Slab track optimisation considering dynamic train–track interaction

Slab track is a type of railway track that is frequently used e.g. in high-speed applications as an alternative to ballasted track. Slab track is also well suited on bridges and in tunnels since no ballast is required and the cross-section of tunnels can be reduced. Slab tracks generally have lower maintenance demands than ballasted track. However, if maintenance is required it may be expensive and intrusive. On the other hand, overdimensioning of slab track will lead to high environmental impact and monetary cost. This thesis aims to increase the knowledge and improve the understanding of the dynamic interaction between vehicle and track in order to allow for the optimisation of slab track.To this end, both two-dimensional (2D) and three-dimensional (3D) slab track models, and a transition zone model between slab track and ballasted track, have been developed. These models are used to simulate the vertical dynamic vehicle–track interaction in the time-domain. The computational cost of the simulation is reduced by using a complex-valued modal superposition technique for the finite element model of the track. In the 3D model, both rails are represented by beam elements, while the concrete parts are described using shell or solid elements. The simulations employ a mix of in-house and commercial codes. The influence of different irregularities, e.g. variations in track support conditions and irregularities in longitudinal level, on significant track responses such as wheel–rail contact forces, stresses in the concrete parts and pressure on the foundation is assessed. From Single-Input-Multiple-Output (SIMO) measurements carried out in a full-scale test rig, the 3D model has been calibrated and validated. The developed models have been used to improve the designs of slab track and transition zones. Based on a multi-objective optimisation problem that is solved using a genetic algorithm, the transition zone design has been optimised to minimise the dynamic loads generated due to the stiffness gradient between the two track forms. The slab track design has been optimised to minimise the environmental footprint considering the constraint that the design must pass the static design criteria described in EN\ua016432-2. This design is then employed in the dynamic model where it is shown that there is a further potential for design improvements and related CO2 savings. In particular, there may be possibilities to reduce the thickness of the concrete layers and the amount of concrete between the rails. Finally, a model of reinforced concrete has been implemented and combined with the dynamic model to assess consequences of cracking in the concrete panel and to evaluate stresses in the reinforcement bars

A Proposal for a Three Detector Short-Baseline Neutrino Oscillation Program in the Fermilab Booster Neutrino Beam

A Short-Baseline Neutrino (SBN) physics program of three LAr-TPC detectors located along the Booster Neutrino Beam (BNB) at Fermilab is presented. This new SBN Program will deliver a rich and compelling physics opportunity, including the ability to resolve a class of experimental anomalies in neutrino physics and to perform the most sensitive search to date for sterile neutrinos at the eV mass-scale through both appearance and disappearance oscillation channels. Using data sets of 6.6e20 protons on target (P.O.T.) in the LAr1-ND and ICARUS T600 detectors plus 13.2e20 P.O.T. in the MicroBooNE detector, we estimate that a search for muon neutrino to electron neutrino appearance can be performed with ~5 sigma sensitivity for the LSND allowed (99% C.L.) parameter region. In this proposal for the SBN Program, we describe the physics analysis, the conceptual design of the LAr1-ND detector, the design and refurbishment of the T600 detector, the necessary infrastructure required to execute the program, and a possible reconfiguration of the BNB target and horn system to improve its performance for oscillation searches.Comment: 209 pages, 129 figure

