Concrete wave barriers to mitigate ground vibrations induced by railway traffic: a three-dimensional numerical study

Continuous wave barriers are mitigation measures to reduce vibrations induced by railway traffic which have been well studied in technical literature. Nevertheless, there are not many studies about discontinuous concrete wave barriers. By this reason, in this paper continuous and discontinuous concrete wave barriers are studied and compared. With this objective, two theoretical cases with discontinuous barriers have been analysed and the results have been compared with those from both continuous barriers and without barriers cases. The study has been carried out with a dynamic numerical 3D FEM model formulated in the space/time domain, which has previously been validated by authors on the Lisbon-Oporto (Portugal) railway line. The numerical results show the discontinuous barriers with a small separation between axles (less than twice the thickness of the continuous barrier) are an efficient measure in the reduction of vibrations, reaching values of insertion loss of up to 13 dB. So, these could be a very interesting alternative to continuous barriers, in order to conjugate a somewhat lower level of reduction of vibration at a considerable lower cost.

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Study of ground vibrations induced by railway traffic in a 3D FEM model formulated in the time domain: experimental validation

Structure and Infrastructure Engineering ◽

10.1080/15732479.2016.1172649 ◽

2016 ◽

Vol 13 (5) ◽

pp. 652-664 ◽

Cited By ~ 13

Author(s):

Jesús Fernández Ruiz ◽

Pedro Alves Costa ◽

Rui Calçada ◽

Luis E. Medina Rodríguez ◽

Aires Colaço

Keyword(s):

Time Domain ◽

Experimental Validation ◽

Ground Vibrations ◽

3D Fem ◽

Fem Model ◽

Railway Traffic ◽

The Time Domain

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Automated Fracture Mechanics and Fatigue Analyses Based on Three-Dimensional Finite Elements

Journal of Pressure Vessel Technology ◽

10.1115/1.4030085 ◽

2015 ◽

Vol 137 (6) ◽

Cited By ~ 1

Author(s):

Hitoshi Nakamura ◽

Wenwei Gu ◽

Seiichi Tajima ◽

Osamu Hazama

Keyword(s):

Finite Element ◽

Crack Propagation ◽

Three Dimensional ◽

3D Fem ◽

Element Mesh ◽

Fem Model ◽

Steel Pipes ◽

Fatigue Initiation ◽

Propagation Analysis ◽

History Of

This paper describes the structure and application of a software system that automates the fatigue initiation and crack propagation analysis based on finite element method (FEM). The system automatically performs necessary procedures to track propagation history of cracks: insertion of a crack and updating of three-dimensional (3D) finite element mesh in accordance with the crack propagation. The system is equipped with a function to automatically perform fatigue analyses using the stress–strain histories at nodes of a 3D FEM model. Some analyses for several examples were carried out for validation. The important example is the surface crack propagation in steel pipes with residual stress.

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Optimization of a Steam Turbine Blade’s Double-T Root Through Contact Surface Convexity

Volume 8: Microturbines, Turbochargers and Small Turbomachines; Steam Turbines ◽

10.1115/gt2016-56136 ◽

2016 ◽

Author(s):

Johanna Ehlers ◽

Henning Ressing ◽

Wulf-Christof von Karstedt ◽

Daniel Rixen ◽

Mohamed S. Gadala

Keyword(s):

Steam Turbine ◽

Turbine Blade ◽

Contact Surface ◽

Three Dimensional ◽

Peak Stress ◽

Element Model ◽

Von Mises Stress ◽

3D Fem ◽

Fem Model ◽

Von Mises

The turbine blade is one of the most critical components of a steam turbine. The high thermal loads and large centrifugal forces cause extreme stresses on the blade, especially on its root. This paper focuses on improving the double-T root of a turbine blade of the control stage by decreasing the root’s peak equivalent von-Mises stress. An 18% reduction was achieved in the peak stress by changing the convexity of the contact surface between the root and the groove. The equivalent von-Mises stress was determined in a static structural analysis of a three dimensional finite element model (3D FEM-model) using ANSYS Workbench. This numerical model was developed to include one blade and the associated part of the shaft, whereas the complete circle of blades was considered by applying cyclic symmetry. Furthermore, this paper includes a modal analysis comparing the natural frequencies of the initial FEM-model with the frequencies of the optimized one. The results were established by an investigation of the influence of the FEM-model’s parameters, its material properties, thermal effects, and an additional damping wire in the shroud.

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Numerical Modelling of Building Vibrations due to Railway Traffic: Analysis of the Mitigation Capacity of a Wave Barrier

Shock and Vibration ◽

10.1155/2017/4813274 ◽

2017 ◽

Vol 2017 ◽

pp. 1-11 ◽

Cited By ~ 3

Author(s):

Fran Ribes-Llario ◽

Silvia Marzal ◽

Clara Zamorano ◽

Julia Real

Keyword(s):

Building Structure ◽

Railway Transport ◽

Negative Externalities ◽

3D Fem ◽

Fem Model ◽

Foundation Slab ◽

Railway Traffic ◽

Vertical Vibrations ◽

Storey Building

Transmission of train-induced vibrations to buildings located in the vicinity of the track is one of the main negative externalities of railway transport, since both human comfort and the adequate functioning of sensitive equipment may be compromised. In this paper, a 3D FEM model is presented and validated with data from a real track stretch near Barcelona, Spain. Furthermore, a case study is analyzed as an application of the model, in order to evaluate the propagation and transmission of vibrations induced by the passage of a suburban train to a nearby 3-storey building. As a main outcome, vertical vibrations in the foundation slab are found to be maximum in the corners, while horizontal vibrations keep constant along the edges. The propagation within the building structure is also studied, concluding that vibrations invariably increase in their propagation upwards the building. Moreover, the mitigation capacity of a wave barrier acting as a source isolation is assessed by comparing vibration levels registered in several points of the building structure with and without the barrier. In this regard, the wave barrier is found to effectively reduce vibration in both the soil and the structure.

