A Bayesian inverse dynamic approach for impulsive wave loading reconstruction: Theory, laboratory and field application

The measurement of wave forces acting on marine structures is a complicated task, both during physical experiments and, even more so, in the field. Force transducers adopted in laboratory experiments require a minimum level of structural movement, thus violating the main assumption of fully rigid structure and introducing a dynamic response of the system. Sometimes the induced vibrations are so intense that they completely nullify the reliability of the experiments. On-site, it is even more complex, since there are no force transducers of the size and capacity able to measure such massive force intensity acting over the very large domain of a marine structure. To this end, this investigation proposes a Bayesian methodology aimed to remove the undesired effects from the directly (laboratory applications) or indirectly (field applications) measured wave forces. The paper presents three applications of the method: i) a theoretical application on a synthetic signal for which MATLAB® procedures are provided, ii) an experimental application on laboratory data collected during experiments aimed to model broken wave loading on a cylinder upon a shoal and iii) a field application designed to reconstruct the wave force that generated recorded vibrations on the Wolf Rock lighthouse during Hurricane Ophelia. The proposed methodology allows the inclusion of existing information on breaking and broken wave forces through the process-based informative prior distributions, while it also provides the formal framework for uncertainty quantification of the results through the posterior distribution. Notable findings are that the broken wave loading shows similar features for both laboratory and field data. The load time series is characterised by an initial impulsive component constituted by two peaks and followed by a delayed smoother one. The first two peaks are due to the initial impact of the aerated front and to the sudden deceleration of the falling water mass previously upward accelerated by the initial impact. The third, less intense peak, is due to the interaction between the cylinder and remaining water mass carried by the individual wave. Finally, the method allows to properly identify the length of the impulsive loading component. The implications of this length on the use of the impulse theory for the assessment or design of marine structures are discussed

Experimentelle und numerische Modellierung der hydraulischen Stabilität von geotextilen Sandcontainern für Küstenschutzwerke

More versatile materials and innovative solutions are required for the design of new, cost effective shore protection structures as well as for the reinforcement of existing threatened coastal barriers, including dune reinforcement and scour protection. Geotextile Sand Containers (GSC) is a relatively low cost, soft and reversible solution for the above problem with a history of more than 50 years in hydraulic and marine applications. Nevertheless, GSC is still an emerging technology and no proper guidelines are available for the design of GSC-structures on a sound scientific base. This PhD study attempts to evaluate the effect of the most important engineering properties of GSCs on the hydraulic stability of GSC-structures and to develop new formulae for the hydraulic stability of crest GSCs of submerged/low-crested GSC-structures. First, the present knowledge related to the engineering properties of GSCs and their effects on the stability of GSC-structures and the existing hydraulic stability formulae for GSC-structures were critically reviewed. Second, four series of especially designed laboratory experiments, which allowed us to have an insight into the influence of the above mentioned properties on the stability of GSC-structures and also to obtain the required parameters for the numerical modelling of their stability were performed. Experimental investigations consisted of two types of laboratory experiments (drop tests and pullout tests), small scale wave flume tests (hydraulic stability tests) and hydraulic flume tests (permeability tests). Third, numerical modelling of GSC-structures was conducted using the weakly coupled RANS-VOF model and FEM-DEM models. Finally, combining both the experimental and numerical results, new stability curves and simple formulae were developed for the hydraulic stability of crest GSCs. This newly developed stability curves and stability formulae are expected to foster the applications of GSC structures for coastal protection.Vielseitige und innovative Lösungen für die Bemessung effektiver Küstenschutzbauwerke sowie Verstärkung existierender, bedrohter Küstenbarrieren werden benötigt. Dies beinhaltet auch Dünenverstärkungen und Kolkschutzmaßnahmen. Sandcontainer aus Geotextilien (GSC) sind eine günstige, flexible und reversible Lösung, die schon mehr als 50 Jahre im marinen und wasserbaulichen Bereich Anwendung findet. Trotzdem befinden sich GSCs immer noch in der Entwicklung und es sind bisher keine Richtlinien zur Bemessung von GSC-Bauwerken auf Grundlage wissenschaftlicher Erkenntnisse vorhanden. Die vorliegende Arbeit ist fokussiert auf die Evaluierung der Einflüsse der wichtigsten Eigenschaften auf die hydraulische Stabilität von GSC-Bauwerken sowie der Entwicklung eines neuen Ansatzes zur Vorhersage der hydraulischen Stabilität von Kronen-GSCs von Unterwasser- bzw. sehr niedrigen GSC- Bauwerken. Zunächst wurde der Wissensstand zu den betreffenden Eigenschaften von GSCs und ihrem Einfluss auf die Stabilität von GSC-Bauwerken und bestehende hydraulische Stabilitätsansätze kritisch bewertet. Anschließend wurden vier speziell entwickelte Experimente durchgeführt, welche Einblick in den Einfluss der oben genannten Eigenschaften auf GSC-Bauwerke gewährte und die Randbedingung für die numerische Modellierung der Stabilität festlegte. Unterschiedliche Arten von Experimenten wurden durchgeführt: zwei Laborexperimente (Fall- und Zugversuche), kleinmaßstäbliche Wellenkanalversuche (hydraulische Stabilität) und Versuche im Strömungskanal (Durchlässigkeit). Weiterhin wurden numerische Simulationen der GSC-Bauwerke mit Hilfe eines schwach gekoppelten RANS-VOF und FEM-DEM Modells durchgeführt. Zuletzt wurden die Ergebnisse der experimentellen und numerischen Untersuchungen zusammengeführt und neue Stabilitätskurven und einfache Berechnungsansätze für die hydraulische Stabilität von Kronen-GSCs entwickelt

