Structural Mechanics of Engineering Constructions and Buildings

The article presents a methodology for nonlinear static analysis of slab-and-beam structures using finite elements constructed using the three-dimensional theory of elasticity and plasticity. Multilayer plate/shell elements and solid beam elements (superelements) are used to analyze structures made of heterogeneous materials, including reinforced concrete. In most currently used software products, beam finite elements are constructed either on the basis of the classical theory of strength of materials or on the basis of the three-dimensional elasticity theory. When using the three-dimensional theory, restrictions are introduced on the shape and size of cross-sections, and all characteristics are reduced to points lying in the end sections of the beams along their axes. Both of these approaches make it difficult to simultaneously take into account physical and geometric nonlinearity, therefore the development of alternative methods for nonlinear static analysis of structures is relevant. To avoid this drawback, a superelement for modeling reinforced concrete columns and beams as part of combined slab-and-beam systems is proposed in this article. To date, there are no alternatives of the proposed superelement for analyzing reinforced concrete structures in known commercial finite element products. The developed methodology is adapted to the PRINS software. An example of calculating the load-bearing capacity of a two-story frame using this software is given. The PRINS software can be used by engineers of design and scientific organizations to solve engineering problems related to the analysis of reinforced concrete structures.

Abstract. In view of the wide application of composite structures in engineering practice, an important task is to study their stress-strain state under the action of various loads. An orthotropic rectangular plate simply supported on four sides was considered. The stress-strain state of the plate under the action of a normally applied load was investigated. General analytical expressions are obtained that allow determining the stress-strain state in an orthotropic plate for different geometric parameters of the plate, for different elastic characteristics of the plate material and for different dimensions of the loading area. Using the derived general analytical expressions, various particular solutions can be obtained: under the action of a normal load applied over the entire surface of the plate, under the action of local and concentrated loads. The results of calculations of an orthotropic carbon fiber plate under the action of a uniformly distributed load applied over the entire surface of the plate are presented as a test problem. To obtain the resolving differential equation, operational calculus associated with the Laplace transform was used.

The study addresses the stress-strain state stages of reinforced concrete frames in zones of potential local collapse due to failure of a vertical element, such as a column or pylon. The paper provides initial assumptions about the mechanisms of secondary failure propagation in multi-storey reinforced concrete building frames, depending on the initial local collapse scenario. Based on these assumptions, the paper formulates force and deformation criteria for the stress-strain state stages of reinforced concrete building frames in the zone of potential local collapse. Using energy balance conditions, simplified relations were developed to estimate the ultimate static load for compressive arch and catenary actions of floor slab structures. The calculated force and deformation criteria values were compared with the experimental values. These comparisons demonstrate that the accuracy of the proposed relations is acceptable for engineering calculations.

Estimating the load-bearing capacity and predicting the residual strength of existing structures is one of the most difficult tasks. Such prediction is usually performed on the basis of experimental destructive testing of samples. A methodology for predicting the residual strength of wooden structures is proposed, based on the results of experimental studies to determine the short-term resistance of pure wood. Wooden rafter systems of residential buildings built in the 1950s and early 1960s in Vladimir were chosen as objects of research. Interpolation and extrapolation methods were used to build a predictive model of the residual life of a structure. Detailed calculations are given, which clearly show the possibility of using these methods. It is determined that the autoregression method (Burg method) shows good predictive results, correlating with experimental data from other studies and theoretical assumptions. Forecasting the remaining life of a structure is a key factor in ensuring the reliability and safety of buildings, as well as reducing future operating costs.

The development of layered structures represents a viable and promising avenue in the field of construction, as their utilization has the potential to significantly enhance strength characteristics, resistance against external forces, as well as enhance the thermal and acoustic insulation properties of buildings and structures. The aim of this study is to investigate the diversity and benefits of utilizing multilayer building components as an alternative to conventional structures, as well as to analyze the characteristics of their operation. Based on the findings of the study, it can be inferred that multilayered structures offer enhanced thermal and acoustic insulation characteristics, which contribute to the creation of a more comfortable living and working environment. Additionally, these structures can significantly decrease the weight of buildings, leading to potential savings in foundation and other structural components.