In this paper, a new solution approach of using Free Element Method (FrEM) is proposed to solve thermal-mechanical problems consisting of composite materials and cracks. In this approach, the computational domain of the problem is discretized into multi-zones and in each zone a set of local nodes are generated. At the local nodes of each zone, the high order free elements are used to collocate the

Due to the inherent uncertainties in various systems, deterministic approaches may not be able to satisfactorily characterize their response. In such cases, stochastic approaches that can systematically consider uncertainties have to be employed. In the past, many stochastic finite element analysis (SFEA) methods have been developed for uncertainty quantification (UQ), among which the perturbation

The present manuscript presents a framework for automating the formulation and resolution of limit analysis problems in a very general manner. This framework relies on FEniCS domain-specific language and the representation of material strength criteria and their corresponding support function in the conic programming setting. Various choices of finite element discretization, including discontinuous

Several finite element models have been analysed to numerically investigate the effects on the compressive strength and on the elastic modulus of a concrete with partial replacement of natural aggregates with different amounts and types of rubber particles from waste tyres. Percentages of substitution from 0% to 83% have been considered with rubber particles size ranging from 3 mm to 30 mm. Analytical

The conventional Cellular Automata (CA) approach has the disadvantage of being particularly suited for design optimization of uniform truss ground structures with identical cells. Moreover, the conventional CA algorithms, which are intrinsically local, have to be modified in order to be able to tackle problems involving displacement constraints. This paper presents a new non-uniform Cellular Automata

As the development of new grades of Ceramic Matrix Composites (CMC) for civil aviation grows, different manufacturing processes have been perfected and several of them can be used successively in order to obtain different types of micro-structures and a variable material quality. Consequently a versatile model should be developed in order to compare these materials and create a tool to help engineers

The sensitivity analysis of hysteretic systems under nonstationary random excitations is of great concern to the stochastic optimal design and control of structures. The equivalent linear equation of motion is first constructed for the hysteretic system by the equivalent linearization method (ELM), and the sensitivity equation of the equivalent linear system is then derived by the direct differentiation

This paper proposes a non-stationary signal decomposition approach to remove the harmonic responses in the operational modal analysis for time-varying structures. Two time–frequency representations, the non-parametric windowed Fourier transform and the power spectral density estimated by the parametric functional series time-dependent autoregressive moving average model, are combined to decompose the

Surrogate model-based sensitivity analysis, especially framed by neural network ensemble (NNE), is an attractive but unresolved issue in structural reliability assessment. In this paper, differing from existing studies, an overview and assessment of typical methods for surrogate model-based parameter sensitivity analysis, namely the input perturbation method, the local analysis of variance, the connection

Spectral element method (SEM) is a robust and efficient mathematical technique for dynamic analysis of structures in frequency domain. Unlike finite element method (FEM), in SEM, the dynamic stiffness matrix forms a nonlinear eigenvalue problem (NLEP) to compute the natural frequencies and vibration modes of the structure which cannot be solved using linear numerical eigen-solvers. In this paper, two

The theory of archgrids of minimal weight has been formulated in the late 1970s and recently reconsidered by means of duality theory in the calculus of variations. In the current study, we follow this approach by putting forward an efficient computational scheme. Trial functions for both primal and dual problems are decomposed in two function bases: trigonometric (Fourier) and polynomial (Legendre)

The optimization of truss structures is a complex computing problem with many local minima, while metaheuristics are naturally suited to deal with multimodal problems without the need of gradient information. The Coyote Optimization Algorithm (COA) is a population-based nature-inspired metaheuristic of the swarm intelligence field for global optimization that considers the social relations of the coyote

A novel efficient stochastic incremental dynamics methodology considering first-excursion probability for nonlinear structural systems subject to stochastic seismic excitations in alignment with contemporary aseismic codes provisions is developed. To this aim, an approximate nonlinear stochastic dynamics technique for conducting first-passage probability density function (PDF) based stochastic incremental

The paper presents a locking-free four-node element for laminated composite and sandwich plates based on Refined Zigzag Theory (RZT). Initially, two RZT-based plate elements are derived using four-node and eight-node configurations, achieved by way of standard C0 isoparametric shape functions. In addition, with a view on improving the modelling of extremely thin plates, an anisoparametric four-node

Wire-and-Arc Additive Manufacturing (WAAM) has been recently adopted to create innovative structural forms and architectural shapes. As shown by few experimental investigations, the layer-by-layer deposition induces a remarkable anisotropy in the elastic response of the WAAM-produced alloys. A suitable topology optimization technique is implemented to account for this peculiar behavior of the material

