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2007 research outputs found
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Sensor Layout Design for Structural Health Monitoring
No full textThis study investigates the enhancement of optimal sensor placement (OSP) algorithms by incorporating modal reduction constraints and developing combined techniques. The primary goal is to optimize sensor placement for structural health monitoring (SHM), thereby improving the efficiency of information acquisition within practical constraints. The proposed methodology utilizes iterative elimination and combined criteria to evaluate various sensor configurations. Numerical experiments demonstrate distinct sensor layouts derived from diverse algorithmic approaches. The study's novel contributions include the integration of modal strain energy, effective independence (EI), and modal assurance criterion (MAC) techniques into a unified framework, enhancing adaptability to a wide range of SHM scenarios. Doi: 10.28991/CEJ-2024-010-12-011 Full Text: PD
Optionally Reinforced Columns Under Simulated Seismic and Time Varying Axial Loads: Advanced HYLSER-2 Testing
No full textSteel- and composite-reinforced columns (SRC and CRC columns) provide alternative solutions for common and harsh environments. Although extensive research has been conducted on these columns, direct comparative studies of SRC and CRC columns under seismic conditions, with consistent testing and realistic load simulations, remain limited. This study examined the nonlinear seismic responses of nine ordinary steel-reinforced concrete column models constructed alternatively with normal-strength and high-strength concretes under simulated earthquakes and time-varying axial loads. A developed advanced HYLSER-2 seismic testing system was employed to conduct seismic tests. Spiral transversal reinforcement with pitches of 6.0 and 9.0 cm was used to explore the effects of concrete confinement. The HYLSER-2 seismic tests, conducted under various interactively simulated earthquake intensities and time-varying axial loads, yielded crucial experimental results. Additionally, an extensive complementary analytical study was conducted to provide comparative insights between steel-reinforced columns (SRC) and composite-reinforced columns (CRC) with novel glass fiber-reinforced (GFRP) bars. The analytical study was conducted using experimentally proven advanced nonlinear analytical micromodels. The analytical results highlight the hysteretic behavior of columns reinforced with ordinary steel and novel GFRP reinforcing bars under the simulated combined effects of reversed cyclic bending and time-varying axial loads. The findings form a critical basis for advancing seismic design strategies for SRC and CRC columns exposed to strong earthquakes and high-time variations in axial loads. Doi: 10.28991/CEJ-2024-010-10-09 Full Text: PD
Study of Reversible Nozzle Apparatuses Using Euler Methodology and CFD Technologies
No full textThis research aims to study multiflow nozzle apparatuses designed to control the thrust vector within a full geometric sphere when the deflection angle of the thrust vector can vary in the range from +180 °to -180 °in any direction. The distribution of the working gas energy was considered as exemplified by a reversible nozzle apparatus with two outlet channels. It was shown that when using wedge-shaped diaphragms, the critical section area can be regulated while maintaining a constant pressure and flow rate of the working gas entering the inlet of the multiflow nozzle. In this case, the mass flow rate of the gas and jet thrust in each outlet channel change in direct proportion to the linear displacement of the diaphragm. Known conical diaphragms do not provide these results. To create promising control systems and train designers, it is proposed to use the Euler methodology and CFD technologies more widely based on the philosophy of technology. In the course of the numerical experiments, the options for the thrust cutoff (tailoff) were considered. A scientific basis has been prepared for solving problems with six degrees of freedom in three-dimensional space, considering Euler angles, when controlling the thrust vector within a full geometric sphere. Issues in flight trajectory planning (for example, for an unmanned aerial vehicle) are discussed with regard to new possibilities for extreme maneuvering. Two main areas for the development of scientific research are considered: energy-saving power generation and transportation systems (land, sea, and air). Doi: 10.28991/CEJ-2024-010-11-013 Full Text: PD
Assessment of Mechanical Properties of Corroded Reinforcement in Chloride Environment Based on Corrosion Rate Monitoring
No full textExisting models for the evaluation of mechanical properties of corroded reinforcement, defined as a function of the mean cross-sectional loss or mass loss of the reinforcement, are not suitable in the case of chloride-induced corrosion, which causes irregular corrosion attack with pronounced localized damage”pits, whose geometry and spacing have a major influence on the mechanical properties of the reinforcement. Models that consider the irregularity of damage due to chloride corrosion are efficient, but as with models based on cross-sectional or mass loss, it is necessary to extract corroded rebars from the reinforced-concrete structure, which is a destructive procedure that can only be performed to a limited extent on an in-service building. To fill the above gaps, a new method based on the non-destructive measurement of corrosion parameters is proposed. The corrosion depth determined from the monitoring correlates directly with the remaining mechanical properties of the reinforcement; therefore, it is not necessary to determine the remaining cross-sectional area and geometry of the pits. The proposed models are based on experimental research on reinforced-concrete beam specimens subjected simultaneously to sustained loading and accelerated chloride corrosion in an environmental chamber in order to induce corrosion similar to that on real structures. Doi: 10.28991/CEJ-2024-010-11-02 Full Text: PD
