Acoustic methods are widely used for non-destructive concrete testing. They detect internal flaws while preserving structural integrity. Nevertheless, current detection methods primarily depend on manual judgment, which is laborious, time-consuming, expensive, and susceptible to misjudgment and oversight. This study established an efficient and accurate detection system for identifying defects in concrete structures. Experimental data is first collected through ultrasonic tomography scans. To compensate for limited test data, numerical simulations generate extensive datasets with varied defect locations, enabling development and optimization of a 1D-CNN model using the dataset. This network structure is then applied to the experimental data for detecting defects in concrete structures. Values of 0.9708 and 0.9440 are achieved by the models which validates its effectiveness in practical applications and generalization ability. This method successfully combines convolutional neural networks with ultrasonic techniques. It enables the automatic detection of internal defects and provides a new effective approach for nondestructive testing of concrete structures.
The rapid development of high-speed railways has promoted the widespread use of dual-use long-span cable-stayed bridges for crossing large rivers and valleys. However, the complex loading conditions associated with these structures introduce significant uncertainties in track geometry evolution, posing challenges for reliability assessment and potentially affecting the safety and performance of railway operations. To address these challenges, this study establishes an integrated finite element model of a dual-use long-span cable-stayed bridge with ballastless track. The model is used to simulate the evolution of track geometry under different loading conditions, showing that long-wave vertical track irregularities exhibit multiple peaks, with the maximum deviations generally occurring near the bridge towers. Areliability assessment framework based on point estimation and higher-order moment theories is proposed to quantitatively assess the reliability of track geometry under the combined effects of highway loads, train loads, and temperature variations. The findings provide a systematic understanding of track geometry behavior on dual-use cable-stayed bridges and offer a robust methodological basis for ensuring the safety, reliability, and operational efficiency of high-speed railway systems on complex bridge structures.
Cosine Functionally Graded (CFG) plates offer a smoother material transition and better stiffness-to-weight ratios than traditional grading profiles. In this study, we investigate the buckling behavior of these plates using a recently developed Higher-Order Zigzag Theory (HOZT). The high-fidelity data generated from our HOZT model served as the training set for a Gradient Boosting Machine (GBM) algorithm. We used key parameters such as skew angle (Phi), boundary conditions, aspect ratio (a/b), side-to-thickness ratio (a/h) and gradient index (R) as input features to predict the critical buckling load ((P) over bar (cr)). Our numerical results, show that the GBM model is remarkably accurate. A parametric dataset is generated considering key variables, including skew angle (0 degrees-60 degrees), aspect ratio (a/b), side-to-thickness ratio (a/h=5-100), boundary conditions, and material gradient index (R). The results show that the non-dimensional critical buckling load significantly increases with skew angle (up to similar to 150% increase from 0 degrees-60 degrees) and decreases with increasing a/h, with the most pronounced variation observed for a/h <= 20.The GBM model demonstrates excellent predictive capability, with deviations from finite element results remaining negligible (typically less than 1% across all tested cases). Overall, this work demonstrates that coupling physics-based simulations with data-driven models is a highly effective way to reduce costs while maintaining the precision needed for the rapid stability assessment of advanced structures.
Short-crossbeam backfill in gob-side entry retaining is prone to lateral instability due to the caving gangue compression from gob, and lateral force point and angle are key influence factors on the stability. The instability of short crossbeam manifested as normal-stress bending failure and shear-stress cutting failure. The optimal bearing zone was in the transition zone between shear and compression. As loading point moved to the end, normal-stress failure load increased with crack propagation from the middle to the end, and shear-stress cutting load appeared at the position near the end and crack propagated towards the support point. Failure load was positively correlated with AE information, the correlation coefficients of loading positions and angles were 0.9722 and 0.9006 respectively. The influence of loading angle was less on failure load than the one of loading position: failure load increased by 2.60 times and by 1.16 times with loading position from the middle to the end and with loading angle from 0 degrees to 30 degrees respectively. The higher failure load, the greater fracture energy, the simpler crack propagation, and the more vertical the crack. The theoretical failure load of the maximum loading angle was consistent with the test result with 0.84% difference.
