Computers & Structures最新文献

In the second-order reliability method, the failure surface consisting of random variables is approximated as a paraboloid in standard normal space. The principal curvatures of the paraboloid are obtained by processing the Hessian matrix to compute the failure probability. However, Breitung's approximate formulation is not always accurate for the reliability problem with the highly nonlinear failure surface. In this paper, based on the approximated paraboloid, a hyperspherical cap area integral method (HCAIM) is presented to improve the accuracy with consistent efficiency. In HCAIM, the hyperspherical cap area expression is combined with the integral method, thus converting the multidimensional failure probability expression into a one-dimensional integral equation to solve for the failure probability of a paraboloid of revolution. An equivalent probability formula is proposed that replaces the failure probability of an elliptic paraboloid with the failure probabilities of multiple paraboloids of revolution. The performance of HCAIM is demonstrated by examples and compared with other methods. The results show that the proposed HCAIM is robust and accurate.

A new 3D topology optimization approach is presented that is based on the singular value decomposition of the input/output transfer matrix of the system. To start with, the input and output vectors, i.e. the acting loads and the quantities of interest for the designer, are chosen and the input-output transfer matrix is derived. Such matrix, say $G\left(p\right)$, depends on the vector of the design variables p (the densities at the element level). The singular value decomposition of $G\left(p\right)$ is the core of the proposed approach. It provides singular values as well as left and right singular vectors. Singular values are shown to uniquely define a few matrix norms that can be conveniently computed and used as goal functions to be minimized. Left and right singular vectors respectively represent the principal input/output pairs of the system whose gain is the associated singular value. Numerical optimization is pursued via the method of moving asymptotes (MMA) [1] that calls for the semi-analytic computations of objective functions and constraints. The results of a few 3D numerical investigations are presented and discussed in much detail. An in-house Matlab code developed for the sake of this paper, and based on the ones presented in [2] and [3], is provided in full as an Appendix to the paper.

Existing computational design tools for steel connection design predominantly employ a point-based design (PBD) approach, which requires iterative re-evaluation whenever there are changes in design specifications. This paper introduces a new framework that adopts a set-based design (SBD) approach, aiming to substantially reduce the iteration and time cost associated with steel connection design and rework. The framework integrates a component-set connection design model with a database storage and query-based data retrieval method. The first method enables the flexible and efficient generation of a large connection design space from all possible component combinations, and automated identification of valid connection configurations within it. The latter method allows for automated design space refinement from preference-based evaluation of connection design efficiency and high-speed comparison and selection of optimal connection designs. To evaluate the relative performance of SBD and PBD approaches, the framework is applied to a steel floor system design case study with 62 connections. Results showed that the SBD approach achieved near-instantaneous connection design automation, with a total execution time of fewer than 55 milliseconds, making it over 10 times faster than the corresponding PBD approach.

The Dual Reciprocity Boundary Element Method (DRBEM) is a numerical technique that has been widely employed in structural engineering for solving boundary value problems. This method is based on the principle of reciprocity, which allows the application of boundary conditions at fictitious points on the actual domain of interest. In recent years, there has been a growing interest in the development and application of DRBEM formulations for different areas of engineering problems, such as heat transfer in solids, convection and diffusion problems, acoustics, and fluid flow in porous media.

This review paper provides a comprehensive overview of DRBEM formulations and focuses on their applications in structural engineering. The major advantages and limitations of DRBEM are discussed, along with the various approaches that employ different radial basis functions in its implementation are presented. The review also highlights several case studies that demonstrate the effectiveness of DRBEM in solving complex structural engineering problems, such as stress analysis, crack propagation in materials, and structural dynamics. Furthermore, the paper identifies several areas where DRBEM can be further improved.

Overall, this review paper provides valuable insights into the DRBEM method and its potential for solving complex structural engineering problems. The summary presented in this paper can help researchers and practitioners in the field of structural engineering to better understand the capabilities of DRBEM and its potential applications in their work.

The present paper introduces a global/local approach for the analysis of three-dimensional (3D) stress states of composite laminated structures. It consists of a two-step procedure. In particular, the first step makes use of finite element modeling based on classical 2D plate elements, whereas a refined layer-wise model based on Carrera Unified Formulation (CUF) is adopted to extract the 3D stress and strain fields in some critical regions that may have arbitrary dimensions. This approach allows dealing with large local areas, increasing the accuracy of the static solution, along with the possibility of embedding this technique in more complex procedures, such as the least-weight design of large heterogeneous complex assemblies, stiffness optimization, or localized progressive failure analysis. The numerical results shown in this paper want to assess the physical and numerical validity of the global/local approach. Particular attention is focused on the choice of the dimensions of the local area (patch) subjected to detailed refined analysis. Also, the convergence properties of the present hybrid FE model are discussed. The first examples deal with laminated composites. Then, the advantages of this methodology are further highlighted by considering free-edge problems and a complex wing structure.

