Aug 2026· Herald of Dagestan State Technical University. Technical Sciences· Vol 53, pp. 210-222· 0 citations· 4 references
Abstract
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.
The article presents tools for creating computational models of reinforced concrete resistance based on the concepts of "representative volume" and "characteristic zone". The tools are based on the idea of modeling zones of a structure characteristic of the type of stress state in the form of a composite strip-prism, which are described by a volume representative of the considered type of stress state, including under load-varying force flows due to crack opening-closing, shear cracks, changes in distances between main cracks, and, accordingly, changes in the stiffness of the representative volume along the three axes.
The proposed model allows determining the resistance of a reinforced concrete structure with various types of stress states in characteristic zones of the deformable space, considering the type of concrete, reinforcement classes, and specific weights of their areas, as well as considering the deformation effect during crack opening established by the author based on the fracture mechanics functional using a double-cantilever element (DCE).
V. Kolchunov· Building and reconstruction· 0 citations
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.
The paper investigates the stress-strain state of critical detachable joints (keyed and threaded) in solid-propellant rocket motors. The purpose of the research is to study the stress-strain state of critical components in rocket technology (using the example of threaded and keyed joints) based on a comparative analysis of the results of numerical modeling in ANSYS and field experiments using photoelasticity.
The authors propose a comprehensive approach to ensure high reliability, combining finite element modeling in ANSYS with experimental validation via the photoelastic method. The scientific novelty of the research consists in acquiring more accurate data regarding the stress state of the components under study by introducing a "virtual photoelasticity" algorithm for direct quantitative validation of numerical results. Furthermore, 3D-printing is utilized as an efficient technological tool for the manufacturing of optical models. Critical stress concentrators are identified in thread roots and keyway corners.
Results demonstrate high convergence between numerical and physical experiments (the relative error is 0.57 % for the threaded connection and 3.4 % for the keyed connection), confirming the accuracy of the calculation models. The practical significance of the work is that the tested methodology can be used both in the early stages of design and for the strength optimization of the existing structures geometry.
K. V. Krivun, A. A. Pescherova, A. A. Lazareva· Omsk Scientific Bulletin Ser...· 0 citations
The aim of the study is to optimize the structure of a polymer composite with continuous longitudinal reinforcement for lighting masts by numerically simulating their stress–strain state under extreme wind loads.A three-layer composite mast (epoxy matrix reinforced with fiberglass or carbon fiber) with an outer diameter of 90 mm, a wall thickness of 5 mm, and a height of 4 m was investigated. A comparison with the base aluminum structure (6060-T6 alloy) was performed using finite element analysis (FEA) in the Ansys software suite. The combined effect of storm wind (25 m/s), lighting device mass (5 kg), and aerodynamic pressure was taken into account. The volume fraction of fibers (40, 60, 80%) and the spatial location of the reinforced layer (inner, central, outer) in the cross-section were varied.The use of polymer composites reduces the mast mass by 50–52% compared to the aluminum analogue (14.42 kg). Replacing fiberglass with carbon fiber additionally reduces the mass by ~10%. Increasing the fiberglass volume fraction from 40 to 80% increases the mass from 6.70 to 7.86 kg, reducing the maximum displacements of the mast top from 4.04 to 3.51 mm. The configuration with a reinforced inner layer provides the highest stiffness: deflections are 2.02–2.04 mm, equivalent stresses are 1.11–3.42 MPa, and the factor of safety reaches a maximum of 704–824. Reinforcing the outer layer increases equivalent stresses up to 5.22 MPa and reduces the factor of safety to ~260. Carbon fibers generate higher stresses (up to 5.22 MPa versus 3.03 MPa for fiberglass) due to a higher modulus of elasticity and local load concentration. Their higher strength limits (up to 2407 MPa) provide an average factor of safety (~575) close to that of fiberglass. The base aluminum mast has the smallest deflections (0.07 mm) but a significantly lower factor of safety (214). A structure with fiberglass in the inner layer at a volume fraction of 60–80% was determined to be rational for street lighting.The patterns of local stiffness redistribution in tubular composite elements depending on the configuration of longitudinal continuous fibers were established. The possibility of targeted control of the mast strength without changing its geometry was proven, which is implemented in serial production using the developed direct extrusion technology.
I. Mikulionok, O. Sokolskyi, D. Shvets et al.· Herald of Khmelnytskyi Natio...· 0 citations
This study investigates the nonlinear bending behavior of circular thin reinforced concrete (RC) and steel-reinforced concrete (SRC) plates under short-term and long-term loading, with particular attention to the influence of support contour compliance. A calculation framework is developed for the stress-strain analysis of axisymmetrically loaded circular plates by accounting for geometric nonlinearity, material nonlinearity, reinforcement effects, and time-dependent deformation. Experimental studies were carried out on circular RC plate models interacting with a support ring, and the measured deflections were compared with theoretical predictions. The results show that the proposed model captures the main features of plate deformation, including the nonlinear increase in deflection with load and the redistribution of the stress-strain state near the contour. For the considered loading cases, the discrepancy between calculated and experimental deflections did not exceed 17 %, which confirms the engineering applicability of the developed approach. It is also shown that support contour compliance significantly affects the long-term behavior and load-bearing response of the plates. The obtained results can be used to improve the design and assessment of circular RC and SRC plates, especially in structures where nonlinear effects and contour deformability must be taken into account.
Kh.S. Razzokov, J. Razzokov, Ikramboy Sattarov· Vibroengineering PROCEDIA· 0 citations
The present work aims to analyze and calibrate the mechanical description of plastic strain-induced anisotropy and damage coupling by the so-called Concrete Damaged Plasticity (CDP) constitutive model, which is rather well known, also since it has become available within popular FEM platforms, such as ABAQUS, and shall reproduce typical features of failure processes in quasi-brittle materials, such as concrete. This is achieved by combining an effective stress-based non-associative hardening/softening plasticity model with an isotropic damage model based on plastic strains, at a smeared continuum scale. In the paper, focusing on the mere elastoplastic coupling for tensile-dominated responses, and introducing an enhanced tuning by setting tensile exponential softening and damage evolutions through a convenient plastic to inelastic strain ratio parameter, by means of an external user implementation, an exhaustive numerical parametrization analysis is performed, starting at a constitutive-driver level, to experiment with the outcomes of the constitutive description and to quantify the amount of material anisotropy induced by plastic deformation, under biaxial elongation/shearing Willam’s test, which prescribes/involves the rotation of the principal axes of strains/stresses. It is shown that the constitutive response is effectively regularized, allowing to fulfil the requirements of Willam’s test, independently of the amount of inherent plastic dilatancy, showing a rather mild presence of plastic-induced anisotropy, at the pure constitutive-driver scale. Furthermore, first extrapolating implications and outcomes at the small (specimen) structural scale are also investigated, with clear appearance of strain localization and related much pronounced plastic-induced anisotropy, in the (imperfection-triggered) macroscopic response, with features that are similar to those coming, for example, from more sophisticated anisotropic damage models, while significant practical applications may subsequently follow, within different structural engineering contexts, such as that of large-scale concrete structures under static and dynamic loading scenarios, toward informed safety assessment and evaluation.
D. Froio, R. Ferrari, E. Rizzi· Frontiers in Materials· 0 citations