During service, reinforced concrete structures are exposed to various environmental conditions that can lead to corrosion damage in both the concrete and rebar, resulting in mass loss and degradation of the mechanical properties of these materials. This paper presents the results of an analysis of the behavior of short reinforced concrete columns with varying degrees of corrosion damage to the concrete and rebar, as well as the effects of strengthening these columns using different techniques and repair mate-rials. From the interaction curves between bending moment and axial force, we estimated the effect of corrosion damage intensity on the ultimate load capacity of the columns. Additionally, these interaction curves were utilized to evaluate the effectiveness of three different methods for strengthening columns that experienced specific corrosion damage, including the loss of concrete cover and part of the cross-section of the main reinforcement bars. The results indicated that the load-bearing capacity of the columns after strengthening significantly depends on the chosen strengthening techniques and the mechanical properties of the repair materials, as well as the loading conditions of the column. Therefore, when selecting reinforcement methods, techniques, and repair materials, it is crucial to consider the values of the sectional forces, particularly the relationship between the bending moment and axial force.
This paper presents a unified quasi-C1-PIM formulation for high-fidelity static and dynamic analysis of beams and plates with arbitrary cross-sections. The formulation integrates a novel eight-node quadrilateral element that achieves quasi-C1 continuity through an averaged dual-path interpolation scheme, enabling smooth stress fields without post-processing. Discretizing the cross-section with a quadrilateral mesh and constructing the threedimensional (3D) displacement field reduces the original problem to a one-dimensional (1D) formulation along the structural axis. An adaptive meshfree point interpolation method (PIM) with a tunable support-domain parameter n0 is employed as the axial solver, facilitating efficient p-convergence. The proposed method is systematically validated through a series of benchmark problems, including a rocket thrust frame, an L-shaped plate on an elastic foundation, thin-walled beams, composite beams, and frame structures under static and dynamic loading. The results exhibit excellent agreement with high-fidelity 3D finite element models while reducing the system degrees of freedom by 85-95% and achieving up to 3.7 & times; speedup and 61% memory reduction at comparable accuracy levels. Parametric studies confirm stable convergence with respect to cross-sectional mesh refinement, axial node density, and the support-domain parameter. By combining geometric generality, inherent stress smoothness, and computational efficiency, the quasi-C1-PIM framework provides a unified and reliable 1D numerical approach for analyzing complex beam and plate structures.
Steel shear walls are an innovative system that resist to lateral loads such as wind and earthquakes. In this paper, the effect of knee element on the behavior of moment resisting frame with steel shear wall has been numerically investigated by changing parameters such as the number and types of link beam (bending, bending-shear and shear behavior), shear wall thickness and span length-to-height ratio. The results showed, the most effective one that affect the bending behavior of the frame is the case with 4 link beams with shear behavior dominated. Also, by changing the length of the link beam from bending to bending-shear and then shear behavior, the values of stiffness, bending strength and dissipated energy have increased. Failure mode in this system depends on how the shear plate is connected to the boundary members. In the absence of knee element, stress is notably concentrated at the interface of beam to the column connection, Conversely, with the inclusion of 4 link elements, the damage and stress concentration are dispersed away from the links and widely distributed in the filler plate thus the maximum plastic capacity of steel shear plate is used. The results demonstrate that incorporating four shear-dominated link beams provides the most balanced improvement, enhancing the lateral stiffness, ultimate strength, and cumulative energy dissipation by up to 143%, 102%, and 112%, respectively, compared to an unreinforced wall. The performance of moment-resisting frames without link beams is characterized by a less effective distribution of stress and inelastic strain compared to other samples and in contrast, the presence of link beams has been associated with a re-hardening effect in the force-displacement response of steel shear walls, resulting in improved bending performance.
