Search results for: reinforced vulcanized rubbers

Authors: O. Vlcek

Abstract:

The paper deals with current issues in research of advanced methods to increase reliability of traditional timber structural elements. It analyses the issue of strengthening of bent timber beams, such as ceiling beams in old (historical) buildings with additional concrete slab in combination with externally bonded fibre - reinforced polymer. The paper describes experimental testing of composite timber-concrete beam with FRP reinforcement and compares results with FEM analysis.

Keywords: timber-concrete composite, strengthening, fibre-reinforced polymer, experimental analysis

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Authors: Faezeh Shalchy

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Concrete is the most used materials in the world. It is also one of the most versatile while complex materials which human have used for construction. However, concrete is weak in tension, over the past thirty years many studies were accomplished to improve the tensile properties of concrete (cement-based materials) using a variety of methods. One of the most successful attempts is to use polymeric fibers in the structure of concrete to obtain a composite with high tensile strength and ductility. Understanding the mechanical behavior of fiber reinforced concrete requires the knowledge of the fiber/matrix interfaces at the small scale. In this study, a combination of numerical simulations and experimental techniques have been used to study the nano structure of fiber/matrix interfaces. A new model for calcium-silicate-hydrate (C-S-H)/fiber interfaces is proposed based on Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX) analysis. The adhesion energy between the C-S-H gel and 2 different polymeric fibers (polyvinyl alcohol and polypropylene) was numerically studied at the atomistic level since adhesion is one of the key factors in the design of fiber reinforced composites. The mechanisms of adhesion as a function of the nano structure of fiber/matrix interfaces are also studied and discussed.

Keywords: fiber-reinforced concrete, adhesion, molecular modeling

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Authors: Rabab Allouzi, Amer Alkloub

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As the complex shaped buildings become a popular trend for architects, this paper is presented to investigate the performance of reinforced concrete flat plate-inclined column connection. The studies on the inclined column and flat plate connections are not sufficient in comparison to those on the conventional structures. The effect of column angle of inclination on the punching shear strength is found significant and studied herein. This paper presents a non-linear finite element based modeling approach to estimate behavior of RC flat plate inclined column connection. Results from simulations of RC flat plate-straight column connection show good agreement with experimental response of specimens tested by other researchers. The model is further used to study the response of inclined columns to punching at various ranges of inclination angles. The inclination angle can be included in the punching shear strength provisions provided by ACI 318-14 to account for the effect of column inclination.

Keywords: punching shear, non-linear finite element, inclined columns, reinforced concrete connection

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Authors: Khaing Su Su Than, Hibino Yo

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Seismic evaluation is needed upon the buildings in Myanmar. Microtremor measurement was conducted in the main cities, Mandalay and Yangon. In order to evaluate the seismic properties of buildings currently under construction, seismic information was gathered for six buildings in Yangon city and four buildings in Mandalay city. The investigated buildings vary from 12m-80 m in height, and mostly public residence structures. The predominant period obtained from frequency results of the investigated buildings were given by horizontal to vertical spectral ratio (HVSR) for each building. The fundamental period results have been calculated in the form of Fourier amplitude spectra of translation along with the main structure. Based on that, the height (H)-period(T) relationship was observed as T=0.012H-0.017H in the buildings of Yangon and, observed the relationship as T=0.014H-0.019H in the buildings of Mandalay. The results showed that the relationship between height and natural period was slightly under the relationship T=0.02H that is used for Japanese reinforced concrete buildings, which indicated that the results depend on the properties and characteristics of materials used.

Keywords: HVSR, height-period relationship, microtremor, Myanmar earthquake, reinforced concrete structures

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Authors: Daniel Ferreira, José M. Marques Oliveira, Filipe Oliveira

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Wear phenomena is critical in injection moulding processes, causing failure of the components, and making the parts more expensive with an additional wasting time. When very abrasive materials are being injected inside the steel mould’s cavities, such as polymers reinforced with abrasive fibres, the consequences of the wear are more evident. Maraging steel (1.2709) is commonly employed in moulding components to resist in very aggressive injection conditions. In this work, the wear performance of the SLM produced 1.2709 maraging steel reinforced by ultrafine titanium and tungsten carbide (TiC-WC), was investigated using a pin-on-disk testing apparatus. A polypropylene reinforced with 40 wt.% fibreglass (PP40) disk, was used as the counterpart material. The wear tests were performed at 40 N constant load and 0.4 ms-1 sliding speed at room temperature and humidity conditions. The experimental results demonstrated that the wear rate in the 18Ni300-TiC-WC composite is lower than the unreinforced 18Ni300 matrix. The morphology and chemical composition of the worn surfaces was observed by 3D optical profilometry and scanning electron microscopy (SEM), respectively. The resulting debris, caused by friction, were also analysed by SEM and energy dispersive X-ray spectroscopy (EDS). Their morphology showed distinct shapes and sizes, which indicated that the wear mechanisms, may be different in maraging steel produced by casting and SLM. The coefficient of friction (COF) was recorded during the tests, which helped to elucidate the wear mechanisms involved.

