Periodica Polytechnica Civil Engineering
International scientific journal. It accepts research and application oriented papers in all aspects of civil engineering.
Budapest University of Technology and Economics
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Strength Properties and Evaluation Method of Composite Modified Carbonaceous Mudstone Soil-rock Mixtures
The application of carbonaceous mudstone soil-stone mixtures (CM-SRM) in embankment engineering is limited due to its poor mechanical properties. This study aims to enhance the strength properties of CM-SRM by modifying it with guar gum, fly ash and red clay. Unconfined compressive strength (UCS) tests and triaxial compression tests were carried out using orthogonal design methods to systematically analyze the mechanical properties and modification mechanisms of modified CM-SRM. The results indicated that the modified CM-SRM exhibited failure modes such as single-shear, single-shear-bulging, double-shear, and double-shear-bulging, with fly ash and guar gum dosages significantly affecting both failure modes. Unconfined compressive strength and cohesion increased post-modification, with minor changes in friction angle. Orthogonal analysis reveals that guar gum dosage significantly effects on UCS and shear strength indexes, whereas the effect of fly ash is comparatively weaker. Based on the test results, a shear strength evaluation method based on linear and nonlinear models is proposed. The study shows that the composite modification mechanisms of red clay, fly ash, and guar gum on CM-SRM mainly includes bonding and filling effects, cation exchange, and gel aggregation. The suggested dosage combination is 10% red clay, 5% fly ash, and 4% guar gum.
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Automated Graph Theoretic Force Method and its Application in Optimal Design of Frame Structures
In this study, the graph-theoretic force method is applied to the optimal design of frame structures and systematically compared with the conventional displacement method. The optimization is performed using the Water Strider Algorithm (WSA), a recently developed bio-inspired metaheuristic, whose population-based search strategy is integrated with both analysis approaches. To ensure reproducibility, all key WSA parameters are reported, and large-scale highly indeterminate frame examples (up to 292 members) are tested, extending beyond previous benchmark studies. In addition, a counterexample with DKI < DSI is included, demonstrating that the relative efficiency of the two methods is problem-dependent rather than universal. The results show that for large-scale highly indeterminate frames, the graph-theoretic force method combined with WSA significantly reduces computational time while maintaining accuracy comparable to the displacement method. These findings highlight both the scalability and the limitations of the graph-theoretic force method, offering a balanced perspective for its practical application in structural optimization.
Investigation of Wind Loading on a Multi-span Anticlastic Tensile Membrane Surface: A CFD Approach
The determination of the wind loads of tensile membrane structures is of crucial importance during their design, since the extremely light weight of the structures can easily lead to severe wind effects on the doubly curved surfaces. According to the current state of the art, almost exclusively wind tunnel test is applied, which is the most reliable method today. On the other hand, the time and cost-consumption of the physical measurements, as well as the questions around the Reynolds number dependency of the wind loads, are serious bottlenecks of such an experimental method. Computational Fluid Dynamics offers an excellent and flexible tool to overcome such problems, but the currently available computational powers prevent the application of robust and high-fidelity scale-resolving methods. The paper deals with the Computational Wind Engineering-based determination of the mean wind loads on a doubly curved tensile membrane structure, applying the Reynolds-averaged Navier-Stokes framework. The conventional k-ω Shear Stress Transport and the recently developed generalized k-ω turbulence models are applied in the simulations. The latter model provides a set of tunable model parameters, where the modification of the coefficients is much clearer and straightforward compared to other turbulence closure models. By tuning the relevant parameter during the simulations, the second model provided significantly better results. The numerical results are validated against experimental data from previous wind tunnel measurements. The internal forces of the membrane in the principal directions of the orthotropic membrane material are computed, and the maximal values of the experimental and numerical-based distributions are compared.
