Masonry is a complex multicomponent composite consisting of dissimilar materials (brick / stone and mortar). Masonry deformation process under loading depends on the mechanical characteristics of the basic composite materials, as well as of the parameters of the elements defining binding between brick and mortar being the interface elements. Traditional methods of masonry modeling are based on the use of generalized ("effective") mechanical properties of the composite as a continuant homogeneous continuant medium. This paper presents an overview and analysis of continuant masonry models adequately reflecting the process of elastic, and in some cases elastic-plastic masonry deformation within the composition of stone structural elements. The paper provides analysis of the experimental research results of masonry behaviour in a biaxial stress state at primary stresses of opposite signs; identifies masonry destruction mechanisms complying with the conditions of stress state. The work demonstrates the key role played by interface elements in the formation of masonry destruction processes. Based on destruction mechanisms deduced from experiments, there was developed a discrete model of masonry. A system of masonry strength criteria was proposed corresponding to the biaxial stress state conditions at primary stresses of opposite signs. For purposes of studying the elastic-plastic deformation and destruction of masonry, there was developed a technology of numerical experiment performance using calculation technologies with a stepwise tracking of stress-and-strain state, at step-by-step loading. The scope of this paper includes verification of modeling method and technology of numerical experiment at various parameters of interface elements defining binding between bricks and mortar.

This paper focuses on the methods of calculating load-bearing systems in the case of a failure of a structural element. This kind of failure makes it necessary to assess further behavior of the structure with a possibility of the progressive collapse development. The stress-strain state analysis of a load-bearing system in the case of a failure of a structure is carried out by two main methods – static and dynamic calculation. It is shown that the static calculation (quasi-static analysis using the dynamic amplification factor) is not a universal method. This paper justifies the application of the direct dynamic calculation in the mode of direct integration of motion for the design analysis of load-bearing systems with high rigidity stories (protection structures for a load-bearing system). It also gives recommendations for selecting parameters of the direct dynamic calculation in the case of a failure analysis of a bearing structure.

1 Национальный исследовательский Московский государственный строительный университет, г. Москва, РОССИЯ 2 ООО «МонолитСтройПроект», г. Москва, РОССИЯ Аннотация: В статье рассматривается вопрос распределения напряжений в опорной зоне безригельного пере-крытия при различных схемах поперечного сечения опорной конструкции. Выполнен детальный анализ чис-ленными методами напряженно-деформированного состояния опорной зоны безригельного перекрытия. Рас-смотрены варианты моделей, сформированные как из пластинчатых, так и из объемных конечных элементов. Численными исследованиями установлены особенности формирования схемы деформирования приопорной зоны перекрытия. Получены схемы распределения нагрузок на контур опорной конструкции различного сече-ния. По результатам численного исследования установлено, что нормативная (традиционная) схема нагрузок на контур опоры соответствует сечению опорной конструкции, близкой к квадрату или прямоугольнику с соотно-шением сторон 1:2. Для вытянутых опорных контуров схема распределения нагрузок на контур опоры имеет существенные отличия от нормируемого. Установлено, что в торцевых зонах протяженных в плане опорных конструкций схема напряженно-деформированного состояния соответствует схеме НДС, формирующейся на квадратной (или близкой к квадрату) опорной конструкции. Разработаны предложения по учету особенностей НДС зоны опирания для расчета конструкции плиты по критерию продавливания.Ключевые слова: моделирование, численные методы, расчетная модель, напряженно-деформированное состояние, железобетонные конструкции, продавливание Abstract: Structural analysis of the formation and evolution processes of structural microdestruction with the transition to macrorestriction occurring during plastic deformation of masonry under biaxial stresses. The dependencies that determine the amount of the plastic phase of the deformation of masonry. Identified processes and their corresponding strength criteria, which play a key role in the implementation phase of plastic deformation. It is shown that plastic deformation of masonry under biaxial stresses occurs when the physical line operation of the basic materials of masonry (brick and mortar). Found that the plastic properties of masonry under biaxial stresses are determined by the processes occurring at the nodes of contact interaction of brick and mortar in horizontal and vertical joints. According to the results of numerical studies the values of the coefficients of ductility of masonry at different variants of mechanical characteristics of brick, mortar and adhesive strength of their interaction. ANALYSIS OF STRESS-STRAIN STATE OF REINFORCED CONCRETE PLATE AROUND SUPPORT ZONES

Introduction. The standards for earthquake-resistant construction have undergone three revisions over the past decade. Each new revision was accompanied by serious discussions. However, no fundamental changes were made to the planned level of seismic safety and methods of safety assurance. Today the scientific and technical level of these standards does not satisfy many specialists, that’s why the engineering community is considering the development of new generation standards. The overall purpose of the work is to focus the attention of specialists not so much on methodological issues of design, as on unresolved or underdeveloped issues. For some of them, solutions are presented that should be considered as the subject for discussion. Materials and methods. Analyses of the regulatory requirements for the means and methods of seismic protection, publications with proposed improvements, and a comparative analysis of regulatory documents of different countries were carried out. We also analyzed the experience of implementing regulatory requirements in software systems. Results. The importance of establishing a relationship between the limit states of structures and the categories of the technical state of facilities during and after seismic impacts was emphasized. The importance of formulating requirements for the analysis of buildings and structures, different levels of responsibility when checking their response to effects of earthquakes, having different recurrence, was also emphasized. We have formulated relevant recommendations that are offered as starting points of discussions. The need for more detailed regulation of the analysis in the time domain was highlighted. Problems were identified that need to be solved both with respect to the initial seismological information and with respect to draft strain diagrams describing the construction material. Considerations were provided on the set of requirements for the design of construction facilities according to the “building + base” pattern, boundary conditions for the considered part of the base and the recalculation of accelerograms in terms of their lower boundaries. Conclusions. Although the above considerations do not claim to be the final solution to these problems, they can serve as the basis for the development of a new generation of standards or as a material, which initiates relevant research and decision making.