Challenge Journal of Structural Mechanics
cjsmec.challengejournal.com Challenge Journal of Structural Mechanics is an international, quarterly published and open access scholarly journal that publishes original research articles as well as review articles, case studies, short communications, discussions, book reviews, letters to the editor and a diary on international events related to any aspect of structural engineering. Primary aim of CJSMEC is to encourage academic challenges in structural mechanics and materials disciplines to seek for the global truth. Therefore, the Journal intends to publish at least a review or discussion as a challenge to previously published papers at each issue. A double blind peer-review policy is followed in order to increase the scientific quality of the published papers.
Comparative machine learning study for allowable bearing capacity prediction of OHTL tower foundations with spatially imputed geotechnical borehole databases’ interpretability
Geotechnical site characterization for alignment-based infrastructure projects, such as overhead transmission lines (OHTLs), involves the collection of extensive borehole datasets across hundreds of kilometers and the interpretation of thousands of results from laboratory and in-situ tests. In this study, a machine learning (ML) framework is proposed for predicting the allowable bearing capacity (qₐₗₗ, kPa) of OHTL tower spread footings using geotechnical borehole data. A dataset comprising 89 boreholes with 16 input parameters, including physical, mechanical, and seismic soil properties, was used. Missing borehole records (n=8) were spatially imputed using Inverse Distance Weighting (IDW) and K-Nearest Neighbors regression prior to model training. Ten ML algorithms, including Ridge, Lasso, ElasticNet, Support Vector Regression, K-Nearest Neighbors, Random Forest, Extra Trees, Gradient Boosting, XGBoost, and LightGBM, were trained. Model performance was assessed using coefficient of determination (R²), root mean square error, mean absolute error, and mean absolute percentage error metrics. Random Forest was identified as the most reliable model for practical deployment, exhibiting balanced generalization behavior with training R² converging from 0.63 to 0.98 and a Train-CV Gap of 0.017, confirming that it learns generalizable patterns rather than memorizing individual observations. Although Gradient Boosting achieved the highest overall performance metrics, its persistent Train R² of 1.000 indicated memorization behavior. SHAP-based interpretability analysis identified groundwater depth, shear strength parameters, and standard penetration test blow count as the primary effective parameters of the qₐₗₗ value. The proposed framework shows that ML-based approaches can significantly enhance the reliability of bearing capacity predictions along transmission line corridors.
Copyright (c) 2026 by the Authors. This is an open access article distributed under the CC BY licence. http://creativecommons.org/licenses/by/4.0
Variations in CFD simulations of wind loading on building structures
Relevant standards for wind loading provide information about wind loads on a small number of standardized building shapes. However, when designing a uniquely shaped structure, two main approaches are possible – either test the structure in a wind tunnel or perform a numerical simulation. With increasing computational power and advances in numerical simulation software, more and more scientific and applied research is being done virtually. Research on fluid flow and the resulting load on machines, industrial facilities and buildings is no exception. In these studies, the first issue is the reliability of the numerical models and, above all, the results obtained through them. Although the programs for numerical simulations have user-friendly interfaces, broad applicability, and advanced solution capabilities, it is not always clear how accurate the results obtained from them are. This article presents a numerical model of a single cylindrical body with a conical roof, subjected to subsonic wind flow. It also shows how, by varying the parameters when creating the model, as the type of finite elements, dimensions of wind tunnel, density of mesh, used RANS model to simulate the turbulence, significant differences can be accounted for in the required computational time and the calculated values of the shear force at its base. It turns out that of all the parameters listed above, the most important is the influence of the dimensions of the finite elements of the fluid domain, i.e., the density of the mesh.
Spatiotemporal trends and lagged precipitation–Soil moisture relationships across coastal and inland regions of Türkiye
Soil moisture is a key hydrometeorological variable that links precipitation and temperature to land–atmosphere interactions and strongly influences evapotranspiration, runoff generation, and drought development. This study investigates the long-term variability of surface soil wetness across Türkiye using daily datasets from seven representative cities characterized by contrasting coastal and inland climatic conditions over the period from 1 January 2005 to 1 January 2025. The analysis focuses on (i) trend assessment of precipitation and surface soil wetness, (ii) evaluation of precipitation–surface wetness (P–GWETtop) and air temperature–surface wetness (T2m–GWETtop) relationships, (iii) comparison of climatic responses between coastal and inland regions, and (iv) lagged correlation analysis to identify the response time of surface wetness to precipitation within a 0–14 day period. Monthly aggregated data were used to perform descriptive statistical analyses, correlation assessments, and linear trend evaluations. The results show that precipitation–surface wetness relationships vary considerably among the selected cities, reflecting regional differences in climatic regime, precipitation characteristics, and evaporative demand. In several inland cities, the influence of air temperature on surface wetness variability appears more pronounced, indicating the importance of evaporation-driven moisture loss under drier climatic conditions. In contrast, coastal cities generally exhibit weaker and more variable response patterns due to their more humid atmospheric conditions. Overall, the findings provide a comparative framework for understanding climate-related surface soil moisture variability across different climatic regions of Türkiye and offer useful insight for future hydrometeorological and environmental assessments.
Numerical study on structural behaviour of 3D sandwich wall under vertical and in-plane loading
Precast three-dimensional (3D) sandwich wall panels are rapidly increasing in modern construction due to their high strength-to-weight ratio, thermal efficiency, and rapid installation. However, their structural behaviour under combined vertical and in-plane loading, along with the influence of boundary stiffening, remains insufficiently studied. This study presents a nonlinear finite element investigation of 3D sandwich wall panels using ANSYS Mechanical APDL to evaluate their structural response under vertical, in-plane, and combined loading conditions. Concrete was modelled using SOLID65 elements incorporating cracking and crushing behaviour, while reinforcement and expanded polystyrene (EPS) core were included to simulate composite action. The influence of boundary stiffening and longitudinal reinforcement on load–displacement behaviour, stiffness degradation, ductility, stress distribution, and crack development were systematically analyzed. The results indicate that boundary stiffening enhances load-carrying capacity by approximately 3 to 5%, while longitudinal reinforcement improves ductility by up to 45% under in-plane loading. Stiffness degradation ranging from 22% to 24% was observed across all configurations, confirming that concrete cracking is the primary factor governing stiffness reduction. The crack patterns were found to align with principal stress distribution patterns, with dominant diagonal cracking under in-plane and combined loading conditions. The validation against experimental results and codal provisions demonstrates good agreement, with deviations generally within 10 to 15%, confirming the reliability of the numerical model. The study provides a reliable and validated numerical framework for assessing the behaviour of precast 3D sandwich wall systems and supports their design under complex loading scenarios.
