Computers & Structures最新文献

Structural dynamics systems are represented by discretized partial differential equations, whose solutions depend on various parameters. Developing high-fidelity numerical models for multi-dimensional systems or those with multiple parameters can be computationally expensive, particularly if the systems are non-linear. Consequently, the concept of a precalculated library of the system's response to a wide range of parameters is appealing. Thus, a global non-linear space-frequency solver is proposed that produces a low-rank representation of the solution using Modal Basis analysis known as the Harmonic Modal Hybrid Method. The DEIM is also used to accelerate its convergence by creating a reduced basis of the non-linear function(s) based on either calculated or experimental values. The optimized solver is then employed for rapid offline computations to construct surrogate models that can give real-time predictions of the parametrized dynamic response using the sPGD technique. These models serve as building blocks for virtual twins that necessitate near-instantaneous calculations when the system parameters and/or conditions are changed. A proof of concept is illustrated by using this technique to analyze a well-known non-linear system, the cantilevered beam with a non-linear cubic spring attached to its end. This method can be easily extended to solve other dynamical systems quickly and effectively.

In this paper, we propose a novel computational formulation capable of solving the problem of material softening and the emerging localisation of strains in spatial frame-like structure, a common phenomenon for brittle heterogeneous materials. This study adopts the embedded strong discontinuity approach within our original velocity-based framework. The velocity-based formulation is thus enhanced with additional capabilities of detection of critical load level and critical cross-section and introduction of the jump-like variables at the level of velocities and angular velocities to enable more realistic description of strain localisation. A modified consistency condition is derived using the method of weighted residuals in complete accordance with the theoretical concept of strong discontinuity. One of the key advantages of the proposed method is its computational efficiency, which is preserved even after detecting cross-sectional singularities and handling post-critical localised strains. The numerical examples show the effectiveness and robustness of the proposed approach.

A stabilized peridynamic correspondence material model for axisymmetric problems (SPD-CMM-A) is proposed in this work to effectively simulate the ablation and ductile fracture behaviors of metals under high temperatures. To quantify the damage resulting from compression and shearing deformations, a strain energy density decomposition method is incorporated into the ductile damage model. Furthermore, a novel axisymmetric stabilization method based on peridynamics linearization theory is introduced to mitigate numerical oscillations arising from zero-energy modes in both thermal and mechanical scenarios. To capture the varying geometries and update the boundary conditions during ablation, a moving boundary model is developed based on temperature-associated criteria. To validate the capacity of the proposed SPD-CMM-A, several representative numerical experiments are conducted. These examples not only affirm its ability to stabilize numerical oscillations in coupled axisymmetric thermoplastic problems but also demonstrate its capability for accurately simulating ablation and predicting crack propagation.

Bolted steel to laminated bio-based material connections experience significant performance challenges due to the nonlinear response and high stress concentrations at their joints. This paper introduces an innovative 3D plasticity-fracture continuum Finite Element (FE) model that significantly advances the simulation of such truss joints by integrating Hill's yielding criteria with an element removal methodology for fracture simulation. This novel approach captures both plastic and fracture behaviors simultaneously, a capability not sufficiently addressed in existing models. We detail the theoretical framework for these models, including the derivation of constitutive equations and the algorithms necessary for their implementation in ABAQUS. Additionally, it is provided a low-fidelity modeling of truss joints, offering a comprehensive analysis of connector elements, joint models, and parametric modeling via Python scripting. The model's efficacy is demonstrated through identification of connection and of hybrid planar trusses under cyclic loading, which validates the practical applicability of the method. To optimize computational efficiency, we developed a Parallel Genetic Algorithm (PGA) that integrates seamlessly with ABAQUS and Python to facilitate parameter calibration. This integration not only enhances the model's accuracy but also reduces computational load, making it feasible for complex engineering applications. Our findings illustrate a significant improvement in modeling accuracy and efficiency, establishing a robust methodology for analyzing truss joints in bio-based construction materials.

In recent years, increasingly complex computational models are being built to describe physical systems which has led to increased use of surrogate models to reduce computational cost. In problems related to Structural Health Monitoring (SHM), models capable of handling both high-dimensional data and quantifying uncertainty are required. In this work, our goal is to propose a conditional deep generative model as a surrogate aimed at such applications and high-dimensional stochastic structural simulations in general. To that end, a conditional variational autoencoder (CVAE) utilizing convolutional neural networks (CNNs) is employed to obtain reconstructions of spatially ordered structural response quantities for structural elements that are subjected to stochastic loading. Two numerical examples, inspired by potential SHM applications, are utilized to demonstrate the performance of the surrogate. The model is able to achieve high reconstruction accuracy compared to the reference Finite Element (FE) solutions, while at the same time successfully encoding the load uncertainty.

