Search Results (84)

Argillaceous slate (AS) is a typical metamorphic rock with well-developed bedding, widely distributed globally. Its bedding structure significantly impacts slope stability assessment, and the challenges associated with slope anchoring and support arising from bedding characteristics have become a focal point in the engineering field. In this study, with bedding dip angle as the key variable, mechanical tests such as uniaxial compression, triaxial compression, direct shear, and Brazilian splitting tests were conducted on AS. Additionally, field anchoring grouting diffusion tests on AS slopes were carried out. The aim is to investigate the basic mechanical properties of AS and the grout diffusion law under different bedding dip angles. The research results indicate that the bedding dip angle has a remarkable influence on the failure mode, stress–strain curve, and mechanical indices such as compressive strength and elastic modulus of AS specimens. The stress–strain curves in uniaxial and triaxial tests, as well as the stress-displacement curve in the Brazilian splitting test, all undergo four stages: crack closure, elastic deformation, crack propagation, and post-peak failure. As the bedding dip angle increases, the uniaxial and triaxial compressive strengths and elastic modulus first decrease and then increase, while the splitting tensile strength continuously decreases. The consistency of the bedding in AS causes the grout to diffuse in a near-circular pattern on the bedding plane centered around the borehole. Among the factors affecting the diffusion range of the grout, the bedding dip angle and grouting angle have a relatively minor impact, while the grouting pressure has a significant impact. A correct understanding and grasp of the anisotropic characteristics of AS and the anchoring grouting diffusion law are of great significance for slope stability assessment and anchoring design in AS areas. Full article

This study investigates the free vibration behaviors of functionally graded (FGM) plates with a porous structure, resting on a Kerr-type elastic foundation, while accounting for thermal effects and complex material property distributions. Within the framework of higher-order shear deformation theory (HSDT), two novel shape functions are introduced to accurately model transverse shear deformation across the plate thickness without employing shear correction factors. These functions are constructed to satisfy shear stress boundary conditions and capture nonlinear effects induced by material gradation and porosity. A variational formulation is developed to describe the dynamic response of FGM plates in a thermo-mechanical environment, incorporating temperature-dependent material properties and three porosity distributions: uniform, linear, and trigonometric. Numerical solutions are obtained using in-house MATLAB codes, allowing complete control over the formulation and interpretation of the results. The model is validated through detailed comparisons with existing literature, demonstrating high accuracy. The findings reveal that the porosity distribution pattern and gradient intensity significantly influence natural frequencies and mode shapes. The trigonometric porosity distribution exhibits favorable dynamic performance due to preserved stiffness in the surface regions. Additionally, the Kerr-type elastic foundation enables fine tuning of the dynamic response, depending on its specific parameters. The proposed approach provides a reliable and efficient tool for analyzing FGM structures under complex loading conditions and lays the groundwork for future extensions involving nonlinear, time-dependent, and multiphysics analyses. Full article

T-bar penetrometers have been widely used to measure strength parameters of marine clay in laboratory and in situ tests. However, using the deep resistance factor derived from full-flow conditions to evaluate the undrained shear strength of shallow clay layers may lead to significant underestimation. Furthermore, the deep resistance factor is inherently influenced by the strain-softening behavior of clay rather than maintaining the constant value (typically 10.5) as conventionally assumed in practice. To address this issue, large-deformation finite element (LDFE) simulations incorporating an advanced exponential strain-softening constitutive model were performed to replicate the full T-bar penetration process—from shallow embedment to deeper depths below the mudline. A series of parametric studies were conducted to examine the influence of key parameters on the resistance factor and the associated failure mechanisms during penetration. Based on numerical results, empirical formulas were derived to predict critical penetration depths for both trapped cavity formation and full-flow mechanism initiation. For penetration depths shallower than the full-flow depth, an expression for the softening correction factor was developed to calibrate the shallow resistance factor. Finally, combined with global optimization algorithms, a computer-aided back-analysis procedure was established to estimate strain-softening parameters using resistance-penetration curves from initial penetration tests in marine clay. The reliability of the back-analysis procedure was validated through extensive comparisons with a series of numerical simulation results. This procedure can be applied to the interpretation of T-bar in situ test results in soft marine clay, enabling the evaluation of its strain-softening behavior. Full article

