Search Results (300)

The present paper proposes a three-dimensional (3D) spherical shell model for the magneto-electro-elastic (MEE) free vibration analysis of simply supported multilayered smart shells. A mixed curvilinear orthogonal reference system is used to write the unified 3D governing equations for cylinders, cylindrical panels and spherical shells. The closed-form solution of the problem is performed considering Navier harmonic forms in the in-plane directions and the exponential matrix method in the thickness direction. A layerwise approach is possible, considering the interlaminar continuity conditions for displacements, electric and magnetic potentials, transverse shear/normal stresses, transverse normal magnetic induction and transverse normal electric displacement. Some preliminary cases are proposed to validate the present 3D MEE free vibration model for several curvatures, materials, thickness values and vibration modes. Then, new benchmarks are proposed in order to discuss possible effects in multilayered MEE curved smart structures. In the new benchmarks, first, three circular frequencies for several half-wave number couples and for different thickness ratios are proposed. Thickness vibration modes are shown in terms of displacements, stresses, electric displacement and magnetic induction along the thickness direction. These new benchmarks are useful to understand the free vibration behavior of MEE curved smart structures, and they can be used as reference for researchers interested in the development of of 2D/3D MEE models. 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 propagation of interface acoustic waves (IAWs) along rotated YX-LiNbO₃/SU-8/ZX-Si structures is theoretically investigated to identify the Y-rotation angles that support the efficient propagation of low-loss modes guided along the structure’s interface. A three-dimensional finite element analysis was performed to simulate IAW propagation in the layered structure and to optimize design parameters, specifically the thicknesses of the platinum (Pt) interdigital transducers (IDTs) and the SU-8 adhesive layer. The simulations revealed the existence of two types of IAWs travelling at different velocities under specific Y-rotated cuts of the LiNbO₃ half-space. These IAWs are faster than the surface acoustic wave (SAW) and slower than the leaky SAW (LSAW) propagating on the surface of the bare LiNbO₃ half-space. The mechanical displacement fields of both IAWs exhibit a rapid decay to zero within a few wavelengths from the LiNbO₃ surface. The piezoelectric coupling coefficients of the IAWs were found to be as high as approximately 7% and 31%, depending on the Y-rotation angle. The theoretical results were experimentally validated by measuring the velocities of the SAW and LSAW on a bare 90° YX-LiNbO₃ substrate, and the velocities of the IAWs in a 90° YX-LiNbO₃/SU-8/Si structure featuring 330 nm thick Pt IDTs, a 200 µm wavelength, and a 15 µm thick SU-8 layer. The experimental data showed good agreement with the theoretical predictions. These combined theoretical and experimental findings establish design principles for exciting two interface waves with elliptical and quasi-shear polarization, offering enhanced flexibility for fluidic manipulation and the integration of sensing functionalities. Full article

Flat slab structures are extensively utilized in modern construction owing to their efficient load transfer mechanisms and optimized space utilization. Nevertheless, the persistent issue of brittle punching shear failure at connection zones continues to pose significant engineering challenges. This study proposes an innovative cross-shaped steel-reinforced concrete (SRC) column–slab connection. Through combining test and numerical analyses, the failure mechanisms and performance control principles are systematically analyzed. A refined finite element model incorporating material nonlinearity, geometric characteristics, and interface effects is developed, demonstrating less than 3% error upon test validation. Using the validated model, the influence of key parameters—including concrete strength (C30–C60), reinforcement ratio (ρ = 0.65–1.77%), shear span–depth ratio (λ = 3–6), and limb height-to-thickness ratio (c₁/c₂ = 2–4)—on the punching shear behavior is thoroughly investigated. The results demonstrate that increasing concrete strength synergistically improves both punching shear capacity (by up to 49%) and ductility (by 33%). A critical reinforcement ratio threshold (0.8–1.2%) is identified. When exceeding this range, the punching shear capacity increases by 12%, but reduces ductility by 34%. Additionally, adjusting the shear span–depth ratio enables controlled failure mode transitions and a 24% reduction in punching shear capacity, as well as a 133% increase in displacement capacity. These results offer theoretical support for the design and promotion of this novel structural system. Full article

