Search Results (599)

Pervious concrete is a promising sustainable pavement material for sponge city construction. The incorporation of Steel Slag Aggregate (SSA) as a substitute for natural aggregates has the double role of clean production with significant economic and environmental benefits. While the strength and permeability, known as two critical design parameters of pervious concrete, are closely linked to its porosity, there is limited research on the influence of the porosity on the mechanical properties of pervious concrete. In this paper, both experimental and numerical investigations were performed, focusing on the influence of target porosity on the strength and permeability of pervious concrete with and without SSA. Three different target porosities (15%, 20%, and 25%), five distinct water-to-cement (w/c) ratios (0.25, 0.28, 0.30, 0.33, and 0.35), and five SSA replacement ratios (0, 25%, 50%, 75%, and 100%) were considered in this study. A two-dimensional (2D) finite-element (FE) model was developed, with which the failure mode and the strength variation of pervious concrete under different target porosities were analyzed and verified with the experimental results. The results showed that the porosity had a significant influence on both the strength and permeability of pervious concrete, while the influence of the w/c ratio is marginal. There existed an optimal w/c ratio of 0.3, for which pervious concrete with porosities of 15%, 20%, and 25% achieved 28-day compressive strengths of 27.8, 20.6, and 15.6 MPa and permeability coefficients of 0.32, 0.58, and 1.02 cm/s, respectively. Specifically, at the lowest porosity of 15%, the replacement of 100% SSA resulted in the largest improvement in the compressive strength up to 37.86%. Based on the regression analysis, a series of empirical equations correlating the porosity, strength and permeability of pervious concrete was formulated and validated against the experimental data. The findings presented herein are expected to provide references to the practical evaluation of the optimal mix proportion of previous concrete, considering specific and demanding engineering requirements. Full article

Glass fiber-reinforced polymer (GFRP) composites exhibit significant advantages over conventional structural webbing materials, including lightweight and corrosion resistance. This study investigates the localized compression performance of the proposed GFRP grid web–concrete composite beam through experimental and numerical analyses. Three specimen groups with variable shear-span ratios (λ = 1.43, 1.77) and local stiffener specimens were designed to assess their localized compressive behavior. Experimental results reveal that a 19.2% reduction in shear-span ratio enhances ultimate load capacity by 22.93% and improves stiffness by 66.85%, with additional performance gains of 77.53% in strength and 94.29% in stiffness achieved through local stiffener implementation. In addition, finite element (FE) analysis demonstrated a strong correlation with experimental results, showing less than 5% deviation in ultimate load predictions while accurately predicting stress distributions and failure modes. FE parametric analysis showed that increasing the grid thickness and decreasing the grid spacing within a reasonable range can considerably enhance the localized compression performance. The proposed analytical model, based on Winkler elastic foundation theory, predicts ultimate compression capacities within 10% of both the experimental and numerical results. However, the GFRP grid strength adjustment factor β_g should be further refined through additional experiments and numerical analyses to improve reliability. Full article

The structural health monitoring of historic buildings represents one of the most significant challenges in contemporary structural analysis, particularly for large-scale structures with accumulated damage. Obtaining reliable diagnostics is crucial yet complex due to the inherent uncertainties in both geometric definition and material properties of historic constructions, especially when structural stability may be compromised. This study presents a comprehensive structural assessment of the Bullring of the Real Maestranza de Caballería de Ronda (Spain), an emblematic 18th-century structure, through an innovative multi-technique approach aimed at evaluating its structural stability. The methodology integrates various non-destructive techniques: 3D laser scanning for precise geometric documentation, operational modal analysis (OMA) for global dynamic characterisation, experimental modal analysis (EMA) for local assessment of critical structural elements, and sonic tests (ST) to determine the elastic moduli of the principal materials that define the historic construction. The research particularly focuses on the inner ring of sandstone columns, identified as the most vulnerable structural component through initial dynamic testing. A detailed finite-element (FE) model was developed based on high-precision laser-scanning data and calibrated using experimental dynamic properties. The model’s reliability was validated through the correlation between numerical predictions and experimental observations, enabling a thorough stability analysis of the structure. Results reveal concerning stability issues in specific columns of the inner ring, identifying elements at significant risk of collapse. This finding demonstrates the effectiveness of the proposed methodology in detecting critical structural vulnerabilities in historic buildings, providing crucial information for preservation strategies. Full article

