Jul 2026· Building and reconstruction· 0 citations· 9 references
Abstract
In modern design practice, a numerical method for verifying the robustness of damaged structural systems based on imitation modeling is becoming increasingly common. This method utilizes the fundamental principles of macromodeling, according to which the elastic behavior of a structural system is determined by the operation of linearly elastic rods and plates, while nonlinear behavior is completely determined by the behavior of point and/or linear plastic hinges. Thus, an adequate description of the diagrams for plastic hinges is an important element of modeling. This article presents proposals for describing the parametric points of plastic hinges for bending, shear, and axial tension, which allows for describing the operation of a damaged structural system at all stages of its operation. It is proposed to limit the maximum rotation angles during bending, taking into account the shear failure criterion. The calculation results obtained using an imitation finite element model are compared with experimental data.
Objective
. This work is devoted to a quantitative assessment of the effect of internal prestressing of reinforcement on the stress-strain state and load-bearing capacity of a thick-walled cylindrical shell.
Method
. The study is carried out through a computational experiment using the finite element method in an axisymmetric formulation. The physical nonlinearity of concrete is described by the Sargin diagram, the parameters of which are verified according to Eurocode 2 data.
Result
. An iterative algorithm based on the method of variable elasticity has been developed for correcting the secant modulus of concrete deformations. The reinforcement is modeled discretely, and the prestressing effect is specified as initial stresses in the reinforcement elements. The modeling results showed that for a cylinder made of B40 concrete with a reinforcement percentage of 3.11%, failure under internal pressure is of a deformation nature and is associated with reaching ultimate tensile strains in the concrete, rather than with the exhaustion of compressive strength. The ultimate internal pressure for a non-stressed structure is 0.55 MPa. A hoop prestressing threshold of 265 MPa has been determined. Exceeding this threshold causes unacceptable tensile stresses in concrete even before the initial operational phase. It has been shown that the optimal hoop prestressing level of 250 MPa allows for doubling the ultimate internal pressure to 1.1 MPa.
Conclusion
. The developed numerical model and calculation algorithm enable predicting the behavior of reinforced concrete structures, taking into account the actual properties of materials and process factors. The obtained results demonstrate the high effectiveness of prestressing for thick-walled cylinders and highlight the need to control not only the strength but also the deformation criteria of concrete failure.
V. V. Kuznetsov, S. V. Litvinov, T. Volosatova· Herald of Dagestan State Tec...· 0 citations
This study focuses on the capacity design of earthquake-resistant steel structures incorporating knee bracing systems, which serve as dissipative elements. It also presents the development and validation of a numerical model for simulating the behavior of these systems. The proposed model accurately captures the response of the fuse element by accounting for the interaction among axial force, shear, and bending moment, including second-order effects, while maintaining low computational demands. Model validation was performed through comparison with two independent experimental campaigns: (1) three-point bending tests on isolated fuses to characterize their local behavior, and (2) cyclic push-over tests on a full-scale, single-story frame to evaluate the global response of the system under lateral loading. Following the validation, an extensive parametric study was carried out via nonlinear static analyses on a multi-story, multi-bay steel frame with semi-rigid joints equipped with knee bracing systems. The investigation examined the influence of the axial forces in the fuses, the fuse cross-sectional typology, the joint rotational stiffness, and the lateral load distribution. The proposed model provides a practical and computationally efficient tool to support performance-based design and optimization of energy-dissipative devices in steel frame structures. The paper also provides a series of design recommendations for practitioners involved in designing earthquake-resistant structures with knee bracing systems.
R. Piazzon, F. Gusella, P. Zampieri· Bulletin of Earthquake Engin...· 0 citations
Based on first-order shear deformation theory and the Rayleigh-Ritz method, this paper establishes the dynamic model for a cylindrical shell with various boundary conditions (fixed, simply supported, free or elastically supported etc.) by means of Chebyshev polynomials and the artificial boundary spring method. To validate the proposed approach, a comparative study is first conducted with existing literature, finite element simulations, and experimental modal tests. The results demonstrate that the method can accurately predict the natural frequencies and mode shapes of the shell. Subsequently, the method of multiple scales is introduced to perform a perturbation analysis of the nonlinear governing equations. Through polar coordinate transformations, the four-dimensional averaged equations of the system are derived. Finally, based on the averaged equations, the amplitude–frequency response characteristics are systematically analyzed, revealing typical nonlinear phenomena such as multi-valued solutions, jump instabilities, and softening–hardening spring behaviors. Furthermore, the Runge–Kutta algorithm is employed to obtain the bifurcation diagrams, phase portraits, Poincaré maps, and maximum Lyapunov exponents. The results indicate that the external excitation amplitude acts as the dominant parameter inducing bifurcations and chaos, whereas the detuning parameter exhibits a weakly sensitive local perturbation effect.