Structural design requires reliable life evaluation. This study employs an approach based on the second law of thermodynamics and entropy generation to assess damage and predict the lifespan of metallic workpieces under uniaxial creep loading. The Norton method was used to calculate initial creep strain rates, followed by determining entropy generation rates and cumulative entropy to quantify damage. The results aligned well with experimental data, demonstrating that entropy generation at the end of the secondary creep stage is stress-and temperature-independent and can be considered a material characteristic. The entropy growth rate increased significantly upon entering the tertiary creep region, mirroring the creep strain rate trend. Stress and temperature influenced entropy generation and damage, with higher stress or temperature accelerating damage propagation. Normalized entropy diagrams were developed and matched with normalized lifetimes across various stress and temperature conditions, revealing material-specific, stress-and temperature-independent correlations. These findings highlight the applicability of entropy-based models for reliable creep life prediction in metals.
This paper investigates the nonlinear low-velocity impact response of an axially moving functionally graded (FG) conical shell. The nonlinear equations of motion are derived based on Reddy's shell theory and von K & aacute;rm & aacute;n geometric nonlinearity. With simply supported boundary conditions, the time histories of deformation and contact force are solved numerically by combining the fourth-order Runge-Kutta method with the Galerkin technique, and the impact force is determined using the modified Hertzian contact model and Newton's second law. A key finding regarding the optimal volume fraction is that an intermediate ceramic content minimizes the central deflection under low-velocity impact, indicating a trade-off between stiffness and energy absorption. Additional numerical results reveal several key findings: (1) Increasing the prestress reduces the maximum central deflection while having negligible effect on the peak contact force, indicating an enhanced energy dissipation capability. (2) A larger damping coefficient accelerates the return to equilibrium after impact but only slightly decreases the maximum deflection. (3) Raising either the impactor radius or its initial velocity increases the peak deflection and contact force; however, a larger radius prolongs the contact time, whereas a higher initial velocity shortens it. (4) The axial motion speed of the conical shell affects the deflection more significantly than the contact force, suggesting that contact stiffness remains nearly unchanged. (5) The semi-vertex angle of the conical shell has a weak influence on the impact response. (6) Increasing porosity or the functionally graded index (i.e., reducing ceramic content) reduces structural to contact
This study presents and studies the application of normalized Modified Bouc-Wen model to capture the nonlinear hysteretic behavior of viscoelastic dampers under cyclic loading. Six different tests were conducted on viscoelastic dampers with different frequencies and amplitudes to evaluate their energy dissipation performance. The model considers strength and stiffness degradation effects using a normalized form to capture nonlinear hysteretic behavior based on applied loading and energy dissipation. Since identifying Modified Bouc-Wen parameters from the experimental results is a challenging task due to the complexity and interdependence of the parameters in the model formulation, the Particle Swarm Optimization (PSO) algorithm was applied. The first stage involved exploring a wide range of parameter values to identify reasonable value ranges, and the second stage applied refined bounds to improve accuracy. The calibrated model was validated by comparing its results with experimental hysteresis curves, confirming good agreement in both stress-strain response and energy dissipation. Furthermore, various machine learning regression models were trained using measurable input parameters. The output variables were the remaining Modified Bouc-Wen parameters derived from PSO-based optimization. Among the tested machine learning models, Gradient Boosting achieved the best performance, effectively estimating the Bouc-Wen parameters and reliably predicting the overall hysteretic behavior. SHAP analysis was conducted to interpret the model, indicating that stiffness and amplitude were the most influential features in estimating the Modified Bouc-Wen parameters.
