Parametric Finite Element Model Research Articles

Information fusion-based maintenance strategies selection for coastal concrete bridges using recycled fishing nets

Repurposing recycled materials for coastal concrete bridge maintenance addresses both engineering requirements and marine ecosystem preservation. This study explored the application of recycled nylon (RN) and polyethylene (PE) from discarded fishing nets in coastal concrete beam maintenance. Specifically, these fibers were incorporated into the polymer cement mortar (PCM) to produce two repair materials. Then, thirteen unrepaired or preventive/post-repaired concrete beams were exposed to the tidal zone for one or two years, followed by beam bending tests and the establishment of the corresponding parametric Finite element modeling (FEM). As an alternative to traditional heavy-parameter models, a novel lightweight crack segmentation model (LiteSqueezeSeg) was proposed for quantitatively analyzing beam surface crack properties. Lastly, experimental, simulated, and quantitative crack information were fused to comprehensively assess the beam performance. Results showed that both PCM-RN and PCM-PE effectively inhibit chloride ion penetration. The proposed LiteSqueezeSeg model (95.66% accuracy) achieved nearly identical performance to Deeplab v3 + but only with about 1/6 parameters. Fused results revealed that PCM-PE repaired beams exhibited superior mechanical performance but inferior ductility compared to PCM-RN. Moreover, both PCM-PE and PCM-RN repaired beams demonstrated that preventive repairs achieved more balanced performance than post repairs. Consequently, utilizing PCM-RN for preventive repair emerged as an optimal candidate. This study significantly contributes to the utilization of waste fishing nets in coastal concrete structure maintenance.

Experimental study and numerical simulation of cellular I-beam manufactured using refill friction stir spot welding technology

The paper presents analyses of thin-walled I-beams constructed from 6061-T6 aluminum alloy using refill friction stir spot welding (RFSSW). A parametrized finite element model of the reference cellular beam was developed, and the results from numerical simulations and experiments were compared. Subsequently, the validated numerical model was utilized to conduct an in-depth analysis of three additional beams featuring distinct cross-sections. To assess the weld behavior, experiments were conducted on samples composed of two sheets connected by two spot welds. The outcomes of these investigations underscore the suitability of RFSSW as a method for constructing thin-walled structures in civil engineering applications.

ПАРАМЕТРИЧНЕ МОДЕЛЮВАННЯ НАПРУЖЕНО-ДЕФОРМОВАНОГО СТАНУ НЕСУЧОЇ КОНСТРУКЦІЇ ПРИЧІПНОГО ШИРОКОЗАХВАТНОГО ПОСІВНОГО КОМПЛЕКСУ ПРИ НАВАНТАЖЕННІ В РЕЖИМІ СІВБИ

On the basis of a parametric finite element model of the supporting structure of a trailed wide-grip sowing complex ATD 18.35, taking into account the mechanical properties of materials of metal structures, characteristics of dynamic effects in the sowing mode, the most dangerous combinations of loads for individual elements of the supporting structure are determined, recommendations for rational design are suggested. The calculated symmetrical scheme of the supporting structure with more than 600 constituent elements was loaded, including a possible asymmetric load. Data on the loading of the spatial frame of the supporting structure were previously obtained as a result of a wide field experiment carried out in the field.

Theoretical and Numerical Simulation Study on the Ultimate Load Capacity of Triangular and Quadrilateral Truss Structures

