The Euler equation is one of the fundamental equations describing fluid motion in Computational Fluid Dynamics, and the existence of discontinuous solutions poses challenges in constructing numerical algorithms for solving this type of equation. To achieve high-resolution numerical results for the Riemann problem of the two-dimensional Euler equation, this paper constructs a pressure-difference adaptive rotating entropy stable scheme. Utilizing the rotating invariance of the equations, the normal vector outside the boundary is decomposed into two orthogonal components, and an entropy stable scheme is implemented in each directions. The determination of the components of the two components relies on the rotation angle. In this paper, a pressure function is introduced to adaptively adjust the rotation angle of the scheme based on local pressure variations. The resolution of the entropy stable scheme is enhanced by introducing the adaptive rotation angle. Numerical examples show that the numerical results obtained by this scheme exhibit good symmetry and high resolution.

Research on acoustic propagation in multiple fluids has important application values in naval architecture and ocean engineering, such as sound propagation in pipelines filled with water and air, and the detection of buried objects. There are two difficulties in solving such problems with the use of the classical finite element method: one is the serious numerical dispersion error in the finite element solutions under medium and high wave numbers; the other is the need to use refined mesh grids to discretize the fluids near the coupling interface. These difficulties lead to a large computational cost for the finite element method, and the manual intervention to generate refined grids. Compared with the finite element method, the weak-form meshfree method does not require traditional grids, and the dispersion error effect in its solution is much weaker, ensuring good computational accuracy and efficiency. However, the meshfree shape functions are usually discontinuous in the problem domain, resulting in the inability of the continuity condition of the acoustic particle velocity to be naturally satisfied on the interface. Therefore, this paper uses the penalty function method to reconstruct the continuity condition of the acoustic particle velocity on the interface, and proposes a Galerkin weak form suitable for meshfree methods for sound propagation in multiple fluids. Numerical analysis shows that the meshfree solutions is consistent with the reference solutions, and the computational accuracy and efficiency of the meshfree method can be higher than the finite element solutions.

A simple numerical implementation method is proposed for the Chaboche-type viscoplastic constitutive model coupled with Lemaitre anisotropic damage theory. Using the decoupled algorithm, the damage tensor is updated based on the forward difference format at the beginning of each incremental step. The damage tensor is considered as a constant in the discretization process of the constitutive equations. Based on the hypothesis of strain equivalence, the formulations containing only partial tensors are constructed in the effective deviatoric stress space, and the radial return process is simplified to solve a nonlinear scalar equation concerning the accumulated plastic strain increment. The numerical implementation method and the derivation of consistent tangent operator are provided based on the Voigt notation scheme. The comparison between the experimental data and the simulation results of isotropic scalar damage model under uniaxial and multiaxial stress states validates the effectiveness and high computational efficiency of this method. Numerical results under different time step sizes also indicate the good accuracy and stability.

Structural condition assessment is crucial for ensuring the safe services of structures, with structural damage detection (SDD) being a core component. In this paper, a novel SDD method is proposed based on the adaptive grasshopper algorithm and sparse regularization. It aims to tackle accuracy decline of SDD results and instability involving uncertainties and incomplete measurement, thereby achieving sparse-regularization-based structural condition assessment. Firstly, adaptive Lévy flight and elite opposition-based learning strategies are incorporated into the adaptive grasshopper algorithm to prevent the SDD process from falling into local optima and to enhance the stability of SDD results. Secondly, a modal parameter-based objective function with sparse regularization is formulated to increase the sparsity of SDD results, thereby improving SDD accuracy and robustness. The optimization results of competition-based evolutionary computation benchmark functions show that the adaptive grasshopper algorithm exhibits better global convergence and identification stability compared with its standard version. Numerical and experimental results for simply-supported beams indicate that the proposed method can ensure reliable SDD accuracy even in the case of incomplete measurements, and it possesses good noise robustness as well.

The formation of porous media is influenced by a number of factors, including the deposition and fragmentation of particles, which result in the formation of interlayers with varying structures. These interlayers exert a significant influence on the mechanical behavior of porous media. This paper presents a systematic investigation into the influence of the inclination angle and thickness of the interlayer on the mechanical behavior of porous media, employing the discrete element method. The results demonstrate that the stress intensity of porous media containing interlayers is between those of the two homogeneous porous media and varies with changes in the inclination angle and thickness of the interlayers. The average coordination number between grains is found to be significantly affected by the thickness of the interlayer at the beginning of loading, but stabilized at the end of loading. The variation of the coordination number affects the distribution of strong and weak force chains, while the inclination angle and thickness of the interlayer determine the magnitude and direction of stress transfer in the force chains. Furthermore, the contact unit normal force and normal contact force are deflected with the increase of the inclination angle of the interlayer, demonstrating significant anisotropy. This study advances our understanding of the intricate mechanical behavior of porous media containing interlayers in strata, offering invaluable insights for optimization and practical application in geological engineering.