In this paper, free vibration and buckling analysis of functionally graded Timoshenko beams are investigated. Stiffness and mass of Timoshenko beam are assumed to change using an exponential function along the beam length. Fredholm transformation approach is applied to solve the governing equation of motion. The usual method for applying Fredholm transformation is approximation of mode shape function by a power series that this method needs four repetitive integrations to obtain weak form of the governing equation. In this paper, a novelty is introduced into usual approach that is approximation of bending moment acting on the cross section of the beam by a power series. This novelty requires two successive integrations to obtain the weak form. Therefore, the mathematical process required is shorter and simpler. Regarding two integrations, two constants appear in the resulting weak form equation that are determined using appropriate boundary conditions for Timoshenko beam. Approximation of bending moment results in a system of linear algebraic equations that the natural frequencies are determined by calculation of a non-trivial solution for this system of equations. Buckling analysis of Timoshenko beam is also presented and the buckling loads are determined for beams with various end boundary conditions. The efficiency and accuracy of the presented approach are investigated through comparison of the numerical results with those available in the existing literature.
This study evaluates the performance of GPC modified with NiTi Shape Memory Alloy (SMA) fibers and waste rubber crumb (WRC) at elevated temperatures. For this purpose, in addition to the unreinforced concrete, mix designs with 0.25% and 0.5% of SMA and 10% WRC were designed and subjected to different tests at ambient temperature, 150 degrees C, 400 degrees C, 600 degrees C and 900 degrees C. It was concluded that at ambient temperature, SMA increases the compressive strength by 10.7%, while WRC reduces it by 27%. Moreover, at 150 degrees C, SMA0.5 exceeded its ambient strength by 2.8%, while the other specimens experienced a decrease in strength. Then, with increasing temperature, all samples experienced a decrease in compressive strength. In addition, splitting tensile strength of the fiber specimens at ambient temperature increased up to 36%, but at 400 degrees C decreased by about 20%, while this decrease was 48% in GPC, and the WRC experienced a decrease of about 21% at 400 degrees C. Furthermore, the flexural strength increased by 7% with the addition of SMA, but WRC caused a 13% decrease in strength. Overall, SMA provides effective crack bridging and thermal damage reduction at all temperatures, while WRC compromises strength.
As the state-of-the-art in seismic resilience evolves from basic life-safety toward damage mitigation and continuous functionality, piloti-type reinforced concrete (RC) buildings remain a critical vulnerability due to their inherent vertical irregularities. While extensive literature addresses general soft-story retrofits, few studies detail the specific plastic hinge evolution and directional isolator-column interactions required to optimize isolation strategies. To bridge this gap, this study evaluates a representative piloti-type RC prototype (Ministry of Land, Infrastructure and Transport, R.O.K.), explicitly selected because its mid-rise height, asymmetric wall layout, and column dimensions accurately represent the broader stock of vulnerable piloti structures. To ensure strict methodological reproducibility, including ASCE-41 plastic-hinge definitions, material nonlinearity parameters, and effective section properties, all modeling choices are comprehensively detailed in SAP2000. Also, distinct from dynamic earthquake simulations, this study employs displacement-controlled quasi-static analyses to systematically map capacity and collapse progression without ground motion variability. Comparative analyses in both principal directions for non-isolated and base-isolated (lead-rubber bearing) configurations reveal that the non-isolated frame develops collapse-level soft-story hinges at low displacements. On the other hand, the base-isolated model completes the prescribed displacement history without collapse by dissipating input energy through isolator hysteresis, dramatically reducing superstructure hinge demand and standardizing the inter-story drift profile. Differentiating this work from prior research, the results highlight that directional stiffness disparities and column sizing dictate energy absorption pathways as larger column sections and higher-stiffness axes significantly enhance isolator efficiency. The findings in this study provide novel, reproducible insights into typical piloti-type RC structural interactions, offering practical guidance for performance-based design in high-density urban seismic regions.
