Different Percentages Of Reinforcement Research Articles

The strength of complex compressed reinforced concrete structures utilising hollow concrete blocks

Structures in which elements from different materials work together are successfully used in various combinations. Recently, new, effective construction materials and products have appeared. In complex or multi-component structures, elements made of materials with different physico-chemical or strain-strength characteristics should be sensibly combined for joint work. The more fully the properties of the components’ materials are utilised, the more efficient the design itself is. By analysing global practice, it can be seen that small concrete blocks have become widespread. The use of masonry made of hollow concrete blocks in modern construction differs from traditional ones in that the void area (up to 70%) makes it possible to create complex high-strength load-bearing structures by filling them with monolithic reinforced concrete. This also enables speeding up the construction process itself and reducing the cost of work on the construction site. The purpose of the study was to examine the strength of centrally compressed columns composed of hollow blocks and concrete filling with different transverse and longitudinal reinforcements, as well as to improve their calculation methodology. Experimental studies of centrally compressed columns, with different percentages of reinforcement using hollow concrete blocks as permanent formwork, have been carried out. The article presents the results of the research on strength, but the results of the strain studies were not included in this work. The proposed method of calculating complex constructions can be applied in design practice. A good correlation was observed between the experimental results and the results of the analytical model.

НЕСУЩАЯ СПОСОБНОСТЬ БАЛОК ТАВРОВОГО ПРОФИЛЯ С ПОЛКОЙ ИЗ ВЫСОКОПРОЧНОГО БЕТОНА И ПРОДОЛЬНОЙ АРМАТУРОЙ КЛАССА А500С

Experimental and numerical studies of the bearing capacity and deformation of T-beams with a flange made of high-strength concrete and longitudinal reinforcement of class A500C with a web made of concrete of ordinary strength were carried out on prototypes of beams and numerical models. The beams being tested are considered at different percentages of reinforcement. The calculation scheme of the beams corresponded to a four-point bend. As a result of experimental and numerical studies, the nature of the destruction of beams, their deformation and the nature of cracking are determined. Experimental and numerical relationships of relative deflections on relative bending moments are obtained. A comparative analysis of the values of the bearing capacity and the relative height of the compressed zone of the beams, obtained experimentally, numerically and according to SP 63.13330.2018, was carried out. The nature of the distribution of deformations in concrete of normal section of beams at different levels of loading is determined.

Коэффициенты учета влияния теплотехнических характеристик арматуры на огнестойкость сжатых железобетонных элементов

Предложено модифицировать методику расчета огнестойкости железобетонных конструкций с учетом влияния на показатели их огнестойкости теплотехнических характеристик арматуры. В основу модификации методики положены корректирующие коэффициенты К1 и К2, полученные в результате экспериментальных исследований и численного анализа. Доказано повышение огнестойкости железобетонных элементов при увеличении содержания в них арматуры от 3,5 до 8,0 %. Methods of calculation justification of the bearing capacity of columns, with different percentages of reinforcement, have been developed, tested and fixed in domestic and foreign design standards. The calculation of the fire resistance of columns with small percentages of reinforcement has also been tested and is performed in accordance with the methodology. However, for columns with an increased percentage of reinforcement (more than 3.5 %), the use of the standard technique can lead to excessive reserves and overspending of materials, since when determining the cross-sectional temperature fields for calculating fire resistance, the method does not take into account the thermal influence of reinforcement. Previously conducted by the author experimental studies of cross-section heating temperatures and fire resistance of compressed reinforced concrete elements allowed a comparative analysis of the studied parameters with the results of numerical calculations, the obtained comparable convergence allowed further calculations of reinforced concrete elements in the Abaqus software package with different geometric dimensions and percentage of reinforcement. According to the results of the numerical study, it was determined that when reinforcing reinforced concrete elements up to 3.5%, the influence of thermal characteristics on the strength resistance of reinforced concrete elements under fire is practically absent, but when reinforcing from 3.5 % to 8 %, the greatest influence of thermal characteristics of reinforcement inclusions on the bearing capacity of the elements is manifested. At the same time, it is also recorded that this positive effect disappears when reinforcing elements of more than 8 %, which is due to the significant bearing capacity of reinforcing bars (when compared with concrete), which is 50 percent or more.