Numerical Investigation of Wave Induced Scour Depth Around Slender and Grouped Monopile
Wave-induced scour around monopile foundations poses a critical challenge for offshore wind turbine design, affecting stability, serviceability, and maintenance costs. Despite extensive experimental studies, high-fidelity numerical tools are still needed to capture complex interactions between wave kinematics, sediment transport, and pile geometry. This study presents a numerical investigation of scour depth around slender monopiles under regular wave conditions. A validated three-dimensional CFD model (FLOW-3D) employing the Volume of Fluid method and RNG k–ε turbulence closure was used to simulate wave–structure–seabed interaction. Sediment transport was modeled using the Meyer–Peter and Müller bedload formulation and an advection–diffusion equation for suspended load. The influence of the Keulegan–Carpenter (KC) number was examined for KC = 8.8–24, covering inertia- and drag-dominated regimes. Results showed that higher KC values intensified vortex-induced sediment transport and scour, while lower KC values led to gradual development. A marked increase occurred beyond KC ≈ 14, indicating a regime shift in flow–sediment interaction. Grouped-cylinder cases at G/D = 1 and 2 showed that narrow spacing produced mutual sheltering and reduced scour, whereas wider spacing caused deeper localized erosion. Single monopile predictions matched experimental data and empirical formulas, demonstrating the model's predictive capability. These findings emphasize the strong KC dependence of scour and suggest that spacing ratios above G/D = 1.5 may help mitigate adverse group effects in array layouts under oscillatory wave forcing.
Metaheuristic-optimized Machine Learning for Mechanical Property Prediction in Eco-friendly Rubberized Concrete
The disposal of discarded tires presents a global environmental challenge, but recycling them into rubber particles for concrete offers a sustainable solution, reducing waste while creating eco-friendly construction materials. However, experimental studies in this field are resource-intensive, requiring significant time and financial investment. This research develops 99 machine learning (ML) models, optimized using three improved metaheuristic algorithms, to predict the mechanical properties of rubberized concrete. The eight ML models include Adaptive Boosting, Artificial Neural Networks, Decision Tree, Gradient Boosting, K-Nearest Neighbors, Random Forest, Support Vector Machines, and Extreme Gradient Boosting, refined through the Improved Hybrid Growth Optimizer, Improved Ray Optimization, and Improved Sand Cat Swarm Optimization algorithms. A dataset of 315 experimental cases, incorporating six input variables, rubber size, rubber weight, cement content, water content, coarse aggregate, and fine aggregate, was analyzed. In addressing missing data for certain mechanical properties, a two-level sequential artificial neural network was employed. The study revealed that the XGBoost-IRO hybrid model excelled in predicting compressive and tensile strength, while the AdaBoost-ISCSO ensemble was best for flexural strength, and the XGBoost-IHGO model performed optimally for modulus of elasticity. Partial Dependence Plots and SHAP analysis highlighted the complex relationships between input variables and mechanical properties, confirming the significance of all input features. Validation through Taylor diagrams and error distribution further confirmed the reliability of the models in predicting all mechanical properties.
Investigation of the Mechanical Properties of Self-compacting Concretes Containing Mineral Additives Produced by Substituting Fine Recycled Aggregate in Different Rates
In the study, the effect of fine recycled concrete aggregate (FRCA) replaced by natural fine aggregate on some mechanical properties of self-compacting concrete (SCC) containing different types and amounts of mineral additives was evaluated. In the concretes produced for this purpose, natural fine aggregate was replaced with FRCA at the ratios of 35%, 70% and 100% by weight. For comparison, concretes without FRCA were also produced. Three different mineral additives, namely fly ash (FA), metakaolin (MK) and silica fume (SF), were used in different ratios. In order to determine the fresh state properties of concretes, unit weight, slump-flow, T500 time, J-ring and sieve segregation tests were carried out, while compressive strength, splitting tensile strength, flexural strength, Böhme abrasion and dynamic elasticity modulus determination tests were carried out on hardened concretes. Based on the findings obtained, there is no significant adverse effect on the mechanical properties of concrete with 35% FRCA replacement. However, when FRCA is used at higher ratios, the negative effect on mechanical properties becomes evident. In particular, Böhme abrasion is quite high at high FRCA replacement ratios. Provided that the conditions in which the research was carried out are valid, the negative effects of FRCA substitution on the mechanical properties of concrete can be eliminated by changing the type and combination ratios of mineral additives used.
The Effect of Different Block Shapes on the Downstream Local Scour in Piano Key Weir
Piano key weirs (PKWs) have a higher discharge capacity than their traditional form, the labyrinth weirs. Due to the high efficiency of PKW, the investigation of their downstream scour is important and requires mitigation strategies. For the first time, this study investigated scour reduction using different block shapes in the outlet keys of a C type trapezoid PKW. The shapes of the blocks are rectangular cubes, trapezoidal cubes (prisms), and cylinders. The range of the densimetric Froude number was between 1.038 and 2.903, while the range of the ratio of the total flow head upstream of the weir to its downstream was between 0.252 and 0.461. The findings revealed that scouring was reduced by 12.7 and 27.3% with an increase of 200 and 300% in the tailwater depth and by 14.5 and 29.3% with a 12.5 and 25% decline in the flow rate. Blocks in the outlet keys significantly reduced the maximum scour depth, with rectangular blocks being the most effective (55.7% reduction), followed by trapezoidal (32.2%) and circular (11.3%). Blocks also elongated the scour hole and shifted the maximum scour depth away from the weir toe. The scour index was lower in weirs with blocks, indicating reduced overturning risk.