Keywords: selective laser melting, nanocomposites, injection moulding, polypropylene with fibreglass

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Authors: M. Hakan Arslan, I. Hakkı Erkan

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Overstrength factor is an important parameter of load reduction factor. In this research, the overstrength factor (Ω) of reinforced concrete (RC) buildings and the parameters of Ω in TEC-2016 draft version have been explored. For this aim, 48 RC buildings have been modeled according to the current seismic code TEC-2007 and Turkish Building Code-500-2000 criteria. After modelling step, nonlinear static pushover analyses have been applied to these buildings by using TEC-2007 Section 7. After the nonlinear pushover analyses, capacity curves (lateral load-lateral top displacement curves) have been plotted for 48 RC buildings. Using capacity curves, overstrength factors (Ω) have been derived for each building. The obtained overstrength factor (Ω) values have been compared with TEC-2016 values for related building types, and the results have been interpreted. According to the obtained values from the study, overstrength factor (Ω) given in TEC-2016 draft code is found quite suitable.

Keywords: reinforced concrete buildings, overstrength factor, earthquake, static pushover analysis

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Authors: Anas M. Fares

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Reinforced concrete shear walls are the most frequently used forms of lateral resisting structural elements. These walls may take many forms due to their functions and locations in the building. In Palestine, the most lateral resisting forces construction forms is the cantilever shear walls system. It is thus of prime importance to study the rigidity of these walls. The virtual work theorem is used to derive the total lateral deflection of cantilever shear walls due to flexural and shear deformation. The case of neglecting the shear deformation in the walls is also studied, and it is found that the wall height to length aspect ratio (H/B) plays a major role in calculating the lateral deflection and the rigidity of such walls. When the H/B is more than or equal to 3.7, the shear deformation may be neglected from the calculation of the lateral deflection. Moreover, the walls with the same material properties, same lateral load value, and same aspect ratio, shall have the same of both the lateral deflection and the rigidity. Finally, an equation to calculate the total rigidity and total deflection of such walls is derived by using the virtual work theorem for a cantilever beam.

Keywords: cantilever shear walls, flexural deformation, lateral deflection, lateral loads, reinforced concrete shear walls, rigidity, shear deformation, virtual work theorem

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Authors: I. Ioannou, I. M. Gitman

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This study focused on the contribution of micro-mechanical parameters on the macro-mechanical response of short fiber composites, namely polypropylene matrix reinforced by glass fibers. In the framework of this paper, an attention has been given to the glass fibers length, as micromechanical parameter influences the overall macroscopic material’s behavior. Three dimensional numerical models were developed and analyzed through the concept of a Representative Volume Element (RVE). Results of the RVE-based approach were compared with analytical Halpin-Tsai’s model.

Keywords: effective properties, homogenization, representative volume element, short fiber reinforced composites

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Authors: E. H. N. Gashti, M. Zarrini, M. Irannezhad, J. R. Langroudi

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Using ETABS software, this study analyzed 23 buildings to evaluate effects of mistakes during construction phase on buildings structural behavior. For modelling, two different loadings were assumed: 1) design loading and 2) loading due to the effects of mistakes in construction phase. Research results determined that considering traditional construction methods for buildings resulted in a significant increase in dead loads and consequently intensified the displacements and base-shears of buildings under seismic loads.

Keywords: reinforced-concrete buildings, construction mistakes, base-shear, displacements, failure

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Authors: D. Jayalakshmi, S. S. Bhosale

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This paper, in its first part, presents the state-of-the-art literature of design approaches for geosynthetic reinforced unpaved roads. The literature starting since 1970 and the critical appraisal of flexible pavement design by Giroud and Han (2004) and Jonathan Fannin (2006) is presented. The design example is illustrated for Indian conditions. The example emphasizes the results computed by Giroud and Han's (2004) design method with the Indian road congress guidelines by IRC SP 72 -2015. The input data considered are related to the subgrade soil condition of Maharashtra State in India. The unified soil classification of the subgrade soil is inorganic clay with high plasticity (CH), which is expansive with a California bearing ratio (CBR) of 2% to 3%. The example exhibits the unreinforced case and geotextile as reinforcement by varying the rut depth from 25 mm to 100 mm. The present result reveals the base thickness for the unreinforced case from the IRC design catalogs is in good agreement with Giroud and Han (2004) approach for a range of 75 mm to 100 mm rut depth. Since Giroud and Han (2004) method is applicable for both reinforced and unreinforced cases, for the same data with appropriate Nc factor, for the same rut depth, the base thickness for the reinforced case has arrived for the Indian condition. From this trial, for the CBR of 2%, the base thickness reduction due to geotextile inclusion is 35%. For the CBR range of 2% to 5% with different stiffness in geosynthetics, the reduction in base course thickness will be evaluated, and the validation will be executed by the full-scale accelerated pavement testing set up at the College of Engineering Pune (COE), India.

