Journal of Materials and Engineering Structures
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316 research outputs found
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Numerical and experimental studies on vibration-based damage detection methods in beam structures
Full text linkVibration-based damage detection (VBDD) methods have emerged as powerful, cost-effective, and non-destructive methods for detecting and assessing damage in structures. These methods utilize the natural dynamics of structures to identify the presence, location, and extent of damage. Analyzing changes in modal parameters such as natural frequencies, mode shapes, and modal curvatures can detect structural anomalies that indicate damage. This paper describes the flexibility matrix method, the modal curvature method, and the gaped smoothing methods and proposes a new method called the square of modal curvature method. Initially, these damage detection methods are studied using a numerical model of a simply supported beam. The results indicate that the square of modal curvature (SMC) method can effectively detect damage using only a few low-frequency modes. The proposed SMC method is further tested using experimental data obtained from a free-free beam model. Two cases are considered: one with experimental vibration data from an intact beam, and the other without. In the absence of data from an intact beam, the SMC method is combined with the Gapped Smoothing Method (GSM). Both test cases yield reliable results
Determine train load and speed based on dynamic displacement results
Full text linkThe load and operational speed of trains on railway bridges play a significant role. In the context of increasing demand for rail transport, accurately determining these parameters not only helps ensure safety but also brings economic benefits and optimizes system efficiency. This research aims to determine the load and speed of trains based on dynamic displacement results obtained from sensors installed on railway bridges. The study was applied on a real urban railway bridge. The dynamic displacement data of the railway bridge under the influence of passing trains is collected using high-sensitivity LVDT sensors. By applying finite element models (FEM) and real-time displacement data analysis combined with optimization algorithms, the estimation of train load and speed is performed. The analysis results show that the estimated load and speed values are relatively accurate compared to reality. This method helps to accurately monitor and manage train load and speed. The research findings will contribute to improving safety, operational efficiency, and provide a solid scientific foundation for enhancing the railway transportation system
Determine cable dynamic parameters from vibration measurement results
Full text linkStructural health monitoring is a particularly important issue for cable-stayed bridges. The main components of a cable-stayed bridge include the main girder, tower, and stay cables. Stay cables act as a support for the girder, helping it have a large span length. Therefore, stay cables are essential parts of cable-stayed bridges and extrados bridges. Determining the parameters of the stay cable is necessary work. Among the parameters of cable-stayed cables, dynamic parameters such as frequency and damping ratio play an important role. This paper presents a method combining the Hilbert transform and Bandpass filter to determine the frequency, damping ratio and logarithmic decrement of the stay cables. The analysis results show the logarithmic decay changes over time during the vibration. Therefore, to estimate the details, it is necessary to divide the data segment before calculating the logarithmic decay. The results of calculating the vibration frequency using the Hilbert transform method are similar to those of calculating the vibration frequency using the FFT method. The calculation results from the proposed method are compared with those of the traditional method and are highly accurate
Parametric study of crack propagation under thermal shock using phase field method
Full text linkThermal shock is a major concern for brittle and quasi-brittle construction materials such as ceramics as it can easily lead to fracture. The complex mechanism and fracture pattern of this phenomenon make its analysis and prediction challenging. The phase-field method in this context is a promising candidate for simulating this phenomenon. By representing a discrete crack with a continuous damage variable that evolves according to its governing equations, the entire fracture process could be captured within the original finite element mesh. In this work, we developed a phase-field thermomechanical fracture model and implemented it into Abaqus software to reproduce literature work on the fracture behavior of ceramic materials subjected to water quenching. Different types of ceramic plates at various temperature conditions were investigated. The obtained results showed good agreement with the published works, validating the model implementation to be applied to further studies
A Study on Dynamic Modulus of Epoxy Asphalt Concrete: Experiment and Modeling
Full text linkEpoxy asphalt concrete (EAC) has been applied as a surface layer for heavy-load pavements and as a coating layer on steel bridge decks in many countries such as Japan, the UK and the US. EAC exhibits several superior properties, including enhanced resistance to rutting and fatigue cracking, compared to conventional asphalt concrete (AC). The dynamic modulus (|E*|) is a key parameter used to evaluate the performance of EAC in flexible pavement structures. This paper presents laboratory experimental results of the dynamic modulus of EAC across a broad range of temperatures and loading frequencies. Based on these results, master curves of |E*| were constructed to investigate viscoelastic properties of EAC mixtures. Moreover, in order to simulate |E*| master curves of EAC, the model “2S2P1D” was chosen because it has been proven to be suitable for all types of asphalt mixtures. The experimental and simulation results of |E*| master curves of EAC mixtures compared with those of polymer modified asphalt concrete (PMAC) showed that EAC have been retained the viscoelastic properties of asphalt materials
Fly ash-cement based concrete for road construction: engineering properties and pavement design
