Search results for: fiber concrete

Authors: M. N. Othman, M. Bukhari, Z. Halim, S. A. Mohammad, K. Khalid

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Sandwich structure composites produced by epoxy core and aluminium skin were developed as potential building materials. Interface bonding between core and skin was controlled by varying kenaf content. Five different weight percentage of kenaf loading ranging from 10 wt% to 50 wt% were employed in the core manufacturing in order to study the mechanical properties of the sandwich composite. Properties of skin aluminium with epoxy were found to be affected by drying time of the adhesive. Mechanical behavior of manufactured sandwich composites in relation with properties of constituent materials was studied. It was found that 30 wt% of kenaf loading contributed to increase the flexural strength and flexural modulus up to 102 MPa and 32 GPa, respectively. Analysis were done on the flatwise and edgewise compression test. For flatwise test, it was found that 30 wt% of fiber loading could withstand maximum force until 250 kN, with compressive strength results at 96.94 MPa. However, at edgewise compression test, the sandwich composite with same fiber loading only can withstand 31 kN of the maximum load with 62 MPa of compressive strength results.

Keywords: Aluminium, kenaf fiber epoxy, sandwich structure composite.

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Authors: Jungbhin You, Taekyun Kim, Jongho Park, Sungnam Hong, Sun-Kyu Park

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Reinforced concrete has been mainly used in construction field because of excellent durability. However, it may lead to reduction of durability and safety due to corrosion of reinforcement steels according to damage of concrete surface. Recently, research of textile is ongoing to complement weakness of reinforced concrete. In previous research, only experiment of longitudinal length were performed. Therefore, in order to investigate the adhesion performance according to the lattice shape and the embedded length, the pull-out test was performed on the roving with parameter of the number of lateral reinforcement, the lateral reinforcement length and the lateral reinforcement spacing. As a result, the number of lateral reinforcement and the lateral reinforcement length did not significantly affect the load variation depending on the adhesion performance, and only the load analysis results according to the reinforcement spacing are affected.

Keywords: Adhesion performance, lateral reinforcement, pull-out test, textile.

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Authors: Cristina S. Decano, Vitaliana U. Malamug, Melissa E. Agulto, Helen F. Gavino

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This study aimed to introduce new natural fiber to be used in the production of geotextile net for mitigation of soil erosion. Fiber extraction from the stalks was the main challenge faced during the processing of stalks to ropes. Thus, an investigation on the extraction procedures of corn (Zea mays L.) stalk under biological and chemical retting was undertaken. Results indicated significant differences among percent fiber yield as affected by the retting methods used with values of 15.07%, 12.97%, 11.60%, and 9.01%, for dew, water, chemical (1 day after harvest and15 days after harvest), respectively, with the corresponding average extracting duration of 70, 82, 89, and 94 minutes. Physical characterization of the developed corn stalk geotextile net resulted to average mass per unit area of 806.25 g/m² and 241% water absorbing capacity. The effect of corn stalk geotextile net in mitigating soil erosion was evaluated in a laboratory experiment for 30^o and 60^o inclinations with three treatments: bare soil (A₁), corn stalk geotextile net (A₂) and combined cornstalk geotextile net and vegetation cover (A₃). Results revealed that treatment A₂ and A₃ significantly decreased sediment yield and an increase in terms of soil loss reduction efficiency. The cost of corn stalk geotextile net is Php 62.41 per square meter.

Keywords: Corn stalk, natural geotextile, retting, soil erosion.

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Authors: B. Navayineya, J. Vaseghi Amiri, M. Alijani Ardeshir

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Hydrodynamic pressures acting on upstream of concrete dams during an earthquake are an important factor in designing and assessing the safety of these structures in Earthquake regions. Due to inherent complexities, assessing exact hydrodynamic pressure is only feasible for problems with simple geometry. In this research, the governing equation of concrete gravity dam reservoirs with effect of fluid viscosity in frequency domain is solved and then compared with that in which viscosity is assumed zero. The results show that viscosity influences the reservoir-s natural frequency. In excitation frequencies near the reservoir's natural frequencies, hydrodynamic pressure has a considerable difference in compare to the results of non-viscose fluid.

Keywords: Closed form solution, concrete dams reservoir, viscosity, dynamic loads, hydrodynamic pressure.

