scholarly journals The Application of Ni–Ti SMA Wires in the External Prestressing of Concrete Hollow Cylinders

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1354
Author(s):  
Aleksandra Dębska ◽  
Piotr Gwoździewicz ◽  
Andrzej Seruga ◽  
Xavier Balandraud ◽  
Jean-François Destrebecq
Keyword(s):  
Thermal Activation ◽  
Internal Surface ◽  
Structural Elements ◽  
Joule Effect ◽  
External Prestressing ◽  
Test Parameters ◽  
Concrete Cylinders ◽  
Hollow Cylinders ◽  
Different Diameters ◽  
Concrete Elements

An innovative method for prestressing structural elements through the use of shape memory alloys (SMAs) is gaining increasing attention in research as this method does not require the use of mechanical anchorages for tendons. The activation of the memory effect by means of temperature variations (Joule effect) in effect produces high stresses in SMA components attached to concrete components as reported in the literature. This paper presents the work performed for the purpose of prestressing concrete hollow cylinders with the use of nickel–titanium (Ni–Ti) SMA wires. In the tests, a variety of hollow cylinders were made using the same concrete mix and with the same wall thickness (20 mm), but with different external diameters (200 mm, 250 mm, and 300 mm). Their prestressing was achieved by the means of Ni-Ti SMA wires of different diameters (1 mm, 2 mm, and 3 mm) wrapped around the cylinders. Longitudinal and circumferential strain during the thermal activation of the SMA wires by Joule heating was measured using gauges located on the internal surface of the hollow cylinders. The experimental protocol, recorded observations, and discussion of the effectiveness of the prestressing of concrete elements as a function of the test parameters are included in the text in detail. Comments on the conditions for effective prestressing of concrete cylinders with SMA wires are proposed in the conclusions of the paper.

scholarly journals Optimizing of system "column-cfrp lamellas" with the strengthening of civil structures

2021 ◽  
Vol 9 (1) ◽  
pp. 1-5
Author(s):  
Irina Mayackaya ◽  
Batyr Yazyev ◽  
Anastasia Fedchenko ◽  
Denis Demchenko
Keyword(s):  
Reinforced Concrete ◽  
Composite Materials ◽  
Carbon Fiber ◽  
Concrete Structures ◽  
Polymeric Composite ◽  
Concrete Columns ◽  
Reinforced Concrete Structures ◽  
Structural Elements ◽  
Civil Structures ◽  
Concrete Elements

Reinforced concrete elements of structures in the form of columns, beams, ceilings are widely used in the construction of buildings and structures of industrial and civil construction. In most cases, the columns serve as supports for other building elements, for example, crossbars, slabs, girders, beams. One of the cycles of the work of reinforced concrete structures is the state of their repair and reconstruction, including the stages of strengthening the elements. There is a problem of strengthening of reinforced concrete columns. The article deals with the issue of reinforcing columns and other structural elements having a cylindrical surface, with polymeric composite materials in the form of carbon fiber lamellae. The use of composite materials allows to increase the service life and strength of reinforced concrete structures used in construction.

scholarly journals Prevention of corrosion fracture of agricultural equipment during storage

2020 ◽  
Vol 164 ◽  
pp. 06002
Author(s):  
Konstantin Zabara ◽  
Artem Shpak ◽  
Alexander Shemyakin ◽  
Tatyana Melkumova ◽  
Natalya Morozova ◽  
...  
Keyword(s):  
Local Heating ◽  
Electric Energy ◽  
Design Feature ◽  
Internal Surface ◽  
Practical Implementation ◽  
Structural Elements ◽  
Entire Volume ◽  
Thermal Cover ◽  
Wave Range ◽  
The Cost

The aim of the study is to reduce metal losses of structural elements of agricultural machines caused by atmospheric corrosion. The presents the theoretical justification and practical implementation of method of storing agricultural machinery in an open area under an active thermal cover. The object of research is the experimental design of an active heat-reflecting screen equipped with heating elements that provide an infrared radiation flux in the mid-wave range of the spectrum with a wavelength of λ = 5-20 μm. A design feature of the heat-reflecting screen is the location of heating elements relative to the agricultural machine in it. The protective effect is achieved due to the fact that when the probability of dew drops increases, the elements heating the internal surface of the heat-reflecting screen and the surface of the machine are automatically switched on, while the air, which is an optically transparent medium, does not heat up, which creates conditions excluding dew. During the tests, it was found that the use of an active heat-reflecting screen allows to ensure reliable safety of the protected machine. The possibility of local heating of the inner surface of the heat-reflecting screen and the surface of the machine without heating the entire volume of air space inside the storehouse can reduce the cost of electric energy. There is no need to preheat the airspace inside the store due to the fact that the thermal effect from the heating elements is observed immediately after being switched on.