Under the evolution of traffic flow, Modular Expansion Joints (MEJs) needs to meet the needs of adapting to constrained deformation on both sides while bearing direct vehicular loads. This operational state results in continuous non-uniform spatial coupling of multiple internal components under time-varying load, making the wear assessment of inter-component connecting materials both complex and essential. Firstly, based on the spatial movement patterns of the internal components and the locations of connecting materials in MEJs, the wear forms of the connecting material between the components are determined and the indicators are parameterized, and the spatial index system for wear in MEJs is proposed. Secondly, simulate the evolution of operational traffic flow, establish a bridge-expansion joint orthogonal model at the same scale, solve the switching and allocation of vehicle load forms on the model, and improve the traffic-bridge-expansion joint analysis system. Finally, taking a typical cable-stayed bridge equipped with MEJs as the engineering background, the wear indicators of MEJs under the evolution of traffic flow are analyzed. The results show that: (1) the patterns of wear of connecting materials in the MEJs is different from the rule of absolute displacement of center beam commonly used in the evaluation of MEJs, and there is also a multiple difference in the value. The absolute displacement of center beam cannot be used for the evaluation of wear of MEJs; (2) the cumulative relative displacements between adjacent center beams and between upper/lower beams all exhibit monotonically decreasing trends from both sides toward the middle of the MEJs structure. The minimum and maximum wear indicators of shear springs show a difference of approximately 9.2 times, while the wear indicators of bearing between upper/lower beams demonstrate a difference reaching 21.24 times. The shear springs and connecting materials between upper/lower beams require differentiated parameter designs. Connecting materials within the same-side displacement box may adopt identical parameters, whereas those on different sides require differentiated designs.
For concrete beams reinforced with hybrid fiber reinforced polymer (FRP)-steel bars, prevailing codes typically employ the neutral axis depth (c/d) to quantify the degree of moment redistribution (beta). Nonetheless, this parameter predominantly reflects sectional behavior and may not accurately capture global structural response. Furthermore, the inherent bond-slip between FRP and concrete significantly influences the moment redistribution characteristics of the structure. To address these deficiencies, this research develops a finite element (FE) model that explicitly incorporates bond-slip effects. An improved simplified model for predicting moment redistribution is also proposed, highlighting the influence of relative stiffness, expressed as rho t1/rho t2, where rho t1 and rho t2 represent the effective reinforcement ratios in the sagging and hogging moment regions, respectively. Numerical analyses demonstrate that the beta is dictated not only by c/d, but is also strongly governed by rho t1/rho t2. Accordingly, the BSI model is modified to incorporate both c/d and rho t1/rho t2 as key parameters within the redistribution assessment framework. Comparative evaluation against FE model results confirms that the proposed simplified model significantly improves prediction accuracy for beta, affirming its applicability and reliability for this class of beams.
This study investigates the thermoelastic behavior of thick-walled truncated conical shells with a constant middle radius and linearly varying thickness under mechanical loading and bi-directional thermal gradients. The governing equations are formulated using First-Order Shear Deformation Theory (FSDT) combined with First-Order Temperature Theory (FTT), and are solved semi-analytically using the disk-form multilayer method (MLM). The analytical results are validated by finite element simulations, which show excellent agreement in radial displacement and stress distributions. Parametric analyses indicate that radial displacement and equivalent stress increase along the shell length and become more pronounced at higher angular velocities, while shear stresses remain negligible. These results provide valuable insights into the thermoelastic response of rotating conical pressure vessels and similar high-temperature structural components.
Evaluating the impact resistance of ferrocement channels is essential for their application in low-cost roofing and similar structural components. This study investigates the impact response and crack propagation behaviour of unreinforced and steel fibre-reinforced ferrocement channels subjected to repeated drop-weight impact loading. Impact performance was assessed in terms of energy at first cracking and failure, post-crack resistance, ductility, and crack width evolution. Experimental results demonstrated that steel fibre reinforcement significantly enhanced impact toughness, with approximately 2.4-fold increase at first crack and nearly 4-fold increase at failure, and increased the impact ductility index by about 70%, indicating a clear transition from brittle to ductile behaviour. Fibre inclusion also reduced crack width by up to 68% and maintained narrow crack openings under repeated impacts. A numerical parametric study showed that steel fibres enhanced impact energy absorption by 7.6-14.9% depending on the number of welded mesh layers, while increasing mesh layers beyond two offered marginal benefits. Randomly oriented fibres exhibited higher impact toughness than planar orientation, with improvements of up to 37%. Overall, two layers of welded mesh were found to provide optimal impact resistance, irrespective of fibre presence.