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Authors: Xia Chen, Hua-Quan Yang, Shi-Hua Zhou

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Alkali-active sandstone aggregate was ground by vertical and ball mill into particles with residue over 45 μm less than 12%, and investigations have been launched on particles distribution and characterization of ground sandstone powder, fluidity, heat of hydration, strength as well as hydration products morphology of pastes with incorporation of ground sandstone powder. Results indicated that ground alkali-active sandstone powder with residue over 45 μm less than 8% was easily obtainable, and specific surface area was more sensitive to characterize its fineness with extension of grinding length. Incorporation of sandstone powder resulted in higher water demand and lower strength, advanced hydration of C₃A and C₂S within 3days and refined pore structure. Based on its manufacturing, characteristics and influence on properties of pastes, it was concluded that sandstone powder was a good selection for use in concrete as mineral admixture.

Keywords: Concrete, mineral admixture, hydration, structure.

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Authors: A. Bárbara Cattozatto Fortunato, D. de Lucca Soave, E. Pinheiro de Mello, M. Piasentini Oliva, V. Tavares de Moraes, G. Wolf Lebrão, D. Fernandes Parra, S. Marraccini Giampietri Lebrão

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Due to increasing environmental pressure for biodegradable products, especially in polymeric materials, in order to meet the demands of the biological cycles of the circular economy, new materials have been developed as a sustainability strategy. This study proposes a composite material developed from the biodegradable polymer PLA Ecovio® (polylactic acid - PLA) with natural sisal fibers, where the soybean ester was used as a plasticizer, which can aid in adhesion between the materials and fibers, making the most attractive final composite from an environmental point of view. The composites were obtained by extrusion. The materials tests were produced and submitted to biodegradation tests. Through the biodegradation tests, it can be seen that the biodegradable polymer composition with 5% sisal fiber presented about 12.4% more biodegradability compared to the polymer without fiber addition. It has also been found that the plasticizer was not a compatible with fibers and the polymer. Finally, fibers help to anticipate the decomposition process of the material when subjected to conditions of a landfill. Therefore, its intrinsic properties are not affected during its use, only the biodegradation process begins after its exposure to landfill conditions.

Keywords: Biocomposites, sisal, polylactic acid, PLA.

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Authors: Hee Jae Shin, Lee Ku Kwac, In Pyo Cha, Min Sang Lee, Hyun Kyung Yoon, Hong Gun Kim

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In rapid industrial development, the demand for high-strength and lightweight materials have been increased. Thus, various CFRP (Carbon Fiber Reinforced Plastics) with composite materials are being used. The design variables of CFRP are its lamination direction, order and thickness. Thus, the hardness and strength of CFRP depends much on their design variables. In this paper, the lamination direction of CFRP was used to produce a symmetrical ply [0°/0°, -15°/+15°, -30°/+30°, -45°/+45°, -60°/+60°, -75°/+75° and 90°/90°] and an asymmetrical ply [0°/15°, 0°/30°, 0°/45°, 0°/60° 0°/75° and 0°/90°]. The bending flexure stress of the CFRP specimen was evaluated through a bending test. Its thermal property was measured using an infrared camera. The symmetrical specimen and the asymmetrical specimen were analyzed. The results showed that the asymmetrical specimen increased the bending loads according to the increase in the orientation angle; and from 0°, the symmetrical specimen showed a tendency opposite the asymmetrical tendency because the tensile force of fiber differs at the vertical direction of its load. Also, the infrared camera showed that the thermal property had a trend similar to that of the mechanical properties.

Keywords: Carbon Fiber Reinforced Plastic (CFRP), Bending Test, Infrared Camera, Composite.

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Authors: Rui Qiu, Giles Hardy, Dong Qu, Robert Trengove, Manjree Agarwal, YongLin Ren

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Phytophthora cinnamomi (P. c) is a plant pathogenic oomycete that is capable of damaging plants in commercial production systems and natural ecosystems worldwide. The most common methods for the detection and diagnosis of P. c infection are expensive, elaborate and time consuming. This study was carried out to examine whether species specific and life cycle specific volatile organic compounds (VOCs) can be absorbed by solid-phase microextraction fibers and detected by gas chromatography that are produced by P. c and another oomycete Pythium dissotocum. A headspace solid-phase microextraction (HS-SPME) together with gas chromatography (GC) method was developed and optimized for the identification of the VOCs released by P. c. The optimized parameters included type of fiber, exposure time, desorption temperature and desorption time. Optimization was achieved with the analytes of P. c+V8A and V8A alone. To perform the HS-SPME, six types of fiber were assayed and compared: 7μm Polydimethylsiloxane (PDMS), 100μm Polydimethylsiloxane (PDMS), 50/30μm Divinylbenzene/CarboxenTM/Polydimethylsiloxane DVB/CAR/PDMS), 65μm Polydimethylsiloxane/Divinylbenzene (PDMS/DVB), 85μm Polyacrylate (PA) fibre and 85μm CarboxenTM/ Polydimethylsiloxane (Carboxen™/PDMS). In a comparison of the efficacy of the fibers, the bipolar fiber DVB/CAR/PDMS had a higher extraction efficiency than the other fibers. An exposure time of 16h with DVB/CAR/PDMS fiber in the sample headspace was enough to reach the maximum extraction efficiency. A desorption time of 3min in the GC injector with the desorption temperature of 250°C was enough for the fiber to desorb the compounds of interest. The chromatograms and morphology study confirmed that the VOCs from P. c+V8A had distinct differences from V8A alone, as did different life cycle stages of P. c and different taxa such as Pythium dissotocum. The study proved that P. c has species and life cycle specific VOCs, which in turn demonstrated the feasibility of this method as means of