Data-driven prediction of initial rotational stiffness in beam-to-upright connections of steel pallet racks
The structural performance of steel pallet rack systems is largely governed by the rotational behavior of beam-to-upright connections. Although design practice often idealizes these joints as rigid or pinned, experimental evidence shows that most exhibit a semi-rigid response. Realistic structural analysis therefore requires a reliable estimate of the initial rotational stiffness, k0, which controls the moment–rotation relationship and affects internal force distribution and frame stability. This study proposes a data-driven framework for predicting k0 directly from the geometric and mechanical properties of uprights, beams, and connectors. The model incorporates key sectional parameters and component yield strengths and is trained on a consolidated database compiled from experimentally validated literature. A comparative assessment of regression techniques shows that ensemble-based machine-learning models, particularly the Extra Trees regressor, provide the highest predictive accuracy. Feature importance and SHAP analyses indicate that connection stiffness is primarily governed by geometric parameters controlling load transfer and deformation mechanisms, while material strength plays a secondary role. The proposed approach eliminates the need for extensive experimental testing and supports realistic semi-rigid modelling and more economical pallet rack design.
On the limitations of simplified kinematic interaction models for embedded foundations
Kinematic interaction (KI) effects arising from foundation embedment alter the motion transmitted from the free field to the foundation level and can therefore influence the seismic demands imposed on structures. Although several analytical formulations and guideline-based procedures exist to represent these effects, their accuracy when used directly to modify design and response spectra has not been thoroughly validated against real ground-motion data. This study provides a systematic evaluation of two widely used KI approaches; (i) the analytical transfer functions of Elsabee and Morray (1977) and (ii) the spectral-modification procedure of FEMA-440 (2005). Using a large suite of recorded motions, free-field and foundation input motions are computed through frequency-domain modification, and corresponding acceleration response spectra are obtained to form computed spectral ratios. These computed ratios serve as a benchmark for assessing the predictive performance of the simplified KI procedures across a range of embedment-to-stiffness conditions. The results show that analytical KI factors substantially underestimate short-period spectral ordinates, whereas FEMA-440 captures overall trends more effectively but loses accuracy for larger embedment depths. The study defines practical ranges in which simplified KI procedures remain reliable and identifies conditions that require more refined soil-structure interaction modelling. The findings provide engineers with clearer guidance for incorporating KI effects in seismic analysis and design.
Copyright (c) 2026 by the Author. This is an open access article distributed under the CC BY licence. http://creativecommons.org/licenses/by/4.0
Copyright (c) 2026 Tulpar Academic Publishing http://creativecommons.org/licenses/by/4.0
Finite element method with energy minimization (FEMEM) in structural analysis: State-of-the-art
The Finite Element Method (FEM) is a powerful and widely adopted numerical technique in structural engineering for the analysis of structures and systems. Although FEM is highly effective for linear problems and can address certain classes of nonlinear problems through appropriate iterative schemes, there exist structural analysis cases that cannot be satisfactorily solved using conventional FEM formulations. Such cases include problems with non-unique equilibrium states, nonlinear or missing boundary conditions, and structures with ill-conditioned flexibility matrices, for example truss systems following the failure of one or more members. To overcome these limitations, an emerging approach—the Finite Element Method with Energy Minimization (FEMEM)—has been introduced. FEMEM is based on the same fundamental principles of structural mechanics as FEM; however, it differs in its solution strategy. Instead of solving matrix equations, FEMEM formulates the problem as the minimization of a functional, namely the total potential energy of the structure. In this paper, the fundamental concepts of FEMEM are first introduced, followed by a comparative discussion with classical FEM to highlight the advantages and limitations of the method. Subsequently, representative applications of FEMEM are presented for various structural systems, ranging from trusses and truss-like structures to planar and three-dimensional structural models. Finally, directions for future research are discussed, with emphasis on extending the applicability of FEMEM to more complex structural systems and a wider range of nonlinearities, including material, geometric, and constraint-related effects.
Optimal metaheuristic design of CFRP wrapping for enhancing the shear capacity of reinforced concrete columns
Reinforced concrete (RC) columns are prone to brittle shear failure under lateral loads like earthquakes, especially in older structures. Carbon fiber reinforced polymer (CFRP) wrapping effectively enhances shear capacity, ductility, and energy dissipation. This study optimizes CFRP jacket design to increase shear strength while minimizing material volume per meter of column. The objective function includes the number of layers (n), strip width (Wf), spacing (Sf), and thickness (tf), following ACI 440.2R-2017 and ACI 318-05 constraints on strain, shear contribution, and capacity. Three metaheuristic algorithms—JAYA, Teaching-Learning-Based Optimization (TLBO), and Flower Pollination Algorithm (FPA)—were used to solve the nonlinear problem in MATLAB with randomized populations, 100–500 iterations, and 30 independent runs. Analyses for 100–500 kN shear demands (20%–100% increases) yield valid designs. Low shear demands typically require minimal CFRP, often a single layer with moderate strip width and large spacing. Higher demands required more intensive reinforcement through increased layer count and reduced spacing, with width adjustments as needed to satisfy code constraints. FPA achieved the lowest CFRP volumes due to its Lévy-flight global search, TLBO produced the most stable results with low variability, and JAYA offered the fastest computation. Increasing iteration count and population size improved convergence in all algorithms, yielding solutions closer to the optimum. Results confirm that metaheuristics enable economical, reliable CFRP retrofitting, promoting sustainability. Future work could include multi-objective optimization for cost and constructability.
Structural performance analysis of steel piled offshore platforms under environmental loads
Steel pile foundations used in offshore structures must be able to maintain their structural integrity and safety throughout the structure's service life under environmental effects such as waves, currents, and wind. In this context, this study conducts a detailed investigation of the structural performance of a steel-piled offshore platform under environmental wave loads with different return periods. Within the scope of the analysis, the behavior of a typical platform pile group was modeled and analyzed using the Sesam Genie software under wave loads with 1-year (operating), 100-year (extreme), and 10,000-year (abnormal) return periods, considering four different soil units (ZU1, ZU2, ZU3, and ZU4). The analysis determined the maximum internal forces acting on the piles (axial forces, lateral forces, and moments) as well as the maximum displacement values at the pile tips, which ranged between 0.012 m and 0.054 m depending on the load direction and return period. Furthermore, the maximum utilization factor (UF) for each pile was calculated, varying between 0.22 and 0.49, and compared against the minimum safety factors specified in the ISO 19902 standard. It was found that in all scenarios, the maximum utilization factors of the piles remained below the respective safety limits, and the horizontal displacements at the pile tips were within acceptable engineering levels. Unlike many previous studies focusing on single piles, this study systematically evaluates group pile behavior in layered soil conditions, providing more realistic insights into offshore foundation performance. In conclusion, this study highlights the importance of concurrently evaluating soil properties and environmental loads for the structural safety of steel pile foundations and contributes to the multifaceted engineering parameters that must be considered during the design phase.
