3643

ISSN 2542-0526

RUSSIAN JOURNAL

OF BUILDING

CONSTRUCTION AND ARCHITECTURE

N 3 (43)

BUILDING STRUCTURES, BUILDINGS AND CONSTRUCTIONS

BASES AND FOUNDATIONS, UNDERGROUND STRUCTURES

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BUILDING MECHANICS

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ARCHITECTURE OF BUILDINGS AND STRUCTURES. CREATIVE CONCEPTIONS OF ARCHITECTURAL ACTIVITY

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Voronezh 2019

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Russian Journal

of Building Construction and Architecture

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BUILDING STRUCTURES,BUILDINGS AND CONSTRUCTIONS

DOI 10.25987/VSTU.2019.3.43.001

UDC 691.328.4

A. N. Nikolyukin1, V. P. Yartsev2, B. A. Bondarev3, A. O. Korneev4

MODELING THE COUPLING OF REINFORCEMENT IN CONCRETE

BASED ON AN ARTIFICIAL NEURAL NETWORK

Tambov State Technical University1, 2

Russia, Tambov

Lipetsk State Technical University3, 4

Russia, Lipetsk

1PhD student of the Dept. of Construction of Buildings and Structures, tel.: +7-953-717-16-44, e-mail: valax1@yandex.ru

2D. Sc. in Engineering, Prof. of the Dept. of Construction of Buildings and Structures, e-mail: kzis@nnn.tstu.ru 3D. Sc. in Engineering, Prof. of the Dept. of Construction Materials Science and Road Technologies

4PhD in Engineering, Assoc. Prof. of the Dept. of Construction Materials Science and Road Technologies

Statement of the problem. One of the major reasons for the loss of the bearing capacity of reinforced concrete structures is considered to be failure of coupling between the reinforcement and concrete. As a result, there is a need to study the change in the value of the coupling of the reinforcing bar and concrete under various influences. It should be noted that due to external and technological influences, the mechanical characteristics of concrete are subject to change, which directly affects the amount of adhesion.

Results and conclusions. Using artificial neural networks the analytical model was obtained that describes the final coupling strength by means of average tangential strains. Concrete of different strength types reinforced with metal and composite reinforcement is used for this study. Coupling was found to be associated with concrete characteristics and reinforcement type. A two-layer reverse neural network was also developed that describes coupling of reinforcement with concrete precisely.

Keywords: coupling, concrete, reinforcement, composite reinforcement, artificial neural networks, model.

Introduction. The major characteristics of evaluation of reinforcement coupling with concrete is tangential strain τсц. It is transformed in a conditional cylindrical surface at the reinforcement concrete interface. Conditional means that even if different types or reinforcement materials are used, their surfaces which are rough and protruding interact with each other. As

© Nikolyukin A. N., Yartsev V. P., Bondarev B. A., Korneev A. O., 2019

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a result, there are strains directed to the surface at some angle. According to R. G. Litvinova, P. P. Nazarenko and G. Rehm, this is a contact task [3, 16]. Conditional tangential strain is a simplified characteristics of the reinforcement concrete adhesion. It does not seem contradictory as generalized theories yielding practical results are allowed for.

V. I. Zhukov, P. P. Nazarenko, M. M. Kholmyanskiy, S. D. Santiago, etc. argued that strain that is normal to the longitudinal reinforcement axis is transverse reinforcement pressure on concrete or thrust that is associated with tangential coupling [6, 16].

As more experimental data were accumulated and new types of reinforcement were designed, a new idea of reinforcement concrete coupling came about. Tangential coupling for wire and smooth slab reinforcement is due to coupling of cement gel with reinforcement and shrinkage pressure friction. There has been a growing interest towards coupling due to the emergence of periodic reinforcement [7]. Besides, it was found that gripping forces generate significant friction on the contact surface. The emergence of twisted and spinned reinforcement causes a material and concrete to interact in particular ways [2]. Tangential adhesive strains and area lengths were obtained as a result of measuring normal strains in reinforcement.

As a result of the studies by A. A. Oatul it was found that coupling is characterized with mutual shift of reinforcement in relation to concrete [4]. Besides, T. I. Astrov identified the dependence of g on the axial strains σ-g on the reinforcement. In the meantime А. I. Semenov and G. Rehm were able to find the dependence of relative deformations of rope reinforcement and concrete on the contact surface on the section under discussion [16].

Using a microscope, G. N. Sudakov conducted an experiment in order to identify mutual shifts by observing shifts of special references fixed on concrete and reinforcement [5]. Throughout the loading the reinforcement was observed using special holes located at a certain step in the concrete along the reinforcement. However, later on G. N. Sudakov discovered the methods of optically sensitive pavings that allowed shifts and deformations to be identified only on the surface of the samples [5]. V. G. Diatovskiy, S. A. Madatyan, А. А. Оаtul, etc. excluded failure of reinforcement-concrete contacts [1, 4].

Currently a lot of authors are of the opinion that numerical modeling is the most efficient method of studying coupling of materials.

Along with a wide range of methods of studying adhesion, a phenomenological approach to mathematical analysis of experimental results based on a series of simplifying prerequisites proved to be popular. It has also become possible to conduct in-depth studies of con- crete-reinforcement interaction. Interaction of materials is presently viewed in the context of numerical methods [4, 5].

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Russian Journal of Building Construction and Architecture

P. P. Nazarenko found [3] that the behavior of coupling of reinforcement with concrete under long-term dynamic and cyclic interactions as well as short-term loads can remain unchanged. However, no particular attention has been paid to coupling under significant loads. Besides, use of phenomenological laws of coupling is limited as they only apply to a certain reinforcement type. V. G. Kolbasin, S. A. Madatyan, T. D. Tuleev and N. N. Surikov believed that a change in the profile of a bar reinforcement has a significant influence on the coupling of bars with it as there are also changes in the character of the profile and surface on the reinforcement [1].

Up to date, there has been no comprehensive theory regarding coupling of reinforcement and concrete. Therefore it is of importance to develop relevant theories of interaction of materials to account for a whole range of factors.

Therefore this study looks at an analytical model designed using artificial neural networks NN for predicting a strength limit of the coupling τсц of ferroconcrete. For that purpose, experiments were conducted to test pulling of bars out of concrete prisms. The dataset obtained experimentally by means of independent variables employed for developing a predicting model NN included strength characteristics of concrete (stretching, compression, elasticity modulus), anchorage depth, diameter of the reinforcement, freezing and thawing cycles of the samples, profile and material of the reinforcement bar (metal and composite reinforcement was used). A statistical analysis of the efficiency of the model while predicting a maximum tangential strain was conducted.

1. Description of the experimental dataset. The data of the 20 obtained samples was used in the experiments [8]. The examples of the used data from each sample are presented in Table 1.

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Note: E is the elasticity modulus of concrete, GPа; Rprism is the prismatic strength of concrete, МPа; Rstretching is the designed stretching resistance of concrete, МPа.

The pulling studies were conducted in accordance with the GOST (ГОСТ) 31938-2012 (Fig. 1).

Tested joint box

Supporting plate

Polyvinyl chloride pipe

Fig. 1. Samples and scheme of the pulling tests

The prism samples reinforced in the centre with a square section 10 × 10 сm and a lengthdepth ratio of the anchorage l/d = 5 were employed. Bars with the diameter of 10 mm were

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