Key Engineering Materials Vol. 887

Abstract: Elaboration analytical and computer modeling, changing dynamic parameters of short-term and long-term loaded nonlinearly deformable large-span spatial shell structures are investigated in this research paper. The proposed physical and geometrically nonlinear models of deformation and computational algorithms for solving dynamic problems are applied to assess the stress-strain state of smooth and ribbed spatial systems with variable stiffness caused by the accumulation of damage and the orthotropic structure reinforced by the ribs of the structures of the studied systems. The possibility of using the proposed method of accounting for variable dynamic stiffnesses in calculations for solving problems of dynamic strength and stability of spatial large-span shells of complex geometry is shown.

Abstract: The paper presents the governing equations of bending of nonlinearly deformable, axisymmetrically loaded round, thin reinforced concrete and steel concrete slabs, taking into account the work of a non-deformable and pliable support contour. Based on the results of theoretical and experimental studies, the stress-strain state of reinforced concrete and steel-concrete slabs under short-term and long-term loadings was estimated. The nature of stress state is revealed in the stages of cracking and destruction of plates. The work of the slabs in the field of elastic, elastoplastic and plastic stages of work is estimated. Using the method of limiting equilibrium, a method for calculating steel-concrete slabs for strength with normalized parameters.

Abstract: The paper presents the results of the study of the stress-strain state of polygonal shells of positive and negative curvature with different geometric shape of the plan, taking into account the influence of the prehistory of a high loading level. To derive the resolving equation, equation, a mixed-type equation of the moment theory of shells was used. The calculation of the investigated out according to the moment theory, taking into account the influence of a complex stress state edge effect. The numerical implementation of this solution is carried out in relation to hinged and restrained shells. The bearing capacity of short-term and long-term loaded reinforced concrete polygonal shells was investigated by the method of limiting equilibrium.

Abstract: The dynamic parameters of long-span prestressed one and two-belt hanging roofs, for which the seismic wavelengths are commensurate with the dimensions of the structure in plan, are considered. Calculated expressions have been obtained to determine the dynamic parameters for symmetric and skew-symmetric oscillations depending on the length of seismic waves.To ensure the operational safety of unique buildings and structures, we studied the change in the structural properties of materials from unfavorable operating conditions, long-term, beyond design-basis static loads, high-intensity dynamic effects, compliance of the support contours and the possibility of local damage and from the failure of cables of the structures under study.

Abstract: Contact problem for viscoelastic aging pipe with a longitudinally nonuniform thin elastic internal coating and a rigid cylindrical insert is considered in the paper. The basic integral equation with integral operators of different types (mixed integral equation) is given. It's analytical solution for contact stresses in insert area is presented. The solution is constructed in such a way that the function describing the inner coating nonuniformity is distinguished by a separate factor. This fact allows one to perform accurate calculations even in cases where the coating properties are described by rapidly changing and even discontinuous functions. Other known analytical methods do not allow one achieving such a results.

Abstract: The problem of use of hi-tech macroporous concrete in load-carrying structures of low-rise buildings is designated and the forthcoming research problems of power resistance and deformation of the compressed and bent elements from foam concrete of natural solidification are formulated. Results of pilot researches of intense state of strain of the compressed and bent elements from foam concrete of average density of 1200-1600 kg/m³ of different structural modification in the conditions of short-term and long action of loading are provided. It is established that foam concrete meet for nonrigid indicators regulatory requirements and take the intermediate place between full-strength cellular and light concrete on expanded aggregates that creates premises for their successful application in the bearing concrete and reinforced concrete constructions. Deformation and strength characteristics of foam concrete of different structural modifications taking into account the impact of the long processes caused by solidification of concrete and external power factors, necessary for calculation and structural design are offered. The received results of researches will allow to project rationally bearing and enclosing structures from foam concrete that leads to increase in technological level of monolithic construction.

Abstract: This paper presents the study results of the nonlinear stress-strain diagrams of concrete based on the local materials of Central Yakutia. The results of comparing the obtained data with the requirements of normative documents of the Russian Federation, European countries, India and China are presented. The calculation results for bending bearing elements with concrete nonlinear deformation taken into account obtained using the Ansys software are given. The reliability of the calculated data was verified using the proposed diagrams, using the example of the results of a survey of characteristic failures of bending concrete and reinforced concrete elements in the Republic of Sakha (Yakutia).