Static, dynamic mechanical and fatigue properties of cement-asphalt mortars

High-speed railway or rail (HSR) is a hot topic all over the contemporary world. And there is a growing tendency towards the application of nonballasted or slab tracks in HSR. Cement-asphalt mortar (CAM), a composite of Portland cement and asphalt emulsion, is widely used as a cushion layer in the two prevailing prefabricated concrete slab tracks of HSR in China, namely CRTS I and CRTS II. After a few years’ operation and service, however, premature cracking has been identified in the CAM layer along part of CRTS I and CRTS II. This is mainly caused by the fatigue of CAMs under repetitive traffic loading, that is, mechanical fatigue. In this research work, therefore, static, dynamic mechanical and most importantly, fatigue properties of the two typical CAMs, namely CAM-I and CAM-II, were investigated. Using a 4-point bending (4PB) test method, static or quasi-static mechanical properties of these two CAMs were studied. Results indicated that the 4PB test method was suitable for characterising their static bending properties in the laboratory, and more reliable results could be obtained, especially on modulus of elasticity, compared to the compression test method which was usually used for formulation design and quality evaluation. However, irrespective of the test methods used, CAM-I and CAM-II were found to be distinctively different in their static mechanical properties and behaviour at room temperature, due to the changes in the microstructures of their binding materials, cement-asphalt binder (CABs), used in CAMs at different A/Cs. The primary functions of CAMs as the cushion layer in CRTS I and II, especially damping, had been demonstrated to be in close relation to their viscoelasticity. Based on the DMA method, the temperature spectra of dynamical modulus and loss factors of CAMs or CABs were obtained to characterise their temperature susceptibility and viscoelasticity, respectively. On the temperature spectrum of CAM-I, the two characteristic temperatures of the asphalt binder, Tg implied to be around -20 °C and TR&B measured to be 48 °C, could be determined, andthese two not only defined the viscoelastic zone for CAM-I and the immediate temperature range for the fatigue tests of CAM-I, but also the two boundaries of service temperatures for CAM-I and CAM-II under traffic loads. The higher A/C caused a decrease in dynamic modulus of CAMs but an increase in their loss factors and temperature susceptibility, and a balance should be considered between them in the future design of new CAMs. For the first time, 4PB fatigue of CAM-I and CAM-II were investigated using two different fatigue test schemes, and the results indicated that, in terms of the fatigue behaviour, the CAM-I can be considered as a cement-modified asphalt mortar whilst CAM-II an asphalt-modified cement mortar. Therefore, it is preferable to use the asphalt mixture-based fatigue test configuration for CAM-I and this fatigue test scheme was an ideal one to be used. Additionally, it was found that low temperature was beneficial to the fatigue life of CAM-I whereas high temperature was detrimental to its fatigue life. On the other hand, the fatigue test configuration of cement-based materials including plain concretes is favourable to use for CAM-II but might not suitable for CAM-II, especially when the influence of the reversal stress, R, or the test temperature was separately considered. Different from plain concrete materials, the reversal stress or the test temperature had a significant impact on the fatigue life of CAM-II. Higher temperature would greatly reduce its fatigue life, and this temperature should not be higher than TR&B of the asphalt binder used. Much longer fatigue life of CAM-II was observed under low temperatures if the same stress, instead of normalised stress level, was applied, and CAM-II was more like plain concretes when temperature fell to around Tg of the asphalt binder

Potential utilization of the NASA/George C. Marshall Space Flight Center in earthquake engineering research

Earthquake engineering research capabilities of the National Aeronautics and Space Administration (NASA) facilities at George C. Marshall Space Flight Center (MSFC), Alabama, were evaluated. The results indicate that the NASA/MSFC facilities and supporting capabilities offer unique opportunities for conducting earthquake engineering research. Specific features that are particularly attractive for large scale static and dynamic testing of natural and man-made structures include the following: large physical dimensions of buildings and test bays; high loading capacity; wide range and large number of test equipment and instrumentation devices; multichannel data acquisition and processing systems; technical expertise for conducting large-scale static and dynamic testing; sophisticated techniques for systems dynamics analysis, simulation, and control; and capability for managing large-size and technologically complex programs. Potential uses of the facilities for near and long term test programs to supplement current earthquake research activities are suggested

Simulating rolling noise on ballasted and slab tracks: vibration, radiation, and pass-by signals

