Unreinforced Beams Research Articles

Preliminary Study on the Bending Behavior of Solid Timber Beams Reinforced with Basalt Fiber-Reinforced Polymer Bars

The purpose of this work is to test the effectiveness of strengthening timber structures by means of composite bars. This article presents the results of preliminary tests carried out on solid beams made of fir wood. The test specimens, which are classified as strength class C24, had dimensions of 7 × 17 × 330 cm. Beams were reinforced with 8 mm diameter basalt fiber-reinforced polymer (BFRP) bars. The bars were glued into grooved channels along the bottom surface. Epoxy resin was used as an adhesive. The strength tests were conducted in accordance with the requirements of EN 408+A1:2012. The four-point bending scheme was adopted. The tests were conducted in the following two series: unreinforced beams (A) and beams reinforced with composites (B). Five elements were tested in each series. The reinforcement resulted in an average increase in the bending moment value of 8.41%. The deflection value at failure increased by 19.77%. The work also includes an analysis of the failure mode and a ductility analysis. Further tests should be carried out using a higher reinforcement ratio. A higher reinforcement ratio should make the presented reinforcement configuration more effective.

Mechanical Properties of Full-Scale Wooden Beams Strengthened with Carbon-Fibre-Reinforced Polymer Sheets

The strengthening, rehabilitation and repair of wooden beams and beams made of wood-based materials are still important scientific and technical issues. This is reflected, among other things, in the number of scientific articles appearing and the involvement of research centres around the world. This is also related to society’s growing belief in the importance of ecological and sustainable development. This article presents an overview of the latest work in this field and the results of our own research on strengthening solid wooden beams with carbon-fibre-reinforced polymer (CFRP) sheets. The tests were carried out on full-size solid beams with nominal dimensions of 70 × 170 × 3300 mm. A 0.333 mm thick CFRP sheet was used for reinforcement. The research analysed various reinforcement configurations and different reinforcement ratios. For the most effective solution, a 46% increase in load capacity, 35% stiffness and 249% ductility were achieved with a reinforcement ratio of 1.7%. Generally, the higher the reinforcement ratio and coverage of the surface of the wood, the higher the strengthening effectiveness. The brittle fracture of wood in the tensile zone for unreinforced beams and the ductile crushing of wood in the compressive zone for reinforced beams were obtained. The most important achievement of this work is the description of the static work of beams in previously unanalysed configurations of strengthening and the confirmation of their effectiveness. The described solutions should extend the life of existing wooden buildings and structures and increase the competitiveness of wooden-based structures. The results indicate that, from the point of view of optimizing the cost of reinforcement, it is crucial to develop cheaper ways of combining wood and composite than to verify different types of fibres.

Bending and shear strengthening of timber beams using prestressed steel and composite bars – experimental and numerical studies

The paper describes a program of experimental and numerical tests aimed at determining the mechanical properties of beams made of laminated timber (BSH) and laminated veneer lumber (LVL) reinforced with pre-stressed bars made of basalt, glass, natural and steel fibers, basalt mats with roving and composite, polyethylene and natural yarn. The paper presents various types of reinforcements, the purpose of which was to obtain higher load-bearing capacity and stiffness in bending with shear than for unreinforced beams. The effectiveness of different reinforcement schemes was compared for seventeen beams subjected to experimental tests on a test stand, the modes of destruction were described, as well as mechanical properties, deformations and deflections for reinforced and unreinforced beams under multiply variable and long-term loading. Based on the experimental studies, a significant increase in the load-bearing capacity and stiffness of the reinforced beams subjected to simultaneous bending and shear was confirmed, and it was indicated that the reinforcements by pre-stressed bars (steel, with polymer reinforcement or natural fibers) and composite mats eliminated local defects and discontinuities in the wood, without affecting the quality and strength of the FRP-wood connection. The numerical results of the analysis of the beam models using the finite element method showed compliance with the experimental studies in terms of deflections, linear and angular strains for the reinforced and unreinforced beams

Flexural behavior of over-reinforced beam with ECC layer: Experimental and numerical simulation study

