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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Case Study: Numerical Investigation of Lateral Stability of Non-prismatic Double Web-tapered Prestressed Reinforced Concrete Girder
This study presents a comprehensive numerical investigation into the lateral stability of non-prismatic, double web-tapered prestressed reinforced concrete girders using advanced finite element modeling (FEM) in ATENA-GiD, validated against experimental results. The analysis examines the influence of key parameters, including initial lateral imperfections (ILI), rubber bearing pad stiffness, concrete tensile strength, load application method, and the effectiveness of fork support restraints. Results reveal that increasing ILI amplifies mid-span lateral displacement by up to 55%, compromising stability. Conversely, stiffer rubber pads improve restraint performance, reducing lateral displacement by 42%, while higher concrete tensile strength decreases lateral displacement by 32% and delays crack formation. Additional parametric studies highlight that the application of eccentric loads, common in experimental and real-world setups, induces secondary torsional effects that reduce lateral stability. A centric load application condition improved performance by reducing lateral displacement by 14%. Moreover, incorporating fully hardened fork supports at girder ends led to a 60% reduction in out-of-plane displacement, demonstrating their essential role in suppressing lateral-torsional buckling. These findings underscore the critical importance of accounting for geometric imperfections, support detailing, load positioning, and material properties in the design of slender, long-span, non-prismatic girders to ensure optimal stability and structural safety.
Copyright (c) 2025 Periodica Polytechnica Civil Engineering
Study of the Microstructure and Permeability of Building Stone Using X-ray Micro-tomography
Fluid transport and storage properties of porous rocks are closely related to their microstructure. Porosity is one of the most important microstructural parameters due to its importance for transport of water, gases and dissolved salts, but also for mechanical, deformation and durability properties of geomaterials used in constructions. In this study, the X-ray computed micro-tomography (XCT) was used to study the spatial distribution of porosity and permeability within the Kocbeře sandstone, which represents a very well-known and long-term used building stone in the territory of the Czech Republic. The microstructure and composition of the Kocbeře sandstone were characterized by a complex of methods, including optical polarization microscopy, scanning electron microscopy coupled with energy dispersive spectroscopy, X-ray powder diffraction, X-ray fluorescence spectroscopy and mercury intrusion porosimetry (MIP). Values of porosity and permeability of the Kocbeře sandstone derived from XCT were compared with results of MIP as well as laboratory measurements of open porosity, hydraulic conductivity and gas permeability. A very good compliance was found between the average values of sandstone porosity determined by the XCT imaging analysis, MIP and experimentally determined open porosity. However, considerable heterogeneity of porosity in the individual analyzed subvolumes was detected using XCT. Very significant inhomogeneity was also found in the spatial distribution of permeability tensors calculated for individual subvolumes. The considerable dispersion of porosity and permeability values of sandstone at the microscale is given by its microstructure. The main role here is played by intense secondary silicification, which unevenly affects the clay matrix of the sandstone.
Copyright (c) 2026 Periodica Polytechnica Civil Engineering
Simplified Analysis of Tall Buildings for Soil–structure Interaction in Uniform and Non-uniform Buildings
This paper presents a continuous analytical model for evaluating the static and dynamic response of tall buildings considering soil–structure interaction. The structure is represented as a parallel coupling of a bending beam and a shear beam, connected by rigid horizontal links, and supported by translational and rotational springs that account for foundation flexibility. The governing equations are derived via Hamilton's principle, explicitly including both translational and rotational inertias. For buildings with uniform properties, closed-form solutions are obtained using the Laplace transform. To extend the formulation to non-uniform buildings, a modified transfer matrix method is introduced that avoids matrix inversion, thereby reducing computational cost. Parametric studies highlight the sensitivity of natural frequencies to soil flexibility and demonstrate the influence of rotational inertia on higher vibration modes, which is often neglected in previous studies. The formulation is restricted to the linear elastic range and does not incorporate second-order (P–Δ) effects or material plasticity, thereby delineating its applicability to structures without significant geometric or material nonlinearities. Numerical comparisons with finite element results confirm the accuracy and efficiency of the proposed approach, providing a practical tool for the preliminary design and performance assessment of tall buildings on flexible foundations.