Keywords: base thickness, design approach, equation, full scale accelerated pavement set up, Indian condition

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Authors: Tasnim Kallel, Rim Taktak

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In this experimental work, fiber reinforced polymer (FRP) composite laminates were manufactured using hand lay-up technique. The unsaturated polyester (UP) and vinylester (VE) were considered as resins reinforced with different woven fabrics (bidirectional and quadriaxial rovings). The mechanical behaviour of the resulting composites was studied and then compared. A focus was essentially done on the evaluation of the effect of E-Glass fiber and ply orientation on the mechanical properties such as tensile strength, flexural strength, and hardness of the studied composite laminates. Also, crack paths and fracture surfaces were examined, and failure mechanisms were analyzed. From the main results, it was found that the quadriaxial composite laminates (QA/VE and QA/UP) with stacking sequences of [0°, +45°, 90°, -45°] present a very ductile tensile behaviour. The other laminate samples (R500/VE, RM/VE, R500/UP and RM/UP) show a very brittle behaviour whatever the used resin. The intrinsic toughness KIC of QA/VE laminate, obtained in fracture tests, are found more important than that of RM/VE composite. Thus, the QA/VE samples, as multidirectional laminate, presents the highest interlaminar fracture resistance.

Keywords: crack growth, fiber orientation, fracture behavior, e-glass fiber fabric, laminate composite, mechanical behavior

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Authors: S. Ghanaraja, Subrata Ray, S. K. Nath

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Particle reinforced Metal Matrix Composite (MMC) succeeds in synergizing the metallic matrix with ceramic particle reinforcements to result in improved strength, particularly at elevated temperatures, but adversely it affects the ductility of the matrix because of agglomeration and porosity. The present study investigates the outcome of tensile properties in a cast and hot forged composite reinforced simultaneously with coarse and fine particles. Nano-sized alumina particles have been generated by milling mixture of aluminum and manganese dioxide powders. Milled particles after drying are added to molten metal and the resulting slurry is cast. The microstructure of the composites shows good distribution of both the size categories of particles without significant clustering. The presence of nanoparticles along with coarser particles in a composite improves both strength and ductility considerably. Delay in debonding of coarser particles to higher stress is due to reduced mismatch in extension caused by increased strain hardening in presence of the nanoparticles. However, higher addition of powder mix beyond a limit results in deterioration of mechanical properties, possibly due to clustering of nanoparticles. The porosity in cast composite generally increases with the increasing addition of powder mix as observed during process and on forging it has got reduced. The base alloy and nanocomposites show improvement in flow stress which could be attributed to lowering of porosity and grain refinement as a consequence of forging.

Keywords: aluminium, alumina, nano-particle reinforced composites, porosity

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Authors: Zaidour Mohamed, Ghalem Ali Jr., Achit Henni Mohamed

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This project is destined to study pole junctions of reinforced concrete beams subjected to seismic loads. A literature review was made to clarify the work done by researchers in the last three decades and especially the results of the last two years that were studied for the determination of the method of calculating the transverse reinforcement in the different nodes of a structure. For implementation efforts in the columns and beams of a building R + 4 in zone 3 were calculated using the finite element method through software. These results are the basis of our work which led to the calculation of the transverse reinforcement of the nodes of the structure in question.

Keywords: beam–column joints, cyclic loading, shearing force, damaged joint

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Authors: Terence Tumolva, Johannes Kristoff Vito, Joanna Crystelle Ragasa, Renz Marion Dela Cruz

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Natural fiber reinforced polymer (NFRP) composites have been the focus of various research projects due to their advantages over synthetic fiber-reinforced composites. For this study, ana haw is used as the fiber source due to its abundance throughout the Philippines. A problem addressed in this study is the need for an environment-friendly method of fiber treatment. The use of sodium alginate to treat fibers was thus investigated. The fibers were immersed in a sodium alginate solution and then in a calcium chloride solution afterwards. The treated fibers were used to reinforce orthophthalic unsaturated polyester (ortho-UP) resin. The mechanical properties were tested using a universal testing machine (UTM), and the fracture surfaces were characterized using scanning electron microscope (SEM). Results showed that the sodium alginate treatment had increased the tensile and flexural strength of the composite. The increase in fiber load had also been found to increase the stiffness of the composite. However, sodium alginate treatment did not provide any significant improvement in the wet mechanical properties of the NFRP. The composite is comparable to some commercially available polymeric materials.

