Search Results (220)

This study investigates the seismic retrofit of historic single-nave churches through the optimization of roof diaphragms designed to enhance energy dissipation. The proposed strategy introduces a deformable box-type diaphragm above the existing roof, composed of timber panels and steel connectors with a cover of steel stripes, where energy dissipation is concentrated in the connections. The retrofit design is guided by the estimation of Equivalent Damping Ratio (EDR) instead of the usually adopted resistance criterion, considering an energy-based approach to improve global seismic performance while preserving architectural integrity. In this way, the retrofitted configuration of the roof can be considered a damper. Three numerical phases are presented to assess the effectiveness of the equivalent damping-based intervention. In the first one, the seismic response of the initial non-retrofitted configuration is implemented using a 3D linear finite element model subjected to a response spectrum. Subsequently, nonlinear equivalent models subjected to spectrum-compatible accelerograms are implemented, simulating the possible retrofitted configurations of the roofs to detect the optimum damping and finding the corresponding roof diaphragm configuration. In the third one, the response of the detected retrofitted configuration is also evaluated by nonlinear 3D model subjected to accelerograms. The three phases with the relative numerical approaches are here applied to a case study, located in a high seismic hazard area. The results demonstrate that the EDR-based methodology can optimize the retrofitted roof diaphragm configuration; the nave transverse response is improved in comparison with that designed with the traditional approach, considering only the over-strength of the interventions. Comparisons about the approaches based on the EDR and the strength criteria are presented in terms of lateral displacements, in-plane shear acting on the roof diaphragm, and in-plane stresses on the façade. Full article

This study examines the in-plane compression behavior of sandwich panels produced with additive manufacturing. This study focuses on two types of honeycomb unit cell topologies with larger dimensions: a hexagonal one and a re-entrant one. For each panel geometry, two material configurations were examined: Onyx (a nylon-based composite) and Onyx reinforced with 10% continuous carbon fibers (CCFs) by mass. The objective was to assess the influence of fiber reinforcement on the mechanical performance and deformation response of the panel structures. In-plane compression tests were conducted to determine the stiffness, strength, and failure modes of the specimens. Additionally, the digital image correlation (DIC) technique was used to capture full-field strain distributions and analyze local deformation mechanisms during loading. The results revealed distinct mechanical responses between the two geometries: the re-entrant structure exhibited auxetic behavior and enhanced energy absorption characteristics. Although reinforced honeycomb panels have an average load capacity that is 35% higher, they fail at a displacement that is approximately 55% smaller compared to unreinforced panels. Despite accounting for only 25% of the total number of layers and 10% of the panel’s mass, the reinforcement achieved superior strength. Re-entrant panel testing showed a 25% force increase in favor of the reinforced variant. They fail at a displacement that is 36.5% greater than that of reinforced honeycombs. This demonstrates a more compliant response while also maintaining 4.9% greater strength, indicating the superior behavior of auxetic reinforced sandwich panels. Introducing CCF reinforcement increased the load-bearing capacity and reduced localized strain concentrations without altering the overall deformation pattern. These findings suggest that enhancing materials can increase the strength and flexibility of 3D-printed re-entrant structures, providing valuable insights for lightweight design and optimized material use in structural applications. Full article

In-plane shear is the dominant deformation mode during thermoforming of fiber-reinforced composites, and accurate characterization of shear behavior is essential for reliable forming simulations. The present work investigates the shear response of a unidirectional cross-ply UHMWPE material system (DSM Dyneema^® HB210) using the picture-frame test, with emphasis on sample configuration, normalization methods, and shear rate effects. Three cruciform sample sizes were tested at 120 °C, along with a configuration in which cross-arm material was removed to isolate the gage region. Finite element analyses using LS-DYNA^® were performed to evaluate the shear rate distribution during forming and to validate the experimental characterization. To maintain a constant shear rate during testing, a decreasing crosshead speed profile was implemented in the test software. Results showed that normalizing by the full specimen area yielded consistent shear stiffness curves across sample sizes, indicating that the arm region contributes equally to the load. Samples with cross-arm material removed exhibited greater scatter than those specimens without cross-arm material removed, confirming that preparation of cross-arm removal complicates repeatability. Rate dependence was observed at room temperature but not at elevated processing temperatures, suggesting that rate-dependent shear models are unnecessary for forming simulations of this material system. These findings provide a practical methodology for shear characterization of UHMWPE cross-ply laminates suitable for thermoforming analyses. Full article