Spatial truss structures (STSs), serving as the bottom support structure of a cooling tower, effectively harness the superior load-bearing capacity offered by lattice-type truss structures. STSs are composed of main bars, diagonal bars, and horizontal bars, with horizontal bars serving as vital components of the truss structure. They play a pivotal role in maintaining the overall integrity and stability of the structure. The proportional relationship between the stiffness of each bar in STSs has a profound impact on the mechanical characteristics of the overall structure. This relationship directly influences the ultimate load-bearing capacity of the structure. Therefore, conducting research on the influence patterns of this relationship is of utmost importance. This paper explores the study of triangular truss structures (TTSs) and quadrilateral truss structures (QTSs). Firstly, through theoretical analysis, considering structural elements such as the stiffness of the horizontal bars, the number of layers in the truss, and the angle between the diagonal bars and the horizontal bars, theoretical expressions for the calculation of the ultimate load capacity of TTSs and QTSs are derived. Furthermore, a parametric finite element (FE) model was established for the TTSs and QTSs. Through numerical simulations, the validity of the theoretical calculation expressions was verified. Finally, this paper discusses the influence of factors such as the stiffness of the horizontal bars, the number of layers in the truss, and the angle between the diagonal and horizontal bars on the TTSs and QTSs. It analyzes the patterns and trends of these influences. The research results indicate that the theoretical and numerical simulation results for the TTSs have an error ranging from 0.40% to 4.93%, while the relative error for the QTSs ranges from 1.59% to 4.88%. These errors are within an acceptable range for engineering calculations. As the stiffness of the horizontal bars increases, the proportionality coefficient of the truss’s ultimate load capacity shows an initial increase followed by a stable trend. It reaches an equilibrium state when the stiffness of the horizontal bars reaches a certain threshold. As the number of layers in the truss and the angle between the diagonal and horizontal bars increase, the proportionality coefficient of the load capacity gradually decreases. The research findings provide a theoretical basis for the application of TTSs and QTSs in cooling towers.

Process parameter optimization for laser directed energy deposition (LDED) of Ti6Al4V using single-track experiments with small laser spot size

Single-track experiments are routinely used in the optimization of process parameters in additive manufacturing processes. Most of the process parameter optimization studies use a laser spot size of 1 mm or more. Since laser spot size affects the input energy density and in turn the efficiency of the deposition process, it is important to develop process maps every time a laser of different spot sizes is used. In this work, we determine the process maps for a laser of 0.6 mm spot size. By combining the process maps and the metallographic inspection, we estimate the optimum process parameters (laser power, scan speed, powder feed rate) for building Ti6Al4V components using powder-based laser-directed energy deposition(LDED). Single-tracks corresponding to 64 different parameter combinations are deposited. After eliminating the process parameter combinations resulting in defective tracks, the optimum process parameters of 300 W laser power and 720 mm min−1 scan speed is established by considering the relationship between the process parameters and the geometrical features of the deposit. The experimental results are then used to calibrate the modeling parameters of a three-dimensional finite element model for simulating the deposition process.

Coupled thermal-mechanical analysis of power electronic modules with finite element method and parametric model order reduction

This work presents a new approach for performing a parametric study and examining nonlinear material behaviours of a coupled thermal-mechanical model of a Power Electronics Module (PEM) by integrating the Finite Element Method (ANSYS-FEM) with Parametric Model Order Reduction (pMOR). The considered coupling method solves the thermal and structural models concurrently compared to the widely practised sequential coupling method. Instead of constant parameter values, which are generally regarded for pMOR studies, the temperature-dependent material properties of the wire material have been parametrised in the work using the pMOR method. A generalised 2D model has been regarded here for thermal-mechanical analysis with the pMOR approach, parametrising temperature-dependent coefficient of thermal expansion (CTE) and Young’s modulus (E) of the wire material to explore their impact on wire bonds. The matrix interpolation method has been applied here for the pMOR study, and PRIMA, a Krylov subspace-based model order reduction (MOR) technique, has been exercised for local model order reductions. A new efficient process of matrix interpolation, based on the Lagrange interpolation technique, has been developed to implement matrix interpolation in the parametric reduced order model (pROM). The local reduced order models (ROMs) have a degree of freedom (DOF) of just 8, compared to the full-order models’ (FOMs) of 50,602. The pROM provides an excellent solution and reduces computational time by 84% for the presented case.

