One of the actual problems in the field of analysing loads and impacts on bearing structures is their identification. It means the point of application, the type of action and its intensity in cases where there is an impact result, but the parameters that caused this result are not determined. For example, it is an accident action, as a result of which the structure is deformed and collapsed. The solution of such problems arises when analysing accidents on load-bearing structures in construction, as well as when monitoring the deformed state of structures in time. The paper proposes to use the principles of neural network modelling to solve the problem of identifying the impact in the form of a concentrated force on the example of beam systems. The values of linear and angular nodal displacements at some action are considered as input data to neurons. As an example, the linearly deformable beam of constant stiffness is considered, the material of which is a continuous isotropic medium.

Keywords: neural network, deflections, load-bearing structure, displacement, deformation, identification

On the example of the beams, the dynamics of systems with unilateral constraints are considered. The algorithm for calculating such systems as a combination of the step method of Newmark and the Lemke algorithm that determines the work scheme of the beam in each time step is proposed. Model tasks are considered with a harmonic exciting force, suddenly applied force, impulse exposure. The numerical convergence of the solution was investigated during the thickening of the temporary grid. It is shown that the accuracy of the solution significantly depends on the determination of the moment of changing the working schemes, since the error of the solution increases with an increase in the events “inclusion/off” of unilateral constraints.

Keywords: constructive nonlinearity, unilateral constraints, linear complementary problem, Lemke's algorithm, structural dynamics, Newmark's method

A new building structure is proposed - a welded steel I-beam with a prestressed perforated wall. The prestress in the beam is created by stretching the web and subsequent welding with chords. Before prestressing, holes are cut in the wall. Using the LIRA-SAPR software package, a model is proposed that can be used to study the operation of a prestressed perforated beam (PNPB) structure. The influence of various forms of voids in the wall on the change in the stress-strain state of steel I-beams prestressed by the wall drawing is studied. A preliminary assessment was made of the favorable effect of prestressing in a conventional perforated beam on the stress-strain state of beams with different forms of perforations in the web.

Keywords: steel structures, prestressing, numerical experiment, normal and shear stresses, bearing capacity

The article discusses modern approaches to the calculation of embedded parts using the most common computing systems in the design environment. The main purpose of the work is a comparative analysis of the stress-strain state of the support plates and anchor rods when calculating in various computing complexes in order to obtain the most reliable and complete results necessary for the designer to ensure reliability when designing components of building structures. In addition to the above, the article focuses on ensuring the rigidity of the support plates, in case of compliance with which, the nodal structural element is able to withstand a single impulse impact.

Keywords: computing complexes, embedded parts, calculation methods, calculation situations, dynamic coefficient, strength indicators

The paper presents a method for calculating the stress-strain state of composite metal-wood beams, taking into account the compliance of bonds in a nonlinear setting using the SCAD software. In the course of the calculation, the pattern of stress and strain distribution, which is close to the real one, was determined. The concentrations of stresses that are capable of initiating the destruction of the structure are determined. Dangerous areas have been identified that make it possible to predict the mode of destruction of the structure, in order to organize measures to strengthen it. The results of the numerical experiment are confirmed by the materials of physical tests.

Keywords: wooden structure, composite beam, pliable connection, calculation, finite element method, stress-strain state, connection, metal-wood beam

The assumptions of mathematical models for calculating the crack resistance of reinforced concrete structures are considered. For each of them, an analysis was carried out to determine whether they correspond to reality throughout the entire life cycle of the structure: from the hardening of the concrete mix to destruction. Based on the results of the analysis, it was proposed to use only one single calculation at the level of standards to assess the crack resistance of structures - according to the crack opening width, acrc. So, for example, at a certain value of acrc, the structure will still remain airtight (the cracks will be non-through), and if this value is exceeded, it will not. At the same time, the calculations already available in the norms for limiting permeability and the safety of reinforcement will still remain in demand. At the junction of the theory of damage accumulation and nonlinear fracture mechanics, a compressed algorithm is proposed for possibly taking into account the influence of cracks at all scale levels of the concrete structure, the key for which is the normalization of the statistical parameters of the distribution of discontinuities by diameters, lengths, openings, depths, directions, distances between discontinuities, etc.

Keywords: reinforced concrete, crack resistance, cracking moment, crack width, plasticity coefficient, damageability, non-linear fracture mechanics

The article contains an analysis of the shallow elastic spherical shell on a rectangular plan, reinforced with ribs along its contour, under the uniformly distributed load. The problem is solved numerically with the variational-difference method, considering the geometric nonlineaity and the shear deformations of the shell and the ribs. As a result, the dependencies of the critical load on the shell stiffness and the ribs stiffness are obtained.