Effects of Expanded Polystyrene Beads and Printing Direction on Printable Epscrete Properties
This study investigates the effects of expanded polystyrene (EPS) beads and printing direction on the fresh and hardened properties of 3D printable lightweight concrete (epscrete) mixtures. In the experimental studies, control samples containing only sand, mixtures containing only EPS and sand-EPS mixtures with different ratios were prepared and various experiments such as workability, shape retention, unit weight, ultrasound transmission velocity, compressive strength, flexural strength and splitting tensile strength tests were performed on these specimens. In addition, the effects of printing and loading directions on the mechanical strength of epscrete mixtures were investigated. The results show that EPS beads improve the rheological properties of fresh concrete and increase workability, but cause a significant decrease in shape retention ability, especially at high EPS ratios. In terms of hardened concrete properties, it was determined that mechanical strength decreases as the EPS ratio increases, but sufficient load-bearing capacity can be provided with compressive strengths exceeding 30 MPa in all directions in mixtures containing 50% EPS. In addition, higher compressive strength is observed under loading perpendicular to the printing direction, while the strength is lower on the interlayer bonding surfaces. Microstructure analyses revealed that ettringite formations are intense in the transition zone between EPS and cement matrix and this increased porosity within the structure adversely affects the overall strength. These results show that lightweight concretes with EPS content, known for their advantages such as lightness and thermal insulation, have potential for 3D printable low-rise and lightweight building applications.
Determining the Actual Shape of a Bridge Pylon with Cylindrical and Conical Shapes Using Point Cloud Data and the RANSAC Shape Fitting Method
Determining the shape and deformations of structures with complex geometries has become an increasingly common task in the construction industry. This article presents a case study on determining the shape and deformation of a slope and circular steel structure, a cigar-shaped cable-stayed bridge pylon with varying cylindrical and conical shapes during three key construction stages using terrestrial laser scanning (TLS) point cloud data and the Random Sample Consensus (RANSAC) algorithm for shape fitting. A methodology involving vertical reorientation, point cloud slicing, and RANSAC-based circle fitting was applied to cross-sections of the pylon. Optimal RANSAC parameters were determined to be 80 iterations and a 5 mm tolerance, achieving reliable circle fitting with root mean square (RMS) errors predominantly within 3 mm across all scans. After initial steel frame installation, geometric distortion analysis revealed minimal deviations within a 2 mm radius error, a slight increase after concrete pouring, and a partial recovery in the final stage, except for a localized anomaly at the pylon's top. Deformation analysis along the pylon's axis showed maximum horizontal displacements of 65 mm according to the static models in the first scan, reaching a maximum of 269 mm after pouring concrete, with a subsequent reduction and change in direction after cable tensioning. This research demonstrates the efficacy of TLS and RANSAC for evaluating structural deformation and emphasizes the importance of parameter optimization for accurate point cloud analysis in complex civil engineering structures.
Seismic Response Prediction of 3D Reinforcement Concrete Frames Using Machine Learning Methods
This study presents a machine learning (ML) framework to forecast the nonlinear seismic behavior of three-dimensional (3D) RC moment-resisting frames, utilizing OpenSeesPy for realistic 3D modeling and nonlinear time-history analysis (NLTHA) with 110 far-field ground motions from the PEER database. A dataset of 29,700 samples was compiled, spanning 4-, 8-, and 12-story buildings with varied geometries and material properties. Seismic responses, including maximum drift, inter-story drift, and roof drift, were predicted via algorithms such as Extra Trees Regressor (ETR), Random Forest (RF), Gradient Boosting Regression (GBR), and XGBoost. Feature importance identified building height, width, Housner Intensity (HI), and Acceleration Spectrum Intensity (ASI) as key inputs. For inter-story drift, R2 scores varied by height: for 4-story, ETR (0.9388), RF (0.9289), GBR (0.9226); for 8-story, RF (0.9833), GBR (0.9787), ETR (0.9781); for 12-story, GBR (0.9827), ETR (0.9798), RF (0.9622). For maximum drift, XGBoost achieved 0.9684, ETR 0.9678, and RF 0.9612.