The anti-pillow effect of mesh antennas has adverse effects on satellite communication. The curvature isotropy of a negative Poisson’s ratio material is expected to be applied and solved for the anti-pillow effect of mesh deployable antennas. Based on the tension characteristics of mesh antennas, our research group has proposed a novel pre-wound six-ligament chiral material, and provided the analytical solutions of Poisson’s ratio and Young’s modulus under the assumption of a small deformation. Following on from the above work, this paper takes into account the variable curvature deformation of pre-wound ligaments and the bending deformation of straight ligaments. The analytical solutions of Poisson’s ratio and Young’s modulus under large deformations are derived, and verified by finite element simulation combined for both small and large deformations. The results show that theoretical solutions considering large deformation of the ligament are more consistent with the simulation results in the large-strain range of anisotropy in the material plane. The analytical solution of Young’s modulus derived from the energy equivalent principle of elastic deformation with a curved beam and a straight beam is consistent with the simulation results under large tensile strain. It has been verified that the existence of a pre-wound ligament can slow down the deformation of the node and reduce the loss of in-plane isotropy to a certain extent, so it is easier to maintain the negative Poisson’s ratio characteristic and maintain an excellent in-plane isotropic deformation mechanism over a larger strain range under tensile load. This characteristic proves the reliability of the prospects applying the pre-wound six-ligament chiral structure in deployable mesh antennas, which lays a theoretical foundation for the subsequent prototype. Full article

This work examines how rolling speed, feeding rate, and pass schedule—with a constant total reduction—affect the stress–strain fields, rolling force, and texture evolution of Al–Cu–Sc alloy sheets. A coupled finite element (FEM) and viscoplastic self-consistent (VPSC) framework is employed and compared with EBSD measurements to connect macroscopic fields with microscale texture changes. Results indicate that increasing rolling speed raises the effective strain rate and deformation heating, which lowers peak rolling force and improves in-plane stress homogenization on the RD–ND plane, while enhancing surface–core incompatibility and residual-stress gradients along the ND–TD direction. A higher feeding rate mainly intensifies work hardening, slightly elevates rolling force, and promotes near-surface stress/strain localization; in contrast, multi-pass schedules redistribute deformation between passes and reduce macroscopic stress concentration. Texture analyses show a speed-induced rotation from $⟨001⟩$ toward $⟨111⟩$ orientations, strengthening shear-related components; KAM maps suggest increased local orientation gradients consistent with higher stored energy. The simulations capture the principal experimental trends across conditions, supporting the use of the combined framework for trend-level process guidance. Overall, the findings clarify parameter–microstructure relationships and provide a basis for designing rolling routes that balance force reduction, stress uniformity, and texture control in Al–Cu–Sc sheets. Full article

Bulk acoustic wave (BAW) resonators, with their exceptional high-frequency performance and excellent quality factor, have become a key driver of advances in sensing technology. This study reports the fabrication and characterization of a force sensor based on a solid mounted resonator (SMR) structure. This SMR device utilizes a high resonance frequency of 2.257 GHz as its core sensing element. The operational mechanism involves the application of an external load inducing localized downward mechanical deformation in the SMR film at the pin contact region, thereby generating significant in-plane compressive stress within the piezoelectric layer. The applied strain modifies the intrinsic elastic and piezoelectric constants of the film, thereby changing both the acoustic phase velocity and the electromechanical coupling coefficient ($K_t^2$), which ultimately leads to a measurable shift in the resonance frequency. The experimental results reveal a deterministic and robust correlation between the resonance frequency shift and the applied load, which forms a precise function relationship enabling the device to achieve a high sensitivity of 37.79 MHz/N. This indicates that it may possess good application and development potential in various complex industrial fields. Full article