Probabilistic Stability Analysis of an Open-pit Dolomite Quarry in Hungary
Due to inherent geological uncertainties, slope stability is a critical factor in open-pit mining operations. These uncertainties affect stability assessments, including spatial variability, weathering, and human factors. The quarry in Vilonya, Hungary, excavates dolomite rock, characterized by fragmentation and variable joint conditions. Post-mining, stability is assessed to determine whether slopes can maintain steeper angles than the standard 45°. This study evaluates the stability of slopes in the Vilonya dolomite quarry using probabilistic methods to account for geotechnical variability and to assess the feasibility of steeper slope angles. A combination of field measurements, laboratory tests, and computational analyses were employed. Joint orientations and roughness were determined through photogrammetry and Barton comb measurements. Statistical analysis of rock parameters were done by software like Analytic Solver. Stability was analyzed using Rocscience software (Dips, RocPlane, SWedge, Slide2) for various failure mechanisms, including planar and wedge sliding, as well as global stability. Kinematic analyses identified critical joint sets that may contribute to slope failure. Probabilistic assessments showed that some joint intersections present failure probabilities as high as 67.42% for wedge failure, while planar sliding risks were negligible. Global stability analysis indicated no critical failures, with safety factors consistently above 1.35 across all slopes. Probabilistic methods reveal significant insights into slope stability that deterministic approaches may overlook. The study confirms the feasibility of maintaining steeper slope angles under controlled risk, optimizing extraction while ensuring stability. Incorporating probabilistic analysis is recommended for reliable slope design in similar geological settings.
Comparative Assessment of Pore Structure and Water Retention in Concrete Using MIP, CT, SEM, and Dewpoint Techniques
Understanding water retention and pore structure in concrete is essential for modeling unsaturated flow and assessing long-term durability, particularly in containment and deep foundation structures. This study investigates two concrete mixtures with different water-to-cement (w/c) ratios (0.40 and 0.50) using a multi-method approach. Water retention curves (WRCs) were measured with a chilled-mirror dewpoint potentiometer and fitted using the Fredlund–Xing model. Pore structures were analyzed via mercury intrusion porosimetry (MIP), X-ray computed tomography (CT), and scanning electron microscopy (SEM). Results show that the mixture with the lower w/c ratio exhibits a higher proportion of fine pores, while the higher w/c ratio leads to a broader pore size distribution and a flatter WRC. MIP-based WRC estimations provided a rough approximation but consistently underestimated measured retention values. CT and SEM revealed distinct pore size domains, with pore size distributions fitting better to a lognormal model than to a Weibull distribution. Although each technique offers only partial insight, their combined application allows for a more comprehensive understanding of concrete's pore network and its effect on hydraulic behavior. The findings highlight both the potential and the limitations of using indirect pore structure data to estimate water retention characteristics in cementitious materials.
Sustainable Use of Construction Waste: Fire Resistance and Strength Characteristics of Recycled Aggregate Concrete for Sustainable Concrete
The pursuance of sustainability in construction has propelled the adoption of innovative materials, with recycled aggregate concrete (RAC) emerging as a pivotal solution to address the environmental challenges posed by traditional concrete. Sustainability in construction has become a global priority, driven by the need to reduce environmental impacts and conserve natural resources. The increasing use of green building certifications like LEED and BREEAM highlights the push towards innovative materials, including RAC. With construction and demolition (C&D) waste accounts for 31% of Europe's total annual waste and global consumption of natural aggregates (NAs) projected to double in the coming decades, recycling concrete waste into recycled concrete aggregates (RCA) has emerged as a sustainable alternative. Studies show that RCA use can reduce greenhouse gas emissions by 65% and non-renewable energy consumption by 58%. Despite advancements in RAC research, challenges remain, particularly regarding its performance under extreme conditions like fire. This study investigates the mechanical and durability properties and potential of using recycled aggregate(RA) in conventional concrete as a replacement in varying percentages of recycled fine and coarse aggregates (0%, 25%, 50%, 75%, and 100%) after exposure to different elevated treatment temperatures (20, 100, 200, 300, 400, 500, 600, and 800 °C). The findings aim to address gaps in understanding the thermal behavior of RAC and promote its adoption as an environmentally friendly construction material.