Impact of Environmental Pressure Changes on High Precision Measurements
Stable environmental temperature is essential for high precision measurements. Underground caves, or underground laboratories, far from the entrance are generally assumed to provide such ideal, extremely stable environment. However, atmospheric pressure variations have an indirect effect on the temperature of such sites. Two relevant effects are adiabatic temperature change and pressure-dependent self-heating of electronic instruments. In this study a 64-days long temperature timeseries recorded by a tilt-meter was analysed to identify and characterize these effects. We found that large, slow temperature changes can be removed properly, allowing both of the aforementioned effects to be detected in the residual. Furthermore, some key parameters of the pressure–temperature transfer function can be estimated. However, a precise model of pressure dependence could not be obtained, possibly due to the nonlinear behaviour of the process and/or insufficient excitation levels. The results demonstrate that these two effects impose opposite requirements on the instrument’s thermal insulation of the instrument. Consequently, either these effects should be taken into consideration, or the generated heat should be conducted away through a properly sized metallic path eliminating the pressure dependence of self-heating.
Fragility-based Seismic Assessment of Reinforced Concrete Frame–tube Tall Buildings Incorporating Soil-structure Interaction
Rapid urbanization and limited available land have increased the construction of high-rise buildings, highlighting the importance of realistic seismic vulnerability assessment in performance-based design. This study analyzes the probabilistic seismic behavior of a 33-story reinforced concrete frame–tube building with core shear walls, modeled according to Iranian seismic codes. Nonlinear Incremental Dynamic Analysis was conducted in MIDAS software under both Fixed Base and Soil–Structure Interaction conditions, using ground motions scaled between 0.1 g and 1.5 g. Fragility curves were generated based on peak inter-story drifts corresponding to four damage states: Slight, Moderate, Extensive, and Complete. Results show that including SSI leads to significantly higher seismic vulnerability, with the structure reaching equivalent damage states at lower PGA levels than the fixed-base model. SSI also causes period elongation and greater deformation demands, indicating the need for enhanced foundation stiffness, soil improvement, or the application of energy-dissipation and isolation strategies to reduce adverse effects. Moreover, comparison of long- and short-period ground motions reveals that the building is more vulnerable to long-period events, especially when SSI is considered. Median PGA thresholds consistently show lower values for SSI across all damage states, confirming the importance of accounting for soil–structure interaction in seismic evaluation. While the results are specific to the soil and structural characteristics studied, the observed trends such as increased seismic demand and vulnerability due to SSI are expected to be applicable to similar high-rise buildings and highlight the need for integrating SSI into future seismic assessments.
Reliability Assessment of Local and Global Buckling Resistances for Reclaimed Welded Box-section Columns
This study presents an enhanced method for evaluating the buckling resistance of reclaimed steel members by proposing modified local and global buckling formulas that align with the safety provisions of the Eurocode. Standard Eurocode formulas for local and global buckling resistance are insufficient for reclaimed members, as they do not account for the standard-based imperfection magnitudes and residual stress states commonly observed in reclaimed structures. To address this gap, new buckling resistance formulas were developed and calibrated through advanced geometrically and materially nonlinear analysis with imperfections (GMNIA). The reliability of the proposed formulas is evaluated in accordance with Annex D of EN 1990, enabling the derivation of appropriate partial safety factors for both local and global buckling modes. An additional safety factor is introduced to capture the interaction between these modes, ensuring a reliable safety assessment. The current study provides engineers with a practical method for evaluating the buckling capacity of reclaimed steel members, promoting safe and sustainable reuse in structural applications.
Evaluation of the Two Faces Water Level Dynamics and its Impact on the Stability of Railway Embankment Infrastructures
The Nanhu railway embankment, located between two lakes, experiences seasonal water level fluctuations. This study aims to assess the impacts of these fluctuations on embankment seepage, stability, and deformation conditions. Firstly, field observations and laboratory experiments were conducted to determine the hydro-mechanical properties of the embankment material and the drawdown scenarios. Subsequently, GeoStudio 2D and PLAXIS 2D software were used for numerical analysis. The analysis demonstrates that the combined impact of a train static load (130–150 kPa) with lowering drawdown and increasing water level scenarios affects the stability of the embankment, resulting in more deformation than the falling scenario. The model result showed a maximum displacement of 238.43 mm, which was corroborated by the observed field data. Furthermore, the rising scenario had a minimal safety factor of 0.9128, and the falling scenario yielded a minimum safety factor of 0.9312, indicating severe instability. Furthermore, the findings indicate that understanding the relationship between safety factors, pore-water pressure, deformation, and train static load for an embankment infrastructure can aid in the stability management of multi-face water level fluctuation conditions. To prevent embankment failures, simplified preventive approaches are analyzed, and it is discovered that the steel-pipe grouting consolidation method can potentially enhance embankment stability by 50%.
