Andrii Bambura, Olena Dorogova
Common method of valuation of strain-stress state of bearing resistance of prestressed concrete elements of round cross-section through strain model
State Enterprise «State Research Institute of Building Constructions»
Abstract. Purpose, tasks and actuality of research deals with assessment of stress-strain state and bearing capacity of the usual and pre-stressed reinforced-concrete elements with round section are presented there. The basic premises and assumptions for deformation model of concrete are stated there. The engineer method for designing of stress-strain state and bearing capacity of elements with round section are proposed on basis of these premises and assumptions. In accordance with accepted assumptions, the averaged section corresponding to average concrete and reinforcement deformations along block length between cracks (if they have place, but not the section with crack) is accepted as design value when elaboration of calculation apparatus. In the process, the hypothesis of plat sections is considering as truth for design section. The correlation between stresses and deformations of compressed concrete is accepted as curvilinear diagram in accordance with equation 3.14 EN 1992-1-1; the deformations of usual reinforcement or increment of deformations in pre-stressed reinforcement are equal to deformations of surrounding concrete. The limit values εсul of fiberdeformations of compressed concrete or rupture of all strained reinforcement rods or loss of bearing capacity of design section due to loss of stability of deformation or loss of equilibrium between internal and external forces are accepted as criterion of bearing capacity loss by design section. Numerical integration (in quadrature) of the non-linear equations set of equilibrium is carrying out there. In process, the compresses area of reinforced concrete element with round section is dividing by m layers perpendicular to axis of moment action. The solution of the gotten non-linear equations sets is carrying out by matching on parameters of deformed state εс(1) and ℵ (or εс(2)) in accordance with deformation methodology. Comparison of the results of the reinforced concrete round sections elements bearing capacity determination (when diving of compressed by m = 40 layers) gotten on «exact» method (direct integration of equilibrium equations) with calculation results on engineer method has shown following: the maximal calculation error does not exceed 1 %. It is acceptable from point of practice.
Keywords: bearing capacity, stress-strain state, round section, equilibrium equation, solution error.
Anatoliy Yugov, Andrii Tymoshko
Classification of buildings on height
Donbas National Academy of Civil Engineering and Architecture
Abstract. The article analyzes the current state of the question of classification of buildings on height in different countries, particularly in Russia, Belarus and Ukraine. According to the results of this analysis, at this moment in most countries there is no consensus about the division of buildings into classes according to their height. The only existing in Ukraine classification of buildings by conditional height, which is contained in DBN V.1.1-7-2002, is presented in this paper. Disadvantages of this classification have been identified and new classification of buildings by conditional height, which is based on the features of structural and space-planning solutions of buildings with different heights and fully oriented on the Ukrainian normative documents, is proposed. Complete substantiation of adopted in the new classification criteria of division and comparison of proposed classification with the existing have been represented in this paper also.
Keywords: classification, building, conditional height, criterion of division, structural solution.
Mixail Pakter, Valery Bratchun, Aleksandr Stukalov, Vitaly Bespalov, Anatoliy Dolya
Laws of technology obsolescence oil road bitumen and asphalt mixes
Donbas National Academy of Civil Engineering and Architecture
Abstract. Using rheological and standard methods, as well as infrared spectroscopy studied phenomena and processes in the oil road bitumen and asphalt concrete with technology obsolescence in the production of asphalt mixes. It was found that the thermal oxidative aging of oil road bitumen is the free radical mechanism and the development of processes that lead to a decrease in oil content in bitumen and increase the concentration of asphaltenes, which manifests itself in reducing the penetration, softening temperature increase, increase in the effective molecular weight of the polymer component of the bitumen to lower relaxation and a deformation capacity, and the loss of adhesion-cohesive properties of the organic binder. Calculate the average speed of the accession process of atmospheric oxygen and the mass loss of petroleum bitumen in the thermal oxidative aging. Isolated by adsorption chromatography fractions of oils and petroleum fraction-benzene resins were studied by infrared spectroscopy, IR-on device 75 in the area of 3 600–700 cm–1 by the liquid film. Found that the bitumen has a film thickness of the surface layer of 0,47 mm in which there is a thermal oxidation process and underneath a bottom layer, which occur only in heat aging processes. Similar patterns of thermal oxidative aging revealed in the «lime mineral powder – oil road bitumen». It is shown that the effect of temperature in the production of asphalt mixes 3,5–5,0 times higher than during preparation of mixtures on the intensity of their aging.
Keywords: oil road bitumen, bituminous mixture, road asphalt, bitumen and aging process of asphalt concrete.
Oleksand Petrakov, Viktor Yarkin, Kateryna Bryzhata
The influence of ground design models on stain-stress distribution of bearing structures on frame constructions with slab foundation
Donbas National Academy of Civil Engineering and Architecture
Abstract. Ground design models significantly affect on the strain-stress distributions of foundations and superstructures, however, technical and regulatory literature degree of impact of this influence is not enough. The paper consider the basic ground design models, impact of the quantitative characteristics of ground design models for internal force in base slabs and bearing structures of frame buildings on slab foundation, and also quoted result of theoretical investigation on the basis of professional software package Lira. In the paper considered the following ground design models: 1) model, which is characterized by constant stiffness, 2) model, which is characterized by a variable stiffness, 3) model, which is characterized by generalized stiffness of professor Klepikov. In these models were compared: the value of vertical forces in the columns, the values of displacements along the axis Z, the bending moments in a plate foundation, and was giving a comparison of the results and recommendations of the selection of ground design model.
Keywords: ground design model, the Winkler model, the model of generalized stiffness professor Klepikova, linearly deformed half-space model.