To improve the seismic performance of semi-rigid steel frame beam–column joints connected by T-stubs, reinforced T-stubs formed via wedge-shaped and thickening modifications are proposed. Taking the middle column joints in steel frames as the research objects, three types of beam–column joints are designed by adopting ordinary, wedge-shaped, and thickened wedge-shaped T-stubs. To conduct a comparative analysis of the seismic performance of the test specimens, this study imposes low-cycle cyclic loads on the column ends of each specimen along their major-axis and minor-axis in-planes. This loading protocol is adopted to simulate the dynamic responses of the specimens under bidirectional seismic action. Comparing the macroscopic failure phenomena of the specimens, the influence of reinforced T-stubs on the plastic development mode of the joints is analyzed. Based on seismic indicators such as hysteresis characteristics, skeleton curves, stiffness degradation, and energy dissipation capacity, the energy dissipation capacity of the specimens along the major-axis is greater than that along the minor-axis, but their deformation capacity is slightly reduced. The bearing capacity, energy dissipation, and rotational stiffness could be improved by reinforced T-stubs, but the deformation capacity is reduced to varying degrees. The stiffness degradation rate of the specimen adopting wedge-shaped T-stubs shows a more obvious accelerating trend. Through the comparative analysis of the three specimens based on the energy damage index, the results indicate that wedge-shaped T-stubs significantly increase the damage degree of the specimens, but thickened wedge-shaped T-stubs have a relatively small impact on the evolution of joint damage. Full article

Concrete creep and shrinkage are critical factors affecting the long-term performance of extradosed bridges, leading to deflection, stress redistribution, and potential cracking. Predicting these effects is challenging due to uncertainties in empirical models and a lack of long-term data. While beam element models are common in design, they often fail to capture complex stress fields in disturbed regions (D-regions), potentially leading to non-conservative assessments of crack resistance. This study presents a computationally efficient probabilistic framework that integrates the First-Order Second-Moment (FOSM) method with a high-fidelity solid element model to analyze these time-dependent effects. Our analysis reveals that solid element models predict 14% higher long-term deflections and 64% greater sensitivity to creep and shrinkage parameters compared to beam models, which underestimate both the mean and variability of deformation. The FOSM-based framework proves highly efficient, with its prediction for the standard deviations of bridge deflection falling within 7.1% of those from the more computationally intensive Probability Density Evolution Method. Furthermore, we found that time-varying parameters have a minimal effect on principal stress directions, validating a scalar application of FOSM with less than 3% error. The analysis shows that uncertainties from creep and shrinkage models increase the 95% quantile of in-plane principal stresses by 0.58MPa, which is approximately 23% of the material’s tensile strength and increases the cracking risk. This research underscores the necessity of using high-fidelity models and probabilistic methods for the reliable design and long-term assessment of complex concrete bridges. Full article

This study experimentally and numerically examines the structural and seismic performance of recycled solid-brick masonry infills and load-bearing walls constructed from demolition materials. Solid bricks recovered from demolished structures were reused as infill in reinforced concrete (RC) frames and as standalone walls. Five full-scale panels, bare, 50% infilled, and 100% infilled frames, were tested under diagonal compression in accordance with ASTM E519-17, simulating in-plane seismic loading. Results showed that fully infilled frames exhibited a 149% increase in diagonal shear strength but a 40% reduction in ductility relative to the bare frame, indicating a trade-off between stiffness and deformation capacity. Finite element simulations using the Concrete Damaged Plasticity (CDP) model reproduced the experimental load–displacement curves with close agreement (within 6–8% in peak load) and captured the main failure patterns. Reusing cleaned demolition bricks reduces the demand for new fired bricks and helps divert construction waste from landfill, contributing to sustainable and circular construction. The findings confirm the potential of recycled masonry for low-carbon and seismic-resilient construction, provided that ductility limitations are appropriately addressed in design. Full article

