Stress-strain State Of Structures Research Articles

Justification of the estimation technique for the technical condition of the tank with inadmissible imperfections in the wall shape

The paper has its focus on the problem of estimating the stress-strain state of the vertical steel tanks with the inadmissible geometric imperfections in the wall shape. In the paper, the authors refer to an actual tank to demonstrate that the use of certain design schemes can lead to the raw errors and, accordingly, to the unreliable results. Obviously, these design schemes cannot be based on when choosing the real repair technologies. For that reason, authors performed the calculations of the tank removed out of service for the repair, basing on the developed finite-element model of the VST-5000 tank with a conical roof. The proposed approach was developed for the analysis of the SSS (stress-strain state) of a tank having geometric imperfections of the wall shape. Based on the work results, the following was proposed: to amend the Annex A methodology “Method for calculating the stress-strain state of the tank wall during repair by lifting the tank and replacing the wall metal structures” by inserting the requirement to compulsory consider the actual stiffness of the VST entire structure and its roof when calculating the structure stress-strain state.

EXPERIMENTAL STUDY OF THE NATURE OF INTERACTION OF STEEL FIBRES EQUIDIRECTIONALLY LOCATED IN PARALLEL TO FORCE IN FINE-GRAINED SLAG CONCRETE

At present, the use of modern technologies is becoming more urgent. This concerns both construction engineering and structural design standards. There is a need for a wider use of computer technology, which will allow solving multifactorial tasks taking into account actual stress-strain state of structures at all the stages of their operation with the help of a nonlinear deformation model in the future. The objective of this work is to study the nature of the interaction of steel fibers equidirectionally located in parallel to force in fine-grained slag concrete, in particular, to determine the coefficient characterizing the change in the contribution to the work of the fibre reinforcement unit depending on the length of the adjacent fibers embedment in the slag concrete and the quality of adhesion between them, and construction of a graphical model of steel fibers operation in cinderblock matrix, diagrams of deformation (state) of concrete, reinforcement and fiberы which are an integral characteristic of physical and mechanical properties of materials. Tests for the extraction of steel fibers with single offset bends at the ends of fine-grained slag concrete have been carried out. Experimental dependences of steel fibers displacement on the applied load have been obtained. Based on the results of the experimental data analysis, formulas for determining the coordinates of piecewise-linear ‘load-displacement’ diagrams are proposed; they describe the displacement of a single fiber from fine-grained slag-concrete, which allows drawing conclusions concerning their mutual influence on the anchoring ability in fine-grained slag concrete. Dependencies for determining the coefficient characterizing the change in the contribution to the work of the fibre reinforcement unit depending on the length of the adjacent fibers embedment in the slag concrete and the quality of adhesion between these fibers and the slag concrete-matrix are proposed. The work also presents common dependencies, which can be used to construct analytical piece-wise diagrams ‘load-displacement’ and describe the work of fiber embedded in fine-grained slag concrete when calculating the units of building structures from steel-fiber-slag-concrete by means of a computer using the diagram technique.

Influence Evaluation of Buildings Constructed in Protected Zone on St.Petersburg Subway Underground Structures Stress-strain State

Building in protected zones of subway can seriously influence on stress-strain state and operational reliability of underground structures. It should be noted that till nowadays there are no normative documents which regulate the permissible additional load on various types of underground subway constructions, the grade of acceptable approaching of the foundations and piles elements and common attitude to protected area dimensions of different underground constructions and other important factors.There is practical need in developing of criterion of permissibility evaluation of ground construction in the St. Petersburg subway protected zone. The criterion depends on various factors: type of underground structures, geotechnical conditions, the current technical state of underground constructions, the allowed value of additional loads on them and other important factors.The article presents the algorithm for the influence evaluation of ground construction on underground structures as well as the example of its practical realization during developing the design solutions and during construction. There are examples of realization of proposed methodology for influence evaluation of ground construction on various St. Petersburg metro underground constructions.

CHANGE IN DEFORMATION PROPERTIES MODELING OF CONCRETE IN PROTECTIVE STRUCTURES OF NUCLEAR REACTOR BY IONIZING RADIATION

The necessity of studying the effect impact of elementary particles impact on the strength and deformation materials properties used in protective constructions nuclear reactors and reactor technology has been stipulated. A nuclear reactor pressure vessel from prestressed concrete, combining the functions of biological protection is to be considered. The neutron flux problem distribution in the pressure vessel of a nuclear reactor has been solved. The solution is made in axisymmetric with the finite element method using a flat triangular finite element. Computing has been conducted in Matlab package. The comparison with the results has been obtained using the finite difference method, as well as the graphs of changes under the influence of radiation exposure and the elastic modulus of concrete radiation deformations have been constructed. The proposed method allows to simulate changes in the deformation properties of concrete under the influence of neutron irradiation. Results of the study can be used in the calculation of stress-strain state of structures, taking into account indirect heterogeneity caused by the physical fields influence.

