Genetic differences based on a beef terminal index are reflected in future phenotypic performance differences in commercial beef cattle

peer-reviewedThe increased demand for animal-derived protein and energy for human consumption will have to be achieved through a combination of improved animal genetic merit and better management strategies. The objective of the present study was to quantify whether differences in genetic merit among animals materialised into phenotypic differences in commercial herds. Carcass phenotypes on 156 864 animals from 7301 finishing herds were used, which included carcass weight (kg), carcass conformation score (scale 1 to 15), carcass fat score (scale 1 to 15) at slaughter as well as carcass price. The price per kilogram and the total carcass value that the producer received for the animal at slaughter was also used. A terminal index, calculated in the national genetic evaluations, was obtained for each animal. The index was based on pedigree index for calving performance, feed intake and carcass traits from the national genetic evaluations. Animals were categorised into four terminal index groups on the basis of genetic merit estimates that were derived before the expression of the phenotypic information by the validation animals. The association between terminal index and phenotypic performance at slaughter was undertaken using mixed models; whether the association differed by gender (i.e. young bulls, steers and heifers) or by early life experiences (animals born in a dairy herd or beef herd) was also investigated. The regression coefficient of phenotypic carcass weight, carcass conformation and carcass fat on their respective estimated breeding values (EBVs) was 0.92 kg, 1.08 units and 0.79 units, respectively, which is close to the expectation of one. Relative to animals in the lowest genetic merit group, animals in the highest genetic merit group had, on average, a 38.7 kg heavier carcass, with 2.21 units greater carcass conformation, and 0.82 units less fat. The superior genetic merit animals were, on average, slaughtered 6 days younger than their inferior genetic merit contemporaries. The superior carcass characteristics of the genetically elite animals materialised in carcasses worth €187 more than those of the lowest genetic merit animals. Although the phenotypic difference in carcass traits of animals divergent in terminal index differed statistically by animal gender and early life experience, the detected interactions were generally biologically small. This study clearly indicates that selection on an appropriate terminal index will produce higher performing animals and this was consistent across all production systems investigated

A comparison of earthwork designs for railway transition zones

Railway track transitions are zones where there is an abrupt change in the track-ground structure. They are often the location of rapid track deterioration, which means more frequent track maintenance is needed compared to plain line tracks. With the aim of reducing maintenance, modern transition zone designs use tapered stiffness earthwork profiles to minimise train-track dynamics. However, there has been limited comparison regarding the effect of different tapered profiles on dynamic behaviour. Therefore, this paper's novelty is the investigation of the performance of different earthwork designs in smoothing stiffness transition's considering different types of improvement and also train speed. To do so, first a 3D finite element track model is developed, with support conditions transitioning from an earth embankment onto a concrete bridge. A dynamic moving train load is simulated using a rigid multi-body approach capable of accounting for train-track interaction. The model is used to study the effect of four earthwork solutions with differing stiffness tapers. For each scenario, two different track structure types (ballast and concrete slab) are considered, along with different magnitudes of ground improvement. Lastly, the effects of train speed are explored. It is found tapered earthwork solutions for ballasted tracks show greater dynamic improvement compared to slabs due to their reduced bending stiffness. Further, the more complex improvement geometries such as double trapezoid shapes offer some additional improvement at locations within 3 m of the bridge. However, when considering such tapered stiffness-based earthwork solutions, additional factors such as constructability must also be considered

An Analysis of Dynamics of Retaining Wall Supported Embankments: Towards More Sustainable Railway Designs

