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The management strategies of thoracolumbar (TL) burst fractures include posterior, anterior, and combined approaches. However, the rigid constructs pose a risk of proximal junctional failure. In this study, we aim to systemically evaluate the biomechanical performance of different TL reconstruction constructs using finite element analysis. Furthermore, we investigate the motion and the stress on the proximal junctional level adjacent to the constructs. We used a T10-L3 finite element model and simulated L1 burst fracture. Reconstruction with posterior instrumentation (PI) alone (U2L2 and U1L1+(intermediate screw) and three-column spinal reconstruction (TCSR) constructs (U1L1+PMMA and U1L1+Cage) were compared. Long-segment PI resulted in greater global motion reduction compared to constructs with short-segment PI. TCSR constructs provided better stabilization in L1 compared to PI alone. Decreased intradiscal and intravertebral pressure in the proximal level were observed in U1L1+IS, U1L1+PMMA, and U1L1+Cage compared to U2L2. The stress and strain energy of the pedicle screws decreased when anterior reconstruction was performed in addition to PI. We showed that TCSR with anterior reconstruction and SSPI provided sufficient immobilization while offering additional advantages in the preservation of physiological motion, the decreased burden on the proximal junctional level, and lower risk of implant failure. [ABSTRACT FROM AUTHOR]

The use of carbon fiber-reinforced polymer (CFRP) rods offers a good solution for external strengthening of flexural reinforced concrete (RC) members. Limited data are available on the behavior of beams externally reinforced with CFRP rods under a loading–unloading protocol, which is of great importance for structural components subjected to vehicle loading. The embedment depth mandated by the majority of standards cannot always be acquired due to concrete cover limitations; the influence of embedment depth under this loading–unloading sequence needs to be investigated. This research studied the effects of rod embedment depth by comparing fully-embedded rods with half-embedded rods under a loading–unloading protocol and comparing the results with monotonic responses. An identical specimen without CFRP reinforcement functioned as the controlling element. The near-surface mounted technique (NSM) was used to integrate the rods with the concrete. The results show that CFRP rods positively affect the load-carrying capacity under a loading–unloading condition. The rods reduce the member's ductility under monotonic loading but have no negative impact under loading–unloading. Whereas the difference in embedment depth configuration slightly affected the enhancement under monotonic loading, the half-embedded rods drastically reduced the capacity improvement under the loading–unloading sequence. An embedment depth deviating from the advised depth, should not be implemented for members subjected to a loading–unloading condition. The CFRP placement method had an impact on the failure behavior of the elements. The half-embedded rod failed by debonding between the rod and the epoxy resin, while the fully-embedded members were characterized by concrete spalling. [ABSTRACT FROM AUTHOR]

The old existing reinforced concrete (RC) structures in Taiwan are susceptible to severe damage under earthquakes because of the soft-story mechanism. Moreover, the effects of near-fault ground motions often contain a long period of velocity pulse and permanent ground displacement. This study is based on the tri-axial shaking table test conducted at the National Center for Research on Earthquake Engineering in Taiwan and a series of seismic performance evaluations of a non-ductile RC structure in Taiwan. Finite element analysis (FEA) will be conducted to simulate the linear and nonlinear behavior of the seven-story building. This accommodates the damage plasticity model for concrete and the elastic-perfectly plastic model for reinforcement. Comparison of the results between the experimental test and numerical model showed that the similarity of the vibration period has a great influence on the simulation results. The findings showed that the data of acceleration and displacement behavior corresponded with the experimental results in a satisfactory margin. Also, the damage mode is very similar to the shaking table test results. The study found that using FEA can satisfactorily simulate the seismic performance of mid-rise buildings under a near-fault earthquake. [ABSTRACT FROM AUTHOR]

Finite element analysis has been commonly used in many studies to examine the performance of structural elements. The objective of this article is to assess the relevance of geometric and strengthened pattern uncertainty on prestressed reinforced concrete beams strengthened by fiber-reinforced plastics based on a nonlinear finite element analysis. The parametric study focuses on the significant effects of fiber-reinforced polymer, beam length, and prestressed load on the ultimate loading capacity of the prestressed reinforced concrete beam strengthened by fiber-reinforced plastics. The results demonstrate the advantages of fiber-reinforced plastics that significantly increase the stiffness and the ultimate loading capacity of prestressed reinforced concrete beams. It is found that the beams that are strengthened by the FRP with fibers oriented at 0° have better results than other orientation angles. [ABSTRACT FROM AUTHOR]

