Abstract: Bolt connections are widely used in engineering structures but are prone to loosening during service, which may lead to serious safety issues. Therefore, reliable bolt-loosening detection is of great importance. Traditional detection methods often suffer from drawbacks such as low efficiency, limited accuracy, and the need for contact sensors. To overcome these limitations, this study proposes a novel non-contact approach for bolt preload monitoring based on Digital Image Correlation (DIC). In this method, an industrial camera captures speckle images of the bolt head before and after deformation, enabling measurement of the surface strain. The DIC technique is employed to calculate the strain field on the bolt head surface, which exhibits a linear relationship with the bolt preload. By tracking changes in this strain field, the proposed method allows effective and accurate monitoring of bolt preload. Experimental results demonstrate that the method provides a precise, efficient, and user-friendly solution for bolt preload monitoring, showing great potential for applications in structural health monitoring.

Abstract: This research aims to assess and quantify the significance of incorporating the seismic performance of global and local engineering demand parameters (EDPs) within the probabilistic frameworks, when structural pounding of adjacent buildings occurs. For this purpose, the seismic performance of 6-story and 12-story reinforced concrete (RC) RC frames subjected to floor-floor pounding is assessed. The pounding is caused by an adjacent shorter and stiffer structure with the top contact point at the middle of the tall building’s total height. Displacement-based and ductility-based EDPs are evaluated at different performance levels (PLs) and at different separation distances (dg). The seismic performance of the RC frames without considering pounding is also evaluated. Incremental dynamic analyses (IDAs) are performed, and probabilistic seismic demand models (PSDMs) are developed to establish fragility curves of the examined RC frames. The probability of earthquake-induced pounding between adjacent structures is properly involved with the median value of Sa,T1 that corresponds to an acceptable capacity level (acceptable PL) of an EDP. The results of this study indicate that excluding structural pounding consequences from the probabilistic frameworks related to the seismic risk of colliding buildings leads to unsafe seismic assessment or design provisions.

Abstract: Water supply and drainage networks are essential components of urban infrastructure, directly influencing both residents' quality of life and the efficiency of city operations through their safety and stability. Over time, these networks often develop non-structural turbid water conditions, which present challenges for traditional maintenance methods. Leveraging the advantages of spatial visualization, three-dimensional environmental reconstruction technology has emerged as a promising solution to address these issues, while also advancing the use of intelligent maintenance technologies within water supply and drainage systems. This paper focuses on the causes of non-structural turbid water in these networks, and evaluates the optimization, effectiveness, and limitations of turbid water imaging, image feature recognition, and 3D environmental reconstruction technologies. Additionally, it re-views the current technical challenges and outlines potential future research directions, aiming to support the development and application of 3D reconstruction technologies for pipeline networks under non-structural turbid water conditions.

Abstract: This paper presents a comprehensive linear dynamic analysis of a four-degree-of-freedom (4-DOF) lumped mass shear building model, numerically implemented within the OpenSeesPy framework. The numerical model parameters, including mass distribution, stiffness, and damping characteristics, are derived directly from prior experimental testing of physical frame models. The study evaluates the structural response under a statistically significant suite of 50 earthquake ground motion records, carefully selected and scaled to match the Eurocode 8 target spectrum for Soil C and a peak ground acceleration of 0.1 g, reflecting the specific seismic hazard conditions of Osijek, Croatia. Time-history analyses utilizing the Newmark-Beta integration scheme reveal critical insights into the dynamic behaviour, specifically the influence of base flexibility on fundamental period elongation and the distinct response characteristics across different storeys. Statistical processing of the results, visualized through response spectra fractiles and correlation profiles, demonstrates that while lateral displacements exhibit stable first-mode dominance, floor accelerations display high dispersion and significant higher-mode amplification, known as the whipping effect, particularly at the roof level. The findings underscore the limitations of deterministic analyses and highlight the necessity of probabilistic frameworks for accurately assessing seismic demand in low-to-mid-rise structures.

