Trang: 764-774 Nguyen Thi Yen Lien, Than Thi Hai YenTóm tắtThe lack of country-specific greenhouse gas (GHG) emission factors vehicles in Vietnam makes the emissions inventory in the transport sector more difficult. This study developed the country-specific GHG emission factor in terms of CO2 equivalent for motorcycles (MCs) in Hanoi to overcome the above impediment. The real-world driving data, instantaneous speed versus time, were collected on the 30 road routes in Hanoi using a GPS device. A filtering process of nine-step was designed to repair misleading speed values and denoise signals before entering the International Vehicle Emissions (IVE) model. The typical GHG emission factor for the MC fleet in Hanoi was approximately 90.83 g/km. This study also found a remarkable difference in the MC’s specific power-related bins distribution between the real-world driving characteristics of the MC in Hanoi and the ones of the World Motorcycle Test Cycle. This contributes to reconfirming the necessity of developing the GHG emission factor based on the very real-world driving data of Vietnam
Detection of bearing faults based on band-pass filters and Fourier interpolation of the load torque
Trang: 775-789 Van Trang Phung, Thanh Lich NguyenTóm tắtBearing faults are widely found in mechatronics systems especially those that are required to work with unbalance loads. A highly reliable mechatronics system requires high quality bearings and/or effective bearing fault diagnostic procedure. This paper deals with the detection of rolling bearing faults based on band-pass filters and Fourier interpolation of the load torque. The reference torque, which is the output of the speed controller, is considered to be an approximation of the load torque. The reference torque is band-pass filtered and then interpolated in terms of Fourier series by using a sliding window method. The Fourier coefficients associated with a healthy bearing are served as a baseline and are compared with faulty lines corresponding to faulty bearings to detect the presence of a bearing failure. The proposed diagnostic method can be conducted online and does not require any additional sensors. Furthermore, the proposed method is able to detect single-point defects whose faulty levels are located at level C of the ISO 10816 Part 3. A mechatronic system equipped with artificial bearing faults is built in the laboratory to verify the effectiveness of the proposed method
An improved version of mode shape based indicator for structural damage identification
Trang: 790-804 Ho Viet Long, Ho Vinh Ha, Vu Van Toan, Ho Xuan BaTóm tắtDamage detection is crucial for the operation and maintenance of an existing bridge or building. A vibration-based method is a popular approach that can be used to identify failures based on changes in the dynamic properties. However, this approach often requires information on both healthy and unhealthy states. In this current study, the structural failure determination is carried out through a damage index based solely on the unhealthy state. A combination of the gapped smooth and modal curvature methods is the core of calculating the proposed indicator. In particular, damage scenarios by means of assumed stiffness reduction, and cuts are investigated. Three categories of beam-like structures consisting of a simply supported beam, a cantilever beam, and a free-free beam are used to validate the applicability of the proposed approach. For comparison purposes, the traditional gapped smooth method is implemented. The location of damage can be identified using only displacement mode shapes. Then, damage quantification at the identified location is estimated using a stochastic optimization process. The promising findings indicate that the proposed approach can enhance the effectiveness of damage identification based on vibration data in the unhealthy state of the structures
Experimental evaluation of shrinkage properties in concrete incorporating coal mine waste rock
Trang: 805-818 Van Minh Nguyen, Thoai Van PhanTóm tắtThis research investigates the properties of concrete utilizing coal mine waste rock (CMWR) as a substitute for river sand. The workability of fresh concrete is assessed through slump tests, revealing a decrease in a slump as the percentage of CMWR replacement increases. The density of the concrete mixtures increased with curing time, and the compressive strength also exhibited an upward trend but with lower values compared to the control concrete when CMWR was used as a replacement. The reduction in compressive strength ranges from 11.4% to 47.6% for CMWR replacement levels of 25% to 100%. The study also examines the influence of climate conditions, including temperature and humidity. Shrinkage deformation tests indicate that CMWR concrete demonstrates higher plastic and dry shrinkage than river sand concrete. CMWR concrete exhibits significantly higher drying shrinkage, attributed to the enhanced water absorption capacity of CMWR particles. These findings provide valuable insights into the performance of concrete incorporating CMWR and propose potential strategies for mitigating its effects. The research outcomes contribute to the knowledge base in the field and offer practical implications for the operation of CMWR in concrete applications
Trang: 819-832 Nguyen Tuan Anh, Le Dang Dung, Nguyen Xuan HuyTóm tắtA finite element model using a multi-fiber approach is proposed in this paper for the analysis of reinforced concrete (RC) members using fiber-reinforced polymer (FRP) reinforcements, with a specific focus on the effect of pure torsion. The proposed model is formulated using a displacement-based approach and a kinematic assumption involving a two-node Timoshenko beam. The compatibility and equilibrium between concrete and FRP materials in the membrane elements are formulated based on a discretization of the cross-section into several areas following its stress state and the principle of the Modified Compression Field Theory. The nonlinear responses of RC elements with FRP bars can be predicted using an appropriate constitutive material law with internal equilibrium of transverse reinforcement and concrete. The pure torsional response is implemented using an enhanced formulation of concrete's tensile behavior, which is based on experimental tests on torsion and the characteristics of FRP materials. The good agreement between the numerical results and experimental data confirms the validity of the proposed model
Mike flood application for forecasting inundation issues: case of duc my bridge area
Trang: 833-849 Doan Thi NoiTóm tắtThe Duc My Bridge is situated approximately 8 km downstream from the Ea Krong Rou reservoir, within the Dinh River system in Khanh Hoa province. Over the years, the region has been experienced heavy rainfall and flooding, leading to elevated flood levels and alterations in the hydraulic regime downstream of the reservoir. These changes are particularly exacerbated by the impacts of climate change. The Ea Krong Rou reservoir belongs to the group of small reservoirs. This is also the type with the highest rate in Vietnam and is more prone to accidents in the rainy season than other types, so the downstream areas are also greatly affected. The article sets up the input parameters for the Dinh River flood plain using the modelling tool MIKE-FLOOD, which integrates the 1-D MIKE-11 model with the 2-D MIKE-21 model. The results show six scenarios (SC1; SC 1C, SC 2, SC 2C, SC3, SC 3C) with very different flood inundation mapping in Duc My Bridge area and other locations. In addition, the paper also determines the degree of concordance between calculated and observed data. Notably, the roughness coefficient is adjusted in the study area to ensure reasonable results