Earthquake Resistance of Masonry-Infilled RC Frames Strengthened with Expanded Metal
No full textThis research aimed to investigate the compressive strength of lightweight concrete walls before and after reinforcement using the expanded metal reinforced with ferrocement jacketing method and to evaluate the performance level of lightweight concrete walls in reinforced concrete rigid frames. Masonry infill walls were tested using seven samples of lightweight concrete with an average size of 600í—600 mm under axial force. The study results were found that in the part of control, non-plastered lightweight concrete wall (CWL) bore an average compressive strength of 2.52 MPa, and plastered lightweight concrete (WPL) bore an average compressive strength of 2.95 MPa. It indicated that plastering on masonry infill walls was able to bear higher impact strength at 1.17 times due to the bonding force of plastering cement at the masonry infill wall. Lightweight concrete walls reinforced with expanded metal, which were able to bear the maximum compressive strength, were lightweight concrete walls reinforced with 1 layer of expanded metal (WPL-E1) that bore the maximum compressive strength capacity, which was equal to 6.40 MPa. When compared with plastered lightweight concrete walls (WPL) samples, masonry infill walls had 2.16 times higher strength capacity. It was shown that reinforcement using the ferrocement technique significantly increased compressive strength capacity. However, in this research, WPL samples, the plastered lightweight concrete walls, were selected as the control samples, and WPL-E1 test samples with the highest compressive strength were used to evaluate the performance level of the reinforced concrete rigid frame. It was found that lightweight concrete walls reinforced with expanded metal were able to bear higher strength at 1.92 and 3.66 times, respectively. When compared to unreinforced masonry infill wall samples and the bare rigid frame, reinforcement with expanded metal effectively was able to increase the strength and stiffness of the reinforced concrete rigid frame. Doi: 10.28991/CEJ-2024-010-12-017 Full Text: PD
Artificial Intelligence Models for Predicting the Compressive Strength of Geopolymer Cements
No full textThe utilization of nanosilica and cellulose nanocrystals (CNCs) in cement geopolymers remains challenged by intricacies and uncertainties regarding their concentration, posing difficulties in the formulation of systematic geopolymer mix designs. This study aims to formulate models based on Artificial Neural Networks (ANN) capable of forecasting the compressive strength of geopolymers through the utilization of experimentally acquired data. Nanosilica was applied at concentrations of 2%–4% and CNCs at 1%–3%. ANN was modeled using MATLAB to predict the compressive strength of the geopolymer. The results indicated an effect of nanosilica and CNCs on the compressive strength of geopolymer at 2%–4% concentration and 1%–3% CNCs. The best ANN was the GDX training function, purelin activation function, LGD and LGDM learning functions, Lr 0.1 and 0.01 at the number of epochs 3812 out of 25000 and 1774 out of 25000, resulting in the best correlation values of 0.994 and 0.959; the lowest RMSE values are 0.022 and 0.110. The results of the ANN model built based on actual data prove that the model is helpful for accurate simulation to predict the compressive strength of geopolymer cement. This study contributes novelty by optimizing the design model for Geopolymer Cements incorporating nanosilica and CNCs. Doi: 10.28991/CEJ-SP2024-010-03 Full Text: PD
Strength Assessment of Stiffened-Panel Structures against Buckling Loads: FE Benchmarking and Analysis
No full textThis research endeavors to examine the effect of stiffener shapes on the structural capacity of stiffened-plate structures, specifically focusing on Tee (T), Angle (L), and Flat (I) stiffened plates. The primary objectives are threefold: firstly, to quantify the critical load values during the buckling phenomenon for T, L, and I stiffened plates; secondly, to assess model deformation upon failure; and thirdly, to investigate whether the buckling behavior of T, L, and I stiffened plates correlates with distinct failure patterns. Employing numerical simulation through the finite element method, this study sheds light on previously unexplored aspects of structural behavior. The findings indicate that angle stiffeners exhibit superior load-bearing performance compared to flat bars. Notably, the research reveals a substantial increase in maximum compressive load by at least 15.90% with Tee bar and 8.25% with angle bar stiffeners when the stiffened panels undergo a 5 mm displacement, presenting a potential avenue for structural enhancement. Additionally, the study demonstrates that T bars outperform in terms of resisting buckling. Noteworthy is the novel approach of examining the combined effect of transverse frame, longitudinal frame, and hull girder under buckling scenarios, a facet not explored in previous research. Furthermore, the utilization of steel S355JR-EN10210 as a material introduces a unique dimension not previously considered in these scenarios. Doi: 10.28991/CEJ-2024-010-04-03 Full Text: PD