Background: Semi-rigid lumbar fusion offers a compromise between pedicle screw-based rigid fixation and non-instrumented lumbar fusion. However, the use of semi-rigid interspinous stabilization (SIS) with interspinous spacer and ligamentoplasty and semi-rigid posterior instrumentation (SPI) to assist interbody cage as fusion constructs remained controversial. The purpose of this study is to investigate the biomechanical properties of semi-rigidly stabilized lumbar fusion using SIS or SPI and their effect on adjacent levels using finite element (FE) method.Method: Eight FE models were constructed to simulate the lumbosacral spine. In the non-fusion constructs, semi-rigid stabilization with (i) semi-rigid interspinous spacer and artificial ligaments (PD-SIS), and (ii) PI with semi-rigid rods were simulated (PD + SPI). For fusion constructs, the spinal models were implanted with (iii) PEEK cage only (Cage), (iv) PEEK cage and SIS (Cage+SIS), (v) PEEK cage and SPI (Cage+SPI), (vi) PEEK cage and rigid PI (Cage+PI).Result: The comparison of flexion-extension range of motion (ROM) in the operated level showed the difference between Cage+SIS, Cage+SPI, and Cage+PI was less than 0.05 degree. In axial rotation, ROM of Cage+SIS were greater than Cage+PI by 0.81 degree. In the infrajacent level, while Cage+PI increased the ROM by 24.1, 27,7, 25.9, and 10.3% and Cage+SPI increased the ROM by 26.1, 30.0, 27.1, and 10.8% in flexion, extension, lateral bending and axial rotation respectively, Cage+SIS only increased the ROM by 3.6, 2.8, and 11.2% in flexion, extension, and lateral bending and reduced the ROM by 1.5% in axial rotation. The comparison of the von Mises stress showed that SIS reduced the adjacent IVD stress by 9.0%. The simulation of the strain energy showed a difference between constructs less than 7.9%, but all constructs increased the strain energy in the infradjacent level.Conclusion: FE simulation showed semi-rigid fusion constructs including Cage+SIS and Cage+SPI can provide sufficient stabilization and flexion-extension ROM reduction at the fusion level. In addition, SIS-assisted fusion resulted in less hypermobility and less von Mises stress in the adjacent levels. However, SIS-assisted fusion had a disadvantage of less ROM reduction in lateral bending and axial rotation. Further clinical studies are warranted to investigate the clinical efficacy and safety of semi-rigid fusions. [ABSTRACT FROM AUTHOR]

Buckling analyses of laminated truncated conical shells subjected to external hydrostatic compression are carried out by employing the Abaqus finite element program. The critical buckling loads of these truncated conical shells with a given material system are maximized with respect to fiber orientations by using the golden section method. Through parametric studies, the influences of the end condition, shell thickness, shell length, shell radius ratio and cutout size on the optimal buckling loads, the associated optimal fiber orientations and the associated buckling modes are demonstrated and discussed. [ABSTRACT FROM AUTHOR]

Numerical analyses are carried out by using the Abaqus finite element program to predict the ultimate pressure capacity and the failure mode of the PWR prestressed concrete containment at Maanshan Nuclear Power Plant, Taiwan, R.O.C. under long term prestressing loss. Material nonlinearity such as concrete cracking, tension stiffening, shear retention, concrete plasticity, yielding of prestressing tendon, yielding of steel reinforcing bar, yielding of liner plate and relaxation of prestressing tendon are all simulated with proper constitutive models. The results of the numerical analysis show that after the 40 years of service, the prestresses in the prestressing tendons would lose about 19% of their initial values. However, under long term prestressing loss, the ultimate pressure capacity of the containment is still higher than the design pressure 482 kPa by 58%. [ABSTRACT FROM AUTHOR]

