was concludedthat the critical loads supported by the galleries are lower than the requirements oftoday’s standards, but since secondary construction elements were damagedbefore the main frames reached their full capacity, no major collapse has yet takenplace. The cobweb effect (load re-distribution between the neighboring elementsin a 3D structure) influenced the behavior of the galleries in the 3D analysis and thecapacity of the main frames proved to be significantly increased compared to the2D assessment.

The direct socio-economic consequences of the deterioration of aging infrastructure systems have triggered a continuous process of revising and updating current design standards and guidelines for critical network components. Specifically, long-term degradation processes demand the analysis and evaluation of vital structural assets such as prestressed concrete bridges. It is crucial to develop theoretically consistent, user-friendly, and non-destructive methodologies that engineering professionals can employ to prevent and mitigate potential catastrophic outcomes during the service life of these bridges. This study provides a thorough review of the available testing methods employed over the years for prestressed concrete bridges and introduces a comprehensive framework for evaluating existing methods for residual prestress force assessment. Through a multi-criteria selection process, the three most feasible tests were designed and carried out on an existing 66-year-old balanced cantilever box girder bridge exposed to freezing temperatures that affected the instrumentation plan and test execution. Finally, predictive models compliant with standard codes were calibrated based on the experimental results and the life cycle loss of prestress forces was evaluated to assess relevant bounding intervals. Findings reveal limited on-site testing and discrepancies between calculated residual forces and predictions by standard codes. The saw cut method showed a 18% difference from the initial applied prestress according to the prestress protocol, suggesting the use of a cover meter and concrete modulus evaluation for improved accuracy. The strand cutting method resulted in a 14% difference, emphasizing the need for stress redistribution assessment. The second-order deflection method showed a 6% difference, indicating a focus on enhanced boundary conditions and thorough sensitivity analysis for future investigations.