A Universal Recursive Analytical Solution of the Nonlinear Storage Equation for Flood Control Reservoir Sizing
The nonlinear storage equation to arbitrary inflow rates is solved for the outflow time-series by recursively employing the analytical solution of the linear storage equation evaluated at each time-increment with an updated storage coefficient value. As the procedure is fully analytical it avoids any problems a numerical solution may present.
Algorithm for Generating Gradient Infills in Load-bearing 3D-printed Parts
In many applications, it is crucial to design load-bearing elements that meet strength and stiffness requirements while minimizing material usage. Using additive manufacturing (AM), these goals can be achieved. With 3D printing technology is possible to create an internal structure — referred to as infill or lattice structure — generated by a dedicated algorithm. A special place is occupied by functionally graded lattice structures (FGLS), which are generated with tunable properties. which is the focus of this article. The primary objective of this algorithm is to create an internal parametric structure with variable thickness for any given cross-sectional shape. Secondary, the algorithm can calculate its cross-sectional characteristics. To evaluate its functionality and effectives, a series of 9 virtual models of cross-sections with 2 varying parameters were generated and subsequently compared with numerical models.
SMAP Soil Moisture Measurement in Hungary over Agricultural Land
Monitoring spatial and temporal dynamics of soil moisture is essential for managing hydrological extremes such as droughts and inland excess water. This study assesses the accuracy of NASA's Soil Moisture Active Passive (SMAP) Level 3 soil moisture product using long-term in situ measurements (2016–2024) from the national drought monitoring network in Hungary. Two distinct 36 km satellite footprint cells were extensively analyzed, representing different land use and soil type conditions. Daily averaged in situ soil moisture data measured in the upper 10 cm layer were compared to SMAP observations for both AM and PM overpasses. Statistical metrics used to evaluate performance include the Pearson correlation coefficient (R), bias, root mean square error (RMSE), and unbiased RMSE (ubRMSE). Results indicate that PM values generally exhibit stronger agreement with in situ measurements. The SMAP product met the <0.04 m3/m3 ubRMSE validation requirement threshold over several years and locations, particularly in areas with homogeneous soil conditions. However, variability in soil types and topography in more heterogeneous regions highlights the need for additional ground-based measurements and higher-resolution satellite data to enhance local-scale validation.
An Automated Bipartite Graph-based Force Method for Efficient Analysis of Planar Trusses
Efficient analysis of structures refers to the methods which reduce the computational cost of the structural analysis. To achieve this, the structural matrices should have some specific attributes. For this purpose, a graph theoretical force method is employed in this study, which leads to a sparse flexibility matrices. In this method, the bipartite graph corresponding to the equivalent graph of the original structural model is constructed. A cycle basis of the bipartite graph corresponds to subgraphs of the structural model on which localized self-equilibrating stress systems can be formed, referred to as a generalized cycle basis of the structure. This enabled the authors of this study to develop a fully automated procedure for the efficient analysis of planar trusses using a graph-theoretical force method. The proposed approach combines classical structural mechanics with the concepts of graph theory. In other words, a bipartite graph approach is employed for a systematic identification of self-equilibrating stress systems in the truss structures. The entire procedure is implemented in MATLAB, allowing all steps to be performed automatically and three different planar trusses are solved using proposed method.