This paper proposes a novel limit analysis block element to model the ring behavior in masonry arch bridges, with consideration of axial deformation induced by both bending and axial compressing motions. The governing formulation is established based on the kinematic theorem. After constructing the velocity field of the block element, the new compatibility condition is put forward, followed by a discussion of possible linearization for the element constitutive model. A new heterogeneous limit analysis formulation that accounts for the deformability of the elements is given at the end. For benchmarking purposes, the collapse of an 80-block arch is first investigated to understand the influence of using different constitutive linearizations. Then, the proposed element is applied to analyze the collapse of a practical bridge involving arch-fill interactions. The results indicate a great necessity of considering the deformability of the ring when analyzing the collapse of masonry arch bridges. Compared with previous experimental results of Prestwood Bridge, employing the rigid modeling for the ring will lead to a significantly overestimated load prediction (about 46.3%) while the proposed deformable brick element with quadrilateral-linearized constitutive can produce a very accurate prediction (bias within 1%). Adoption of the hexagon linearization will give rise to a comparatively inflexible block behavior and the corresponding ring performs analogous to the rigid case. Finally, the model proposed gets over the main shortcoming exhibited by a beam discretization of the ring, namely the potential over-flexibility of the bridge arch, induced by the simplification of the actual geometry.

This study aims to achieve real-time estimation of the full-field strain distribution in a structure by signals measured from several strain gauges attached to the structure. Our virtual sensing procedure is developed based on finite element formulation and employs the mode superposition approach. To verify the feasibility of the proposed procedure, numerical and experimental tests are conducted on a laboratory-scale offshore jacket structure subjected to water waves. Key aspects addressed in this study include the selection of displacement modes and the division of strain signals. The experiments are performed in an ocean basin, and comprehensive explanations are provided for the jacket prototype design, implementations, experimental setup, and wave loading conditions. The performance of the proposed virtual sensing procedure is thoroughly assessed through various evaluation measures, enhancing the understanding of its capabilities and limitations in practical applications.

The paper presents a nonlinear concentrated plasticity frame element for advanced analysis of steel frames exposed to elevated temperatures. The element extends the formulation based on the generalized plasticity material model that was successfully applied to the analysis of steel and composite structures. It considers the material's nonlinear behavior, temperature-induced loading, strength and stiffness degradation typical for structures under fire conditions. The nonlinear geometry is taken into account with the corotational formulation. Because of the generalized plasticity relations adoption, the element can describe the gradual yielding of cross sections. At the same time, the implemented return mapping algorithm ensures the element's high computational efficiency. The governing element equations, selection of parameters and computer implementation are discussed in the paper, followed by element validation through the number of experimental data examples and other numerical models. The comparative analysis demonstrated the element's versatility and capability to accurately predict the structural response of steel frame structures exposed to fire.

This paper presents a literature review on methods for enabling real-time analysis in digital twins, which are virtual models of physical systems. The advantages of digital twins are numerous, including cost reduction, risk mitigation, efficiency enhancement, and decision-making support. However, their implementation faces challenges such as the need for real-time data analysis, resource limitations, and data uncertainty. The paper focuses on methods for reducing computational demands, which have not been systematically discussed in the literature. The paper reviews and categorizes methods and tools for accelerating the modeling of physical phenomena and reducing the computational needs of digital twins.

A boundary point interpolation method (BPIM) is presented in this paper for numerical solving acoustic problems. The BPIM is a boundary-type meshless method that combines the point interpolation technique for constructing approximate functions with boundary integral equations for reformulating boundary value problems. Since effective numerical integration techniques are crucial in the BPIM and boundary integral equation methods for calculating regular and singular integrals, two Clenshaw-Curtis integration techniques (CCITs) for regular and weakly singular integrals are derived in a unified manner with the same integration points on quadratic integration cells. In addition, a unilateral CCIT, a power series expansion technique, and an improved CCIT are proposed to effectively calculate strongly singular integrals or Cauchy principal value integrals in the BPIM. These integration techniques provide direct and efficient formulas for calculating boundary integrals on quadratic integration cells, and can be directly applied to the calculation of regular and singular integrals in the boundary element method and other meshless boundary integral equation methods. Explicit expressions of integration weights in all CCITs are derived, and the values of integration points and weights are listed. Numerical results are finally provided to validate the effectiveness of the present meshless method and integration techniques.