Papers by Keyword: Hybrid Reinforcement

Abstract: To alleviate the corrosion issue, GFRP bars are usually preferred over steel reinforcing bars. However, its application causes larger deflection and brittle failure of concrete members. To solve this, steel bars can be used in combination with GFRP bars to reduce deflection and enhance ductility. Steel-GFRP hybrid reinforced concrete is a relatively recent concept, as a result, it is still in the development stage. This study numerically examines the flexure response of concrete beams reinforced with hybrid reinforcement i.e., GFRP bars combined with steel. A total of five numerical models were developed for this investigation. The analysis methodology is based on the models developed for investigation of GFRP reinforced concrete beams which was validated with experimental studies. It is found that with an increase in the replacement percentage of steel in GFRP RC beams, the ultimate load is increased. Also, it is observed that there is a significant reduction in deflection in post-cracking and pre-steel yielding region along with enhancement in the attributes of ductility which is beneficial for serviceability aspects. The steel-GFRP hybrid-reinforced concrete beams were found to have failed by yielding of steel and subsequent concrete crushing.

Abstract: Concrete is extremely vulnerable against impact loading due to its low tensile strength and pronounced brittleness. The application of thin strengthening layers, containing Textile Reinforced Concrete (TRC) and Strain-Hardening Cement-based Composites (SHCCs) in a ductile cement-based composite, is a promising solution to enhance the impact resistance of existing concrete structures. Three-dimensional (3D) textile structures exhibit numerous advantages over two-dimensional (2D) ones, most importantly higher shear, bending and energy absorption capacity, hence, appear to be instrumental in providing sufficient reinforcement to the target strengthening layers. However, design variability and optimization possibility of available 3D textile reinforcement are restricted. This paper presents the development of novel textile-based 3D truss reinforcement that can overcome these limitations. On the basis of woven 3D cellular structures, innovative pyramidal 3D truss reinforcement with favorable load-bearing capacity as well as notable energy absorption capability is developed and successfully realized. To investigate the feasibility and efficacy, cement-based composite consisting SHCC and newly developed pyramidal 3D truss reinforcement is prepared and tested under high-speed tensile loading as well as transversal impact loading. The experimental results show that woven 3D truss reinforcement is highly compatible with SHCC, and significantly enhances its impact resistance. Furthermore, SHCC reinforced with novel pyramidal 3D truss structure remarkably outperforms that with 2D carbon reinforcing structure approved for commercial use.

Abstract: The sustainable development of industry and society requires new approaches to the building structures design. The article presents the indices of strength, crack resistance and width of crack opening obtained as a result of experimental testing of beams with hybrid reinforcement with basalt plastic and metal armature. The following beams were examined for comparison purposes: the ferroconcrete beams of the control-series, and the twin beams reinforced only with basalt-plastic reinforcement. It was found that the replacement of the metal armature with basalt plastics led to an increase in strength, on average, by 40%. Similar strength indices were obtained for hybrid reinforcement beams. Crack resistance indices of hybrid reinforcement beams were found to be close to ferroconcrete beams of the control series. Crack resistance indices for these beams were also by 84... 89% higher in comparison with beams reinforced with basalt-plastics. The width of crack openings in hybrid reinforced beams did not exceed the maximum permissible norms at the operational level of loads (70% of destructive) and were smaller than in beams reinforced with basalt plastic reinforcement. Hybrid reinforcement efficiency has been established to improve the performance criteria of beams reinforced with composite armature.

Abstract: It is presented the study of the beam samples reinforced with metal armature, BFRP armature and beams with hybrid reinforcement using metal and BFRP armature. Half of the tested samples of beams were manufactured on concrete with river sand, as a fine aggregate. The others were made on concrete with fractionated fine wastes of Mining and Beneficiary complex (MBC) instead of the river sand. The tests were carried out by static loading of the scheme of a single-run free beam loaded in the thirds of gear. It was established that the beams reinforced with BFRP armature and the beams with hybrid reinforcement showed an increase of strength, about 40%, compared with the beams reinforced with metal reinforcement. The deflections of the beams reinforced with BFRP armature were 315% -331% higher than the deflections of the beams reinforced with metal reinforcement and 165% -205% higher than it is allowed by standards. The use of hybrid reinforcement allowed reducing their deflections in two times compared to the beams reinforced with BFRP armature. At a load level of 60% of the destructive, the deflections of beams with hybrid reinforcement BFRP and metal armature did not exceed the maximum permissible norm. When concrete samples manufactured, the substitution of the river sand with fine fractionated wastes from the Mining and Beneficiary complex (MBC) did not affect their durability and deformability (the difference between the values according to these indicators is within the statistical error).

Abstract: As part of the development and research of UHPC materials, the broad professional public deals mainly with the determination of the basic physical and mechanical parameters, in particular the compressive strength, that is considered as a determining parameter for these cement-based composites. The strength of the composite material is determined under normal laboratory conditions. Fine cement-based composite materials are increasingly used not only for academic purposes but also for practical applications. Therefore, it is necessary to focus on other parameters that determine these new Hi-Tech materials. The mechanical properties of materials at elevated temperatures belong to an area that is not properly defined not only in the Czech Republic but also in the world. Research into the behavior of these composite materials and their thermal loading can provide additional information and basics to expand these building materials such as France, USA, Japan and other countries around the world. In the Czech standards applicable to the design of concrete structures subjected to thermal stress, the values of the reduction coefficient Kc, θ are used only for commonly used dense concrete and also for expanded concrete. It is clear that these values cannot be used for fine-grained composite materials with cement binder reinforced hybrid reinforcements. The aim of the paper is to determine and describe the behavior of these materials in the temperature range of 20 ° C to 1000 ° C for two test modes that affect residual strength and high temperature strength.