A nonlinear constitutive model for a single lamina is proposed for the failure analysis of composite laminates. In the material model, both fiber and matrix are assumed to behave as elastic-plastic and the in-plane shear is assumed to behave nonlinearly with a variable shear parameter. The damage onset for individual lamina is detected by a mixed failure criterion, composed of the Tsai-Wu criterion and the maximum stress criterion. After damage takes place within the lamina, the fiber and in-plane shear are assumed to exhibit brittle behavior, and the matrix is assumed to exhibit degrading behavior. The proposed nonlinear constitutive model is tested against experimental data and good agreement is obtained. Then, numerical analyses are carried out to study the failure behavior of symmetric angle-ply composite laminates and symmetric cross-ply composite laminates subjected to biaxial loads. Finally, the conclusions obtained from the numerical analysis are given. [ABSTRACT FROM AUTHOR]

Free vibration analyses of laminated truncated conical shells subjected to axial compressive forces are carried out by employing the Abaqus finite element program. The fundamental frequencies of these truncated conical shells with a given material system are then maximized with respect to fiber orientations by using the golden section method. Through parametric studies, the influences of the end condition, shell length, shell radius ratio and the compressive force on the maximum fundamental frequencies, the associated optimal fiber orientations and the associated vibration modes are demonstrated and discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] FRP-strengthened RC slabs are investigated by finite element software ABAQUS. [•] Proper constitutive models are applied to simulate nonlinear material behavior. [•] A proper bond model is found essential to be incorporated into numerical analysis. [•] Parametric analyses are performed to examine the behavior of strengthened slabs. [ABSTRACT FROM AUTHOR]

Abstract: Abaqus finite element program is employed to analyze the ultimate load capacities of square reinforced concrete plates strengthened by fiber-reinforced plastics. Appropriate constitutive models are introduced and validated to stimulate nonlinear material behavior of reinforced concrete and fiber-reinforced plastics. The influences of FRP reinforcement, steel reinforcement, and concrete properties on the ultimate strengths of the reinforced concrete plates are investigated. Finally, based on the numerical results, empirical equations are proposed to predict increment of ultimate load capacities of the square reinforced concrete plates strengthened by fiber-reinforced plastics, which would be useful for practical engineering applications. [Copyright &y& Elsevier]

Abstract: Free vibration analyses of laminated curved panels with central circular cutouts and subjected to axial compressive forces are carried out by employing the Abaqus finite element program. The fundamental frequencies of these composite laminated curved panels with a given material system are then maximized with respect to fiber orientations by using the golden section method. Through parametric studies, the significant influences of the panel aspect ratio, the panel curvature, the cutout size and the compressive force on the maximum fundamental frequencies, the optimal fiber orientations and the associated fundamental vibration modes of these panels are demonstrated and discussed. [Copyright &y& Elsevier]

Abstract: Proper material constitutive models for concrete-filled double skin tube (CFDST) columns with circular cross-section and subjected to axial compressive forces are proposed and verified against experiment data using the nonlinear finite element program Abaqus. It is shown that CFDST columns can provide a good confining effect for concrete core, especially when the diameter-to-thickness ratios of both the outer and the inner tubes are small. In addition, empirical equations are proposed to predict the lateral confining pressure of the concrete core for CFDST columns. Finally, the axial strengths of the CFDST columns calculated by the proposed formulations are compared with AISC formulations against the experimental data. It has been shown that the proposed formulations are better than the AISC formulations. [Copyright &y& Elsevier]

Abstract: The Abaqus finite element program together with nonlinear material constitutive models for concrete-filled tube (CFT) and steel gusset plate is used to analyze the behaviors of the gusset plate type CFT-to-Bracing connections subjected to axial compressive forces. It is found that the failure of CFT-to-Bracing connections occurs below the connecting area. Local bulged shapes of the steel tube might take place in the areas close to the gusset plate and the fixed end under the failure stage. The ultimate strengths of the CFT columns slightly increase with the increasing of the load ratio and the thickness of the gusset plate. The introduction of the cutouts on the gusset plates slightly increases the ultimate strength of the CFT column and causes more local bulged shapes on the steel tubes below the connection area under the failure stage. [Copyright &y& Elsevier]

