Search Results (201)

Enclosed reinforced concrete structures subjected to internal blast loading represent a critical safety concern in infrastructure applications where detonations may occur within confined spaces. Although circular cross-sections have been widely adopted for blast-resistant containment structures, systematic quantitative comparisons of internal blast responses between circular and square enclosed configurations under progressive charge weight conditions remain limited. LS-DYNA finite element simulations are conducted under four trinitrotoluene (TNT) charge weight conditions ranging from 1200 to 2500 kg, and the failure-inducing blast load is defined as the minimum charge weight at which continuous concrete element deletion first occurs in the roof or side-wall region. In this study, the failure-inducing blast load is interpreted as an erosion-based comparative indicator under the adopted empirical blast-loading framework rather than as an absolute real-world confined-blast failure threshold. The roof failure-inducing blast load is identical for both structures at 1200 kg, whereas the side-wall failure-inducing blast loads are 2500 kg for the circular structure and 1500 kg for the square structure, indicating approximately 67% higher side-wall blast resistance in the circular structure. This difference is attributed to the membrane action of the curved wall, which redistributes internal blast-induced lateral pressure along the circumferential direction and limits out-of-plane deformation. Under the 2500-kg condition, the peak side-wall displacement of the square structure is 161.6% higher than that of the circular structure, whereas its peak roof displacement is 33.3% lower. Axial strains at all reinforcement locations remain within the elastic range, confirming that concrete damage is governed by the low tensile capacity of concrete rather than reinforcement yielding. Full article

Single-story unreinforced masonry rural houses along the Tanlu Earthquake Belt in Anhui Province are generally constructed without ring beams and tie columns, resulting in poor structural integrity and low seismic performance. This paper proposes a convenient single-sided High-Ductility Concrete Strip (HDCS) retrofitting method. Two 1:2 scaled test specimens, namely the unretrofitted model M1 and HDCS single-side retrofitted model M2, were fabricated for shaking table tests. Systematic analyses were carried out based on white noise sweep tests, failure modes, acceleration responses and inter-story displacement responses. The test results show that HDCS possesses excellent tensile capacity, which forms continuous confinement at wall joints and openings to boost structural stiffness and greatly restrain post-seismic stiffness degradation, as well as achieve more uniform structural deformation distribution. Under strong seismic excitations, the unretrofitted model suffers severe damage, including penetrating diagonal shear cracks and separation between gable walls and lower walls. In contrast, damage of the retrofitted model is concentrated within the HDCS overlay, realizing damage redistribution and preventing brittle failure of the main masonry. HDCS stabilizes the distribution of acceleration amplification factors and restrains wall rocking and stress concentration around openings. Although single-sided strengthening induces slight out-of-plane effects, its adverse influence is acceptable. Full article

In response to engineering issues such as cracking and waterproofing failure caused by lateral displacement of the main structural layers when autoclaved-aerated-concrete (AAC) exterior wall panels are applied in the typhoon-prone areas of Southeastern Zhejiang, a form of embedded connection structure is proposed. This structure combines anchoring reliability with deformation adaptability. Based on the typhoon wind load in the Kanmen area of Yuhuan County, Taizhou City, Zhejiang Province, as the design basis, AAC exterior wall panel frame test specimens are designed and fabricated. Out-of-plane wind resistance static load tests are conducted. The deflection and strain patterns of the test specimens are analyzed to verify the wind-resistance bearing capacity and deformation coordination ability of this connection form. The test results indicate that under the standard value of typhoon wind load of 5.47 kN/m², the maximum deflection of the test specimen is 2.155 mm, with a deflection ratio of 7.98 × 10⁻⁴, which is far below the specification limit. The measured maximum tensile and compressive strains does not reach the cracking strain of AAC material, and the component does not exhibit cracking or sudden stiffness changes. Both the out-of-plane wind resistance and deformation coordination capabilities meet the requirements for use in typhoon areas. This study provides solid theoretical support and engineering reference for the application of AAC exterior wall panels in prefabricated buildings in high-wind-pressure areas. Full article