Seismic hazard and risk analyses of historical masonry structures in Kocaeli, Türkiye
Protection of masonry structures is among the most important building groups around the world. Generally constructed of heavy materials such as stone and brick, these structures are highly seismically vulnerable. In large earthquakes, masonry structures that have not received adequate engineering services are usually heavily damaged or destroyed. To prevent damage to these structures, seismic hazard and risk analyses must first be conducted correctly. This study investigates the seismic hazards and risk distributions of historical masonry structures in Kocaeli, Türkiye. As a preliminary step, information and document collection studies on historical masonry structures were conducted in Kocaeli, Türkiye. Then, a detailed building inventory data set was prepared. Following that, a probabilistic seismic hazard assessment for the investigation area was conducted considering the different attenuation relationships. In the seismic hazard analyses, the hazard maps, hazard curves and response spectra were prepared based on the inventory data set at select reference points. After that, the seismic risk analyses were conducted to determine the structure distribution based on damage levels for the structures in the data set considering different fragility curves. Accordingly, historical masonry structures in Kocaeli province close to the North Anatolian Fault (NAF) Line have high hazard curves and spectrum values, whereas structures on the Black Sea coast have low values. According to the hazard maps obtained as a result of the analyses, Kartepe, Darica, Gölcük, and Başiskele districts have a high estimated hazard distribution, while Kandira has a lower estimated hazard distribution. Further, when the risk assessment is carried out by looking at the distribution of building groups based on damage levels, it was determined that towers, aqueducts, residential structures, and dome structures are the highest priority risk structures, respectively.
Development of a sustainable geopolymer structural element with waste glass powder: Mechanical characteristics
In this study, the potential of converting waste glass powder, sourced from glass manufacturing processes in Turkey, into sustainable and environmentally friendly construction materials was explored. A novel approach was adopted by producing geopolymeric building elements using only waste glass powder, water, and varying concentrations of sodium hydroxide (2%, 4%, and 6%) in a completely cement-free system. This distinguishes the study from previous works, as it focuses solely on waste glass powder as the primary aluminosilicate source without incorporating additional binders such as fly ash or slag. The physical and mechanical properties of the produced samples were evaluated through unit weight, ultrasonic pulse velocity, compressive strength, flexural strength, and tensile strength tests. The results indicated that the mixture containing 4% sodium hydroxide provided optimal performance, demonstrating superior mechanical strength, structural integrity, and durability. Notably, the specimens produced with 4% NaOH exhibited higher durability than aerated concrete and achieved strength and density values close to conventional bricks, suggesting their potential applicability in non-load-bearing structural elements. Furthermore, this study addresses a significant gap in the literature regarding the standalone use of waste glass powder in geopolymer systems and contributes valuable data on its performance in solid form. The findings also highlight the material's potential to reduce reliance on Portland cement, thereby lowering carbon emissions and promoting the circular economy through effective waste utilization. Overall, the study offers an innovative and practical solution for sustainable construction by demonstrating the feasibility of producing high-performance geopolymer elements entirely from waste-derived materials.
Investigating Iosipescu shear properties of laser powder bed fusion 316L stainless steel via digital image correlation technique
Laser Powder Bed Fusion (LPBF) has been widely adopted for producing stainless steel 316L components with complex geometries; however, despite extensive research on its tensile performance, the shear behavior of LPBF 316L remains insufficiently characterized. Reliable shear properties are crucial for structural components operating under multiaxial loading, yet experimental data enabling accurate calibration of multiaxial yield and failure models are still scarce. In this study, the tensile and shear responses of LPBF 316L were systematically investigated through standard uniaxial tensile testing and Iosipescu shear testing, supported by full-field Digital Image Correlation (DIC). All specimens were fabricated using LPBF system, and their build orientations were precisely documented to account for anisotropy effects. Tensile tests yielded an ultimate tensile strength of approximately 650 MPa and an average elastic modulus of 197 ± 32 GPa. Iosipescu shear tests demonstrated a maximum shear stress of 621 MPa, revealing a notably close relationship between shear strength and tensile strength. The experimentally measured shear modulus was also consistent with the tensile-derived value through classical elastic relations. The combined results deepen our understanding of LPBF 316L mechanical behavior, especially the coupling between tensile and shear responses. The findings further highlight the importance of integrating shear data into design procedures, multiaxial stress assessments, and material databases for additively manufactured stainless steels. Overall, this study provides a robust experimental foundation for improving structural integrity assessments and advancing the design of LPBF 316L components subjected to complex loading.
A discrete element method for evaluating the seismic performance of concrete gravity dam-reservoir systems under main shock-aftershock events
Dams are crucial for water supply, flood prevention, and hydroelectric power generation. Often located in seismically active regions, they are vulnerable to main shock-aftershock (MS-AS) sequences, which can compromise structural integrity and hydraulic safety. Critical aspects of dam response to MS–AS events remain unclear, particularly the required rest time between successive events and threshold AS-to-MS intensity measure ratios that could serve as predictors of additional damage. This study addresses these gaps by analyzing concrete gravity dam–reservoir systems of three heights (50 m, 100 m, and 150 m) using the developed discrete element–based approach coupled with displacement/pressure-based mixed finite elements for the reservoir. Empirical rest time equations were derived from 124 as-recorded ground motions, while seismic performance under varying intensity levels was evaluated using 14 as-recorded MS–AS sequences. Damage was quantified using discrete indices of base crack length, maximum base crack width, and maximum total upstream crack width. Results indicate that AS primarily propagate existing cracks at lower intensities, whereas higher intensities generate new cracks along the upstream face, increasing crack widths by 25–30% on average. The 50 m high dam remained within the mild damage category, while taller dams occasionally reached moderate levels, posing potential seepage risks. Threshold AS-to-MS ratios for four different intensity measures were identified. These findings provide mechanistic insight into crack propagation under MS-AS events, providing practical guidance for post-earthquake dam safety assessment, inspection prioritization, and incorporating sequential seismic effects into design and emergency planning.
Copyright (c) 2025 by the Authors. This is an open access article distributed under the CC BY licence. http://creativecommons.org/licenses/by/4.0
Mechanical characterization of FDM-printed PLA: Role of infill geometry and build direction
This study examines the mechanical behavior of polylactic acid (PLA) components produced via Fused Deposition Modeling (FDM), focusing on the effects of infill geometry and build orientation on tensile strength and deformation. Three infill patterns‒Cubic Subdivision, Gyroid, and Tri-Hexagon‒were combined with three build orientations (0°, 45°, and 90°) using an L9 Taguchi orthogonal array to systematically evaluate their influence and identify optimal configurations. ASTM D638 Type IV tensile specimens were fabricated and tested to assess performance. The results revealed that the Gyroid pattern at a 90° build orientation achieved the highest tensile strength (987.3 N), while the 45° build orientation exhibited the greatest ductility (3.39 mm), reflecting the anisotropic mechanical behavior inherent to FDM. The Tri-Hexagon pattern displayed brittle fracture characteristics, whereas the Cubic Subdivision offered intermediate performance. Analysis of variance (ANOVA) identified infill pattern as the most significant factor, accounting for 86.52% of the variation in mechanical properties, while build orientation contributed 6.29%. These findings emphasize that infill strategy plays a far more decisive role than build orientation in determining mechanical performance. Overall, the study provides practical insights into optimizing FDM-printed components by selecting appropriate infill patterns and build orientations to meet application-specific requirements, particularly where strength or energy absorption is critical. The results can serve as a reference for designers and engineers aiming to enhance the structural efficiency and reliability of 3D-printed PLA parts.
