scholarly journals Reinforcement impact on the stress-deformation state of concrete faced rockfill dam

Vestnik MGSU ◽  
2019 ◽  
pp. 347-355 ◽  
Author(s):  
Mikhail P. Sainov ◽  
Andrei Y. Shigarov ◽  
Sofia A. Iasafova
Keyword(s):  
Reinforced Concrete ◽  
Steel Reinforcement ◽  
Control Element ◽  
Tensile Stresses ◽  
Rockfill Dam ◽  
Reinforcement Percentage ◽  
Deformation State ◽  
Stress Deformation ◽  
The Face ◽  
Concrete Face

ABSTRACT Introduction. The article considers results of research of reinforced-concrete face stress-deformation state depending on availability of the reinforcement. At some ultra-high reinforced-concrete faced rockfill dams (CFRD) the transversal (horizontal) cracks were developed in the seepage-control element. It is supposed that the cause of the crack formation is high values of tensile stresses. In this connection, opinions are expressed about the necessity of strengthening the face reinforcement. However, in accordance with the experience gained, in real dams the reinforcement, as a rule, is arranged in one row with reinforcement percentage 0.35 to 0.5 %. The urgent issue of CFRD studies is assessment of impact of the concrete face strengthened reinforcement on enhancement of its reliability. Materials and methods. The studies were conducted for different variants of rock fill deformation properties on the example of 100 m high rockfill dam. The reinforced concrete face was adopted to be wide (1 m thick). The reinforcement was adopted to be two-row one, with reinforcement percentage of 1.5 %. The study was conducted using the finite element method. The reinforcement was simulated using bar finite elements. Results. To reveal the role of reinforcement, analyses of the stress-deformation state were conducted for two cases. In one case it was assumed that reinforcement is absent and in the other case consideration was made for the face with steel reinforcement. Stresses in concrete and steel reinforcement were analysed. Stresses acting along the upstream slope were considered. Conclusions. It was revealed that due to the reinforcement of steel-bar reinforced concrete face it was impossible to provide decrease of tensile stresses in the face concrete down to the permissible level. Reinforcement may play a significant role in the face stress-deformation state only at the moment of forming transversal cracks in the face concrete, but such a case is inadmissible.

scholarly journals Impact of rockfill dam structure heterogeneity on reinforced concrete face stress-strain state

2019 ◽  
pp. 5-5 ◽  
Author(s):  
Mikhail Sainov ◽  
Igor Egorov ◽  
Konstantin Pak
Keyword(s):  
Reinforced Concrete ◽  
Strain State ◽  
Longitudinal Force ◽  
Heterogeneous Structure ◽  
Stress Strain ◽  
Stress Strain State ◽  
Rockfill Dam ◽  
Deformation Properties ◽  
The Face ◽  
Concrete Face

Introduction. One of the main principles in designing modern ultra-high rockfill dams with reinforced concrete face is the principle of zoning rockfill of various quality in the dam body. It envisages that rockfill in the shell upper part should be compacted very carefully in order to minimize to the maximum the deflections of the reinforced concrete face. In the shell lower part it is allowed placing heterogeneous rockfill with less degree of compaction. Analysis of the results of field observations over settlements of the already constructed dams shows that this pattern of zoning may lead to considerable irregularity in distribution of rockfill deformation moduli between the upstream and the downstream parts of the dam. Numerical modeling of the existing Aguamilpa dam carried out by use arlier showed that this effect may be caused by unfavorable stress-strain state of the reinforced concrete face threatening with crack formation. Were come ended using dams of homogenous structure. However, this conclusion caused doubts of some experts. More detailed studies who see results are described in this article were conducted in order to confirm or disprove this conclusion. Materials and methods. The studies were conducted by finite element method on the example of 100 m high rockfill dam. Different alternatives of rockfill deformation properties in the shell upstream and downstream parts were considered. Results. Analysis of the results of studies confirmed the conclusions made earlier about the features of the rockfill dam reinforced concrete face stress-strain state. It was revealed that increase of rockfill deformation in the dam shell downstream part leads to appearance of additional tensile longitudinal force in the face. It increases the risk of appearance of through transversal cracks in the face. However, the heterogeneous structure of the dam shell may not have a decisive impact on stress values because the value of bending moment plays a great role. Conclusions. The results of the fulfilled study as well as modern dam construction practice show the necessity of modifying the traditional pattern of rockfill zoning in the dam body. It is necessary to provide decrease of differences in rockfill deformation of the upstream and downstream parts of the dam.

