Solution Procedure Research Articles

Nonlinear static analysis of masonry structures with mortar joints and cracking units by optimization‐based rigid block models

AbstractA rigid block model with elasto‐plastic softening interfaces is developed for nonlinear static analysis of masonry structures subject to monotonic loading. Cracking, crushing, and shear failures are taken into account at interfaces, following a simple micro‐modeling approach. An optimization‐based formulation is used for the solution of the equation systems governing the behavior of the rigid block assemblage. A simple incremental solution procedure is implemented to take into account the material softening behavior and the effects of large displacements on equilibrium conditions. The interface models are validated against tension and shear tests on bi‐block prisms from the literature. Applications to numerical and experimental out‐of‐plane loaded masonry walls as well as to circular arches with mortar joints are presented to evaluate the effects of tensile strength and the accuracy of the developed model against responses involving P‐Δ effects. Comparisons with experimental tests on shear walls also involving cracking of the units in the failure mechanisms are finally reported to discuss the potentialities and limitations of the proposed modeling approach.

Flow analysis of water conveying nanomaterials over a rotating surface with thermal radiation

PurposeThe present findings aim to investigate the thermal behavior of water-based nanofluid flow over a rotating surface, focusing on understanding the effects of different types of nanoparticles on thermal efficiency, considering thermal radiation and variable viscosity effects. By considering four distinct nanoparticles – silicon dioxide titanium dioxide, aluminum oxide and molybdenum disulfide – the study aims to provide insights into how nanoparticle addition influences heat production, thermal boundary layer thickness and overall thermal performance.Design/methodology/approachThe study employs computational methods, utilizing the BVP mid-rich algorithm for the solution procedure. The computational approach allows for a detailed investigation of the thermal behavior of nanofluid flows across a rotating surface under varying conditions.FindingsThe study concludes that adding nanoparticles in the base liquid increases heat production in the system, resulting in enhanced thermal boundary layer thickness. The comparative analysis shows that different nanoparticle types exhibit varying effects on thermal efficiency, suggesting that careful selection of nanoparticles can optimize heat transport and thermal management processes. Moreover, there's a noteworthy uptrend in the radial velocity profile concerning the stretching parameter, whereas a converse trend is observed in the thermal profile.Originality/valueThis study contributes original insights by comprehensively investigating the thermal behavior of water-based hybrid nanofluid flow over a rotating surface.

Multiple shared mobility services under competition: Empirical evidence for public acceptance and policy insights to sustainable transport

Traffic congestion and roadside emissions are severe and common problems in metropolitans. As a promising and sustainable solution to mitigating these vehicle externalities, shared mobility reduces the required vehicle fleet size for serving a given level of demand by sharing a vehicle among travelers with similar schedules and itineraries. Public acceptance is the key to the success of shared mobility development. This study investigates the acceptance of drivers and passengers of two typical competing shared mobility modes, car-pooling and taxi ride sharing, taking Hong Kong as a case study. For an empirical evaluation, an on-street stated preference survey was conducted, and 829 respondents, including 257 private car owners and 572 non-private car owners were interviewed about their travel preferences in three given hypothetical scenarios. In total, 2,487 observations were collected for calibrating two proposed logit-based discrete choice models for drivers and passengers. The model results show that the out-of-pocket cost, in-vehicle travel time, and out-of-vehicle time are key factors influencing travelers’ decisions toward car-pooling and taxi ride-sharing. An equilibrium model was proposed and an iteration solution procedure was applied to obtain a convergent solution to balance the demand and supply of drivers and passengers for car-pooling services. Furthermore, sensitivity analyses were carried out to examine the effects of variations in proportions of travel cost and taxi fare shared by passengers for car-pooling and taxi ride-sharing, and to assist in the formulation of relevant transport policies.