Multivariate analysis reveals that BVDV field isolates do not show a close VN-based antigenic relationship to US vaccine strains

Objective Evaluate bovine viral diarrhea virus (BVDV) antigenicity by using virus neutralization titers (VNT) analyzed using the principal component analysis (PCA) from antisera generated against US-based vaccine strains against both US-origin field isolates and non-US-origin field isolates. Results Data from both independent analyses demonstrated that several US-origin and non-US-origin BVDV field isolates appear to be antigenically divergent from the US-based vaccine strains. Results from the combined analysis provided greater insight into the antigenic diversity observed among BVDV isolates. Data from this study further support genetic assignment into BVDV subgenotypes, as well as strains within subgenotypes is not representative of antigenic relatedness. PCA highlights isolates that are antigenically divergent from members of the same species and subgenotype and conversely isolates that belong to different subgenotypes have similar antigenic characteristics when using antisera from US-based vaccine isolates

In vitro method to evaluate virus competition between BVDV-1 and BVDV-2 strains using the PrimeFlow RNA assay

Bovine viral diarrhea viruses (BVDV), segregated in BVDV-1 and BVDV-2 species, lead to substantial economic losses to the cattle industry worldwide. It has been hypothesized that there could be differences in level of replication, pathogenesis and tissue tropism between BVDV-1 and BVDV-2 strains. Thus, this study developed an in vitro method to evaluate virus competition between BVDV-1 and BVDV-2 strains. To this end the competitive dynamics of BVDV-1a, BVDV-1b, and BVDV-2a strains in cell cultures was evaluated by a PrimeFlow RNA assay. Similar results were observed in this study, as was observed in an earlier in vivo transmission study. Competitive exclusion was observed as the BVDV-2a strains dominated and excluded the BVDV-1a and BVDV-1b strains. The in vitro model developed can be used to identify viral variations that result in differences in frequency of subgenotypes detected in the field, vaccine failure, pathogenesis, and strain dependent variation in immune responses

Rocking of offshore lighthouses under extreme wave impacts: Limit analysis, analytic formulations and distinct element method

