Transient Structural Response Research Articles

Analysis and evaluation of suitability of high-pressure dynamic constitutive model for concrete under blast and impact loading

Concrete demonstrates complex dynamic mechanical behaviors under the influence of blast or impact loads, and there are inherent limitations in experimental and theoretical methods when dealing with highly nonlinear problems. As computational technologies and mechanics continue to evolve, it is possible to conduct high-fidelity simulations of the transient response of concrete structures subjected to intense dynamic loads. Such simulations play a crucial role in revealing the propagation laws of stress waves, the progression of damage, the mechanisms of structural failure, and in conducting protective engineering design. An accurate concrete material model is essential for conducting numerical studies. This article reviews the development of high-pressure dynamic constitutive models for concrete in recent years from both experimental research and theoretical modeling perspectives, focusing on the analysis and evaluation of the modeling methods and main shortcomings of the equation of state(EOS), strength model, and damage model. Using single-element numerical simulations under a single loading path and numerical calculations of engineering cases under complex loading paths, a systematic analysis and comparison were conducted on the predictive capabilities of the HJC, RHT, KCC, and CSC models, as well as the newly developed Kong-Fang and Yan-Chen models. It pointed out the impact of high-pressure mechanical behavior of concrete and the cumulative effect of damage under hydrostatic pressure on the calculation results. Finally, a discussion was conducted on the inherent flaws, applicability, and research difficulties of local constitutive models of concrete in the finite element method. This provides a reference for the selection and research of constitutive models when conducting numerical analysis of the blast and impact resistance of concrete structures.

Effect of tilt angle on wind-induced vibration in pre-stressed flexible cable-supported photovoltaic systems

With the increasing adoption of mountainous photovoltaic installations, pre-stressed flexible cable-supported photovoltaic (PV) systems (FCSPSs) are becoming increasingly popular in large-scale solar power plants due to their evident adaptability to sloping terrain. The wind-induced deformation of FCSPSs significantly influences the wind field. In this study, a two-way fluid–structure interaction (FSI) analysis is conducted to assess the wind-induced vibration response of FCSPSs at various panel tilt angles. Firstly, the analysis approach for wind-induced vibration coefficients of FCSPSs is established, which involves model equivalency, coefficient definitions, model creation, and grid and solution settings. Secondly, the modal analysis is then conducted on FCSPSs at various panel tilt angles. Subsequently, the transient response of the PV structure and the variations in the wind field are evaluated by adjusting the panel tilt angles. Finally, a quantitative analysis is performed to investigate the influence of panel tilt angles on the support reaction and displacement wind-induced vibration coefficients of FCSPSs. The results indicate that the tilt angle has a certain impact on wind-induced vibration coefficients (reaction force, displacement). The effect of the tilt angle on the internal force wind-induced vibration coefficient is more pronounced. However, the variation in displacement due to wind-induced vibrations is significantly greater than the variation in internal force. Meanwhile, the displacement wind-induced vibration coefficient and the support reaction wind-induced vibration coefficient should be considered separately for different tilt angles.

Active control and prediction model for the dynamic shape of laminated plate/shell structures with piezoelectric actuators

This study establishes an active control and prediction model for the dynamic shape of laminated plates/shells with piezoelectric actuators. Firstly, transient responses of shell structures are numerically calculated by adopting the finite element method (FEM) and the Newmark formulae, then the Kuhn-Tucker equation is utilized to get the time-varying voltage values with a minimum shape control error. Subsequently, a backpropagation neural network (BPNN) is constructed to predict the control precision for cases with different piezoelectric actuator layouts. Finally, the proposed control model is demonstrated through numerical examples with a maximum relative control error of only 0.023% for a given desired shape and the average error of the prediction model with 98 input neurons is 18%, thereby satisfying the application requirements. Furthermore, for a model with 3870 degrees of freedom and 21 discrete time points, the computational time is reduced significantly from 8.24 s to 0.002 s through the prediction model, making it highly suitable for optimization problems by utilizing heuristic algorithms.