Abstract: The buckling resistance of fiber-reinforced laminated cylindrical panels with a given material system and subjected to uniaxial compressive force is maximized with respect to fiber orientations by using a sequential linear programming method together with a simple move-limit strategy. The significant influences of panel thicknesses, curvatures, aspect ratios, cutouts and end conditions on the optimal fiber orientations and the associated optimal buckling loads of laminated cylindrical panels have been shown through this investigation. [Copyright &y& Elsevier]

Abstract: Numerical analyses are carried out by using the ABAQUS finite element program to predict the ultimate pressure capacity and the failure mode of the PWR prestressed concrete containment at Maanshan nuclear power plant. Material nonlinearity such as concrete cracking, tension stiffening, shear retention, concrete plasticity, yielding of prestressing tendon, yielding of steel reinforcing bar and degradation of material properties due to high temperature are all simulated with proper constitutive models. Geometric nonlinearity due to finite deformation has also been considered. The results of the analysis show that when the prestressed concrete containment fails, extensive cracks take place at the apex of the dome, the junction of the dome and cylinder, and the bottom of the cylinder connecting to the base slab. In addition, the ultimate pressure capacity of the containment is higher than the design pressure by 86%. [Copyright &y& Elsevier]

Abstract: A nonlinear material constitutive model, including a nonlinear in-plane shear formulation and the Tsai–Wu failure criterion, for fiber–composite laminate materials is employed to carry out finite element buckling analyses for composite laminate skew plates under uniaxial compressive loads. The influences of laminate layup, plate skew angle and plate aspect ratio on the buckling resistance of composite laminate skew plates are presented. Comparing with the linearized buckling loads of the skew plates, one can observer that the nonlinear in-plane shear together with the failure criterion have significant influence on the ultimate loads of the composite laminate skew plates with [±θ]10S and [±θ/90/0]5S layups but not the [α/0]10S layup. [Copyright &y& Elsevier]

Abstract: Proper material constitutive models for concrete-filled tube (CFT) columns subjected to an axial compressive force and bending moment in combination are proposed and verified in this paper by using the nonlinear finite element program ABAQUS compared against experimental data. In the numerical analysis, the cross sections of the CFT columns are categorized into three groups, i.e., ones with circular sections, ones with square sections, and ones with square sections stiffened with reinforcing ties. It is shown that the steel tubes can provide a good confining effect on the concrete core when the axial compressive force is large. The confining effect of a square CFT stiffened by reinforcing ties is stronger than that of the same square CFT without stiffening ties but weaker than that of a circular CFT. Nevertheless, when the spacing of reinforcing ties is small, a CFT with a square section might possibly achieve the same confining effect as one with a circular section. [Copyright &y& Elsevier]

Numerical analyses are performed using the ABAQUS finite element program to predict the ultimate loading capacity of rectangular reinforced concrete beams strengthened by fiber-reinforced plastics applied at the bottom or on both sides of these beams. Nonlinear material behavior, as it relates to steel reinforcing bars, plain concrete, and fiber-reinforced plastics is simulated using appropriate constitutive models. The influences of fiber orientation, beam length and reinforcement ratios on the ultimate strength of the beams are investigated. It has been shown that the use of fiber-reinforced plastics can significantly increase the stiffnesses as well as the ultimate strengths of reinforced concrete beams. In addition, with the same fiber-reinforced plastics layer numbers, the ultimate strengths of beams strengthened by fiber-reinforced plastics at the bottom of the beams are much higher than those strengthened by fiber-reinforced plastics on both sides of the beams. [Copyright &y& Elsevier]

Details on the fundamental frequencies of fiber-reinforced laminated curved panels which are maximized with respect to fiber orientation, highlighting panel thickness, curvature, aspect ratio, cutouts and end conditions on the maximum fundamental frequencies. Details on constitutive matrix for fiber-composite laminae; Examination of numerical analysis; Identification of conclusions.

