MULTI‐PHYSICAL MODELLING AND PROTOTYPING OF AN ENERGY HARVESTING SYSTEM INTEGRATED IN A RAILWAY PNEUMATIC SUSPENSION

The aim of this PhD thesis is the investigation of an energy harvesting system to be integrated in a railway pneumatic spring to recovery otherwise wasted energy source from suspension vibration. Exploiting the piezoelectric effect to convert the mechanical energy into an electrical one, the final scope consists on the use of this system to power supply one or more sensors that can give useful information for the monitoring and the diagnostics of vehicle or its subsystems. Starting from the analysis of the energy sources, a multi‐physical approach to the study of an energy harvesting system is proposed to take into account all physics involved in the phenomenon, to make the most of the otherwise wasted energy and to develop a suitable and affordable tool for the design. The project of the energy harvesting device embedded in a railway pneumatic spring has been carried out by means of using a finite element technique and multi‐physics modelling activity. The possibility to combine two energy extraction processes was investigated with the purpose of making the most of the characteristics of the system and maximize the energy recovering. Exploiting commercial piezoelectric transducers, an experimental activity was conducted in two steps. A first mock‐up was built and tested on a shaker to develop the device and to tune the numerical model against experimental evidence. In the second step a fullscale prototype of an air spring for metro application with the EH system was realized. In order to test the full‐scale component, the design of a new test bench was carried out. Finally, the Air spring integrated with the EH device was tested and models validated

MEMS accelerometer: proof of concept for geotechnical engineering testing

Geotechnical engineering materials are inherently variable, which leads to many simplifications when trying to model their behavior. The materials must always be characterized prior to any design work so that the engineer knows which direction he must progress to have a reliable design. Although subsurface characterization techniques and geotechnical design steadily improve, they are by no means infallible. The combination of geotechnical subsurface characterization along with geophysical techniques for improved design and construction monitoring has begun to surface as a viable alternative to the standard techniques in geotechnical engineering. This is important because there is a lack of Quality Control/Quality Assurance during the construction stage of a project, which further compounds the problems inherent from the complexity of the subsurface. Geophysical techniques based on elastic wave propagation provide an excellent combination of characterization and monitoring for the observation of geotechnical engineering projects. Elastic wave propagation provides coverage between traditional boreholes and it helps infer changes in the state of stresses. Unfortunately, sensors for this type of monitoring have typically been expensive, and the use of elastic wave propagation for characterization and monitoring has just begun to become to be implemented. The application of elastic wave tomography needs an inexpensive set of sensors to help justify its inclusion in the broad area of construction monitoring and characterization systems. This set of inexpensive sensors has arrived on the market developed from Miniature Electro-Mechanical Systems (MEMs) technology. This research developed the Analog Devices’ ADXL250 MEMS accelerometer to determine its limitations and its range of applications. In addition, a packaging system developed to allow for a broader range of applications in geotechnical engineering. Once the sensor was fully calibrated, a long-term goal for the research was to utilize the instrument in a laboratory experiment to obtain a tomographic image of the state of stress within a model. While the sensor was utilized in a model in this study, the final reasoning for its use within the model was simply to show its capabilities and areas of application. Simple velocity distributions are given as well as inferences made about the driving factors for these behaviors

Innovations in earthquake risk reduction for resilience: Recent advances and challenges

The Sendai Framework for Disaster Risk Reduction 2015-2030 (SFDRR) highlights the importance of scientific research, supporting the ‘availability and application of science and technology to decision making’ in disaster risk reduction (DRR). Science and technology can play a crucial role in the world’s ability to reduce casualties, physical damage, and interruption to critical infrastructure due to natural hazards and their complex interactions. The SFDRR encourages better access to technological innovations combined with increased DRR investments in developing cost-effective approaches and tackling global challenges. To this aim, it is essential to link multi- and interdisciplinary research and technological innovations with policy and engineering/DRR practice. To share knowledge and promote discussion on recent advances, challenges, and future directions on ‘Innovations in Earthquake Risk Reduction for Resilience’, a group of experts from academia and industry met in London, UK, in July 2019. The workshop focused on both cutting-edge ‘soft’ (e.g., novel modelling methods/frameworks, early warning systems, disaster financing and parametric insurance) and ‘hard’ (e.g., novel structural systems/devices for new structures and retrofitting of existing structures, sensors) risk-reduction strategies for the enhancement of structural and infrastructural earthquake safety and resilience. The workshop highlighted emerging trends and lessons from recent earthquake events and pinpointed critical issues for future research and policy interventions. This paper summarises some of the key aspects identified and discussed during the workshop to inform other researchers worldwide and extend the conversation to a broader audience, with the ultimate aim of driving change in how seismic risk is quantified and mitigated