Connections in Precast Concrete Elements

2016 ◽  
Vol 691 ◽  
pp. 376-387 ◽  
Author(s):  
Ivan Hollý ◽  
Ivan Harvan
Keyword(s):  
Structural Integrity ◽  
Precast Concrete ◽  
Concrete Structures ◽  
Structural Elements ◽  
Entire Structure ◽  
Engineering Department ◽  
Final Design ◽  
Structural Engineer ◽  
Concrete Elements

The structural integrity of precast concrete structures depends mainly on the connections between the precast structural elements. The purpose of a connection is to transfer loads, restrain movement, and/or to provide stability to a component or an entire structure. Therefore, the design of connections is one of the most important aspects in the design of precast concrete structures. All connections should design with valid codes. Every precasters have developed connection details over the years that suit their particular production and erection preferences. It is common, that the structural engineer to show loads and connection locations and allow the successful manufacturer’s engineering department to provide the final design and details of the connections.

Fire Endurance of Concrete Elements Reinforced with GFRP Bars

2013 ◽  
Vol 651 ◽  
pp. 181-186
Author(s):  
Ana Almerich-Chulia ◽  
Jose Molines-Cano ◽  
Pedro Martin-Concepcion ◽  
Juan Rovira-Soler
Keyword(s):  
Fire Resistance ◽  
Structural Integrity ◽  
Fire Spread ◽  
Structural Elements ◽  
Concrete Element ◽  
Loss Of Life ◽  
Fire Engineering ◽  
Fire Endurance ◽  
Concrete Elements ◽  
Mechanics Characteristics

Fire engineering is primarily to prevent loss of life or injury during a fire. Obviously the best way to achieve this is to prevent ignition, minimizing fire spread and smoke, dying the fire before it has fully developed. When this is not possible, when the fire is fully developed, structural elements must guarantee sufficient fire resistance. If containment methods fail, structural integrity must stay for a period long enough to evacuate occupants and firemen put out it. This investigation studies the bearing capacity of GFRP reinforced concrete element, its fire resistance, variations of its mechanics characteristics and its bonding to concrete when temperature rises, together others changes that may occur in the element.

Different Approaches to Numerical Simulations of Prestressed Concrete Structural Elements

2014 ◽  
Vol 621 ◽  
pp. 148-153 ◽  
Author(s):  
Filip Hokes
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Numerical Simulations ◽  
Prestressed Concrete ◽  
Main Part ◽  
Structural Elements ◽  
Computational System ◽  
Element Level ◽  
Comparison Of The Results ◽  
Concrete Elements

The topic of this paper is the description of different approaches to numerical simulation of prestressed concrete in computational system ANSYS 14.5. Due to increasing popularity of the numerical simulations, the paper aims to divide and describe simple methods and related aspects of modeling prestress on the finite element level. The paper contains three main part: the analytical solution, the numerical solution and the final comparison of the results. The obtained numerical results proved applicability of FEA for solving problems of prestressed concrete elements.

Application Technology of Bamboo Reinforced Concrete in Building Structure

2012 ◽  
Vol 195-196 ◽  
pp. 297-302 ◽  
Author(s):  
Wei Feng Zhao ◽  
Jing Zhou ◽  
Guo Bin Bu
Keyword(s):  
Reinforced Concrete ◽  
Weight Ratio ◽  
High Strength ◽  
Concrete Columns ◽  
Building Structures ◽  
Structural Elements ◽  
High Tensile Strength ◽  
Application Technology ◽  
Steel Bar ◽  
Concrete Elements

Bamboo is mainly a tropical and subtropical plant which is found adequate in many countries. The strength of bamboo as concrete reinforcement is much lower than steel bar reinforcement. However, one of the merits is a cheap and replenishable agricultural resource and abundantly available. Due to excellent properties like high strength to weight ratio, high tensile strength and free-cutting and processing, bamboo as a potential reinforcement material in place of steel is widely available in concrete structural elements. The present paper introduces some of the existing studies and application technology of bamboo reinforced concrete elements in building structures, such as bamboo reinforced concrete columns, beams, slabs and walls.

scholarly journals A PROBABLISTIC APPROACH TO EVALUATION OF THE ULTIMATE LOAD ON FLEXURAL RC ELEMENT ON CRACK LENGTH

2020 ◽  
Vol 16 (1) ◽  
pp. 98-105
Author(s):  
Sergey Solovyev
Keyword(s):  
Reinforced Concrete ◽  
Stress Intensity ◽  
Crack Length ◽  
Reliability Analysis ◽  
Critical Stress ◽  
Probabilistic Approach ◽  
Structural Elements ◽  
Intensity Coefficient ◽  
Stress Intensity Coefficient ◽  
Concrete Elements