Aero-engine casings with excellent impact resistance are a practical requirement for ensuring the safe operation of aero-engines. In this paper, we report on numerical simulations of broken rotating blades impacting aluminum honeycomb sandwich casings under different temperatures and optimization of structural parameters. Firstly, an impact test system with adjustable temperature was established. Restricted by the temperature range of the strain gauge, ballistic impact tests were carried out at 25 °C, 100 °C, and 200 °C. Secondly, a finite element (FE) model including a pointed bullet and an aluminum honeycomb sandwich plate was built using LS-DYNA. The corresponding simulations of the strain–time curve and damage conditions showed good agreement with the test results. Then, the containment capability of the aluminum honeycomb sandwich aero-engine casing at different temperatures was analyzed based on the kinetic energy loss of the blade, the internal energy increment of the casing, and the containment state of the blade. Finally, with the design objectives of minimizing the casing mass and maximizing the blade kinetic energy loss, the structural parameters of the casing were optimized using the multi-objective genetic algorithm (MOGA). Full article

The present study intends to assess the ratcheting response of SA508 and SA333 steel alloys subjected to asymmetric loading cycles at various operating temperatures of 298, 573, and 623K through a hardening framework developed by Ahmadzadeh–Varvani (A-V) and the finite element analysis structured by the Chaboche hardening model (CH) in the ANSYS software program. The dynamic recovery terms in the A-V and CH hardening framework consisted of temperature-dependent parameters and functions to address the dynamic strain aging (DSA) phenomenon at high temperatures of 573 and 623 K. The DSA phenomenon reported at elevated temperatures was attributed to the interactions of solute atoms and dislocations with a certain temperature, resulting in higher material strength and lower ratcheting deformation. The coefficients of these frameworks were analytically determined through stress–strain hysteresis loops obtained from the strain-controlled cyclic tests. The FE analysis was applied to numerically evaluate backstress evolution through use of the CH model. Two popular nonlinear brick and tetrahedron element types were examined to study the convergence of the elemental system with various numbers of elements. This ensured the independence of the simulated results from the number of elements and their convergence. The simulated ratcheting responses for brick and tetrahedron solid elements were compared to those predicted analytically by the A-V hardening rule and experimentally measured values. The predicted and simulated ratcheting data were found to be in good agreement with the measured data. The predicted and simulated ratcheting results generated using the A-V and FEA approaches showed $R^2$ values of 0.96 and 0.85, respectively, when compared with the experimental data. Full article

The growing application of soil–geosynthetic composites (SGCs) in geotechnical engineering has highlighted the critical role of reinforcement spacing in enhancing structural performance. This study presents a numerical investigation of the stress–deformation behavior of SGC masses under working stress and failure load conditions, considering both confining and unconfined pressure scenarios. A finite element (FE) model was developed to analyze stress distribution, reinforcement strain profiles at varying depths, and lateral displacement at open facings. Results revealed that vertical stresses in reinforced and unreinforced soil masses were nearly identical, while lateral stresses increased notably in reinforced masses, particularly near reinforcement layers and open facings. Closer reinforcement spacing (0.2 m) effectively reduced lateral displacement and enhanced structural stability compared with wider spacing (0.4 m). In some cases, strengthening reinforcement in the upper portion of the SGC mass proved more effective under failure loads in both confining and unconfined pressure conditions. These findings provide critical insights for optimizing reinforcement spacing in SGC systems, with implications for the design of retaining walls and bridge abutments. Full article

In the context of sustainable manufacturing practices, minimum quantity lubrication (MQL) has been extensively employed in machining operations involving hard-to-cut materials. While substantial experimental and numerical investigations on MQL-assisted machining have been conducted, existing simulation approaches remain inadequate for modeling the dynamic flow field variations inherent to MQL processes, significantly compromising the predictive reliability of current models. This study introduced an innovative bidirectional iterative coupling framework integrating finite element (FE) analysis and computational fluid dynamics (CFD) to enhance simulation accuracy. Since fluid flow characteristics critically influence tribological and thermal management at the tool–workpiece interface during machining, CFD simulations were initially performed to evaluate how MQL parameters govern fluid flow behavior. Subsequently, an integrated FE-CFD modeling approach was developed to simulate Ti-6Al-4V alloy turning under MQL conditions with varying feed rates. The novel methodology involved transferring thermal flux data from FE simulations to CFD’s heat source domain, followed by incorporating CFD-derived convective heat transfer coefficients back into FE computations. This repetitive feedback process continued until the thermal exchange parameters reached convergence. Validation experiments demonstrated that the proposed method achieved improved alignment between the simulated and experimental results for both cutting temperature profiles and principal force components across different feed conditions, confirming the enhanced predictive capability of this coupled simulation strategy. Full article