The current study demonstrates the buckling properties of composite laminates reinforced with MWCNT fillers using a novel higher-order shear and normal deformation theory (HSNDT), which considers the effect of thickness in its mathematical formulation. The hybrid HSNDT combines polynomial and hyperbolic functions that ensure the parabolic shear stress profile and zero shear stress boundary condition at the upper and lower surface of the plate, hence removing the need for a shear correction factor. The plate is made up of carbon fiber bounded together with polymer resin matrix reinforced with MWCNT fibers. The mechanical properties are homogenized by a Halpin–Tsai scheme. The MATLAB R2019a code was developed in-house for a finite element model using C⁰ continuity nine-node Lagrangian isoparametric shape functions. The geometric nonlinear and linear stiffness matrices are derived using the principle of virtual work. The solution of the eigenvalue problem enables estimation of the critical buckling loads. A convergence study was carried out and model efficiency was corroborated with the existing literature. The model contains only seven degrees of freedom, which significantly reduces computation time, facilitating the comprehensive parametric studies for the buckling stability of the plate. Full article

This study investigates the impact of nonlinear constitutive models on one-dimensional seismic site response analysis (SRA) for soft, reclaimed soil deposits in Saemangeum, South Korea. Two widely used models, MKZ and GQ/H, were applied to three representative soil profiles using the DEEPSOIL program. Ground motions were scaled to bedrock peak ground accelerations (PGAs) corresponding to annual return periods (ARPs) of 1000, 2400, and 4800 years. Seismic response metrics include the ratio of GQ/H to MKZ shear strain, effective PGA (EPGA), and short- and long-term amplification factors (F_a and F_v). The results highlight the critical role of the site-to-motion period ratio (T_g/T_m) in controlling seismic behavior. Compared to the MKZ, the GQ/H model, which features strength correction and improved stiffness retention, predicts lower shear strains and higher surface spectral accelerations, particularly under strong shaking and shallow conditions. Model differences are most pronounced at low T_g/T_m values, where MKZ tends to underestimate amplification and overestimate strain due to its limited ability to reflect site-specific shear strength. Relative to code-based amplification factors, the GQ/H model yields lower short-term estimates, reflecting the disparity between stiff inland reference sites and the soft reclaimed conditions at Saemangeum. These findings emphasize the need for strength-calibrated constitutive models to improve the accuracy of site-specific seismic hazard assessments. Full article

This paper addresses the errors that arise when calculating the convective heat transfer in concentric annular pipes by using the equivalent diameter and turbulent heat transfer formula for circular pipes. This approach employs numerical simulations to solve the Reynolds-averaged Navier–Stokes equations and uses the realizable k–ε turbulence model and a low Reynolds number model near a wall. This study conducts numerical simulations of turbulent convective heat transfer within a concentric annular pipe. The results show that the shear stress on the inner wall surface of the concentric annular pipe and the heat transfer Nusselt number are significantly higher than those on the outer wall surface. At the same Reynolds number, both the entrance length and the peak velocity increase upon increasing the inner-to-outer diameter ratio. A correction factor for the inner-to-outer diameter ratio is proposed to achieve differentiated and accurate predictions for the inner and outer wall surfaces. The results clearly demonstrate the effect of the inner-to-outer diameter ratio on heat transfer. Full article

In order to deeply investigate the effects of various factors on the shear behavior of RC beams strengthened with fiber-reinforced polymer (FRP) grid–polymer cement mortar (PCM) composite, and to construct a more accurate formula for the shear behavior of reinforced concrete beams, the following work is carried out in this investigation: Firstly, the finite element numerical simulation of FRP grid–PCM composite RC beams model is carried out using ABAQUS and compared with the test results to verify the correctness of the model; then, the effects of the amount of FRP grid reinforcement, the elastic modulus of the FRP grid, the shear span ratio of the beam, the concrete strength, and the shear reinforcement ratio on the shear performance of the strengthened beams are analyzed; finally, based on the effective strain of the FRP grid to quantify its actual shear contribution, a calculation formula of the shear behavior Capacity of RC Beams Strengthened with an FRP grid–PCM composite is proposed. The results show that the model established in this paper can effectively simulate the shear behavior of the beams in the test; additionally, the effects of the amount of FRP grid reinforcement, the shear span ratio, and the concrete strength are more significant. Finally, the theoretical results of the calculation formula fit well with the collected experimental ones. Full article

