scholarly journals Effects of Concrete Core Technological Defects on the Strength of Tube Confined Concrete Elements

2018 ◽  
Vol 7 (3.2) ◽  
pp. 376
Author(s):  
Oleksandr Semko ◽  
Olga Gukasian ◽  
Serhii Skliarenko
Keyword(s):  
Concrete Strength ◽  
Experimental Studies ◽  
Fracture Pattern ◽  
Confined Concrete ◽  
Concrete Core ◽  
Different Types ◽  
Technological Defects ◽  
Concrete Elements ◽  
Core Production ◽  
Physical And Mechanical Characteristics

The paper sums up a series of experimental studies describing the influence of most types of concreting common defects, such as core weakening: weak compression inclusions, voids, height heterogeneity of concrete. The basis of the experimental study is the research on the concrete core production conditions influence on tube confined concrete elements and the change in physical and mechanical characteristics of the elements. The concrete strength is estimated based on the results of the study of specially shaped samples with given dimensions. According to the results of concreting samples with different types of modeled defects (abnormalities) inspection, the most dangerous damages of the concrete core were identified and different variants of the height strength retrogression of the elements under study were analyzed. As a result, the degree and type of damage to the tube confined concrete elements core of the samples, which affect the fracture pattern, was established. 

Composite Polymer Mesh For Masonry

2019 ◽  
pp. 15-19
Keyword(s):  
Strain State ◽  
Mechanical Characteristics ◽  
Experimental Studies ◽  
Structural Elements ◽  
Composite Polymer ◽  
Performance Technology ◽  
Different Types ◽  
Composite Grids ◽  
And Performance ◽  
Physical And Mechanical Characteristics

With the development and introduction of technologies for the production of composite materials for construction purposes in Russia appeared composite flexible ties, anchors, fittings, etc. These materials and products are not fundamentally new and have previously been studied for use for reinforcing concrete or structural elements. However, for increasing the bearing capacity of stone structures as masonry meshes they were practically not used, while masonry mesh is one of the most demanded materials in construction. The article presents experimental studies of composite meshes of different types and performance technology used in masonry. Experimentally substantiated and normalized values of physical and mechanical characteristics of rods for composite polymer grids are obtained. The evaluation of efficiency of composite meshes in masonry is made, the values of crack forming and rupture loads are determined, the peculiarities of the stress-strain state of composite grids as flexible ties are revealed, the fields of application are formulated.

A constitutive model of concrete confined by steel reinforcements and steel jackets

2005 ◽  
Vol 32 (1) ◽  
pp. 279-288 ◽  
Author(s):  
Y-F Li ◽  
S-H Chen ◽  
K-C Chang ◽  
K-Y Liu
Keyword(s):  
Constitutive Model ◽  
Concrete Strength ◽  
Strain Curve ◽  
Steel Reinforcement ◽  
Confined Concrete ◽  
Stress Strain ◽  
Steel Jacket ◽  
Proposed Model ◽  
Concrete Cylinders ◽  
Different Types

In this paper, a total of 60 concrete cylinders 30 cm in diameter and 60 cm in length confined by steel jackets of different thicknesses and different types of lateral steel reinforcements are tested to obtain the stress–strain curves of the cylinders. A constitutive model is proposed to describe the behavior of concrete confined by steel reinforcement, steel jackets, and both steel reinforcement and steel jackets used to retrofit and strengthen reinforced concrete structures. The confined concrete stress–strain curve of the proposed model is divided into two regions: the curve in the first region is approximated using a second-order polynomial equation, and that in the second region using an nth-order power-law equation, where n is a function of the unconfined concrete strength and the lateral confining stress. The results of the experiments show that different types of lateral steel reinforcement contribute greatly to the compressive strength of concrete cylinders confined by the reinforcement. Comparing the stress–strain curves of the uniaxial test with that from the proposed model, we conclude that the proposed model for concrete confined by a steel jacket and lateral steel reinforcement can predict the experimental results very well.Key words: constitutive model, steel jacket, confined concrete.

scholarly journals Choice Recommendations for Rational Concreting Technology of Steel Reinforced Concrete Structures