Reliability Analysis of Stone Columns Improved Ground for Mitigation of Liquefaction
Stone columns are widely used to improve ground performance and mitigate liquefaction in weak or loose soils. However, conventional deterministic design methods fail to account for the uncertainties in soil and column properties, which can significantly affect performance under seismic loading. To address this gap, this study presents a reliability-based framework for assessing the effectiveness of stone columns in reducing liquefaction potential. The analysis considers key random variables – seismic acceleration (amax), saturated unit weight (γsat), stone friction angle (φ′c ), shear wave velocity (Vs), and column diameter (Dc) – under normal and lognormal distributions. Probabilistic methods, including First Order Second Moment (FOSM), Point Estimation Method (PEM), and Monte Carlo Simulation (MCS), were applied to evaluate the reliability index (β). Results show that increasing parameter uncertainty leads to a significant reduction in β, even when the deterministic safety factor exceeds unity (≈1.50). Sensitivity analysis reveals that Vs and γsat have the greatest influence on reliability, while Dc and amax exhibit minimal impact. These findings underscore the necessity of incorporating probabilistic approaches in design and provide insights for simplifying reliability assessment by reducing the number of random variables without compromising accuracy.
Closed-form Solutions for Lateral Displacement of Single-bay Coupled Shear Walls Using a Subsystem-based Three-field CTB Beam
Local shear deformation and axial extensibility of walls have recently been recognized as critical, yet previously overlooked, sources of error in predicting the lateral displacement of coupled shear walls. Existing analytical models often face limited practical application due to solution complexity and insufficient physical clarity. Using a generalized continuous model, this paper proposes a simple, exact, closed-form analytical formulation based on an independent subsystem approach, enabling fast and accurate estimation of lateral displacements. The generalized continuous model couples, in parallel, an extensible Timoshenko beam and a shear beam, thereby capturing both shear deformation and axial extensibility. The total lateral displacement is expressed as a linear combination of three independent subsystems: bending, shear, and bending–shear coupling. Closed-form solutions are derived for each subsystem under uniform, triangular, and top-concentrated loading. The displacement components—bending, shear, and interaction—are physically interpreted, with the interaction term arising exclusively from the coupling subsystem. Numerical examples illustrate the physical meaning of each component, while a parametric analysis establishes applicability limits, showing a maximum safe-side error of +7.30%, compared to the −56.04% unsafe-side error of the classical solution. The proposed formulation ensures structural safety, maintains analytical simplicity, and is well-suited for practical engineering design.
Producing Concrete Incorporating Hybrid Cementitious Materials and Recycled Concrete Aggregate with Novel Thermal Treatment Methods
Recycled concrete aggregate (RCA), characterized by high porosity and adhered mortar, often impairs the mechanical strength and durability of concrete. This research develops a new integrated treatment method, which combines thermal-mechanical conditioning of RCA with hybrid supplementary cementitious materials (SCMs), including metakaolin (MK) and ground granulated blast-furnace slag (GGBS). Three thermal treatment protocols were applied to enhance RCA quality, and concrete mixes with 50% and 100% RCA replacement were prepared. The study investigated the impact of adding MK up to 30% and GGBS up to 20% on the compressive strength, splitting tensile strength, workability, and water absorption of concrete. Although isolated effects require further investigation, the research found that the integrated use of TT3-treated RCA, where TT3 refers to the stepped thermal treatment protocol and SCMs, showed promising performance under the experimental conditions, producing a 90-day compressive strength greater than that of the control mix and reducing water absorption by more than 30%. The combined application of thermal-mechanical treatment (TT3) on RCA and the use of hybrid supplementary cementitious materials (SCMs), such as metakaolin (MK) and ground granulated blast-furnace slag (GGBS), significantly improved the concrete properties. The integrated use of TT3-treated RCA and SCMs resulted in a 90-day compressive strength that was 5.5% higher than that of the control mix, indicating significant long-term performance improvements.