Effect of elevated temperatures on mechanical properties of hydraulic lime-based mortar in historical structures
Historic masonry structures are subjected to various negative effects from the time they are built. As a result, these structures suffer damage, leading to restoration and reinforcement efforts. Hydraulic lime-based mortars (HLMs), which are compatible with the nature of historic structures, are used in restoration and reinforcement. This study investigated the fire resistance of hydraulic lime-based mortars. Within the scope of this study, HLMs were prepared in accordance with restoration standards, and prism specimens were prepared with HLMs. These specimens were exposed to high temperatures ranging from 200 °C to 700 °C, and bending and compression tests were conducted on the specimens exposed to temperature. During the elevated temperature tests (ETTs), a total of 27 specimens were prepared, including three test specimens, one temperature monitoring specimen for each temperature, and three reference specimens. While the reference specimens were tested at room temperature, the other specimens were kept until they reached room temperature after the ETTs were completed and then tested under the same conditions as the reference specimens. No tests were performed on the temperature monitoring specimens, and these specimens were only used to monitor the temperatures inside the specimens with thermocouples placed inside. As a result of the experimental studies and evaluations, it was determined that the HLMs began to lose their mechanical properties with increasing temperature, but even after 700 °C, they still exhibited mechanical properties observed in low-grade mortars.
Enhancing the mechanical performance of perforated steel plates through fiber-reinforced composite reinforcement: A finite element analysis study
Reinforced concrete and steel plates are widely used in civil engineering and are important components of many structural systems and ground reinforcement projects. These plates effectively carry different loads, enhance ground support, and improve the durability of structures. Moreover, the proper selection and use of these materials during the design and planning stages of construction projects have a direct impact on cost and time efficiency. In addition to their structural contributions, the effective use of reinforced concrete and steel plates is critical for the safety and success of construction projects. In order to transfer loads to the frame system, reinforced concrete plates serve as horizontal load-carrying components. Load-bearing capacity, stiffness, fire resistance, and sound insulation are important properties of reinforced concrete plates. Perforated plates are widely used in structural applications but suffer from stress concentration around openings, reducing their mechanical performance. This study investigates the reinforcement of perforated steel plates using fiber-reinforced polymer (FRP) composites around holes to enhance structural integrity. The research employs finite element analysis (FEA) to assess the effects of different reinforcement widths under varying loads. A detailed comparison of stress and deformation distributions before and after reinforcement is presented. The findings indicate that FRP reinforcement significantly reduces stress concentration and improves the load-bearing capacity of perforated plates, providing practical insights for industrial and construction applications.
Performance investigation of a mixed slab building with beam and ribbed slabs
Over time deterioration in material properties, unauthorized modifications, or construction defects can negatively affect the seismic behavior of structural members. Therefore, the in-situ identification and performance analysis of reinforced concrete elements, carried out to ensure the safety of the existing building stock, have become a fundamental part of examining structural characteristics and developing disaster risk reduction strategies. In this study, the structural performance analysis of an existing reinforced concrete building with a mixed slab system was conducted by using the STA4CAD V13.1 software. For this purpose, nonlinear pushover analysis was performed for each seismic direction. As the existing reinforced concrete building did not satisfy the requirements for the single-mode method prescribed in TBDY (2018), a multi-mode pushover analysis was conducted for the structure. Based on the results of nonlinear multi-mode pushover analysis, the damage states of the structural members were determined, and the performance level of the structure was evaluated. The targeted performance level of controlled damage, as defined in the Turkish Building Earthquake Code-2018 TBEC (2018), could not be achieved for the analyzed residential-type reinforced concrete building. However, the collapse prevention performance level was determined due to the damage occurrence in the structural elements.
Seismic performance assessment of timber-framed (hımış) structures with different infill materials
This study investigates the seismic performance of traditional timber-framed (hımış) structures incorporating different types of infill materials through advanced nonlinear finite element modeling. Timber-infilled walls represent a widely used hybrid construction typology in seismic regions, where the interaction between the ductile timber frame and brittle infill materials critically influences structural behavior. Four configurations are analyzed: (1) Timber frame with adobe (mudbrick) infill; (2) Timber frame with fired clay brick infill; (3) Timber frame with natural rubble stone infill; and (4) Bare timber frame. A series of three-dimensional pushover analyses are conducted using ANSYS Workbench, where all materials are modeled using Multilinear Isotropic Hardening plasticity, including contact-based interface definitions and geometric nonlinearity. The mechanical behavior of each wall system is interpreted based on key seismic performance indicators, including initial lateral stiffness, base shear capacity, effective displacement ductility, and energy dissipation. Results show that while infill materials significantly increase the lateral strength and stiffness of the wall systems, they also introduce varying degrees of brittleness and reduced ductility. These findings emphasize the critical role of infill type in the seismic response of timber-framed walls and highlight the importance of understanding frame–infill interaction for the assessment and retrofitting of traditional building stock in earthquake-prone regions.
Copyright (c) 2025 by the Author. This is an open access article distributed under the CC BY licence. http://creativecommons.org/licenses/by/4.0
Nonlinear in-plane response of 3D-printed concrete walls with varied infill patterns: Experimental mix design and numerical structural assessment
This study investigates the nonlinear in-plane structural behavior of 3D-printed concrete wall elements with two representative internal infill patterns ‒ lattice (L) and triangular (T) ‒ using finite element modeling informed by experimentally derived material properties. A printable concrete mixture was specifically developed using CEM I 42.5 R Portland cement, silica sand, and hydroxypropyl methylcellulose (HPMC) as a viscosity-modifying agent. Conventional cast specimens (40×40×160 mm³) achieved a 28-day flexural strength of 8.7 MPa and a compressive strength of approximately 63 MPa. Nonlinear behavior of wall panels with both infill types was investigated using numerical methods with advanced constitutive laws. These models account for the distinct compressive–tensile response of concrete and damage evolution under monotonic lateral loading, allowing assessment of the influence of geometry on load-bearing capacity and failure mechanisms. The results reveal that both infill patterns exhibit nonlinear load–displacement responses with an initial elastic regime, an early localized cracking peak, followed by a notable recovery in load-bearing capacity, and subsequently a global peak load prior to progressive post-peak softening. While the overall performance of both infill types was comparable, the T pattern exhibited a marginally higher peak load (1.7–2.7%) and improved ductility relative to the L form. These distinctions are attributed to the T-pattern’s more efficient diagonal force transfer and the development of a single continuous diagonal shear band, as opposed to the L-pattern’s multiple discontinuous cracks and broader damage zones.