Retaining walls are structures used to retain earth materials on a slope. Typically, they are designed for static loads, but for highway and railway infrastructures, vehicle-induced dynamic responses are also relevant. Therefore, retaining wall structures are often designed with a factor of safety that is higher than necessary, because it can be challenging to quantify the magnitude of expected dynamic stresses during the design stage. This unnecessary increase in material usage reduces the sustainability of the infrastructures. To improve railway retaining wall sustainability, this paper presents the results from a field monitoring campaign on a heavy-haul rail line with a retaining wall, studying the dynamics induced in response to 30-ton axle load trains running at speeds of between 5 km/h and 100 km/h. The site comprises an earth embankment supported by a gravity retaining wall, with accelerometers on the sleepers, roadbed surface, and retaining wall, velocity sensors on the roadbed, and strain gauges on the rail web to record wheel–rail forces. The vibration intensities collected from various locations are processed to explore the peak particle velocities, maximum transient vibration values, and one-third octave band spectrums. Two transfer functions define the vibration transmission characteristics and attenuation of vibration amplitude along the propagation path. The long-term dynamic stability of the track formation is studied using dynamic shear strain derived from the effective velocity. The peaks of observed contact forces and vibrations are statistically analyzed to assess the impact of train speed on the dynamic behavior of the infrastructure system. Next, a 3D numerical model expresses the maximum stress and displacements on the roadbed surface as a function of train speed. The model evaluates the earth pressures at rest and vehicle-induced additional earth pressures and horizontal wall movement. The investigation provides new insights into the behavior of railway track retaining walls under train loading, and the field data are freely available for other researchers to download. The findings could facilitate the design of more sustainable retaining walls in the future

Scoping methodology to asses induced vibration by railway traffic in buildings

This work presents a scoping model to predict ground-borne railway vibration levels within buildings considering soil-structure interaction (SSI). It can predict the response of arbitrarily complex buildings in a fraction of the time typically required to analyse a complex SSI problem, and thus provides a practical tool to rapidly analyse the vibration response of numerous structures near railway lines. The tool is designed for use in cases where the ground-borne vibration is known, and thus can be used as model input. Therefore in practice, for the case of a new line, the ground motion can be computed numerically, or alternatively, for the case of new buildings to be constructed near an existing line, it can be recorded directly (e.g. using accelerometers) and used as model input. To achieve these large reductions in computational time, the model discretises the ground-borne vibration in the free field into a frequency range corresponding to the modes that characterize the dynamic building response. After the ground-borne response spectra that corresponds with the incident wave field is estimated, structural vibration levels are computed using modal superposition, thus avoiding intensive soil-structure interaction computations. The model is validated using a SSI problem and by comparing results against a more complex finite element-boundary element model. Finally, the new scoping model is then used to analyse structural-borne vibration. The results show that the scoping model provides a powerful tool for use during the early design stages of a railway system when a large number of structures require analysis

Permeation grouting of low-permeability silty sands with colloidal silica

Permeation grouting is used to fill the voids in soils with particulates for the purpose of improving soil strength. The technique has been predominatly used for cohesionless soils, however due to nanotechnological advancements in colloidal silica, its application to other soil types has more recently gained attention. Given sands with high silt fractions are a common geotechnical deposit, permeation grouting using colloidal silica is potentially an attractive improvement technique, yet has received limited attention. Therefore, this paper seeks to investigate the transport properties of colloidal silica in low-permeability silty sand, in terms of the effective grouting penetration range and peak strength. To this end, permeation injection is applied on low-permeability silty sand in a laboratory setting and then direct shear tests are undertaken. The results indicate colloidal silica concentrations should be greater than 10% to meet water resistance and strength requirements, while lower than 30% to ensure a uniform distribution of grout and adequate penetration. A low injection pressure of between 45 and 55 kPa, and between 65 and 75 kPa, is found to be suitable for permeating 20% and 30% concentrations of colloidal silica, respectively. After 7 days of curing time, silty sand at natural moisture content and treated with a 20% concentration of colloidal silica shows an increase in peak strength of between 58.1% and 78.4%, which increases further with curing time. A 20% concentration of colloidal silica is recommended for treating silty sand with a coefficient of permeability in the range 10−6 m/s, based on both injection range and peak strength after treatment. These findings may guide the practice of permeation grouting for low-permeability soils

Assessment of railway vibrations using an efficient scoping model

Vibration assessments are required for new railroad lines to determine the effect of vibrations on local communities. Low accuracy assessments can significantly increase future project costs in the form of further detailed assessment or unexpected vibration abatement measures. This paper presents a new, high accuracy, initial assessment prediction tool for high speed lines. A key advantage of the new approach is that it is capable of including the effect of soil conditions in its calculation. This is novel because current scoping models ignore soil conditions, despite such characteristics being the most dominant factor in vibration propagation. The model also has zero run times thus allowing for the rapid assessment of vibration levels across rail networks. First, the development of the new tool is outlined. It is founded upon using a fully validated three dimensional finite element model to generate synthetic vibration records for a wide range of soil types. These records are analysed using a machine learning approach to map relationships between soil conditions, train speed and vibration levels. Its performance is tested through the prediction of two independent international vibration metrics on four European high speed lines and it is found to have high prediction accuracy. A key benefit from this increased prediction accuracy is that it potentially reduces the volume of detailed vibration analyses required for a new high speed train line. This avoids costly in-depth studies in the form of field experiments or large numerical models. Therefore the use of the new tool can result in cost savings