Deployable reflector antennas demand high geometric precision; the Ruze equation directly links surface error to RF gain. Arc-shaped CFRP ribs are vulnerable to thermal deformation, as their curvature converts in-plane expansion into out-of-plane displacement, which symmetric laminates cannot suppress. Classical laminate theory (CLT) underestimates the coefficient of thermal expansion (CTE) of cross-ply laminates by factors of 1.75–2.38 for the laminate configurations investigated in this study, causing up to 79.4% of displacement prediction errors in symmetric designs. Here, we present an asymmetric laminate that overcomes both limitations. The upper skin (nine plies) and lower/web skins (seven plies) from the same prepreg batch create a CTE mismatch (Δα = 6.30 × 10⁻⁷ K⁻¹), activating coupling stiffness to generate a thermal moment opposing curvature-driven displacement. Because both skins share identical batch history, CTE prediction errors cancel through common-mode rejection. Compared with the symmetric design, the asymmetric design achieved a 50.4% reduction in thermal deformation (from 210 µm to 104 µm) and improved FEA accuracy from 79.4% error to 4.8% error under experimental schemes. The method uses only conventional 0/90° prepreg and standard autoclave processing, with the upper-surface ply count as the sole design variable for a given section’s geometry, establishing retained coupling stiffness as a practical route to dimensional stability in curved space structures. Full article

Accurate prediction of welding-induced deformation is essential for dimensional control in large-scale ship block construction. In production design, transverse shrinkage directly governs the cutting allowance and shrinkage margin among various deformation modes. The inherent strain framework is widely used due to its computational efficiency, but the interaction between the implementation of equivalent loads and geometric nonlinearity has not been systematically investigated. This study evaluates two conventional loading representations: the equivalent nodal force method and the equivalent thermal load method, under both linear and geometrically nonlinear analysis formulations. In linear elastic analysis, both representations are equivalent and successfully provide identical, stable in-plane shrinkage predictions because both methods utilize input loads formulated from the same target inherent deformation. However, in shipbuilding practice, a geometrically nonlinear formulation is frequently required to capture large-displacement behaviors or structural instabilities in thin-walled assemblies. When geometric nonlinearity is introduced into these shrinkage predictions, a critical discrepancy emerges depending on the load implementation: the equivalent nodal force method violates the physical basis of shrinkage prediction by introducing unwanted out-of-plane deformation artifacts. This is a numerical artifact arising from the interaction of localized artificial compressive stresses with the stress-dependent geometric stiffness matrix. In contrast, the equivalent thermal load method is robust and always preserves the target in-plane shrinkage without any undesired out-of-plane geometry. Therefore, even though both methods are robust in the linear regime, the equivalent thermal load method is recommended when a geometrically nonlinear formulation is involved to ensure numerical consistency and reliability in production design. Full article

The objective of this study is to recover the transient out-of-plane displacement field of clamped circular plates subjected to blast loading using a single high-speed camera, as a low-cost alternative to stereo Digital Image Correlation (DIC) for the specific class of axisymmetrical structural responses of circular plates. The dynamic response of thin metal plates to blast loading is a fundamental problem in protective structural design, traditionally investigated through DIC. Although it provides full-field displacement measurements with high spatial resolution, it requires stereo camera arrangements, controlled illumination, speckle pattern preparation, and elaborate calibration procedures that significantly increase experimental cost and complexity. This study introduces a monocular optical method applicable to axisymmetrically defined material testing applications, such as the response of circularly supported isotropic plates under a uniform impulsive load, to recover the transient out-of-plane displacement field without using DIC. Clamped circular aluminum plates are subjected to blast loading generated by PG-3 charges of variable mass detonated at the closed end of a shock tube, with the exposed face matching the tube cross-section so as to enforce axisymmetric pressure load. A diametral reference line marked on the rear face of each specimen was recorded by a single high-speed camera, and a perspective correction derived from the axisymmetric deformed geometry was then applied to reconstruct the time-resolved displacement profile along the diameter. The permanent post-test deformed shape of each plate was subsequently digitized through 3D scanning and used as ground truth to validate the optical reconstruction. The reconstructed profiles closely matched the scans: for the conventional responses the root-mean-square error was 1.251 mm with a normalized mean residual of 6.57% (Case A) and 1.793 mm (9.20%, Case B), while for the anomalous counterintuitive response it was 1.043 mm (14.93%, Case C). Symmetry can thus be exploited as an active measurement principle to obtain quantitative blast-response data with substantially reduced experimental burden and without specialized stereo-optical instrumentation. Full article