Shifting to rail-bound freight and passenger traffic is key in Europe\u27s strategy towards transport decarbonisation. However, increasing railway traffic can increase environmental noise pollution. Rolling noise is often the dominant noise source. It originates from the interaction of the rough running surfaces of wheel and rail. Predicting rolling noise and performing acoustic optimisation of existing and new tracks requires validated, flexible, and physics-based prediction tools. This is especially relevant for the different designs of ballastless tracks, which are increasingly used for high-speed lines. Therefore, this thesis aims to develop and implement a modelling approach for rolling noise in the time and frequency domain to increase understanding of sound radiation, investigate noise mitigation measures, and allow research of the perception of transients in rolling noise.To achieve this, models for vibration in wheels and several types of ballasted and slab tracks have been implemented using the Waveguide Finite Element method. This method allows an efficient prediction of the track vibration up to high frequencies. Next, models for the sound radiation from wheel and track were implemented using adaptions of the Boundary Element method (BEM), such as the Fourier series BEM and the wavenumber domain BEM.The computational efficiency was addressed in multiple ways. Finally, an approach to simulate the sound produced at a stationary track-side receiver has been developed and implemented based on moving Green\u27s functions. The simulations were largely implemented in in-house Python code. The ballasted and slab track dynamic models have been tuned and compared with measurements on full-scale tracks.The developed models have been used to analyse the vibrations in track and wheel and the acoustic radiation from these vibrations. This allowed the investigation of noise mitigation measures. Further, the necessary complexity of the dynamic track model for predicting rolling noise in time domain was investigated. Two parameter studies were carried out with a focus on track design with lower noise emission. Slab tracks with booted sleepers showed a potential for noise reduction without increasing loads on the track structure. A continuous rail support lowered the radiated sound power at high frequencies. The contributions of different wheel modes to the radiated sound were investigated considering the directivity of each mode, and dominant modes were identified. The established models produce time signals usable for auralisation, which, among others, has the potential to research human perception of transients in rolling noise

Integrated Application of Active Controls (IAAC) technology to an advanced subsonic transport project. ACT/Control/Guidance System study. Volume 2: Appendices

The integrated application of active controls (IAAC) technology to an advanced subsonic transport is reported. Supplementary technical data on the following topics are included: (1) 1990's avionics technology assessment; (2) function criticality assessment; (3) flight deck system for total control and functional features list; (4) criticality and reliability assessment of units; (5) crew procedural function task analysis; and (6) recommendations for simulation mechanization

Design, modelling and testing of a compact piezoelectric transducer for railway track vibration energy harvesting

This is the final version. Available from Elsevier via the DOI in this record. Data will be made available on request.To enable wireless sensor networks to monitor rail infrastructures in real-time, a cost-effective power source is in need. This work presents the design, modelling and testing of a piezo stack energy harvester with frequency up-conversion mechanism for scavenging energy from railway track vibration. The proposed harvester is designed to meet railway track applications’ size, frequency, and stress requirements. A compact design integrating the inertial mass and the piezo stack transducer systems is used to enable the mechanical collision for realising the frequency up-conversion mechanism and ensure the size of the energy harvester is suitable for the limited space on the railway track. The frequency bandwidth of the energy harvester is broadened by utilizing the longitudinal and torsional oscillation of the designed plate springs which enable the system to have two adjacent natural frequencies. The mechanical transformer of the piezo stack transducer system is designed to achieve the required stress level under both the impact force caused by the collision motion and the inertial force generated by the random vibration of the rails. A finite element model (FEM) analysing the free vibration of the piezo stack transducer caused by the frequency up-conversion mechanism is developed to analyse the dynamic characteristics of the coupled system. Lab tests are carried out to validate the proposed FEM and evaluate the impact of different factors such as load resistance, acceleration, initial interval, plate spring, and pulse excitation on power generation. Experimental results show that the energy harvester has two resonant frequencies of 17 Hz and 20 Hz. The frequency up-conversion mechanism can convert this low-frequency vibration into the piezo stack transducer’s high resonant frequency vibration of 94 Hz. A maximum average power of 6.72 mW with a 1-mW-bandwidth of 15 Hz is obtained when actuated at 0.7 RMS g acceleration.Engineering and Physical Sciences Research Council (EPSRC)University of Exete

Aeronautical engineering: A continuing bibliography with indexes, supplement 100

This bibliography lists 295 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System in August 1978