Parametric Study on the Effect of Axial Force on the Seismic Performance of the Bar Damper
A bar damper (BD) is an energy-absorbing device that, despite its simplicity, exhibits excellent energy absorption capacity. The parametric studies in this research focused on the effect of axial force on the cyclic behavior of these dampers. Initially, to verify the results of the numerical model, three experimental BD samples with different heights were utilized. After calculating the buckling load of BD, the effect of 2% and 4% of this load on its cyclic behavior was investigated. The effect of axial force and damper dimensions on its seismic parameters was assessed through nonlinear static analyses. These parameters included initial and effective stiffness, strength, energy dissipation, and equivalent damping ratio (EDR). Additionally, based on the curve fitting method for estimating the initial stiffness of the damper under axial force, an approximate equation was provided, which showed acceptable accuracy compared to the numerical results. The results indicated that the axial force led to a reduction in elastic stiffness, effective stiffness, and strength of the damper, especially at large deformations. The impact on energy dissipation was negligible, but it caused an increase in the EDR. The greatest impact of the axial force was observed on the strength, followed by its effect on the EDR.
Modified Correlations to Predict Shear-wave Velocity Using Cone Penetration Test Data for Hungary
This study evaluates and optimizes empirical correlations between shear wave velocity (Vs) and cone penetration test (CPT) data for various soil types in Hungary. A comprehensive database of 914 data pairs was compiled from multiple cities with diverse geological conditions, incorporating SCPTu and MASW measurements. Over 40 existing Vs–CPT correlations were statistically assessed using parameters such as RMSE, RD, K, CVK, and RI to determine their accuracy across different soil types and depositional settings. The most promising correlations were further refined using regression analysis, leading to the development of improved models tailored for Hungarian soils. These new correlations were evaluated both graphically and statistically, showing enhanced predictive performance, particularly for coarse-grained soils. The final proposed models demonstrate significant reductions in estimation error, with RMSE improvements exceeding 35%. This work provides geotechnical engineers in Hungary with robust, site-adapted tools for seismic site characterization and supports safer and more reliable subsurface profiling practices.
Durability Indices of a Sealing Mortar Incorporating Blast Furnace Slag
Ground granulated blast furnace slag generated from steel manufacturing presents environmental challenges, but it can be valuable when utilized as a supplementary material in concrete, contributing to the development of sustainable materials. In this research, a new sealing mortar was prepared by substituting 10% of the cement with slag (M10). This material can provide performance comparable to M234, a M0 sealer used for sealing and wedging supports and machine bases. The mechanical properties and durability indices of both M10 and M234 were compared to the reference mortar MISO, which is a laboratory-made mortar free of slag. XRD analysis was conducted to determine the crystallinity of the starting cement, and granulometry revealed a median size distribution of 23 μm for the slag after grinding. Capillary absorption and water-accessible porosity were tested for all samples.
Behavior of Flat Slabs with Partial Use of SIFCON Subjected to Concentrated Loading
This research investigates the applicability of slurry-infiltrated fiber concrete (SIFCON) to enhance ductility and punching shear capacity. In addition, especially since the SIFCON mortar is considered self-compacting, thus reduces the labor costs associated with concrete vibration. Eight flat slabs with dimension 600 × 600 × 60 mm, were cast and tested under concentrated loading. The main experimental parameters investigated were the type of concrete (NSC and SIFCON), the placement of SIFCON within the slab, and the proportion of the slab area composed of SIFCON. Among the tested specimens, one slab was constructed entirely with NSC and another entirely with SIFCON; these two slabs served as reference specimens for comparative evaluation. The experimental results are presented, including maximum load, deflection, ductility, and rotation, as well as the crack pattern of each specimen and the inclination of cracks. According to the test results, punching shear of RC slabs and deformation capacities are considerably increased by using SIFCON. The percentage increase in punching shear capacity of the slab with SIFCON layer 40 mm in the tension face was 112%, and the ductility of the slab with SIFCON layer 20 mm in the tension face was 117%, compared with the reference slab. Furthermore, by increasing the post-punching deformations of slabs, the strengthening approach may also be applied to prevent structures from collapsing suddenly following punching shear failure.