With the popularization of the concept of seismic performance-based design, the correct and quantitative evaluation of post-earthquake damage to structural components has become a research focus. Referring to the concrete constitutive relationship mentioned in the Chinese national standard GB/T 50010-2010, this study proposes a damage assessment method for concrete components based on material damage. According to the value of the uniaxial damage evolution parameter of concrete (d_c(t)), the damage grades of concrete components are defined. It is specified that, when the value of d_c(t) is less than the d_c(t),r value corresponding to the peak concrete strain (ε_c(t),r), the concrete component is in a non-damaged state (Level L1). When the value of d_c(t) is greater than the d_c(t)u value corresponding to the concrete strain (ε_c(t)u), the concrete component is in a severely damaged state (Level L6). When the value of d_c(t) is between these two values, the damage grade of the concrete component (levels L2 to L5) is determined using linear interpolation. To promote its engineering application, this study also proposes a quantitative expression for the damage assessment method for concrete components based on d_c(t). To verify the rationality of the damage assessment method for concrete components based on d_c(t), a refined model of rectangular, T-shaped, and L-shaped concrete shear wall components was established using ABAQUS software, and a nonlinear finite element analysis was carried out. The simulation results show that (a) the damage assessment method for concrete components based on d_c(t) can better characterize damage to concrete shear wall components; (b) when defining the damage grades of concrete shear wall components, using d_c is more reasonable than using d_t; and (c), from a macroscopic perspective, the damage assessment method for concrete components based on d_c(t) is more in line with actual expectations and has a higher safety factor compared with the damage assessment method for concrete components based on the concrete compressive strain (ε_c) mentioned in the Chinese association standard T/CECA 20024-2022. Full article

While the development of sustainable construction materials, such as green concrete made from glass waste or recycled concrete aggregate, has been extensively researched, much of the existing work has focused narrowly on these two components. This limited scope highlights the need for further investigation to comprehensively address their drawbacks and expand the available knowledge base. Moreover, the current study uniquely emphasizes the shear response of green concrete, a critical aspect that has not been previously explored. Push-off shear samples made of green concrete, a mixture of recycled concrete, and glass waste, were built and subjected to direct shear loading testing to investigate shear response. In different proportions (0, 10, 25, 50, and 100%), fine glass aggregate is used in place of river sand. At different ratios (0, 10, 20, and 40%), coarse glass aggregate was substituted for coarse natural aggregate to form four mixtures. Additionally, recycled concrete and coarse glass aggregates were utilized instead of coarse natural aggregates. In the last group, coarse natural aggregate was substituted with recycled concrete aggregates in different proportions (0, 16, 40, and 80%). Measurements were made of the applied shear force and the sliding of the shear transfer plane during the test. The tested mixtures’ failure, shear strength, shear slip, shear stiffness, and shear stress slip correlations were examined. According to the results, all of the samples failed in the shear transfer plane. The shear strength of mixes containing 10, 25, 50, and 100% fine glass was, respectively, 12.8%, 14.7%, 29.5%, and 39% lower than the control combination without fine glass. As the amount of recycled glass and concrete materials grew, so did the shear slip at the shear transfer plane. In recent years, numerous studies have proposed formulas to predict the push-off shear strength of plain concrete, primarily using compressive strength as the key parameter—often without accounting for the influence of infill materials. The present study introduces an improved predictive model that incorporates the contents of recycled concrete aggregate, coarse glass aggregate, or fine glass aggregate as correction factors to enhance accuracy. Full article