Keywords: NFRP, composite, alginate, anahaw, polymer

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Authors: K. Krushnamurty, D. Rasmitha, I. Srikanth, K. Ramji, Ch. Subrahmanyam

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E-glass-epoxy laminated composites having different fiber volume fractions (40, 50, 60 and 70) were fabricated with and without the addition of nanoclay. Flexural strength and tensile strength of the composite laminates were determined. It was observed that, with increasing the fiber volume fraction (Vf) of fiber from 40 to 60, the ability of nanoclay to enhance the tensile and flexural strength of E-glass-epoxy composites decreases significantly. At 70Vf, the tensile and flexural strength of the nanoclay reinforced E-glass-epoxy were found to be lowest when compared to the E-glass-epoxy composite made without the addition of nanoclay. Based on the obtained data and microstructure of the tested samples, plausible mechanism for the observed trends has been proposed. The enhanced mechanical properties for nanoclay reinforced E-glass-epoxy composites for 40-60 Vf, due to higher interface toughness coupled with strong interfilament bonding may have ensured the homogeneous load distribution across all the glass fibers. Results in the decrease in mechanical properties at 70Vf, may be due to the inability of the matrix to bind the nanoclay and glass-fibers.

Keywords: e-glass-epoxy composite laminates, fiber volume fraction, e-glass fiber, mechanical properties, delamination

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Authors: Amessalu Atenafu Gelaw, Nele Rath

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Currently, laser hardening process is becoming among the most efficient and effective hardening technique due to its significant advantages. The source where heat is generated, the absence of cooling media, self-quenching property, less distortion nature due to localized heat input, environmental friendly behavior and less time to finish the operation are among the main benefits to adopt this technology. This day, a variety of injection machines are used in plastic, textile, electrical and mechanical industries. Due to the fast growing of composite technology, fiber reinforced polymer matrix becoming optional solution to use in these industries. Due, to the abrasion nature of fiber reinforced polymer matrix composite on the injection components, many parts are outdated before the design period. Niko, a company specialized in injection molded products, suffers from the short lifetime of the injection nozzles of the molds, due to the use of fiber reinforced and, therefore, more abrasive polymer matrix. To prolong the lifetime of these molds, hardening the susceptible component like the injecting nozzles was a must. In this paper, the laser hardening process is investigated on Unimax, a type of stainless steel. The investigation to get optimal results for the nozzle-case was performed in three steps. First, the optimal parameters for maximum possible hardenability for the investigated nozzle material is investigated on a flat sample, using experimental testing as well as thermal simulation. Next, the effect of an inclination on the maximum temperature is analyzed both by experimental testing and validation through simulation. Finally, the data combined and applied for the nozzle. This paper describes possible strategies and methods for laser hardening of the nozzle to reach hardness of at least 720 HV for the material investigated. It has been proven, that the nozzle can be laser hardened to over 900 HV with the option of even higher results when more precise positioning of the laser can be assured.

Keywords: absorptivity, fiber reinforced matrix, laser hardening, Nd:YAG laser

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Authors: Arber Sejdiji, Jan Schmitz-Huebsch, Christian Mittelstedt

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Due to its use in a broad range of temperatures, the prediction of elastic properties of fiber composite materials under thermal load is significant. Especially the transversal stiffness dominates the potential of use for fiber-reinforced composites (FRC). A numerical study on the influence of thermal stress on transversal stiffness of fiber-reinforced composites is presented. In the numerical study, a representative volume element (RVE) is used to estimate the elastic properties of a unidirectional ply with finite element method (FEM). For the investigation, periodic boundary conditions are applied to the RVE. Firstly, the elastic properties under pure mechanical load are derived numerically and compared to results, which are obtained by analytical methods. Thereupon thermo-mechanical load is implemented into the model to investigate the influence of temperature change with low temperature as a key aspect. Regarding low temperatures, the transversal stiffness increases intensely, especially when thermal stress is dominant over mechanical stress. This paper outlines the employed numerical methods as well as the derived results.