The fracture mechanics of concrete and reinforced concrete is a promising direction in the development of methods for reinforced concrete structural elements design and inspection. At the same time, probabilistic methods of design and behavior analysis of structural elements are of particular interest. The article describes a probabilistic approach to load-bearing capacity and reliability analysis of flexural reinforced concrete elements based on the crack length criterion. The functional relationship between the critical stress intensity coefficient of concrete and the design compressive strength of concrete is given. The article presents a method for the reliability analysis of flexural reinforced concrete elements at the operational stage with limited statistical data about the critical stress intensity coefficient of concrete. The ultimate value of the failure probability (or reliability index) should be set for each object individually based on the value of the acceptable risk.

scholarly journals Prestress state evolution during thermal activation of memory effect in concrete beams strengthened with external SMA wires

2020 ◽  
Vol 20 (4) ◽  
Author(s):  
A. Debska ◽  
Piotr Gwozdziewicz ◽  
A. Seruga ◽  
X. Balandraud ◽  
J. F. Destrebecq
Keyword(s):  
Ambient Temperature ◽  
Memory Effect ◽  
Concrete Beams ◽  
Macroscopic Model ◽  
Maximum Temperature ◽  
Joule Effect ◽  
Mechanical Coupling ◽  
State Evolution ◽  
Definition Of ◽  
Concrete Elements

Abstract The memory effect of shape-memory alloys (SMAs) has opened interesting perspectives to create prestress states in concrete elements. However, the procedure has not been yet fully resolved due to the complex thermomechanical behavior of these alloys, in addition to the practical difficulties of mechanical coupling between SMA and concrete elements. The present study deals with tests on the development of prestressing forces in concrete beams during the thermal cycle required in the procedure. Pre-stretched nickel–titanium wires were externally placed on concrete prismatic beams equipped with strain gauges. As concrete rupture may occur during the heating by the Joule effect, a compromise must be found between the SMA pre-stretch level and the maximum temperature to be applied before returning to ambient temperature. A macroscopic model was developed to analyze this compromise. The complex thermomechanical response of SMAs implies a particular attention in the definition of the ambient temperature and heating conditions for the creation of prestress states in concrete components.

Mass concrete sections and the maturity concept

1976 ◽  
Vol 3 (1) ◽  
pp. 47-57 ◽  
Author(s):  
E. G. Nisbet ◽  
S. T. Maitland
Keyword(s):  
Temperature Rise ◽  
Concrete Strength ◽  
Temperature Curve ◽  
Mass Concrete ◽  
Structural Elements ◽  
Standard Laboratory ◽  
Laboratory Conditions ◽  
Concrete Cylinders ◽  
Recording Potentiometer ◽  
Early Strength

The 28 day strength of concrete cylinders cured under standard laboratory conditions can now be reliably predicted at early ages by use of (a) the Modified Boiling Test or (b) the Autogenous Curing Test. The availability of early strength indicators for concrete can be used to great advantage during construction provided these strengths can be related to the strength of the structural elements.To permit an estimate to be made of the strength of in-place concrete on structures appurtenant to the Welland Channel By-pass, the temperature rise of the structural elements was monitored with an automatic 16 point recording potentiometer. The time temperature curve of the in-place concrete was compared to that of 6 in. by 12 in. (150 mm by 300 mm) concrete cylinders taken during casting of the structure and cured autogenously for 48 h, thus permitting an estimate of the in-place concrete strength to be made from the results of the 48 h autogenous strengths.On the basis of the in-place concrete strength estimates, decisions were made regarding the application of post tensioning forces and/or the removal of formwork and supporting shoring.

scholarly journals Reinforced concrete corbels strengthened with external prestressing

2019 ◽  
Vol 12 (4) ◽  
pp. 812-831 ◽  
Author(s):  
R. M. ROMANICHEN ◽  
R. A. SOUZA
Keyword(s):  
Reinforced Concrete ◽  
Nonlinear Analysis ◽  
Experimental Results ◽  
Analytical Models ◽  
Reinforced Concrete Structures ◽  
Structural Elements ◽  
Strut And Tie ◽  
External Prestressing ◽  
Strength Capacity ◽  
Strut And Tie Model

Abstract Reinforced concrete structures may demand, throughout their lifetime, the increase of the capacity load due to eventual changes in the load configuration. In this context, corbels could be considered structural elements which present great challenges for installing strengthening solutions. The referred difficulty is due to the fact that the strength capacity of this kind of element is dependent on the strength of a diagonal concrete strut and a tensile steel tie, both located in a very short region also subjected to interferences. In the present paper, the behavior of reinforced concrete corbels strengthened with external prestressing is investigated. For that, nonlinear analysis of short corbels (a/d ratio between 0,5 and 1,0), strengthened or not, have been applied. Also, analytical models based on the Strut-and-Tie Model were developed and the obtained results were compared with experimental results. The obtained results have demonstrated that strengthening reinforced concrete corbels using external prestressing is a fast, efficient and safe solution.

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