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In this paper, we present an investigation into the stability of equilibrium points and synchronization within a finite time frame for fractional-order Lengyel–Epstein reaction-diffusion systems. Initially, we utilize Lyapunov theory and multiple criteria to examine the finite-time stability of equilibrium points. Following this analysis, we design efficient, interdependent linear controllers. By applying a Lyapunov function, we define new adequate conditions to ensure finite-time synchronization within a specified time interval. Finally, we provide two illustrative examples to demonstrate the effectiveness and practicality of our proposed method and validate the theoretical outcomes.

An approach for the topology optimization of structures composed of nonlinear beam elements under time-varying excitation is presented. Central to this approach is a hysteretic beam finite element model that accounts for distributed plasticity and axial-moment interaction through appropriate hysteretic interpolation functions and yield/capacity function, respectively. Nonlinearity is represented via the hysteretic variables for curvature and axial deformations that evolve according to first order nonlinear ordinary differential equations (ODEs), referred to as evolution equations, and the yield function. Hence, the governing dynamic equilibrium equations and hysteretic evolution equations can thus be concisely presented as a system of first-order nonlinear ODEs that can be solved using general ODE solvers without the need for linearization. The approach is applied for the design of frame structures with an objective to minimize the total volume in the domain, such that the maximum displacement at specified node(s) satisfies a specified constraint (i.e., drift limit) for the given excitation. The maximum displacement is approximated using the p-norm and thus permits the completion of the analytical sensitivities required for gradient-based updating. Several numerical examples are presented to demonstrate the approach for the design of structural frames subjected to pulse, harmonic, and seismic base excitation. Topologies obtained using the suggested, nonlinear approach are compared to solutions obtained from topology optimization problems assuming linear-elastic material behavior. These comparisons show that although similarities between the designs exist, in general the nonlinear designs differ in composition and, importantly, outperform the linear designs when assessed by nonlinear dynamic analysis.

Many thermomechanical processes, such as rolling, turning, grinding, welding or additive manufacturing, involve either a material flowing through a fixed load system or a heat source moving with respect to the material. In many situations, these processes involve a constant speed translational, rotational or helical movement of the loading with respect to the material so that a (quasi-) steady thermo-mechanical state is achieved quickly. Classical Lagrangian steady state finite element simulation of these processes in the material’s frame is a heavy task requiring large meshes refined all along the load path. This article presents a nodal-integration-based finite element method for solving transient and steady-state elastoplastic problems associated with these processes. The simulation is carried out step by step in a frame linked to the loading. As the nodes of the mesh do not represent material points, the computation procedure requires determining the position at the previous time step of the material point associated with each node ( anterior point ) in order to perform the time-integration of the constitutive equations. The anterior points are located anywhere in the mesh and therefore interpolation techniques are required to get the previous mechanical state there. As all the mechanical variables are calculated at nodes with the method proposed, this approach makes the interpolation more straightforward. Applications to 3D forming and welding are presented to illustrate the efficiency of the proposed method. The results of finite element simulations in the frame tied to the loading are compared to those of Lagrangian calculations simulating the load motion in the material’s frame. The applications demonstrate that the proposed model can significantly accelerate simulations, achieving a maximum acceleration of around 40 in 3D forming and about 4 in welding. These results highlight the substantial efficiency improvements enabled by the proposed method.

Buckling restrained braces (BRBs) as metallic dampers can supply stable and balanced hysteretic response. While BRBs exhibit outstanding energy dissipation capacity, their low post-yield stiffness contributes to large residual drift concentration in simply supported buckling restrained braced frames. The present study introduces a novel all-steel tube-in-tube BRB composed of a short-length hybrid core serially connected to a non-yielding robust member. The hybrid core includes short-length yielding members made up of circular hollow sections surrounded by an all-steel encasing system. High strain hardening capacity of short-length hybrid core enhances the post-yield stiffness, thus reducing the residual drift in simply supported buckling restrained braced frame. In this paper, first the components of proposed brace are represented in detail. Subsequently, the design procedure and stability analysis results are provided. The feasibility of conceptual hybrid BRB is evaluated by finite element analysis method. Afterwards, the global response of prototype buckling restrained braced frames comprising conventional and proposed braces are appraised via pushover and nonlinear time history analyses. The analyses results designated the significant efficiency of proposed braces to help mitigate inter-story and particularly residual drifts in buckling restrained braced frames.

This paper presents a nonlinear time-history reassessment of an existing reinforced concrete frame building originally designed in 2007 according to the Romanian seismic code P100-1/2006 and re-evaluated under current seismic demand. Two three-dimensional solid finite-element models were developed in ANSYS Workbench 2025 R2: a bare reinforced concrete frame and an infilled frame with masonry panels. A distinctive feature of the modelling strategy is the explicit representation of longitudinal and transverse reinforcement embedded in the concrete solids, which allows direct tracking of steel stress demand and post-cracking load transfer. The models were subjected to bidirectional ground motions from the Vrancea 1977 and 1990 earthquakes and the Türkiye 2023 earthquake, scaled to the P100-1/2013 target spectrum for the investigated site. The results show that masonry infills markedly increase global stiffness and reduce displacement-related demand, with substantially lower roof displacements and interstorey drift measures in the infilled configuration. The bidirectional response remains predominantly translational, while the local stress and inelasticity fields indicate qualitative concentration zones in the frame, masonry panels, and staircase region. Overall, the study shows that masonry infills can strongly modify the actual seismic response of existing reinforced concrete frame buildings and should be considered explicitly in performance assessment.