This paper focuses on identifying temperature-compensated Y-cuts (using a Cartesian coordinate system) in a piezoelectric α-GeO₂ single crystal, which is isostructural–quartz α-SiO₂. The study aims to minimize the frequency drift of the thickness shear mode by analyzing the resonant frequency’s first- and second-order temperature coefficients T_f⁽¹⁾ and T_f⁽²⁾. To obtain these, the first-order, T_Cij⁽¹⁾, and second-order, T_Cij⁽²⁾, temperature coefficients of the elastic constant, C_ij, previously obtained from room temperature up to 900 °C, were calculated. Upon heating, the thermal behavior of the elastic constants indicated that some, such as C₁₁ and C₃₃, are stable over a range of temperatures, while others, such as C₄₄ and C₆₆, increase with the temperature. This paper also explores a family of singly and doubly rotated Y-cuts of α-GeO₂, revealing cuts with a potential application for temperature compensation and/or linear dependence over the temperature range. The results are compared with those of the well-known piezoelectric isomorph material α-SiO₂. The findings highlight that α-GeO₂ is a promising material for piezoelectric devices in high-temperature environments, outperforming α-SiO₂ (α-quartz), which is limited by a solid–solid phase transition at 573 °C. Full article

This study presents a high-order shear deformation theory (HSDT)-based model for evaluating the energy harvesting performance of functionally graded material (FGM) beams integrated with a piezoelectric layer and subjected to a moving concentrated load at constant velocity. The governing equations are derived using Hamilton’s principle, and the dynamic response is obtained through the State Function Method with trigonometric mode shapes. The output voltage and harvested power are calculated based on piezoelectric constitutive relations. A comparative analysis with homogeneous isotropic beams demonstrates that HSDT yields more accurate predictions than the Classical Beam Theory (CBT), especially for thick beams; for instance, at a span-to-thickness ratio of h/L = 12.5, HSDT predicts increases of approximately 6%, 7%, and 12% in displacement, voltage, and harvested power, respectively, compared to CBT. Parametric studies further reveal that increasing the load velocity significantly enhances the strain rate in the piezoelectric layer, resulting in higher voltage and power output, with the latter exhibiting quadratic growth. Moreover, increasing the material gradation index n reduces the beam’s effective stiffness, which amplifies vibration amplitudes and improves energy conversion efficiency. These findings underscore the importance of incorporating shear deformation and material gradation effects in the design and optimization of piezoelectric energy harvesting systems using FGM beams subjected to dynamic loading. Full article

This study investigates the in-plane shear behavior of solid brick masonry walls, both unreinforced and retrofitted using Reinforced Khorasan Jacketing (RHJ), a traditional pozzolanic mortar technique rooted in Iranian and Ottoman architecture. Six one-block-thick English bond masonry walls were tested in three configurations: unreinforced with Horasan plaster (Group I), reinforced with steel mesh aligned to wall edges (Group II), and reinforced with mesh aligned diagonally (Group III). All the walls were plastered with 3.5 cm of Horasan mortar and tested after 18 months using diagonal compression, with load-displacement data recorded. A detailed 3D micro-modeling approach was employed in finite element simulations, with bricks and mortar modeled separately. The Horasan mortar was represented using an elastoplastic Mohr-Coulomb model with a custom softening law (parabolic-to-exponential), calibrated via inverse parameter fitting using the Nelder-Mead algorithm. The numerical predictions closely matched the experimental data. Reinforcement improved the shear strength significantly: Group II showed a 1.8 times increase, and Group III up to 2.7 times. Ductility, measured as post-peak deformation capacity, increased by factors of two (parallel) and three (diagonal). These enhancements transformed the brittle failure mode into a more ductile, energy-absorbing behavior. RHJ is shown to be a compatible, effective retrofit solution for historic masonry structures. Full article