MODELING OF CROSS-SECTIONS OF WOODEN ELEMENTS FOR DIFFERENT OPTIONS AND PERCENTAGES OF REINFORCEMENT

A detailed analysis of literary sources on the study of strengthening of wooden elements by various methods was carried out.
 The calculation sequence of wooden elements reinforced with glued metal elements is proposed. An algorithm for determining the "moment-curvature" graph using optimized wood deformation diagrams is proposed. Calculations were carried out for various forms of beam cross-sections. Calculations of the cross-section were carried out and "moment-curvature" graphs were determined for different options for the reinforcement of the wooden element (with the reinforcement of the compressed zone, the stretched zone, as well as with the reinforcement of both zones). Schedules were determined with different percentages and methods of reinforcing elements. It was established that the best result of reinforcement occurs when reinforcing compressed and stretched zones, less effective when reinforcing a beam in a compressed zone, the smallest effect of reinforcing a stretched zone.
 To simulate the work of reinforced wood, the mechanical characteristics of "pine" wood with a moisture content of 12% and metal, namely the characteristics of A400S reinforcement, were used. Moment-curvature plots are given for cross-sections with different percentages of reinforcement and reinforcement in compression and tension zones. An increase in the load-bearing capacity of a bending wooden element due to various options and percentages of reinforcement reinforcement is presented.
 It is necessary to note the change in the shape of the "moment-curvature" graph with symmetrical reinforcement, namely, with an increase in the percentage of reinforcement, its shape approaches a straight line. Based on the analysis, conclusions were drawn. The volume of further experimental and theoretical research on this issue is given.

Analysis of shielding effectiveness and mechanical properties of metal matrix composite AL6061 reinforced with Al2O3 and fly ash for oblique incidence of EM wave

PurposeFiber-reinforced polymers (FRP) contain critical electrical conductivity for high-intensity radiated fields such as lightning strike susceptibility, electromagnetic energy from radar, airborne radio frequency transmitter. To provide high-intensity radiated field protection (HIRFP) for the electric and electronic aircraft system and defied the EMI effect on it, metal matrix composite was conquered. To provide the dynamic ever-increasing requirement of industries, it is necessary that Al6061 metal matrix composite assisted with AL2O3 and fly ash is used to construct the aircraft to provide HIRFP. The thickness of the material can be maintained as low as possible to use it as a coating material for the aircraft surface. X-band for oblique incidence is used to measure electromagnetic and mechanical safeguarding properties of composites.Design/methodology/approachDay by day, the applications of aerospace are becoming digital and automated. Proper shielding techniques are required to operate digital electronic devices without electromagnetic interference. It leads to a rapid rise in temperature, thermal ablation, delamination, and adverse effects on the electric and electronic aircraft system. Fly ash, a metal matrix material composite AL6061 with different percentages of reinforcement of Al2O3, was contemplated and experimented with for mechanical properties like tensile strength, density and hardness.FindingsThe obtained results compared with adjusted values and an improvement of 0.19, 0.18, 0.14 g/cm3 for density of MMC-1, MMC-2, MMC-3.31, 11 MPa for tensile strength of MMC-1, MMC-2. 24, 27, 23 BHN for hardness of MMC-1, MMC-2, MMC-3. With regard to the shielding effectiveness the results compared with adjusted values and obtained 11.36, 14.56, 19.47 dB better value than it. According to the above results, fabricated MMC’s provide superior results for a defined application like HIRFP(Surface material of aircraft).Practical implicationsIt can be used to protect electronic devices under a high-intensity radiated field, mainly in aircraft design to protect from lightning effect.Originality/valueFor a better approximation of the signal toward the practical case, the oblique incidence was considered with a different combination of Al2O3 and fly ash, reinforced to pure AL6061 to get better shielding and mechanical properties.