Finite element simulation of axial crushing of flat and C-channel composite coupons using a modified mesomodel

The present article investigates the axial crushing behavior of IM7/8552 material system. Two types of specimens are considered-(a) flat coupons with saw-tooth trigger and (b) C-channels with 45° chamfer as a trigger. All the crushing test data (load, displacement and velocity history curves) is shared in the Crashworthiness working group (CWG) consortium of the Composite material handbook (CMH17.org). Flat crush coupons are tested at the University of Utah and the C-channels are tested at the John H. Glenn Research Center of the National aeronautics and space administration (NASA). Three types of layups are considered for flat coupons: QI1-[90/±45/0]2S, HL2-[902/02/±45/02] and HL3-[90/45/02/90/-45/02]. Two types of layups are considered for C-channels: HL2-[902/02/±45/02] and HL3-[90/45/02/90/-45/02]. Both the specimens are subjected to crush loading with an initial velocity and lumped mass attached to the impactor. All the ply and interface material properties come from the current authors' testing campaign except for strength and stiffness in the fiber direction. The crushing test cases are simulated in LS-Dyna software. Ply and interface behavior is described via user-defined material subroutines of LS-Dyna software. Each ply is modeled using 3D solid elements and the interfaces are modeled explicitly using cohesive elements. Intraply behavior is described using a novel modified meso model proposed by the present authors. Intraply model accounts for nonlinear damage, plasticity, ply fracture toughness and finite element mesh size. Interply response is modeled using bi-linear law. Predictions from present FE models showed a good correlation with crush test data. The effect of finite element model parameters e.g., filtering frequency, mesh size, interface properties, ply fracture toughness, element erosion criterion, contact stiffness and friction coefficient on crushing predictions is demonstrated by conducting parametric studies.

Kinematic-mapping-model-guided analysis and optimization of 2-PSS&1-RR circular-rail parallel mechanism for fully steerable phased array antennas

This paper presents a systematic methodology for analyzing and optimizing an innovative antenna mount designed for phased array antennas, implemented through a novel 2-PSS&1-RR circular-rail parallel mechanism. Initially, a comparative motion analysis between the 3D model of the mount and its full-scale prototype is conducted to validate effectiveness. Given the inherent complexity, a kinematic mapping model is established between the mount and the crank-slider linkage, providing a guiding framework for subsequent analysis and optimization. Guided by this model, feasible inverse and forward solutions are derived, enabling precise identification of stiffness singularities. The concept of singularity distance is thus introduced to reflect the structural stiffness of the mount. Subsequently, also guided by the mapping model, a heuristic algorithm incorporating two backtracking procedures is developed to reduce the mount's mass. Additionally, a parametric finite-element model is employed to explore the relation between singularity distance and structural stiffness. The results indicate a significant reduction (about 16%) in the antenna mount's mass through the developed algorithm, while highlighting the singularity distance as an effective stiffness indicator for this type of antenna mount.

Towards Structural and Aeroelastic Similarity in Scaled Wing Models: Development of an Aeroelastic Optimization Framework

The pursuit of more efficient transport has led engineers to develop a wide variety of aircraft configurations with the aim of reducing fuel consumption and emissions. However, these innovative designs introduce significant aeroelastic couplings that can potentially lead to structural failure. Consequently, aeroelastic analysis and optimization have become an integral part of modern aircraft design. In addition, aeroelastic testing of scaled models is a critical phase in aircraft development, requiring the accurate prediction of aeroelastic behavior during scaled model construction to reduce costs and mitigate the risks associated with full-scale flight testing. Achieving a high degree of similarity between the stiffness, mass distribution and flow field characteristics of scaled models and their full-scale counterparts is of paramount importance. However, achieving similarity is not always straightforward due to the variety of configurations of modern lightweight aircraft, as identical geometry cannot always be directly scaled down. This configuration diversity has a direct impact on the aeroelastic response, necessitating the use of computational aeroelasticity tools and optimization algorithms. This paper presents the development of an aeroelastic scaling framework using multidisciplinary optimization. Specifically, a parametric Finite Element Model (FEM) of the wing is created, incorporating the parameterization of both thickness and geometry, primarily using shell elements. Aerodynamic loads are calculated using the Doublet Lattice Method (DLM) employing twist and camber correction factors, and aeroelastic coupling is established using infinite plate splines. The aeroelastic model is then integrated within an Ant Colony Optimization (ACO) algorithm to achieve static and dynamic similarity between the scaled model and the reference wing. A notable contribution of this work is the incorporation of internal geometry parameterization into the framework, increasing its versatility and effectiveness.