To optimize the brittle failure of reinforced conerete (RC) over-reinforeed beams and enhance their flexural performance, a novel structural form is proposed. To be specific, the Engineered Cementitious Composite (ECC) layer is installed on top of the RC over-reinforced beam (ERCOB). A total of six test beams are prepared, comprising one unreinforced beam and five reinforced beams. The variables comprised the depth of the ECC, reinforcement ratio, and whether the ECC is configured at the bottom. The test findings are subsequently compared with simulation outcomes to validate the model's precision. Next, the influence of various variables on ERCOB flexural performance, such as load-deflection response, bearing capacity, etc., is deeply analyzed. The research indicates that the ECC applied to both the top and bottom of the specimen exhibits enhanced bearing capacity and ductility. In comparison to CB-1, the maximum load and deflection ductility coefficient of EB-2 increased from 45.73 kN to 2.63–48.52 kN and 3.85, representing increases of 6.1 % and 29.6 %, respectively. It reveals that ECC layer improves the defects caused by excessive reinforcement of over-reinforced beams, and optimizes the tensile capacity of the steel bars, thus improving the bending capacity and ductility of the specimens. Finally, the prediction model of ERCOB flexural capacity is proposed to further verify the effectiveness of ERCOB. This study not only verifies the effectiveness of ECC reinforcement, but also helps to delay the failure process of structures, provide reference for future engineering application design.

Fracture Behavior of Crack-Damaged Concrete Beams Reinforced with Ultra-High-Performance Concrete Layers

Reinforcing crack-damaged concrete structures with ultra-high-performance concrete (UHPC) proves to be more time-, labor-, and cost-efficient than demolishing and rebuilding under the dual-carbon strategy. In this study, the extended finite element method (XFEM) in ABAQUS was first employed to develop a numerical model of UHPC-reinforced single-notched concrete (U+SNC) beams, analyze their crack extension behavior, and obtain the parameters necessary for calculating fracture toughness. Subsequently, the fracture toughness and instability toughness of U+SNC were calculated using the improved double K fracture criterion. The effects of varying crack height ratios (a/h) of SNC, layer thicknesses (d) of UHPC reinforcement, and fiber contents in UHPC (VSF) on the fracture properties of U+SNC beams were comprehensively investigated. The results indicate that (1) the UHPC reinforcement layer significantly enhances the load-carrying capacity and crack resistance of the U+SNC beams. Crack extension in the reinforced beams occurs more slowly than in the unreinforced beams; |(2) the fracture performance of the U+BNC beams increases exponentially with d. Considering both the reinforcement effect benefit and beam deadweight, the optimal cost-effective performance is achieved when d is 20 mm; (3) with constant d, increasing a/h favors the reinforcement effect of UHPC on the beams; (4) as VSF increases, the crack extension stage in the U+BNC beam becomes more gradual, with higher toughness and flexural properties; therefore, the best mechanical properties are achieved at a VSF of 3%.

Test and Analysis of Concrete Beams Reinforced by Polyurethane Concrete–Prestressed Steel Wires (PUC–PSWs)

In order to solve the problems of low tensile strength of composite mortar prone to cracking when reinforced concrete beams are strengthened by traditional methods, this paper proposes a new polyurethane concrete–prestressing wire (PUC–PSW) reinforcement method using polyurethane concrete (PUC) as the wire embedding material. Twelve reinforced concrete T-beams were tested for PUC–PSW flexural reinforcement. These consisted of one unreinforced beam, four PSW-reinforced beams and seven PUC–PSW-reinforced beams. The wire embedding material, wire anchorage form, PUC material depth, amount of wire and loading type were used as variables. The test results show that PUC–PSW reinforcement can significantly increase the yield load and ultimate load of the reinforced beams by 24.1% and 44.6%, respectively, compared with PSW reinforcement. When the load reached 90 kN, the crack widths of PSW-reinforced beam A2 and PUC–PSW-reinforced beam A8 were 0.17 mm and 0.1 mm, respectively. The ability of PUC–PSW reinforcement to limit crack development is better than that of PSW reinforcement, especially after the main beam steel yield. The strength, stiffness and crack-limiting ability of the reinforced beam increase with the PUC thickness of the reinforced layer.