The article presents a novel strain-based finite element family for the analysis of material softening of planar frame structures. In our case, the softening zone is described by a discrete crack, which is considered as an ‘excluded’ finite element point, i.e., the deformation quantities in the crack are considered separately from the deformation quantities of the element. They are connected to the element only through kinematic quantities, used to describe the crack opening. The criterion for crack initiation is defined as the limit axial-bending resistance of the cross-section. The advantage of the presented model is that it is not necessary to define cracks or softening zones in advance and that the solution is mesh-independent in the sense that no further densification of the mesh is needed purely on account of capturing material softening. The accuracy and efficiency of the presented finite element family is illustrated by the example of a clamped–simply supported concrete beam and a portal concrete frame. The examples demonstrate that even with a minimum number of finite elements of suitable accuracy, sufficiently accurate results are obtained for normal engineering practice.

The Gurson-Tvergaard-Needleman (GTN) model has been improved to extend its application for high strain rate loading and assessed by using the Taylor impact process of 7xxx aluminum alloys. The existing modification method based on independent shear damage variables has been integrated into the enhanced GTN model to assess shear fracture. In addition, the effects of strain rate hardening, temperature softening, and viscosity resistance terms have been taken into account in the constitutive equation to accurately depict the material’s deformation behavior under high strain rates. A series of quasi-static mechanical tests and Split Hopkinson Pressure Bar (SHPB) tests with strain rates ranging from 1000$s^{-1}$ ∼ 5000 $s^{-1}$ were conducted on 7A52-T6 alloy and 7A62-T6 alloy. The Taylor impact experiments showed that the mushrooming deformation and shear fractures occurred as the impact velocity increased. Both the 7A52 and 7A62 alloys exhibited fracture characteristics of shear and void nucleation, and the voids only grew slightly after formation. The predicted fracture patterns in Taylor impact and the evolution trend of material strength using the enhanced GTN model are consistent with the experimental results.

Traditionally, nonprobabilistic methods for reliability problems evaluate the reliability level of single failure modes, lacking the capability to perform comprehensive reliability analysis series–parallel systems formed by multiple failure modes. In this paper, the nonprobabilistic systematic reliability method (NSRM) is proposed to evaluate the reliability of series–parallel systems within the nonprobabilistic framework. Firstly, the correlation propagation analysis is introduced to quantify the ellipsoidal uncertain domain of limit state functions, upon which all subsequent reliability analyses are based. Subsequently, an equivalence-based method based is proposed to determine the equivalent limit state functions of parallel subsystems, accompanied by the establishment of an optimal equivalence strategy. The NSRM is further established by combining the second order reliability bound techniques. Lastly, the paper presents two numerical examples and an engineering application, showcasing the efficacy and precision of the proposed NSRM in practical scenarios.

During the in-orbit service, mesh reflector antennas inevitably withstand the long-term creep behavior, resulting in changes in material properties and loss of cable tensions, thus decreasing the structural stiffness and surface accuracy. Pretension design plays an important role for mesh reflector antennas in achieving high surface accuracy, and different levels of pretension also affect the antenna’s creep behavior in the time dimension, which can be actively utilized to improve stability of the antenna surface accuracy. In this paper, we present an anti-creep pretension determination method for mesh reflector antennas to improve the surface accuracy stability. The creep model in the discretized time domain is adopted to describe the cable creep behavior. The time-related nonlinear equilibrium equation of the mesh reflector antenna is established with the force density method. The time-related tangent stiffness matrix is derived and adopted to solve the nonlinear equilibrium equation by the Newton-Raphson method, providing an effective way to analyze the antenna creep phenomenon in the discretized time domain. Aiming to minimize the long-term peak value of the time-variant surface error, the pretension schemes are generated and optimized. Finally, this approach is effectively applied to a thirty-unit mesh reflector antenna and its feasibility and effectiveness are verified.

Regular monitoring of the hanger system is essential for preserving structural integrity in tied-arch bridges. This proactive monitoring enables preventive maintenance and early detection of hanger damage. To confront this issue, we propose a novel scanning method for assessing the impact of damaged hangers on the dynamic behaviour of single-span tied-arch railway bridges. Using each hanger as a positional reference, this method employs an instrumented vehicle as a mobile scanner to indirectly acquire vibration data from the traversed bridge deck. The hybrid approach integrates vehicle-bridge interaction (VBI) dynamics, vehicle scanning method (VSM), and moving windowed Fourier transform (mw-FT) technique to generate time–frequency spectrograms from the collected signals. In this representation, the time axis indicates the duration of the inspection vehicle traversing the bridge deck. By analysing frequency shifts within the spectrogram, we can identify damaged hangers through observed variations in frequency content over time. Numerical studies demonstrate the efficacy of the proposed hybrid vehicle scanning technique in detecting potential hanger damage in tied-arch railway bridges.