Computers & Structures最新文献

In this work, a novel GPU-accelerated heterogeneous method for the automated multilevel substructuring method(HAMLS) is presented for dealing large finite element models in structural dynamics. Different parallel modes based on node, subtree, and eigenpair have been developed in the solution steps of AMLS to achieve a heterogeneous strategy. First, a new data management method is designed during the model transformation phase to eliminate the determinacy race in the parallel strategy of the separator tree. Considering the distribution characteristics of the nodes in the separator tree and the dependence of node tasks, a load balancing heterogeneous parallel strategy is designed to take full advantage of hosts and devices. By developing an adaptive batch processing program for solving eigenvectors during the back transformation phase, the overheads of launching kernels, as well as the GPU memory requirements, can be reduced by several orders of magnitude. Several numerical examples have been employed to validate the efficiency and practicality of the novel GPU-accelerated heterogeneous strategy. The results demonstrate that the computational efficiency of the novel strategy using one GPU can increase to 3.0x that of the original parallel AMLS method when 16 CPU threads are used.

Concrete with new features such as high strength and a high tension–compression ratio has been developed to enhance building safety and the defense structure capability, which also poses a challenge to classical constitutive models such as the Holmquist-Johnson-Cook (HJC) model.

This study proposes a flexible constitutive model that is suitable for concrete-like materials with varying strength and tension–compression ratios. Known as the three-invariant model, it features the explicit introduction of two mechanical characteristic parameters: the tension–compression ratio and the Lode angle. By strictly passing through (or closely approximating) six benchmark stress state points, the model effectively captures tension–compression anisotropy and yield behaviors across the entire range of hydrostatic pressure. To further extend the static model to dynamic conditions, a unified S-type strain rate equation is developed. This equation accounts for dynamic tension–compression anisotropy arising from the material’s intrinsic properties by considering the influence of hydrostatic pressure on strain rate effects. Experimental data from various rock and concrete specimens subjected to true triaxial stress states are compared with calculated data. The results confirm that the proposed model accurately reflects the yield strength and improves the predicted accuracy of structural responses under complex stress states.

A comprehensive strategy combining theory and experiment is proposed to characterize the dynamic coupling induced shifts of vehicle and bridge frequencies through both experimental investigation and numerical validation, in which the effect of vehicle-bridge interaction is theoretically incorporated in the vehicle-scanning method based on the experimental model. It is known that the measurement of bridge frequencies plays an important role in structural health monitoring as the shift of frequency can be served as an indicator of possible damage occurring in a bridge. Nevertheless, the attention has been mainly drawn on the accuracy improvement in developing the vehicle-scanning method so far, with limited discussion of dynamic coupling effect on the frequency shifts. As such, a combined theoretical–experimental approach is presented to show that the influence of vehicle-bridge interaction results in the coupled frequencies of a vehicle-beam system using the vehicle-scanning method, and adopting a heavy lumped test vehicle can lead to the underestimated bridge frequency and overestimated vehicle frequency. As a new finding, the effect of rolling frequency is experimentally observed in the vehicle spectrum for the first time.

This work is concerned with the development of new fourth-order accurate explicit time integration methods for the solution of wave propagation problems discretized by the finite element method. These novel schemes are derived from the well-known Central Difference time integration method through a proposed time substep procedure formed by either two or three complex substeps. The proposed formulation follows a different approach of standard time integration methods in the sense that results in the time domain are complex numbers, and advantages of such a distinct feature and its relation to the error are presented and discussed. A numerical analysis reveals that the proposed formulation not only enhances the stability but also increases the accuracy when compared to the classical Central Difference method; besides, the computer implementation is very straightforward. Finally, numerical examples are presented and the results are compared with the corresponding ones from other fourth-order methods in order to demonstrate the effectiveness, robustness and potentialities of the proposed formulation.

This paper introduces a computational approach for inferring the minimum requirements for the nondestructive inspection of subsurface delamination in outdoor concrete structures using passive infrared thermography (IRT). The non-linear numerical system was solved using the Finite Element Method (FEM). Complete verification and validation of the numerical model were performed through the analysis of experimental and computational errors, as well as through the comparison of computational outputs of thermal gradients with the contrast values measured in an experiment with solar radiation and passive IRT. The results of accuracy and precision of the computational simulation approach were found to be adequate, from a practical perspective, for the intended use of the model, with the thermal gradient values having an uncertainty of 0.080 ± 0.91 °C and -0.016 ± 0.91 °C for the concrete slab and column sample, respectively. Furthermore, the developed model was used to perform a one-year analysis of the studied case, in order to determine the approximate radiative heat flux required to identify defects with different size-to-depth (S/D) ratios in various concrete components with distinct solar exposures. Finally, the relationship between the calculated radiative heat flux and thermal contrast with the respective environmental variables in place was analyzed graphically.