A novel fiber‐reinforced polymer rope: Simulation and theoretical investigation

AbstractThe study proposed using twisted rope made of flexible fiber‐reinforced polymers (FRPs) instead of wire and synthetic ropes in high load‐bearing and corrosive environments. Finite element model verification and parameter analysis were conducted for the rope, along with deriving theoretical equations for its tensile properties. Increasing the lay length improved model accuracy, with a maximum bearing capacity within a 10% margin of error compared to experimental results. The model length had minimal impact on calculation results, while changes in radial mesh size (0.13 and 0.2 mm) and friction coefficient (0–0.2) greatly affected maximum contact stress. The tensile strength and elastic modulus of the strand remained almost constant (approximately 1142 MPa and 44 GPa) when the friction coefficient was altered. Increasing lay length (6D–20D) enhanced the tensile properties of the strand, whereas tendon diameter (1–3 mm) had negligible impact. Arranging inner and outer strands with the same lay length was better for circular ropes than those with the same lay angle. Inverse lay direction reduced rope torque and increased strand contact stress. Rectangular ropes had higher strength and modulus conversion efficiency, with lower contact stress compared to circular ones. The accuracy of rope equations improved with longer lay lengths, and adding a correction factor for lay length can modify the equation.Highlights A flexible FRP rope with high strength and twisted form was proposed. The effect of construction factors on the tensile behaviors of ropes was clarified. Equations for calculating the tensile properties of ropes were derived.

A finite element model for investigating the influence of keel design and position on unicompartmental knee replacement cementless tibial component fixation

ObjectivesThe cementless Oxford Unicompartmental Knee Replacement (OUKR) tibial component relies on an interference fit to achieve initial fixation. The behaviour at the implant-bone interface is not fully understood and hence modelling of implants using Finite Element (FE) software is challenging. With a goal of exploring alternative implant designs with lower fracture risk and adequate fixation, this study aims to investigate whether optimisation of FE model parameters could accurately reproduce experimental results of a pull-out test which assesses fixation. Materials and methodsFinite element models of implants with three methods of fixation (standard keel, small keel, and peg) in a bone analogue foam block were created, in which implants were modelled using an analytical rigid definition and the foam block was modelled as a homogenous linear isotropic material. The total interference and elastic slip were varied in these models and optimised by comparing simulated and experimental results of pull-out tests for two (standard and peg) implant geometries. Then the optimised interference and elastic slip were validated by comparing simulated and experimental data of a third (small keel) implant geometry. ResultsThe optimisation of parameters established an interference of 0.16 mm and an elastic slip of 0.20 mm as most suitable for modelling the experimental force–displacement plots during pull-out. This combination of parameters accurately reproduced the experimental results of the small keel geometry. The maximum pull-out forces from the FE models were consistent with experimental data for each implant design. ConclusionsThis study shows that experimental pull-out tests can be accurately modelled using adjusted interference values and non-linear friction and outlines a method for determining these parameters. This study demonstrates that complex problems in modelling implant behaviour can be addressed with relatively simple models. This can potentially lead to the development of implants with reduced risk of failure.

A general parametric finite element modeling and stress response analysis methods for pipeline system using the nonconforming solid element

In the dynamic topology optimization design of pipeline system, parametric finite element modeling (PFEM) is needed to improve the model reconstruction efficiency. Taking a typical spatial single pipeline as the research object, this paper innovatively presents a PFEM method of pipeline system based on the newly constructed nonconforming solid (Solid-NC) element. The stiffness and mass matrices of the spatial 8-node Solid-NC element with second-order boundary accuracy are obtained by introducing the node-free displacement items and statics condensation method. The PFEM method of the pipeline body is proposed by selecting the straight-line segment lengths as the pipeline shape control parameters. The PFEM method of the pipeline is described in detail, including the node coordinate solutions of straight-line and curved arc segments based on the direction vector method and vector decomposition method, respectively, and the simulation of the clamp mechanical properties considering the actual pre-tightening state of the clamp. Furthermore, the modal analysis is carried out, the node stress response solution is solved based on the stress smoothing method, and the effectiveness of the PFEM method is verified through experiment. Finally, the mesh quality and model reconstruction efficiency of the PFEM method is analyzed, the results show that the developed PFEM method has higher mesh quality and fast model reconstruction speed, and the model reconstruction time is shortened by 544.5 times at most compared with ANSYS software.