Seismic Resilience Analysis of Steel Moment Frames Equipped with Dissipative Replaceable Devices
This study aims to probabilistically evaluate the seismic resilience of steel structures equipped with dissipative and replaceable components. These elements are specifically designed to enhance the repairability of the structures, thereby minimizing downtime and facilitating rapid post-earthquake recovery. Moreover, the effects of dissipative replaceable devices on fragility and vulnerability estimates are investigated. This study examined two steel buildings, a 6-story and a 12-story structure, considered under two distinct configurations: conventional moment-resisting frames and frames equipped with dissipative replaceable links. Preliminary designs were first developed, followed by the creation of detailed nonlinear models in OpenSees. The seismic performance was then assessed through Incremental Dynamic Analysis using a set of generic ground motion records. For each damage state, distinct recovery functions are defined, and 500 realizations are generated through the Latin Hypercube sampling technique to construct probabilistic resilience curves. The results demonstrate that incorporating dissipative replaceable devices significantly enhances the seismic performance and resilience of steel structures. Compared to conventional frames, link-equipped frames exhibited reduced inter-story drifts, leading to lower non-structural damage and concentration of inelastic demands in replaceable links rather than primary members. Fragility analysis confirmed a reduction in the probability of damage states, particularly at life safety and collapse prevention levels. Resilience indices further highlighted the superior functionality retention and faster recovery of frames with replaceable links, especially under strong earthquakes. Comparative assessment of 6- and 12-story buildings indicated that the benefits of dissipative links are consistent across different heights, with even greater improvements observed in taller structures.
An Efficient Kriging Surrogate Model for Developing Seismic Fragility Curves of Low-rise Steel Structures Considering Epistemic Uncertainties
Seismic fragility curves are essential for assessing structural performance under earthquake loading; however, their development requires addressing both aleatory and epistemic uncertainties, which can be computationally intensive. This study introduces an efficient Kriging-based surrogate modeling framework for deriving collapse fragility curves of steel moment-resisting frames while explicitly incorporating uncertainties in key hysteretic parameters. Incremental Dynamic Analysis (IDA) is conducted on a 5-story steel frame using 22 far-field ground motions and 125 structural parameter scenarios, reflecting probabilistic variability in plastic rotation capacity, post-capping rotation, and cyclic deterioration. The Kriging surrogate is calibrated using maximum likelihood estimation, enabling accurate interpolation of nonlinear structural response behavior. Validation results demonstrate a prediction accuracy of R2 = 0.92, outperforming the conventional response surface method (R2 = 0.88). Additionally, the Kriging model reduces mean collapse capacity prediction error to 0.5%, compared to 24% in the response surface approach, while maintaining significantly lower computational cost. The proposed methodology provides a computationally efficient and uncertainty-aware framework for collapse fragility curve development, supporting performance-based seismic design and risk assessment.
Investigating Deep Learning Colorization of Terrestrial Laser Scanning Point Clouds for Calibration-light and Rapid Visualization
Terrestrial laser scanning (TLS) is widely used for generating accurate, high-resolution colored point clouds. However, a significant portion of the time at each scanning station is dedicated to capturing and stitching panoramic images for accurate colorization. For applications where precise colors are not critical, pseudo-colored point clouds can serve as a faster and computationally efficient alternative, particularly for presentations and qualitative analysis. This study proposes a novel pipeline leveraging advancements in deep learning-based photo colorization to pseudo-color point clouds. By treating the intensity maps from TLS as single-channel grayscale images, we apply pretrained deep learning models from the DeOldify library, trained with NoGAN techniques, to generate realistic pseudo colors. Indoor and outdoor TLS scan slices are showcased before and after pseudo colorization. The resulting, colored intensity maps are used to colorize point clouds, creating visually compelling representations. We compare these pseudo-colored point clouds with traditionally colorized counterparts that utilize RGB imagery. The results demonstrate that pseudo-colored point clouds can effectively enhance human evaluation and visualization tasks, providing a valuable tool for scenarios where real colors are unnecessary.