2020 NASA Technology Taxonomy

This document is an update (new photos used) of the PDF version of the 2020 NASA Technology Taxonomy that will be available to download on the OCT Public Website. The updated 2020 NASA Technology Taxonomy, or "technology dictionary", uses a technology discipline based approach that realigns like-technologies independent of their application within the NASA mission portfolio. This tool is meant to serve as a common technology discipline-based communication tool across the agency and with its partners in other government agencies, academia, industry, and across the world

Direct in-situ evaluation of liquefaction susceptibility

textEarthquake-induced soil liquefaction that occurs within the built environment is responsible for billions of dollars of damage to infrastructure and loss of economic productivity. There is an acute need to accurately predict the risk of soil liquefaction as well as to quantify the effectiveness of soil improvement techniques that are meant to decrease the risk of soil liquefaction. Current methods indirectly measure the risk of soil liquefaction by empirically correlating certain soil characteristics to known instances of surficial evidence of soil liquefaction, but these methods tend to overpredict the risk in sands with silts, to poorly predict instances of soil liquefaction without surface manifestations, and fail to adequately quantify the effectiveness of soil improvement techniques. Direct in-situ evaluation of liquefaction susceptibility was performed at a single site at the Wildlife Liquefaction Array (WLA) in Imperial Valley, California, in March 2012. The project included a CPT sounding, crosshole testing, and liquefaction testing. The liquefaction testing involved the measurement of water pressure and ground particle motion under earthquake-simulating cyclic loading conditions. The objective of this testing technique is to observe the relationship between shear strain in the soil and the resulting generation of excess pore water pressure. This fundamental relationship dictates whether or not a soil will liquefy during an earthquake event. The direct in-situ evaluation of liquefaction susceptibility approach provides a more accurate and comprehensive analysis of the risks of soil liquefaction. It also has the ability to test large-scale soil improvements in-situ, providing researchers an accurate representation of how the improved soil will perform during a real earthquake event. The most important results in this thesis include the identification of the cyclic threshold strain around 0.02% for the WLA sand, which is very similar to results achieved by other researchers (Vucetic and Dobry, 1986, and Cox, 2006) and is a characteristic of liquefiable soils. Another key characteristic is the 440 to 480 ft/sec (134 to 146 m/s) shear wave velocity of the soil, which are well below the upper limit 656 ft/sec (200 m/s) and an indication that the soil is loose enough for soil liquefaction to occur. The third significant point is that the compression wave velocity of the sand is greater than 4,500 ft/sec (1,370 m/s), indicating that it is at least 99.9% saturated and capable of generating large pore water pressure due to cyclic loading. These three conditions (cyclic threshold strain, shear wave velocity, and compression wave velocity) are among the most important parameters for characterizing a soil liquefaction risk and must all be met in order for soil liquefaction to occur.Civil, Architectural, and Environmental Engineerin

1st year EFAST annual report

The present report provides information about the activities conducted during the 1st year of the EFAST project. The first chapter is dedicated to describe the inquiries conducted at the beginning of the project and to briefly summarise the main results. The second chapter is dedicated to the first EFAST workshop where some of the leading scientists in the field of earthquake engineering have met to discuss about the need and the technologies related to earthquake engineering. The third chapter contains a state of the art and future direction in seismic testing and simulation. The final chapter is dedicated to describe the preliminary design of the web portal of the future testing facility.JRC.DG.G.5-European laboratory for structural assessmen

Development, Evaluation and Implementation of Sensor Techniques for Bridges Critical to the National Transportation System