Conventional masonry infill walls can significantly alter the seismic response of framed buildings and often produce damage patterns incompatible with resilience-based seismic design. Dry-jointed sliding masonry wall systems have therefore emerged as deformation-tolerant alternatives that accommodate drift through controlled interface motion rather than damage accumulation. This study investigates the sequential in-plane (IP) and out-of-plane (OOP) behavior of such systems considering wall thickness, openings, and boundary detailing. Six full-scale specimens were tested, including thick- and thin-wall reference specimens, thick-wall specimens with window openings, and thin-wall specimens with door openings. IP performance was evaluated using global hysteretic and energy-based response parameters, whereas OOP behavior was assessed through load–displacement response, an equivalent acceleration index, and selected image-based displacement fields. The results show that IP drift was mainly accommodated through distributed sliding along horizontal interfaces and local block rotation, without diagonal compression strut formation or brittle cracking, even at drift ratios up to approximately 3.5%. Wall thickness improved IP strength, stiffness, shear resistance, and cumulative energy dissipation, while openings mainly affected deformation compatibility and load-transfer continuity. Under OOP loading, wall thickness and boundary continuity increased stiffness and capacity while enabling resistance mobilization at smaller displacement levels. As inertia-based comparison indicators, boundary-enhanced thick- and thin-wall specimens reached equivalent acceleration capacities of 3.41 g and 1.64 g, respectively. Overall, the system reduced IP damage accumulation, but adequate OOP stability requires appropriate wall thickness, unit geometry, and boundary detailing. Full article

Precision tilt stages capable of high angular resolution and low cross-axis coupling are essential for applications such as free-space optical communication, adaptive optics, and micro/nano-positioning. In this study, a two-degree-of-freedom compliant tilt stage based on differential actuation of positive and negative Poisson’s ratio folded-beam structures is proposed. The stage incorporates four circumferential compliant motion units, each consisting of a W-shaped positive Poisson’s ratio folded beam, an M-shaped negative Poisson’s ratio folded beam, a lever amplification mechanism, and compliant decoupling leaf springs. By exploiting the opposite out-of-plane deformation tendencies of the two folded-beam types under identical input forces, a push–pull differential driving effect is generated, enabling independent tilting motion about two orthogonal axes with enhanced angular output. The lever amplification mechanisms enlarge the small displacement of the piezoelectric actuators, while the decoupling leaf springs suppress parasitic motion and reduce cross-axis coupling. A static analytical model is established based on compliance analysis and force–moment equilibrium. The model predictions are validated through finite element analysis, with errors of 4.77% and 4.80% for the two axes, respectively. Experimental results obtained from a stereolithography-fabricated prototype demonstrate maximum tilt angles of 9.19 mrad and 8.80 mrad about the x- and y-axes under a 150 V driving voltage, while the corresponding coupling angles are only 0.043 mrad and 0.040 mrad, yielding coupling ratios below 0.5%. The proposed design achieves a favorable combination of compact monolithic structure, effective displacement amplification, and excellent decoupling performance, offering a practical solution for precision optical adjustment, beam steering, and micro/nano-positioning systems. Full article

Strong chiral responses in planar dielectric metasurfaces are important for polarization-selective nanophotonic devices, but achieving large and reversible circular dichroism (CD) in simple dielectric structures remains challenging. This work proposes a symmetry-broken silicon metasurface that realizes near-infrared chiral response based on bound states in the continuum (BICs). The unit cell consists of a silicon nanoblock with two through-air grooves. The in-plane displacement of the air grooves breaks the C₂ rotational symmetry and splits the BIC-related polarization singularity into two circularly polarized points (C points) with opposite handedness. By further introducing out-of-plane tilting, one of the C points is shifted to the Г point, enabling spin-selective coupling between normally incident circularly polarized light and the quasi-BIC mode. Reversing the out-of-plane tilt switches the sign of CD, with values reaching −0.98 and 0.98, approaching the theoretical limits of ±1. Under oblique incidence, the structure can also exhibit near-limit CD responses. Finally, by introducing graphene, the structure achieves tunable circular-polarization-selective absorption, with the absorption of CD approaching the theoretical limits of ±0.5 for the coupled system. This work provides a new design idea for compact chiral nanophotonic materials by using symmetry breaking to control spin-selective quasi-BIC coupling and tunable chiral absorption. Full article