Enhancement of Sulfate Resistance in Dune Sand Mortars through Polypropylene Fiber Incorporation
This study investigates the impact of different polypropylene fiber (PPF) dosages (0.1% and 0.15%) and lengths (12 mm and 18 mm) on dune mortar (DM) modified with river sand (RS) at a replacement ratio of 50%. The main objective is to evaluate the durability of this fiber-reinforced mortar in a sulfate-rich environment. Compressive strength was assessed at 28, 60, and 180 days, along with mass loss and strength degradation analyses. Microstructural characteristics were examined by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). while porosity (P) and sorptivity tests were performed to evaluate permeability. The results reveal that PPF reinforcement significantly enhances sulfate resistance, reducing deterioration rates in mass and compressive strength by up to 46% and 40.87%, respectively. Additionally, water absorption and sorptivity coefficient (S) decreased to 83.91% and 86.36%, respectively, compared with the control. The synergy between modified sand content and PPF reinforcement demonstrates potential for improving sulfate durability, making it a viable solution for concrete applications in aggressive environments.
Effects of Core Drilling Location on the Response of Eccentric Axially Loaded Columns under Cyclic Lateral Loads
In evaluating the performance of existing reinforced concrete buildings, compressive strength is determined by core samples taken from the structural elements. Regarding ease of application, the core area is selected as close to the column's bottom as possible. Although studies in the literature and relevant regulations state that coring should be done from the middle area of the columns, there is no evaluation of the behavior of the columns under different loading conditions. Besides, the location of the cored area can be ignored for symmetrically loaded columns; it will vary for eccentric axially loaded columns, which are frequently encountered in practice. Only axial load has been considered for the evaluations in studies investigating the effect of the cored area on the load-bearing element. However, this should also be evaluated under horizontal cyclic loadings that change the tensile and compressive zones of the load-bearing element. Therefore, this study aims to determine the most suitable coring area on the column by considering the literature, regulations and application situations in reinforced concrete columns subjected to eccentric axial loading and horizontal cyclic loading with the finite element method. In addition, the study aims to provide an academic basis for the importance of loading type (symmetric/eccentric) in selecting the core drilling area, which is often determined randomly in practice.
Post-Grouting Behaviour of Ground Anchors in Dense Cohesionless Soils: Field Observations and Theoretical Insights
Post-grouting is a widely adopted technique in ground anchor systems intended to enhance grout–soil interaction through pressure-induced mechanisms. It is generally assumed to improve load transfer by inducing fissures in the initially set grout, expanding the grout body, and enlarging the fixed-length diameter. This study investigates grout behaviour under post-grouting pressure in dense cohesionless soils using data from 870 post-grouted anchors installed at nine construction sites in Budapest, Hungary, with similar ground conditions. Grouting volumes were statistically analysed, focusing on the correlation between grouting volumes and their relationship to soil properties particularly grain size distribution. Theoretical grout body diameters were estimated using expansion and infiltration models. Load–displacement test data were used to back calculate apparent free lengths and infer fixed lengths, which were compared with literature values. Two post-grouted test anchors were excavated. Both showed uniform diameters matching the original borehole, with no signs of grout body enlargement. However, large irregular grout masses were found in permeable zones, suggesting material migration toward weaker paths under pressure. These findings indicate that in medium dense to dense sands, post-grouting enhances performance primarily through local soil densification not geometric expansion, highlighting the need to revise traditional assumptions regarding grout behaviour in such conditions.
Sustainable Utilization of Red Mud and Glass Waste in Alkali-Activated Cements: Design and Performance of Products
Red mud (RM) is a hazardous waste that is generated in large quantities, and its sustainable, rational treatment and recovery is still a challenge. The aim of this research is to develop higher added value alkali-activated cements (AACs), which, by using red mud, can help to protect limited resources, reduce pollution, and produce alternative, "greener" building materials. During this work, industrial waste materials – blast furnace slag, red mud, and glass waste – were used to produce AACs suitable for traditional construction applications (e.g., load-bearing structures, foundation blocks, and walkways). Key parameters including the maximum RM content (recommended 21.7 wt% to maintain sufficient strength), composition of the activating solution, liquid/solid ratio, particle size, and reactivity of the glass waste were optimized. Glass waste reactivity was enhanced by high-energy grinding at 200 rpm for 90 minutes, resulting in a maximum compressive strength of 66.8 MPa, exceeding the highest strength class defined by relevant standards (EN 197-1). Mechanical properties were supported by microstructural analyses (SEM, FT-IR), and heavy metal behavior was assessed through leachate and adsorption tests. The AACs effectively immobilized heavy metals such as Cd, Ni, Pb, and Hg, with long-term leaching resistance and improved retention capacity compared to Portland cement-based mortars. Additionally, powder-based Pb2+ adsorption tests confirmed that RM-containing AACs offer enhanced performance in removing lead from aqueous solutions. Overall, these binders – containing up to 71.4 wt% combined industrial waste – demonstrate competitive mechanical and environmental properties, contributing to sustainable construction practices and potential wastewater treatment applications.
