Finite Element Model Of Structure Research Articles

Bayesian finite element model updating with a variational autoencoder and polynomial chaos expansion

The quantification of uncertainty in civil structures poses a significant challenge in contemporary research due to the substantial computational demands involved. This study introduces an innovative approach for updating the finite element model (FEM) and quantifying uncertainties in civil structures through the synergistic use of variational autoencoder (VAE) and polynomial chaos expansion (PCE). Within this framework, the unknown parameters inherent to the structural FEM are represented as latent variables and can be effectively inferred through the VAE. These latent variables are modeled using a multivariate Gaussian distribution. In the proposed methodology, the PCE serves to approximate the log-likelihood function associated with the latent variables, facilitating the derivation of the analytic expression for the variational lower bound. By maximizing this variational lower bound, both the mean and standard deviation can be readily determined. To assess the accuracy and computational efficiency of the proposed technique, numerical analyses are performed on a cantilever beam and a steel pedestrian bridge. Furthermore, the effectiveness of the proposed approach is validated through its application to damage identification within a benchmark model. Significantly, the results indicate that the proposed method offers superior computational efficiency compared to the conventional VAE approach. Notably, the findings reveal that employing a high-order PCE is unnecessary; rather, a low-order PCE suffices for precise parameter identification. Consequently, the proposed methodology necessitates only a limited dataset for training to ascertain the PCE coefficients, thereby enhancing its practical applicability and efficiency.

Study on prefabricated composite shear wall cladding anti-shedding connection structure

Fabricated steel structure systems have undergone significant advancements. However, problems associated with exterior wall panel systems have become increasingly prominent, particularly the issue of exterior wall panel shedding. Three full-scale fabricated composite shear wall exterior panel components were designed and tested under quasi-static conditions. The failure sequence and characteristics of the exterior wall panels at different displacement angles, including their out-of-plane displacement and stiffness degradation, were evaluated to assess their seismic and connection performance in different building construction methods. The results indicated that drilling holes near the centre of autoclaved lightweight concrete (ALC) boards improved the seismic performance of wall panels. Long round holes in the ALC boards allowed the dissipation of sliding energy during the initial deformation of wall panels. Furthermore, wall panels with bonded anchorage connections for rockwool boards exhibited better seismic performance than those with pure anchorage connections. To verify the accuracy of the findings, a structural finite element model was established, and the influences of various parameters, such as the position of ALC board connecting bolts, length of ALC board holes, and bonding rate of rockwool boards, on the stress and deformation of the exterior wall panel system were analyzed. Based on the test results and finite element simulation analysis, an anti-shedding connection construction method was proposed.

Synergy of LIDAR and hyperspectral remote sensing: health status assessment of architectural heritage based on normal cloud theory and variable weight theory

Architectural heritage health assessment is the basis of scientific repair and maintenance. However, existing methods do not adequately take into account the fuzziness, randomness and uncertainties unique to architectural heritage assessment. In this paper, a new evaluation model of VM-NCM is constructed by combining variable weight theory and normal cloud model theory. The model enables the combination of qualitative ratings and quantitative calculation, deals with the fuzziness in the assessment process, and resolves the randomness and reflects the uncertainty to a certain extent. Based on constructing the index system combining qualitative and quantitative indexes, the structural index values are acquired by the synergistic coupling of the fine laser point cloud model and finite element structural analysis model. The acquisition of surface index values is completed by the hyperspectral intelligent detection technology of surface materials and diseases. These reduce the generation of ambiguous information in the index detection process. An evaluation study is conducted using the Yingxian wooden pagoda in China as an example. The results show that this method takes into account the fuzziness and randomness in the evaluation process, and obtains more scientific and reliable evaluation results, which provides a research paradigm for assessing the architectural heritage health status.

Research on Quantification of Structural Natural Frequency Uncertainty and Finite Element Model Updating Based on Gaussian Processes

During bridge service, material degradation and aging occur, affecting bridge functionality. Bridge health monitoring, crucial for detecting structural damage, includes finite element model modification as a key aspect. Current finite element-based model updating techniques are computationally intensive and lack practicality. Additionally, changes in loading and material property deterioration lead to parameter uncertainty in engineering structures. To enhance computational efficiency and accommodate parameter uncertainty, this study proposes a Gaussian process model-based approach for predicting structural natural frequencies and correcting finite element models. Taking a simply supported beam structure as an example, the elastic modulus and mass density of the structure are sampled by the Sobol sequence. Then, we map the collected samples to the corresponding physical space, substitute them into the finite element model, and calculate the first three natural frequencies of the model. A Gaussian surrogate model was established for the natural frequency of the structure. By analyzing the first three natural frequencies of the simply supported beam, the elastic modulus and mass density of the structure are corrected. The error between the corrected values of elastic modulus and mass density and the calculated values of the finite element model is very small. This study demonstrates that Gaussian process models can improve calculation efficiency, fulfilling the dual objectives of predicting structural natural frequencies and adjusting model parameters.