Keywords: Gas chromatography, headspace solid-phase microextraction, optimization, volatile compounds.

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Authors: Mahmoud A. Mahmoud, Ashraf Osman

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In this study, the different approaches currently followed by design codes to assess the stability of buildings utilizing concrete moment resisting frames structural system are evaluated. For such purpose, a parametric study was performed. It involved analyzing group of concrete moment resisting frames having different slenderness ratios (height/width ratios), designed for different lateral loads to vertical loads ratios and constructed using ordinary reinforced concrete and high strength concrete for stability check and overall buckling using code approaches and computer buckling analysis. The objectives were to examine the influence of such parameters that directly linked to frames’ lateral stiffness on the buildings’ stability and evaluates the code approach in view of buckling analysis results. Based on this study, it was concluded that, the most susceptible buildings to instability and magnification of second order effects are buildings having high aspect ratios (height/width ratio), having low lateral to vertical loads ratio and utilizing construction materials of high strength. In addition, the study showed that the instability limits imposed by codes are mainly mathematical to ensure reliable analysis not a physical ones and that they are in general conservative. Also, it has been shown that the upper limit set by one of the codes that second order moment for structural elements should be limited to 1.4 the first order moment is not justified, instead, the overall story check is more reliable.

Keywords: Buckling, lateral stability, p-delta, second order.

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Authors: T. Häfele, J. Kaspar, M. Vielhaber, W. Calles, J. Griebsch

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The demand for an increasing diversification of the product spectrum associated with the current huge customization desire and subsequently the decreasing unit quantities of each production lot is gaining more and more importance within a great variety of industrial branches, e.g. automotive industry. Nevertheless, traditional product development and production processes (molding, extrusion) are already reaching their limits or fail to address these trends of a flexible and digitized production in view of a product variability up to lot size one. Thus, upcoming innovative production concepts like the additive manufacturing technology basically create new opportunities with regard to extensive potentials in product development (constructive optimization) and manufacturing (economic individualization), but mostly suffer from insufficient strength regarding structural components. Therefore, this contribution presents an innovative technological and procedural conception of a hybrid additive manufacturing process (fiber-reinforced sandwich structures based on selective laser sintering technology) to overcome these current structural weaknesses, and consequently support the design of complex lightweight components.

Keywords: Additive manufacturing, fiber-reinforced plastics, hybrid design, lightweight design.

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Authors: Majid Saaly, Shahriar Tavousi Tafreshi, Mehdi Nazari Afshar

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Most reinforced concrete structures are designed only under heavy loads have large transverse reinforcement spacing values, and therefore suffer severe failure after intense ground movements. The main goal of this paper is to compare the shear- and axial failure of concrete bending frames available in Tehran using Incremental Dynamic Analysis (IDA) under near- and far-field records. For this purpose, IDA of 5, 10, and 15-story concrete structures were done under seven far-fault records and five near-faults records. The results show that in two-dimensional models of short-rise, mid-rise and high-rise reinforced concrete frames located on Type-3 soil, increasing the distance of the transverse reinforcement can increase the maximum inter-story drift ratio values up to 37%. According to the existing results on 5, 10, and 15-story reinforced concrete models located on Type-3 soil, records with characteristics such as fling-step and directivity create maximum drift values between floors more than far-fault earthquakes. The results indicated that in the case of seismic excitation modes under earthquake encompassing directivity or fling-step, the probability values of failure and failure possibility increasing rate values are much smaller than the corresponding values of far-fault earthquakes. However, in near-fault frame records, the probability of exceedance occurs at lower seismic intensities compared to far-fault records.