2018 ◽  
Vol 7 (3.2) ◽  
pp. 275
Author(s):  
Тatiana Nikiforova ◽  
Olga Gukasian ◽  
Nataliia Mahas
Keyword(s):  
Reinforced Concrete ◽  
Experimental Research ◽  
Concrete Strength ◽  
Concrete Structures ◽  
Work Conditions ◽  
Reinforced Concrete Structures ◽  
Concrete Core ◽  
Steel Reinforced Concrete ◽  
Research Cycle ◽  
Concrete Elements

In this work the experimental research cycle is described. This cycle is an affect studying of the most widespread concrete defect types, such as concrete core weakening is an inclusion of the "weak" concrete, the presence of emptiness, concrete heterogeneous by the height. The research of the manufacturing conditions affect of combine concrete core structures and the elements of physical and mechanical characteristics changing are on the experimental research base. On the researches testing base of samples with special form and given sizes the concrete strength value is appreciated. The different variants of strength decreasing on the researched element height are analyzed by the conducted testing results of the steel reinforced concrete structures. As a result of the conducted tests, the work conditions coefficient and the steel reinforced concrete elements concreting technology were formulated.  

scholarly journals Compressive Behavior of Bamboo Sheet Twining Tube-Confined Concrete Columns

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4124
Author(s):  
Xunyu Cheng ◽  
Yang Wei ◽  
Yuhan Nie ◽  
Gaofei Wang ◽  
Guofen Li
Keyword(s):  
Concrete Strength ◽  
Concrete Columns ◽  
Confined Concrete ◽  
Test Results ◽  
Compressive Behavior ◽  
Concrete Core ◽  
Strain Relationship ◽  
Mode Stress ◽  
New Type ◽  
Good Agreement

This study experimentally investigated various axial compressive parameters of a new type of confined concrete, which is termed bamboo sheet twining tube-confined concrete (BSTCC). This new composite structure was composed of an outer bamboo composite tube (BCT) jacket and a concrete core. Under axial compression, the parameters of thirty-six specimens include concrete strength (i.e., C30 and C50) and BCT thickness (i.e., 6, 12, 18, 24, and 30 layers). The mechanical properties of the BSTCC specimens from the perspective of the failure mode, stress-strain relationship, effect of BCT thickness and dilation behavior were analyzed. The results showed that, in compression, with an increase in BCT thickness in the range of 18-layers of bamboo sheets, the strength increased remarkably. When the strength of the concrete core was high, the confinement effect of the BCT was reduced. In addition, the BCT thickness relieved the dilation of the BSTCC specimens. Finally, the experimental results were compared with predictions obtained from 7 existing FRP-confined concrete models. All the predictions had good agreement with the test results, which further confirmed that the models developed for FRP-confined concrete can provide an acceptable approximation of the ultimate strength of the BSTCC specimens.

Study of Joint Work of Shell and Core of Tube Confined Concrete Elements with Strengthened Core

2019 ◽  
Vol 968 ◽  
pp. 258-266
Author(s):  
Olexandr Palyvoda ◽  
Olexandr Lapenko
Keyword(s):  
Cross Section ◽  
Low Cost ◽  
Concrete Strength ◽  
High Strength ◽  
Confined Concrete ◽  
Joint Work ◽  
Rational Combination ◽  
The Cost ◽  
Concrete Elements ◽  
Modern Building

At the present time, it is necessary to strengthen the economy mode, the resources efficiency and reduce the material consumption in construction. Modern building constructions must meet all the requirements of economy, resource conservation, which are required for construction. The main direction of their development is reducing the cost of steel (14-16%), saving cement (10-12%) and saving forest materials (12-14%). These tasks can be solved, including at the expense of reduction of material content and reduction of the cross-section of structures, due to the rational combination of concrete and steel in their joint work and through the use of high-strength materials. These requirements are satisfied with building constructions from tube confined concrete. With a relatively small cross-section, such structures can withstand significant efforts, while the concrete at the expense of a volumetric stressed state receives stresses that far exceed the prism strength, which saves steel and concrete. Applying high-strength concrete, concrete, compacted by pressing, centrifugation, it is possible to obtain significant cement savings, as due to industrial technological factors of sealing concrete mix significantly increases the concrete strength. It is possible to increase the concrete strength also due to the use of indirect reinforcement, which allows, at low cost of steel, to significantly increase the strength of structures. Improving the well-known effective methods of strengthening concrete in relation to tube confined concrete constructions with strengthened cores suitable for industrialization is an urgent and important task. The purpose of the research presented in this paper was the experimental study of tube confined concrete elements with reinforced in different methods concrete cores; the development of methods for calculating the carrying capacity and the stress-strain state of tube confined concrete elements with strengthened cores.