This study describes the structural response of historic lighthouses to extreme wave impacts. Located offshore on exposed rocks, 19th Century lighthouses were built with large interlocked granite blocks and have survived weathering for nearly two centuries. Under extreme wave impacts, lighthouses of this structural typology may uplift and rock, whereas sliding is prevented by the vertical interlocking. The uplift and sliding thresholds calculated with the limit analysis method reveal why this structural system is capable of bearing extreme wave impacts without failure. The ingenious vertical keying is proven to be a major characteristic that contributes to the resilience of these lighthouses. The structural response is explained with the use of analytic formulations of the rocking motion. Detailed analysis of the response to wave impact is conducted with reference to Wolf Rock lighthouse. The impact wave corresponding to a 250-year effective return period is identified using non-stationary Bayesian extreme analysis. Moreover, wave flume tests on a scaled cylindrical structure were performed to identify the wave impact force time-history shapes. Based on two waves: a theoretical time-history based on existing models in the literature and the measured time-histories from small-scale experiments, a series of synthetic force time-history sequences are generated for the purposes of a parametric analysis. This parametric analysis, with the Distinct Element Method, using the commercial software 3DEC, reveals the influence of the duration and shape of the force time-history function. For impacts with the same impulse values, shorter time impacts produce the most intense opening of joints, despite causing smaller horizontal displacements. Furthermore, variability in the structural response is revealed even for impacts of the same impulse, duration and maximum force but different shape of the force time-history

Evaluation of Current Socio-Economic Status for Development of Water Supply and Sanitation in Rural Sector

The present study was carried out on Deiyanwela area in Aranayake DSD in Kegalle District to identify the socio-economic status in the study area for the provision of necessary planning information in implementing the Water Supply and Sanitation Improvement project and identify critical issues. A semi-structured questionnaire survey was conducted for households (n=100) for assessing the Social-demographic and economic background of the community through random sampling technique in project impact area. Majority, (95%) indicated that their livelihood pattern as mixed economic while (5%) as agricultural. (88%) of the families were headed by males whereas (12%) families are headed by females in the project area. Project impact area is composed of (99%) Sinhalese population and (1%) Tamils population respectively. In terms of Water Consumption Patterns, (21%) of houses use existing water supply scheme and (12%) fulfill their water requirement from private protected wells located within their premises. Surface water usage is (23%), which is not safe unless subjected to disinfection before drinking. (80%) of the respondents mentioned that water is insufficient during dry seasons, which may cause to reduce the water quality as well. Majority of the respondents (79%) mentioned that they were not satisfied with their present water supply. Therefore, they expect an improvement of the existing water supply facilities. In relation to health and hygiene, since, currently there was no proper water treatment method, (95%) people followed domestic purification methods such as domestic filters and boiling; whereas (5%) are using traditional purification methods. Nearly (85%) of the households had proper sanitation facilities while (5%) of the people did not have toilets. From these (85%), (50%) was accounted for water sealed toilets with cistern and (35%) accounted for water sealed toilets without cistern. Since the current water supply was insufficient to cover their demand, majority of the people were willing to acquire new water connection. Thus, (96%) people were willing to pay a monthly water bill. (22%) of households receive the government food subsidy of Samurdhi given for households living below the official poverty line with regards to economy. (33%) of the people were involved in professions in the private sector, (24%) accounted for the Agriculture while unemployed population was (2%). The monthly expenditure, (42%) of people earned monthly income of LKR.10, 000-20,000 and only (3%) of people earned more than LKR.50, 000. In conclusion it revealed that there was a necessity and high demand for pipe born water, sanitation and economic development and incorporation of a water supply and sanitation improvement project is a sustainable solution.Keywords: Water supply, Sanitation, Socio-economic, Improvement, Tropica

Influence of the Spatial Pressure Distribution of Breaking Wave Loading on the Dynamic Response of Wolf Rock Lighthouse

The survivability analysis of offshore rock lighthouses requires several assumptions of the pressure distribution due to the breaking wave loading (Raby et al. (2019), Antonini et al. (2019). Due to the peculiar bathymetries and topographies of rock pinnacles, there is no dedicated formula to properly quantify the loads induced by the breaking waves on offshore rock lighthouses. Wienke’s formula (Wienke and Oumeraci (2005) was used in this study to estimate the loads, even though it was not derived for breaking waves on offshore rock lighthouses, but rather for the breaking wave loading on offshore monopiles. However, a thorough sensitivity analysis of the effects of the assumed pressure distribution has never been performed. In this paper, by means of the Wolf Rock lighthouse distinct element model, we quantified the influence of the pressure distributions on the dynamic response of the lighthouse structure. Different pressure distributions were tested, while keeping the initial wave impact area and pressure integrated force unchanged, in order to quantify the effect of different pressure distribution patterns. The pressure distributions considered in this paper showed subtle differences in the overall dynamic structure responses; however, pressure distribution #3, based on published experimental data such as Tanimoto et al. (1986) and Zhou et al. (1991) gave the largest displacements. This scenario has a triangular pressure distribution with a peak at the centroid of the impact area, which then linearly decreases to zero at the top and bottom boundaries of the impact area. The azimuthal horizontal distribution was adopted from Wienke and Oumeraci’s work (2005). The main findings of this study will be of interest not only for the assessment of rock lighthouses but also for all the cylindrical structures built on rock pinnacles or rocky coastlines (with steep foreshore slopes) and exposed to harsh breaking wave loading.</jats:p