Uncertainty Factors of a Finite Element Model using the Fuzzy Analysis Method

The recent advancement in manufacturing technology in the automotive and aerospace sectors has led to the invention of advanced structured material, which is lightweight and a complex geometry model that can be manufactured. As it is related to human safety and hazards, the need for uncertainty analysis in a structure before and after a manufacturing process is a primary concern. Thus, this paper analyzes the uncertainty parameters of a meshed finite element model in the geometry, boundary condition, load, and material properties. An uncertainty analysis numerical tool, the fuzzy analysis method, is applied in Excel-VBA as the simulation platform. Each uncertainty parameter is in a range of numbers, with a maximum and minimum value as the limit. The α-cuts determine the fuzzy analysis output on the membership function. The deterministic value of the variable is implemented for comparison purposes. The simulation result for the von-Mises stress analysis has significantly impacted the uncertainty analysis as its curve has surpassed the yield strength limit of the material. The simulation output for the displacement has a more considerable uncertainty dispersion when compared to the other results. This study helps to find a better security margin of a structure for its sustainability in the future.

Sustainability-Driven Design of Aircraft Composite Components

The current prevailing trend in design across key sectors prioritizes eco-design, emphasizing considerations of environmental aspects in the design process. The present work aims to take a significant leap forward by proposing a design process where sustainability serves as the primary driving force. In this context, sustainability is positioned as a fundamental component to be integrated into the initial stages of design, introducing innovative multidisciplinary criteria that redefine the design paradigm. Within this framework, sustainability is characterized using a comprehensive and quantifiable index encompassing technological, environmental, economic, and circular economy dimensions. To demonstrate the practical application of sustainability as the primary criterion in designing mechanical components, a parametrized finite element model of a composite plate is utilized, integrating both pristine and recycled fibers. Subsequently, a demonstrator derived from the aviation industry—specifically, a hat stiffener—is employed as a validation platform for the proposed methodology, ensuring alignment with the demonstrator’s specific requirements. Various representative trade-off scenarios are implemented to guide engineers’ decision-making during the conceptual design phase. Additionally, the robustness of the aforementioned methodology is thoroughly assessed concerning changes in the priority assigned to each sustainability criterion and its sensitivity to variations in the initial data. The significance of the proposed design methodology lies in its effectiveness in addressing the complex challenges presented by conflicting sustainability objectives. Furthermore, its adaptability positions it for potential application across various sectors, offering a transformative approach to sustainable engineering practices.

Special IASS 2024_Parametric Analysis of “Zollinger Type” Ribbed Timber Shells

The following article presents the study and further development of the roof system developed and patented by Friedrich Zollinger in 1920. The so-called Zollinger construction system is based on short timber components - lamellae, connected by a bolt and a form of decking only for covering purpose. By developing the micro step joint, an increase in joint stiffness can be achieved. In addition, by applying and activating a load-bearing roof covering, a further increase in system stiffness can be achieved and demonstrated. Especially with regard to large spans, the increase of the stiffness and reduction of the deflection becomes inevitable against the background of an economic feasibility.Based on the analysis of the historic Zollinger system, it is possible to evaluate potential for improvements in terms of system stiffness as well as contemporary design, development and manufacturing. Due to the large number of different influencing factors, the system was modeled as a parametric master model. In this, a closed process cycle can be developed from the geometric definition, to the static analysis and to the derivation of the computer-aided manufacturing data.In the present study especially the exact recording, description and modeling of the stiffness and feasibility of the connection details "lamella-lamella" and "lamella-planking" was investigated. A parametric finite element model can be used to determine the stiffness parameters as a function of the fasteners used and the spacing of the fasteners. Staple connections are used as the main means of connection between the lamella and the planking. The implementation of the staple connections in the finite element analysis was carried out using spring parameters, which are determined in the course of the development.The analysis and optimization of the connection stiffnesses is presented against the background of an economical structure development. By using digital planning methods and interfaces, a contemporary way of working is presented. In addition, a contribution is made to digitalization in the construction industry.