Impact of screw arm angle, material property, and applied force on the behavior of maxillary expander
A unilateral or bilateral posterior crossbite is a common and severe malocclusion characterized by maxillary transversal deficiency. Various expansion appliances are employed to correct this condition. The objective of this study was to evaluate the forces transmitted to the teeth and the deformation of the expander appliance resulting from modifications to the screw arms of a slow maxillary expander with different angles, using finite element analysis. All models were created in SolidWorks and analyzed using ANSYS Workbench. The analysis revealed that the models with different angular configurations of the expander screw arms (0°, 15°, and 30°) exhibited very similar reaction forces on the teeth. However, significant differences in deformation values were observed among the models. The most effective parameter is the force applied to the expander with a rate of 46%, followed by the arm angle with a rate of 44%, while the effect of material type is 10%. The most significant conclusion that can be drawn from these findings is that the arm angle is as important as the force applied to the expander. In situations where the force that can be applied is limited by various factors, it can be demonstrated that altering the arm angle can lead to the achievement of the desired outcome.
Long-term durability of red mud-modified cement mortars: Effects of high temperature and freeze-thaw cycles
The use of industrial by-products such as red mud in cementitious materials addresses sustainability by reducing environmental impact and improving performance. As a hazardous waste from aluminium production, red mud offers a promising solution for waste management and improves the mechanical and durability properties of mortar when used as a partial cement replacement. This study investigates the long-term mechanical and durability properties of cement mortars modified with red mud, a by-product of alumina production. Red mud was incorporated at substitution percentages of 5%, 10%, 15%, 20%, 25%, 30% and 35% by weight of cement. The mortars were subjected to harsh environmental conditions such as high temperatures (200°C to 600°C), freeze-thaw cycles (50 and 100 cycles), and normal curing conditions at 365 days of age. The study showed that partial replacement of cement with red mud significantly affected the mechanical and durability properties of the mortars. The optimum red mud replacement level of 10% showed that microstructural compactness and hardness were improved by increasing the ultrasonic pulse velocity, dynamic modulus of elasticity and flexural strength. Durability tests showed improved thermal resistance at moderate levels of red mud content, while higher levels adversely affected freeze-thaw performance. These findings confirm that a 10% red mud substitution offers the best balance between strength, durability, and sustainability.
Influence of damage state threshold variability on the seismic vulnerability analysis of masonry aqueducts
The accuracy of fragility curves, a key outcome of seismic vulnerability studies, directly influences rational seismic risk assessments. In this study, analytical-based fragility curves for a masonry aqueduct were derived using tested earthquake-based Intensity Measure (IM) parameters and various threshold limit values for specific damage states, as commonly used in the literature. The Maximum Intensity Damage Ratio (MIDR) thresholds for specific damage states proposed by FEMA 356, GERMHS, and ASCE 41-13 standards were considered. Additionally, damage state thresholds were determined through a capacity curve obtained via nonlinear static analysis and empirical relationships found in the literature. The effect of damage thresholds on the Probability of Exceedance (PoE) values for a specific damage state was analyzed using the reference MIDR values determined in this study. Based on earthquake ground motion records, PoE values corresponding to different damage states were evaluated separately for each IM parameter. The results demonstrate that the damage threshold value significantly impacts the developed fragility curves. Therefore, when developing fragility curves for the seismic risk assessment of masonry structures, it is crucial to analyze and determine the appropriate threshold levels for each structure individually, rather than directly applying the threshold values used in the literature.
Impact of composite columns on soft and weak storey irregularities in buildings without ground floor infill walls
In buildings without infill walls on the ground floor, structural irregularities, such as soft and weak storey irregularities can significantly reduce their resilience to earthquakes. These irregularities arise from insufficient lateral stiffness and strength in the ground floor structure, leading to instability during seismic events. This study investigated the seismic performance of frame structures, focusing on two key factors: the lateral rigidity provided by infill walls and the potential benefits of replacing conventional columns with composite columns on the ground floor. The analysis was conducted in accordance with the Turkish Building Earthquake Code 2018 (TBEC-2018), which provides specific guidelines for designing structures to withstand seismic forces. The findings revealed that including the lateral rigidity of infill walls in the analysis increased the cracked cross-section’s moment of inertia by 5%. While this addition enhanced the building’s lateral load resistance, it also increased the rigidity irregularity coefficient by 33%, indicating a potential redistribution of seismic forces that could affect the overall stability. On the other hand, introducing composite columns on the ground floor helped reduce the rigidity irregularity coefficient by 20%, providing a more uniform response to lateral loads. However, this improvement came at the cost of a 29% increase in the strength irregularity coefficient, highlighting the challenges in balancing stiffness and strength irregularities. These findings emphasize the importance of carefully evaluating structural modifications to optimize seismic performance. While composite columns are effective in mitigating rigidity irregularities, their impact on strength irregularities must be managed to avoid compromising overall safety.
Improving bond performance of 3D-printable earth-based mortar reinforced with jute fibers
3D printing technology has transformed the construction industry by enabling rapid and cost-effective production of complex geometries. However, it faces significant challenges, including sustainability concerns due to cement's environmental impact and reinforcement issues arising from the incompatibility of traditional steel. These challenges necessitate the development of innovative material solutions. This study aims to enhance the bond strength between sustainable earth-based mortar and jute fibers used as reinforcement in 3D printed structures by exploring the effects of different treatments and compositions. Bond strength was evaluated by considering the effect of different treatments on the resistance of the fiber to being pulled out of the mortar. Pull-out tests were conducted on specimens with varying compositions and treatments. Results demonstrated substantial improvement in bond performance; specifically, the reference sand-free earth-clay mortar exhibited the lowest interfacial shear strength of 0.30 MPa. The most remarkable enhancement was observed in specimen which jute fibers pre-treated by immersion in mud slurry, which showed a 147% increase, reaching an interfacial shear strength of 0.74 MPa. Combining sand addition and fiber pre-treatment, however, did not yield additional benefits. These results indicate that simple, cost-effective local treatments can notably enhance fiber-matrix bond strength in 3D-printed earth-based structures without necessitating additional equipment or significant expense.
Influence of connector forces on the expansion configuration of a hexagonal modular floating structure
The preliminary design of a hexagonal modular floating structure (HMFS) system includes two configurations: U-shaped and V-shaped, which link seven hexagonal modules that create a network of connectors. The connector force is a crucial consideration in the layout of the connector network, as it must sustain the forces generated by wave motion due to its influence on the stability and safety of the modular floating structure. This paper presents the development of the HMFS connector network and the estimation of the connector horizontal force influence by two types of configurations. The design concepts of these configurations for HMFS configurations are proposed where analysis was implemented for regular wave in various directions of 0°, 30°, 45°, 60°, 85°, and 90°. The impact of these various wave directions and the HMFS configurations on the connector force is analysed accordingly. According to this research finding, the connector force in U-shaped configuration is higher than the load in V-shaped of HMFS configuration. The connector force of the V-shaped configuration is arranged in hexagonal vertices (VV-shaped) facing wave direction receive a higher connector force than hexagonal parallel sides (VP-shaped) facing wave directions. The determination of horizontal connector load of hexagonal modules with varying configurations enabled the designer to estimate the horizontal connector load for various conceptual designs of hexagonal shapes, such as dock ships, yacht terminal and floating cities.