This study investigates the deformation characteristics and base stability of a circular diaphragm wall support system (external diameter: 90 m, wall thickness: 1.5 m) with pit bottom reinforcement for the South Anchorage deep foundation pit of the Zhangjinggao Yangtze River Bridge, which uses layered and partitioned top-down excavation combined with lining construction. Through field monitoring (deep horizontal displacement of the diaphragm wall, vertical displacement at the wall top, and earth pressure) and numerical simulations (PLAXIS Strength Reduction Method), we systematically analyzed the deformation evolution and failure mechanisms during construction. The results indicate the following: (1) Under the synergistic effect of the circular diaphragm wall, lining, and pit bottom reinforcement, the maximum horizontal displacement at the wall top was less than 30 mm and the vertical displacement was 0.04%H, both significantly below code-specified thresholds, verifying the effectiveness of the support system and pit bottom reinforcement. (2) Earth pressure exhibited a “decrease-then-increase” trend during the excavation proceeds. High-pressure jet grouting pile reinforcement at the pit base significantly enhanced basal constraints, leading to earth pressure below the Rankine active limit during intermediate stages and converging toward theoretical values as deformation progressed. (3) Without reinforcement, hydraulic uplift failure manifested as sand layer suspension and soil shear. After reinforcement, failure modes shifted to basal uplift and wall-external soil sliding, demonstrating that high-pressure jet grouting pile reinforcement had positive contribution basal heave stability by improving soil shear strength. (4) Improved stability verification methods for anti-heave and anti-hydraulic-uplift were proposed, incorporating soil shear strength contributions to overcome the underestimation of reinforcement effects in traditional pressure equilibrium and Terzaghi bearing capacity models. This study provides theoretical and practical references for similar deep foundation pit projects and offers systematic solutions for the safety design and deformation characteristics of circular diaphragm walls with pit bottom reinforcement. Full article

Understanding the formability limits of thin-walled tubes with square cross-sections and L-section profiles is crucial for improving manufacturing efficiency and ensuring structural reliability in industries such as automotive and aerospace. Unlike the usually studied circular tubes, square tubes and L-section profiles geometries present unique deformation and fracture behaviours that require specific analysis. To address this gap, this research establishes a novel methodology combining digital image correlation (DIC) with a time-dependent approach and precise thickness measurements, enabling accurate strain measurements essential to the onset of necking and fracture strain identification. Two experimental tests under different forming conditions allowed capturing a distinct range of strain paths leading to failure. This approach allowed the determination of the forming limit points associated with necking and the fracture forming lines associated with crack opening by tension (mode I) and by in-plane shear (mode II). The findings highlight the strong influence of geometry on the fracture mechanisms and provide valuable data for optimizing tube-forming processes for square tubes and L-section profiles, ultimately enhancing the design and performance of lightweight structural components. Full article

This study aims to improve the shear performance of reinforced concrete (RC) beams by utilizing the favorable tensile and shear deformation capabilities of high-strength, high-toughness epoxy mortar. This study investigates the effect of reinforcement layer thickness on the shear failure modes, bearing capacity, and deformation capacity of beams through static tests on three specimens reinforced with thin layers of high-strength, high-toughness epoxy mortar and one unreinforced beam. The results show that reinforcing RC beams with thin layers of high-strength, high-toughness epoxy mortar can significantly enhance its shear bearing capacity and deformation capacity. The reinforcement layer of epoxy mortar can partially exert the shear resistance provided by the stirrups. The thicker the reinforcement layer, the more significant the improvement in the shear bearing capacity and deformation capacity of the strengthened beam. The epoxy mortar layer bonds well with the concrete, but delamination between the cover concrete and the core concrete leads to failure of the reinforcement layer, meaning that shear bearing capacity does not increase linearly with the thickness of the epoxy mortar layer. Based on the experimental results, a shear bearing capacity calculation formula for RC beams reinforced with thin layers of high-strength, high-toughness epoxy mortar is proposed, which matches the experimental results well. Full article