Parameter Identification of a Large-Scale Vibroacoustic Finite Element Model with a One-Dimensional Convolutional Neural Network

Uncertainties are significant in the early vibroacoustic development, e.g., of a car body, to prevent costly modifications close to the start of production. First, engineers must know which uncertain parameters are sensitive: Our previous work identified 170 uncertain parameters being sensitive out of a complex finite element model with 1,300 uncertain parameters – a parameter reduction of approximately 87%. Second, engineers aim to find reliable distributions of these sensitive input parameters for finite element simulations. Finding these distributions is very demanding in a large-scale vibroacoustic model with several connecting parameters, as research already acknowledges regarding simplified connections. In this paper, we address this challenge with neural networks. For this, we use data in the frequency domain. Due to the curse of dimensionality, it is difficult to determine the parameter set of 170 parameters with a neural network. Therefore, we examine the influence of the number of parameters on the performance of neural networks. Furthermore, we train a fully connected feed-forward neural network and compare this to a one-dimensional convolutional neural network. The latter exhibits a better performance. Finally, we show how to determine distributions of the analyzed parameters based on artificial measurement data. Due to this process, we can significantly improve our finite element simulations and show how to deal with the challenge of determining uncertain parameters in a large-scale vibroacoustic finite element model based on data in the frequency domain.

Numerical investigation of a finite element abdominal wall model during breathing and muscular contraction

Background and ObjectiveVentral hernia repair is faced with high recurrence rates. The personalization of the diagnosis, the surgical approach and the choice of the prosthetic implant seem relevant axes to improve the current results. Numerical models have the potential to allow this patient-specific approach, yet currently existing models lack validation. This work extensively investigated a realistic finite element abdominal wall model including the implementation of muscle activation. MethodsA parametric 3D finite element model composed of bone, muscle and aponeurotic structures was introduced. Hyperelastic anisotropic materials were implemented. Two loading scenarios were simulated: passive inflation of the abdominal cavity to represent, e.g., breathing, and passive inflation followed by muscular activation to simulate other daily activities such as cough. The impact of the inter-individual variability (e.g., BMI, tissue thickness, material properties, intra-abdominal pressure (IAP) and muscle contractility) on the model outputs was studied through a sensitivity analysis. ResultsThe overall model predictions were in good agreement with the experimental data in terms of shape variation, muscles displacements, strains and midline forces. A total of 34 and 41 runs were computed for the passive and active sensitivity analysis respectively. The regression model fits rendered high R-squared in both passive (84.0 ± 6.7 %) and active conditions (82.0 ± 8.3 %). IAP and muscle thickness were the most influential factors for the selected outputs during passive (breathing) activities. Maximum isometric stress, muscle thickness and pre-activation IAP were found to drive the response of the simulations involving muscular contraction. The material properties of the connective tissue were essential contributors to the behaviour of the medial part of the abdominal wall. ConclusionsThis work extensively investigated a realistic abdominal wall model and evaluated its robustness using experimental data from literature. Such a model could improve patient-specific simulation for ventral hernia surgical planning, prevention, and repair or implant evaluation. Further investigations will be conducted to evaluate the impact of the surgical technique and the mechanical characteristic of prosthetic meshes on the model outputs.