Seismic Response Analysis of Steel Structure Isolation System Under Long-Period Seismic Motion

To analyze the seismic response of steel structure isolation systems under long-period seismic motion, a 9-story steel frame building was selected as the subject. Five steel structure finite element models were established using SAP2000. Response spectrum analysis was conducted on the seismic motion to determine if it adhered to the characteristics of long-period seismic motion. Modal analysis of each structural model revealed that the isolation structure significantly prolonged the structural natural vibration period and enhanced seismic performance. Base reactions and floor displacements of various structures notably increased under long-period seismic motion compared to regular seismic activity. Placing isolation bearings in the lower part of the structure proved more effective under long-period seismic motion. In seismic design engineering, it is essential to consider the impact of long-period seismic motion on structures and the potential failure of isolation bearings.

Experimentally validated numerical prediction of laser welding induced distortions of Al alloy parts for railcar body by inherent strain method combined with thermo-elastic-plastic FE model

A laser welding with wire filler feeding was developed to replace traditional arc welding process for joining aluminium alloy railcar body components. A three-dimensional (3D) thermo-elastic-plastic finite element (FE) model was applied to compute the plastic strains of weld zone in a downsized aluminium alloy plate with butt-joint, T-joint and fillet-joint configurations, respectively, combined with corresponding experimental validations. The achieved plastic strains at the weld zone were then input as inherent strain loadings into elastic structural FE model of fully sized aluminium alloy railcar body components to predict the welding induced distortion with the experimentally measured out-of-plane distortions. The experimentally validated FE model was then further applied for optimizing the inverse pre-deformation of plates to counteract the welding induced deformation, finally to mitigate the welding distortion issues.

Research on Simulation Technology of Excitation Response of Aircraft Structural Based on Finite Element Model in Flutter Flight Test

To simulate excitation response of the aircraft structural of flutter test aircraft under different excitation methods. A simulation method for excitation response of flutter flight tests based on finite element models has been proposed. This method is based on the finite element model of the aircraft structure. Establish aerodynamic and excitation force models for flutter flight tests. Obtain a simulation model for the excitation response of aircraft flutter flight tests. Solve the model and simulate various excitation methods for flutter flight tests. Firstly, a detailed introduction was given to the excitation modeling method for aircraft flutter flight tests, including two excitation models: external excitation and control surface excitation. Then, the finite element model of the structural dynamics of a single wing with ailerons is taken as the research object. Establish a single wing flutter flight test excitation response model. Implemented simulation of control surface sweep excitation, control surface pulse excitation, and small rocket excitation. The feasibility of this method has been verified. Finally, based on the finite element model of the entire aircraft, a flutter flight test excitation response simulation model was established. We have conducted analysis and research on sensor position optimization, excitation method optimization, excitation response amplitude prediction, and flutter boundary prediction. And the simulation optimization analysis results were compared with the flight test results. Analyzed the promoting effect of flutter flight test excitation response simulation on flight tests.

A novel damage identification method based on acceleration response sensitivity and finite element model updating: Numerical and experimental

The utilization of time-domain data for structural damage diagnosis and finite element model updating has several benefits, such as direct implementation of the measured data with no requirement for domain changing and susceptibility to structural damages. This study introduces a straightforward sensitivity relation for the measured acceleration response, avoiding the requirement for computational techniques like direct differentiation methods. The proposed equation establishes a linear relationship between variations of the structural parameters and structural responses. The proposed sensitivity equation operates at the level of improved equations and exhibits greater accuracy compared to the current approaches. The numerical evaluation of the proposed sensitivity equation on two offshore jacket platforms reveals the accuracy of the proposed method. Additionally, an experimental case study to examine the efficacy and validation of the introduced sensitivity relation in real-world settings demonstrates the procedure’s viability. The numerical and experimental results reveal the accuracy of the proposed sensitivity equation.

