Numerical simulation of the behavior of kinematically unstable slopes under dynamic influences

Introduction. The concept of estimating the dynamic parameters of the “base — weakened layer — block” system is proposed, taking into account the physical nonlinearity of the material and the kinematic method of excitation of vibrations. In accordance with this approach, the physical nonlinearity of the base and block material is considered using the Drucker- Prager model. The weakened layer is modeled by 3D spring finite elements. The verification procedure of the proposed methodology is carried out on the example of the dynamic calculation of the “base — weakened layer — slope” system.Materials and Methods. The computational experiments were performed using the ANSYS Mechanical software package in combination with a nonlinear solver based on the Newton-Raphson procedure. SOLID45 volumetric finite elements were used to discretize the computational domains. Combined elastic-viscous elements COMBIN14 were used to simulate the displacement of the block relative to the fixed base.Results. An engineering technique for the dynamic analysis of the stress-strain state of the “base — weakened layer — block” spatial system with kinematic method of excitation of vibrations is developed. The accuracy and convergence of the proposed method is investigated using specific numerical examples.Discussion and Conclusion. Based on the mathematic simulation performed, it is shown that the developed technique provides assessing the risks of the occurrence of real landslide processes caused by external non-stationary impacts.

SUBSTANTIATION OF DESIGN DECISIONS OF ELEMENTS OF MILITARY OBJECTS IN CONDITIONS OF CONTACT AND PLASTIC DEFORMATION

New design solutions, technologies and materials are required to improve tactical and technical characteristics of military equipment. Often this implies operation in such conditions as contact interaction and elasto-plastic deformations of materials. New models and research methods are developed for better utilization of modern materials and improved performance of military equipment. They account directly for complex physical and structural nonlinearities. The properties of conventional and novel materials are determined both in bulk and on surfaces at microstructural level. This will enable physically adequate and mathematically correct analysis of stress-strain state. The new advanced design solutions will emerge through the objective-driven search by means of parametric modeling. The project will extend traditional local problem statements with newly developed variational principles that account for structural and physical nonlinearity and are suitable for parameterization. This will create the basis for fundamental analysis of torsion bar suspensions, hydrovolumetric and gear drives and other crucial components of combat vehicles, engineering solutions for domestic manufacturers of military equipment that will bring their tactical and technical characteristics to highest modern standards. Keywords: contact interaction; stress-strain state; intermediate layer; contact pressure; contact area; plastic deformation

CALCULATION OF CENTRALLY COMPRESSED CONCRETE FILLED STEEL TUBULAR COLUMNS OF ANNULAR SECTION TAKING INTO ACCOUNT PHYSICAL NONLINEARITY

In the article, the resolving equations are obtained for the calculation taking into account the physical nonlinearity and creep of centrally compressed concrete filled steel tubular columns of annular cross-section. The examples of the calculation of the bearing capacity with a short-term load are given. The solution was carried out numerically in the Matlab environment using the finite difference method. The deformation theory of plasticity by G.A. Geniev was used.

Matrix Description of Non-Linear Properties of Materials or Structural Components—Idea and Application Examples

Numerical methods are widely used in structural analysis problems. In the cases of the most complex and practical problems, they are often the only way to obtain solutions, as analytical methods prove ineffective. The motivation for this paper was the desire to extend the scope of numerical methods to cover the problems of creating constitutive models of structural materials. The aim of this research was to develop a matrix or numerical discrete constitutive model of materials. It presents the general assumptions of the developed method for modeling the physical properties of materials. The matrix model is only useful with an appropriate numerical algorithm. Such an algorithm was created and described in this paper. Based on its findings, computer software was developed to perform numerical simulations. Presented calculation examples confirmed the effectiveness of the developed method to create constitutive matrix models of various typical materials, such as steel, but also, e.g., hyper-elastic materials. It also presents the usefulness of constitutive matrix models for simulations of simple stress states and analyses of structural elements such as reinforced concrete. All presented examples involved the physical nonlinearity of the materials. It is proved that the developed matrix constitutive model of materials is efficient and quite versatile. In complex analyses of structures made of nonlinear materials, it can be used as an effective alternative to classical constitutive or analytical models based on elementary mathematical functions.

EVALUATION OF THE RELIABILITY OF BUILDING STRUCTURES IN SIMULIA ABAQUS: MODELING OF STOCHASTIC MATERIAL PROPERTIES

This article describes a software module component integrated with the SIMULIA Abaqus engineering analysis software package and designed to simulate random values of material parameters in a finiteelement model based on specifiedstatistical characteristics, with the possibility of taking into account the physical nonlinearity of material behavior under various combinations of loads and influences.The target group of materials under study is materials of load-bearing elements of building structures, such as concrete, stone, steel. This software module can be recommended for use by specialists, engineers and scientists engaged in probabilistic analysis of the reliability of structures of buildings and structures, apparatus, machines, devices, with the combined use of complexes of computer modeling and engineering analysis. Has a certificateof state registration of the computer program "AS for modeling stochastic properties of materials" No. 2019667439 dated 12.24.2019.