Numerical analysis and design of concrete-filled wire arc additively manufactured steel tube under axial compression

Numerical investigation of the mechanical behaviour of concrete-filled wire arc additively manufactured (WAAM) steel tube under axial compression is presented in this paper. Typical structural performances of concrete-filled WAAM steel tube are extensively analyzed based on the experimental results firstly. FE models are established based on 3D models obtained by 3D laser scan technology, whilst the material anisotropy of WAAM steel tube is taken into account. The sensitivity study on the finite element (FE) model parameters is developed to assess their influence on the simulation results. The established FE models are verified against the test results demonstrating their effectiveness in predicting the structural behaviour of the concrete-filled WAAM steel tube. The composite action between the WAAM steel tube and inner concrete is analyzed through the validated FE models, indicating that it should be emphasized within the strain range from 0.003 to 0.01. The influences of the concrete and steel strengths are evaluated to investigate the confinement effect, showing that the concrete and steel strength exhibit a negative and positive impact on the confinement effect, respectively, and a positive correlation between the steel strength and biaxial stresses of the WAAM steel tube can be obtained. Finally, the design method of concrete-filled WAAM steel tube under axial compression, which considers the effect of the geometric undulations and material anisotropy of the WAAM steel tube, is proposed based on the theory of confining effect. The comparison results indicate that the proposed method can predict the axial compressive strengths of the concrete-filled WAAM steel tubes with reasonable accuracy.

Effects of dynamic and rigid implantation on biomechanical characteristics of different sagittal alignment lumbar after single- or double-level spinal fixations: a finite-element modeling study

BackgroundAlthough it is critical to understand the accelerated degeneration of adjacent segments after fusion, the biomechanical properties of the spine have not been thoroughly studied after various fusion techniques. This study investigates whether four Roussouly’s sagittal alignment morphotypes have different biomechanical characteristics after different single- or double-level spinal fixations.MethodsThe parametric finite element (FE) models of Roussouly’s type (1–4) were developed based on the radiological data of 625 Chinese community population. The four Roussouly's type models were reassembled into four fusion models: single-level L4–5 Coflex fixation model, single-level L4–5 Fusion (pedicle screw fixation) model, double-level Coflex (L4–5) + Fusion (L5–S1) model, and double-level Fusion (L4–5) + Fusion (L4–5) model. A pure moment of 7.5 Nm was applied to simulate the physiological activities of flexion, extension, lateral bending and axial rotation.ResultsBoth single-level and double-level spinal fixation had the greatest effect on lumbar range of motion, disc pressure, and annulus fibrosis stress in flexion, followed by lateral bending, extension, and axial rotation. In all models, the upper adjacent segment was the most influenced by the implantation and bore the most compensation from the fixed segment. For Type 2 lumbar, the L4–L5 Coflex effectively reduced the disc pressure and annulus fibrosis stress in adjacent segments compared to the L4–L5 Fusion. Similarly, the L4–L5 Coflex offered considerable advantages in preserving the biomechanical properties of adjacent segments for Type 1 lumbar. For Type 4 lumbar, the L4–L5 Coflex did not have superiority over the L4–L5 Fusion, resulting in a greater increase in range of motion at adjacent segments in flexion and extension. The difference between the two fixations was not apparent in Type 3 lumbar. Compared to the single-level Fusion, the changes in motion and mechanics of the lumbar increased after both the double-level Coflex + Fusion and Fusion + Fusion fixations, while the differences between two double-level fixation methods on adjacent segments of the four lumbar models were similar to that of the single-level fixation.ConclusionType 3 and Type 4 lumbar have good compensatory ability and therefore allow for a wider range of surgical options, whereas surgical options for small lordotic Type 1 and Type 2 lumbar are more limited and severe.

Seismic response of bridges employing knowledge-enhanced neural networks for the lumped plasticity modelling of RC piers

AbstractTo facilitate seismic analysis of bridges, especially on a regional scale, this study established a parametric finite element model of bridges incorporating simplified component elements. It employs a knowledge-enhanced neural network (KENN) to calibrate the parameters of the lumped plasticity model of pier columns. Along with a database of historical experimental results, the influence of the key characteristics of reinforced concrete columns on model parameters are investigated and formulated as physical laws to supervise KENN training. The developed KENN model was then developed, yielding root mean square errors within the range of [0.027, 0.209]. These errors are slightly larger than those of the purely data-driven neural network, yet the KENN model aligns more consistently with the physical principles. Further, to demonstrate its accuracy and efficiency, the proposed methodology was applied for the rapid seismic response analysis of typical bridges.