Keywords: elastic properties, micromechanics, thermal stress, representative volume element

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Authors: L. Asaro, M. Gratton, S. Seghar, N. Poirot, N. Ait Hocine

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Rubber waste disposal is an environmental problem. Particularly, many researches are centered in the management of discarded tires. In spite of all different ways of handling used tires, the most common is to deposit them in a landfill, creating a stock of tires. These stocks can cause fire danger and provide ambient for rodents, mosquitoes and other pests, causing health hazards and environmental problems. Because of the three-dimensional structure of the rubbers and their specific composition that include several additives, their recycling is a current technological challenge. The technique which can break down the crosslink bonds in the rubber is called devulcanization. Strictly, devulcanization can be defined as a process where poly-, di-, and mono-sulfidic bonds, formed during vulcanization, are totally or partially broken. In the recent years, super critical carbon dioxide (scCO₂) was proposed as a green devulcanization atmosphere. This is because it is chemically inactive, nontoxic, nonflammable and inexpensive. Its critical point can be easily reached (31.1 °C and 7.38 MPa), and residual scCO₂ in the devulcanized rubber can be easily and rapidly removed by releasing pressure. In this study thermomechanical devulcanization of ground tire rubber (GTR) was performed in a twin screw extruder under diverse operation conditions. Supercritical CO₂ was added in different quantities to promote the devulcanization. Temperature, screw speed and quantity of CO₂ were the parameters that were varied during the process. The devulcanized rubber was characterized by its devulcanization percent and crosslink density by swelling in toluene. Infrared spectroscopy (FTIR) and Gel permeation chromatography (GPC) were also done, and the results were related with the Mooney viscosity. The results showed that the crosslink density decreases as the extruder temperature and speed increases, and, as expected, the soluble fraction increase with both parameters. The Mooney viscosity of the devulcanized rubber decreases as the extruder temperature increases. The reached values were in good correlation (R= 0.96) with de the soluble fraction. In order to analyze if the devulcanization was caused by main chains or crosslink scission, the Horikx's theory was used. Results showed that all tests fall in the curve that corresponds to the sulfur bond scission, which indicates that the devulcanization has successfully happened without degradation of the rubber. In the spectra obtained by FTIR, it was observed that none of the characteristic peaks of the GTR were modified by the different devulcanization conditions. This was expected, because due to the low sulfur content (~1.4 phr) and the multiphasic composition of the GTR, it is very difficult to evaluate the devulcanization by this technique. The lowest crosslink density was reached with 1 cm³/min of CO₂, and the power consumed in that process was also near to the minimum. These results encourage us to do further analyses to better understand the effect of the different conditions on the devulcanization process. The analysis is currently extended to monophasic rubbers as ethylene propylene diene monomer rubber (EPDM) and natural rubber (NR).

Keywords: devulcanization, recycling, rubber, waste

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Authors: M. Al-Farttoosi, M. Y. Rafiq, J. Summerscales, C. Williams

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Many buildings and bridges are damaged due to impact loading, explosions, terrorist attacks and wars. Most of the damaged structures members such as beams, columns and slabs are not totally failed and it can be repaired. Nowadays, carbon fibre reinforced polymer CFRP has been wildly used in strengthening and retrofitting the structures members. CFRP can rector the load carrying capacity of the damaged structures members to make them serviceable. An experimental investigation was conducted to investigate the impact behaviour of the damaged beams repaired with CFRP. The tested beams had different degrees of damage and near surface mounted technique NSM was used to install the CFRP. A heavy drop weight impact test machine was used to conduct the experimental work. The study investigated the impact strength, stiffness, cracks and deflection of the CFRP repaired beams. The results show that CFRP significantly increased the impact resistance of the damaged beams. CFRP increased the damaged beams stiffness and reduced the deflection. The results showed that the NSM technique is more effective in repairing beams and preventing the debonding of the CFRP.

Keywords: damaged, concrete, impact, repaired

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Authors: Adel M. Belal, Sameh Abu El-Soud, Mariam Farid

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This study presents the effect of reinforcement inclusions (fibers-geogrids) on fine sand bearing capacity under strip footings. Experimental model tests were carried out using a rectangular plates [(10cm x 38 cm), (7.5 cm x 38 cm), and (12.5 cm x 38 cm)] with a geogrids and randomly reinforced fibers. The width and depth of the geogrid were varied to determine their effects on the engineering properties of treated poorly graded fine sand. Laboratory model test results for the ultimate stresses and the settlement of a rigid strip foundation supported by single and multi-layered fiber-geogrid-reinforced sand are presented. The number of layers of geogrid was varied between 1 to 4. The effect of the first geogrid reinforcement depth, the spacing between the reinforcement and its length on the bearing capacity is investigated by experimental program. Results show that the use of flexible random fibers with a content of 0.125% by weight of the treated sand dunes, with 3 geogrid reinforcement layers, u/B= 0.25 and L/B=7.5, has a significant increase in the bearing capacity of the proposed system.