Advanced Hybrid AI Models for Predicting Softening Point and Penetration of Modified Bitumen
Ensuring bitumen quality is essential for the durability of asphalt pavements. Conventional laboratory tests for softening point (SP) and penetration (P) are reliable but labor-intensive and time-consuming, particularly for modified binders incorporating recycled additives. This study proposes an advanced hybrid machine learning (ML) framework integrating Neural Architecture Search (NAS) with Artificial Neural Networks (ANN) to predict the SP and P of modified bitumen containing crumb rubber (CR), coffee grounds (CG), and olive pomace (OP). A dataset of 49 laboratory-prepared samples was used to train and validate three models – Random Forest (RF), ANN, and NAS-ANN – evaluated through statistical indicators (MSE, RMSE, R2, R). The NAS-ANN achieved the best performance, with R = 0.9665/0.9567 for SP and 0.9726/0.8711 for P (training/validation). Sensitivity analysis indicated that OP had the most significant influence on SP, followed by CR and CG. The optimized NAS-ANN model was implemented in a user-friendly interface named SmartBit-AI, designed to facilitate rapid prediction and mix-design preselection. Overall, the proposed NAS-ANN framework complements conventional laboratory testing, offering a practical and efficient tool for accelerating sustainable bitumen evaluation and design.
On the Long-term Deflection Behavior of Timber–concrete Composite Slabs
This paper investigates the long-term behavior of cross-laminated timber (CLT)–concrete composite (TCC) slabs through a large-scale parametric study using a two-layer finite-element model with interface springs to represent partial interaction. The study isolates the influence of four parameters—concrete shrinkage (modeled via relative humidity, RH), composite factor (γ), concrete creep coefficient (φ), and timber creep coefficient (Kdef)—on time-dependent deflections. A total of 36,864 analyses were performed for a 6 m span under quasi-permanent loading, with results normalized to the least-deflecting case in each subset. For a representative configuration (CLT 120 mm, concrete 50 mm) and RH = 60%, the normalized 50-year deflection increases by approximately 22% with higher shrinkage, by 6% when reducing γ from 0.9 to 0.3, by 8% when increasing φ from 1.5 to 3.0, and by 12% when increasing Kdef from 0.6 to 1.0. Across configurations, shrinkage is consistently the dominant driver. Moreover, shrinkage-induced deflection scales approximately linearly with the distance from the centroid of the concrete layer to the composite neutral axis (Zna), highlighting geometry as a primary design lever. The design implications are as follows: 1. prioritize low-shrinkage concrete mixes; 2. avoid intentionally reducing γ, as global stiffness and overall performance deteriorate; and 3. select layer proportions that minimize Zna while balancing the stiffness gains and shrinkage sensitivity associated with thicker concrete toppings.
An Integrated Time-frequency Framework for Cable Force Identification in Long Cables of Long-span Bridges
Accurate identification of cable forces is crucial for the Structural Health Monitoring (SHM) of long-span cable-stayed bridges. However, vibration-based methods face significant challenges when analyzing closely spaced high-order frequencies in long cables, including the difficulty of identifying low-order frequencies and the propensity for modal aliasing. This paper proposes a novel integrated time-frequency analysis framework to automatically identify cable frequencies from vibration data without prior information. The framework employs a hierarchical approach where the Secondary Fourier Transform (SFT) first automatically estimates the fundamental frequency difference, thereby enabling two advanced techniques: the modified short-time Fourier transform (MSTFT) for sparse modal identification and the modified Hilbert transform (MHT) for high-precision instantaneous frequency (IF) tracking. Several long cables in a certain long-span bridge were employed, and the results demonstrated that the framework successfully identifies cable frequencies from higher-order modes (10th to 15th order), effectively compensating for weak low-order signals. SFT provided a rapid and robust estimation of the average frequency difference. Building on this, MSTFT enabled the sparse frequency identification of designated modal orders, while MHT precisely captured IF fluctuations, revealing dynamic force changes that correlated with peak traffic periods. The proposed integrated framework offers a powerful and adaptable solution for cable force identification. The proposed framework automates the analysis, mitigates modal aliasing, and accommodates multi-precision requirements. This enhances traditional vibration-based monitoring, delivering a robust solution for SHM systems to better assess operational safety and optimize the maintenance of long-span bridges.