An efficient Bayesian method with intrusive homotopy surrogate model for stochastic model updating

AbstractThis paper proposes a new stochastic model updating method based on the homotopy surrogate model (HSM) and Bayesian sampling. As a novel intrusive surrogate model, the HSM is established by the homotopy stochastic finite element (FE) method. Then combining the advanced delayed‐rejection adaptive Metropolis–Hastings sampling technology with HSM, the structural FE model can be updated by uncertain measurement modal data. The numerical results show that the updating effectiveness of the proposed method is better than that of the Bayesian methods with the non‐intrusive surrogate models, such as stochastic response surface model and Kriging model. Compared to the Bayesian method with the intrusive second‐order perturbation model, the updating results of the proposed method are more accurate, especially when the fluctuation of the uncertain measured data is large and the stiffness of the structure significantly changes. The model updating results of a cable‐stayed bridge show that the statistic modal properties of the updated bridge model have a very good agreement with the uncertain measurement modal data.

Multi-physics and multi-objective optimization of a permanent magnet-assisted synchronous reluctance machine for traction applications

This contribution addresses the rotor design process of a Permanent Magnet-assisted Synchronous Reluctance Machine by adopting a multi-physics and multi-objective optimization algorithm. A Finite Element (FE) approach is employed to determine the electromagnetic and structural responses during the optimization. In particular, a detailed FE structural modeling is used, which often is based on simplifications and inaccuracies in the available literature. A genetic algorithm is adopted, with the objectives being the maximization of the mean torque, the minimization of the torque ripple and the minimization of the stress in the rotor. A parametric analysis of the geometric features precedes the optimization to establish the design variables which mostly affect the machine performance, and thus to reduce the computational cost of the optimization. The presented methodology consists of a useful tool for the final stages of the design process, and provides a rotor with a torque ripple reduced by 15.1% compared to an existing design used as a benchmark, while the mean torque and the maximum stress remain the same as the original configuration.

Working mechanism evaluations of full-scale joints with bolted-cover plate connection for modular steel buildings

The force-reliability of the modular structural joints is crucial for ensuring the structural integrity of modular steel buildings. However, the welds connecting the beam and column within the module are susceptible to tear during seismic events. This mode of failure greatly undermines the ability of these joints to withstand seismic forces. Four full-scale modular structural joints with bolted-cover plate connection were designed and conducted for seismic performance testing, emphasizing the significance of methods such as reinforcing diagonal braces and strengthening flanges on the protective effect of beam–column welds in the module. The simplified modular structural joint and frame finite element model were proposed based on experimental data, refined finite element modeling, and theoretical analysis. The findings suggest that the seismic behavior of the modular structural joint remains unaffected by variations in axial compression ratio within the designed range of parameters. The beam–column weld of the module in the reinforced joint exhibits almost no weld tearing, and both strengthening methods demonstrate exceptional capacity for energy dissipation. The proposed simplified modeling method facilitates the efficient determination of the modular structural joint bearing capacity and the lateral stiffness of the modular frame. The research findings presented in this paper can serve as a valuable reference point for the engineering design of modular steel structures.

Origami-Wrapped Structures with Corrugated Unfolded Forms

Stowage schemes based on origami wrapping patterns are useful for the design of various deployable spacecraft structures. These origami patterns allow for the compact stowage of flat sheets of small thickness. Typically, some other structure is needed to stiffen this thin sheet when it is fully deployed and flat. This paper describes a class of thin-shell structures that can be compactly stowed using origami wrapping methods but have a corrugated form when deployed. These structures cannot reach a flat state by design. The persistent corrugations provide stiffness without the need for an external structure, thus leading to overall savings in mass and complexity. The geometrical design of the corrugations is highly tunable. This paper describes a method for generating the form of these folding structures; the method guarantees that the structure can be unstrained both when compactly wrapped and when fully deployed. Test articles are fabricated to demonstrate the concept, and stowage experiments and stiffness experiments are conducted. A structural finite element modeling procedure is described to predict the deployed stiffness of these structures, and the stiffness predictions match the experimental results.