In this paper, we introduce an extension of the piecewise rigid displacement (PRD) method for addressing the stability of a generic two-dimensional masonry structure subjected to large displacements. So far, the PRD method has been applied to simulate cracks in the reference configuration considering small displacements. Here, we investigate both cracks and internal forces in the presence of large

The interfacial transition zone (ITZ) between cement paste and aggregates in concrete plays an important role in the macro-mechanical properties of concrete. It generally exhibits as a weak link, restricting the material resistance of concrete. The present work aims at proposing a numerical bridge from mesostructure features to macro-mechanical properties based on the extended finite element method

Structural indicators of asphalt mixtures, including aggregate gradation, spatial distribution, orientation, shape, angularity, texture, aggregate content, asphalt content and air void content, determine mixture heterogeneity and therefore significantly affect the micromechanical response of mixtures. An approach to the virtual design of mixture microstructure using structural indicators is proposed

Research on the control of wave propagation has received continuous attention due to its potentially rewarding applications in the past decades, and numerous methods have been developed for controlling wave propagation in certain materials or structures. Despite previous work has made many innovations in controlling wave propagation, they are limited to the research from a band gap perspective. Herein

Parts of the irreversible response of materials can be described by a plasticity approach. For modelling quasi-brittle materials such as concrete, the microplane approach is a powerful method. In order to predict the load–displacement as well as the stress–strain relation, numerous constitutive models developed for small strains have been used successfully. Nevertheless, for example, at high hydrostatic

In this paper, a new and robust formulation to solve three-dimensional thermomechanical contact problems under non-linear interface thermal contact (ITC) conditions is presented. This methodology allows us to consider non-linear thermal contact conductance, including the presence of thermal interface materials (TIM), and convective conditions at the interstitial contact region. The Boundary Element

A step by step method is presented for reducing the need for a large number of response history analyses (RHAs) in developing surrogates to predict the structural responses. These surrogates, which map ground motions features and characteristics of the structural systems into structural responses, are used in deriving fragility curves; and mostly are developed using machine learning algorithms. A machine

This paper addresses the free-vibration response of structures coupled with periodically-distributed resonators, generally referred to as locally-resonant structures. The first step is to show that all exact natural frequencies can be calculated by a proper formulation of the Wittrick-Williams algorithm, involving a condensed dynamic stiffness matrix whose size depends only on the number of degrees

An efficient reliability method is presented to address the challenge inherent in the high-dimensional reliability analysis. The critical contribution is an elegant implementation of combining the kernel principal component analysis (KPCA)-based nonlinear dimension reduction and the Gaussian process regression (GPR) surrogate model by introducing a nonintrusive, joint-training scheme. This treatment

Restoration of ancient wooden beams and design of smart wood-based structures are gaining an increasing interest in building industry. In this context, the computational challenge is to develop numerical constitutive models that account for the complex and strongly non-linear behaviour of wood. Wood is a natural composite exhibiting pronounced orthotropic behaviour, and markedly different properties

This research bridges the gap between the numerical layout optimization method and the geometry-based analysis and design method of graphic statics. The study connects the two methods for the application of strut-and-tie models in reinforced concrete design. It suggests a new algorithm for the algebraic graphic statics of indeterminate trusses inspired by the layout optimization method. This research

The analysis of three-dimensional (3D) stress states can be complex and computationally expensive, especially when large deflections cause a nonlinear structural response. Slender structures are conventionally modelled as one-dimensional beams but even these rather simpler analyses can become complicated, e.g. for variable cross-sections and planforms (i.e. non-prismatic curved beams). In this paper

This paper presents a novel mesoscale finite element model for predicting the effective mechanical properties of concrete-like particle-reinforced composites with concave aggregates. In the mesoscale model, unit cells (UC) with randomly distributed non-convex particles and period boundaries are generated through computationally efficient algorithms to represent the periodic microstructures of concrete

Continuum models based on the combination of the theories of plasticity and damage mechanics pose a powerful framework for representing the highly nonlinear material behavior of cohesive-frictional materials. However, non-associated plastic flow rules for representing the inelastic volumetric expansion of such materials may result in unstable material behavior and, accordingly, strongly mesh-dependent

Adaptive growth method is a structural topology optimization approach based on the growth mechanism of natural biological branching systems, and it has been successfully applied for the static reinforcement of three-dimensional box structures. However, due to the effect of structural characteristics towards natural frequencies, it is difficult for adaptive growth method to effectively grow stiffeners

Fiber reinforced materials (FRMs) can be modeled as bi-phasic materials, where different constitutive behaviors are associated with different phases. The numerical study of FRMs through a full geometrical resolution of the two phases is often computationally infeasible, and therefore most works on the subject resort to homogenization theory, and exploit strong regularity assumptions on the fibers distribution

Suppressing enclosed voids in topology optimization is an important problem in design for manufacturing. The method of Poisson equation-based scalar field constraint (i.e., Poisson method) can effectively address this problem. Nevertheless, the numerical performance of this method is not well understood. This paper investigates the numerical functionality and characteristics of the Poisson method.