The advantages of the multiresolution finite wavelet domain method in terms of convergence speed and solution localization capabilities have been demonstrated in dynamic simulations of one- and two-dimensional solids. The first step in the multiresolution procedure entails a coarse solution, which is subsequently enriched by the calculation of finer solutions, so convergence is achieved without discarding the previous results obtained at coarser resolutions. In this work, the multiresolution structure of the method is thoroughly explored to develop two novel convergence indicators which can provide error indices for the first two steps of the process and focus the fine solutions on specific subregions, enhancing accuracy and computational speed. The first convergence indicator is based on force residuals and the second relies on the maximum ratio of the fine to total solution. Detailed examination of the multiresolution components results in profound comprehension of the way they participate to the total solution. Based on repeated observations, it is deduced that the participation of fine components to the total solution constitute metrics of convergence, permitting the termination of the hierarchical analysis without requiring convergence checks. The proposed convergence indicators can guide targeted refinement techniques and may provide the basis for a new computational paradigm.

In this paper, a nonlinear analytical model is presented for the low-velocity collision impact of a sandwich plate with auxetic honeycomb-core layer. The auxetic feature of the honeycomb material is realized by mathematically expressing the effective material coefficients in terms of material property and cellular geometric parameters through a homogenization method. The higher order shear deformation theory, the von Kármán nonlinearity theory, and a modified Hertz contact law which accounts for the contact pressure distribution and indentation effect, are employed to establish the kinematic relations. The Newmark time integration scheme in conjunction with the direct iterative method is utilized to establish a solution procedure for the nonlinear dynamic governing equation. The verification of the presented model with the data in published literatures is carried out, followed by a series of numerical analyses for influences of cellular geometric features and impactor’s initial conditions (such as impactor’s initial velocity, mass, and nose curvature radius) on the nonlinear dynamic response. The results of numerical analyses show that the geometric features of the unit cell in the honeycomb-core and impactor’s initial conditions can cause significant influences on the nonlinear collision impact behaviors of the system.

The Method of Fundamental Solution (MFS) for the thin plate resting on the Winkler-Pasternak elastic foundation under dynamic loading is proposed in this work. In traditional MFS, the double-source method is utilized with two free variables including the locations of source pint. In order to construct MFS with few free parameters, the main aim of this paper is to deduce two fundamental solutions for a concentrated force and a dipole of thin plate resting on the elastic foundation with damping by Laplace transform technique. The behaviours and performances of fundamental solutions are observed comprehensively. Time domain numerical results are obtained by the Durbin’s inverse method and the behaviours of fundamental solutions are observed comprehensively. The main novelty of this paper is the derivation of Laplace transformed fundamental solutions of the dipole of a Kirchhoff plate resting on the Winkler-Pasternak elastic foundation with the damping factor and comparisons have been made between Kirchhoff plate and Reissner/Mindlin plate theories under dynamic loadings. In order to show the accuracy of this methodology, numerical comparisons between the present work and either analytical solutions or finite element solutions are presented. Excellent agreements with both analytical solution and finite element method solution are observed.

This paper presents a new radial basis function-based stiffness evaluation procedure developed in the framework of nonlinear, and non-intrusive reduced-order modeling. For structural nonlinear systems, a stiffness evaluation procedure (STEP) and its variants use a cubic polynomial for evaluating nonlinear stiffness coefficients and have been developed as non-intrusive reduced-order models (ROM) using data obtained from numerical simulation model. In this paper, we propose using a radial-basis function (RBF) instead of the cubic polynomials on evaluating nonlinear stiffnesses. As the RBF shows a good performance for approximating nonlinearities, the efficiency and robustness of the ROM are substantially enhanced in a non-intrusive manner. In particular, the proposed R-STEP ROM can be constructed for elastoplastic analysis without any additional treatments. Various numerical examples verify the performance of the proposed R-STEP ROM comparing with the STEP methods and commercial finite element software, ABAQUS.

This study presents a robust contact constitutive model in the distinct element method (DEM) framework for simulating the mechanical behavior of masonry structures. The model is developed within the block-based modeling strategy, where the masonry unit is modeled as deformable blocks with potential crack surfaces in the middle of the bricks, while the mortar joints are defined as zero-thickness interfaces. The modeling strategy implements multi-surface plasticity with damage mechanics, including a tension cut-off, Coulomb failure criterion, and an elliptical compressive cap for the damage in tension, shear, and compression, respectively. Two new features are introduced in this contact model: a piecewise linear softening function for strength degradation in tension and shear and a hardening/softening function to phenomenologically define the compressive damage of masonry composite into the unit-mortar interface. The constitutive model is implemented in commercial DEM software using the small displacement configuration and validated against material and experimental tests on masonry walls subjected to constant pre-compression and monotonically increasing in-plane load. The experimental and numerical results regarding the force-displacement relationship and damage pattern produced by the proposed constitutive model are compared and critically discussed, demonstrating the capability of DEM coupled with the suitable constitutive law in simulating the behavior of masonry structures.