The roof slab, as a critical component for partitioning the vertical space within RC frame structures, can effectively mitigate the propagation of shock waves and reduce damage levels in adjacent rooms. This study employed finite element (FE) modeling to investigate the vertical propagation of blast waves and roof ejection velocity in RC frames. The model’s reliability was verified by reconstructing internal explosion tests on RC frames and close-in explosion tests on masonry walls. On this basis, two typical single-room RC frame structures that are vertically adjacent were designed, and numerical simulations of the internal explosion were conducted under four explosive equivalents and four venting coefficients. The propagation of shock waves, load characteristics in the vertically adjacent room, and the dynamic response of roof slabs were examined. The results show that shock waves propagated to the vertically adjacent room decreased by approximately two orders of magnitude for peak overpressure and one order of magnitude for impulse due to the obstruction of shock waves by roof slabs, respectively, compared to the source explosion room. For larger venting coefficients, abundant energy was released through the venting openings, making it difficult to form a quasi-static pressure with a long duration inside the source explosion room. In addition to the shock wave, the explosive ejection of roof slabs in the explosion source room will further exacerbate the damage to the vertically adjacent room. Peak overpressure and impulse propagated to the vertically adjacent room were reduced significantly by the increase in the venting coefficient, resulting in an attenuation of structural damage. Finally, empirical models incorporating the venting coefficient were established to characterize the attenuation coefficients of power parameters, demonstrating the predictive capability for peak overpressure, impulse, and roof ejection velocity in both the explosion source room and the vertically adjacent room. Full article

In the assembly of spacecraft cabins, the presence of uncertain and time-varying temperature environments can induce thermal deformation in bulkheads, potentially affecting dimensional stability. Online sensing of thermal deformation is critical for mitigating such risks. However, conventional finite element methods (FEMs) rely on cascading thermal and structural analyses, which suffer from inefficiency. To address this issue, we propose a methodology that integrates a physical model with a data-driven temperature field measurement technique, demonstrated through case studies involving a spacecraft porthole bulkhead. First, leveraging the geometric invariance of the bulkhead during assembly, a purely static FE model is established offline. Second, multi-point temperature measurements combined with Kriging estimation are employed to directly reconstruct the temperature field, circumventing the computationally intensive FEM-based thermal analysis process. Finally, by utilizing the precomputed inverse stiffness matrix and performing an online conversion from temperature to equivalent forces, thermal deformation is rapidly resolved. The numerical results demonstrate that the root-mean-square errors of the predicted full-field deformation are maintained at the micron level, with an average computation time of less than 0.14 s. Furthermore, a meticulously designed experiment was conducted, where the predicted thermal displacements of several key points showed good agreement with measurements by means of a laser tracker. This research provides a promising tool to achieve digital twinning of thermal deformation states for aerospace components. Full article

Flax fiber reinforcements weaken with aging and microstructural changes, limiting their applications. Here, we examine the effects of microstructure and aging on flax fiber elements’ performance by using 4000-year-old and modern Egyptian flax as references through multi-scale numerical modeling. This study introduces a novel investigation into the tensile stress distribution behavior of archaeological and modern flax yarns. The finite element (FE) model is derived from 3D volumes obtained via X-ray microtomography and tensile testing in the elastic domain. At the microscale, fibers exhibit higher axial stress concentrations around surface defects and pores, particularly in regions with kink bands and lumens. At the mesoscale, fiber bundles show increased stress concentrations at inter-fiber voids and lumen, with larger bundles exhibiting greater stress heterogeneity, especially around pores and surface roughness. At the macroscale, yarns display significant stress heterogeneity, especially around microstructural defects like pores and fiber–fiber cohesion points. Aged fibers from ancient Egyptian cultural heritage in particular demonstrate large fiber discontinuities due to long-term degradation or aging. These numerical observations highlight how porosity, surface imperfections, and structural degradation increase stress concentration, leading to fiber rupture and mechanical failure. This insight reveals how aging and defects impact flax fiber performance and durability. Full article

As a key roadside safety feature, longitudinal guardrail steel barriers are purposefully designed to contain and redirect errant vehicles to prevent roadway departure, dissipate impact energy through plastic deformation, and reduce the severity of vehicle crashes. Nevertheless, these systems should be carefully designed and assessed, as localized rupturing, especially near splice or impact locations, can lead to catastrophic failures, compromising vehicle containment, violating crash safety standards, and ultimately jeopardizing the safety of occupants and other road users. Before conducting full-scale crash testing, finite element analysis (FEA) tools are widely employed to evaluate the design efficiency, optimize system configurations, and preemptively identify potential failure modes prior to expensive physical crash testing. To accurately assess system behavior, calibrated material models and precise failure criteria must be utilized in these simulations. Despite the existence of numerous failure criteria and material models, the material characteristics of AASHTO M-180 guardrail steel have not been fully investigated. This paper significantly advances the FE modeling of ductile fracture in guardrail steel, addressing a critical need within the roadside safety community. This study formulates stress-state-dependent failure criteria and proposes advanced material modeling techniques. Extensive experimental testing was conducted on steel specimens having various triaxiality and Lode parameter values to reproduce a wide spectrum of complex, three-dimensional stress-state loading conditions. The test results were then used to identify material properties and construct a failure surface. Subsequent FEA, which incorporated the Generalized Incremental Stress-State-Dependent Damage Model (GISSMO) in conjunction with two LS-DYNA material models, illustrates the capability of the developed surface and material input parameters to predict material behavior under various stress states accurately. A parametric study was completed to further validate the proposed models, highlighting their robustness and reliability. Full article