Multiaxial ratcheting-fatigue evaluation of pressurized elbow pipe under strong cyclic loading using damage-coupled cyclic plasticity model

Continuous damage mechanics (CDM) is based on the theories of continuous medium mechanics and continuous medium thermodynamics, which considers damage is an irreversible dissipative process within the materials, and employs the field-theoretic approach of image-only science to study the internal macroscopic damage evolution law of the materials and its influence on the deterioration of the macroscopic mechanical properties of the materials. Hence, within the framework of CDM, a damage-coupled cyclic plasticity constitutive model is proposed based on combined isotropic and Chen-Jiao-Kim (CJK) kinematic hardening rule for evaluating the ratcheting-fatigue behavior of 90° elbow pipes under strong cyclic loading in this paper. Stress return mapping and numerical solution procedures of the proposed model are formulated based on the backward finite difference method. Formulation of the consistent tangent operator is presented for the Finite Element implementation of the plasticity model in ABAQUS UMAT. The FE analysis of non-pressurized and pressurized elbow pipes under cyclic displacement-controlled loading is respectively performed using the implemented constitutive model. The results reveal that the predicted results of the damage-coupled cyclic plasticity constitutive model are better than combined isotropic-kinematic hardening model, and well consistent with the experimental data.

Dynamic Mean–Variance Portfolio Optimization with Value-at-Risk Constraint in Continuous Time

Recognizing the importance of incorporating different risk measures in the portfolio management model, this paper examines the dynamic mean-risk portfolio optimization problem using both variance and value at risk (VaR) as risk measures. By employing the martingale approach and integrating the quantile optimization technique, we provide a solution framework for this problem. We demonstrate that, under a general market setting, the optimal terminal wealth may exhibit different patterns. When the market parameters are deterministic, we derive the closed-form solution for this problem. Examples are provided to illustrate the solution procedure of our method and demonstrate the benefits of our dynamic portfolio model compared to its static counterpart.

An algorithm based on B-differentiable equations method for solving problems involving frictional contact coupled with concrete plastic damage

In this paper, an algorithm is proposed to solve the frictional contact problems while considering elasto-plastic material properties. The static and dynamic solution procedures are derived in incremental form, respectively. The proposed method employs a two-layer iteration strategy. In the outer iteration layer, the equilibrium equations are solved, with the stress and stiffness matrix updated at each iteration. Within the inner iteration layer, the contact force is calculated, where the contact equations, expressed as B-differentiable equations, incorporate only contact conditions in normal and tangential directions, and the contact flexibility matrix, obtained by applying unit force pair to all contact node pairs in turn, is introduced. Consequently, the solution for nonlinear equilibrium equations and contact equations is decoupled, requiring only one decomposition of the stiffness matrix for each calculation of the contact flexibility matrix, as it remains constant within the contact iteration layer. In addition, the constitutive model of concrete developed by Lee and Fenves is utilized. This model adopts two independent variables to describe tensile and compressive damage, together considering the strength recovery of the concrete. Numerical examples demonstrate the accuracy of the proposed method by comparing the results from Abaqus. Furthermore, the present algorithm is applied to static and dynamic analyses of a concrete arch dam with several transverse joints, where the effects of gravity, water level, the number of contact surfaces, and seismic load are considered, and some conclusions are obtained.

A hybrid Monte Carlo, discontinuous Galerkin method for linear kinetic transport equations

We present a hybrid method for time-dependent particle transport problems that combines Monte Carlo (MC) estimation with deterministic solutions based on discrete ordinates. For spatial discretizations, the MC algorithm computes a piecewise constant solution and the discrete ordinates use bilinear discontinuous finite elements. From the hybridization of the problem, the resulting problem solved by Monte Carlo is scattering free, resulting in a simple, efficient solution procedure. Between time steps, we use a projection approach to “relabel” collided particles as uncollided particles. From a series of standard 2-D Cartesian test problems we observe that our hybrid method has improved accuracy and reduction in computational complexity of approximately an order of magnitude relative to standard discrete ordinates solutions.

Aerodynamic Investigation on a Coaxial-Rotors Unmanned Aerial Vehicle of Bionic Chinese Parasol Seed.