Experimental investigations on the behaviour of structural-sized wood-CFRP composite beams in local fire

AbstractThe study involved combustion of 24 structural-sized beams under three-point bending subjected to substantial loading prior to ignition, reaching 90% of characteristic load-carrying capacity. A localised fire exposure zone was established proximal to the region experiencing the highest bending moment. The specimens were categorised into two groups: the first consisted of tituted by glued-laminated timber (B), and the second comprised wood-CFRP (carbon fibre reinforced polymer) composite (BW). Initial measurements encompassed pre-ignition static deflection and load. Subsequently, the specimens underwent controlled combustion, during which parameters including burning duration and deflection up to failure, were documented. Following cooling with sand, two cross-sectional slices were extracted from each fractured beam, enabling to find vector-based contours of the remaining cross-section. The charring rate and the approximate heat flux density for each test were determined, enabling a direct comparison of the results. A statistically significant number of specimens was examined, facilitating a comparative analysis between reinforced and unreinforced beams concerning failure time and form. Incorporating CFRP tapes among wooden constituents was found to increase the fire resistance of the structure, however, the thickness of the wooden material enveloping the CFRP composite emerges as a pivotal determinant. This issue needs thorough testing under standard fire in the future. Nevertheless, the fact is that adding CFRP tapes engenders a distinct form of beam collapse, transitioning from instantaneous cracking in B-beams to ductile failure in BW-beams.

Flexural behavior of glulam beams reinforced by bonded prestressing tendons

The rapid progression of mass timber structures towards greater spans presents a challenge for the flexural behavior of glulam beams. In this study, this challenge was addressed by reinforcing the glulam beams with prestressing tendons which were bonded to the glulam beams by epoxy resin. The objective of this study is to investigate the influence of prestressing force levels and bonded types on the flexural behavior of prestressed glulam beams. Four-point bending tests were conducted on twelve glulam beams prepared by unreinforced, unbonded prestressed or bonded prestressed techniques. Experimental results revealed that the glulam beams exhibited increased ductility under prestressing force. Compared with unreinforced beams, the prestressed beams demonstrated a remarkable increase of up to 78.8 % in flexural capacity and 13.5 % in flexural stiffness. For the prestressed beams, the flexural capacity increased as prestressing force increases. Compared with the unbonded prestressed beams at the same prestressing force level, the bonded ones exhibited higher flexural capacity and flexural stiffness. Additionally, the bonded prestressed beams exhibited a slight increase in tendon stress at the end of the prestressing tendon during loading, indicating favorable bonding behavior of epoxy resin. Numerical models were developed to predict the non-linear flexural behavior of prestressed beams, and the numerical results showed good agreements with the experimental results. Parametric analysis based on the numerical models was conducted on the prestressed beams at various prestressing force levels. The positive effect of the bonded prestressed method on the flexual behavior of glulam beams was further substantiated.

Flexural behavior of ECC reinforced RC beams under secondary load: Experimental, numerical simulation and theoretical analysis

The aim of this paper is to study the flexural behavior of reinforced concrete (RC) beams reinforced by engineered cementitious composite (ECC). The reinforcement effect of ECC on RC beam is studied by experiments, numerical simulation and theoretical analysis, considering the secondary load. Five beams were tested under static load, including two beams with ECC layers at the top and bottom (TBEB), two beams with ECC layers at the bottom (BEB) and one unreinforced beam. Different parameters in the test include reinforcement ratio, whether the top is equipped with ECC layer, and the thickness of the top ECC layer. The test data were used to validate the finite element model developed to simulate the bending response of the ECC layer reinforced beam. Then, a series of parameter studies were carried out to evaluate the effects of ECC layer thickness, reinforcement ratio and ECC elastic modulus on the reinforced beam. The experimental and numerical simulation results show that compared with other reinforced beams, TBEB equipped with 50 mm ECC layer at the top and bottom has better performance. Compared with the control beams, the ultimate bearing capacity is increased by 82.6 %, ductility and deformation capacity are increased by 2.38 times and 2.11 times, respectively. Finally, a calculation model for predicting the flexural capacity of TBEB is presented. The predicted flexural capacity is in good agreement with the experimental results.