Keywords: shallow spherical shell, ribbed shell, stability, bending stiffness, geometrical nonlinearity, variational-difference method, critical load

Mechanical systems oscillate relative to the equilibrium position, and their amplitude depends on both frequency and mass, shape, design and mechanical properties of the system. There are two parameters of the grequency response of mechanical systems: the frequency of their natural vibrations and dynamicity on the effect of forced vibrations (dynamic coefficient). The purpose of the article is to investigate methods for calculating the parameters of the frequency response such a frequency of natural vibrations and the dynamic coefficient of a cantilevered steel beam. The methods which were used are analytical, finite element method with the ANSYS software environment and experimental method on the vibration stand with two loading methods: sinusoidal vibration using the swinging frequency method and broadband random vibration. The obtained natural oscillation frequency values are consistent within the relative error of 15%, dynamic coefficient values are consistent within the relative error of 5%. The finite element method is well consistent with the analytical method, while it requires fewer operations for more complex designs. Differences in the results of experiments arise from differences in the methods of loading the object of research.

Keywords: frequency response, finite element mathod, ANSYS, natural vibrarion frequency, sweep check, broadband random vibration

The application of the gas-dynamic method with the use of nonlinear dynamics to the calculation of an underground structure built into the lower floor on the impact of an air shock wave is considered, taking into account the collapse of the above-ground part of the building. It is known that one of the impacts on built-in underground structures designed to protect the population and territory from natural and man-made emergencies is the impact of a possible collapse or blockage from a higher building when exposed to an air shock wave. This task is relevant because the current methods are based on linear static calculation methods and involve certain assumptions, including when calculating for collapse, and all this can lead to difficult to estimate errors in the calculation results. Therefore, when solving these problems, which are highly non-linear and the processes under consideration themselves are fast, it is necessary to consider the use of more adequate and accurate methods based on more rigorous formulations, which is the gas-dynamic method using nonlinear dynamics.

Keywords: emergency explosive effects, air shock wave, impulse effects, non-linear gas dynamics, compression phase, rarefaction phase, underground structures, “Ambient” elements, Eulerian grids, progressive collapse, collapse of structures, destruction of structure

The article considers the method of applying dynamic effects on cylindrical mesh roofs. The necessity of taking into account oscillatory processes from operating devices and in case of mechanical failure of the attached equipment is justified. The features of the construction of structures and the location of static loads are taken into account. A specific numerical example is given in the framework of application software application. A rational grid shape with a diagonal element in the middle is adopted and acceptable ratios of geometric parameters are obtained. The defining mathematical dependencies are indicated and the dynamic load modeling process is shown. Direct integration of the equations of motion is carried out. The regularities of the influence of oscillatory processes on the operation of the roof are revealed and a visual visualization of the results is obtained. Extreme values of force factors and parameters of deformation of the structure at a given time interval are recorded.

Keywords: cylindrical mesh roof, direct integration of equations of motion, dynamic impact, force factor, deformation parameter

The points of stress concentration in the sections of structural elements are considered. These include, in particular, crack tips that may appear both during operation and as a result of a violation of their production technology. The values of stress intensity factors in the vicinity of cracks in the considered sections with contour corner points are obtained. In addition, the study of indicators in the asymptotic solution of the elasticity theory problem for bodies made of isotropic materials in the vicinity of the structure rod element corner point of the section, where the sides (or one of them) are supported by a thin coating, was carried out. On the other side of the corner region, various conditions for its reinforcement are assumed, including the presence of a thin elastic coating. Mathematically, the solution of the problem is reduced to the transcendental characteristic equation solution, that is, to the problem of finding the equation roots that is constructed from the condition for the existence of a non-zero solution to a linear homogeneous equations system. The characteristics of the stress components were determined for various combinations of boundary conditions, physical and geometric parameters. Qualitative conclusions are made. In particular, values these parameters are established combinations , at which the behavior of stresses at the section corner point becomes singular.

Keywords: stress intensity factor, isotropic elastic bodies, structural element, section corner point , crack, thin elastic coating, boundary conditions, characteristic equation, stress concentration

The unique building of the Center for Science and Art is modeled as a variant of the complex development of the territory of the old hippodrome in Rostov-on-Don. The analysis of the formation of vertical external communication parametric structures for a spherical object is performed. Based on the results of the consideration of ten forms, a rational form of "Turban" was determined, which retains a constant comfortable slope, and in emergency situations can go into autonomous mode while maintaining the rigidity of the structure. Visualization of the object's integration into the urban environment was carried out in Rhino 3D using the Grasshopper visual programming language program. By combining specialized years, modeling of roads and the volumetric geometry of buildings, the object of study, zoning and reading information from the surrounding area was carried out. The resulting model allows us to evaluate the aesthetics and comfort of the urban environment in the case of construction of a new facility.

Keywords: unique buildings, modeling, parametric architecture, urban environment, grasshopper