Aerodynamic investigation of a bionic coaxial-rotors unmanned aerial vehicle (UAV) is performed. According to Chinese parasol seed features and flight requirements, the bionic conceptual design of a coaxial-rotors UAV is described. A solution procedure for the numerical simulation method, based on a multi-reference frame (MRF) model, is expressed, and a verification study is presented using the typical case. The aerodynamic design is conducted for airfoil, blade, and coaxial-rotors interference. The aerodynamic performance of the coaxial rotors is investigated by numerical simulation analysis. The rotor/motor integrated experiment verification is conducted to assess the performance of the coaxial-rotors UAV. The results indicate that the UAV has excellent aerodynamic performance and bionic configuration, allowing it to adapt to task requirements. The bionic UAV has a good cruise power load reach of 8.36 kg/kw, and the cruise flying thrust force is not less than 78 N at coaxial-rotor and rotor-balloon distance ratios of 0.39 and 1.12, respectively. It has the "blocks stability phenomenon" formed by the rotor downwash speed decreases and the balloon's additional negative pressure. The present method and the bionic configuration provide a feasible design and analysis strategy for coaxial-rotors UAVs.

Stretchable-thickness model for dynamic responses of graphene origami reinforced badminton sport plate

In this article, we organize a stretchable-thickness model to present a frequency analysis for a composite plate applicable in badminton court which is reinforced with origami graphene. A higher order kinematic model is extended in this work including three bending, shear, and stretching functions, where the stretching functions is responsible for satisfying the out of plane shear strains and stresses at top/bottom surfaces of the badminton equipment. The sport or composites plate is manufactured from a copper matrix reinforced with graphene origami where the effective material properties are calculated based on micromechanical models as a function of volume fraction and folding degree of graphene origami, material properties of matrix and reinforcement and temperature. The numerical results are presented with changes of volume fraction, folding degree of reinforcement, and thermal loading along the thickness direction. The main novelty of this work is accounting thickness stretching deformation for the analysis of a graphene origami reinforced plate and investigating the responses of graphene origami as a new reinforcement. A verification investigation is presented for approve of the methodology, and solution procedure. An investigation on the order of deformation is presented for various thickness ratio of the badminton sport plate.

Influence of tangential hydrodynamic force and inclination angle calculation on the dynamic responses analysis of mooring line based on lumped mass method

Research on mooring line response offers a scientific foundation and technical backing for ocean engineering management. The lumped mass method is commonly used to calculate the dynamic responses of mooring line, pioneered by Walton and Polachek, although it ignores the tangential hydrodynamic force. Nakajima addressed this limitation, but the inclination angle calculation for each element is approximated by the average of the adjacent two nodes. To accurately assess the influences of these factors, this work introduces the tangential hydrodynamic force component into the equation of motion for mooring line dynamic analysis based on the lumped mass method. Meanwhile, we improve the discretization process of lumped mass nodes, analyzing half of the connected spring at both ends of each lumped mass node respectively. The detailed formulation and motion equation for static and dynamic mooring line analysis are presented. The time-domain solution procedure based on the finite difference method is adopted. Finally, different external excitations are applied to calculate the dynamic responses of mooring line. The results show that the top tension increases by about 2%–5% considering the contribution of tangential hydrodynamic force, and the inclination angle calculation significantly influences the dynamic configuration of the mooring line when it is intense change.

Developing a Bi-Level Optimization Model for the Coupled Street Network and Land Subdivision Design Problem with Various Lot Areas in Irregular Blocks

Street design and land subdivision are significant tasks in the development and redevelopment planning process. Optimizing street and land subdivision layouts within a unified framework to achieve solutions that meet a set of objectives and constraints (e.g., minimizing parcel area deviation from standard values, minimizing land consumption for street construction, etc.) is a critical concern for planners, particularly in complex contexts such as blocks with irregular shapes and parcels of varying sizes and requirements. To address this challenge, a mathematical formulation is presented for the bi-level street network and land subdivision optimization problem. Subsequently, the solution procedure is outlined, which utilizes a genetic-based algorithm for street design and a memetic–genetic-based algorithm for land subdivision. Finally, two cases are presented, solved, and discussed to analyze and verify the proposed mathematical model and solution procedures. The results suggest that the formulated problem is suitable for addressing the coupled street network and land subdivision design problem, and it can be adapted and extended to other case studies. Additionally, the introduced ideas and algorithms satisfactorily solved the stated problem.