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Numerical Study of the Coupling of Sub-Terahertz Radiation to n-Channel Strained-Silicon MODFETs

Sensors ◽

10.3390/s21030688 ◽

2021 ◽

Vol 21 (3) ◽

pp. 688

Author(s):

Jaime Calvo-Gallego ◽

Juan A. Delgado-Notario ◽

Jesús E. Velázquez-Pérez ◽

Miguel Ferrando-Bataller ◽

Kristel Fobelets ◽

...

Keyword(s):

Electric Field ◽

Continuous Wave ◽

Numerical Study ◽

Three Dimensional ◽

Thz Radiation ◽

Internal Electric Field ◽

Strained Si ◽

Transistor Channel ◽

Electromagnetic Simulations ◽

Bonding Wires

This paper reports on a study of the response of a T-gate strained-Si MODFETs (modulation-doped field-effect transistor) under continuous-wave sub-THz excitation. The sub-THz response was measured using a two-tones solid-state source at 0.15 and 0.30 THz. The device response in the photovoltaic mode was non-resonant, in agreement with the Dyakonov and Shur model for plasma waves detectors. The maximum of the photoresponse was clearly higher under THz illumination at 0.15 THz than at 0.3 THz. A numerical study was conducted using three-dimensional (3D) electromagnetic simulations to delve into the coupling of THz radiation to the channel of the transistor. 3D simulations solving the Maxwell equations using a time-domain solver were performed. Simulations considering the full transistor structure, but without taking into account the bonding wires used to contact the transistor pads in experiments, showed an irrelevant role of the gate length in the coupling of the radiation to the device channel. Simulations, in contradiction with measurements, pointed to a better response at 0.3 THz than under 0.15 THz excitation in terms of the normalized electric field inside the channel. When including four 0.25 mm long bonding wires connected to the contact pads on the transistor, the normalized internal electric field induced along the transistor channel by the 0.15 THz beam was increased in 25 dB, revealing, therefore, the important role played by the bonding wires at this frequency. As a result, the more intense response of the transistor at 0.15 THz than at 0.3 THz experimentally found, must be attributed to the bonding wires.

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A geosynthetic reinforcement solution to prevent the formation of localized sinkholes

Canadian Geotechnical Journal ◽

10.1139/t00-002 ◽

2000 ◽

Vol 37 (5) ◽

pp. 987-999 ◽

Cited By ~ 33

Author(s):

P Villard ◽

J P Gourc ◽

H Giraud

Keyword(s):

Surface Deformation ◽

Numerical Study ◽

Three Dimensional ◽

Full Scale ◽

Geosynthetic Reinforcement ◽

The Road ◽

Railway Line ◽

Collapse Mechanisms ◽

Full Scale Tests ◽

Three Dimensional Finite Element

To prevent the appearance of localized sinkholes under roads and railway lines in areas at risk, a research program testing a geosynthetic reinforcement solution was carried out by a group of laboratories. The aim of the reinforcement is to limit surface deformation after the appearance of a sinkhole by making the surface settlement as compatible as possible with the geometrical safety criteria of the road or railway line until earth filling and repair works can be scheduled. Full-scale tests were carried out on reinforced, instrumented road and railway structures subjected to localized collapse. At the same time, a numerical study was carried out to gain a better understanding of the mechanisms involved (arch effect, membrane effect, and collapse mechanisms). The experimental results of the full-scale tests were analyzed and compared with the results of three-dimensional finite element modeling.Key words: localized sinkhole, karstic cavity, reinforcement, geosynthetic.

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Numerical study on effects of chamber design and multi-inlet on storm geyser

Water Science & Technology ◽

10.2166/wst.2021.061 ◽

2021 ◽

Vol 83 (6) ◽

pp. 1286-1299

Author(s):

Jiachun Liu ◽

Shuangqing Zhang ◽

Biao Huang ◽

David Z. Zhu

Keyword(s):

Peak Pressure ◽

Numerical Study ◽

Three Dimensional ◽

Mitigation Measures ◽

Maximum Pressure ◽

Rapid Urbanization ◽

Inflow Condition ◽

Entrapped Air ◽

Mitigation Methods ◽

Dynamics Models

Abstract Storm geysers increasingly occur in sewer systems under climate change and rapid urbanization. Mitigation measures are in great demand to avoid safety problems. In this study, three-dimensional computational fluid dynamics models of single-inlet and multi-inlet systems were established to investigate geysering induced by rapid filling and assess the effectiveness of potential mitigation methods. The modeling results suggest that increasing the capacity of the downstream pipe before the inflow front reaches the chamber can effectively reduce the maximum geyser pressure. The peak pressure can be significantly mitigated when the chamber size is designed with care and the drop height between the upstream and downstream pipes is reduced. A diversion deflector with air vents and an orifice plate at the riser top end can alleviate the maximum pressure by about 65% with about 75% of the entrapped air being released. The peak pressure during the geyser event in the multi-inlet model is less than that of a single-inlet model under the same total inflow condition, but more water can be released.

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