This paper presents a highly efficient and accurate approach to determine the bounds on the first excursion probability of a linear structure that is subjected to an imprecise stochastic load. Traditionally, determining these bounds involves solving a double loop problem, where the aleatory uncertainty has to be fully propagated for each realization of the epistemic uncertainty or vice versa. When

Several simplified models have been developed to simulate unbound soil for dynamic soil-structure interaction analysis in time domain. However, the existing models may have critical limitations for general applications. This study presents an approach to systematically generate lumped-parameter models with frequency-independent coefficients to represent the dynamic stiffness of rigid foundations in

In this study, a novel scheme for modelling and analysis of spot-welded shell structures is presented by placing local spider-web shell meshes representing the weld nugget region in a global shell mesh. Interface shell elements are employed for trimmed shell elements with arbitrary number of nodes created by cutting a global shell mesh with the boundaries of local spider-web shell meshes. Transverse

The use of multiscale schemes for computational failure evaluations of quasi-brittle composites, particularly concrete, has become a promising challenge for evaluating the complex degradation mechanisms at different scales of observations. In the framework of standard finite element procedures, both concurrent and semi-concurrent multiscale procedures have so far been considered for analysing failure

This paper, for the first time in literature, formulated and validated a three-dimensional, nonlinear augmented finite element method (3D A-FEM) that can account for multiple crack evolution in laminated composites under large deformation. The 3D A-FEM accounts for all major cracking events (intra-ply matrix cracking, fiber rupture/kinking, and inter-ply delamination) with explicit cohesive cracks

The optimization of damping composite material in a certain frequency range has become one of the critical issues in structural engineering applications due to the fact that the structures usually work in a wide vibration frequency range. This paper proposes a topology optimization method for designing the damping composite materials with high stiffness and high broadband damping. The broadband damping

In this paper, we develop a CAD-oriented topology optimization method incorporating directly the CAD model into the feature-driven optimization (FDO) framework. Practically, any free-form design domain model (FDDM), defined by the CAD model in stereolithography (STL) file format, is first represented by a level set function employing a radial basis function (RBF) interpolation technique. Feature-based

This paper presents a comprehensive numerical finite element implementation of the nonlocal strain gradient theory applied to thin laminated composite nanoplates using Kirchhoff theory (known as Classical Laminated Plate Theory or CLPT). Hermite interpolation functions are used to approximate membrane and bending degrees of freedom according to the conforming and nonconforming approaches. To the best

Assuming Timoshenko’s beam hypothesis, this paper proposes a unified strategy to derive exact finite-element (FE) matrices for framed structures having elements with variable rigidity. Its basic idea is to apply the principle of virtual forces (PVF), at the element level, to obtain a flexibility-based set of equations from which structural-property and nodal-load coefficients can be directly evaluated

We present in this paper a novel and efficient computational approach in terms of triangular extended stochastic finite element method (T-XSFEM) for simulation of random void problems. The present T-XSFEM is further enhanced by local mesh refinement with the aid of variable-node elements to couple/link different mesh-scales, increasing the efficiency of the developed approach and saving the computational

Traditional origami design is generally based on designers’ artistic intuition and skills, mathematical calculations, and experimentations, which can involve challenges for crease patterns with a large number of vertices. To develop novel origami structures for engineering applications, systematic and easy-to-implement approaches capable of generating diverse origami patterns are desired, without requiring

This paper shows experimental and numerical analyses on rammed earth arches asymmetrically loaded and successively strengthened with a natural composite. The aim is to evaluate the capability of finite element codes to faithfully describe the mechanical response, including the post peak branch and post elastic deformations. The mechanical properties of rammed earth were determined through specific

This paper concerns a computational implementation for solving a Moving Load (ML) problem on an infinite Euler–Bernoulli elastic beam on a Pasternak visco-elastic support. A steady-state dynamic response in convected coordinate is sought, by a numerical approach with discretization over a finite domain, implying spurious boundary reflections of non-evanescent waves. This is effectively solved by: (a)