This paper presents an analytical method, namely interface stiffness transfer method, for evaluating the responses of multilayered elastic structures. Based on the Love function and general solutions, the stiffness matrix relationship of the displacement-stress state vectors is introduced to obtain the interface stiffness transfer matrix equation between adjacent layers, which satisfies an algebraic Riccati matrix equation. When the elastic layer is a half-space, an explicit solution is obtained directly for the interface stiffness matrix. The interface stiffness transfer matrix method starts from the bottom layer with a known stiffness, and then deals with one layer at a time until the uppermost layer is reached, obtaining the interface stiffness of the multilayered structure. Finally, by solving the symmetric equilibrium equations of the boundary conditions, the displacement-stress state vector of an arbitrary layer is obtained. This method keeps the advantages of the classical transfer matrix method, but naturally excludes its exponential growth terms. In particular, the proposed method is a powerful candidate for efficiently solving the algebraic Riccati equation for the optimal control problems. Numerical examples show the properties of the interface stiffness transfer method.

This paper presents a Bezier triangle meshing method that considers both clipped and non-clipped forms for a single NURBS surface. The proposed method is applied to analyze isogeometric Kirchhoff-Love shell structures. The process begins by interpolating NURBS surfaces into Bezier surfaces. Subsequently, the topological relationship between the clipping curve and each parameter node is calculated within the parameter domain. A Bezier contour curve set is then generated in the parameter domain by selecting points along the clipping curve. Utilizing this contour curve set, a triangular mesh is generated in the parameter domain. Finally, the Bezier triangle mesh in the physical domain is created through a mapping method. The adaptability and robustness of the algorithm are verified through three models, and the mesh quality is assessed. The results demonstrate favorable overall mesh quality. Building upon this foundation, the paper illustrates the application of a rotation constraint between Kirchhoff-Love shell elements, using the penalty function method with Scordelis-Lo's Roof shell model as an example. The accuracy of Kirchhoff-Love shell elements based on Bezier triangles is subsequently validated.

Small cross-sections of boundary elements easily induce the “internal tension” phenomenon of steel plate shear walls, making it difficult to fully utilize the seismic performance of buckling-restrained steel plate shear walls. The design of cross-sections of boundary elements is related to their internal force requirements, and analyzing the internal force requirements of boundary columns is meaningful. Based on the proposed buckling-restrained steel plate shear wall with multi-concrete panels (MBRSPSW), the analytical expressions for the internal force of the boundary column of the MBRSPSW were theoretically derived in this paper. Combined with the experimental research on the buckling-restrained steel plate shear wall horizontally assembled multi-concrete panels (H-MBRSPSW), its numerical model was established and verified. The internal force distributions of the boundary column obtained from numerical analysis and analytical calculation were further compared. The research results indicate that the inner steel plates in the MBRSPSW are divided into constrained regions and unconstrained regions. The axial force, shear force, and bending moment distributions of the boundary column from the analytical calculation results agree with those from the numerical analysis results, and the internal force calculation expressions of the boundary column are correct. The research results can provide a reference for the design of this category of steel plate shear walls.

To study the influence of steel truss web shear deformation on the deflection of steel truss web composite box beams, the beams were first decomposed into a laminated structure composed of top and bottom flanges and a steel truss. A steel truss web shear deformation angle function was introduced to establish an analytical model, and the flexural deformation of a simply supported beam was analyzed as an example. The effective stiffness of the cross-section was determined by combining Euler beam theory and the analytical solution, and the mid-span deflection was calculated using this effective stiffness. The flexural characteristics under different load conditions were analyzed and compared with the Euler beam theory. The influence of structural parameters such as steel truss web diameter, steel truss web wall thickness, and steel truss web inclination angle on the effective stiffness was also examined. The results show that considering steel truss web shear deformation provides an analytical solution closer to the finite element results, with a maximum error of 6.24%. Using the effective stiffness can effectively predict the mid-span deflection, with a maximum error of 3.64% compared with the analytical solution. Among the structural parameters affecting the effective stiffness, steel truss web wall thickness has the greatest influence, followed by steel truss web diameter and steel truss web inclination angle. Additionally, the effective stiffness is positively correlated with steel truss web diameter and steel truss wall thickness but negatively correlated with steel truss web inclination angle.

The calculation of the probability distribution of performance functions is a core issue in uncertainty quantification and reliability design, and the recently proposed equivalent expectation method (EEM) is an effective way to solve this problem. This paper proposes an improved EEM. Putting forward an empirical calculation formula for the standard deviation coefficient of auxiliary random variablesand obtaining a more accurate probability distribution of the auxiliary function. Meanwhile, aiming at the accuracy issue in calculating the probability distribution of theperformance function is proposed, the calculation formula for the PDF of the performance function is derived using only one auxiliary function. In the process of calculating the PDF, proposing an exact theoretical transformation of probability distribution from auxiliary functions to performance functions is proposed, resulting in a more accurate PDF of the performance function. Finally, the effectiveness and accuracy of the method are verified through three numerical examples. The results indicate that this method is suitable for computing the probability distribution of high-dimensional nonlinear or implicit performance functions.