Throughout its service life, structural reinforced concrete (RC) encounters cyclic loads and the load amplitude might always vary, leading to a mixed high and low-cycle failure. This research investigates the high cyclic response of RC T-beams strengthened in the negative moment region using near-surface mounted (NSM) Carbon Fiber Reinforced Polymer (CFRP) rods. The distinctive aspect lies in exploring varied embedment depths, including the introduction of half-embedded configurations as an alternative NSM technique. The study comprehensively analyzes load-carrying capacity, failure modes, energy dissipation, ductility, stiffness degradation, and strain behavior, providing insights into the effects of loading rates on structural response. Through an experimental program comparing fully-embedded (BF-D) and half-embedded (BH-D) CFRP rods with a control beam (BN-D) under high-rate cyclic loading, significant increases in ultimate load capacity (21.23% for BH-D and 30.86% for BF-D) are demonstrated despite debonding occurrences. The findings highlight a trade-off between benefits (enhanced ultimate load capacities, improved energy dissipation, and increased stiffness) and drawbacks (reduced ductility and tendencies toward brittle behavior) under high loading rates. Furthermore, a rate-dependent material formula is developed and validated, predicting the flexural strength of the negative moment region in good agreement with experimental results. Finally, this research contributes practical solutions to RC element strengthening challenges and advances understanding of NSM-CFRP-strengthened beam, emphasizing the impact of loading rates on structural response. [ABSTRACT FROM AUTHOR]

The goal of this paper is to evaluate the post-failure behavior of the Hsien-du-shan rock avalanche, which was triggered by Typhoon Morakot in 2009, using a three-dimensional (3D) discrete element program, namely, 3DEC. The 3D slope topography and local joint sets are explicitly considered in the calculations, and the joint sets cut the sliding rock mass into blocks with arbitrary shapes. The modeled blocks exhibit the elastic behavior of the local rocks. The analysis successfully simulates the wedge failure at the initiation of the landslide. Additionally, the 3DEC results clarify the local rock sliding phenomena at the boundaries of the source area. The simulated depositional area correlates well with the actual area affected by the Hsien-du-shan rock avalanche. In addition, the erosion of a ridge by the sliding rock near the southwestern margin of the area at an elevation of 590 m has a significant influence on the shape and size of the impacted area. The interlocking effect between blocks is also considered. [ABSTRACT FROM AUTHOR]

This paper assesses the impact of Chiu-fen-erh-shan residual slope failure using a three-dimensional distinct element program. The simulation results indicate that rocks will severely damage the Lung-Nan path. The Taanshan syncline generates a depression zone adjoining to the slope toe and acts as a buffer zone to trap failing rocks. Some rocks will travel through the syncline, which poses a risk to visitors at the monument and the Shihmen observation deck. Few rocks will pass though the memorial park near the northern boundary of the slope. Visitors should be evacuated out of the impact area during a heavy rainfall event. [ABSTRACT FROM AUTHOR]

The CoCrFeMnNi high entropy alloys remain an active field over a decade owing to its excellent mechanical properties. However, the application of CoCrFeMnNi is limited because of the relatively low tensile strength. Here we proposed a micromechanical model which adopted from the theory of dislocation density to investigate the strengthening mechanisms of precipitation of chromium-rich non-equiatomic CoCrFeMnNi alloy. The microstructures of CoCrFeMnNi were obtained directly from SEM-BSE images with different annealing temperatures. The proposed framework is validated by comparing simulations with experiments of uniaxial tensile tests on the CoCrFeMnNi alloys under different annealing temperatures. The stress–strain curves indicate that the precipitate has greater influence on post-yield hardening than the initial yielding strength. In addition, we identified that the particle distribution, controlled by the average size of the particle and the volume fraction of precipitation, can significantly enhance the strengthening effect. The numerical results indicate that HEAs with a precipitate distribution closer to a normal distribution and with smaller average size will tend to have higher strength and ductility. [ABSTRACT FROM AUTHOR]

Under cyclic loading circumstances, reinforced concrete (RC) constructions may be subject to failure. Because they may indicate inadequate capacity owing to aging, environmental effects, or unintentional impacts, strengthening is critical to resist static and cyclic loads. Therefore, the goal of this research was to look at how bare and negative moment region strengthened RC T -beams behaved under monotonic and low reversed cyclic loads. As the strengthening system, carbon fiber reinforced polymer (CFRP) rods having different embedment depths were used with a near-surface mounted (NSM) approach. The findings of this study demonstrated that the impact of NSM-CFRP rods was sufficient for extending the ultimate load and capturing cracks under monotonic loading. Additionally, as compared to their bare counterparts, the negative moment region NSM-CFRP strengthened beams showed improved hysteresis behavior, a larger energy dissipation capacity together with initial stiffness, and a reduced damage index under cyclic loading. Moreover, the experimentally determined load-carrying capacities matched reasonably well with the theoretical predictions. [ABSTRACT FROM AUTHOR]