To meet the increasing demands for structural lightweighting in electric vehicles (EVs), carbon fiber reinforced plastic (CFRP) has been gradually introduced to reduce weight and enhance passenger safety in automotive engineering. The battery-pack enclosure is a key structural component for EVs, as it significantly influences the driving distance, safety, and road handling of EVs. This study presents a top-down design approach and topology optimization for a lightweight CFRP battery pack enclosure reinforced with cross-shaped stiffeners. The main objective is to develop an efficient composite enclosure that meets performance targets while accommodating the demands of cost-effective mass production. The composite battery pack enclosure was fabricated using the compression molding process. Topology optimization was carried out in the preliminary design stage on the structural shape and geometric parameters following a top-down design approach. Experimental tests recorded maximum deformations of 0.56 mm and 10.33 mm under in-plane and lateral loads, respectively. The final prototype product achieved a total mass of 4.78 kg with a rapid curing cycle of 10–15 min. In conclusion, a lightweight composite battery-pack enclosure with cross-shaped stiffeners was successfully manufactured, integrating a top-down design approach with topology optimization. This study demonstrates an effective design approach to achieving an optimal balance of lightweight, cost-effectiveness, and production efficiency for EV battery-pack enclosures. Full article

There has been significant interest in deploying unmanned aerial vehicles (UAVs) for their ability to perform precise and rapid remote mapping and inspection of critical environmental assets for structural health monitoring. This case study investigates the use of UAV-based LiDAR and photogrammetry at Melbourne Water’s Western Treatment Plant (WTP) to routinely monitor high-density polyethylene floating covers on anaerobic lagoons. The proposed approach integrates LiDAR and photogrammetry data to enhance the accuracy and efficiency of generating digital elevation models (DEMs) and orthomosaics by leveraging the strengths of both methods. Specifically, the photogrammetric images were orthorectified onto LiDAR-derived DEMs as the projection plane to construct the corresponding orthomosaic. This method captures precise elevation points directly from LiDAR, forming a robust foundation dataset for DEM construction. This streamlines the workflow without compromising detail, as it eliminates the need for time-intensive photogrammetry processes, such as dense cloud and depth map generation. This integration accelerates dataset production by up to four times compared to photogrammetry alone, while achieving centimetre-level accuracy. The LiDAR-derived DEM achieved higher elevation accuracy with a root mean square error (RMSE) of 56.1 mm, while the photogrammetry-derived DEM achieved higher in-plane accuracy with an RMSE of up to 35.4 mm. An analysis of cover deformation revealed that the floating cover had elevated rapidly within the first two years post-installation before showing lateral displacement around the sixth year, which was also evident from a significant increase in wrinkling. This approach delivers valuable insights into cover condition that, in turn, clarifies scum accumulation and movement, thereby enhancing structural integrity management and supporting environmental sustainability at WTP by safeguarding methane-rich biogas for renewable-energy generation and controlling odours. The findings support the ongoing collaborative industry research between Monash University and Melbourne Water, aimed at achieving comprehensive structural and prognostic health assessments of these high-value assets. Full article

This work aims to investigate the buckling and post-buckling behaviour of wood-based sandwich structures with and without a manufacturing defect, under compressive loading. The specimens were made by gluing birch veneers to a balsa wood core. The defect consisted of a central zone where glue was lacking between the skin and the core. A compression load was applied to the plate using the VERTEX test rig, with the plate placed on the upper surface of a rectangular box and bolted at its borders. The upper surface of the plate was monitored using optical and infrared cameras. The stereo digital image correlation method was used to capture the in-plane and out-of-plane deformations of the specimen, and to calculate the strains and stresses. The infrared camera enabled the failure scenario to be identified. The buckling behaviour of pristine specimens showed small local debonding in the post-buckling range, which was not detrimental to overall performance. In the presence of a manufacturing defect, the decrease in buckling load was only about 15%, but final failure occurred at lower compressive loads. Full article