Abstract: Amid growing environmental concerns, resource depletion, and the pressing challenges of industrial waste management, this study investigates the potential of magnesium slag (MS) as a sustainable alternative binder in the production of one-part geopolymer con-cretes (OPGC). The objective is to reduce reliance on conventional cementitious materials while promoting the valorization of industrial by-products in construction practices. For this purpose, ten different mixtures were designed by replacing ground granulated blast furnace slag (GGBS), the conventional aluminosilicate precursor, with MS, an innovative aluminosilicate precursor, at replacement levels of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% by weight, using a solid activator. The fresh and hardened properties of these mixtures were systematically evaluated through slump, setting time, density, ultrasonic pulse velocity (UPV), and strength tests, while microstructural characterization was also conducted using scanning electron microscopy (SEM) coupled with ener-gy-dispersive X-ray spectroscopy (EDX) to further investigate the geopolymerization process, elemental distribution, and the role of MS in binder formation in OPGC. The results revealed that MS incorporation significantly influenced both workability and mechanical performance, and it was confirmed that MS actively participates in geo-polymerization and can be effectively utilized up to a certain threshold. Replacement levels up to 30% were found to maintain acceptable mechanical performance, providing evidence that MS is a promising precursor for developing sustainable OPGC.

Abstract: Bridge decks are exposed to chloride ingress from de-icing salts, freeze-thaw cycling, and repeated wetting and drying, which gradually degrades the concrete over time. Many existing models treat concrete conditions as static and do not capture time-varying chloride exposure. This study develops deterioration envelopes for concrete bridge decks that predict loss of compressive strength and internal integrity by combining accelerated laboratory testing with in-situ bridge core data extracted from Delaware bridges. The model is supported by three data sources: accelerated laboratory tests, cores from in-service bridges provided by the Delaware Department of Transportation (DelDOT), and climate and asset datasets from the National Oceanic and Atmospheric Administration (NOAA) and the Federal Highway Administration's (FHWA) InfoBridge™ database. Laboratory specimens (n = 300) were reproduced based on Delaware mix designs from the 1970s and 1980s and were tested in accordance with ASTM and ACI protocols. Environmental conditioning applied wet-dry and freeze-thaw cycles at chloride contents of 0, 3, and 15 percent to replicate field exposure within a shortened test period. Measured properties included compressive strength, modulus of elasticity, resonance frequency, and chloride penetration. Results show a gradual, near-linear reduction in compressive strength and resonance frequency with increasing chloride content over 160 cycles, which corresponds to about 2 to 5 years of service exposure. Resonance frequency was the most sensitive indicator of internal damage across the tested chloride contents. By combining test results, core data, and bridge inspection history into a single durability index, the deterioration envelopes forecast long-term degradation under different chloride exposures, providing a basis for prediction that extends beyond visual inspection.

Abstract: The challenge of insufficient monitoring accuracy in vision-based multi-point dis-placement measurement of bridges using Unmanned Aerial Vehicles (UAVs) stems from camera motion interference and the limitations in camera performance. Existing methods for UAV motion correction often fall short of achieving the high precision necessary for effective bridge monitoring, and there is a deficiency of high-performance cameras that can function as adaptive sensors. To address these challenges, this paper proposes a UAV vision-based method for multi-point displacement measurement of bridges and introduces a monitoring system that includes a UAV-mounted camera, a computing terminal, and targets. The proposed technique was applied to monitor the dynamic displacements of the Lunzhou Highway Bridge in Qingyuan City, Guangdong Province, China. The research reveals the deformation behavior of the bridge under vehicle traffic loads. Field test results show that the system can accurately measure vertical multi-point displacements across the entire span of the bridge, with monitoring results closely matching those obtained from a Scheimpflug camera. With a root mean square error (RMSE) of less than 0.3 mm, the proposed method provides essential data necessary for bridge displacement monitoring and safety assessments.