Experimental and Numerical Simulation of Effects of High Temperature on RC Frame Infilled with Sandwich Panel
No full textThis study investigated the structural behavior of reinforced concrete (RC) frames infilled with masonry walls and polyurethane (PU) sandwich wall panels at elevated temperatures. This study aims to assess the influence of temperature on the stiffness and load-carrying capacity of infilled frames, optimize the thickness of the sandwich wall panel, and compare the performance of masonry and sandwich infill systems. Analytical investigations were conducted using finite element analysis software (ABAQUS) to simulate the behavior of the frames at elevated temperatures and consider various configurations of skin thickness for PU sandwich panels. Experimental tests were performed to validate the analytical results. The frames were subjected to transient temperature conditions and uniform unit loads to evaluate their response. Experimental tests were conducted on RC frames infilled with masonry and sandwich-wall panels at elevated temperatures. The frames were subjected to static loading, and their deformations and failure modes were observed. The analytical study revealed that an increase in the skin thickness of the sandwich panel improved its temperature resistance, stress-withstanding ability, and displacement. A skin thickness of 0.45 mm was determined to be the optimal choice considering stress levels and economic factors. The infilled frame with the sandwich wall panel exhibited a 19.22% higher initial stiffness than the masonry wall panel in the experimental tests. The ultimate load-carrying capacity decreased by 17.86% in the infilled sandwich wall panel frame compared to the masonry infill system. The study provides valuable insights into the behavior of RC frames infilled with masonry walls and sandwich wall panels under elevated temperatures. The optimized thickness of the PU sandwich panel was determined by balancing the thermal resistance and the structural performance. The infilled frames with sandwich wall panels exhibited enhanced stiffness but slightly reduced ultimate load-carrying capacity compared with the masonry infill. These findings contribute to the understanding of thermal effects on building structures and can aid in the design and construction of more resilient and efficient buildings in the future. Doi: 10.28991/CEJ-2024-010-01-018 Full Text: PD
Turbidity Removal Performance of Selected Natural Coagulants for Water Treatment in Colombian Rural Areas
No full textDespite the recognized efficiency of natural coagulants, their widespread adoption in the water treatment industry remains low. Our study evaluates the effectiveness of three natural coagulants”Moringa Oleifera, Yausa (Abutilon Insigne Planch), and Breadfruit (Artocarpus Altilis)”in reducing water turbidity levels of 40–50 NTU. Among these, two are native plant species potentially applicable in rural Colombian areas, where there are evident disparities in water infrastructure. This research contributes to the development of these coagulants, exploring their integration with existing water treatment methods, determining their optimal concentrations, and efficiencies in turbidity removal. Our findings reveal significant turbidity removal efficiencies: 88.9% for Moringa Oleifera, 83.3% for Yausa, and 67.2% for Breadfruit. These results indicate the feasibility of these agents as sustainable replacements for traditional chemical coagulants, exhibiting a level of effectiveness alike to that observed in Moringa Oleifera. However, challenges in practical implementation and sustainability, covering technical, environmental, economic, and social aspects, are notable obstacles. The aim of this study is to not only demonstrate the effectiveness of these natural coagulants but also to encourage their broader acceptance and integration into sustainable water treatment practices incorporating two unstudied plant species, such as Yausa and Breadfruit, furthering research to overcome existing challenges. Doi: 10.28991/CEJ-2024-010-02-020 Full Text: PD
Asphalt Mix Compressive Stress-Strain Behavior: An Analytical and Experimental Study of Variable Influence
No full textTo address the excessive depletion of natural resources in Indonesia's civil construction sector, there's a rising trend in utilizing plastic waste from packaging, such as beverage bottles and plastic bags, alongside renewable energy sources like Modified Buton Asphalt (MBA). MBA serves as a partial substitute for both fine and coarse natural aggregates and non-renewable energy sources like petroleum bitumen. This study aimed to investigate the effects of incorporating polyethylene terephthalate (PET) and polypropylene (PP) waste as partial substitutes for coarse and fine aggregates through experiments and t-tests. The objective was to determine how the stress-strain behavior of asphalt mixtures formed using MBA changed with the addition of this mixture. Additionally, compressive strength and elastic modulus were calculated under mixed compressive loads. PET and PP plastic waste replaced natural coarse and fine aggregates at three volume percentages: 1%, 2%, and 3%, with a PET:PP ratio of 50%. A manual grater was used to shred PET and PP plastic bottles into shredded plastic waste, which was retained in sieve no. 50 after sieving. The study found that adding PET, PP plastic, and MBA waste enhanced the asphalt mixture's mechanical strength and modified relevant variables, resulting in a more elastic and ductile behavior. Doi: 10.28991/CEJ-2024-010-05-011 Full Text: PD