This study reviews existing research on the effects of the interaction between in-plane (IP) and out-of-plane (OOP) behaviors on the seismic response of non-framed unreinforced masonry (URM) structures. During earthquakes, masonry buildings exhibit complex behaviors. First, walls may experience simultaneous IP and OOP actions, or pre-existing IP and OOP damage, deformation, or loads that can alter their unidirectional IP or OOP seismic response. Second, the IP and OOP action of one wall can affect the behavior of its intersecting walls. However, the effects of these behaviors, referred to as “direct IP-OOP interactions” and “Flange effects”, respectively, are often disregarded in design and assessment provisions. To address this gap, this study explores findings from experimental and numerical research conducted at the wall level currently available in the literature, identifying the nature of these interaction effects and the key parameters that affect their extent. The available body of work includes only a few experimental studies on interaction effects, whereas numerical investigations are more extensive. However, most numerical studies focus on how OOP pre-damage/deformation influences the IP behaviors (OOP/IP interactions) and the role of flanges in IP response (F/IP interactions), leaving significant gaps in understanding the effects of IP pre-damage/deformation on the OOP response (IP/OOP interactions) and the OOP response in the presence of flanges (F/OOP interactions). Among the parameters studied, boundary conditions, wall height-to-length aspect ratio, and vertical overburden are found to have the most significant influence on interaction effects because of their relevance for the IP and OOP failure mechanisms. Other parameters, such as the restriction of top uplift, the presence of openings, or changes in slenderness ratio, are not comprehensively studied, and the available data are insufficient for definitive conclusions. Methodologies available in the literature for extrapolating the findings observed at the wall level to building-level analyses are reviewed. The current predictive equations primarily address the effects of OOP pre-load and Flange effects on IP response. Furthermore, only a few macro-element models are proposed for cost-effective, large-scale building simulations. To bridge these gaps, future research must expand experimental investigations, develop more comprehensive design and assessment equations, and refine numerical modeling techniques for building-level applications. Full article

A rotating imperfect ring resonator of the gyroscope is modeled by a rotating thin ring with evenly distributed point masses. The free response of the rotating ring structure at constant speed is investigated, including the steady elastic deformation and wave response. The dynamic equations are formulated by using Hamilton’s principle in the ground-fixed coordinates. The coordinate transformation is applied to facilitate the solution of the steady deformation, and the displacements and tangential tension for the deformation are calculated by the perturbation method. Employing Galerkin’s method, the governing equation of the free vibration is casted in matrix differential operator form after the separation of the real and imaginary parts with the inextensional assumption. The natural frequencies are calculated through the eigenvalue analysis, and the numerical results are obtained. The effects of the point masses on the natural frequencies of the forward and backward traveling wave curves of different orders are discussed, especially on the measurement accuracy of gyroscopes for different cases. In the ground-fixed coordinates, the frequency splitting results in a crosspoint of the natural frequencies of the forward and backward traveling waves. The finite element method is applied to demonstrate the validity and accuracy of the model. Full article

The mechanics of an elastic sheet reinforced with fiber mesh is investigated when undergoing bilateral in-plane bending and stretching. The strain energy of FRC is formulated by accounting for the matrix strain energy contribution and the fiber network deformations of extension, flexure, and torsion, where the strain energy potential of the matrix material is characterized via the Mooney–Rivlin strain energy model and the fiber kinematics is computed via the first and second gradient of deformations. By applying the variational principle on the strain energy of FRC, the Euler–Lagrange equilibrium equations are derived and then solved numerically. The theoretical results highlight the matrix and meshwork deformations of FRC subjected to bilateral bending and stretching simultaneously, and it is found that the interaction between bilateral extension and bending manipulates the matrix and network deformation. It is theoretically observed that the transverse Lagrange strain peaks near the bilateral boundary while the longitudinal strain is intensified inside the FRC domain. The continuum model further demonstrates the bidirectional mesh network deformations in the case of plain woven, from which the extension and flexure kinematics of fiber units are illustrated to examine the effects of fiber unit deformations on the overall deformations of the fiber network. To reduce the observed matrix-network dislocation in the case of plain network reinforcement, the pantographic network reinforcement is investigated, suggesting that the bilateral stretch results in the reduced intersection angle at the mesh joints in the FRC domain. For validation of the continuum model, the obtained results are cross-examined with the existing experimental results depicting the failure mode of conventional fiber-reinforced composites to demonstrate the practical utility of the proposed model. Full article