Keywords: Directivity, fling-step, fragility curve, IDA, inter story drift ratio.v

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Authors: Tomoko Fukuyama, Osamu Senbu

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Prestressed concrete is used a lot in infrastructures such as roads or bridges. However, poor grout filling and PC steel corrosion are currently major issues of prestressed concrete structures. One of the problems with nondestructive corrosion detection of PC steel is a plastic pipe which covers PC steel. The insulative property of pipe makes a nondestructive diagnosis difficult; therefore a practical technology to detect these defects is necessary for the maintenance of infrastructures. The goal of the research is a development of an electrochemical technique which enables to detect internal defects from the surface of prestressed concrete nondestructively. Ideally, the measurements should be conducted from the surface of structural members to diagnose non-destructively. In the present experiment, a prestressed concrete member is simplified as a layered specimen to simulate a current path between an input and an output electrode on a member surface. The specimens which are layered by mortar and the prestressed concrete constitution materials (steel, polyethylene, stainless steel, or galvanized steel plates) were provided to the alternating current impedance measurement. The magnitude of an applied electric field was 0.01-volt or 1-volt, and the frequency range was from 106 Hz to 10-2 Hz. The frequency spectrums of impedance, which relate to charge reactions activated by an electric field, were measured to clarify the effects of the material configurations or the properties. In the civil engineering field, the Nyquist diagram is popular to analyze impedance and it is a good way to grasp electric relaxation using a shape of the plot. However, it is slightly not suitable to figure out an influence of a measurement frequency which is reciprocal of reaction time. Hence, Bode diagram is also applied to describe charge reactions in the present paper. From the experiment results, the alternating current impedance method looks to be applicable to the insulative material measurement and eventually prestressed concrete diagnosis. At the same time, the frequency spectrums of impedance show the difference of the material configuration. This is because the charge mobility reflects the variety of substances and also the measuring frequency of the electric field determines migration length of charges which are under the influence of the electric field. However, it could not distinguish the differences of the material thickness and is inferred the difficulties of prestressed concrete diagnosis to identify the amount of an air void or a layer of corrosion product by the technique.

Keywords: Prestressed concrete, electric charge, impedance, phase shift.

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Authors: Aleš Florian, Lenka Ševelová, Jaroslav Žák

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Formation of tensile cracks in concrete slabs of rigid pavement can be (among others) the initiation point of the other, more serious failures which can ultimately lead to complete degradation of the concrete slab and thus the whole pavement. Two measures can be used for reliability assessment of this phenomenon - the probability of failure and/or the reliability index. Different methods can be used for their calculation. The simple ones are called moment methods and simulation techniques. Two methods - FOSM Method and Simple Random Sampling Method - are verified and their comparison is performed. The influence of information about the probability distribution and the statistical parameters of input variables as well as of the limit state function on the calculated reliability index and failure probability are studied in three points on the lower surface of concrete slabs of the older type of rigid pavement formerly used in the Czech Republic.

Keywords: Failure, pavement, probability, reliability index, simulation, tensile crack.

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Authors: A. P. Singh

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The results reported in this paper are the part of an extensive laboratory investigation undertaken to study the effects of fibre parameters on the permeability and strength characteristics of steel fibre reinforced concrete (SFRC). The effect of varying fibre content and curing age on the water permeability, compressive and split tensile strengths of SFRC was investigated using straight steel fibres having an aspect ratio of 65. Samples containing three different weight fractions of 1.0%, 2.0% and 4.0% were cast and tested for permeability and strength after 7, 14, 28 and 60 days of curing. Plain concrete samples were also cast and tested for reference purposes.

Permeability was observed to decrease significantly with the addition of steel fibres and continued to decrease with increasing fibre content and increasing curing age. An exponential relationship was observed between permeability and compressive and split tensile strengths for SFRC as well as PCC. To evaluate the effect of fibre content on the permeability and strength characteristics, the Analysis of Variance (ANOVA) statistical method was used. An a level (probability of error) of 0.05 was used for ANOVA test. Regression analysis was carried out to develop relationship between permeability, compressive strength and curing age.

Keywords: Permeability, grade of concrete, fibre shape, fibre content, curing age, steady state, Darcy’s law, method of penetration.