Haotian Song, S. Lu· Sound & Vibration· 0 citations
Introduction
. The article analyses the stress-strain states of reinforced concrete elements when calculating the strength of normal sections using a nonlinear deformation model NDM, proposes a method for describing axial deformations and forced in the form of function parameters, introduces criteria for grouping deformed states based on emerging forces. An analytical method is proposed for determining the limiting forces in the normal section of a reinforced concrete element when calculating strength according to NDM.
Aim.
Development of a methodology for finding the limiting forces at which there is no significant degradation of the rigidity of the normal section in a reinforced concrete element when calculating using the NDM, which does not require the use of numerical modeling tools.
Results.
The results of the research showed that recording the deformed states of the section in the form of parameters of the axial deformation equation makes it possible to describe the mechanisms of NDM in the form of a system of nonlinear equations, which makes it possible to express direct analytical dependencies for finding deformations from forces. A group of stressstrain states of normal sections has been identified, which can be characterized, from the point of view of forces, as close to the maximum possible (about 90…100 % in bending moment), and from the point of view of rigidity as a boundary, after crossing which a sharp degradation of the rigidity characteristics of the section is observed. Analytical dependencies describing the identified group made it possible to abandon the use of numerical methods to determine limiting forces according to NDM.
Conclusions. A method for determining the limiting forces in the normal section of reinforced concrete elements when calculating according to the NDM has been developed, which does not require the use of numerical models. The essence of the method lies in the established mutual dependencies between the parameters of equation of the deformed state of the section, at which forces close to maximum possible are observed in it, and there is no sharp degradation of the rigidity characteristics of the normal sections.
D. Rusanov, S. Serbin· Concrete and Reinforced Conc...· 0 citations
The article presents a mathematical model for the loss of stability in a continuous welded rail system, based on the analysis of the deformed shape of an equivalent beam that simulates the rail-sleeper grid. The deformed area of an equivalent infinitely long beam divided into a buckling region characterized by transverse displacements and adjacent regions where only compression occurs. The length of the regions is unknown and determined during the solution. The distinctive feature of the proposed model is to take into account the release of compressive forces after loss of stability, as well as the non-linearity of deformations, but with the preservation of the Bernoulli hypothesis. The law of changing the compressive force depends on the accepted law of changing the resistance of the environment in which the deformation occurs. Model has been improved to account for the nonlinearity of resistance to longitudinal and transverse cross-section displacements of the equivalent beam. Resistance functions are obtained by the approximation of experimental points using the least squares method, non-linear in case of transverse resistance approximation. The system of non-linear differential equations, which is closed by boundary conditions and transversality conditions, is solved by the finite difference method. The difference equations use central difference formulas, which require a minimum length of the template. The solution is made by a method of successive approximations, ensuring a sufficient number of grid nodes. The results of track stability parameters calculations are presented. Including the critical value of the heating temperature of the rails above the fixing temperature, at which a stable deformed shape can exist. The results of the solution according to the refined model are compared with the results of the model with constant resistance and with the results of the model without the release of the compressive force. Refinement of the model by taking into account non-linearities of various natures is important for assessing the pre-critical state of a continuous welded track.
P. Smirnov· Bulletin of Siberian State U...· 0 citations
The paper investigates the nonlinear torsional dynamics of drill strings using mathematical and computational modeling. The study is motivated by the need to improve the reliability and efficiency of drilling processes under conditions when torsional vibrations affect the performance and the safety of drilling systems. A nonlinear mathematical model of the drill string is developed by treating it as a deformable rod with distributed parameters. The governing equations are derived from the Hamilton-Ostrogradsky variational principle under the assumption of finite strains within the framework of nonlinear elasticity. The distributed-parameter problem is reduced to a finite-dimensional system by means of the Bubnov-Galerkin method. Numerical simulations are performed to analyze the dynamic response of the considered systems and to evaluate the influence of geometric, dynamic, and physical parameters on drill string vibrations. The results show the effect of drill string length, angular velocity of the drill string, and material properties on the amplitude, frequency characteristics, modal interaction, and phase-plane structure of the nonlinear torsional response.
L. Khajiyeva, M. M. Jantassova, A. Kudaibergenov· WSEAS Transactions on Applie...· 0 citations