Abstract: This study investigates the differences in flexural behavior of ultra-high-performance concrete (UHPC) arising from variations in test methods and key experimental parameters. Flexural tensile tests were conducted on 51 specimens representing 17 combinations of test variables, including steel fiber length (13 mm and 19.5 mm), specimen cross-sectional dimensions (75×75 mm, 100×100 mm, and 150×150 mm), presence or absence of a notch, and loading configuration (three-point and four-point loading). The tests were performed in accordance with ASTM C1609 and EN 14651, and both deflection and crack mouth opening displacement (CMOD) were normalized by the span length to compare the influence of each parameter. The notched specimens demonstrated significantly improved reliability, exhibiting up to an 8.4-fold reduction in standard deviation due to the consistent initiation of cracking. Regarding size effects, the 75×75 mm specimens showed an overestimation of flexural performance due to the wall effect of fiber distribution, whereas the 100×100 mm and 150×150 mm specimens exhibited similar flexural responses. The comparison of loading configurations revealed that three-point loading produced up to 11.7% higher flexural tensile strength than four-point loading, attributable to concentrated moment–shear interaction and the combined effects of fiber bridging and shear resistance mechanisms. In addition, specimens with longer steel fibers (19.5 mm) exhibited 5.2–9.7% higher flexural performance than those with shorter fibers (13 mm), which is attributed to enhanced interfacial bonding and improved crack dispersion capacity.

Abstract: The rapid mobilization of sediment stored behind dams, in amounts that are large relative to mean annual sediment loads can jump start river restoration but can also adversely impact habitat, infrastructure, land, and water use upstream of, within, and downstream of the former impoundment. A wide range of geomorphic and engineering assessment tools were applied to help manage sediment-related risks associated with the removal of two dams from the Elwha River in Washington State and the release of roughly 21 million m3 of sediment. Each of these tools had their strengths and weaknesses, which are explored here. The processes of sediment erosion, transport and deposition were complex. No one model was able to fully simulate all these with the accuracy necessary for predicting the magnitude and timing of coarse and fine sediment release from the reservoir. Collectively, however, the model outputs provided enough information to guide the adaptive sediment management process during dam removal. When the complexity of the morphodynamic responses to dam removal and the associated risks exceeded the capacity of any one tool to adequately assess, synoptic forecasting proved useful. The lessons learned on the Elwha have provided insights into how to use a variety of modeling techniques to address sediment management issues such as dam removal scale, complexity and risk increase.

Abstract: The article deals with the issue of designing reverse curves in a railway track, i.e. a geometric system consisting of two circular arcs (usually with different radii), directed in opposite directions and directly connected to each other. It is also about being able to recreate (i.e. model) the existing geometric system with reverse arcs, so that it is then possible to correct the horizontal ordinates in the area where the circular arcs connect. An analytical method of designing track geometric systems was used, in which individual elements of these systems are described using mathematical equations. The design itself is carried out in the appropriate local Cartesian coordinate system, which is based on symmetrically arranged adjacent main directions of the route. The origin of this system is located at the point of intersection of adjacent main directions, whose coordinates in the global system are known. In the case of reverse curves, a third main direction appears, which significantly complicates the design procedure. The initial values ​​of the radii of the reverse arcs must correspond to the existing system of main directions. The introduction of transition curves causes these radii to decrease; their values ​​are determined iteratively. A set of formulas for creating a geometric system of reverse curves is presented. These formulas were used in the calculation example. A graph of the horizontal curvature of the track axis and a method for determining the possible train speed without the use of cant on an arc and with the use of cant are shown. The presented procedure is universal and can be applied to other geometric situations involving the design of reverse curves.