Mechanical Properties of Fire-Damaged RC Beams Reinforced with Carbon Fiber Mesh

The bearing capacity of reinforced concrete (RC) beam will be weakened by fire. It is necessary to strengthen RC beams after fire. The carbon fiber mesh (CFM) can be used to reinforce RC beams. In this paper, RC beams were exposed to varying temperatures, followed by reinforcement with varying layers of CFM. The influence of the heating temperature and the number of CFM layers on the flexural performance of RC beams was investigated. The results indicated that the cracking loads of RC beams were 18.2, 16.4, 16.3, and 15.5 kN when the RC beams were subjected to room temperatures, 150, 350, and 550 °C. Compared to the unreinforced beams at room temperature, the cracking loads of the RC beams were reduced by 9.89%, 10.44%, and 14.84%. As the quantity of CFM reinforcement layers rises, so does the ultimate bearing capacity. For example, when the temperature was 150 °C, the ultimate loads of the beams with one and three layers of CFM were increased by 20% and 31.76% compared to the reference beam. When the temperature was 350 °C, the ultimate loads of the beams with one and three layers of CFM were increased by 19.51% and 28.04% compared to the RC beam without CFM. When the temperature was 550 °C, the ultimate loads of the beams with one and three layers of CFM were increased by 20% and 26.67% compared to the RC beam without CFM. Fire-damaged RC beams can be strengthened by one layer of CFM and mortar if the temperature was below 350 °C. Fire-damaged RC beams can be strengthened by three layers of CFM and mortar if the temperature was below 550 °C. The mechanical properties can be obviously enhanced.

Reinforcing preloaded steel I-beams by considering welding heat effects and geometric imperfections

Steel I-beams are often strengthened by welding steel cover plates to the bottom flanges of the beams. However, very limited studies have been conducted on the effect of welding heat on the behaviour of I-beams reinforced while under load. This paper presents a finite element (FE) analysis-based study on the behaviour of preloaded steel I-beams reinforced with cover plates welded to the bottom flanges of beams, considering welding procedure simulation. FE analysis is conducted to study the effects of welding heat, welding sequence, and weld length on the residual welding deformation and behaviour of steel I-beams reinforced while under load. It is observed that an appropriate welding sequence and weld length can reduce the residual lateral deformations induced from welding of a reinforcing plate to the bottom flange of the preloaded I-beam and thus control the unfavourable welding effects. Based on the analyses, a welding segment length of L/9, where L is the length of the beam, is recommended for practical applications. In addition, FE analysis shows that the direction and magnitude of the initial geometrical imperfection can change the value and direction of the residual deformation resulting from welding. Furthermore, it is observed that preloading does not have any significant effect on the behaviour and ultimate capacity of the I-beam reinforced at a preload level up to 50% of the strength of the unreinforced beam. Also, when compared with the current standards AISC 360-16 and CSA S16-9, FE analysis of reinforced steel I-beams considering welding simulation shows that the current standards significantly overpredict the moment capacities of the reinforced beams when the top flange loading effect is not considered.

Strengthening of Laminated Veneer Lumber Slabs with Fiber-Reinforced Polymer Sheets—Preliminary Study