Keywords: earth reinforcement, geogrid, random fiber, reinforced soil

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Authors: Stephen Akong Takim

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This study focused on the optimization of the flexural strength of bio-composite samples of palm kernel, whelks, clams, periwinkles shells and bamboo fiber reinforced with resin for engineering applications. The aim of the study was to formulate different samples of bio-composite reinforced with resin for engineering applications and to evaluate the flexural strength of the fabricated composite. The hand lay-up technique was used for the composites produced by incorporating different percentage compositions of the shells/fiber (10%, 15%, 20%, 25% and 30%) into varied proportions of epoxy resin and catalyst. The cured samples, after 24 hours, were subjected to tensile, impact, flexural and water absorption tests. The experiments were conducted using the Taguchi optimization method L25 (5x5) with five design parameters and five level combinations in Minitab 18 statistical software. The results showed that the average value of flexural was 114.87MPa when compared to the unreinforced 72.33MPa bio-composite. The study recommended that agricultural waste, like palm kernel shells, whelk shells, clams, periwinkle shells and bamboo fiber, should be converted into important engineering applications.

Keywords: bio-composite, resin, palm kernel shells, welk shells, periwinkle shells, bamboo fiber, Taguchi techniques and engineering application

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Authors: Velázquez Alejandro, Pradhan Sujan, Yoon Rokhyun, Sanada Yasushi

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The utilization of new materials as an alternative solution to decrease the environmental impact of the construction industry has been gaining more relevance in the architectural design and construction industry. One such material is cross-laminated timber (CLT), an engineered timber solution that excels for its faster construction times, workability, lightweight, and capacity for carbon storage. This material is usually used alone for the entire structure or combined with steel frames, but a hybrid with reinforced concrete (RC) is rarer. Since RC is one of the most used materials worldwide, a hybrid with CLT would allow further utilization of the latter, and in the process, it would help reduce the environmental impact of RC construction to achieve a sustainable society, but first, the structural performance of such hybrids must be understood. This paper focuses on proposing a model to predict the seismic performance of RC frames with CLT panels as infills. A series of static horizontal cyclic loading experiments were conducted on two 40% scale specimens of reinforced concrete frames with and without CLT panels at Osaka University, Japan. An analytical model was created to simulate the seismic performance of the RC frame with CLT infill based on the experimental results. The proposed model was verified by comparing the experimental and analytical results, showing that the load-deformation relationship and the failure mechanism agreed well with limited error. Hence, the proposed analytical model can be implemented for the seismic performance evaluation of the RC frames with CLT infill.

Keywords: analytical model, multi spring, performance evaluation, reinforced concrete, rocking mechanism, wooden wall

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Authors: Akaki Qatamidze

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Implementation of the project will be a step forward in terms of reliability in Georgia and the improvement of the construction and the development of construction. Completion of the project is expected to result in a complete knowledge, which is expressed in concrete and stone structures of assessing the technical condition of the processing. This method is based on a detailed examination of the structure, in order to establish the injuries and the elimination of the possibility of changing the structural scheme of the new requirements and architectural preservationists. Reinforced concrete and stone structures research project carried out in a systematic analysis of the important approach is to optimize the process of research and development of new knowledge in the neighboring areas. In addition, the problem of physical and mathematical models of rational consent, the main pillar of the physical (in-situ) data and mathematical calculation models and physical experiments are used only for the calculation model specification and verification. Reinforced concrete and stone construction defects and failures the causes of the proposed research to enhance the effectiveness of their maximum automation capabilities and expenditure of resources to reduce the recommended system analysis of the methodological concept-based approach, as modern science and technology major particularity of one, it will allow all family structures to be identified for the same work stages and procedures, which makes it possible to exclude subjectivity and addresses the problem of the optimal direction. It discussed the methodology of the project and to establish a major step forward in the construction trades and practical assistance to engineers, supervisors, and technical experts in the construction of the settlement of the problem.

Keywords: building, reinforced concrete, expertise, stone structures

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Authors: Sriram Venkatesh, V. Murali Mohan, T. V. Karthikeyan

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The main advantage of multi-directionally reinforced composites is the freedom to orient selected fibre types and hence derives the benefits of varying fibre volume fractions and there by accommodate the design loads of the final structure of composites. This technology provides the means to produce tailored composites with desired properties. Due to the high level of fibre integrity with through thickness reinforcement those composites are expected to exhibit superior load bearing characteristics with capability to carry load even after noticeable and apparent fracture. However a survey of published literature indicates inadequacy in the design and test data base for the complete characterization of the multidirectional composites. In this paper the research objective is focused on the development and testing of 4-D orthogonal composites with different preform configurations and resin systems. A preform is the skeleton 4D reinforced composite other than the matrix. In 4-D preforms fibre bundles are oriented in three directions at 1200 with respect to each other and they are on orthogonal plane with the fibre in 4th direction. This paper addresses the various types of 4-D composite manufacturing processes and the mechanical test methods followed for the material characterization. A composite analysis is also made, experiments on course and fine woven preforms are conducted and the findings of test results are discussed in this paper. The interpretations of the test results reveal several useful and interesting features. This should pave the way for more widespread use of the perform configurations for allied applications.