This study assesses the punching shear characteristics of ultra-high-performance concrete (UHPC) slabs in two phases. The initial phase involved experimental tests to determine the critical thickness differentiating punching shear failure and flexural failure modes. Subsequently, the second phase further explored the punching shear behavior of UHPC slabs by analyzing various key parameters. The experimental findings indicated that as the thickness of the slabs increased, the punching shear capacity exhibited nearly linear enhancement, surpassing the improvement seen in bending capacity. Thus, a critical thickness of at least 100 mm was identified as the threshold distinguishing punching shear failure from flexural failure. Additionally, an increase in slab thickness significantly elevated the cracking load of the UHPC slabs. While a higher reinforcement ratio of 3.5% slightly increased the first cracking load, it greatly enhanced the ultimate capacity. The addition of steel fibers also contributed to improvements in both cracking and ultimate loads, albeit to a limited extent. The use of a granite powder substitute, comprising 10% of the mass of silica fume, had minimal impact on the punching shear capacity of the UHPC slabs. Finally, a comparison is drawn between the experimental results for punching shear capacity and those obtained from various theoretical models. This comparison highlights significant discrepancies in the results, stemming from the differing parameters employed in the proposed theoretical models. Among the prediction models, the JSCE model provided the most balanced and conservatively accurate estimation of punching shear capacity, effectively incorporating the effects of slab thickness, reinforcement ratio, and fiber content, thus highlighting its potential as a reliable reference for future design recommendations. This information will serve as a valuable reference for future research and practical applications related to UHPC bridge decks and slabs. Full article

The instability of a non-Newtonian dielectric fluid jet of power-law (P-L) type injected when streaming dielectric gas through porous media is examined using electrohydrodynamic (EHD) linear analysis. The interfacial boundary conditions (BCs) are used to derive the dispersion relation for both shear-thinning (s-thin) and shear-thickening (s-thick) fluids. A detailed discussion is outlined on the impact of dimensionless flow parameters. The findings show that jet breakup can be categorized into two instability modes: Rayleigh (RM) and Taylor (TM), respectively. For both fluids, the system in TM is found to be more unstable than that found in RM, and, for s-thick fluids, it is more unstable. For all P-L index values, the system is more unstable if a porous material exists than when it does not. It is demonstrated that the generalized Reynolds number (${Re}_n$), Reynolds number ($Re$), P-L index, dielectric constants, gas-to-liquid density, and viscosity ratios have destabilizing influences; moreover, the Weber number ($We$), electric field (EF), porosity, and permeability of the porous medium have a stabilizing impact. Depending on whether its value is less or more than one, the velocity ratio plays two different roles in stability, and the breakup length and size of P-L fluids are connected to the maximal growth level and the instability range in both modes. Full article

To reduce the cast in place work of concrete and realize the industrial production of a bamboo–concrete composite (BCC), innovative connection systems composed of an assembled bamboo–lightweight concrete composite (ABLCC) structure featuring perforated steel plate connectors are presented for use in engineering structures. This study examined the shear performance of connection systems composed of an assembled BCC structure featuring perforated steel plate connectors based on the design and fabrication of three groups of shear connectors with nine different parameters using bamboo scrimber, lightweight concrete, perforated steel plates, and grout. Push-out tests were conducted on these shear connectors. A linear variable differential transformer (LVDT) and digital image correlation (DIC) were utilized for measurements. The test parameters comprised fabrication techniques (assembled and cast-in-place/CIP) and connector size (steel plate thickness). This study investigated mechanical performance indicators, including the failure mode, load–slip relationship, shear stiffness, and shear capacity of the shear connectors. The experimental results showed that the shear connector failure modes involved concrete spalling near the connectors and deformation of the perforated steel plates. The load–slip curves generally included three stages: high slope linear increase, low slope nonlinear increase, and rapid decrease. The shear capacity and stiffness of the assembled shear connectors were 0.84 times and 2.46 times those of the CIP connectors, respectively. The stiffness of the 4 mm steel plate connectors increased by 42% compared to the 2 mm steel plate connectors. Analysis showed that the shear capacity of the BBC primarily consisted of four aspects: the end bearing force of the steel plate, contact friction, and forces due to the influence of tenon columns and the reinforcing impact of through-rebars. This study proposes a simple and suitable formula for obtaining the shear capacity of perforated steel plate connectors in the BCC structure, with the analytical values being in good agreement with the test results. Full article