Enhancing Mechanical Performance of Hemp Fiber-reinforced Cementitious Composites
Over the past decade, cement-based composites incorporating natural fibers have emerged as promising alternatives to conventional building materials due to their environmental benefits. The current trend in sustainable construction highlights the growing interest in bio-composites, particularly mortars reinforced with vegetable fibers, which combine technical efficiency with ecological responsibility. Compared to conventional mortars, these bio-composites reduce environmental impact, improve energy efficiency through their low density, and offer enhanced crack resistance and durability under flexural stresses. Hemp fibers, with their complex internal structure and mechanical resilience, are particularly suited for reinforcing cementitious matrices. This study examines the integration of hemp fibers into cement-based composites, aiming to enhance their mechanical performance for construction use. The fibers underwent alkali treatment with different concentrations of sodium hydroxide (NaOH) and were prepared in various lengths before being blended into the mortar. A design of experiments using Response Surface Methodology (RSM) was employed to evaluate the influence of these variables on compressive and flexural strength, tested after 28 days of curing. The outcomes were analyzed through Analysis of Variance (ANOVA) to identify optimal conditions. Additionally, a predictive model was developed to describe the behavior of the composites under varying treatment parameters. This research offers practical insights into the sustainable development of fiber-reinforced cementitious materials and highlights strategies for optimizing their mechanical performance using natural reinforcements.
Comparative Analysis of the Numerical Model and Geodetic Measurements of the Settlement in the Kobilja Glava Tunnel
This paper presents a comparative analysis of the settlement of the Kobilja Glava tunnel structure, using three-dimensional numerical modeling and geodetic monitoring during construction. The numerical model, developed in the Plaxis 3D software package, included all excavation and support phases, with rock mass parameters defined based on RMR classification and conversion of Hoek-Brown parameters into the Mohr-Coulomb form. The primary lining was modeled using plate elements, while anchors were represented as embedded elements with equivalent elastic modulus. Geodetic measurements were carried out continuously, with measurement points positioned at the tunnel crown, sidewalls, and the bench, providing actual convergence values. Comparison between the numerical model results and geodetic measurements revealed discrepancies ranging from 18% to 24%, with the largest deviations recorded at a distance of 24 m from the excavation face. Statistical data analysis (RMSE ≈ 3.71 mm; σ ≈ 1.21 mm) confirmed the presence of a systematic prediction error, but also the stability of deviations across the analyzed points. The results confirm the technical validity of the applied model and the designed support system, while emphasizing the need for dynamic updating of numerical models in accordance with field data. This further reinforces the implementation of the observational method as a reliable approach under real tunneling conditions.
Toward Carbon-neutral Concrete: Early Age Strength of Mechanically Activated Construction and Demolition Waste-based Binders
There is need to research and develop sustainable building materials from waste and by-products with adequate standards for increasing infrastructural and environmental need occasioned by population increase, modernization, urbanization, environmental and climatic changes concern currently. In unprocessed form it is not possible to up-cycle concrete waste, therefore mechanical activation (MA) technique can be applied to up-cycle waste, through improvement of properties for secondary raw materials. This study focuses on effect of early age compressive strength and MA of construction and demolition waste (CDW) hence advocacy for carbon neural concrete. MA improved the early age strengths of CDW based binder strengths. The finer CDW samples had better strength at 7 days compared to coarser. Generally, reduction of water to binder (w/b) ratio resulted to higher pozzolanic activity index for binders with 25% CDW. The 25% cement replacement with MA CDW as binder replacement was optimum, with highest respective compressive strengths of 67.02 ± 1.56 MPa and 62.82 ± 12.15 MPa, for ranges 5303–8440 cm2/g (average 6872 cm2/g) and 12,102–10,327 cm2/g (average 11214 cm2/g) geometric specific surface areas based CDW's binders respectively. Remarkable strength for MA of CDW could be due to a combination of impact of Si reactivity and filler effect in the CDW. Water content, particle sizes and carbonation had an impact on compressive strengths for binder materials. Inconsistency in particle sizes from different batches was possibly due to the quartz amount.
