Fire resistance of concrete members reinforced with fiber reinforced polymer (FRP) rebars is an extremely crucial area that needs to be investigated prior to implementing FRP composite materials in ...buildings and other fire vulnerable structures. This work examines analytically the performance of FRP reinforced concrete beams subjected to high temperatures. Methods for estimating the residual flexural and shear strengths of FRP reinforced concrete beams exposed to fire for a certain duration of time were developed. The proposed methods are based on the assessment of the reduction in the initial strengths of concrete and FRP reinforcement resulting from the high temperatures developed inside the beam. A parametric study was carried out to study the effect of concrete cover, fire exposure time on the FRP temperatures and shear and flexural capacities of reinforced beams. It was found that the FRP temperatures decrease with increasing the concrete cover, and FRP reinforced concrete beams exhibited significant degradation in shear and flexural strengths. Finally, this study recommends a minimum concrete cover for fire resistance of 64 mm (2.5 in.) for FRP reinforced concrete.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper focuses on sustainable cementitious composites in terms of their conductivity, hydration and self-sensing properties, which are key features for smart city infrastructures. Smart cities ...have massive infrastructures that are interconnected, transmitting data and information for health-monitoring and performance optimization. In this regard, having them made of sustainable building materials (concrete) that are also sufficiently conductive, will be a suitable solution for structures’ performance. The studied sustainable cementitious mixtures are made by sea components (sea water and sea sand), which are abundant resources. The primary goal of this study is to improve the mixes’ electrical conductivity and sensitivity. To achieve this goal, milled carbon fibres (MCFs) and chopped carbon fibres (CCFs) in 6 different proportions were added to the cementitious mixes. The experimental study is divided into impedance spectroscopy to study the conductivity and hydration development, and self-sensing properties, conducted on various mix designs. The results show that incorporating sea components improve the electrical conductivity of the mixes by 40-50%. Further improvements were achieved by adding MCF as it shows a remarkable reduction by 60% compared to the plain ss-sw (sea sand and sea water) samples. Adding CCF improved the conductivity even further and resulted in sample’s resistivity as low as 53 Ωcm after 1 year of curing time.
Short glass fiber reinforced composites (SGFRC) are frequently used to manufacture parts with complex surfaces by injection or compression molding. It was found that the length of fibers is often ...reduced during the manufacturing processes. To understand the causes of the change in fiber length, ex-situ 3D CT images are taken from tensile experiments to extract the information of the microstructure of the SGFRC, including fiber length, orientation and breakage. In the calculation of the critical length, the Kelly model is modified to include the effect of the stresses at fiber ends and the mechanical effect of internal pore defects on the composites. It is found that the microscopic interaction of short fibers breaks longer fibers, until they are shorter than the critical length. Through comparisons, it is found that the modified Kelly model is more accurate in predicting critical length of short fibers. In this study, micro-failure modes, such as fiber pulling out, interface debonding, matrix damage and pore destruction, are all characterized by micro-CT and scanning electronic microscope to analyze the complex failure mechanisms. The micro failure modes are mainly attributed to the micro geometric features and mass fraction of short fibers.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Concrete structures undergo an uncontrollable damage process manifesting in the form of cracks due to the coupling of fatigue loading and environmental effects. In order to achieve long-term ...durability and performance, continuous health monitoring systems are needed to make critical decisions regarding operation, maintenance and repairs. Recent advances in nanostructured materials such as carbon nanotubes have opened the door for new smart and advanced sensing materials that could effectively be used in health monitoring of structures where wireless and real time sensing could provide information on damage development. In this paper, carbon nanotube networks were embedded into a cement matrix to develop an in situ wireless and embedded sensor for damage detection in concrete structures. By wirelessly measuring the change in the electrical resistance of the carbon nanotube networks, the progress of damage can be detected and monitored. As a proof of concept, wireless cement-carbon nanotube sensors were embedded into concrete beams and subjected to monotonic and cyclic loading to evaluate the effect of damage on their response. Experimental results showed that the wireless response of the embedded nanotube sensors changes due to the formation of cracks during loading. In addition, the nanotube sensors were able to detect the initiation of damage at an early stage of loading.
The increasing concern over electromagnetic wave (EMW) contamination has led to the emergence of the EMW-absorbing superstructure element. Cementitious composites typically possess poor ...electromagnetic wave reflectivity, but this was improved through 3D printing technology, which offers greater productivity and design flexibility. In this study, a new wave-shaped EMW absorbing superstructure was manufactured using 3D cement printing, and mechanical testing showed a significant improvement in flexural and shearing strength. Molecular dynamic simulation was utilized to investigate the mechanism of the enhanced mechanical properties at the molecular scale. The EMW absorption performance of the printed specimens was analyzed from 1 GHz to 18 GHz through the Naval Research Laboratory (NRL) equipment, exhibiting a significant improvement in reflectance, especially in the low-frequency domain. Based on experimental results, the optimized design of the superstructure was proposed, which possesses an average reflection loss of −25 dB, a peak reflectivity of −37.4 dB, and an absorbing bandwidth of 17 GHz. These findings suggest that the 3D-printed EMW absorber element has great potential for use in minimizing electromagnetic contamination in various applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Mechanical design is one of the essential disciplines in engineering applications, while inspirations of design ideas highly depend on the ability and prior knowledge of engineers or designers. With ...the rapid development of machine learning (ML) techniques, artificial intelligence (AI)‐based design methods are promising tools for the design of advanced engineering systems. So far, there have been some studies of 2D patterns and structural designs based on ML techniques. However, a particular challenge remains in allowing complex 3D mechanical designs using ML techniques. Herein, a novel and experience‐free method to equip ML models with 3D design capabilities by combining a convolutional neuron network (CNN) with a deep convolutional generative adversarial network (DCGAN) is developed. The model directly receives 2D image‐based training data that define the complex 3D structures of a specific machine part. After the training process, an infinite number of new 3D designs can be generated by the proposed model, with their geometric and mechanical properties being accurately predicted at the same time. Moreover, the generated new designs can be fed back to expand the original input datasets for further ML model training and updating.