Keywords: multi-directionally reinforced composites, 4-D orthogonal preform, course weave, fine weave, fibre bundle spools, unit cell, fibre architecture, fibre volume fraction, fibre distribution

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Authors: Priyankar P. Deka, Sutanu Samanta

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This paper describes the development of new class of epoxy based hybrid composites reinforced with jute and filled with rice husk flour. Rice husk flour is added in 0%, 1%, 3%, 5% by weight. Epoxy resin and triethylene tetramine (T.E.T.A) is used as matrix and hardener respectively. It investigates the mechanical properties of the composites and a comparison is done for monolithic jute composite and the filled ones. The specimens are prepared according to the ASTM standards and experimentation is carried out using INSTRON 8801. The result shows that with the increase of filler percentage the tensile properties increases but compressive and flexural properties decreases.

Keywords: jute, mechanical characterization, natural fiber, rice husk

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Authors: Billy Angel B. Bayot, Hubert Clyde Z. Guillermo, Daniela Eve Margaret S. Olano, Lian Angeli Kaye E. Suarez

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A utilization of Nipa palm fibers (Nypa fruticans) and Asian green mussel shells (Perna viridis) as additive materials in making fiber-reinforced concrete was carried out. The researchers collected Asian green mussel shells and Nipa palm fibers as additive materials in the production of fiber-reinforced concrete and were used to make 3 Setups containing 20g, 15g, and 10g of Nipa palm fiber varying to 10g, 20g, 30g of Asian green mussel shell powder and a traditional concrete with respect to curing period 7, 14, and 28 days. The concrete blocks were delivered to the UP Institute of Building Materials and Structures Laboratory (CoMSLab) following each curing test in order to evaluate their compressive strength. Researchers employed a Two-Way Analysis of Variance (ANOVA) and determined that curing days, concrete mixture, and the combined curing days with concrete have an effect on the compressive strength of concrete. ANOVA results indicating significant differences had been subjected to post hoc analysis using Tukey's HSD. These results then yielded the comparison of each curing time and different concrete mixtures with traditional concrete, which comes to the conclusion that a longer curing period leads to a higher compressive strength and Setup 3 (30g Asian green mussel shell with 10g Nipa palm fiber) has the larger mean compressive strength, making it the best proportion among the fiber-reinforced concrete mixtures and the only proportion that has significant effect to traditional one. As a result, the study concludes that certain curing times and concrete mix proportions of Asian green mussel shell and Nipa palm fiber are critical determinants in determining concrete compressive strength.

Keywords: Asian green mussel shells (Perna viridis), Nipa palm fibers (Nypa fruticans), additives, fiber-reinforced concrete

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Authors: Yu-Zhou Zheng, Wen-Wei Wang

Abstract:

In this paper, a new strengthening technique for reinforced concrete (RC) beams is proposed by combining Basalt Fibre Reinforced Polymer (BFRP) grid and Engineered Cementitious Composites (ECC) as a composite reinforcement layer (CRL). Five RC beams externally bonded with the CRL at the soffit and one control RC beam was tested to investigate their flexural behaviour. The thickness of BFRP grids (i.e., 1mm, 3mm and 5mm) and the sizes of CRL in test program were selected as the test parameters, while the thickness of CRL was fixed approximately at 30mm. The test results showed that there is no debonding of CRL to occur obviously in the strengthened beams. The final failure modes were the concrete crushing or the rupture of BFRP grids, indicating that the proposed technique is effective in suppressing the debonding of externally bonded materials and fully utilizing the material strengths. Compared with the non-strengthened beam, the increments of crack loading for strengthened beams were 58%~97%, 15%~35% for yield loading and 4%~33% for the ultimate loading, respectively. An analytical model is also presented to predict the full-range load-deflection responses of the strengthened beams and validated through comparisons with the test results.