Assessing the Effects of Motor Oil, Gypsum, and Sodium Chloride on the Behavior of Lime-improved Grey High Plasticity Clay
This study evaluates the effects of motor oil (MO), gypsum (CaSO4·2H2O), and sodium chloride (NaCl) as additives on the geotechnical properties of Grey High Plasticity Clay (GS) improved with 0, 4, and 8% lime (L). Each additive was incorporated into GS at 0, 2, and 4% by dry weight. Unconfined compressive strength (UCS) tests were performed on specimens compacted at their optimum moisture content (OMC) and maximum dry density (MDD) after 7, 30, and 120 days of curing. Results indicated that the plasticity index (PI) of GS decreased with the addition of additives, whether used alone or combined with lime. The introduction of any additive into natural or lime-improved GS enhanced soil classification, with gypsum and NaCl exhibiting a more pronounced effect. Additionally, MDD decreased while OMC increased as lime content rose, due to cation exchange reactions leading to clay particle flocculation. However, MDD increased with higher additive contents, whereas OMC decreased with increasing MO and NaCl but rose with gypsum. UCS values improved significantly with any additive, particularly after 120 days of curing. Microstructural analysis via scanning electron microscopy (SEM) revealed the formation of cementitious compounds and/or ettringite in GS samples improved with lime alone or in combination with gypsum, contributing to strength enhancement.
Numerical Evaluation and Prediction of Bond Performance of Ribbed FRP and Steel Bars in Concrete Using Pull-out Test Simulations
This research investigates the bond behavior between concrete and ribbed reinforcement bars through numerical simulations of pull-out tests, focusing on three types of fiber-reinforced polymer (FRP) bars—Glass (GFRP), Aramid (AFRP), and Carbon (CFRP)—alongside conventional Steel bars, all with diameters ranging from 10 to 14 mm. Steel bars are modeled using a bilinear elastic–plastic constitutive law, while FRP bars follow a linear elastic behavior. The concrete modelled using a Regularized Coupled Damage–Plasticity Drucker–Prager Microplane approach. The interaction between concrete and reinforcement is simulated using a Mohr–Coulomb-type contact interface with friction coefficients tailored to each bar material, also accounting for mechanical interlock through explicit modeling of the rib geometry. The simulation results from the pull-out tests are compared against analytical bond–slip models and predictive formulations for maximum bond stress reported in the literature. Based on these comparisons, a new adapted predictive analytical model is proposed, showing improved agreement with the simulation data. The results indicate that CFRP bars exhibit in general the highest bond stress performance, followed by AFRP, steel, and GFRP. For all bar types, both the maximum bond stress and the corresponding slip decrease with increasing diameter. Steel bars exhibit higher and less predictable slip as a result of plastic deformation, whereas FRP bars demonstrate more stable and predictable behavior owing to their linear elastic response.
Hydrological Mass Variations in Major River Basins in China with the Use of GRACE Monthly Gravity Field Models
Mass redistributions within the Earth system induce changes in the planet's gravity field, observable via the Gravity Recovery and Climate Experiment (GRACE) mission. GRACE data have become essential for monitoring large-scale hydrological processes. While GRACE captures water mass variations at the basin scale, in situ hydrological stations provide localized insights based on water level and volume changes. This study investigates water mass variations across the major river basins of mainland China, aiming to link basin-scale GRACE observations with local in situ measurements. Building on previous findings from the La Plata River basin, this research explores the potential phase lag between GRACE-derived mass changes and tide gauge records. However, no significant phase lag was identified in Chinese basins, likely due to intensive water management practices that also affect subsurface water storage. Nevertheless, the GRACE-derived sur-face mass variations were validated, showing strong temporal and spatial agreement with simulated total water storage anomalies from the CLHMS model and ERA5-Land reanalysis.
Influence of Acidic and Alkaline Environments on the Mechanical Properties of Cement Mortars
Cement-based materials are exposed to various internal and environmental aggressions of acidic and alkaline nature that may affect their durability. This study investigates the influence of aggressive environments on the mechanical and physical behavior of cement mortars. Mortar specimens (4 × 4 × 16 cm3) were prepared with a water-to-cement (w/c) ratio of 0.5 and cured in water at pH 7 for 28 days. Additional specimens were exposed to sulfuric acid solutions at pH 2, 3.5, and 5, as well as alkaline solutions at pH 11 and 12.5. The findings indicate that mortars deteriorate significantly when exposed to acid. Mass losses can reach 20%, compressive strength losses range from 31% to 47%, and tensile strength losses range from 16% to 34%, depending on the acidity. In contrast, alkaline exposure results in a little expansion, which can raise mass and volume by as much as 2.3%. Both the tensile and compressive strength losses remain below 11% and 16%, respectively. In order to clarify degradation mechanisms and guide the development of more resilient cement-based materials, this study compares the behavior of mortar in extremely acidic and alkaline environments.