Scoping prediction of re-radiated ground-borne noise and vibration near high speed rail lines with variable soils

This paper outlines a vibration prediction tool, ScopeRail, capable of predicting in-door noise and vibration, within structures in close proximity to high speed railway lines. The tool is designed to rapidly predict vibration levels over large track distances, while using historical soil information to increase accuracy. Model results are compared to an alternative, commonly used, scoping model and it is found that ScopeRail offers higher accuracy predictions. This increased accuracy can potentially reduce the cost of vibration environmental impact assessments for new high speed rail lines. To develop the tool, a three-dimensional finite element model is first outlined capable of simulating vibration generation and propagation from high speed rail lines. A vast array of model permutations are computed to assess the effect of each input parameter on absolute ground vibration levels. These relations are analysed using a machine learning approach, resulting in a model that can instantly predict ground vibration levels in the presence of different train speeds and soil profiles. Then a collection of empirical factors are coupled with the model to allow for the prediction of structural vibration and in-door noise in buildings located near high speed lines. Additional factors are also used to enable the prediction of vibrations in the presence of abatement measures (e.g. ballast mats and floating slab tracks) and additional excitation mechanisms (e.g. wheelflats and switches/crossings)

Field testing and analysis of high speed rail vibrations

This paper outlines an experimental analysis of ground-borne vibration levels generated by high speed rail lines on various earthwork profiles (at-grade, embankment, cutting and overpass). It also serves to provide access to a dataset of experimental measurements, freely available for download by other researchers working in the area of railway vibration (e.g. for further investigation and/or the validation of vibration prediction models). First, the work outlines experimental investigations undertaken on the Belgian high speed rail network to investigate the vibration propagation characteristics of three different embankment conditions. The sites consist of a 5.5 m high embankment, an at-grade section and a 7.2 m deep cutting. The soil material properties of each site are determined using a ‘Multichannel Analysis of Surface Waves’ technique and verified using refraction analysis. It is shown that all sites have relatively similar material properties thus enabling a generalised comparison. Vibration levels are measured in three directions, up to 100 m from the track due to three different train types (Eurostar, TGV and Thalys) and then analysed statistically. It is found that contrary to commonly accepted theory, vertical vibrations are not always the most dominant, and that horizontal vibrations should also be considered, particularly at larger offsets. It is also found that the embankment earthworks profile produced the lowest vibration levels and the cutting produced the highest. Furthermore, a low (positive) correlation between train speed and vibration levels was found. A selection of the results can be downloaded from www.davidpconnolly.com

Spectroscopic target selection for the Sloan Digital Sky Survey: The luminous red galaxy sample

We describe the target selection and resulting properties of a spectroscopic sample of luminous red galaxies (LRGs) from the imaging data of the Sloan Digital Sky Survey (SDSS). These galaxies are selected on the basis of color and magnitude to yield a sample of luminous intrinsically red galaxies that extends fainter and farther than the main flux-limited portion of the SDSS galaxy spectroscopic sample. The sample is designed to impose a passively evolving luminosity and rest-frame color cut to a redshift of 0.38. Additional, yet more luminous red galaxies are included to a redshift of ∼0.5. Approximately 12 of these galaxies per square degree are targeted for spectroscopy, so the sample will number over 100,000 with the full survey. SDSS commissioning data indicate that the algorithm efficiently selects luminous (M*g ≈ - 21.4) red galaxies, that the spectroscopic success rate is very high, and that the resulting set of galaxies is approximately volume limited out to z = 0.38. When the SDSS is complete, the LRG spectroscopic sample will fill over 1 h-3 Gpc3 with an approximately homogeneous population of galaxies and will therefore be well suited to studies of large-scale structure and clusters out to z = 0.5