Abstract: This study investigates the behaviour of Compressed Earth Cylinders (CECs) and Compressed Earth Blocks (CEBs) during direct compression tests and examines the influence of aspect ratio and the effects of platen restraint. The experimental investigation utilises two soil types and examines the impact of jute fibre reinforcement on the failure mechanism of CECs with aspect ratios ranging from 0.50 to 2.00. Through experimental analysis and numerical modelling, the effects of platen restraint are examined, and a novel hypothesis of intersecting cones is presented. The results show that specimens with a lower aspect ratio exhibited higher compressive strength due to confinement caused by platen restraint. Moreover, this research has derived new aspect ratio correction factors which enable conversion from Apparent Compressive Strength (ACS) to Unconfined Compressive Strength (UCS) of unstabilised and fibre-reinforced CECs. A theoretical relationship between CECs and CEBs was also determined, with an accuracy of 2.7 %. The outcome of this research recommends a standard approach to the application of aspect ratio correction factors when interpreting and reporting the compressive strength of CECs and CEBs.

Abstract: With respect to safety-critical infrastructure such as nuclear power plants, offshore wind turbine platforms, and cross-sea bridges, the coupled effects of carbonation, corrosion, and fatigue may lead to catastrophic failures. In this study, an experiment involving 14 reinforced concrete beams was conducted to investigate the indirect coupling effect of fatigue damage and a carbonation environment. On the basis of the results of the fatigue damage tests, porosity was selected as the damage variable. Finally, based on the electrochemical principles of reinforcement corrosion and considering the impact of fatigue damage on oxygen diffusion, a corrosion-based electrochemical model for reinforced concrete under the coupled effects of fatigue damage and carbonation was established, along with a numerical simulation. The key factors influencing the reinforcement corrosion behavior were also analyzed. (1) The oxygen concentration distribution at any position on the steel reinforcement surface within the concrete increased with increasing damage, whereas the lowest oxygen concentration occurred at the interface between the anode and cathode. The corrosion current density on the steel reinforcement surface reached its maximum value at the anode–cathode interface, and the average corrosion rate increased with increasing damage. The corrosion rate of steel reinforcement in concrete with 82.5% damage was up to 18% higher than that observed in undamaged concrete. (2) When the saturation rate s < 0.7, the corrosion of the reinforcing steel in concrete was mainly controlled by its resistivity, and the corrosion current density increased with increasing saturation; when the saturation rate S > 0.7, the corrosion process was controlled by cathodic oxygen diffusion, and the corrosion current density decreased with increasing saturation. (3) Compared with the effect of temperature, the influence of fatigue damage on the corrosion potential was weaker. The average corrosion current density increased with both temperature and fatigue damage. For concrete with 82.5% damage, the average corrosion current density was 0.00265 A/m² at a certain temperature and increased to 0.00315 A/m² at a higher temperature, representing an increase of approximately 20%. (4) When the concrete was undamaged, the average corrosion current density of the reinforcing steel anode continuously decreased as the thickness of the concrete cover increased. However, after the damage level increased, the average corrosion current density of the anode initially increased but then decreased with increasing cover thickness. The results of this study provide a theoretical basis and a reference for the safe operation and maintenance of major engineering projects.

Abstract: Wind design aims to ensure the stability, safety, and durability of a structure exposed to wind forces. Therefore, a comparative study using Computational Fluid Dynamics (CFD) was conducted to evaluate the effects of surrounding structures in wind building design. Two scenarios were analyzed: the first, in which the building was exposed to an open field, and the second, in which the building was surrounded by other buildings of equal or lower height. A CFD model, previously calibrated with experimental data, was used to simulate wind behavior. The results obtained showed significant differences between the two scenarios, confirming that nearby structures have a considerable impact on the distribution of wind pressures on the building. Therefore, the importance of considering surrounding buildings is highlighted. It is suggested that CFD can be a useful complementary tool for obtaining pressure coefficients and for the detailed analysis of wind behavior, which could improve the design and safety of buildings under wind loads.