MODELING OF THE SUBWAY DYNAMIC INFLUANCE ON THE GROUND STRUCTURE

The article discusses a new approach to modeling the behavior of structures under the influence of dynamic loads, including loads from ground and underground transport. The approach is to apply the direct integration method, as well as the SBFEM method to calculate the forces in load-bearing building structures under dynamic influences, taking into account a number of factors - the damping properties of the subgrade, physical nonlinearity of soils and the passage of waves in the soil space. The article presents the main theoretical premises, the results of a numerical experiment of a real monolithic building, built in the zone of influence of the subway.

Comparison of Different Procedures for Progressive Collapse Analysis of RC Flat Slab Structures under Corner Column Loss Scenario

Progressive collapse is the failure of the whole structure caused by local damage, which leads to significant economic and human losses. Therefore, structures should be designed to sustain local failures and resist subsequent nonproportional damage. This paper compared four procedures for a progressive collapse analysis of two RC structures subjected to a corner column loss scenario. The study is mainly based on the methods outlined in the current Russian standard (linear static (LS) pulldown, nonlinear static (ND) pulldown, and nonlinear dynamic), but also includes LS and NS pushdown procedures suggested by the American guidelines and linear dynamic procedure. We developed detailed finite element models for ANSYS Mechanical and ANSYS/LS-DYNA simulations, explicitly including concrete and reinforcement elements. We applied the Continuous Surface Cap Model (MAT_CSCM) to account for the physical nonlinearity of concrete. We also validated results obtained following these procedures against known experimental data. Simulations using linear static pulldown and linear dynamic procedures lead to 50–70% lower results than the experimental because they do not account for the nonlinear behavior of concrete and reinforcement. Displacements obtained from the NS pulldown method exceed the test data by 10–400%. It is found that correct results for both RC structures can only be found using a nonlinear dynamic procedure, and the mismatch with the test data do not exceed 7%. Compared to static pulldown methods, LS and NS pushdown methods are more accurate and differ from the experiment by 28% and 14%, respectively. This relative accuracy is provided by more correct load multipliers depending on the structure type.

Finite element modeling of the joint action of flow slide and protective structure

Introduction. In the context of the problem of plane deformation, a finite-element model of a natural landslide slope is developed. It allows for the joint work of a flow slide and a protective engineering structure. The Drucker-Prager model is used to take into account the physical nonlinearity of the slope layer material. To activate the kinematic instability, a viscoelastic interlayer is introduced into the design scheme, along which the landslide layer slides.Materials and Methods. Numerical experiments were performed using the ANSYS Mechanical software package, which implements the finite element method in the form of the displacement method. Slope discretization is performed on the basis of PLANE42 flat four-node finite elements. To simulate the displacement of the landslide layer relative to the fixed base, the combined viscoelastic elements COMBIN14 were used.Results. A physically nonlinear model of a natural landslide slope consisting of a base, a landslide layer, and a viscoelastic interlayer, is formalized. An engineering technique for analyzing the stress-strain state of the “slopeprotective structure” system has been developed, taking into account the kinematic instability of the landslide layer. A series of computational experiments was carried out.Discussion and Conclusion. Based on the calculations performed, it is shown that the proposed method enables to specify the force action of the landslide layer on the protective structure and, thereby, to increase the reliability of the risk assessment when activating the landslide process.

LOAD-BEARING CAPACITY OF THE FLANGE CONNECTION OF BEAMS, COVERING OF A SINGLE-STOREY INDUSTRIAL BUILDING TAKING INTO ACCOUNT ITS MUSHROOM SHAPE

The article deals with issues related to the analysis of steel frame structures. The subject of the study is the construction sector. The object of research is flanged joints of beams of coverings of one-storey industrial buildings. In order to achieve these goals, the following methods are used: analysis, synthesis, description, generalization and comparison. According to the results of the work, the features of forming the quality of interaction between flanged joints and high-strength bolts in the form of a nodal connection of coating beams are determined. Additionally, the analysis of features during the design work and production of flanged connections used for the implementation of popular design solutions for steel cross frames of single-storey buildings is carried out. The main directions of analysis of the state of steel structures in the presence of signs of deformation (mushroom shape) of the flange connection are disclosed. The obtained data helps to optimize the composition of structural reinforcement elements, as well as reduce the level of labor intensity in the production and installation of flange joints of single-storey buildings’ coating beams. In the course of the study, an experiment is conducted in which the principle of symmetry is used. The unidirectional connection in and between nodes is modeled using the elements considered. In this case, it is necessary to mention the phenomenon of the adhesive effect of the nodes during compression and the lack of adhesion during tension. The model takes into account the physical nonlinearity of the material properties, the behavior of which is set by bilinear dependencies under load