Analyzing the feasibility of reinforcing new and existing wooden structures is a valid problem, being the subject of numerous scientific papers. The paper presents the preliminary results of a study on reinforcing Laminated Veneer Lumber (LVL) panels with composite materials bonded to exterior surfaces using epoxy resin. Glass-Fiber-Reinforced Polymer (GFRP) sheets, Carbon-Fiber-Reinforced Polymer (CFRP) sheets, and Ultra-High-Modulus (UHM) CFRP sheets were used as reinforcement. The variables in the analysis were the type of reinforcement and the number of reinforcement layers. The tests were carried out on small samples (45 × 45 × 900 mm) subjected to the so-called four-point bending test. Reinforcement positively affected the mechanical properties of composite section. The highest increases in load bearing were 37 and 48% for two layers of GFRP and CFRP, respectively. The bending stiffness increased up to 53 and 62% for two layers of CFRP and UHM CFRP, respectively. There was a change in failure mode from cracking in the tension zone for unreinforced beams to veneer shear in the support zone (for CFRP and GFRP sheets) and sheet rupture (UHM CFRP). Good agreement was obtained for estimating bending stiffness with the presented numerical and mathematical model; the relative error was up to 6% for CFRP and GFRP and up to 20% for UHM CFRP. This preliminary study proved the effectiveness of combining LVL with FRP sheets and indicated their weak spots, which should be further analyzed to improve their competitiveness against the traditional structures. The key limitation was the shear strength of LVL.

ПРОЧНОСТЬ И ДЕФОРМАТИВНОСТЬ ДЕРЕВЯННЫХ КОНСТРУКЦИЙ, АРМИРОВАННЫХ ОТРАБОТАННЫМИ ПОЛОТНАМИ ЛЕНТОЧНЫХ ПИЛ

In Russia, the volume of sawn products produced by cutting large-sized logs on band saws is increasingly expanding. The blades of band saws work from 20 to 500 hours and the technology of their secondary use is currently not provided. The creation of an effective method of reinforcing wooden structures with spent band saw blades will increase their load-bearing capacity, rigidity and operational reliability. It is assumed that in terms of the combination of strength indicators and manufacturability, the new reinforced wooden structures will correspond to existing analogues, and in terms of economic indicators they will surpass them. The conceptual novelty consists in the secondary use of man-made waste from woodworking industries in the construction of buildings and structures, which for the first time will allow to justify the effectiveness of the method of reinforcing wooden structures with treated band saw blades at a high theoretical level. The article examines beams made of solid wood with a length of 6 meters with a cross section of 100 × 200 mm, bending tests are performed. Numerical simulation of the plane stress state by the finite element method is performed. The load-bearing capacity of a beam reinforced with spent band saw blades increased by 1.5 times in comparison with an unreinforced beam.

An Evaluation of Mechanical and Fracture Characteristics of Geopolymer Concrete Incorporating Steel Fibers.

The present research aims to examine the impact of steel fiber inclusion (ranging from 0% - considered as reference, 0.08%, 0.16%, 0.24%, to 0.32%) on the mechanical and fracture characteristics of notched geopolymer concrete unreinforced beams (GCUB). These beams are prepared using fly ash and GGBFS (Ground Granulated Blast Furnace Slag), and the findings are compared with those from plain cement concrete unreinforced beams. The investigation encompasses various parameters including compressive strength, bending strength, split tensile strength, fracture energy (GF), crack mouth opening displacement (CMOD), and stress intensity factor (KIC). The primary focus is to assess how the inclusion of crimped steel fibers influences the ability of geopolymer concrete to arrest cracks. The outcomes obtained from the study underscore the effectiveness of crimped steel fibers in mitigating crack propagation and averting brittle fractures within notched geopolymer concrete unreinforced beams. The results indicate notable enhancements across all fracture and mechanical parameters upon the introduction of steel fibers. This points towards the positive impact and efficiency of steel fibers in augmenting the behavior of geopolymer concrete, making it more resistant to crack propagation and brittle failure.

Study on Flexural Behavior of Corroded I-Shaped Steel Beams Strengthened with Hybrid CFRP/GFRP Sheets.