Abstract: Asymmetric V-shaped tunnels are commonly found in newly built urban underground road tunnels. During a fire, the smoke flow in such kind of tunnels is complex, and effective smoke control under longitudinal ventilation is challenging. The critical ventilation speed under different slope combinations and fire heat release rate (HRR) in asymmetric V-shaped tunnel with the fire source located at the slope change point were studied by experiments through a 1:20 scaled model tunnel. The research results indicate that the critical ventilation speed increases with the increase of the fire HRR. Under the same fire heat release rate, when longitudinal ventilation is implemented on the side with small slope, the critical ventilation speed decreases as the slope difference between the two sides of the slope change point increases. Conversely, when longitudinal ventilation is implemented from the large slope side, the critical ventilation speed increases with the slope difference increasing. For practical engineering applications, based on the critical ventilation speed of the single-slope tunnel, combining with the experimental results, slope corrections were applied to the critical ventilation velocity of V-shaped tunnels. Calculation models for the critical ventilation velocity under longitudinal ventilation from the large or small slope sides were obtained respectively. The research findings can provide technical support for the design and operation of smoke control systems in V-shaped tunnels during fire incidents.

Abstract:

A comprehensive diagnosis of the railway line aims to control its actual structure and geometric arrangement. Such railway inspections can help detect potential track deformation caused by operational loads and climatic effects. Geodetic monitoring appears to be a beneficial component of such diagnostics, particularly when modern terrestrial or aerial laser-scanning techniques are employed. The reliable determination of track deformation using geodetic contactless methods relies on precise measurements, high-quality instruments, and point cloud processing, which is based on specific numerical procedures that help reveal possible track displacements or deformations. At the same time, the used geodetic methods should reflect the required minimal resolution depending on the size and type of the measured track geometric parameter. The paper presents a brief description of a comprehensive diagnostic conducted on the Tatra Electric Railway, a single-track, narrow-gauge line in the mountain tourist resort of northern Slovakia, with a closer focus on point cloud processing acquired using geodetic methods.

Abstract: Cost estimation is a core function of construction planning, yet it remains one of the most time-consuming and fragmented tasks in the industry. Even with better tools and more data, estimators deal with recurring challenges like inconsistent quantity formats, scattered historical data, and manual subcontractor reviews. These challenges slow down the process and increase the risk of errors, especially early in a project when decisions matter most. This study maps how estimation is actually done in practice, pinpoints where the main burdens occur, and proposes a generative AI-based framework to help streamline and support the process. Using a qualitative approach, ten semi-structured interviews were conducted with industry experts, including estimators, BIM/VDC managers, data analysts, and project managers. Thematic analysis of these interviews led to the identification of key burden areas, which were grouped into three categories: conceptual estimation, subcontractor evaluation, and change management. The results show that current workflows are heavily dependent on manual data handling, subjective judgment, and disconnected tools. In response, the study proposes a targeted LLMs-enabled framework designed to assist with quantity standardization, historical cost referencing, subcontractor bid evaluation, and version control.

Abstract: The ongoing concern about sustainable infrastructure has driven the development of cement-based adhesives (CBAs) for fibre-reinforced polymer (FRP) retrofitting of con-crete structures. Nevertheless, traditional CBAs usually have low bond strength, low crack resistance, and low long-term durability that undermine the performance of FRP-concrete systems. To overcome these shortcomings, this review focuses on the po-tential of nanomaterial-modified CBAs to improve interfacial bonding and mechanical integrity. A systematic literature review assessment was used to analyze recent experimental studies on CBAs with nanosilica, carbon nanotubes, graphene oxide, and other nanomaterials. Their functions in enhancing adhesion, load transfer efficiency, environmental stressor resistance, and the overall structural performance have been emphasized in the review. It also contrasts the performance of neat and nano-modified CBAs in the FRP-based retrofitting systems, highlighting their ad-vantages and shortcomings. Particular emphasis is put on new high-strength self-compacting cementitious adhesives (IHSSC-CAs), which have a high level of me-chanical performance and environmental friendliness in relation to traditional bonding systems. The paper concludes with the identification of research gaps, a discussion of the practical implementation issues, and an explanation of the future perspectives of the next-generation sustainable and resilient concrete retrofitting technologies development.