scholarly journals Diagnostic Reliability in the Assessment of Degradation in Precast Concrete Elements

2021 ◽  
Vol 6 (11) ◽  
pp. 164
Author(s):  
Antonio Bossio ◽  
Giuseppe Faella ◽  
Giorgio Frunzio ◽  
Mariateresa Guadagnuolo ◽  
Roberto Serpieri
Keyword(s):  
Precast Concrete ◽  
Construction Material ◽  
Concrete Strength ◽  
Research Area ◽  
Past Century ◽  
Concrete Core ◽  
Diagnostic Reliability ◽  
Core Sampling ◽  
Long Span ◽  
Concrete Elements

In the past century, precast reinforced concrete has become the most widely used construction material in infrastructure engineering, especially for long-span structures. Nowadays, a growing research area concerns the assessment of concrete strength degradation due to environmental exposure and reinforcement corrosion. This paper reports an experimental campaign on some prefabricated concrete elements that were exposed to atmospheric agents for approximately 20 years. The campaign took the uncommon opportunity to access the full inspection and sampling of rebar. The included activities had different invasiveness and encompassed inspections, core sampling, corrosion potential mapping, compressive strength tests, as well as neutralization depth assays on cored surfaces, on chisel-split surfaces, and on drilling powders. The results bring together a global diagnostic picture of very limited degradation and of elements that are fully able to attend their design service life; the latter is estimated to be considerably higher than 20 years and to exceed 75 years if the concrete mix does not show quality issues. Results also permit drawing considerations on a hierarchy of diagnostic reliability in the evaluation of RC degradation, in which concrete core sampling plays the role of golden standard.

scholarly journals COMPARISON OF CONCRETE COMPRESSIVE STRENGTH VALUES OBTAINED USING REBOUND HAMMER AND DRILLED CORE SPECIMENS

2015 ◽  
Author(s):  
Raimondas SADZEVICIUS ◽  
Tatjana SANKAUSKIENE ◽  
Petras MILIUS
Keyword(s):  
Reinforced Concrete ◽  
Concrete Strength ◽  
Hydraulic Structures ◽  
Test Results ◽  
Concrete Compressive Strength ◽  
Main Attention ◽  
Concrete Core ◽  
Rebound Hammer ◽  
Concrete Elements ◽  
Non Destructive

Durability of reinforced concrete structures depends on the maintenance conditions, surveillance, and well-timed repair of structures or reconstructions. Usually, the main attention falls on the durability determination based on the evaluation of change of main physical –mechanical properties, especially, on the compression strength of concrete. In this study, tests with the rebound hammer and concrete cores extracted from the existing reinforced concrete elements in hydraulic structures are presented. The comparison of strength values obtained with the rebound hammer and the concrete core specimens of reinforced concrete in hydraulic structures is carried out. The research was performed during the scientific expedition in the period of 2010–2014. The investigated objects are allocated in hydroschemes of Druskininkai, Marijampolė, Klaipėda districts. It was established that the results obtained using the non-destructive method were by 17 % higher than the ones obtained by performing the destructive test. However, it can be said that despite this fact, the non-destructive method offers simplicity and rapidity in use: test results are readily available on site and there is a possibility to test concrete strength of those structures where cores cannot be drilled due to thin-walled or densely reinforced structures.

scholarly journals Analytical calculation of tube confined concrete elements with strengthened cores