Numerical modelling and investigation of CFS built-up stud walls in fire

Cold-formed steel (CFS) stud walls with the studs made of BC (built-up back-to-back CFS channel) and NC (built-up nested CFS channel) members are likely to be utilised in many applications in CFS building structures. However, the knowledge and understanding related to the thermal and structural behaviour of these improved CFS stud walls under fire exposure and their FRLs (fire resistance levels) are still limited. Although standard fire tests of real-sized walls could show the behaviour and FRL of some BC and NC stud walls, their results are limited because of their high cost and time-consuming nature, and are applicable to only the tested configurations. In this study, thermal and sequentially coupled structural finite element models were established. The validation of these models was achieved using the standard fire test results of real-sized BC, NC and channel stud walls. Later, parametric investigations based on the established models were undertaken to investigate the behaviour and FRLs of load-bearing BC, NC and channel stud walls with or without cavity insulation under varying load ratios. The outcomes from these investigations clarified the superiority of cavity insulated NC stud walls. Details of this study and its outcomes are presented in this paper.

SEISMIC BEHAVIOR OF MULTI-STORIED RC BUILDING WITH RE-ENTRANT CORNER

Nowadays, buildings often feature irregular floor plans for functional, aesthetic, or economic reasons. Constructing earthquake-resistant structures in seismic areas, especially with irregular shapes like re-entrant corners, poses challenges. Such corners are common when maximizing limited space is a priority. In earthquakes, re-entrant corners in structures pose major vulnerabilities, causing stress concentration and torsion problems. The main aim of this paper is to develop finite element structural analysis models of 10, 12, and 15-storied L-shaped RC buildings with a re-entrant corner under different seismic zones using equivalent static analysis (ESA) and response spectrum analysis (RSA). This research also focuses on the overall behavior of analysis results (story drift, overturning moment, base shear, etc.) with the influence of re-entrant corner. It also investigates the performance of columns and beams near re-entrant corners as the number of stories increases in different seismic zones. For the current study, ETABS V19 is used. Models consider seismic, dead, and live loads. The Bangladesh National Building Code (BNBC) 2020 is used to examine the equivalent static analysis (ESA) and the response spectrum analysis (RSA) methods. It has been concluded from the study that re-entrant corner beams consistently exhibit the highest bending moments and torsion levels across all seismic zones. Similarly, re-entrant corner columns consistently demand the most axial force and rebar when compared to similar column types. Furthermore, the study identifies maximum stress levels in re-entrant corner slabs across all seismic zones.

Investigation of the Influence of Contact Patterns of Worm-Gear Sets on Friction Heat Generation during Meshing

Friction losses and scuffing failures are interesting research topics for worm gears. One of the factors leading to scuffing is the heat generated in the contact of gear teeth. The contact geometry of worm gears is complex, leading to high friction between contact surfaces. High friction between contact surfaces during operation generates heat friction that causes the occurrence of scuffing, which in turn determines the scuffing load capacity. To analyse the thermal characteristics of a worm-gear pair and the thermal behaviour of contact teeth, a direct-coupled thermal–structural 3D finite element model was applied. The heat flux due to friction-generated heat was determined on the gear tooth to investigate thermal characteristics and predict transient temperature fields. This study permits an in-depth understanding of the temperature fields and the friction heat generation process. Also, better control of the contact pattern between worm-gear teeth would decrease friction heat and increase scuffing load capacity. This paper investigates the transient thermal behaviour among different pinion machine setting parameters that can result in an optimal tooth-contact pattern that produces a lower temperature field, thus achieving higher transmission efficiency.

Finite-volume micromechanics-based multiscale analysis of composite structural model accounting for elastoplastic and ductile damage mechanisms

A hierarchical homogenization framework is proposed for nonlinear elastic-plastic and damage simulation of a unidirectional composite laminate. Proper scale transition rules between the macro- and the micro-scale variables were introduced, wherein the finite-element and finite-volume methods are employed for predicting the structural and material point response, respectively. Specifically, at the macroscopic scale, the ABAQUS/CAE structural analysis provides macroscopic strains for the lower-scale unit cell simulation (top-down) at each load increment. Reversely, at the microscopic scale, the unit cell problem is modelled using extended parametric finite-volume direct averaging micromechanics (FVDAM) through a Meta-UMAT subroutine that links the global finite element solver and the constitutive laws (UMAT subroutines). Homogenization of stresses and effective stiffness tensor obtained from the unit cell predictions is passed back to the ABAQUS/CAE for the higher-scale finite-element structural model computation (bottom-up). The stresses and strains at the global and local scales can be tracked during the incremental loading on the macroscopic structures through continuous homogenization and localization. The predictive capabilities of the proposed technique are verified vis-à-vis the experimental response of the Boron/Aluminum (B/Al) laminate obtained from off-axis tensile and shear loading available in the literature.