Toward Deep Generation of Guided Wave Representations for Composite Materials

Laminated composite materials are widely used in most fields of engineering. Wave propagation analysis plays an essential role in understanding the short-duration transient response of composite structures. The forward physics-based models are utilized to map from elastic properties space to wave propagation behavior in a laminated composite material. Due to the high-frequency, multi-modal, and dispersive nature of the guided waves, the physics-based simulations are computationally demanding. It makes property prediction, generation, and material design problems more challenging. In this work, a forward physics-based simulator such as the stiffness matrix method is utilized to collect group velocities of guided waves for a set of composite materials. A variational autoencoder (VAE)-based deep generative model is proposed for the generation of new and realistic polar group velocity representations. It is observed that the deep generator is able to reconstruct unseen representations with very low mean square reconstruction error. Global Monte Carlo and directional equally-spaced samplers are used to sample the continuous, complete and organized low-dimensional latent space of VAE. The sampled point is fed into the trained decoder to generate new polar representations. The network has shown exceptional generation capabilities. It is also seen that the latent space forms a conceptual space where different directions and regions show inherent patterns related to the generated representations and their corresponding material properties.

Transient Structural Thermo-Mechanical Response of Multi-Layered Viscoelastic Composite Laminates with Non-Idealized Interfacial Conditions Based on New Fractional Derivatives

Multi-Layered viscoelastic composite laminates are commonly designed as damping structures in non-isothermal environments to avoid unnecessary vibration and ensure the safety of structures working in vibration engineering, such as reducing the unwanted vibration and noise of aircraft structures and vehicles. In recent years, there have been extensive research works that contributed to evaluate and predict the influences of relaxation time parameters, nonlocal elastic/thermal parameters, and temperature related material properties on the dynamic thermo-viscoelastic responses of such structures. Nevertheless, the effects of fractional derivatives and related parameters are rarely reported on this topic. This paper aims to construct a mathematical model of transient structural thermo-mechanical response of multi-layered viscoelastic composite laminates with non-idealized interfacial conditions (i.e., the thermal contact resistance and elastic wave impedance) by introducing the new definitions of the Caputo-Fabrizio (CF), Atangana-Baleanu (AB), and Tempered-Caputo (TC) fractional derivatives. The Laplace transform method is applied to obtain the transient solutions. The dimensionless results reveal that the new fractional derivatives, non-idealized interfacial conditions and material constants ratios significantly affect the wave propagations and transient thermo-viscoelastic responses, and the harmful heat/stress isolation at interface are improved to some extent.

Investigation of a perturbation-based model updating approach for structural health and event monitoring

With the intention to detect structural events, for example, occurrence of damage and assessing their severity under service, structural health and event monitoring proved itself as a reliable evaluation tool. While many algorithmic approaches exist, model-based monitoring offers the prominent advantage to enable extensive analysis of damage states based on a structural digital twin. In order to accurately replicate the dynamical behaviour of a real-world structure, inherent physical properties, for example, mass, stiffness and structural damping, of the digital twin might be corrected from nominal values. This can be achieved by numerical model updating procedures. In this study, the application of a model updating approach is presented to eliminate modal discrepancies. Based on the perturbated modal dynamic residual, an updating equation is formulated. Stiffness and mass correction terms with preserved orthogonality and symmetry conditions are determined by the method of least squares. A case study using computationally generated modal data is conducted, evaluating the numerical updating performance in terms of correction accuracy and reproduction of modal parameters. Finally, the transient structural response to an impulse excitation is compared between updated and reference model. The gathered results prove the method’s suitability as accurate and robust updating procedure, fostering its application in model-based monitoring frameworks.

N-sided polygonal cell-based smoothed finite element method (nCS-FEM) based on Wachspress shape function for modal analysis

In this article, an n-sided polygonal cell-based smoothed finite element (nCS-FEM) based on the Wachspress shape function is formulated for free and forced vibration of solid structures. Cell-based smoothing domains are constructed in n-sided polygonal element mesh. Using the gradient smoothing technique, the computation of the strain-displacement matrix requires only the value of the Wachspress shape function, not the derivatives of the shape function or the mapping relationship. The Lanczos algorithm is used to solve eigenvalue problems that produces vibration modes of a given structure, and the vibration modes and modal superposition techniques are used to obtain transient dynamic responses of structures subjected to arbitrary dynamics forces. The nCS-FEM is applied to solve a number of solid structures for modal analysis and compared with the Polygonal FEM, nES-FEM and ABAQUS, it is found that nCS-FEM has high precision, high efficiency and super convergence.