Combined effects of nonlinear thermal radiation and suction/injection on bioconvective boundary layer of Maxwell nanofluid over a porous movable surface

The nanofluids exclusively enhance the thermal significance of many engineering and industrial processes including the manufacturing processes, chemical reactions, polymers, thermal devices, heating systems, solar energy etc. The presence of porous medium and suction/injection phenomenon incorporates key importance in the petroleum engineering and plasma physics. The objective of current work is to present a theoretical analysis for investigating the bioconvective flow of Maxwell nanofluid with applications of suction/injection effects. The flow is causing by porous moving surface. The radiative phenomenon with nonlinear expressions is adopted. The chemical reaction features are used for analysis of concentration phenomenon. Modified Cattaneo–Christov approach is followed to model the problem. A set of dimensionless variables are used for simplifying the modeled equations. The solution procedure is subject to implementation of shooting scheme. Graphical explanation of problems is presented in order to evaluates the role of different parameters. Physical behavior of problem is focused and justified in details. It is noted that heat and mass transfer enhances due to suction/injection parameter. The temperature profile reduces due to thermal relaxation parameter. Current results reveal significance in the ehat exchangers, improving the sustainability of thermal systems, controlling the cooling processes, fertilizes, biofuels etc.

Risk-aware microgrid operation and participation in the day-ahead electricity market

This work examines the daily bidding problem of a grid-connected microgrid with locally deployed resources for electricity generation, storage and its own electricity demand. Trading electricity in energy markets may offer economic incentives but exposes the microgrid to financial risk caused by market commitments. Hence, a multi-objective, two-stage stochastic mixed integer linear programming (MILP) model is formulated, extending prior work of a risk-neutral microgrid bidding approach. The multi-objective model minimises both expected total cost of day-ahead microgrid operations and financial risk from bidding measured by conditional value-at-risk (CVaR). Bidding curves derived as first stage decisions are always feasible under present market rules – including a limitation on the number of break points per submitted curve – while being near optimal for the microgrid’s day-ahead recourse schedule. The proposed optimisation model is embedded in a variant of the ɛ-constrained method to generate bidding curve candidates with different trade-offs between the two conflicting objectives. Moreover, scenario reduction is used to compromise accuracy of the uncertainty set for better computational performance. Particularly, the marginal relative probability distance between initial and reduced scenario set is suggested to make a decision on the extent of scenario reduction. The proposed solution procedure is tested in a computational study to demonstrate its applicability to generate optimal microgrid bidding curve candidates with different emphasis between total cost and CVaR in reasonable computational time.

An innovative joint-space dynamic theory for mobile multi-axis system with unilateral constraint

The wheel-ground unilateral constraint is essential in establishing the complete mobile multi-axis system dynamics. To reduce the calculation complexity and improve the dynamic performance, an innovative joint-space dynamic theory for mobile multi-axis systems with unilateral constraints is proposed. This present study builds on our existing explicit dynamics studies of tree-chain rigid multi-axis systems. By analyzing the formulation of the unilateral constraints, the complexity of establishing the constraint equations is reduced while the physical implications are clear. The constraint equations are derived and established based on the explicit partial derivative equations, where the expression of the constraint equations is greatly simplified. Then, based on the process of backward force iteration and in combination with the derived dynamic and unilateral constraint equations, the solution and analytical procedure for unilateral constraints are presented. The accuracy of the proposed method is proved by the three-wheeled multi-axis system and Mars rover examples. The proposed method is explicit, canonical, and symbolic and has the advantages of simple modeling and low computational complexity, which is analyzed by comparing it with the Open Dynamic Engine's approach.