Chemical and mechanical reprocessed resins and bio-composites based on five epoxidized vegetable oils thermosets reinforced with flax fibers or PLA woven

Bio-epoxy resins based on five epoxidized vegetable oils were formulated with an aromatic disulfide crosslinker with diacid functionality, 2,2′-dithiodibenzoic acid (DTBA), to obtain recyclable epoxy thermosets. Flax fibres (FF) and PLA woven were used as bio-based reinforcements for these matrices. Different percentages of reinforcement were tested and the effect of the natural fibres on the matrix's crosslinking reaction was studied by DSC analysis. Then, the obtained materials were analyzed by Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Dynamic Mechanical Analysis (DMA), water absorption and Scanning Electron Microscopy (SEM). The reinforcements improved the thermal and mechanical properties of the neat resins, with tan δ values varying from 91 to 148 °C showing a good compatibility matrix-FF but a reduced one in case of matrix-PLA woven. The dynamic nature of the networks crosslinking allowed the chemical and mechanical recycling of both resins and bio-composites. Moreover, the obtained results show the possibility to recuperate the natural FF filler for the preparation of second-life generation bio-composites.

Wear, optimization and surface analysis of Al-Al2O3-TiO2 hybrid metal matrix composites

The aim of the present work is to investigate vickers hardness, wear behavior as well as to perform optimization of wear data for pure Al and Al-Al2O3-TiO2 hybrid metal matrix composites. The hybrid composite (Al-Al2O3-TiO2) was prepared by mechanical stir casting with equal proportion of reinforcement (2.5, 5.0, 7.5 and 10 wt.%). Vickers hardness, wear behavior and its optimization using ANOVA as well as TOPSIS along with the microstructure of the worn surface of prepared sample has been investigated. Vickers hardness increases with an increase in weight percentage of reinforcements. Wear test was carried out under dry sliding condition by pin-on-disc wear machine according to the ASTM G99-95a standard. Wear properties of the sample have been obtained at different percentages of reinforcement. Wear resistance of the hybrid composite increases with the variation of percentage of titanium oxide particles due to its lubricating properties. ANOVA shows that the reinforcements and load have different effect on samples wear rate. TOPSIS analysis shows rank of the sample according to its wear rate. Worn surface morphology was investigated and it showed deep grooves, more debris, delamination and rough surface in pure Al sample as compared to the high percentage of reinforced hybrid metal matrix composites.

Investigation of physical, mechanical and tribological properties of Al6061–ZrO2 nano-composites

The present investigation mainly concentrates on work done in order to explore physical, mechanical & tribological characteristics of Al6061 alloy reinforced with nano-sized zirconium dioxide particulates. Four casts of different percentages of reinforcement from 0 to 6 wt% in the steps of 2 are fabricated using liquid metallurgy technique (stir casting). The prepared composites later subjected to various physical, mechanical & wear tests and results were studied. The tests were carried out in accordance with the ASTM standards on the alloy and nano-composites. In the present investigation the physical and mechanical properties like density, hardness and tensile strength increased significantly with the increase in percentage of reinforcement in the matrix alloy, while the percentage elongation found to be decreased. The sliding wear tests were performed by using pin-on-disc the tribometer and results indicated that wear resistance of composites was higher. Off the four compositions, there were improved properties of composites with higher weight percent of reinforcement. Scanning Electron Microscope (SEM) micrographs was used after tensile testing to study fractured surfaces of specimens and wear morphology after wear testing. Overall the investigational outcomes are very interesting and motivates to do further more research.

The way to improvement of the method of calculation of rigidity of bending reinforced concrete elements from conventional ferro-concrete

The aim of the research was to improve the physical model of deformation of a bent ferro-concrete element with cracks on the basis of modern achievements in the theory of damage accumulation and fracture mechanics. The presented model allows to determine the rigidity of the element in the operation stage taking into account the damage, the work of the stretched concrete over the macrocrack, the concentration of stresses at its apex, and the presence of a pre-destruction zone in it. The analysis of the results of calculating the rigidity of elements with different percentages of reinforcement by the proposed method and the diagram method using different diagrams of concrete deformation is performed. It has been established that the work of stretched concrete over the macrocrack has a greater effect on the rigidity at a load exceeding the cracking time by no more than 30%, which is especially pronounced in strongly reinforced elements (up to 48%).