scholarly journals Stress-deformation state of compound reinforced concrete bars with high-strength reinforcement prone to long-term compression

Vestnik MGSU ◽  
2019 ◽  
pp. 1121-1131
Author(s):  
Kristina I. Zarakovskaya ◽  
Vladimir F. Zakharov
Keyword(s):  
Reinforced Concrete ◽  
Stress State ◽  
Calculation Method ◽  
High Strength ◽  
Longitudinal Reinforcement ◽  
Deformation State ◽  
Stress Deformation ◽  
Strain Stress ◽  
Compound Section

Introduction. Considering that reinforced concrete is the most common material in construction and reconstruction of buildings and facilities, research of work of high-strength reinforcement in reinforced concrete elements, including compressed columns, are still relevant at present. Analysis of compound-section columns with high-strength longitudinal reinforcement is of particular interest since the method of sectional build-up is widespread enough in the reconstruction of buildings and facilities. However, no information on the work of this kind of reinforced concrete structures under long-term compression was found either in foreign or domestic literature; this fact provides relevance and academic novelty of the study. Materials and methods. The article provides the research of parameters of the strain-stress state of compound reinforced concrete bars with high-tensile reinforcement under long time compression employing the modern methods of mathematical simulation. Results. The developed calculation method allows determining additional parameters of the strain-stress state of the compressed compound-section reinforced concrete bars considering the concrete creep deformations forming in time of the long-term compression. When comparing the analytical study results with authors’ experimental data and previous results of other researchers, an adequate degree of reliability of the developed calculation method was confirmed. Conclusions. When applying the developed calculation method of stress-deformation state parameters for the compressed compound-section columns with high-strength longitudinal reinforcement, the study discovered that significant effort redistribution from concrete to high-strength reinforcement occurs under long-term compression. This fact was confirmed with the results of an experimental investigation on the resistance of the compound reinforced concrete bars with high-tensile reinforcement to the longtime compression.

scholarly journals An XFEM-Based Analysis of Concrete Face Cracking in Rockfill Dams

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Binpeng Zhou ◽  
Junrui Chai ◽  
Jing Wang ◽  
Heng Zhou ◽  
Lifeng Wen
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Numerical Model ◽  
Crack Initiation ◽  
Rockfill Dam ◽  
Initiation And Propagation ◽  
The Face ◽  
Stress And Deformation ◽  
Concrete Face ◽  
Element Method

The concrete face of a rockfill dam is a long and thin slab structure, which is highly susceptible to fracture when subjected to the settlement of the dam. The study of the generation and propagation of cracks in the concrete face of rockfill dams is of great significance to dam construction and face crack prevention. In this study, the initiation and propagation of cracks in the concrete face of a rockfill dam are investigated using an extended finite element method (XFEM) and ABAQUS software for the Gongboxia concrete-face rockfill dam. A numerical model for this dam is established using a finite element method, and the face stress and deformation distributions are obtained. Based on the results, a numerical model is built to find the location where cracks are initiated in the face. The displacement of the entire model is treated as the equivalent displacement for the numerical model. XFEM is utilized throughout the modeling process to obtain the stress concentration, crack initiation, and crack propagation in the concrete face, and an analysis of crack initiation and propagation is conducted. Finally, the effects of the thickness of concrete covers and reinforcement layers on the stress intensity of crack tips are also discussed using the established numerical model, and techniques for controlling the fracturing of the concrete face have been proposed in this paper.