A novel efficient method for transient heat analysis of cylindrical periodic structure based on the physical features and group theory

In this paper, a novel efficient and accurate numerical method is developed for analyzing the transient temperature responses of cylindrical periodic structures. By exploiting the structure’s circumferential cyclic periodic property and leveraging group theory, a circumferential decomposition strategy is presented to transform the temperature response analysis of the cylindrical periodic structure into the analyses of a series of one-dimensional periodic structures. Then, based on the physical nature of the transient heat conduction, an axial decomposition strategy is developed to convert the computations of the temperatures of these one-dimensional periodic structures into the calculations of the temperatures of a series of small-scale structures. The computational cost of these small-scale structures is further reduced by using the group theory. Several numerical examples demonstrate that the proposed method has higher accuracy and computational efficiency in comparison with the Crank-Nicolson method. When the Crank-Nicolson method attains the acceptable results, the proposed method is about 10 and 20 times faster than the Crank-Nicolson method with direct and preconditioning conjugate gradient solvers, respectively.

Transient response of pavement structures under moving wheel loads using the ALE methodology

AbstractThe dynamic response of long structures (e.g., pavements) subjected to moving loads is generally difficult to simulate using conventional methods like the finite element method in the Lagrangian setting. This is because the entire length of the structure in the path of the moving load would need to be discretized, and in turn would require large meshes. Additionally, if improvement in quality of results through the use of finer mesh sizes is sought, the entire region of the mesh in the load path would require refinement. As a direct result, long simulation run‐times can be expected when using conventional methods. To overcome these drawbacks, and improve the efficiency of the finite element simulations, the Arbitrary Lagrangian Eulerian (ALE) approach can be used to simulate pavement structures, provided longitudinal homogeneity is assumed. This contribution uses an extension of the quasi‐static ALE framework to the transient domain, enabling the study of the dynamic response of pavement structures subjected to moving loads. In this work, some case studies are considered to highlight the capabilities of this dynamic ALE framework.

Refined Analysis of the Transient Temperature Effect during the Closing Process of a Cross-Sea Bridge

In order to study the transient temperature effect during the construction of a cross-sea bridge off the coast, based on the Hong Kong-Zhuhai-Macao Bridge-Pipe Bridge Crossing Cliff 13-1 Gas Field, a refined analysis was conducted and the prediction of transient temperature gradient and structural response was carried out under the conditions of strong solar radiation and atmospheric convection using the method of combining theoretical research and numerical simulation. Firstly, the partial differential equation of uniform heat flux density on the outer surface of the main girder under the action of solar radiation and atmospheric convection was established. The equation was realized by calculating the solar radiation intensity and the comprehensive heat transfer coefficient, as well as fitting the atmospheric temperature on the outer surface of the main girder, and the equivalent comprehensive temperature at any time on the main girder was obtained. Secondly, a numerical analysis model of the heat conduction of the main girder section was established, and the equivalent comprehensive temperature was input into the numerical model as the temperature field boundary to solve the transient temperature gradient of the section, and the result was verified in comparison with the measured data. Finally, the transient temperature gradient was applied to the girder, and the temperature effect of the main girder during the closing process was also calculated. Construction control measures were also discussed. The research results show that the predicted value of the transient temperature gradient is consistent with the measured value (the maximum deviation is less than 2 °C), and the predicted value is slightly larger than the measured value, which makes the structure safer. During the closing process, the temperature gradient of the main girder has obvious non-linear characteristics: the temperature gradient is relatively high within 0.4 m of the top surface of the roof while tending to zero outside 0.4 m. The best closing time for the main girder is from 21:00 in the evening of the closing day to 6:00 a.m. the next day. For the small angles at both ends of the closure segment during the best closing time, temporary adjustment jacks and temporary counterweights can be adopted to eliminate the small angles at both ends of the closure segment in order to facilitate the welding construction and meet the smoothness requirements of bridge alignment.