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Authors: Elis N. Herliyana , Kunio Tsunoda, Yusuf S. Hadi, Arinana, Dewi A. Natalia

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This study aims to determine the level of resistance of Hevea brasiliensis and Paraserianthes falcataria (synonym: Falcataria molucana) against wood rot fungi Pleurotus ostreatus based on Indonesian standard SNI 01.7207-2006 and Japanese standard JIS K 1571-2004. The variables measured were visual appearance and weight loss percentage of wood based on longitudinal and cross section fiber directions of rubber wood and sengon wood. Measurement of oven dry weight loss of wood samples performed after 12 weeks incubation. Replication performed was 10 times at each treatment combination. The results based on SNI 01.7207-2006, weight loss value of H. brasiliensis and P. falcataria wood with fiber direction longitudinal were 23,12 and 22,25% respectively and cross section were 20,77 and 18,76% respectively, and all were classified to resistance class IV (no resistance). The results based on JIS K 1571-2004, weight loss value of both woods with fiber direction cross section were 10,95 and 14,20% respectively.

Keywords: H. brasiliensis wood, Natural durability, P. falcataria wood, P. ostreatus.

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Authors: M. Fadhil Nuruddin, Samuel Demie, M. Fareed Ahmed, Nasir Shafiq

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The research investigates the effects of super plasticizer and molarity of sodium hydroxide alkaline solution on the workability, microstructure and compressive strength of self compacting geopolymer concrete (SCGC). SCGC is an improved way of concreting execution that does not require compaction and is made by complete elimination of ordinary Portland cement content. The parameters studied were superplasticizer (SP) dosage and molarity of NaOH solution. SCGC were synthesized from low calcium fly ash, activated by combinations of sodium hydroxide and sodium silicate solutions, and by incorporation of superplasticizer for self compactability. The workability properties such as filling ability, passing ability and resistance to segregation were assessed using slump flow, T-50, V-funnel, L-Box and J-ring test methods. It was found that the essential workability requirements for self compactability according to EFNARC were satisfied. Results showed that the workability and compressive strength improved with the increase in superplasticizer dosage. An increase in strength and a decrease in workability of these concrete samples were observed with the increase in molarity of NaOH solution from 8M to 14M. Improvement of interfacial transition zone (ITZ) and micro structure with the increase of SP and increase of concentration from 8M to 12M were also identified.

Keywords: Compressive strength, Fly ash, Geopolymer concrete, Workability

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Authors: V. K. Bansal, M. Kumar, P. P. Bansal, A. Batish

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This paper presents the results of an experimental investigation carried out to evaluate the effects of partial replacement of cement and fine aggregate with industrial waste by-products on concrete strength properties. The Grey Taguchi approach has been used to optimize the mix proportions for desired properties. In this research work, a ternary combination of industrial waste by-products has been used. The experiments have been designed using Taguchi's L9 orthogonal array with four factors having three levels each. The cement was partially replaced by ladle furnace slag (LFS), fly ash (FA) and copper slag (CS) at 10%, 25% and 40% level and fine aggregate (sand) was partially replaced with electric arc furnace slag (EAFS), iron slag (IS) and glass powder (GP) at 20%, 30% and 40% level. Three water to binder ratios, fixed at 0.40, 0.44 and 0.48, were used, and the curing age was fixed at 7, 28 and 90 days. Thus, a series of nine experiments was conducted on the specimens for water to binder ratios of 0.40, 0.44 and 0.48 at 7, 28 and 90 days of the water curing regime. It is evident from the investigations that Grey Taguchi approach for optimization helps in identifying the factors affecting the final outcomes, i.e. compressive strength and split tensile strength of concrete. For the materials and a range of parameters used in this research, the present study has established optimum mixes in terms of strength properties. The best possible levels of mix proportions were determined for maximization through compressive and splitting tensile strength. To verify the results, the optimal mix was produced and tested. The mixture results in higher compressive strength and split tensile strength than other mixes. The compressive strength and split tensile strength of optimal mixtures are also compared with the control concrete mixtures. The results show that compressive strength and split tensile strength of concrete made with partial replacement of cement and fine aggregate is more than control concrete at all ages and w/c ratios. Based on the overall observations, it can be recommended that industrial waste by-products in ternary combinations can effectively be utilized as partial replacements of cement and fine aggregates in all concrete applications.

Keywords: Analysis of variance, ANOVA, compressive strength, concrete, grey Taguchi method, industrial by-products, split tensile strength.