Designing fiber-reinforced concrete (FRC) panels to resist projectile impact is a challenging task, as it requires balancing the panel's failure resistance with construction feasibility, such as minimizing its weight. These objectives often conflict since lighter FRC panels tend to be more vulnerable to damage than heavier ones. Additionally, the panels must be designed to achieve predefined failure modes. To address these challenges, this study develops a multi-objective optimization process to minimize both the penetration ratio and the weight of FRC panels under missile impact while incorporating failure mode as a constraint. The optimization process is implemented using the nondominated sorting genetic algorithm-II (NSGA-II). Machine learning (ML) models are employed to predict penetration depth and classify failure modes using experimental datasets. However, due to the dataset's limitations, including class imbalance and insufficient samples, the k-means SMOTE technique is applied to generate additional data for the minor classes. Moreover, the Giant Trevally Optimizer (GTO) is utilized to adjust the hyperparameters of the ML models, aiming to achieve optimal performance. The results demonstrate that kmeans-SMOTE and GTO algorithms significantly improve the predictive accuracy of the models. Furthermore, the optimization algorithm effectively identifies multiple optimal solutions, exhibiting a clear trade-off between the objectives. The strong convergence toward boundary values and the even distribution of Pareto-front points confirms the algorithm's efficiency in exploring the solution space. Finally, a cloud-based platform is developed to employ the application of the proposed model in real-world design processes.
This study explores the impact of soil-structure interaction on the design and analysis of a base-isolated RC frame building. The building's preliminary design employs the direct-displacement base design approach for low design inter-story drift that is compatible with the fully operational performance range. The lead rubber bearing serves as an isolator for the isolated building. The design forces and moments are determined by simulating the single-degree-of-freedom, base-isolated building, taking into consideration the impact of soil-structure interaction. The foundation is meant to keep eccentricity and safety factors within acceptable ranges. It is considered that the lateral deformation components include displacement generated by the isolator, the superstructure, and the foundation's rocking and swaying relative to the soil. The difference between the basic period with and without soilstructure interaction is also investigated. The approach is confirmed by time-history analysis of various soil profiles and base-isolated building layouts.
This study examines the role of aluminosilicate nanotubes (ANTs) in improving the performance of thermally cured geopolymer concrete (GPC) prepared using Class F fly ash and metakaolin. The main objective is to enhance early-age strength, durability, and microstructural stability of GPC under high-temperature conditions relevant to geothermal environments. ANTs were incorporated at 0-3.0 wt% of binder, and specimens were cured at 80 degrees C. A systematic experimental program was conducted, including tests on flowability, compressive and tensile strength (3 h to 28 days), drying shrinkage, water absorption, and pore structure. Microstructural and chemical analyses were performed using XRD, FTIR, SEM, and TGA/DTG. Statistical evaluation was carried out using ANOVA and Tukey's HSD test to confirm the significance of results. Results show that ANTs reduce workability due to increased water absorption. However, significant improvements in mechanical and durability properties were observed. The optimum dosage of 2.0 wt% ANTs increased 1-day compressive strength by 32.77% and enhanced early tensile strength by up to 191%. This mix also showed the lowest water absorption and drying shrinkage, along with a denser pore structure. Microstructural results confirmed improved gel formation and matrix compactness. Hence, the study demonstrates that controlled incorporation of ANTs, especially at 2.0 wt%, can effectively enhance the performance of thermally cured GPC. This approach offers a durable and sustainable solution for construction in high-temperature environments such as geothermal tunnels.