Electromechanical coupling enriched finite element method for dynamic characteristic of piezoelectric materials structures

To improve the application depth and breadth of intelligent unit devices made from piezoelectric structures, their kinetic properties shall be urgently studied. Herein, based on the basic equations and boundary conditions of piezoelectric materials, an interpolation coverage function of node displacement was introduced into the displacement shape function and potential shape function of coupling electromechanical finite element method (FEM), forming an electromechanical coupling enriched FEM generalized shape function. Together with the variation principle, an electromechanical coupling enriched FEM was put forward, and its motion equations were deduced. Next, the free vibration and transient response of the piezoelectric structure were analyzed, and the accuracy and validity of the new method were validated with numerical cases. Results show this method has high application prospects for analyzing the dynamic properties of piezoelectric material structures.

A coupled computational framework for the transient heat transfer in the typical pyrotechnic device

Propellant combustion in pyrotechnic devices produces high-temperature, high-pressure gas. The component is moved by high-pressure gas, which subsequently impacts the energy absorber and causes it to compress and deform. The temperature difference between the high-temperature gas and the wall causes transient heat transfer. Propellant combustion, transient heat transfer, and structural response are coupled, but previous studies had to independently analyze them. Therefore, a multi-physical field numerical model is developed based on the commercial software ABAQUS in this paper, which couples energetic material combustion, transient heat transfer, and structural response. In the user subroutine VUAMP, a lumped-parameter model is used to predict the parameter distribution of combustion products. This determines the load applied on the thin-walled tube and the boundary conditions of transient heat transfer. In ABAQUS, the transient heat transfer and structural response are investigated by the direct thermo-dynamic coupling method. The coupling effect between multiple physical fields is realized by real-time parameter exchange. The rationality and accuracy of the coupling model are verified by comparison with the experiment. The results show that the coupling model can effectively simulate the complex coupling process after considering the transient heat transfer and the interaction between multiple physical fields. Taking a pyrotechnic device as the research object, the pressure load accuracy obtained by the coupled model is improved by 5.1%, and the structure response obtained is also closer to the experiment result. At the same time, more characteristic parameters of the structure field and temperature field are obtained.

An analytical solution method for transient response of truss-type space frame structures

An analytical solution method for transient response of truss-type space frame structures

Can transient simulation efficiently reproduce well known nonlinear effects of jointed structures?

Although joints are omnipresent in engineering structures, their proper consideration in simulations is still a challenging area of research. This is because joints introduce local nonlinearities which lead to load and preload-dependent resonance frequencies and damping, mode coupling, high variability of contact area and contact pressures. The knowledge about those phenomena has been gathered via systematic experimental testing. A meaningful digital or virtual replication of such tests would require a transient numerical time integration, where besides all dynamic effects, the local and fine discretized nonlinear contact and friction forces in the joint also need to be considered. The Finite Element Method can only provide this theoretically since the necessary computation times make practical use almost impossible. Newer methods, where the joint deformation is represented via so-called contact modes instead of nodal degrees of freedom, offer a perspective for transient virtual tribomechadynamics. This paper is devoted to the following question: Is it possible for the first time to numerically reproduce real experiments with low computing times so that the previously mentioned nonlinear effects can be observed? In this work the transient numerical response of a jointed structure due to different loads (sine sweep, sine, step and impulse) is evaluated and related to measurements. The application of the Hilbert Transform to the time data, as known from measurements, reveals load and preload dependent eigenfrequency and damping. Other measured phenomena like mode coupling, a high variability in the contact area and resulting contact force can also be observed numerically. The results are in good qualitative agreement with the experiments. This work proves the principal capability of virtual tribomechadynamics as an efficient complement to real testing for gaining deeper insight. All the powerful measurement methods can directly be applied to simulated data.

Coupling Modal Analysis with the BEM for the Transient Response of Bar Structures Interacting with Three-Dimensional Soil Profiles

Coupling Modal Analysis with the BEM for the Transient Response of Bar Structures Interacting with Three-Dimensional Soil Profiles

Effect of Topology on Transient Dynamic and Shock Response of Polymeric Lattice Structures

Effect of Topology on Transient Dynamic and Shock Response of Polymeric Lattice Structures

Analysis of random wind-induced response of isolation structure with viscoelastic damper and TMD