Because of the degradation of building materials and the increased design load, concrete parts continually require repair. Special cementitious matrix components, Strain Hardening Cementitious Composites (SHCC), have exceptional ductility, strength growth during cracking, and recurrent controlled-opening crack formation. The purpose of this study was to improve the qualities of SHCC by reinforcing it with steel metal mesh. This study examined the optimization and effects of shear strengthening on the shear capacity of both damaged and undamaged reinforced concrete beams by employing SHCC internally reinforced with steel mesh fabric (SMF). Under bending loading, eight reinforced concrete beams were evaluated. Four of them were loaded to shear crack before any strengthening could be performed. The beams were 1500 mm in length, 200 mm in height, and 120 mm in width, and one, two, or three SMFs were applied. The beams’ whole shear span had external strengthening applied on both sides. Additionally, layers of strengthening in the U-shape were applied. The walls of the strengthening were thirty millimeters thick. The failure, load-deflection response, ultimate load, ultimate displacement, and energy absorbance of the tested beams were determined and discussed. Compared to an unstrengthened beam, the ultimate load of undamaged beams increased by 47%, 57%, and 90% when reinforced with 1, 2, or 3 layers of SMF, respectively, within the SHCC. Additionally, incorporating one, two, or three SMF layers within the SHCC improved the deflection of strengthened undamaged beams by 52%, 87%, and 116%, respectively. For damaged beams, the maximum load was approximately 11% lower than that of their undamaged counterparts, regardless of the number of SMF layers used in the SHCC strengthening. Applying one, two, or three layers of SMFs within the strengthening layer led to increases of the ratios of 163, 334, and 426%, respectively, in the energy absorbed by the strengthened beams in comparison to the control beam. The shear strength of the strengthened beams was determined through analytical modeling by implementing a correction factor (α = 0.5) to take into consideration the debonding action between the SHCC layer and the beam sides. This factor significantly improved the predictive accuracy of the analytical models by matching the mean ratio of the analytical findings to the experimental predictions. Full article

China has an existing building area of 80 billion square meters, where reinforced concrete structures have a large quantity and a wide surface area. The risk of structures being subjected to blast loading is relatively high. Reactive powder concrete has the specialties of ultra-high toughness, super strength, and a high strength to ponderance ratio. Reinforced concrete (RC) structures strengthened by RPC are called RPC-RC structures, which can easily elevate the explosive load resistance of building structures while also strengthening the building. It is a significant method used in avoiding the collapse of structures under explosive loads. The dynamic reaction and damage evaluation approaches of RPC-RC columns under explosive load have not been deeply studied. For addressing this issue, numerical simulation of RPC strengthened RC columns under explosive load was carried out by LS-DYNA (R10), and the correctness of the numerical simulation was verified by comparing it with relevant experimental results. In this paper, a finite element model of an RPC-RC column was established, and the main factors affecting the anti-explosion performance of an RPC-RC column were studied. The influence of the RPC reinforcement layer parameters (RPC thickness, RPC strength, longitudinal reinforcement ratio, and stirrup ratio) on the dynamic reaction and damage degree of RPC-RC columns was examined. The consequences indicated that the failure mode of the columns after RPC reinforcement can alter from bending shear damage to bending damage. As the thickness and strength of the RPC increases, the longitudinal reinforcement ratio increases, the stirrup ratio increases, and the maximum horizontal deformation of the center point of the RPC reinforced RC columns decreases. For RPC-RC columns with a height of 3–4 m and a width of 300–400 mm under blast loading, columns with an axial compression ratio greater than 0.3 will collapse, while columns with an axial compression ratio less than 0.3 are less likely to collapse. In the light of the calculation outcomes, a formula for reckoning the damage index of RPC-RC columns was proposed, taking into account factors such as proportional distance, axial compression ratio, RPC thickness, longitudinal reinforcement ratio, and stirrup ratio. Full article

The effective length factor (ELF) of bridge piers, a critical design parameter, is determined by solving the transcendental equation governing stability. Efficient and accurate solutions to these equations under various constraints are essential for automating bridge design software. In this paper, the bridge pier is simplified as an elastically restrained column based on the Timoshenko beam model, and the pier stability equation under general elastic constraints considering shear deformation is derived. By analyzing the distribution patterns of the solutions to the transcendental equations with and without considering shear deformation, a novel two-stage Adaptive Sequential Root Search Method based on bisection algorithm (ASRSBM2s) is proposed to calculate the ELF. In the first stage, the smallest positive root of the transcendental equation without considering shear deformation is first calculated, and the obtained positive root is used to restrict the solution domain of the transcendental equation considering shear deformation in the second stage. Compared with the results of the finite element method (FEM), the proposed algorithm can accurately determine the correct roots of the transcendental equation for various bridge scenarios, and the maximum relative error of the calculated ELF of bridge piers is below 2.5%. Full article