Full text linkThis research investigates various fly ash (FA) levels of 0%, 15%, 25%, and 35% for cement replacement in concrete, specifically for rural roads in southern Vietnam. The slump values of the fresh concrete mixture were kept under 40 mm to maintain workability based on the requirement of rigid pavement. Concrete's mechanical properties, including its elastic modulus, flexural strength, and compressive strength, and the abrasion resistance were examined at three different stages of curing of 7, 28, and 56 days. Results indicated FA may not contribute to strength development as effectively as cement at early stages. However, the strength of concrete achieved the highest value at a 15% FA replacement level at the long-term curing age. The findings indicated that FA could enhance the long-term strength of concrete regarding its flexural and compressive strengths. According to the results of the abrasion resistance test, abrasion loss rises between 3.2 kg/m2 and 4.21 kg/m2 as FA increases. Finally, the calculation results revealed that 15% and 25% of FA replacement for cement can be used in rigid pavement with good performance
The static test of non-embedded pile-board subgrade in deep soft soil of Shanghai-Hangzhou passenger dedicated line
Full text linkThe non-embedded pile-board subgrade (NEPBS) is a new type of roadbed structure widely used in constructing China's high-speed railways. The paper selects the typical section of the NEPBS project of the Shanghai-Hangzhou Passenger Dedicated Line (SHPDL). It establishes an in-situ static load test system to study and analyze the bearing mechanism and applicability of the NEPBS in deep and soft soil areas. The test results show that the NEPBS has good engineering properties; as time changes, the reinforcement internal force of the loading plate and supporting beam is shown clearly; the converted bending moment agrees with the theoretical bending moment, and the plate-soil contact stress is minor. The test results can explain and analyze the theoretical calculation results. The three-way coordination of the pile-board subgrade can effectively improve the bearing capacity of the foundation soil. The deformation of the NEPBS is reasonable. One year after the completion of the roadbed and track structure, the maximum cumulative settlement of the top surface of the loading plate is 3.29mm, which meets the settlement control requirements
Evaluation of the static behavior of cable-stayed bridge with a curved pylon: A case study
Full text linkBridges play an essential role in the transportation system, especially large-span bridges. Interestingly, cable-stayed bridges (CSBs), typical large-span bridges, have been applied worldwide with curved pylons to obtain a high aesthetic. However, the effects of the curved pylon on CSB behavior are complicated compared to the traditional cases, e.g., A and H-shaped pylons. Remarkably, the cable tension and internal forces of the girders and pylons were significantly redistributed due to the curvature of the pylons. This motivates this study to quantitatively address the impact of curved pylons on the static behavior of CSBs. The current work also proposes a suitable strengthening solution using additional horizontal beams for the curved pylon. To achieve these goals, numerical simulation is employed to develop 3D CSB models with curved, H, and A-shaped pylons. Moreover, the cable tension force from the numerical simulation and that obtained by the lift-off measurement method for an actual bridge are compared to demonstrate the reliability of 3D models. Thus, the results of the present study are expected to provide more profound knowledge and valuable insights for the design work of future curved pylon CSBs
Experimental Study of the Behavior of GFRP Reinforced Concrete Corbels
Full text linkLately, there has been a growing use of FRP rebars (fiber reinforced polymer rebars) in structural components. To understand the complex behavior of these structures under loading, experimental studies are necessary. This article presents an experimental analysis of four double-sided concrete corbels reinforced with glass fiber-reinforced polymer (GFRP) bars and no web reinforcement, focusing on the effects of longitudinal reinforcement ratios and shear span to effective depth ratios (a/d) on structural performance. Two a/d ratios (0.7 and 1.0) and two values of longitudinal GFRP reinforcement ratios (ρf = 0.56% and ρf = 0.87%) were tested to compare the shear behavior of the corbel specimens. The failure modes, stiffness, load-displacement curves, and diagonal strut mechanism are discussed. The results reveal that the splitting mode of failure and the diagonal strut mechanism become dominant once inclined cracks appear. While both the a/d ratio and GFRP reinforcement ratio influence the behavior of GFRP-reinforced concrete corbels, the a/d ratio has a more pronounced effect on shear resistance, whereas the GFRP reinforcement ratio has a lesser impact on shear strength. Additionally, the ACI 440.1R-15 guidelines for predicting the shear strength of GFRP-reinforced concrete corbels were found to provide overly conservative estimates
An efficient surrogate model for building energy consumption estimation considering global warming scenario: a case study in Tra Vinh
Full text linkClimate change has emerged as a global challenge, profoundly affecting various sectors, including building energy. Rising temperatures lead to an increase in energy requirements, and the choice of building materials and orientation influences a building's energy efficiency. This paper aims to build a surrogate model for predicting energy demand through building materials. A case study of a two-storey residential house in Tra Vinh is conducted based on the RCP4.5 climate change scenario for 2050. Firstly, training datasets are generated under the assumed global warming scenario RCP4.5, considering various materials for walls and ceiling slabs. Then, a machine learning model is developed to forecast building energy consumption, with the number of hidden nodes, hidden layers, and training algorithm optimized based on a root mean squared error objective function. Additionally, building orientations are analyzed concerning the movement of the sun. The findings demonstrate the simplicity, efficacy, and application potential of the suggested approach in enhancing the efficiency of building energy analysis, offering valuable insights for sustainable building practices in the face of future climate change