The evolution of structural materials and sensor technology has impacted the bridge industry by improving the robustness of the highway network and providing behavior based condition assessments. During the last decades, conventional materials have been supplemented with state-of-the-art materials (e.g., carbon and fiber based, ultra-high performance concrete, etc.). The evolution of smart or intelligent structures by incorporating systems to quantify performance will continue to revolutionize the bridge industry. While laboratory and field applications have indicated that smart materials are appropriate for bridge applications, additional investigations regarding sensor installation, deployment and data reduction are still needed. The work described herein is a collection of field and laboratory tests in which sensors were applied to verify structural and material behavior and develop smart members for integration as part of a structural health monitoring system for bridge superstructures. Three projects are presented in which new materials and unique structures were evaluated using specialized sensors and monitoring techniques. Two basket-handle arch pedestrian bridges with high-strength steel hanger rods supporting a pre-cast, post-tensioned concrete panel deck system were monitored to prevent deck cracks in the vicinity of the hanger rods. Fiber optic sensors and externally mounted accelerometers were attached to the hanger rods to indirectly determine the tensile forces during incremental construction stages and in service conditions. For the second project, a three-span prestressed concrete (PC) girder, composite deck bridge was monitored and evaluated. One end span consisted of composite FRP deck panels and was compared to the opposite cast-in-place reinforced concrete deck end span. Strategically placed transducers measured strain levels on the PC girders and the FRR panels from controlled live and ambient traffic loadings to determine the degree of composite action, load distribution, and maximum in-service strains. A FRP panel temporary bypass bridge was evaluated as a replacement to typical steel temporary bridges as part of the third project. The research focused on the design, fabrication, construction and load testing of this state-of-the-art bridge. This bridge was instrumented with transducers for measuring deflections and loaded with a static truck at pertinent locations to evaluate its performance. A five year research plan was established to develop a conceptual smart timber bridge made of glued laminated (glulam) stringers and a transverse glulam deck. Both stock and custom fiber optic sensor packages were implemented to quantify the structural response. The first of multiple phases of this national five year plan includes the development of an efficient structural health monitoring system and a smart timber bridge field demonstration. To support these goals, two types of FBG sensors packages were developed, the first evaluated the structural strain response and the second isolated the sensor from mechanical strain for detecting deterioration parameters (e.g., moisture content, corrosion, wood deterioration, etc.). Techniques were developed for embedding and attaching the FBG sensor packages to glulam specimens. Small scale specimens were instrumented with the custom FBG sensor packages and tested under a range of temperature and loading conditions to determine sensor viability. A full scale glulam beam was instrumented with similar FBG sensor packages to demonstrate applicability and evaluate performance at service level proportions. From this work, the following contributions in structural bridge monitoring were added to the state-of-the-art: * Application of FBG sensors and accelerometers to monitor the structural behavior of a bridge during construction. * Applied testing of non-traditional FRP deck panels to validate composite action. * Initial development of a smart timber bridge structural health monitoring system. * Development of FBG sensor packages for implementation in glulam members as part of a smart timber bridge

Air Injection Technique to Mitigate Liquefaction beneath Shallow Foundations

Historical and recent earthquakes often remind the need for taking precautions against earthquake-induced liquefaction damage that structures on shallow foundations can suffer. Air injection technique has the potential to improve the soil supporting new and existing structures. There is, however, little research on its application and performance beneath existing shallow foundations. The aim of this research was to provide a comprehensive view of the air injection technique by conducting well-controlled dynamic centrifuge and 1-g shaking table tests, along with static soil column experiments in the laboratory. Detailed analysis of the test results highlighted that air injection was an effective way of minimising the soil-softening and loss of shear stiffness associated with earthquake-induced liquefaction. A decreasing trend in the magnitude of excess pore pressures and foundation settlements was observed with decreasing degree of saturation. Air injection technique was also found to perform better under increased confining stresses. Injecting air in a controlled manner (e.g. applying low air injection rate and pressure) was shown to be crucial for the safety of foundations. A wider and more uniformly desaturated zone was achieved with increasing air injection pressure, but which concurrently increased the settlements that shallow foundations experienced. It was also found that most of the air could remain entrapped in partially saturated soil under different simulated field conditions for a long period of time, which indicated the long-term reliability of the mitigation accomplished. Particle image velocimetry was utilised to identify deformation mechanisms that develop underneath and in the ground surrounding shallow foundations. It was shown that foundations resting on saturated soil settled excessively. Foundation settlements were predominantly driven by deviatoric strains, and a bearing capacity failure mechanism did form. When air was injected into saturated soil, air reduced the build-up of excess pore pressures as it contracted during dynamic loading but increased soil compressibility. Deviatoric strain-induced deformations significantly reduced, which resulted in much smaller settlements. The observed settlements were principally caused by volumetric strains that arose from increased soil compressibility. Given the depth of liquefaction reduced significantly for air-injected partially saturated soil, a complete bearing capacity failure mechanism could not occur. The lower the degree of saturation, the shallower and more localised the deformations were observed.Ministry of National Education (M.E.B.) of Turke