• A mesoscale kMC model is constructed to study the grain size effect of nanoglasses (NGs). • Variable characteristic strain captures the structural variation in terms of a shear band development. • Reduction of elastic constants of STZs simulates the failure behavior akin to the experimental tests. • Inhomogeneous to homogeneous deformation transition occurs as grain size decreases to ∼10 nm. • Deformation mechanism for the deformation transition due to grain size of NGs has been elucidated. Severe shear localization in metallic glasses (MGs) significantly limits their mechanical performance. Nanoglass (NG), composed of heterogeneous glassy domains created by introducing interfaces into MGs at the nanoscale, could be a promising strategy against severe shear localization, as demonstrated by numerous atomistic simulations. This study introduces a novel mesoscale kinetic Monte Carlo (kMC) model with a variable characteristic strain (VCS) to investigate the grain size effect in NGs. This model captures the complex evolution of shear bands during deformation, revealing a surprising transition from inhomogeneous to homogeneous deformation as the NG grain size decreases to approximately 10 nm. This transition is attributed to the impediment of shear band formation by the small grain size, facilitated by softer interfaces guiding early shear transformation zone (STZ) activities across the entire sample. Furthermore, a progressive reduction of elastic constants simulates the failure response observed in experiments. Our model predicts a critical grain size for the transition in agreement with molecular dynamics simulations and experiments, highlighting its potential for designing NGs with enhanced shear resistance. This mesoscale model enables the investigation of NG deformation with microstructural features on an experimentally-relevant spatial-temporal scale. This paves the way for tailoring NG microstructures to achieve enhanced mechanical performance, and opens new avenues for exploring the influence of interfaces in controlling shear localization. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: A meshless collocation method is developed for the static analysis of plane problems of functionally graded (FG) elastic beams and plates under transverse mechanical loads using the differential reproducing kernel (DRK) interpolation, in which the DRK interpolant is constructed by the randomly distributed nodes. A point collocation method based on this DRK interpolation is developed for the plane stress and strain problems of homogeneous and FG elastic beams and plates. It is shown that the present DRK interpolation-based collocation method is indeed a truly meshless approach with excellent accuracy and has a fast convergence rate. [Copyright &y& Elsevier]

Metal solutions, such as high- and medium-entropy alloys, exhibit extraordinary mechanical performance in comparison to regular alloys. In this study, we employ a crystal plasticity finite element model (CPFEM) to study the strengthening mechanisms of a new medium-entropy alloy, Ti 65 (AlCrNb) 35. A 3D representative model is constructed by processing experimental results for Ti 65 (AlCrNb) 35 , such as average grain size, grain size distribution, and initial texture, using the open-source software Dream.3D. The constitutive law for the grains is described by the crystal plasticity and implemented in Abaqus user-defined material (UMAT). The results of uniaxial tensile tests are utilized to calibrate the required parameters in the CPFEM. Strengthening effects resulting from the grain size, strain rate, and cyclic loading for Ti 65 (AlCrNb) 35 are investigated by performing numerical simulations based on the proposed computational framework. Numerical simulation results show that the yield strength increases with decreasing initial grain size, which agrees well with experimental observations of the Hall–Petch effect. In addition, the rate-dependent yield stress increases as the applied strain rate increases in the tensile tests. Moreover, the cyclic loading results demonstrate the isotropic hardening behaviors and the saturation of yielding strength when the maximum strain reaches 10%. Finally, we discuss the contributions of different strengthening mechanisms on the yield strength of Ti 65 (AlCrNb) 35 under different load conditions. • We employ a micromechanical model to study the strengthening mechanisms of medium-entropy alloys. • A 3D representative model is constructed by processing experimental results using Dream.3D. • The micromechanical constitutive model of medium-entropy alloys is implemented in ABAQUS UMAT. • We study the strengthening effects of grain size, strain rate, and cyclic loading on the yielding stress. • The proposed computational framework can be applied to other novel alloys. [ABSTRACT FROM AUTHOR]