Combined Effects of Particle Shape and Deformability on Cyclic Shear Response of Sand-rubber Mixtures
In this study, the cyclic response of sand-rubber mixtures was investigated in terms of shape and deformability effects of particles. A series of cyclic simple shear tests were performed using three different sand and two different rubber specimens. The rubber particles were included in the sand samples with five different contents, and the mixtures were loaded until five different shear strain levels. The cyclic response was evaluated using secant shear modulus and damping ratio parameters. The particle deformability and shape effects of the rubber particles were elaborated using local images from the tests. In addition, the mixtures were subjected to California bearing ratio test to correlate the cyclic response with static behavior. The results were evaluated by adopting an interactive approach by considering the shape and deformability of the particles together. It was revealed that the influence of shape and rubber content on the cyclic parameters were found to be highly dependent on the shear strain level. The shear modulus at small strain levels followed similar trends as the bearing ratio in terms of particle shape and rubber content influences. The contribution of sand and rubber particles to the damping ratio varied with the shear strain, and particle shape effects emerged at large strain levels. The local image of the samples reveals that the response of the mixtures is transformed as the rubber particles produce primary force columns. Rubber particles can provide a fiber effect depending on the shape features.
Experimental and Statistical Optimization of Low-carbon Binder Concrete under Varying Alkaline Activator Conditions
This study investigates the mechanical and microstructural performance of fly ash–GGBS-based geopolymer concrete activated using sodium carbonate and sodium silicate in varying ratios (1:1, 1.5:1, and 1:2), with a conventional sodium hydroxide–sodium silicate mix serving as the control. Workability was evaluated through slump tests, while compressive strength was measured at 7, 14, and 28 days. The control mix (NaOH:Na2SiO3 = 1:2.5) achieved a 28-day compressive strength of 48.6 MPa, while the carbonate-based mixes recorded strengths of 44.1 MPa (1:1), 36.3 MPa (1.5:1), and 41.2 MPa (1:2). SEM–EDS analyses confirmed that the 1:1 mix exhibited a dense matrix with a balanced distribution of Si, Al, Na, and Ca, indicative of the formation of both N–A–S–H and C–A–S–H gels. XRD patterns further corroborated the presence of these hydration products, with reduced unreacted phases in the optimized mix. Statistical evaluation using Response Surface Methodology (RSM) and ANOVA identified the alkaline activator ratio as a significant factor influencing compressive strength (p < 0.05), with the model achieving a high coefficient of determination (R2 = 0.985). The predicted and experimental strengths showed close agreement, validating the model's predictive capability. Results demonstrate that a 1:1 Na2CO3:Na2SiO3 ratio provides an optimal balance between mechanical performance and sustainability, making it a promising alternative for high-strength, eco-friendly geopolymer concrete applications.
Influences of the Geopolymer Composition on the Strength and Durability of Fly Ash-based Geopolymer Stabilized Compacted Soil
Compacted earth materials are sustainable construction alternatives, but their durability is commonly enhanced using Portland cement, which has a high environmental impact. Geopolymers offer a potential low-carbon replacement and demonstrate promising mechanical properties, durability, and environmental performance. This study investigates the influence of geopolymer composition on the mechanical properties and durability of geopolymer-stabilized compacted earth (GSCE). Samples were prepared using Na2SiO3/NaOH ratios ranging from 1.0 to 2.0 with 10 M NaOH. In the first stage, compressive strength was optimized by varying curing temperature and curing time. The highest strength was obtained for specimens with a Na2SiO3/NaOH ratio of 1.5, cured at 90 °C for 24 h. In the second stage, durability was evaluated for GSCE prepared under these optimal conditions through wetting–drying cycles (C = 1–12) in tap water, salt water, and acidic solution (pH = 4). Under acidic conditions, compressive strength increased and reached a maximum after six wetting–drying cycles. XRD and FTIR analyses were used to identify phase development and chemical bonding within the geopolymer matrix. The results highlight the potential of geopolymer-stabilized compacted earth as a durable, environmentally sustainable construction material that incorporates industrial by-products.