Morphing wings allow aircrafts to exhibit good aerodynamic performance at multiple points within a flight envelope. However, forthcoming aircraft designed for cross-speed domain operations impose fresh demands, particularly in the realm of wing shape adjustments, such as transient morphing. Inspired by the diving process of the northern gannet, this study proposes a morphing-wing eight-bar mechanism for transient variable sweeping under high-speed conditions. A comprehensive analysis of the rigid-flexible coupling dynamic models of the mechanism is developed by employing the finite-element floating frame of reference formulation. To numerically solve the dynamic equations, a concise reduced-order algorithm that included static equilibrium compensation is introduced. The maximum dynamic stress encountered during the morphing process at various speeds and time ratio at which each link is subjected to the maximum stress, referred to as the maximum stress-time ratio of each link, are evaluated. The results show that the maximum dynamic stress and maximum stress–time ratio serve as effective measures of the performance of the mechanism under high-speed working conditions. Although the proposed eight-bar variable-sweepback-wing mechanism requires further structural optimization to achieve superior high-speed performance, it demonstrates potential for high-speed applications.

Many studies have been carried out for understanding the mechanism of failure of RC structural systems under varying temperature circumstances. Similarly, several methods have been developed for improving the fire resistance of concrete buildings, with respect to material selection and detailing aspects. However, only some of the researchers have concentrated on composite behavior of interaction between the structural elements and functional elements, like interaction between masonry infill walls and RC frame elements in the emergence of fire. Several numerical models have been developed for analysis of infilled frames. For simulating the action of fire on full-scale reinforced concrete buildings, three factors, namely, presence of loading, place of fire, its intensity, and duration, must be considered since the material behavior depends on the stress level, intensity and duration of fire and the sensitiveness of structural element to the location and application of fire. To consider the combined effect of load and high temperature, finite element analysis is used. For simulating the intensity and time factor for temperature rise, transient state studies must be done.

In this paper, we investigate the seismic response of 2D building subjected to harmonic sinusoidal forces at the base with varying frequencies. Linear time history analysis (LTHA) is employed to evaluate the dynamic behavior of 2-story 4-bays reinforced concrete (RC) shear frame to capture the structural response across resonance conditions. To ensure an accurate assessment of vibration responses, both analytical methods (Modal analysis and Duhamel integration) and numerical approaches (Newmark Beta and Wilson Theta) are employed. Additionally, Finite Element Analysis (FEA) is performed using the SAP2000 software to compare the results. The study reveals that the excitation frequency significantly influences displacement and interstory drift responses. High-frequency excitation does not produce large displacements of the floors. This work highlights the importance of considering both excitation characteristics and structural properties in seismic design, and it emphasizes the significance of integration analytical and numerical methods in modern seismic engineering practices.

The increased interest in tall timber buildings has led to the need for more accurate prediction models. With inherently low mass and stiffness properties, multi-story buildings made of timber are susceptible to wind-induced vibrations, which can result in discomfort for the occupants. Multiple experimental and numerical studies investigating natural frequencies and mode shapes of timber buildings can be found in the literature. However, modeling the damping properties in timber buildings has not been studied fully yet. This study presents a framework for the estimation of the global damping ratio of glue–laminated-frame buildings by use of linear-elastic finite element modeling. Using stiffness-dependent Rayleigh damping and the dynamic analysis in the time domain, it was demonstrated that the predictions of the FE model for the damping ratio were within the range of the results obtained by on-site measurements. The case study of the tallest all-timber building in the world (Mjøstårnet, Norway) was used to demonstrate the framework using extensive small- and large-scale experimental data. The parametric study identified the damping ratio in the diagonals and material damping ratio in the glue–laminated timber as the key parameters influencing the damping ratio of the whole building.

The dynamic cumulative damage of rigid-flexible coupling model of high-speed train with flexible bogie frame is performed by using the coupled scheme of elastic and multibody dynamics theories. The motion equations of the present problem are firstly established by integrating the finite element method and floating frame of reference approach based on the virtual power principle and D’Alembert principle. The process of condensing the elastic DOFs of the obtained finite element model involving the incorporation of the substructure technique and sparse approximate inverse method is tentatively carried out. Then, the motion equations are further solved by virtue of the generalized α method and the Jacobian-free Newton–Krylov technologies. And the superiority of coupled scheme is proven by comparing with the traditional approach. Finally, besides the dynamic behaviors of the considered vehicle model, the time-variations of stresses on the elastic bogie frame’s dangerous nodes and the distributions of stresses of bogie frame at some specified moments are synchronously calculated and analyzed. More importantly, the real-time and time-varying cumulative damages of some typical nodes on bogie frame are investigated.