This study investigated the effectiveness of Tooth Primer and cleaning agents in removing saliva contamination from zirconia as assessed using shear bond strength (SBS). A total of 175 rectangular specimens, 10 mm in diameter and 6 mm in thickness, were randomly divided into seven groups (n = 25 each): group 1, no saliva contamination (control); group 2, saliva-contaminated and not rinsed; group 3, saliva-contaminated and rinsed; group 4, saliva-contaminated, Ivoclean-treated, and rinsed; group 5, saliva-contaminated, Katana Cleaner-treated, and rinsed; group 6, saliva-contaminated, Tooth Primer-treated, and rinsed; and group 7, saliva-contaminated, Tooth Primer-treated, and not rinsed. All zirconia specimens from groups 1–7 were bonded to composite rods with Panavia SA Luting Multi cement. The bonded specimens were subjected to the SBS test using a universal testing machine. To assess the type of failure, the debonded surface was evaluated using a stereomicroscope. The SBS data were analyzed using one-way ANOVA with Tukey’s post-test. The SBS values of groups 2 (0.90 ± 0.20 MPa) and 3 (1.35 ± 0.43 MPa) were significantly lower compared with the other groups (p = 0.00). The SBS value of zirconia decontamination using Ivoclean in group 4 (18.51 ± 3.01 MPa) was significantly lower than that of the control group (22.24 ± 2.37 MPa) (p = 0.00). However, the SBS values of groups 5 (20.92 ± 2.63 MPa), 6 (21.43 ± 2.81 MPa), and 7 (20.87 ± 2.35 MPa) did not significantly differ compared with the control group (22.24 ± 2.37 MPa) (p = 0.369, p = 0.861, p = 0.327, respectively). Moreover, SBS values did not significantly differ among groups 5 to 7 (p = 0.984, p = 1.00, p = 0.976, respectively). Regarding failure mode, groups 2 and 3 exclusively experienced adhesive failures. Groups 1, 4, 5, 6, and 7 exhibited adhesive and mixed failures. In conclusion, Ivoclean, Katana Cleaner, and Tooth Primer effectively mitigated the adverse effects of saliva contamination on the resin cement–zirconia interface. Furthermore, Tooth Primer can be used as a cleaner for saliva-contaminated zirconia surfaces, with or without rinsing. Full article

Corrugated steel plate shear walls (CSPSWs) exhibit excellent energy dissipation capacity and lateral resistance performance due to their unique “accordion structure”, making them a highly promising seismic component in prefabricated buildings. The assembled CSPSWs utilize bolted connections on both sides, which align with the energy-saving and emission-reduction trends of prefabricated construction. Compared to traditional welded connections, this method reduces the impact on frame columns during seismic deformation and allows for easier post-damage replacement. Through experimental and finite element analysis, this study systematically investigates the lateral mechanical behavior of assembled CSPSWs and compares them with flat steel plate shear walls (FSPSWs), revealing the stress mechanisms and failure modes of corrugated structures. Additionally, parametric analysis quantifies the influence of plate thickness, width/height ratio, and wave height on structural performance. Experimental results demonstrate that CSPSWs significantly outperform FSPSWs in out-of-plane displacement resistance and energy dissipation efficiency. Parametric analysis indicates that increasing plate thickness and width/height ratio enhances energy dissipation, while increasing wave height negatively affects energy dissipation capacity. This research provides theoretical support for the optimal design and engineering application of assembled corrugated steel plate shear walls. Full article