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Authors: F. I. Belheouane, M. Bensaibi

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The seismic feedback experiences in Algeria have shown higher percentage of damages for non-code conforming reinforced concrete (RC) buildings. Furthermore, the vulnerability of these buildings was further aggravated due to presence of many factors (e.g. weak the seismic capacity of these buildings, shorts columns, Pounding effect, etc.). Consequently Seismic risk assessments were carried out on populations of buildings to identify the buildings most likely to undergo losses during an earthquake. The results of such studies are important in the mitigation of losses under future seismic events as they allow strengthening intervention and disaster management plans to be drawn up. Within this paper, the state of the existing structures is assessed using "the vulnerability index" method. This method allows the classification of RC constructions taking into account both, structural and non structural parameters, considered to be ones of the main parameters governing the vulnerability of the structure. Based on seismic feedback from past earthquakes DPM (damage probability matrices) were developed too.

Keywords: Seismic vulnerability, Reinforced concrete buildings, Earthquake, DPM, Algeria.

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Authors: Abbas Vahedian, Rijun Shrestha, Keith Crews

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In recent years, fibre reinforced polymers as applications of strengthening materials have received significant attention by civil engineers and environmentalists because of their excellent characteristics. Currently, these composites have become a mainstream technology for strengthening of infrastructures such as steel, concrete and more recently, timber and masonry structures. However, debonding is identified as the main problem which limit the full utilisation of the FRP material. In this paper, a preliminary analysis of factors affecting bond strength of FRP-to-concrete and timber bonded interface has been conducted. A novel theoretical method through regression analysis has been established to evaluate these factors. Results of proposed model are then assessed with results of pull-out tests and satisfactory comparisons are achieved between measured failure loads (R² = 0.83, P < 0.0001) and the predicted loads (R² = 0.78, P < 0.0001).

Keywords: Debonding, FRP, pull-out test, stepwise regression analysis.

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Authors: A. Dulaimi, H. Al Nageim, F. Ruddock, L. Seton

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This study aims at developing a novel cold asphalt concrete binder course mixture by using Ordinary Portland Cement (OPC) as a replacement for conventional mineral filler (0%-100%) with new by-product material (LJMU-A2) used as a supplementary cementitious material. With this purpose, cold asphalt concrete binder course mixtures with cationic emulsions were studied by means of stiffness modulus whereas water sensitivity was assessed by measuring the stiffness modulus ratio before and after sample conditioning. The results indicate that a substantial enhancement in the stiffness modulus and a considerable improvement of water sensitivity resistance is achieved by adding LJMU-A2 to the cold asphalt mixtures as a supplementary cementitious material. Moreover, the addition of LJMU-A2 to those mixtures leads to a stiffness modulus after 2-day curing compared to that obtained with Portland cement, which occurs after 7-day curing.

Keywords: Binder course, cold mix asphalt, cement, stiffness modulus, water sensitivity.

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Authors: Musa H. Arslan, Murat Ceylan, Tayfun Koyuncu

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In this study, an Artificial Neural Network (ANN) analytical method has been developed for analyzing earthquake performances of the Reinforced Concrete (RC) buildings. 66 RC buildings with four to ten storeys were subjected to performance analysis according to the parameters which are the existing material, loading and geometrical characteristics of the buildings. The selected parameters have been thought to be effective on the performance of RC buildings. In the performance analyses stage of the study, level of performance possible to be shown by these buildings in case of an earthquake was determined on the basis of the 4-grade performance levels specified in Turkish Earthquake Code-2007 (TEC-2007). After obtaining the 4-grade performance level, selected 23 parameters of each building have been matched with the performance level. In this stage, ANN-based fast evaluation algorithm mentioned above made an economic and rapid evaluation of four to ten storey RC buildings. According to the study, the prediction accuracy of ANN has been found about 74%.

Keywords: Artificial neural network, earthquake, performance, reinforced concrete.

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Authors: Na Li

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This paper describes a new measuring algorithm for three-dimensional (3-D) braided composite material .Braided angle is an important parameter of braided composites. The objective of this paper is to present an automatic measuring system. In the paper, the algorithm is performed by using vcµ6.0 language on PC. An advanced filtered algorithm for image of 3-D braided composites material performs has been developed. The procedure is completely automatic and relies on the gray scale information content of the images and their local wavelet transform modulus maxims. Experimental results show that the proposed method is feasible. The algorithm was tested on both carbon-fiber and glass-fiber performs.

Keywords: Three-Dimensional composite material, Mathematical morphology.