Modeling of size dependent buckling behavior of piezoelectric sandwich perforated nanobeams rested on elastic foundation with flexoelectricity

This article presents a size dependent mathematical model and an analytical solution methodology to accurately simulate and analyze the size dependent buckling behavior of piezoelectrically layered sandwich nanobeams with perforated core embedded in an elastic medium with flexoelectricity. The electric enthalpy energy function is expressed in terms of the electric and the flexoelectric effects. Regular squared cutouts perforation pattern is adopted for the perforated core. Closed forms for the equivalent geometrical parameters of perforated core are developed. The shear deformation effect is incroporated using the Timoshenko beam theory (TBT). To capture the nonlocality and the microstructure length scale effects, the nonlocal strain gradient elasticity theory is modified and adopted to include the electromechanical nonclassical effects. The Hamiltonian principle is utilized to derive the equilibrium equations. An analytical solution methodology is developed to derive closed forms for critical buckling loads. The developed solution procedure is implemented into a MATLAB software code. The accuracy of the developed procedure is verified by comparing obtained results with corresponding cases reported in the literature. Influences of different design variables on the electromechanical buckling behavior are explored through intensive parametric studies. Results obtained showed the significant effects of the flexoelectricity and the piezoelectric parameters on the size dependent buckling behavior of piezoelectric sandwich nanobeams with perforated core. Size dependent electromechanical as well as mechanical buckling behaviors could be controlled by adjusting these parameters. The developed procedure and the obtained numerical results are helpful in many technological and industrial applications as MEMS and NEMS.

Second order hemivariational inequality driven by evolution differential inclusion to a dynamic thermoviscoelastic contact problem

In this paper we study an abstract system which consists of a hyperbolic hemivariational inequality coupled with a differential evolution inclusion involving a history-dependent operator in Banach spaces. A hybrid iterative system corresponding to the hemivariational inequality is introduced. Combining the Rothe method, a feedback iterative technique, and a surjectivity result for pseudomonotone operators, we establish existence and a priori estimate for solutions to an approximate problem. Next, through a limiting procedure for solutions of the hybrid iterative system, we show the existence of a mild solution to the original problem. Finally, we apply the main results to a dynamic contact problem in thermoviscoelasticity.

Improved fuzzy multi-objective transportation problem with Triangular fuzzy numbers

The present study investigates a Multi-Objective Transportation Problem within a fuzzy environment. The cost of transportation, supply, and demand data are assumed to be inaccurate due to market variations. As a result, the parameters are imprecise or fuzzy data. We offer a multi-objective, balanced transportation problem during this work, where all the parameters are fuzzy numbers. Following a mathematical formulation, fuzzy arithmetic will be used to divide the Fuzzy MOTP into three levels MOTP (lower, medium, upper). After reducing the problem to a crisp MOTP and applying a harmonic mean to each objective function, a suggested solution procedure is presented. Determining the optimal solutions for the FMOTP under unknown situations is, thus, the most important objective of this research.

Flexural wave propagation characteristics of advanced nanocomposites reinforced sandwich structure via 3D-flexibility-deep neural networks approaches

The propagation of flexural waves in advanced nanocomposites reinforced sandwich structures is a topic of paramount importance in the field of structural engineering and materials science. This study investigates the dynamic behavior of such structures, focusing on the wave propagation characteristics along with longitude and lateral directions and their influence on structural performance. Advanced nanocomposites, with their unique material properties and enhanced mechanical properties, offer promising opportunities for the development of lightweight and high-strength sandwich structures. For this important aim, first, a mathematical modeling using three-dimensional flexibility theory and an analytical solution procedure, the results are collected. After that using the datasets of the mathematical modeling section, the hybrid deep neural networks are trained, tested, and validated. Through comprehensive analytical simulations and machine network validations, this research elucidates the complex interplay between material composition, structural geometry, and wave propagation phenomena. Key parameters, such as wave velocity, dispersion, and geometry conditions are analyzed to gain insights into the dynamic response of the sandwich structure. The findings contribute to a deeper understanding of the underlying physics governing flexural wave propagation in nanocomposite-reinforced sandwich structures, thereby facilitating the design and optimization of lightweight and resilient structural systems for diverse engineering applications.