Abstract: This paper presents a study focused on ensuring acoustic comfort in rooms intended for educational purposes. In educational environments, students can concentrate more effectively when sound disturbances that may distract from the learning process are minimized. Enhancing the acoustic conditions leads to improved performance and allows students to complete their activities in a calmer environment. The importance of determining the reverberation time is emphasized, as it is a key criterion in assessing the acoustic quality of enclosed spaces. The measured values were adjusted according to the standards STAS 9783/0-84 and Normative C125-2013. Three commercially available solutions were proposed to optimize the acoustic comfort of the studied room, and the most suitable solution was selected. The chosen option complies with the requirements of STAS 9783/0-84 and Normative C125-2013, thus ensuring a high level of acoustic comfort. From an interior design perspective, this solution also harmonizes best with the existing environment, particularly with the color tones of the existing HPL panels.

Abstract: Hydraulic structures, particularly water intake systems, are often affected by unwanted bedload depositions, which can significantly reduce their operational efficiency and lifespan. This numerical study presents the potential of using oblique vertical underflow baffles in redistributing the bedload and mitigating bedload accumulations at desired locations. In this study, a straight rectangular channel containing an underflow baffle submerged up to 20% of the water depth was analyzed in a three-dimensional computational fluid dynamics model while varying the discharge, baffle alignment, and channel width coverage. The specific flow conditions induced by the oblique underflow baffles generates a vortex on one side of the channel following the trailing edge of the baffle, where a bedload free zone is created, unlike the case with an orthogonal baffle. This phenomenon offers a potential strategy for managing bedload movement in channels and sluices, providing a means to prevent undesirable bedload depositions and to help operating hydraulic structures efficiently. Furthermore, increasing discharge expands the bedload free zone, and the oblique baffle remains significantly effective even for channel width coverage of just 25%, which indicates the potential of cost-effective designs with limited structural supports. Moreover, this study demonstrates that oblique underflow baffles can effectively guide bedload transport within the channel cross-section, presenting a practical and efficient approach for bedload management and safeguarding intake and similar hydraulic structures.

Abstract:

The paper investigates the impact of processing and mix design factors that determine the effectiveness of adding crushed and sieved concrete rubble (hereafter – recycled concrete fines, RCF) into cement-based concrete. The set of factors includes the dosage and specific surface area of RCF, cement content, superplasticizer dosage, temperature of thermal treatment of RCF, and dosage of accelerating admixture. The compressive strength of the concrete from which the rubble was obtained was preliminarily established based on its correlation with mass loss during crushing. XRD, SEM, and EDS tests were used to determine the chemical and mineralogical composition of RCF and the morphology of the particles. There were specific surface areas of RCF, pozzolanic activity, and correlations with fineness and thermal treatment temperature. Using the experimental design, experiments were carried out by varying six factors: RCF specific surface area, RCF content, thermal treatment temperature of RCF, cement content, superplasticizer dosage, and hardening accelerator (Na₂SiF₆) content in concrete containing RCF. Statistical processing of the experimental data provided adequate polynomial regression models for the water demand of the fresh concrete and the compressive strength of hardened concrete at 7 and 28 days. Analysis of the models made it possible to quantitatively assess the influence of the studied factors on the output parameters and rank them by their degree of influence. The greatest increase in water demand was attributed to cement content, especially above 400 kg/m³, and to RCF content. It was established that the addition of a superplasticizer allows for compensating additional water demand and the reduction of compressive strength caused by increased RCF dosage. The influence of different RCF activation methods on compressive strength was ambiguous. Increasing the specific surface area up to a specific surface area of 250 m²/kg of RCF improved strength, but further grinding caused strength reduction due to increased water demand. The positive effect of the superplasticizer on RCF-modified concrete strength was enhanced by the introduction of a chemical activator (hardening accelerator) and thermal treatment of RCF. The obtained models of water demand and compressive strength of concrete with RCF can, under certain conditions, be applied for the optimisation of mix design. The paper proposes a method of mix design and provides an example of calculation.