Quasi-static ultrasound elastography (USE) is a promising imaging technique for detecting malignancies by assessing tissue stiffness, but its accuracy heavily depends on the quality of radio-frequency (RF) frame pairs used for displacement estimation. A major challenge in quasi-static USE is signal decorrelation, which is primarily caused by out-of-plane motion during manual probe compression, leading to unreliable displacement fields and degraded elastography images. This paper introduces a novel, displacement estimator-agnostic method for assessing RF frame pair quality by measuring the similarity between the measured post-compression RF frame and a warped version of the pre-compression frame generated using the estimated displacement field. The proposed approach employs computationally efficient metrics such as mean squared error (MSE) and correlation, demonstrating robustness against signal decorrelation in both synthetic and clinical datasets. Additionally, we present a method to simulate realistic RF data corruption via controlled out-of-plane displacements, facilitating the development of robust motion-tracking algorithms. Validation using in silico phantoms, tissue-mimicking phantoms and clinical breast cancer and liver cancer cases confirm the method’s efficacy in identifying high-quality frame pairs, significantly improving strain image accuracy. Threshold values of 1.4 and 0.5 were determined for MSE and correlation, respectively, as being effective to differentiate between good vs. bad RF data frame pairs. This work lays the foundation for automated frame selection in USE, enhancing its diagnostic reliability and clinical utility. Full article

The seismic design of spatial joints in long-span concrete-filled steel tube (CFST) arch bridges under complex stresses remains a critical challenge in high-intensity seismic zones. This study investigates the seismic performance and failure mechanisms of CFST spatial KT-type joints, using the Pingnan No. 3 Bridge as a case study. Based on similarity theory, four scaled test specimens were designed. The core variable was the axial compression ratio of the main pipe, while the load on the K-branch served as the parametric variable. Quasi-static tests were conducted under constant static loading on the main pipe and K-branches, coupled with low-cycle cyclic loading on the T-branch. Furthermore, nonlinear finite element analysis (FEA) was performed using Abaqus for cross-validation. The results indicate that the primary failure mode of this joint configuration is the shear-punching failure of the main pipe wall at the T-branch intersection. The load–displacement hysteresis curves exhibit a robust “bow-shaped” profile, indicating substantial plastic energy dissipation capacity. Comparative analysis confirms that hollow steel pipe T-branches offer superior ductility in long-span arch bridges compared to concrete-filled alternatives. By extracting shear stress distribution characteristics from the FEA model to precisely locate the neutral axis, this study proposes a theoretical correction to the ultimate load-carrying capacity calculation model. The derived theoretical values demonstrate good agreement with the experimental results. The relative errors between the calculated and experimental bearing capacities of KT783a, KT783, KT700, and KT607 were 1.99%, 0.23%, 2.26%, and 2.45%, respectively, referring to the T-branch out-of-plane bearing capacity predicted by the proposed formula. The proposed theoretical model provides a reliable quantitative basis for the seismic design and local strengthening of similar spatial joints in long-span CFST arch bridges. Full article