2021 ◽  
Vol 280 ◽  
pp. 03005
Author(s):  
Oleksandr Palyvoda ◽  
Dmytro Yermolenko ◽  
Oleksandr Andriichuk ◽  
Mindaugas Vaicekauskas ◽  
Intars Dicmanis
Keyword(s):  
Mutual Influence ◽  
Experimental Studies ◽  
Analytical Calculation ◽  
Confined Concrete ◽  
Structural Elements ◽  
Structural Element ◽  
Method Of Evaluation ◽  
In The Beginning ◽  
Concrete Elements ◽  
Theoretical Results

The approach to the formation of the analytical method of evaluation of the stress-strain state of complex rod bearing structural elements is considered in the paper. The prerequisites described cover all the fundamental features of deformation of the components in conditions of tube confined concrete with a strengthened core. This is confirmed by the results of our own experimental studies. The case of central axial compression is considered in detail. From the beginning of loading to destruction of a structural element, two fundamentally different stages of work are distinguished: in the beginning – elastic; closer to destruction – plastic. The method of variable elasticity parameters is used to describe the performance of concrete in the plastic stage. The mutual influence of components during deformation is revealed by solving the contact problem. The methodology was tested by comparing the results of our own experimental and theoretical results.

scholarly journals Calculation of tube concrete elements with strengthened cores by numerical method

2020 ◽  
Vol 166 ◽  
pp. 08002
Author(s):  
Oleksandr Palyvoda ◽  
Dmytro Yermolenko ◽  
Oksana Demchenko ◽  
Oleksandr Andriichuk ◽  
Oleksandr Nyzhnyk
Keyword(s):  
Finite Element ◽  
Experimental Studies ◽  
High Strength ◽  
Confined Concrete ◽  
Finite Element Models ◽  
Structural Elements ◽  
Cross Sectional ◽  
The Difference ◽  
Concrete Elements ◽  
Elastic Stage

The paper considers the features of formation of finite element models of tube confined concrete structural elements in the form of centrally compressed rod with strengthened cores. The prerequisites, which underlies the proposed approach to the formation of finite element models of tube confined concrete elements with strengthened cores, are given. Lengthwise the tube confined concrete elements have constant dimensions and a set of cross-sectional components. It is proved that the use of high-strength concrete allows performing calculations in the elastic stage of the work of materials. When modeling the work of rod reinforcement in tube confined concrete elements with strengthened cores, it can be represented as an imaginary cylinder with a cross-sectional area equal to the area of the rod reinforcement. The proposed prerequisites for the numerical simulation of the work of tube confined concrete elements with the strengthened cores of the studied types allowed to construct adequate finite element models. The difference in the value of the load-bearing capacity obtained from the results of physical and numerical experimental studies was 5,94…7,72 %.

Strength of Concrete-Filled Plastic Tube Stub Columns Using a Normalized Stiffness Approach

2021 ◽  
Vol 1163 ◽  
pp. 174-189
Author(s):  
Nwzad Abduljabar Abdulla
Keyword(s):  
Concrete Strength ◽  
Peak Load ◽  
Confined Concrete ◽  
Plastic Tube ◽  
Concrete Core ◽  
External Shell ◽  
Strength Models ◽  
The Impact ◽  
Stub Columns

The polymeric plastic tube can encase concrete and provide an external shell for confining and insulating concrete core from the impact of the surrounding environment. The effect of the tube and concrete strength on the concrete-filled plastic tubes (CFPT) stub columns specimens was investigated. Test results show that the tube provides passive confinement to the concrete core, which increases both the maximum peak load and the ultimate strain capacities. However, the tube has low stiffness, which affects its confinement capacity and hindrance its applications for structural use. To examine the role of tube stiffness and express the strength of a concrete-filled plastic tube, a previously proposed normalized stiffness approach for both active and passive confinement of FRP-confined concrete was adopted for the present study. From the perspective of stiffness and to better understand the behavior of CFPT specimens under uniaxial compression loads, a database of recent studies were assembled combined with the results of the present study. Several existing strength models for FRP-confined concrete were also used to predict the mechanical strength of CFPT. Two models were proposed with good predictions of the experimental results of the database.

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