Keywords: basalt fiber-reinforced polymer (BFRP) grid, ECC, RC beams, strengthening

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Authors: Omar A. Farghal

Abstract:

This research aimed to experimentally and analytically investigate the contribution of bonded web carbon fiber reinforced polymer (CFRP) sheets to the shear strength of reinforced concrete (RC) T-beams. Two strengthening techniques using CFRP strips were applied along the shear-span zone: the first one is vertical U-jacket and the later is vertical strips bonded to the beam sides only. Fibers of both U-jacket and side sheets were vertically oriented (θ = 90°). Test results showed that the strengthening technique with U-jacket CFRP sheets improved the shear strength particularly. Three mechanisms of failure were recognized for the tested beams depending upon the end condition of the bonded CFRP sheet. Although the failure mode for the different beams was a brittle one, the strengthened beams provided with U-jacket CFRP sheets showed more or less a ductile behavior at a higher loading level up to a load level just before failure. As a consequence, these beams approved an acceptable enhancement in the structural ductility. Moreover, the obtained results concerning both the strains induced in the CFRP sheets and the maximum loads are used to study the applicability of the analytical models proposed in this study (ACI code) to predict: the nominal shear strength of the strengthened beams.

Keywords: carbon fiber reinforced polymer, wrapping, ductility, shear strengthening

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Authors: Sara Honarparast, Omar Chaallal

Abstract:

Reinforced concrete (RC) coupled shear walls (CSWs) are very effective structural systems in resisting lateral loads due to winds and earthquakes and are particularly used in medium- to high-rise RC buildings. However, most of existing old RC structures were designed for gravity loads or lateral loads well below the loads specified in the current modern seismic international codes. These structures may behave in non-ductile manner due to poorly designed joints, insufficient shear reinforcement and inadequate anchorage length of the reinforcing bars. This has been the main impetus to investigate an appropriate strengthening method to address or attenuate the deficiencies of these structures. The objective of this paper is to twofold: (i) evaluate the seismic performance of existing reinforced concrete coupled shear walls under reversed cyclic loading; and (ii) investigate the seismic performance of RC CSWs strengthened with externally bonded (EB) carbon fiber reinforced polymer (CFRP) sheets. To this end, two CSWs were considered as follows: (a) the first one is representative of old CSWs and therefore was designed according to the 1941 National Building Code of Canada (NBCC, 1941) with conventionally reinforced coupling beams; and (b) the second one, representative of new CSWs, was designed according to modern NBCC 2015 and CSA/A23.3 2014 requirements with diagonally reinforced coupling beam. Both CSWs were simulated using ANSYS software. Nonlinear behavior of concrete is modeled using multilinear isotropic hardening through a multilinear stress strain curve. The elastic-perfectly plastic stress-strain curve is used to simulate the steel material. Bond stress–slip is modeled between concrete and steel reinforcement in conventional coupling beam rather than considering perfect bond to better represent the slip of the steel bars observed in the coupling beams of these CSWs. The old-designed CSW was strengthened using CFRP sheets bonded to the concrete substrate and the interface was modeled using an adhesive layer. The behavior of CFRP material is considered linear elastic up to failure. After simulating the loading and boundary conditions, the specimens are analyzed under reversed cyclic loading. The comparison of results obtained for the two unstrengthened CSWs and the one retrofitted with EB CFRP sheets reveals that the strengthening method improves the seismic performance in terms of strength, ductility, and energy dissipation capacity.

Keywords: carbon fiber reinforced polymer, coupled shear wall, coupling beam, finite element analysis, modern code, old code, strengthening

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Authors: Bingjie Wang, Qianqian Qang, Nan Lu, Xiubing Liang, Baolong Shen

Abstract:

Novel composites of HfNbTaTiZrV refractory high-entropy alloy (RHEA) reinforced with 0-5 vol.% Al₂O₃ particles have been synthesized by vacuum arc melting. The microstructure evolution, compressive mechanical properties at room and elevated temperatures, as well as strengthening mechanism of the composites, are analyzed. The HfNbTaTiZrV RHEA reinforced with 4 vol.% Al₂O₃ displays excellent phase stability at elevated temperatures. A superior compressive yield strength of 2700 MPa at room temperature, 1392 MPa at 800 °C, and 693 MPa at 1000 °C has been obtained for this composite. The improved yield strength results from multiple strengthening mechanisms caused by Al₂O₃ addition, including interstitial strengthening, grain boundary strengthening, and dispersion strengthening. Besides, the effects of interstitial strengthening increase with the temperature and is the main strengthening mechanism at elevated temperatures. These findings not only promote the development of oxide-reinforced RHEAs for challenging engineering applications but also provide guidelines for the design of light refractory materials with multiple strengthening mechanisms.

Keywords: Al₂O₃-reinforcement, HfNbTaTiZrV, refractory high-entropy alloy, interstitial strengthening

Procedia PDF Downloads 115