How to effectively reinforce steel structures with rust and damage is an important research topic in the engineering field. This article takes the rusted I-beam as the research object and analyzes the effects of different CFRP/GFRP reinforcement methods on the bending performance of rusted I-beams through experimental research with a total of 1 unreinforced beam and 7 CFRP/GFRP-reinforced beams. The results show that when the number of CFRP/GFRP-reinforced layers is the same, replacing some of the CFRP with GFRP and using different interlayer mixed laying sequences have little effect on the bending bearing capacity of rusted I-beams. The number of CFRP/GFRP-reinforced layers is the key factor affecting the bending bearing capacity. At the same time, numerical simulation was conducted using finite element software to study the stress distribution and stress development law of the reinforced beam, and the numerical simulation results were consistent with the experimental results.

An Experimental and Numerical Analysis of Glued Laminated Beams Strengthened by Pre-Stressed Basalt Fibre-Reinforced Polymer Bars

Damage often develops in glued laminated timber members under high bending loads due to natural defects in the timber, which results in their low load-bearing capacity and stiffness. In order to improve the bending mechanical properties of glulam beams, a new type of longitudinal glulam reinforcement with pre-stressed basalt fibre-reinforced polymer composites (BFRP) was developed using the Near Surface Mounted (NSM) technique. The strengthening method consisted of two pre-stressed BFRP bars glued into the grooves at the bottom side of the beam; meanwhile, for the second strengthening alternative, the third BFRP bar was embedded into the groove at the top side of the beam. Therefore, an experimental study was carried out to verify this strengthening technique, in which fifteen full-size timber beams were tested with and without bonded BFRP bar reinforcement in three series. According to the results of this experimental study, it can be seen that the effective load-bearing capacity of the reinforced beams increased up to 36% and that the stiffness of the beams increased by 23% compared to the unreinforced beams. The tensile stresses in the wooden fibres were reduced by 11.32% and 25.42% on average for the beams reinforced with two and three BFRP bars, respectively. On the other hand, the compressive stresses were reduced by 16.53% and 32.10% compared to the unreinforced beams. The usual failure mode saw the cracking of the wood fibres at the defects, while for some specimens, there were also signs of cracks in the epoxy adhesive bond; however, the crack propagation was, overall, significantly reduced. The numerical calculations also show a good correlation with the experimental results. The difference in the results between the experimental and numerical analysis of the reinforced and unreinforced full-sized beams ranged between 3.63% and 11.45%.

COMPARATIVE STUDY OF CONCRETE BEAMS CONVENTIONAL REINFORCING WEAPON AND CONCRETE BEAMS WOOD WEAPON OPPOSITIFOLIUS MALLOTUS

The objective of this work is to compare the mechanical performance of concrete beams reinforced with convention reinforcement (iron) and concrete beams reinforced with oppositifolius mallotus wood with a view to building an innovative construction system for habitable or non-habitable floors of pavilions in rural areas. For this fact, nine (09) specimens of section 10x10x40cm3 were made at the rate of three (03) unreinforced concrete specimens three (03) reinforced concrete with Mallotus oppositifolius wood (vegetable reinforcement) without prior treatment and three (03) reinforced concrete specimens of conventional reinforcement (iron) which were subjected to the four-point bending test after twenty-eight (28) of age. At the end of the tests, it was found that the oppositifolius mallotus wood frame improves the four-point bending strength of the beams compared to unreinforced beams without achieving the mechanical performance of reinforced beams in conventional reinforcement. We also note a lower arrow compared to unreinforced beams. A visual analysis of the beams reinforced with mallotus oppositifolius wood (plant frame) after a total rupture shows us a need to treat the surface of the mallotus oppositifolius wood to make it rougher in order to increase its adhesion with the concrete. We thus retain the possibility of using mallotus oppositifolius wood as a vegetal frame in the construction of social housing in rural areas after its waterproofing and treatment.