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Authors: Ye. B. Utepov, A. S. Tulebekova, A. B. Kazkeyev

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Maturity sensors are used to determine concrete strength by the non-destructive method. The method of placement of the maturity sensors determines their number required for a certain frame of a monolithic building. This paper proposes a cheap prototype of an embedded wireless sensor for monitoring concrete structures, as well as an alternative strategy for placing sensors based on the transitional boundaries of the temperature distribution of concrete curing, which were determined by building a heat map of the temperature distribution, where unknown values are calculated by the method of inverse distance weighing. The developed prototype can simultaneously measure temperature and relative humidity over a smartphone-controlled time interval. It implements a maturity method to assess the in-situ strength of concrete, which is considered an alternative to the traditional shock impulse and compression testing method used in Kazakhstan. The prototype was tested in laboratory and field conditions. The tests were aimed at studying the effect of internal and external temperature and relative humidity on concrete's strength gain. Based on an experimentally poured concrete slab with randomly integrated maturity sensors, it the transition boundaries form elliptical forms were determined. Temperature distribution over the largest diameter of the ellipses was plotted, resulting in correct and inverted parabolas. As a result, the distance between the closest opposite crossing points of the parabolas is accepted as the maximum permissible step for setting the maturity sensors. The proposed placement strategy can be applied to sensors that measure various continuous phenomena such as relative humidity. Prototype testing has also revealed Bluetooth inconvenience due to weak signal and inability to access multiple prototypes simultaneously. For this reason, further prototype upgrades are planned in the future work.

Keywords: Heat map, placement strategy, temperature and relative humidity, wireless embedded sensor.

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Authors: Shrikant Charhate, Gayatri Deshpande

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Permeable pavements have significant benefits like managing runoff, infiltration, and carrying traffic over conventional pavements in terms of sustainability and environmental impact. Some of the countries are using this technique, especially at locations where durability and other parameters are of importance in nature; however, sparse work has been done on this concept. In India, this is yet to be adopted. In this work, the progress in the characterization and development of Permeable Articulated Concrete Blocks (PACB) pavement design is described and discussed with reference to Indian conditions. The experimentation and in-depth analysis was carried out considering conditions like soil erosion, water logging, and dust which are significant challenges caused due to impermeability of pavement. Concrete blocks with size 16.5’’x 6.5’’x 7’’ consisting of arch shape (4’’) at beneath and ½” PVC holes for articulation were casted. These blocks were tested for flexural strength. The articulation process was done with nylon ropes forming series of concrete block system. The total spacing between the blocks was kept about 8 to 10% of total area. The hydraulic testing was carried out by placing the articulated blocks with the combination of layers of soil, geotextile, clean angular aggregate. This was done to see the percentage of seepage through the entire system. The experimental results showed that with the shape of concrete block the flexural strength achieved was beyond the permissible limit. Such blocks with the combination could be very useful innovation in Indian conditions and useful at various locations compared to the traditional blocks as an alternative for long term sustainability.

Keywords: Connections, geotextile, permeable ACB, pavements, stone base.

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Authors: Do-Kyu, Hwang, Ho-Young Kim, Ho-Hyeoung Choi, Gi-Beom Park, Jae-Hoon Lee

Abstract:

Currently there are many use of threaded reinforcing bars in construction fields because those do not need additional screw processing when connecting reinforcing bar by threaded coupler. In this study, reinforced concrete bridge piers using threaded rebar coupler system at the plastic hinge area were tested to evaluate seismic performance. The test results showed that threads of the threaded rebar coupler system could be loosened while under tension-compression cyclic loading because tolerance and rib face angle of a threaded rebar coupler system are greater than that of a conventional ribbed rebar coupler system. As a result, cracks were concentrated just outside of the mechanical coupler and stiffness of reinforced concrete bridge pier decreased. Therefore, it is recommended that connection ratio of mechanical couplers in one section shall be below 50% in order that cracks are not concentrated just outside of the mechanical coupler. Also, reduced stiffness of the specimen should be considered when using the threaded rebar coupler system.

Keywords: Reinforced concrete column, seismic performance, threaded rebar coupler, threaded reinforcing bar.

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Authors: Zhi Zhang, Tao Tang, Guangda Lu, Cheng Qin, Huogen Huang, Shaotao Zheng

Abstract:

High purity hydrogen and the valuable by-product of carbon nanotubes (CNTs) can be produced by the methane catalytic decomposition. The methane conversion and the performance of CNTs were determined by the choices of catalysts and the condition of decomposition reaction. In this paper, Ni/MgO and Ni/O-D (oxidized diamond) catalysts were prepared by wetness impregnation method. The effects of reaction temperature and space velocity of methane on the methane conversion were investigated in a fixed-bed. The surface area, structure and micrography were characterized with BET, XPS, SEM, EDS technology. The results showed that the conversion of methane was above 8% within 150 min (T=500) for 33Ni/O-D catalyst and higher than 25% within 120 min (T=650) for 41Ni/MgO catalyst. The initial conversion increased with the increasing temperature of the decomposition reaction, but their catalytic activities decreased rapidly while at too higher temperature. To decrease the space velocity of methane was propitious to promote the methane conversion, but not favor of the hydrogen yields. The appearance of carbon resulted from the methane decomposition lied on the support type and the condition of catalytic reaction. It presented as fiber shape on the surface of Ni/O-D at the relatively lower temperature such as 500 and 550, but as grain shape stacked on and overlayed on the surface of the metal nickel while at 650. The carbon fiber can form on the Ni/MgO surface at 650 and the diameter of the carbon fiber increased with the decreasing space velocity.

Keywords: methane, catalytic decomposition, hydrogen, carbon nanofiber

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Authors: Ali Kezmane, Said Boukais, Mohand Hamizi

Abstract:

This paper presents an analytical study on the behavior of reinforced concrete walls with rectangular cross section. Several experiments on such walls have been selected to be studied. Database from various experiments were collected and nominal shear wall strengths have been calculated using formulas, such as those of the ACI (American), NZS (New Zealand), Mexican (NTCC), and Wood and Barda equations. Subsequently, nominal shear wall strengths from the formulas were compared with the ultimate shear wall strengths from the database. These formulas vary substantially in functional form and do not account for all variables that affect the response of walls. There is substantial scatter in the predicted values of ultimate shear strength. Two new semi empirical equations are developed using data from tests of 57 walls for transitions walls and 27 for slender walls with the objective of improving the prediction of peak strength of walls with the most possible accurate.

Keywords: Shear strength, reinforced concrete walls, rectangular walls, shear walls, models.

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Authors: Azad A. Mohammed, Gulan B. Hassan

Abstract:

Analytical procedure was carried out in this paper to calculate the ultimate load capacity of reinforced concrete corbels strengthened or repaired externally with CFRP sheets. Strut and tie method and shear friction method proposed earlier for analyzing reinforced concrete corbels were modified to incorporate the effect of external CFRP sheets bonded to the corbel. The points of weakness of any method that lead to an inaccuracy, especially when overestimating test results were checked and discussed. Comparison of prediction with the test data indicates that the ratio of test / calculated ultimate load is 0.82 and 1.17 using strut and tie method and shear friction method, respectively. If the limits of maximum shear stress is followed, the calculated ultimate load capacity using shear friction method was found to underestimates test data considerably.

Keywords: Corbel, Strengthening, Strut and Tie Model, Shear Friction

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Authors: Young-Jun You, Youn-Ju Jeong, Min-Su Park, Du-Ho Lee

Abstract:

Due to a lot of limited conditions, a large box type floating structure is inevitably constructed by connecting many pontoons. When a floating structure is made with concrete, concrete shear key with saw-teeth shape is often used to carry shear force. Match casting for the shear key and precise construction on a sea are very important for making separated two pontoons as one body but those are not easy work and may increase construction time and cost. To solve this problem, one-way shear key is studied in this paper for a connected part where there is some difference between upward and downward shear force. It has only one inclined plane and can resist shear force in one direction. Big shear force is resisted by concrete which forms an inclined plane and small shear force is resisted by steel bar. This system can reduce manufacturing cost of individual pontoon and construction time and cost for constructing a floating structure on a sea. In this paper, the feasibility study about one-way shear key system is performed by comparing with design example.

Keywords: Connection, floating container terminal, pontoon, pre-stressing, shear key.

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Authors: Kalyan Kumar Mandal, Damodar Maity

Abstract:

The degradation of concrete due to various hygrochemo- mechanical actions is inevitable for the structures particularly built to store water. Therefore, it is essential to determine the material properties of dam-like structures due to ageing to predict the behavior of such structures after a certain age. The degraded material properties are calculated by introducing isotropic degradation index. The predicted material properties are used to study the behavior of aged dam at different ages. The dam is modeled by finite elements and displacement and is considered as an unknown variable. The parametric study reveals that the displacement is quite larger for comparatively lower design life of the structure because the degradation of elastic properties depends on the design life of the dam. The stresses in dam cam be unexpectedly large at any age with in the design life. The outcomes of the present study indicate the importance of the consideration ageing effect of concrete exposed to water for the safe design of dam throughout its life time.

Keywords: Hygro-chemo-mechanical, isotropic degradation, finite element method, Koyna earthquake.

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