This study investigated whether the suspension method (tenderstretch, TS or Achilles tendon, AT) can improve the quality of horsemeat by analyzing longissimus dorsi (LD) and semitendinosus (ST) muscles. A total of 25 horse carcasses were considered experimental units and split longitudinally, with one half suspended using the TS method and the other half using the AT method, which enabled a direct comparison within the carcass. After 7 days of aging under commercial processing conditions, the LD and ST muscles were analyzed for pH, color (L*, a*, b*), water-holding capacity (drip loss, thawing loss, cooking loss), tenderness (Warner–Bratzler shear force), and sarcomere length. Statistical analysis was performed using the MIXED procedure in SAS, with Bonferroni correction applied for post hoc comparisons. Significant differences were found between the muscles: LD had higher tenderness (39.28 N vs. 49.77 N, p = 0.0011), lower cooking loss (23.56% vs. 27.04%, p = 0.0002), and higher thawing loss (12.38% vs. 9.72%, p = 0.0021) compared to ST muscle, which had a lighter color (L* = 41.90 vs. 37.73, p < 0.0001) and longer sarcomeres (2.22 μm vs. 1.74 μm, p < 0.0001). While the TS suspension method significantly increased sarcomere length (2.05 μm vs. 1.92 μm, p = 0.0020), it did not lead to significant improvements in other quality attributes such as pH, water-holding capacity, or tenderness. The results indicate that although the TS method affects muscle structure by elongating sarcomeres (with an average difference of 0.13 μm), it does not significantly improve the overall quality of the horsemeat compared to the AT method after 7 days of aging. A combination of factors beyond suspension methods, such as optimizing aging periods or considering additional processing techniques, may therefore be required to improve horsemeat quality. This study provides insights into the specific attributes of LD and ST muscles and their response to suspension methods and contributes to a better understanding of optimizing horsemeat quality for commercial purposes. Full article

Laminated composite bolted joints are increasingly used in the aerospace field, and their damage and failure behavior has been studied in depth. In view of the complexity and stability requirements of laminated composite bolted structures, accurate prediction of damage evolution and failure behavior is significant to ensure the safety and reliability of the structures. In this paper, a novel asymptotic damage model is developed to predict the damage process and failure behavior of laminated composite bolted joints. In this model, the modified Puck criterion and the maximum shear stress criterion are used for fiber yarns. The parabolic yield criterion is adopted for the matrix, and the fiber fracture, inter-fiber fracture and matrix fracture are considered at the microscopic level. The pull-out strength and progressive failure behavior of countersunk and convex bolted joints structures are predicted by using the proposed model, and the corresponding experimental studies are carried out. The results show that the prediction results are in good agreement with the experimental data, which verifies the reliability of the model. Additionally, the effects of different structural parameters (thickness and aperture) on the progressive damage and failure behavior during pull-out is analyzed by the proposed model, and correction factors of pull-out strength are obtained, which provides a powerful tool for the design, analysis and progression of laminated composite bolted joint structures. Full article

Ground liquefaction potential analysis is a fundamental characterization in areas with continuous seismic activity, such as Ecuador. Geotechnical liquefaction studies are usually approached from dynamic penetration tests, which pose problems both in their correct execution and in their evaluation. Our research involves analyzing dynamic penetration tests and microtremor geophysical surveys (horizontal-to-vertical spectral ratio technique, HVSR) for analyzing the liquefaction potential at the base of the San Marcos dam, a reservoir located in Cayambe canton (Ecuador). Based on the investigations performed at the time of construction of the dam (drilling and geophysical refraction profiles) and the application of 20 microtremor observation stations via the HVSR technique, an analysis of the safety factor of liquefaction (SF_liq) was conducted using the 2001 Youd and Idriss formulation and the values of the standard penetration test (SPT) applied in granular materials (sands). In addition, the vulnerability index (K_g) proposed by Nakamura in 1989 was analyzed through the HVSR records related to the ground shear strain (GSS). The results obtained in the HVSR analysis indicate the presence of a zone of about 100 m length in the central part of the foot of the dam, whose GSS values identified a condition of susceptibility to liquefaction. In the same area, the SPT essays analysis in the P-8A drill hole also shows a potential susceptibility to liquefaction in earthquake conditions greater than a moment magnitude (M_w) of 4.5. That seismic event could occur in the area, for example, with a new activity condition of the nearby Cayambe volcano or even from an earthquake from the vicinity of the fractured zone. Full article