Research on Flexural Bearing Capacity of Reinforced Hollow Slab Beams Based on Polyurethane Composite Material Positive and Negative Pouring Method

In order to explore the construction technology of prestressed steel strand–polyurethane cement composites for strengthening hollow slab beams, two reinforced test beams (L1, L2) and one unreinforced test beam (L0) were subjected to flexural static load tests. The deflection, ductility, stiffness, strain, and bearing capacity of each test beam were used to summarize the influence of different reinforcement techniques on the flexural performance of hollow slab beams. Research shows the prestressed steel strand–polyurethane composite material was well-bonded to the hollow slab beam, which effectively inhibits the development of concrete cracks and delays the damage process of hollow slab beams, that the reinforcement effect of the test beam L1 under the reverse pouring process was remarkable, and the bending performance of the test beam L2 under the forward pouring process of the simulated real bridge was good, which was much better than that of the unreinforced beam L0. The use of tensile prestressed steel strands and forward casting of polyurethane–cement composite materials effectively improved the flexural bearing capacity of the test beams, and this reinforcement process can be further extended to engineering applications.

Strengthening of Structural Flexural Glued Laminated Beams of Ashlar with Cords and Carbon Laminates.

Changes in the condition of existing timber structures can be caused by fatigue or biological attack, among other things. Replacing damaged timber is still very expensive, so it seems more advisable to repair or reinforce damaged elements. Therefore, in order to improve the static performance analysis of timber structures, reinforcement applications in timber elements are necessary. In this experimental study, technical-scale glulam beams measuring 82 × 162 × 3650 mm, which were reinforced with carbon strands and carbon laminates, were tested in flexure. A four-point bending test was used to determine the effectiveness of the reinforcement used in the timber beams. Internal strengthening (namely, glued carbon cords placed into cut grooves in the last and penultimate lamella) and an external surface of near-surface mounted (NSM) carbon laminates glued to the bottom surface of the beam were used to reinforce the laminated ashlar beams. As a result of this study, it was found that the bending-based mechanical properties of ash wood beams reinforced with carbon fibre-reinforced polymer composites were better than those of the reference beams. In this work, the beams were analysed in terms of the reinforcement variables used and the results were compared with those for the beams tested without reinforcement. This work proves the good behaviour of carbon fibre reinforced plastic (CFRP-Carbon fibre reinforced polymer) cords when applied to timber beams and carbon laminates. This study illustrated the different reinforcement mechanisms and showed their structural properties. Compared to the reference samples, it was found that reinforcement with carbon strings or carbon laminates increased the load-bearing capacity, flexural strength and modulus of elasticity, and reduced the amount of displacement of the timber materials, which is an excellent alternative to the use of ashlar and, above all, inferior grade materials due to the current shortage of choice grade. Experimental results showed that, with the use of carbon fibre (carbon cords SikaWrap® FX-50 C-Sika Poland Sp. z o.o., Warsaw), the load bearing capacity increased by 35.58%, or with carbon cords SikaWrap® FX-50 C and carbon laminates S&P C-Laminate type HM 50/1.4 - S&P Poland Sp. z o.o., Malbork, by 45.42%, compared to the unreinforced beams.

Experimental Research on the Effects of Waste Foundry Sand on the Strength and Micro-Structural Properties of Concrete

Now a days, a great distance has to be travelled to find good quality natural river sand. These supplies are also running out very quickly. So, a replacement for river sand is being sought after. Natural river sand is non-renewable and takes millions of years to be produced. By using manufactured sand, natural sand is completely replaced. Lack of research has led to the substitution of leftover waste foundry sand for manufactured sand in concrete. By adding used foundry sand to concrete, it is possible to enhance mechanical properties like compressive strength, fracture toughness, and flexibility. Using tests on cubes, cylinders, and unreinforced beams, the mechanical properties of concrete made with waste foundry sand and manufactured sand as fine aggregate were assessed. Tensile, splitting, and flexural strengths of the concrete were all determined after 7, 14, 28, 56, and 90 days of curing. SEM, EDS, and Thermo Gravimetric Analysis (TGA/DCs) were also used to perform micro structural analyses on the control mixture and mixtures containing 10, 20, 30, 40, and 50% waste foundry sand. The strength differences that occur when fine aggregates are replaced with waste foundry sand in different proportions are better understood, thanks to the micro structural experiments. In order to justify its use as a replacement for fine aggregate in terms of strength and microstructure studies, just the right amount of WFS was added to the concrete. Doi: 10.28991/CEJ-2022-08-10-010 Full Text: PDF