Examining the effects of different seismic base isolators on the seismic behavior of a real-size steel truss structure
In this study, the seismic behavior of a real-size steel truss structure is examined for elastomeric isolator, double friction pendulum isolator, and fixed support conditions. Hence, the main aim of the study is to examine which type of support is safer for seismic response of a real-size steel truss structure, considering the structural reactions under earthquake and other acting load effects. To do this, the structural models generated with three different support conditions are examined in detail in terms of earthquake characteristic according to conducted structural seismic analyzes. The real-size steel truss structures are modeled in SAP2000 structural analysis program and are designed in accordance with the Turkish Building Earthquake Code-2018 specifications. The snow and wind loads acting on the truss structures are calculated in the direction of TS EN 1991-1-3 and TS EN 1991-1-4 specifications, respectively. The earthquake forces are implemented to the truss structure through mode superposition method. Finally, the truss structure is comparatively examined in terms of the structural weight, base shear force, natural vibration period, and relative drift. As regards to the obtained results, it has been observed that the seismic responses of the steel truss structure are remarkable better when the seismic base isolator is implemented into the structure.
Utilization of expired cement and aged roof tile powder in the production of sustainable geopolymer: Mechanical and physical properties
This study deals with the production of geopolymer mortar in order to promote the recycling of waste materials as sustainable building materials. The use of waste materials such as expired cement and aged roof tiles powders in cementitious systems is of great importance in terms of increasing environmental sustainability and reducing industrial waste. Recycling these materials and using them as alternative binders contributes to more environmentally friendly and economical concrete and mortar production by reducing natural resource consumption. Expired cement and aged roof tile powder were used as binder materials and mortar specimens were produced by activating these materials with alkalis such as NaOH and Na2SiO3 at different ratios. Within the scope of the experimental studies, mechanical and physical properties such as unit weight, ultrasonic pulse velocity, compressive strength and bending strength were investigated in detail. The results showed that the expired cement specimens performed better especially in unit weight, ultrasonic pulse velocity and compressive strength tests, while the roof tile powder had superior properties in terms of bending strength. It was also found that the specimens activated with sodium hydroxide (NaOH) exhibited generally higher strength and performance than those activated with sodium silicate (Na2SiO3). These findings prove that waste materials such as both expired cement and roof tile powder can be valuable alternatives in the construction industry in terms of sustainability and waste management and reveal the potential of using these materials in geopolymer mortar production.
Investigation of the effects of re-curing on mechanical properties of basalt-polypropylene hybrid fiber concretes after exposure to high temperature
Fiber reinforced concretes have attracted significant attention in recent decades due to their superior flexural and toughness properties compared to traditional concrete in civil engineering structures. In addition, cementitious materials can undergo significant mechanical deterioration under high temperature. Therefore, the investigation of the properties of FRC for fire-resistant design has become an important research topic in recent years. On the other hand, there is very little research on the repair of FRCs damaged by fire. In this study, high temperature resistance of mixtures prepared using basalt and polypropylene fibers was investigated. In addition, the ability of FRCs exposed to high temperatures to regain their properties by applying water re-curing process was investigated. In this context, ultrasonic pulse velocity (UPV), compressive and flexural strength of FRC series after different stages were investigated. In the use of water curing single basalt fiber, 18.56% and 13.82% increase in relative compressive strength was obtained after 600 °C and 800 °C, respectively. These increase rates were determined as 22.25% and 22.81% in relative flexural strength. Recovery was more significant in the hybrid mixture formed with 0.2% polypropylene fiber. 29.22% and 15.93% recovery was reported in relative compressive strength after 600 °C and 800 °C, respectively. It was determined that re-curing significantly increased the mechanical properties of FRC mixtures.
Predicting shear strength in reinforced concrete deep beams through finite element modeling of diverse concrete materials
This study investigates the prediction of the strength of reinforced concrete deep beams, critical components in urban infrastructure, by evaluating their load-carrying capacities through finite element modeling and nonlinear inelastic analyses using LS-DYNA software. Four widely used concrete material models were examined: Mat084/085, Mat159, Mat072R3, and Mat016. Analyses were conducted on two single-span and four double-span beams with varying reinforcement configurations and an aspect ratio of 1.0, based on well-documented experimental setups. Comparative analyses of force-displacement behavior and stress distributions revealed significant differences in shear strength predictions across the models, with Mat159 providing the most accurate results. These findings establish a reliable and cost-effective approach for predicting the capacities of deep beams, reducing reliance on extensive experimental testing. The study contributes valuable insights for improving strength predictions in critical infrastructure applications such as bridges and foundations.
Investigating the effects of glass fiber in enhancing concrete pavement performance
Flexible pavements are considered more sustainable than concrete pavements primarily due to the higher long-term maintenance and rehabilitation costs associated with concrete pavements. Concrete pavements possess a higher modulus of elasticity, which allows them to distribute vehicle loads over a larger area, thereby enhancing the strength of the pavement. However, despite this advantage, their flexural strength is relatively low. As a result, there has been a growing focus on research to improve the flexural strength of concrete pavements to increase their overall performance and sustainability. This study aimed to reveal the effects of enhanced mechanical properties of concrete reinforced with glass fiber on concrete pavements, specifically under heavy vehicle loading as in real-world conditions. The impact of glass fiber on the thickness of both the concrete and base layers, as well as the quality of the base layer material and transverse joint spacing, was assessed. For this purpose, 3D finite element models were developed using ANSYS software, considering concrete thicknesses of 100, 150, and 200 mm, glass fiber ratios of 0%, 0.5%, and 1%, base layer elastic moduli of 100, 200, and 300 MPa, and transverse joint spacings of 300, 450, and 600 mm. It was determined that the concrete thickness and the base layer modulus of elasticity were the most influential factors in minimizing flexural stress, total deformation, and equivalent total strain. The glass fiber addition had a more notable impact on maximum principal stress, especially at the 1% ratio, but had a minimal effect on total deformation and strain. Transverse joint spacing had the least effect, although shorter spacings are still recommended to reduce the risk of transverse cracking in stiffer base layers.
The mechanical properties of cement mortar reinforced with silica fume subjected to sulfate and chloride environment
This study investigates the effect of incorporating micro-sized silica fume on the mechanical properties and durability of cement mortar when exposed to sulfate and chloride environments. Mortar samples were prepared by replacing cement with micro-sized silica fume in varying proportions of 5%, 10%, 15%, 20%, 25%, 30%, and 35% by weight. The specimens were cured in water and chemically aggressive conditions, including 5% and 10% sodium sulfate solutions, as well as mixtures of 5% and 10% sodium chloride solutions, to simulate real-world exposure to such environments. Experimental results revealed that the addition of silica fume significantly enhanced the mortar's resistance to chemical deterioration caused by sulfates and chlorides. This improvement is attributed to the pozzolanic reaction of silica fume, which contributed to denser microstructures, reduced porosity, and a stronger bond within the matrix. Among the tested proportions, the optimal replacement ratios for achieving the best balance between mechanical strength and durability were identified up to 20%. These findings highlight the efficiency of silica fume as a supplementary cementitious material in mitigating the adverse effects of aggressive chemical agents. Such modifications can be particularly valuable in improving the service life of concrete structures exposed to harsh environmental conditions, enhancing sustainability and cost-effectiveness in construction practices.