The analysis method of wind vibration response of the seismically isolated structure with viscoelastic damper and tuned mass damper(TMD) under Davenport wind load was studied systematically. Firstly, using the general integral models of viscoelastic dampers to establish the exact dynamic integral-differential response equations in original structural space for isolated structure with general linear viscoelastic damper and TMD. Then, adopting the transfer function method to obtain the exact non-orthogonal modal superposition solution in original structural space for the displacement response standard deviation and the equivalent wind force transient response in the time domain of the isolated structure with viscoelastic damper and TMD under wind loading. These exact solutions can accurately discover the vibration properties of viscoelastic dissipative structures. That is, the dissipative structural modes are not orthogonal, the dynamic equations cannot be decoupled with the structural modes, while transient structural response can be accurately represented as an individual superposition of modal responses. The analysis of the calculation example showed that the isolated structure with viscoelastic damper and TMD can more effectively reduce the actual values of wind-induced displacement response standard deviation, equivalent wind vibration force and design value of equivalent wind. Since the results obtained in this paper are exact solutions, it can provide a theoretical basis for the design of the structures with viscoelastic damper and TMD, the optimization of damper and TMD parameters.

Photoinduced Ultrafast Transition of the Local Correlated Structure in Chalcogenide Phase-Change Materials.

Revealing the bonding and time-evolving atomic dynamics in functional materials with complex lattice structures can update the fundamental knowledge on rich physics therein, and also help to manipulate the material properties as desired. As the most prototypical chalcogenide phase change material, Ge_{2}Sb_{2}Te_{5} has been widely used in optical data storage and nonvolatile electric memory due to the fast switching speed and the low energy consumption. However, the basic understanding of the structural dynamics on the atomic scale is still not clear. Using femtosecond electron diffraction, structure factor calculation, and time-dependent density-functional theory molecular dynamic simulation, we reveal the photoinduced ultrafast transition of the local correlated structure in the averaged rocksalt phase of Ge_{2}Sb_{2}Te_{5}. The randomly oriented Peierls distortion among unit cells in the averaged rocksalt phase of Ge_{2}Sb_{2}Te_{5} is termed as local correlated structures. The ultrafast suppression of the local Peierls distortions in the individual unit cell gives rise to a local structure change from the rhombohedral to the cubic geometry within ∼0.3 ps. In addition, the impact of the carrier relaxation and the large number of vacancies to the ultrafast structural response is quantified and discussed. Our Letter provides new microscopic insights into contributions of the local correlated structure to the transient structural and optical responses in phase change materials. Moreover, we stress the significance of femtosecond electron diffraction in revealing the local correlated structure in the subunit cell and the link between the local correlated structure and physical properties in functional materials with complex microstructures.

Dynamic response of fractionally damped two-layered viscoelastic plate

The vibration response of the plates attached with the free viscoelastic damping layer is investigated to predict the performance of free surface damping treatment. The frequency-dependent dynamic properties of the viscoelastic layer are expressed by fractional Kelvin-Voigt model. A simple and efficient identification approach based on the gradient-based optimization principle is employed to evaluate the viscoelastic model parameters from the experimental data. Both classical and fractional Kelvin-Voigt models are employed to describe the viscoelasticity, and the corresponding model parameters are identified. Further, the application of these identified parameters in the modeling and analyzing of real viscoelastic composite structures is demonstrated through quantitative examples. Step load-induced transient responses of the viscoelastic structures modeled using the classical and fractional model parameters are investigated and compared, to demonstrate the consequences of unknowingly using the classical Kelvin-Voigt model. The effects of the viscoelastic layer thickness on the transient response of the two-layered plate are also studied.

Asymptotic analysis of the transient response of a thermoelastic assembly involving a thin layer

We study the transient response of a thermoelastic structure made of two tridimensional bodies connected by a thin adhesive layer. Once more we highlight the powerful flexibility of Trotter's theory of approximation of semi-groups of operators acting on variable spaces: considering the geometrical and physical characteristics of the thin layer as parameters, we are able to show in a unitary way that this situation leads to a huge variety of limit models the properties of which are detailed. In particular, according to the relative behaviors of the different parameters involved, new features are evidenced such as the apparition of an added specific heat coefficient for the interface or of additional thermomechanical state variables defined not only on the limit geometric interface but on its cartesian product by any interval of real numbers.