Predictive maturity of non-linear concrete constitutive models for impact simulation

This paper explores the concept of predictive maturity for non-linear concrete constitutive models employed in the computational prediction of the structural response of reinforced concrete structures to impact from free-flying missiles. Such concrete constitutive models are widely varied in complexity. Three constitutive models were utilized within the same finite element structural model to simulate the response of the IRIS III experiment. Each of the models were individually calibrated with available material testing data and also re-calibrated assuming limited availability of test data. When full calibration is possible, more sophisticated constitutive models appear to provide more predictive maturity; however, when this data is not available (e.g. for an existing structure where representative test specimens may not be available), the expected maturity is reduced. Indeed, this hypothesis is supported by the simulations that indicate good agreement with measured experimental response quantities from the IRIS III tests with complex constitutive models and full calibration, and accordingly poor predictions when less complex models are used or when the more sophisticated models are poorly calibrated. Thus, predictions of structural response where complete material testing data is not obtainable should be understood as less predictive.

A computational model for structural dynamics and reconfiguration of DNA assemblies

Recent advances in constructing a structured DNA assembly whose configuration can be dynamically changed in response to external stimuli have demanded the development of an efficient computational modeling approach to expedite its design process. Here, we present a computational framework capable of analyzing both equilibrium and non-equilibrium dynamics of structured DNA assemblies at the molecular level. The framework employs Langevin dynamics with structural and hydrodynamic finite element models that describe mechanical, electrostatic, base stacking, and hydrodynamic interactions. Equilibrium dynamic analysis for various problems confirms the solution accuracy at a near-atomic resolution, comparable to molecular dynamics simulations and experimental measurements. Furthermore, our model successfully simulates a long-time-scale close-to-open-to-close dynamic reconfiguration of the switch structure in response to changes in ion concentration. We expect that the proposed model will offer a versatile way of designing responsive and reconfigurable DNA machines.

Structural Health Monitoring Design and Performance Evaluation of a Middle-Span Bridge

Structural health monitoring (SHM) has attracted significant attention over the past two decades due to its ability to provide real-time insight into the condition of structures. Despite the development of several SHM systems for long-span bridges, which play a crucial role in the assessment of these structures, studies focusing on short- or middle-span bridges remain scarce. This research paper presents an efficient and practical bridge monitoring and warning system established on a middle-span bridge, a key crossroad bridge located in Shenzhen. The monitoring system consists of sensors and measuring points that collect a substantial amount of data, enabling the close monitoring of various operational indicators to facilitate the early detection of threshold exceedances. Based on this system, the subtle condition of the bridge can be evaluated, and the operational condition of the bridge can be studied through the comparative analysis of the collected data. Over four months of monitoring, data including the strain and creep of the main beam, the strain and settlement of piers and the crack width of the bridge body are observed. Furthermore, the real-time operational status of the bridge is analyzed and evaluated through the combination of the collected data and the structural finite element model.

The Analysis of Permanent Magnet Vernier Synchronous Machine Vibration and Noise

The permanent magnet vernier synchronous machine (PMVSM) has the characteristics of high torque density and high power density and has advantages in the field of low-speed and high-torque applications. The PMVSM utilizes rich harmonics for torque enhancement, but it can also cause an increase in radial electromagnetic force and vibration noise. In this paper, we take a 12-slot 10-pole PMVSM as an example to analyze the source of radial electromagnetic force, vibration and noise. The electromagnetic finite-element model and structural finite-element model of the PMVSM are established for calculation. Through the analysis and calculation of two-dimensional electromagnetic fields, the radial electromagnetic force distribution of the PMVSM is obtained. We derive the radial electromagnetic force formula of the PMVSM and verify the correctness of the formula through harmonic analysis of the radial electromagnetic force. The sources of radial electromagnetic forces at various orders and frequencies within the PMVSM are analyzed and summarized by coupling the radial electromagnetic force obtained from the electromagnetic finite-element model to the structural finite-element model and conducting electromagnetic vibration harmonic response analysis on the PMVSM. The measured acceleration spectrum of the prototype is compared with the finite-element method (FEM) results, verifying the correctness of the finite-element simulation results for electromagnetic vibration.