This paper proposes a sampling-based system reliability-based design optimization (SRBDO) method with local approximation of constraints. To enhance the optimization efficiency of SRBDO problems with time-consuming constraints, Kriging metamodels are employed to replace the true constraint functions. A new composite active learning strategy based on the possibility of correctly predicting the state

Efficient modeling and optimization techniques are required to overcome the high design complexity and computational costs concerning the engineering of composite structures. In this paper, a modeling framework for the dynamic analysis of doubly curved composite panels is developed. Lamination parameters are used to characterize the stiffness properties of the laminate, and the responses are calculated

The application of structural topology optimization with complex engineering materials is largely hindered due to the complexity in phenomenological or physical constitutive modeling from experimental or computational material data sets. In this paper, we propose a new data-driven topology optimization (DDTO) framework to break through the limitation with the direct usage of discrete material data

An isogeometric membrane element based on the non-uniform rational basis spline (NURBS) model is presented that accounts for membrane wrinkling based on tension-field theory. First, the element is validated by means of a benchmark problem involving a partly wrinkled membrane. It is then applied to the large deformation of a thin membrane structure using a two-stage procedure that combines dynamic relaxation

The Shanghai Tower is presently the tallest structure in China and one of the super tall buildings in the world. To get a quick and direct insight into the overall dynamic behavior of this complex structure, a lumped-mass finite element model based on macro beam theory was developed. Next, an in-depth sensitivity analysis was performed on this baseline model and model updating was conducted by using

A fast reanalysis solver using linear tetrahedral elements is developed for 3D transient thermo-mechanical problems with temperature-dependent materials. The core idea is to formulate the reanalysis framework of a stable node-based smoothed finite element reanalysis method. In the developed solver, the stable node-based smoothed finite element method (SNS-FEM) is used as the main solver due its accuracy

Real fire incidents have shown that the structural systems of high-rise buildings perform much better during a fire attack than what classical structural fire analysis predicts. The reason behind this phenomenon is the empirically established fact that beneficial interaction mechanisms evolve between the fire-exposed and the fire-unexposed parts of structural systems. However, there is no computational

Particle damping is a passive damping technique at which granular material is either filled in a box attached to a vibrating structure or it is filled in holes embedded in the vibrating structure. Due to the structural vibrations, momentum is transferred to the granular material which interacts with each other. As a result, energy is dissipated by impacts and frictional phenomena between the particles

Prediction of vibrations generated by railway traffic experiences an increasing interest, as new lines are being constructed and planned in many countries. The paper proposes a numerical model to analyse a coupled vehicle–bridge–soil system, taking into account the most important phenomena affecting the structure, while at the same time being comparatively computationally efficient. Such model is useful

We study and use overlapping triangular finite elements enriched by trigonometric functions and implicit time integration to solve transient wave propagations in inhomogeneous media. We show explicitly that the total dispersion error of the calculated solutions can be split into two parts, the spatial error and temporal error. The study of the spatial dispersion error shows the effectiveness of the

The determination of effective material properties of composites based on a three-dimensional representative volume element (RVE) is considered in this paper. The material variation in the RVE is defined based on the colour intensity in each voxel of an image which can be obtained from imaging techniques such as X-ray computed tomography (XCT) scans. The RVE is converted into a numerical model using

We present a modeling framework for propagating the uncertainty, stemming from random heterogeneity of concrete microstructure, to its mesoscale elastic properties at the level of statistical volume element. The microstructure of concrete is modeled as a three-phase composite, consisting of aggregates (inclusions) in mortar (matrix), and interfacial transition zone (ITZ), a thin high porosity zone

The field of optimal design of linear elastic structures has seen many exciting successes that resulted in new architected materials and structural designs. With the availability of cloud computing, including high-performance computing, machine learning, and simulation, searching for optimal nonlinear structures is now within reach. In this study, we develop convolutional neural network models to predict

We propose a new adaptive NURBS upper-bound limit analysis approach for the assessment of general three-dimensional curved masonry structures, based on different meta-heuristic mesh adaptation schemes. The method, which can easily be integrated within CAD modeling environments, allows to establish the actual failure mechanism and load bearing capacity of a masonry structure by iteratively adjusting

In this paper, we introduce a level set topology optimization formulation considering coupled mechanical and thermal loads. Examples considering stress and compliance minimization under temperature and volume constraints, and mass minimization under stress and temperature constraints, are presented. The p-norm of the stress field and temperature field is used to approximate the maximum stress and temperature