Coexisting with Disasters: A State-of-the-art Review of Resilience Assessment of Steel Structures under Extreme Hazards
The current era of structural design prioritizes safety, performance, and compliance with evolving standards. While these advancements have undoubtedly improved structural integrity, safety is no longer sufficient. The increasing frequency and intensity of natural disasters, including seismic events and tornadoes, along with human-induced hazards, such as blasts, demand a broader and more adaptive design philosophy. This paradigm is resilience, a concept that not only addresses immediate structural survival but also considers recovery, functionality, and the broader physical, social, and economic impacts of disasters. Resilience-based design surpasses conventional approaches by accounting for indirect consequences, such as downtime and cascading effects, and emphasizing recovery and long-term societal well-being. This paper presents a state-of-the-art review of resilience assessment for steel structures subjected to lateral loads from seismic, blast, and tornado hazards. Which impose significant demands on structural integrity and resilience due to the extreme forces they exert, making them critical in resilience assessment. The limitations of current design codes, such as the Eurocode, are critically examined, focusing on their emphasis on life safety over recovery and their lack of multi-hazard frameworks. Future directions are explored, including the adaptation of design codes to incorporate multi-hazard resilience, the integration of advanced materials, and the development of quantifiable resilience metrics. By addressing these challenges, this paper emphasizes the need to transform structural engineering to ensure that steel structures can coexist with disasters. The insights presented aim to promote the development of novel approaches and methodologies that enhance resilience as a core principle in structural steel design.
The Role of Management Theories and Tools in Creating Added Value: Insights from the Prefabricated Residential Building Sector
The study investigates how management tools impact value creation across different approaches. It identifies key value-creating trends, analyses relevant tools, and provides a framework to support companies in selecting optimal strategies. A unique concept of value creation was developed, incorporating consumer expectations, corporate innovation, and competitiveness. Furthermore, cross-disciplinary concept of added value was developed. The research examined 27 management theories and tools using narrative literature review and thematic analysis, demonstrating how classical models enhance efficiency, while modern approaches prioritise adaptability and employee motivation. Classical management theories primarily improve value creation by optimising organisational processes and increasing productivity. Meanwhile, contemporary approaches focus on fostering innovation, customer engagement, and corporate social responsibility. Management tools play a crucial role in improving organisational efficiency, competitiveness, and sustainability. Techniques such as CRM systems, SWOT analysis, and Porter’s competitive strategies help companies optimise operations, enhance decision-making, and drive strategic growth. Additionally, process improvement methodologies contribute to increased customer satisfaction, innovation capabilities, and strengthened corporate relationships. The study also explores the prefabricated residential building sector, highlighting the widespread adoption of the Lean Construction approach. This method supports efficiency, waste reduction, and sustainability, making it preferred strategy in the industry. The findings conclude that continuous development and integration of management tools are essential for long-term competitiveness. Companies that strategically apply these tools within their governance structures achieve qualitative growth, market advantage, and sustainable business practices. By aligning management strategies with value creation, organisations can enhance adaptability, optimise performance, and reinforce their commitment to innovation and customer satisfaction.
Experimental Characteristics Impact on Bond Strength at Elevated Temperatures: A Literature Review
Evaluating structure strength characteristics post-fire or when subjected to prolonged periods of elevated temperature is essential, as these conditions degrade concrete strength, specifically bond strength between rebar and concrete. Residual bond strength can be determined through direct pull-out or beam tests. Several factors influence bond strength at normal temperatures, including the properties of the concrete and the rebar, the specimens' characteristics, the concrete cover, and the stress state of the specimen during testing. The situation becomes more complex at higher temperatures as heating introduces additional variables. In this context, the bond is influenced by the heating characteristics of the specimen, such as the heating rate and cooling process. While researchers acknowledge these factors, the degree of their impact is still a subject of debate. This paper aims to review the existing literature on bond strength at elevated temperatures and to explore how various factors influence this strength under such conditions. The study gathers data to examine the bond-slip curve at high temperatures, the effects of experimental variables on bond strength, and the residual bond strength after exposure to elevated temperatures. Key experimental characteristics considered in this paper include the heating procedure, heating rate, heating duration, cooling regime, properties of the rebar, properties of the specimen, and the relationship between concrete strength and bond strength.