This study investigates the structural performance and load-bearing capacity of single- and double-story modular bridge configurations using both experimental testing and finite element analysis. A full-scale field test was conducted on a 45.7 m double-story bridge subjected to truck loading at ten distinct positions along the span. Midspan deflections and axial strains of key members were measured and analyzed at each loading position to assess the bridge’s response under service loads. The experimental data were used to validate three-dimensional finite element (FE) models and refine modeling techniques for the double-story modular bridge. The validated FE models enabled further analysis of the structural performance of double-truss–double-story (DD) and quadruple-truss–single-story (QS) modular bridge configurations, both in single- and double-lane setups. The numerical results demonstrated that the double-story configuration with double truss lines per side provided a notable improvement in stiffness and load-carrying capacity compared to the single-story configuration with quadruple truss lines. Moreover, single-lane bridges exhibited better performance than their double-lane equivalents, emphasizing the impact of bridge width on structural stability. Wider, double-lane bridges were found to be more prone to out-of-plane buckling at midspan, with the top chords experiencing significantly greater deformation. Buckling analyses indicated that, although the DD and QS configurations had comparable critical loads, their failure mechanisms differed. Finally, live load factors predicted through the models were compared with the requirements of the Canadian Highway Bridge Design Code (CHBDC), confirming that the DD configuration in a two-lane setup meets code expectations and demonstrates effective structural performance. Full article

This paper examines the hysteretic behavior of the buckling restrained braces (BRBs) in the steel frame. Both experimental and finite element (FE) studies were conducted. The experimental results showed that the well-detailed buckling restrained braced frame (BRBF) withstood significant drift demands, while the BRB exhibited significant yield without severe damage. Although the BRB inside the steel frame was subjected to 2.69% strain of the CP under the axial compression demands, the local and global deformations were not observed. The FE model was developed and validated. The numerical investigations of hysteretic behavior of the BRBF in the literature are generally focused on the friction between the core plate (CP) and the casing member (CM). The results suggest that the behavior of the BRBF is significantly affected not only by the friction between CP and CM but also by the pretension load on the bolts and the friction between the contact surfaces of steel plates of slip-critical connections in the steel frame. The FE analysis showed that pretension loads of 35 kN and 75 kN gave accurate predictions for cyclic responses of BRBF under tension and compression demands, respectively. Moreover, the FE predictions were in good agreement with the test results when the friction coefficient is 0.05 between CP and CM and it is 0.20 between steel plates. Full article

Salts can have detrimental effects on asphalt pavements, leading to permanent damage that compromises their durability and sustainability. This study investigates the damage mechanisms of asphalt pavements under coupled salt–thermal–mechanical effects using multi-scale modeling. Pull-off and semicircular bending (SCB) tests were conducted to determine material parameters and validate numerical models. Experimental data demonstrated that after 48 h of salt treatment at −10 °C, specimens exhibited reductions in cohesive strength ranging from 23.5% to 26% and adhesive strength decreasing by 25% to 44% compared to untreated controls. More severe degradation was observed at 0 °C, with cohesive strength diminishing by up to 63.8% and adhesive strength declining by up to 71.6%. A multi-scale finite element (FE) pavement model incorporating cohesive zone modeling (CZM) was developed to simulate damage behavior within asphalt concrete. Salt diffusion analysis revealed limited penetration depth within short exposure periods, and results showed that salt penetration reached only about 10 mm into the pavement layers after 48 h. Results indicated significant reductions in adhesive and cohesive strengths due to salt exposure, with damage susceptibility increasing under combined thermal fluctuations and mechanical loading. Additionally, the effects of moving load magnitude and speed on pavement damage were examined, showing higher damage accumulation at lower speeds and heavier loads. This research provides insights into pavement deterioration mechanisms, contributing to improved durability and maintenance strategies for asphalt pavements in salt environments. Full article

Springback control is a critical factor in profile stretch-bending-torsion forming. A new stretch-bending-torsion automatic forming method based on the mixture of finite element and BP neural network (FE-BPNN) is proposed. The method enhances the shape accuracy of profiles after single-step forming. Initially, the study introduces the 3D multi-point stretch-bending and torsion (3D MPSBT) forming machine and its forming principles. Subsequently, it details the springback prediction method and automatic forming control approach based on BPNN. A springback control model is established through numerical simulation and experiments. The proposed springback control method is compared with a springback factor-based approach from other researchers using hollow rectangular profiles undergoing combined bending and torsion deformation as the research object. The results validate the effectiveness and advantages of the proposed method. Full article