Abstract: The introduction of wide range of novel raw materials and composites are tuning exceptionally the construction industry on its head. The recent research trends majorly intensified on hybrid concept using the varied materials collectively. This study primarily aims at experimentally investigating the response of concrete exterior beam column joint with Hybrid Reinforcement Technique (HRT) for reverse cyclic load conditions. The on-site fabricated, Hand Layup Carbon Fibre Reinforced Polymer (CFRP-HL) stirrups and the conventional steel main reinforcements form a hybrid reinforcement system in this study. The on-site constructed CFRP-HL reinforcement serves as a substitute for pre-fabricated CFRP rebars which has limitations and inflexibility in adapting the construction alterations. In total six types of specimens, a couple of test specimens are strengthened with HRT and another with external bond CFRP fibre wrap. In the remaining three specimens, one with non-conventional steel detailing and a couple of conventional joints that are designed according to IS 456:2000 and IS 13920:1993 respectively. In addition, the influence of varied spacing of stirrups in specimens is studied separately. Further, the test results on overall strength, stiffness, load deflection characteristics, dissipated energy and ductility of test specimens is evaluated and discussed. The use of CFRP-HL with steel as hybrid combination enables to comprehend the benefit from their distinctive characteristics. This proposal strongly improves the greater flexibility of using CFRP-HL in field as needed.

Abstract: The effect of high temperature load on mechanical properties and porosity of a newly designed Ultra High Performance Fiber Reinforced Concrete (UHPFRC) is studied. The hybrid reinforcement of UHPFRC is based on a mixture of polypropylene and steel fibers. In order to identify influence of high temperature exposure on UHPFRC, its residual mechanical parameters such as compressive strength, flexural strength and Young’s modulus of elasticity are accessed. Moreover, residual bulk density, matrix density and total open porosity are examined and related to the monitored structural changes. Simultaneous Thermal Analysis (STA) is employed in order to describe transformation processes during high temperature loading. The conducted tests provide practical information for controlled regulation of water vapor transport in a low permeable cementitious composite in order to decrease risk of spalling.

Abstract: Now a day’s Hybrid Metal Matrix composites has a large number of applications in automobiles, aircrafts and structural applications like brake rotors, engine parts and cylinder liners. The aim of this study is to determine the mechanical properties of boron carbide (B₄C) and zirconium silicate (ZrSiO₄) particulate reinforced with AA6063 alloy composites. In this experimental study, B₄C and ZrSiO₄ particulates reinforced with AA6063 composites were manufactured by stir casting technique. Mechanical properties of these composite materials were investigated by different weight percentages, 3%, 6%, 9% of boron carbide (B₄C) and 9%, 6%, 3% of zirconium silicate (ZrSiO₄) respectively. The mechanical properties evaluation reveals variations in hardness and the tensile strength values with the composite combinations investigated in this work. From the experimental studies, the optimum volume fraction of hybrid reinforcement in AA6063 alloy on the basis of mechanical properties and SEM analysis is also determined.

Abstract: The use of natural fibers has a great interest due to their damping properties, low density and moderate strength. The effect of incorporating chopped natural fibers, as disperse reinforced phase, on the dynamic or quasi-static elastic modulus of glass fiber laminates is presented. Squares of 32 cm² plain wave glass fiber prepreg with epoxy resin were used in a stacking sequence [0]4. Short length chopped (1-3 mm) natural coir fiber was placed in between of each glass fiber prepreg sheet (4) and laminates were prepared by the vacuum bag technique. The volume fraction of natural fiber was 30% (mass fraction of 10%) and samples of 254 mm length and 25.4 mm width were cut and tested at vibration conditions in a cantilever beam arrangement. The vibration frequency was measured by an accelerometer ADXL335 at z-axis, perpendicular to the sample test plane and the elastic modulus was estimated with the cantilever model. The results showed that the samples with coir fiber showed an increase in the dynamic elastic modulus value of 150 to 171% with regard to that one of glass fiber samples without fiber. Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials (ASTM D3039) was also used to further characterize the thin samples (≈0.75 mm) with an Instron machine 8800, 25kN. The tensile properties obtained are lower for coir fiber samples than the ones without.

Abstract: In-situ aluminum matrix composites have good bonding strength and homogeneous distribution of particles, which offer improved mechanical property and wear resistance. Electrical discharge machining is considered as a suitable process for making complicated shape of difficult to machine materials. In this experimental work AA6061-6% TiB₂/ZrB₂ in-situ metal matrix composite was fabricated using flex assisted synthesis. This experimental investigation is focused to study the influence of electrical discharge machining process parameter on surface roughness in machining of the AA6061-6% TiB₂ /ZrB₂ composite. Taguchi method and L₉ orthogonal lay out are applied to conduct the experimental work. Analysis of variance was performed to evaluate the percentage of contribution of each parameter. The analysis of the result indicates that discharge current has strongest influence on the surface roughness. This experimental study helps to select the optimal machining parameter to achieve good surface finish.