Simulative Analysis for Reinforced Concrete Face Rockfill Dam of Qianqiao Reservoir

2011 ◽  
Vol 295-297 ◽  
pp. 2413-2416
Author(s):  
Dong Yu Ji ◽  
Wen Liang Ma
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Construction Process ◽  
Operational Process ◽  
Rockfill Dam ◽  
Concrete Face ◽  
Concrete Face Rockfill Dam

In this paper, finite element simulative analysis is proceeded for reinforced concrete face rockfill dam of Qianqiao reservoir. Deducing variation law of the dam’s stress and displacement in construction process and operational process. The analytic results are shown：reinforced concrete face rockfill dam of Qianqiao reservoir is reasonable structure, and every index meets the requirements for design.

scholarly journals IMPACT OF DAM ROCKFILL CREEP ON REINFORCED CONCRETE FACE STRESS-STRAIN STATE

2019 ◽  
Author(s):  
Mikhail P. Sainov ◽  
Andrey Yu. Kirichenko
Keyword(s):  
Reinforced Concrete ◽  
Rheological Model ◽  
Strain State ◽  
Time Dependent ◽  
Favorable Effect ◽  
Stress Strain ◽  
Stress Strain State ◽  
Operation Period ◽  
The Face ◽  
Concrete Face

Introduction. Rockfill deformations are developed during long time. It is known that most intensive they are during construction period, but their increment continues also during operation period due to creep. Therefore, creep may affect the reinforced concrete face stress-strain state. Nevertheless, search for the scientific and technical information showed that the problem of creep impact on the face strength is poorly studied. Materials and methods. Studies of stress-strain state were conducted with the aid of numerical modeling by finite element method. They were carried out on the example of in-situ Toulnustouc dam, which deformations during the operation period are known by the results of field measurements. For simulation of the time-dependent dam, deformation increment process there was chosen a rheological model of soil and a technique was worked out for calculating the dam stress-strain state. At plotting the rheological model, the use was made of the simplest exponential relationship of time-dependent deformations. Results. The parameters of the rockfill model were determined by selection from condition of matching between the dam design displacements and the field data. For the considered dam, the rockfill creep has not resulted in cardinal changes in the reinforced concrete face stress-strain state. Conclusion. It was revealed that increase of the dam settlements due to creep has a favorable effect: they create additional compressive longitudinal force in the face.

scholarly journals Design of reinforced concrete slabs subject to the construction joints

Vestnik MGSU ◽  
2019 ◽  
pp. 1106-1120
Author(s):  
Andrei V. Deineko ◽  
Valentina A. Kurochkina ◽  
Irina Yu. Yakovleva ◽  
Aleksandr N. Starostin
Keyword(s):  
Reinforced Concrete ◽  
Concrete Structure ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Reinforced Concrete Structure ◽  
Construction Joint ◽  
Floor Slabs ◽  
Deformation State ◽  
Stress Deformation ◽  
Construction Joints

Introduction. When erecting monolithic reinforced concrete floor slabs, a necessity of construction joints arises. The construction joints are the areas of structural weakening. The construction practice shows that the compliance with the correct technology of the construction joint arrangement is not a sufficient condition to ensure the strength balance of reinforced concrete floor slabs. As a result, the stress-deformation state calculated on the assumption of the concrete slab solidity deviates from the actual state. The relevance of the task is determined by the fact that the conformity of design and actual characteristics of the in-situ reinforced concrete structures as a whole depends on the correct calculations of construction joints. Materials and methods. The problem of implementing the construction joints in the monolithic floor slabs was considered by way of example of a residential building under construction. In the course of construction, pre-construction land surveys were carried out at the areas of the construction joint arrangement. Calculations of reinforced concrete structures using finite element method (FEM) were also performed. Results. As a result of the study, the actual deflections of the floor slabs were measured at the areas of the construction joints and FEM calculations were made on the same floor slabs, both those erected at once and those erected in stages subject to the construction joints. The difference between the calculated and actual deflections is conditioned upon the inaccurate conformity between the mathematical model and the real reinforced concrete structure, its erection and maintenance conditions. It should be noted that the deflection of horizontal reinforced concrete structures is only one of the stress-deformation state parameters that can be measured better than the others. It is shown that if the deflection of a real reinforced concrete structure does not correspond with the design estimation, the other stress-deformation state parameters will differ from the design estimation as well. Conclusions. The influence of joints can be taken into account in the scope of FEM computer-aided calculations with the explicit reproduction of the structure erection by pouring concrete, using engineering approach to the consideration of nonlinearity on the basis of the introducing reduction coefficients to the reinforced concrete effective modulus of elasticity. Solid composition modeling of reinforced concrete provides the best possibilities on taking all sorts of nonlinearity manifestations into consideration.

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