The applications of image‐based deep learning approaches (convolutional neuron networks and deep convolutional generative adversarial networks) make computers possible to conduct complex 3D mechanical designs and accurately predict their geometric properties. It provides a fundamental for complex designs by artificial intelligence (AI) and reveals the great potential of AI‐based optimization designs.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Fasting during Ramadan involves abstaining from food and drink from dawn to sunset, potentially influencing cognitive functions essential for the intellectual development of the youth. Therefore, ...understanding the effects of fasting on these functions in children/adolescents provides valuable perspectives to enhance education and promote mental well-being. However, studies on children/adolescents in this context are still limited. To evaluate the impact of Ramadan fasting on cognitive functions, including information processing speed, inhibition, decision-making, and auditory attention processes among children and adolescents aged 11 to 15 years. This study was conducted with 24 healthy children/adolescents (aged 12.84 ± 0.69 years). The experimental protocol consisted of two sessions: Before-Ramadan (BR) and at the beginning of the second week of Ramadan (R2). At each session, the boys were randomly tested on simple reaction time (SRT), choice reaction time (CRT), negative priming reaction time (NPRT), and auditory discrimination (P300). The tests were administered and scored by the same person in the different sessions. The study found that Ramadan fasting did not have an effect on various reaction times or on electro-physiological data, including P300 amplitude and latency. The current study, conducted with healthy children/adolescents, indicates that Ramadan fasting had no impact on various reaction times (SRT, CRT, NPRT), suggesting the preservation of information processing speed and decision-making, even in the face of increased task complexity. This is evident, on the one hand, through the maintenance of the ability to react to unexpected events, and, on the other hand, through the mastery of resistance to automatism, thus reflecting the preservation of inhibitory function (NPRT). Regarding P300 data, the absence of changes in latencies and amplitudes suggests that Ramadan fasting did not alter either the evaluation time of auditory stimuli or auditory attention processes.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Characterization and analysis of large quantities of existing soil data represent highly complicated tasks because of the spatial correlation, uncertainty, and complexity of the processes underlying ...soil formation. In this work, three linear kriging (simple kriging, ordinary kriging, and universal kriging) and three nonlinear kriging (indicator kriging, probability kriging, and disjunctive kriging) algorithms are compared to determine which is best suited for the characterization and interpolation of soil data for applications in transportation projects. A spherical model is employed as the experimental variogram to aid the spatial interpolation and cross-validation. The kriged data are subjected to leave-one-out cross-validation. The data used are in both vector and raster format. Statistical measures of correctness (mean prediction error, root-mean-square error, standardized root-mean-square error, average standard error) from the cross-validation are used to compare the kriging algorithms. Using indicator and probability kriging with the vector data set yielded the best results.
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DOBA, FGGLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Eco-friendly concrete becomes research hotspots since concrete production emits 8–10% of the total anthropogenic CO2 emissions worldwide. Industry solid waste modification exhibits great potentials ...on mitigating aggregates depletion and carbon emissions. Coal gangue aggregate (CGA) coated by silica fume manually (CGACM) and in a desiccator (CGACD) are utilised to optimize the 3D printing concrete. Specimens were printed by a 3D printing robotic arm with a 25 mm-diameter nozzle. The compressive strength of CGACM and CGACD increases by 49% and 44% than non-activated series. For splitting tensile strength, the figures are 43% and 36%. The density of activation series decreases over 16% compared with standard sand. However, both surface pretreated methods make negative effects on structure compactness. From the SEM, SiO2 particles filles defects of aggregates, resulting in a denser internal structure and promoting secondary hydration reaction. However, excessive SiO2 particles agglomerated on CGA leads to the lubricant film among particles. These results expand recycle methods for CG and promotes 3D printing technology application on mine.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The rapid increase in energy demand has resulted in more dependence on fossil fuels, which leads to higher CO2 emissions every year. To overcome this problem, shifting from fossil fuel-based energy ...resources to renewable and sustainable ones is essential. One of the new research areas developed in this context is the harvesting of energy from urban infrastructures and, in particular, roads. A large amount of energy in the form of heat or kinetic energy is wasted annually on roads. Recovering these local forms of energy as electricity would improve the energy efficiency of cities. In this review paper, recent developments in the field of energy recovery from roads using solar panels, piezoelectric, thermoelectric and electromagnetic harvesters are discussed along with their efficiency, cost and field implementation. Moreover, new advancements in developing compatible energy storage systems are also discussed and summarised. Based on the review, although all of these systems have the potential of recovering at least a part of the wasted energy, only one of them (the electromagnetic converters) is capable of generating a considerable energy level. In addition, based on the evaluation of the maturity of the technologies, and their cost analyses, more studies are required in order to fill the gap between the current state of the technologies and their full operational form.
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