Flexible honeycomb skins offer a promising route for achieving continuous shape adaptation in morphing aircraft. In practical service, however, the skin must simultaneously accommodate large in-plane deformation while maintaining sufficient out-of-plane load-bearing capacity, which poses a fundamental design challenge. To address this trade-off, this study investigates an SMA-based U-shaped honeycomb under combined tensile deformation and aerodynamic pressure. A parametric finite element model incorporating SMA superelasticity is established, and an automated Abaqus–modeFRONTIER framework is developed for multi-objective optimization under dual loading conditions. The curvature radius, parallel-segment length, and middle-beam length are selected as design variables. The optimization objectives are defined as minimizing the maximum local strain under a prescribed tensile displacement and reducing the Z-direction displacement under aerodynamic loading as an indicator of out-of-plane bending resistance. The resulting Pareto front reveals the trade-off between flexibility and load-bearing capacity, and the sensitivities of the key geometric parameters are analyzed. Compared with the initial design, a representative optimized solution reduces the maximum local strain by 58.5% and the Z-direction displacement by 61.3%. These results provide a numerical basis for the design of SMA-based flexible skins for morphing aircraft. Full article

This study comprised an experimental investigation of the in-plane performance of composite floor slabs under out-of-plane effects. Two composite floor slabs were subjected to pure in-plane loading, and in-plane and out-of-plane coupled loading, respectively. The study analyzed crack patterns, failure modes, and load–displacement curves, and evaluated how out-of-plane effects influenced in-plane performance. The test results indicated that both specimens exhibited a typical shear-tension failure mode, forming diagonal shear cracks. The specimen with out-of-plane loading exhibited a trend for lateral development of the shear cracks. The load–displacement curves of the two specimens showed obvious strength degradation, stiffness degradation, and a pinching effect. By comparing the two specimens, it could be observed that at a small out-of-plane displacement angle, the in-plane ultimate bearing capacity of a specimen was not significantly weakened; however, as the out-of-plane displacement continued to increase, the in-plane bearing capacity of the specimen decayed more rapidly. Full article

This study tested quarter-scale adobe masonry walls under monotonic in-plane loading, considering the effect of water content at the foundation–wall interface, fiber type, and openings (i.e., door, window). Seven walls were constructed with unstabilized adobe bricks containing either cut straw or sisal fibers and mud mortar. Gravimetric water content (w_b) at the foundation–wall interface (i.e., wall base) varied by test wall, ranging from 2.4 to 4.9% by dry mass. The walls were instrumented to measure in-plane and out-of-plane displacements and vertical deflections during the load tests. Greater water contents at and near the wall base shifted cracking toward the lower courses and along the foundation–wall interface; however, the peak load capacity did not vary significantly with w_b but was strongly influenced by crack trajectory, including whether cracking diverted into the foundation or propagated rapidly along the foundation–wall interface. Peak loads ranged from 1928 N (433 lb) to 6517 N (1465 lb). Fiber type influenced deformation behavior of the walls, with sisal-brick walls generally developing larger vertical deflections and, in some instances, larger peak in-plane displacements than straw-brick walls. Window and door openings altered crack initiation and propagation by concentrating cracking at opening corners and producing segmented mechanisms, increasing in-plane displacements in some cases, but still sustaining comparatively large peak loads. Full article

The buckling and post-buckling responses of carbon fibre-reinforced polymer (CFRP) structures are strongly affected by geometric imperfections, boundary conditions, and material nonlinearities, making their reliable numerical prediction challenging. This work presents an integrated experimental–numerical investigation of a stiffened CFRP panel subjected to compressive loading, with the aim of improving model validation in instability regimes. The experimental campaign combines full-field measurements obtained through digital image correlation with local strain data from strain gauges, adopting a back-to-back configuration to capture the strain reversal associated with global buckling. The experimental results are compared with nonlinear finite element simulations incorporating intralaminar damage based on Hashin’s failure criteria. A good agreement between the numerical and experimental results is observed in the pre-buckling and early post-buckling regimes. However, increasing discrepancies arise at higher load levels, mainly due to manufacturing imperfections and uncertainties in boundary conditions, which influence the onset and evolution of localized deformation. Statistical indicators are employed to quantitatively assess the correlation between the experimental and numerical responses. The analysis focuses on the key response parameters, including the load–displacement behaviour, out-of-plane displacements, strain evolution, and damage initiation, enabling a comprehensive comparison of experimental and numerical results. The results demonstrate the effectiveness of combining full-field and point-wise measurements for validating numerical models of composite structures. Furthermore, the study highlights the limitations of idealized modelling assumptions and provides insights into the sensitivity of CFRP structures to imperfections in post-buckling and failure regimes. Full article