Synthesis, thermal behavior, and kinetics of degradation of alkyl hepta cyclopentyl polyhedral oligomeric silsesquioxanes/polysterene nanocomposites

The degradation of polyhedral oligomeric silsesquioxane (POSS)/polystyrene (PS) nanocomposites at different percentages of reinforcement was studied in order to verify their thermal stability in respect to the pristine PS. Analyzed compounds were prepared by in situ polymerization of styrene, in the presence of POSSs and characterized by 1H-NMR. The temperature at 5% mass loss and the activation energy of degradation, determined through kinetics literature methods, were taken into consideration in order to assess both the resistance and the kinetics of degradation. The results obtained for the synthesized polymer and composites were discussed and compared with each other and with those obtained in the past for similar alkyl-POSS/PS nanocomposites. A good improvement of the thermal stability, in respect to neat polymer, was found and showed that the presence of cyclopentyl groups at the vertices of the POSS cage led to a good interaction with the matrix. It was also drawn up a thermal stability classification among the synthesized materials and those studied in the past according to the organic nature of the substituents on the inorganic cage of the composite reinforcement.

Forensic evaluation of a large reinforced concrete specimen using radar and ultrasonic pulse echo

Non-destructive techniques play an important role in the condition assessment and evaluation of reinforced and pre-stressed concrete structures and also serve as a forensic tool in identifying various parameters such as thickness, presence of reinforcement, spacing, cover thickness, presence of other elements such as PVC pipes, steel embedment, honeycombs and voids. For exploring the effectiveness of the radar and pulse echo technique in identifying various parameters, a large-scale multi-storey reinforced concrete specimen is constructed with various features at CSIR-SERC, Chennai, with columns, beams and slabs of different sizes, cross-section having different percentages of reinforcement. The defects such as honeycombs, cracks, delamination, presence of conduits, ducts, etc. are also incorporated. This paper highlights the results from the application of these two techniques namely radar and ultrasonic pulse echo on the large-scale concrete specimen. Different features of the specimen were evaluated and the results are presented.

Damping behavior of Al/SiCP multilayer composite manufactured by roll bonding

High damping materials comprising good mechanical properties as structural materials and high damping capacity for vibration loading are the best solutions for vibration problem. In current study, functionally graded material from composite sheets with different percentages of reinforcement was manufactured by hot rolling process. The damping behavior of base alloy composite including different percentages of SiC particles and Al/SiCP multilayer composite sheets was studied at room temperature conditions. The Al/SiCP composites were found to exhibit higher damping capacity compared to Al alloy. The damping capacity increased by increase in the percentage of reinforcement. Furthermore, Al/SiCP multilayer composite sheet provided higher damping capacity in comparison to Al alloy. Therefore, damping capacity enhanced by increasing the number of layers. The main source for damping behavior in composite materials is dislocation damping whereas in stepwise multilayer composite sheets, it comes from boundary conditions between layers.

Load deformation characteristics of GFRP reinforced HPC square columns

Performance of glass fiber reinforced polymer (GFRP) reinforced high performance concrete compression members under axial loading were studied by conducting detailed experimental investigations. For the present study, twenty-four square columns of size 150 mm and slenderness ratios of 6, 8, 10 and 12 were cast, in which twelve columns reinforced with GFRP and the remaining twelve with conventional steel. For each slenderness ratio, three different percentages of reinforcement was tried with 1.4%, 2% and 3.5% each as longitudinal reinforcement for both GFRP and steel. Performance characteristics such as load carrying capacity, axial deformation, lateral deformation and rebar axial strain were studied in detail. Parametric study was done taking L/D ratio and percentage of reinforcement as parameters. Keywords: Load carrying capacity, axial deformation, lateral deformation, rebar axial strain, L/D ratio, Glass Fiber Reinforced Polymer

Editorial

Editorial

Flexural Behaviour of Concrete Beams Reinforced With GFRP Bars

Abstract: The paper presents some of the results from a large experimental program undertaken at the Department of Civil Engineering of Salerno University. The static behaviour under service conditions of concrete beams reinforced with GFRP (Glass Fibre‐Reinforced Polymer) as well as CFRP (Carbon Fibre‐Reinforced Polymer) bars and stirrups is examined. Within the whole experimental program concerning forty beams, two different concrete strengths and two different percentages of reinforcement are taken into consideration. The final aim is to investigate both deflections at midspan and crack widths. Moreover, the ultimate behaviour up to failure is also investigated. A part of this experimental program, concerning ten prototypes reinforced with GFRP bars, is here presented and discussed. Finally, comparisons with analytical predictions given by CNR‐DT 203/2006 are also shown.

