No abstract

On the basis of modern numerical implementations of the finite element method the article presents the justification of the adequacy of the method of solving the problems of structures straining in their contact interaction with the elastic-plastic nonlinear soil medium. Compatible calculations of structures and nonlinear bases, which are described by modern mechanical and soil models within one problem is a significant technical problem. The solution of the assigned tasks is possible only within the framework of numerical methods, the most common of which is the finite element method (FEM). The construction of the computational finite element model raises many complex questions that require additional detailed study. In addition, the compliance with the state building norms and regulations is an important factor for further practical use. The use of numerical methods in the calculation of machines and structures, taking into account their interaction with the elastic-plastic medium is largely determined by the complexity or even impossibility of analytical calculation due to the complexity of structural schemes, heterogeneity of material features, uneven soil layers, implementation of step-by-step work execution technologies and so on. The combination of the latest achievements in the field of structural mechanics and soil mechanics is a promising direction for the development of effective approaches to building discrete models of space systems “structure-nonlinear base” for solving applied problems. The use of the developed method allows to significantly specify the structures stress state interacting with the soil base, and to significantly specify the impact on the calculated level of the base bearing capacity. Only the simultaneous consideration of the nonlinear resistance of the soil base together with the plasticity and the structure destruction in the numerical simulation of the foundation-shell load provided good agreement with the natural experiment data as to the type of the boundary state and the bearing capacity level.

All mechanisms and structures consist of parts interacting with each other, and the distribution of contact forces between these parts is unknown in advance and can only be found as a result of solving specific problems, called contact problems.Calculation of the stress-strain state under force contact conditions is important because in many cases the contact zone is a probable zone of loss of strength and a zone of structural failure.Data on the stress-strain state of such elements and units can be obtained using a modern apparatus of mathematical modeling - such as the finite element method. The paper presents a methodology for modeling nonlinear contact problems in calculations of nodal connections of steel structures. Modeling of contact interaction is performed by the example of a truss support node made of bent-welded profiles in the integrated software system SCAD Office. The developed method is based on the penalty function method, which is based on the concept of contact layer and contact elements with special properties. The contact interaction is modeled using one-way connections. The node model is calculated and investigated as geometrically nonlinear based on the method of stepwise analysis. The contact forces - stress and contact normal forces - in a steel truss support node have been determined. The obtained data have been analyzed and the deformed models of the nodal connection for the contact and noncontact formulations of the problem have been compared.It is possible to use the results to further investigate the contact stresses arising from the interaction of the elements of the truss support assembly. Taking into account the contact interaction of the elements in the calculation of the most important joints of the frame allows you to correctly assess the stress-strain state of the structures and trace the picture of the deformations of the elements, as close to the real.The research results can be used to search for contact stresses arising from the interaction of elements of the frame of civil and industrial buildings.

The reliability and efficiency of the semi-analytic finite element method in the problems of geometrically nonlinear elastic-plastic deformation of axisymmetric structures under the influence of dynamic loads are considered. The possibilities of the technique are demonstrated on the examples of numerical simulation of the building structures' stress-strain state with large linear deformations and technological operation analysis of impulse metal processing.

architectural monument. A technical inspection of the building was performed and existing defects were identified. The analysis of potential sources of dynamic influences on the building is carried out. The technique of experimental researches is developed. The technique is based on a systems approach and involves the determination of dynamic parameters with the location of sensors directly on the individual elements of the studied structures. During the study, records of continuous fixation of the distribution of active oscillations of the structure were used. Numerical values of oscillation frequencies at different external sources are obtained. The nature of the distribution of amplitude values of oscillations in structures testified to the integrity of the structure as a single dynamic system. A comprehensive approach to solving the problem of modeling complex dynamical systems is considered. A mathematical model of a fragment of structures has been developed. The elements of the model create a multilayer structure with variable elastic characteristics. The results of numerical studies of the behavior of structures, taking into account the presence of peeling plaster, indicate a significant increase in natural frequencies of oscillation (up to 10 times), taking into account the partial lack of adhesion between plaster and load-bearing structures. As a result of separation, the plaster begins to work as a separate element with its own frequency with which it can resonate with other vibrating sources. The method of experimental-numerical analysis of the object is offered. This approach is based on the premise of determining the dynamic parameters of the interaction of subsystems with each other. The obtained numerical values of dynamic parameters will be used in further monitoring of the investigated building, on the basis of which it is possible to predict possible scenarios of behavior of structures over time. The research results can be used in the restoration process for optimal fixing of plaster fragments and avoidance of resonant phenomena in operation on the basis of detailed local mathematical models.