Applied Mechanics and Materials Vols. 725-726

Abstract: Concrete pavements and airfields in the curing process of protection against desiccation, particularly, the application of the wax-polymer emulsion which forms a solid film, which persists for a long time in the initial period of operation of roads and airfields. The presence of the film changes the nature of the friction on the surface that could adversely affect traffic and aircraft. This paper investigates the friction of rubber on the surface of the treated concrete with an aqueous emulsion of paraffin series Emcoril. It was established that the friction on the paraffin film, unlike friction on the surface of the concrete does not respect the law of linear Coulomb. The degree of deviation from linearity, the higher the greater the thickness of the film. The frictional force on the film increases with the slip velocity. At high speed, friction in the film is greater than the frictional force on the concrete, and at low speed is much lower than the previous one

Abstract: Standardization and unification of elements, constructions and design solutions is one of the main ways to reduce the complexity and cost of the construction.Standard designs of truss coatings with a 10% slope for 24, 30, 36 meters spans were developed in this article for different load combinations.Stress calculation and truss elements dimensioning was made with the SCAD Office software complex. Then the relationship between the thickness of the section, span and load was defined, and the limits of various sizes of the accepted bottom chord connecting block.Designed series of truss structures with a 10% slope and 24, 30, 36 meters spans covers a range of line loads from 1,3 t/m to 3.3 t/m. In comparison with the truss structures series Molodechno it has a lower metal consumption by reducing the cross section of the upper chords due to vertical elements adding. Transportation of a 12-meter section falls under the category of oversized transportation.

Abstract: It is proposed a computational model of spatial formation of cracks in reinforced concrete constructions under the action of torsion with bending, based on working assumptions and constructed equations. The physical interpretation of the solution is that it allows to search for generalized minimum load, which corresponds to the formation of the first crack and the spatial coordinates of the point of its formation.

Abstract: Application of dynamic method for conservative system stability analysis is considered. It is shown that the use of this method may cause essential errors. A detailed analysis of error causes is given. A number of models is considered, at which stability analysis, errors occur. Threat evaluation of such errors is given. It is shown that the physical nature of probable errors is in that in degenerated dynamic system these forms of stability loss correspond to the original system from which all dynamic degrees of freedom are excluded. Recommendations which allow excluding probable errors are given. Method which may be called degenerated system dynamic method is proposed. This method is especially effective at time dynamic analysis of linear degenerated system subjected to short-term loads.

Abstract: The delta-functions are used in calculation of the building structures to determine irregularity places, but the delta-function proper is a limiting function featuring no geometrical interpretation. In order to justify correctness of its application, it is necessary to carry out the limiting transition based on the method of variation limiting transformations. Consideration is given to the shallow shells supported by the narrow ribs or featuring jogs of the middle surface. The places of discrete variation of shell thickness or its curvature will be set by means of singular columnar functions. The limiting transition from such functions to delta-functions is used to obtain correlations for the rib shells and the shells featuring the middle surface. This is the way to justify a possibility of using delta-functions in the theory of shells featuring irregularities. At that, the equilibrium equations get simplified and, at the same time, the calculation accuracy gets lost.

Abstract: Actuality of study of the problem of longitudinal crack formation along reinforcement taking into account concrete nonlinear strain is pointed out in this article. It is known that at collaboration of steel and concrete plastic strains occur in concrete surrounding bar. Previously, in the work [6], solution on determination of splitting cracks at elastic work of concrete in the area of active bond to steel was proposed. In this article, theoretical solution on determination of longitudinal cracks both in supporting area and in the area of collaboration of steel and concrete between cracks along element is suggested. For establishing equations taking into account inelastic work of concrete, the theory of plastic properties suggested by G.A. Geniev was used. Component stress-strain relation is recorded by analogy with studies performed by G.A. Geniev and N.N. Malinin. At that, design dependencies are linked with normative factors of concrete, such as concrete ultimate tensile strength, Poisson ratio and concrete elastic strain ratio at stretching. All this allowed to significantly simplify the use of expressions offered.

Abstract: 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

Abstract: The quadrilateral finite element for analysis of thin-walled reinforced concrete structures with complex geometrical shapes is suggested for implementation in engineering software. The behavior of concrete and reinforcement is described with relations of the deformation theory of plasticity, formulated in terms of residual strains, which allows passing from unloading to active loading for stress – strain diagram with opposite sign. The compatibility of deformations of concrete and reinforcement is assumed. Reinforcement of each direction is presented as a separate layer, subjected to tension - compression in the direction of rod axes. The Mindlin-Reissner shell theory as well as the mixed interpolation of shear strain components is used.

Abstract: For elastic frames authors offer a method of solving the tasks of optimal control of the stress state, when the boundary loads are the controlling parameters. In difference from other papers it is offered to use deformation energy as a merit functional. This functional estimates the deviation between two functions: optimal function and given function. Examples of the solution are given.

Abstract: This article considers the convergence of the foundation slab finite element model. Slab works in conjunction with the subgrade. In PC Cross Scad authors conducted joint calculation of the foundation slab and ground, based on the use of an iterative algorithm.Analytical research of convergence of the calculations results allowed to select optimum partitioning step of the model. Conclusions are drawn on rationality of calculations of the foundation slab on the bilinear subgrade realized in PC Cross Scad.