Problems of the reliability and durability of dynamically loaded structures from physically nonlinear material

One aspect of the problem of providing safety assurance when designing structures for the implementation of technical applications of high-energy matter states related to the durable functioning of loaded components is considered. The regularities of the stress-strain state of structures made from a material with nonlinear properties exposed to a mobile heat source are examined. It is demonstrated that the plastic deformation is intensified when the amplitude of the temperature variations increases insignificantly, leading to a durability loss in the structure, according to the fracture criterion, of an order of magnitude.

Analysis of drop tests of an experimental sample of TUK-84

The calculations of the stress-strain state of the structure of TUK-84 and its drop test for mechanical damage, performed on the SM-E322 KBSM stand, are analyzed. It is shown that the results agree well with one another. Conclusions are drawn concerning the preservation of strength and functionality of TUK-84 after being subjected to mechanical loads under conditions of an accident situation, and recommendations are made concerning the order in which calculations of rolled structures should be performed. A computational model making it possible to analyze the stress-strain state of roll structures with various modifications of TUK-84 without the need of repeating expensive tests for accident conditions during shipment is developed on the basis of the test results.

Consideration of friction between layers in determining the stress-strain state of structures with nonideal layer contact

A mathematical model for calculation of structures in a three-dimensional installation allowing for layer slippage with friction was constructed. The examples examined show that consideration of friction in problems of calculating laminated structures with nonideal layer contact can introduce an essential correction in the stress—strain state of the structure. In slabs with a freely sagging lower surface, friction is perceived for important friction coefficients and increases when the slippage surface approaches the loaded surface. In masses with a rigidly attached lower surface, even insignificant friction coefficients lead to essential redistribution of the stress—strain state.

ESTIMATION METHOD AND EXPERIMENTAL INVESTIGATION OF STRESS-STRAIN STATE FOR TENSILE RC INCLUDING ASSESSMENT OF SHRINKAGE AND NON-LINEAR STRAINS

In this paper, a stress-strain state is analysed for hardening reinforced concrete due shrinkage, increase of physical parameters and non-linear strains of concrete. A method has been developed for assessment of initial stress-strain for reinforced concrete specimens subjected to short-term loading. Stresses and strains in reinforcement and concrete are estimated by experimental-theoretical method and σ—ε diagram for tensile concrete including the descending branch is defined. Experimental investigations of tensile reinforced and non-reinforced members have been carried out for defining the descending part of σ—ε diagram. Sufficient agreement of experimental and predicted data have been achieved. The method and results of these investigations have been applied for design and building of water cleaning equipment made from cast-in-situ and pre-cast concrete. Stress-strain state of structures has been determined for different stages of construction and each of them the required technology has been chosen. Careful examination of structures of the buildings built allows to conclude that the above method can used for calculation and design of cast-in-situ and pre-cast reinforced concrete structures.

ESTIMATION METHOD AND EXPERIMENTAL INVESTIGATION OF STRESS-STRAIN STATE FOR TENSILE RC INCLUDING ASSESSMENT OF SHRINKAGE AND NON-LINEAR STRAINS

Summary In this paper, a stress-strain state is analysed for hardening reinforced concrete due shrinkage, increase of physical parameters and non-linear strains of concrete. A method has been developed for assessment of initial stress-strain for reinforced concrete specimens subjected to short-term loading. Stresses and strains in reinforcement and concrete are estimated by experimental-theoretical method and σ—e diagram for tensile concrete including the descending branch is defined. Experimental investigations of tensile reinforced and non-reinforced members have been carried out for defining the descending part of σ—e diagram. Sufficient agreement of experimental and predicted data have been achieved. The method and results of these investigations have been applied for design and building of water cleaning equipment made from cast-in-situ and pre-cast concrete. Stress-strain state of structures has been determined for different stages of construction and each of them the required technology has been ch...

Stress-strain state of structures with local surface cylindrical damage

Stress-strain state of structures with local surface cylindrical damage

Examination of the stress-strain state of structures made of carbon-reinforced plastic by the polarization-optical method

Examination of the stress-strain state of structures made of carbon-reinforced plastic by the polarization-optical method

Results of observing the state of hydraulic structures of the moscow canal

The 40-yr operating experience with the hydraulic structures of the Moscow Canal revealed various aspects which must be taken into account in the design, construction, and operation of similar hydraulic structures. The defects due to forces that were noted on the structures indicate the need to conduct detailed investigations of them and to set up longterm observations of the stress-strain state of structures on a broader scale.