Copyright (c) 2025 Tulpar Academic Publishing http://creativecommons.org/licenses/by/4.0
Combined effect of rice husk ash and animal bone powder on strength and permeability of concrete
Concrete is a key component of construction, and its demand is rising quickly along with infrastructural development. Although cement and aggregates are still essential components for making concrete, the production of cement greatly increases CO2 emissions, necessitating the use of substitute materials to lessen the impact on the environment. As partial cement substitutes, rice husk ash (RHA) and animal bone powder (ABP) are viable alternatives. Animal bones, which are especially common in areas with high cattle populations, and rice husks, a byproduct of paddy production, are frequently discarded despite having useful qualities that can be used to improve concrete. With an emphasis on how they affect the material's permeability and strength, this thesis investigates the addition of RHA and ABP to concrete. Different RHA and ABP replacement amounts are examined through controlled experimentation to ascertain how they affect the properties of concrete following a predetermined curing period. The goal of this research is to determine the ideal combination that strikes a balance between environmental advantages and performance. In addition to improving the qualities of concrete, using RHA and ABP helps with waste management and pollution control. This strategy may help with sustainable building methods, reduce CO2 emissions, and encourage efficient use of resources by lowering dependency on conventional cement.
Impact of iron powder and blast furnace slag on the mechanical properties of polymer concrete: An experimental and hyperparameter-tuned ANN-based study
Polymer-based materials have become increasingly used in concrete production and various engineering applications due to their versatile properties. In particular, polymer concrete (PC) has become a preferred reinforcement material in the construction industry. Various studies have been carried out to evaluate the performance of PC and to improve its mechanical properties by adding different admixtures. This study investigates the effects of fine materials such as iron powder (IP) and blast furnace slag (BFS) on the mechanical performance of PC. Within the scope of the study, samples with 5% and 10% IP, 5% and 10% BFS, 2.5% IP + 2.5% BFS and 5% IP + 5% BFS were prepared. These specimens were cured in the same laboratory environment and subjected to mechanical tests at the end of the 7th day. The results of the mechanical tests were compared to reveal the effect of fine materials on the performance of the PC. The potential of an artificial neural network (ANN) model is investigated to replicate real-world outcomes. The findings provide valuable insights into the potential of iron powder and blast furnace slag as admixtures to improve the mechanical properties of PC.
Copyright (c) 2024 by the Authors. This is an open access article distributed under the CC BY licence. http://creativecommons.org/licenses/by/4.0
Mechanical properties of lightweight photocatalytic marbelite
This study investigated the mechanical performance of lightweight photocatalytic marbelite (LPM). In the production of LPM, titanium dioxide (TiO2) and various fiber additives were used to impart self-cleaning properties to the LPM with photocatalytic effect. In the study, fibers were added to the LPM mix at different ratios (0%, 0.5%, 1%) and unit weight, ultrasound transmission rate, bending, splitting tensile and compressive strength tests were carried out on these specimens. The mixture was prepared with perlite and polyester resin and enriched with TiO2 and fiber additives. Perlite was used as an aggregate in the LPM and lightweighting properties were added to the specimens. The experimental results show that increasing the fiber content significantly improves the mechanical strength of the LPM. The improvement in bending strength reached 60%, while in compressive strength it reached 25% and in splitting tensile strength it reached 35%. With the addition of TiO2, the bending strength of LPM increased by 15%, while the compressive strength increased by 12% and the splitting tensile strength increased by 7%. These ratios were higher with increasing fiber content. These results suggest that LPM, which provide environmental benefits with their photocatalytic properties and improved mechanical performance, can be more effectively used in industrial applications.
Freeze-thaw and drop-weight impact resistance of fiber-reinforced pervious concretes produced using recycled pervious concrete aggregate
Pervious concrete can rapidly drain stormwater from the top layer to the sublayer. However, the porous structure of this concrete also results in low mechanical properties, which prevent the widespread use of pervious concrete around the world. This study investigated the freeze-thaw and drop-weight resistances of pervious concrete produced with recycled pervious concrete aggregate. Two different aggregate types (limestone and recycled) and two different aggregate size fractions (15/25 mm and 5/15 mm) were used to examine the effect of aggregate type and gradation. Additionally, for improving mechanical and durability properties, polypropylene fibers were used at three different dosages by the volume of mixtures (0.1%, 0.2%, and 0.3%). Within the scope of the study, compressive, splitting-tensile, and flexural strengths, effective porosity, freeze-thaw, abrasion, and impact resistance of pervious concrete were determined. The results showed that concrete produced with recycled aggregate had some advantages in terms of porosity; however, its mechanical properties, freeze-thaw, and impact resistance were lower than those of pervious concretes produced with limestone aggregate. Additionally, fiber addition decreased the compressive strength and effective porosity of pervious concrete. However, up to a certain point (0.2%), fiber addition improved abrasion, freeze-thaw, and impact resistance, as well as splitting tensile and flexural behavior of pervious concrete.
Copyright (c) 2024 by the Author. This is an open access article distributed under the CC BY licence. http://creativecommons.org/licenses/by/4.0
Structural behavior of ferrocement beams with circular openings
The construction sector is a major contributor to resource consumption and waste generation. Therefore, developing more efficient and sustainable materials and infrastructure is a top priority for achieving the Sustainable Development Goals. This research aims to contribute to this effort by studying the behavior of ferrocement beams with circular openings, with the goal of understanding their behavior under various loads and determining their potential use in designing more resilient and sustainable structures. Fifteen beams with different reinforcement mesh types were subjected to experimental testing under four-point loading, one group serves as the control with conventional reinforcement, while others vary in mesh type and opening configurations. All beams maintained approximately close reinforcement ratios, employing either two layers of welded galvanized steel mesh or a single layer of expanded steel mesh. Using numerical models, all fifteen beams were analyzed with the structural analysis program ANSYS V. 15 to study their non-linear shear behaviors and compare them with experimental data, focusing on load-deflection curves and failure modes. Results show that beams reinforced with expanded steel mesh achieved higher ultimate loads than those with welded mesh, with increases up to 81.59% depending on the opening configuration. However, beams with openings generally exhibited reduced ultimate loads, averaging 26.85% for welded mesh and 32.13% for expanded mesh, compared to beams without openings. Vertical openings, particularly with multiple openings, resulted in significant load decreases.