Analysis of mechanical response and failure characteristics of tunnels crossing active faults considering axial force and geometrical nonlinearity

Tunnels subjected to active fault dislocation may experience significant damage. This paper establishes a novel methodology and solution procedure for analyzing the mechanical response and failure characteristics of tunnels subjected to active fault dislocation based on an elastic foundation beam model. The proposed methodology includes axial, transverse, and vertical soil-tunnel interaction terms, in addition to geometrical nonlinearity and axial force terms in the governing equation. This approach has a significantly extended application range, effectively addressing the problems encountered in tunnels crossing active faults with diverse crossing angles, dip angles, and fault types. The proposed methodology is verified by comparison to a 3D FEM model with various fault types, experimental tests, and on-site case, and the results are in excellent quantitative and qualitative agreement with the numerical, experimental, and on-site results. When fault displacement is below 0.5 m, disregarding geometric nonlinearity results in calculation errors of approximately 10% to 17% for peak axial force (Nmax), 18% to 22% for peak shear force (Vmax), and 20% to 30% for peak bending moment (Mmax). Finally, the responses caused by different factors, i.e., fault type, fault displacement, tunnel stiffness, and tunnel diameter, are investigated in detail to better understand tunnels crossing active faults. The results show that amongst the various fault types, the Vmax and the Mmax experienced by tunnels subjected to oblique slip-fault dislocation surpass those of other fault types, accompanied by the most extensive failure range. The augmentation of fault displacement, tunnel stiffness, and tunnel diameter precipitates a corresponding escalation in the Nmax, Vmax, Mmax, and failure range. Under oblique-slip fault dislocation, the tunnel undergoes an initial phase of shear failure, followed by tension-bending failure, delineated by distinct fault displacement thresholds of 0.1 m and 0.2 m, respectively. The proposed methodology provides the advantage of reliable stability analysis and design of tunnels crossing active faults.

The Impact of Volume Fraction and Nanoparticles in the Flow of Nanofluids along the Boundary Layer Over a Flat Plate

Introduction: The forced convective, steady, viscous, nonlinear boundary layer flow of a two-dimensional problem over a flat plate with heat transfer nanofluids. The flow is laminar. Two different types of nanoparticles, namely, Titanium dioxide () and Silver are used to prepare nanofluids with base fluid is chosen as water. Nanofluids has a large number of applications in the area of biomedical, cooling and tribological applications. Objectives: To study about the effect different nanoparticles and their volume fraction in the flow of nanofluids along the boundary layer over a flat plate. Analyse the changes in the viscosity, density, specific heat capacity, thermal conductivity, Prandtl number, skin friction coefficient and Nusselt number. Methods: The flow of the fluid that are governed by the PDEs that are nonlinear are transformed into the ODEs that are nonlinear by employing similarity transformations, which then solved by the use of MATLAB bvp5c solution procedure. Results: Both thermal conductivity and heat transfer coefficient increases with the increase in the volume fraction of the corresponding nanoparticle. Also, Silver-water nanofluid has the high thermal conductivity and heat transfer rate when compared with Titanium dioxide-water nanofluid. Conclusions: Silver water nanofluid surpasses titanium dioxide water nanofluid in terms of thermal conductivity and heat transfer rate. Moreover, the physical attributes like viscosity, density, and thermal conductivity of nanofluids escalate proportionally with the volume fraction of nanoparticles. Conversely, specific heat capacity and Prandtl number exhibit an inverse relationship with the volume fraction of nanoparticles, decreasing as it increases.