Use of multivariate analysis to evaluate antigenic relationships between US BVDV vaccine strains and non-US genetically divergent isolates

Bovine viral diarrhea virus (BVDV) comprises two species, BVDV-1 and BVDV-2. But given the genetic diversity among pestiviruses, at least 22 subgenotypes are described for BVDV-1 and 3-4 for BVDV-2. Genetic characterization is generally accomplished through complete or partial sequencing and phylogeny, but it is not a reliable method to define antigenic relationships. The traditional method for evaluating antigenic relationships between pestivirus isolates is the virus neutralization (VN) assay, but interpretation of the data to define antigenic relatedness can be difficult to discern for BVDV isolates within the same BVDV species. Data from this study utilized a multivariate analysis for visualization of VN results to analyze the antigenic relationships between US vaccine strains and field isolates from Switzerland, Italy, Brazil, and the UK. Polyclonal sera were generated against six BVDV strains currently contained in vaccine formulations, and each serum was used in VNs to measure the titers against seven vaccine strains (including the six homologous strains) and 23 BVDV field isolates. Principal component analysis (PCA) was performed using VN titers, and results were interpreted from PCA clustering within the PCA dendrogram and scatter plot. The results demonstrated clustering patterns among various isolates suggesting antigenic relatedness. As expected, the BVDV-1 and BVDV-2 isolates did not cluster together and had the greatest spatial distribution. Notably, a number of clusters representing antigenically related BVDV-1 subgroups contain isolates of different subgenotypes. The multivariate analysis may be a method to better characterize antigenic relationships among BVDV isolates that belong to the same BVDV species and do not have distinct antigenic differences. This might be an invaluable tool to ameliorate the composition of current vaccines, which might well be important for the success of any BVDV control program that includes vaccination in its scheme

Use of multivariate analysis to evaluate antigenic relationships between US BVDV vaccine strains and non-US genetically divergent isolates.

Bovine viral diarrhea virus (BVDV) comprises two species, BVDV-1 and BVDV-2. But given the genetic diversity among pestiviruses, at least 22 subgenotypes are described for BVDV-1 and 3-4 for BVDV-2. Genetic characterization is generally accomplished through complete or partial sequencing and phylogeny, but it is not a reliable method to define antigenic relationships. The traditional method for evaluating antigenic relationships between pestivirus isolates is the virus neutralization (VN) assay, but interpretation of the data to define antigenic relatedness can be difficult to discern for BVDV isolates within the same BVDV species. Data from this study utilized a multivariate analysis for visualization of VN results to analyze the antigenic relationships between US vaccine strains and field isolates from Switzerland, Italy, Brazil, and the UK. Polyclonal sera were generated against six BVDV strains currently contained in vaccine formulations, and each serum was used in VNs to measure the titers against seven vaccine strains (including the six homologous strains) and 23 BVDV field isolates. Principal component analysis (PCA) was performed using VN titers, and results were interpreted from PCA clustering within the PCA dendrogram and scatter plot. The results demonstrated clustering patterns among various isolates suggesting antigenic relatedness. As expected, the BVDV-1 and BVDV-2 isolates did not cluster together and had the greatest spatial distribution. Notably, a number of clusters representing antigenically related BVDV-1 subgroups contain isolates of different subgenotypes. The multivariate analysis may be a method to better characterize antigenic relationships among BVDV isolates that belong to the same BVDV species and do not have distinct antigenic differences. This might be an invaluable tool to ameliorate the composition of current vaccines, which might well be important for the success of any BVDV control program that includes vaccination in its scheme