Copyright (c) 2024 Tulpar Academic Publishing http://creativecommons.org/licenses/by/4.0
Optimization of mechanical properties in lime-based composites using the Taguchi method
Global warming is widely recognized as one of the most pressing issues of our time. One of the primary contributors to this phenomenon is the emission of CO2, which significantly exacerbates global warming. Today, the production and industry of cement stand out as leading sources of carbon emissions. Consequently, the scientific community is actively researching solutions to reduce cement usage. Some of these efforts focus on alternative binders such as silica fumes and lime. In this study, the goal is to enhance silica fume and lime binder composites, optimizing them for both refractory and insulating properties using the Taguchi optimization method. The results indicate significant improvements in compressive and flexural strengths, which were further validated through testing. The highest compressive strength achieved was 11.97 MPa, while the maximum flexural strength reached 0.34 MPa. This research underscores the potential of alternative binders in mitigating the environmental impact of cement production while enhancing material performance in various applications.
Influence of the distance between vertical cylinders positioned in a row on the wind load on them
The silos and vertical cylindrical tanks of small volumes are often built in batteries, at short distances between them. As a result of their close location, the wind load on them increases. In the European standard EN 1991-1-4:2005+A1:2010 exists a methodology for determining this increase, which is dependent on the ratio a/d, where a is the distance between the facilities and d is their diameters. Unfortunately, this methodology is applicable for ratios a/d > 2.5. In cases where the values are smaller, the standard transfers to the national annexes. In the available to the author annexes, including the Bulgarian one, there is nothing on the subject. Moreover, the necessary information could not be found in the public scientific literature. Only in the Australian/New Zealand standard AS/NZS 1170.2:2011 are written some simple rules for closely spaced vessels. To fill this gap, multiple models of closely spaced cylindrical bodies has been created by the author. A computer fluid simulation (CFD) program is used for this purpose. In the present study, the bodies are arranged in one row and the wind blows them perpendicularly. Through these computer models is determined how the wind load changes due to their proximity. In contrast to what is stated in EN 1991-1-4:2005+A1:2010, the dependence is not linear, and the influence of the close arrangement of the bodies decays much faster. On the other hand, this influence should be considered at much greater distances between bodies than stated in AS/NZS 1170.2:2011.
Prediction of optimum design of welded beam design via machine learning
Design optimization is an important engineering design topic. One of the important issues in structural design is to minimize the cost. This study based on an engineering problem of Welded Beam Design aims to minimize the cost of the beam with machine learning (ML) models depending on the constraints on applied load, shear stress, bending stress and end deflection. The data set to be used in this context was created using a metaheuristic optimization algorithm. This hybrid algorithm is based on the classical Jaya algorithm by adding the student phase of Teaching Learning Based Optimization. The dataset obtained as a result of the optimization is a dataset with 1189 rows. Six different algorithms were used for prediction analyses. These are Linear Regression, Decision Tree, Elastic Net, K-Nearest Neighbour, Random Forest, and XGBoost algorithm. In the data set, load, length, and displacement are input; the design variables such as b, h, l, t and minimum cost are output. Since there is more than one output in the dataset, Multioutput Regression is applied. The performance of regression models was assessed using the Coefficient of Determination (R²), Mean Absolute Error (MAE), and Root Mean Square Error (RMSE). According to the results obtained, the Decision Tree Model showed the best performance among the other models (R2=1, MAE=6.13e-11, RMSE=9.47e-10).
The effect of build direction on component strength in SLA-based additive manufacturing
Nowadays additive manufacturing is frequently used, especially in industrial applications such as aerospace and biomedical. In the additive manufacturing method, thanks to the layered manufacturing technique, it enables the production of components with all kinds of complex geometries and accelerates the production process. As it is known, the orientation of the layers in the additive manufacturing technique affects the mechanical properties of the components. Among the parameters affecting strength, layer thickness, production direction and layer geometry are of great importance. In this study, the effect of layer orientation on component strength in SLA-based additive manufacturing was experimentally investigated. Consequently, standard tensile samples were produced at four different production orientation using the UV Stereolithography method. Tests of the tensile samples were carried out at constant tensile speed and tensile curves were obtained. According to the results, it was determined that the layer joints parallel to the shear plane exhibited the lowest strength. Therefore, samples produced at the parallel to the shear plane fractures at lower loads and showed low strength. Considering the experimental results obtained, it has been determined that the structure orientation affects the mechanical properties of the component by ~20%.
Effect of different trimline extension of clear aligners in combination with Class II elastics on the mandibular dentition: a finite element analysis
Objective of this study is to evaluate the effect of different trimline extension of aligners and the effect of elastics applied through the slit cutouts and buttons on the mandibular dentition using Class II intermaxillary elastics combined with clear aligner treatment. Three-dimensional (3D) finite element models that simulate the effects of Class II elastics on the mandibular arch in four different scenarios were studied, named, straight and high trimline aligner (HTLA) model with elastic applied through buttons (Model 1), straight and low trimline aligner (LTLA) model with elastic applied through buttons (Model 2), HTLA model with elastic applied through slit cutout (Model 3), LTLA model with elastic applied through slit cutout (Model 4). 3D displacements of the teeth, von Mises stress (VMS) in the periodontal ligament (PDL) were calculated. In all models, the crown of the mandibular anterior teeth moved labially, the root moved lingually, and the mandibular first molars moved mesially. Among all models, labialization of incisors and mesialization of molars was highest in Model 2 and lowest in Model 3. In clear aligner treatment combined with Class II elastics, HTLA was more effective in controlling mandibular incisor proclination and mesial tipping of mandibular molars. The slit cutout models were more effective in controlling mesial tipping of mandibular molars.
From ruins to reconstruction: Harnessing text-to-image AI for restoring historical architectures
The preservation of cultural heritage has become increasingly important in the face of conflicts and natural disasters that threaten historical sites worldwide. This study explores the application of artificial intelligence (AI), specifically text-to-image generation technologies, in reconstructing heritage sites damaged by these adversities. Utilising detailed textual descriptions and historical records, this study employed AI to produce accurate visual representations of damaged heritage sites, bridging the gap between traditional documentation and modern digital reconstruction methods. This approach not only enhances the architectural design process across various disciplines but also initiates a paradigm shift towards more dynamic, intuitive, and efficient heritage conservation practices. The methodology integrates data collection, iterative AI-generated image production, expert review, and comparative analysis against historical data to evaluate reconstruction accuracy and authenticity. By integrating AI with traditional preservation practices, this study advocates a balanced approach to conserving cultural legacies, ensuring their preservation and revitalisation for future generations. Preliminary findings suggest that AI-generated imagery holds significant promise for enhancing digital heritage preservation by offering novel approaches for visualising and understanding historical sites. These findings also highlight the need to address ethical, technical, and collaborative challenges to enhance the precision, reliability, and applicability of AI technologies in the field of cultural heritage. This study contributes to digital humanities and archaeological conservation, demonstrating AI's potential to support and complement traditional heritage preservation methods and suggests a pathway for substantial methodological evolution in the field.