Fabrication of aluminium composites reinforced with carbon fibres by a centrifugal infiltration process

Centrifugal-force infiltration was used for obtaining aluminium alloy composites reinforced with carbon fibre by the infiltration of preforms. The lost-wax-casting technique was used during the manufacturing process. Preforms fabricated with different percentages of reinforcement were heated to facilitate their filling with aluminium. Some samples were coated with nickel to favor the reinforcement wetting by the molten aluminium alloy. Composites with volume fraction of reinforcements above 7 vol.% and porosity values lower than 0.5 vol.% were obtained with this technique. The hardness of the composites increased with the volume fraction of reinforcement and the solution and the later precipitation of nickel coating caused an additional hardening effect.

Development of Al–Si–Mg alloys reinforced with diboride particles

A series of aluminium composites, with varying volume fractions of diboride particles, were made by mixing various proportions of aluminium alloy and titanium diboride (TiB 2) powders followed by hot extrusion. Different studies were carried out in the composites developed in order to obtain their general properties. The possible reaction between the matrix and reinforcement was evaluated by performing heat treatments regarding temperature at a fixed time of 1 h and at different temperatures of 350, 400, 450 and 500 °C. In this study, optical and scanning electron microscopy (SEM) with X-ray microanalysis, were used to determine the growth of the reaction layer. Mechanical properties such as ultimate strength and strain to failure were studied. The tests were performed at room and high temperature in the material in state T1 and T6. The type of damage was analysed by SEM. Tribological properties were analysed in conditions of dry friction as well as lubrication with standard lubricant in automotive industry of the type SAE 250. The evolution of the coefficient of friction in front of the speed of sliding, applied pressure, regime of lubrication and content of reinforcement in the composites was studied. The contribution also describes results from corrosion tests on aluminium composites with different percentages of reinforcement. Specimens were examined after exposure to the corrosive solution employing SEM and the type and amount of corrosion was observed.

A new model for predicting crack width with different percentages of reinforcement and concrete strength classes

This paper describes a new model for predicting crack width in presence of different percentages of reinforcement and concrete strength classes that became from 30 to 80 MPa.

Short particle strengthened aluminium alloy, fracture toughness investigated with instrumented impact tests

For different aluminium matrix alloys values of fracture mechanics were determined and compared. The investigated materials were aluminium matrix alloys with an aluminium matrix of AA 6061 (AlMg 1 SiCu) reinforced by small alumina (Al2O3) particles. Three point bend specimens with four different percentages of reinforcement, different notch orientation with electro eroded cuts or fatigue crack were investigated. The values of fracture mechanics were determined by instrumented impact with an impact velocity of 0.1 m/s. The outcome shows the behaviour of values of fracture mechanics over the percentage of reinforcement. The result shows that the instrumented impact test is a reasonable tool for the optimisation of materials for specific applications.

Effects of percentage of reinforcement and number of reinforcements in S+ on discrimination learning in the runway

Williams (1989) reported that discrimination learning and its reversal in the operant chamber are regulated by the number of reinforcements to the S+ alternative independently of reinforcement schedule, a finding Williams called the invariance effect. To determine whether there is an invariance effect in the runway, we trained four groups of rats on a successive brightness discrimination problem and its reversal. The experimental design was a factorial combination of two reinforcement schedules associated with S+ (partial reinforcement, PRF, vs. consistent reinforcement, CRF) and the number of trials per day to S+ (five vs. seven). The design provided one PRF group and one CRF group given the same number of reinforcements to S+. It also provided for a comparison between two PRF groups given different percentages of reinforcement in S+, and for PRF and CRF groups given the same number of trials in S+. PRF impaired both original discrimination learning and reversal learning whether PRF and CRF groups were equated for number of trials or for number of reinforcements, and learning was not affected by the percentage of reinforcement difference between the two PRF groups. Thus, no invariance effect was obtained.