A risk ranking strategy for network level bridge management

Life-Cycle Civil Engineering - Proceedings of the 1st International Symposium on Life-Cycle Civil Engineering, IALCCE '08 2008, Pages 643-648At present almost all bridge owners and managers, i.e. Network Rail, Highways Agency and local authorities in the UK, carryout bridge inspections at regular intervals to collect information on condition and performance of bridges. Introduction of risk based approaches in the selection of inspection regimes can provide consistent safety levels within the network in a cost effective manner. This paper presents the development of a qualitative risk ranking strategy to characterize a network of bridges into groups with similar risk levels, which can form the basis for developing a risk based inspection regime over the network. There are a multitude of factors that affect risk. These factors are identified and rationally combined to present various attributes of bridges. A qualitative scoring system is then introduced which utilizes the attributes to rank bridges in terms of their relative risk. Sensitivity analysis is performed to quantify the effect of relative weights of the attributes on the risk scores. The methodology is demonstrated through its application on UK's Network Rail bridge stock comprising of about 40,000 bridges. The criteria to classify the severity of the attributes are established for the network. A random sample of bridges is ranked to illustrate the proposed methodology. © 2008 Taylor & Francis Group, London

Predictive SHM-supported deterioration modelling of reinforced concrete bridges

Deterioration, increase in loading demand and change in utilization have induced an unknown level of risk in the use of transport infrastructure systems. Bridges being a vital element of such systems, due to their very nature as well as their exposure to harsh environmental conditions, should be effectively managed for the benefit of the overall transport network. Predicting the future condition and reliability of the bridges is vitally important in this process. Probabilistic models have been developed to estimate and predict the extent of deterioration in, for example, concrete bridges. However, the input parameters of these models are fraught with uncertainties, thus severely limiting their accuracy, particularly over longer time frames. On the other hand, continuous innovations in the sensing and measurement technology have lead to the development of monitoring instruments that can provide continuous (or almost continuous) data regarding the actual structural performance in the time frame. This information cannot be used directly for the prediction of future performance, first because it typically pertains to a small number of specific locations, and secondly because it needs to be combined with a whole host of other knowledge components. Furthermore, uncertainties in the instruments/measurements and in the future behaviour of the structure and its interaction with the environment (e.g. including the effects of deterioration) also hinder the predictive capability of current modelling tools. The potential benefits of improving performance prediction through the integration of health monitoring systems with probabilistic predictive models, and their implications on the management of deterioration prone structures are presented in this paper through the development of an integrated methodology. It is shown, through application case studies, that the confidence in predicted performance can be significantly increased through the use of SHM-supported modelling of deterioration and the major inspection and maintenance activities can be delayed on the account of increased confidence in the predicted performance. An example of such integration is illustrated in Figure 1 for various cases of sensor outputs including attainment of limiting value as well as (Graph Presented) confirmation of safety at various points in time during the service life. It is clear that the uncertainty is reduced with the availability of additional information and the level of this reduction depends on the quality and timing of information obtained through sensing equipment. A sensitivity study of various input parameters has concluded that the range of predicted performance is considerably reduced through the updating methodology presented in this paper. A typical result is shown in Figure 2, which quantifies the influence of the number of sensors on the coefficient of variation for the time to corrosion initiation at rebar revel for various hypothesized exposure conditions. The case with '0' sensor indicates the prior corrosion initiation times. It can be seen that the influence of various models that could be assumed for exposure conditions is minimized by the integration of data obtained through SHM into the predictive models. Finally a life-cycle cost analysis for various management strategies (with and without the use of SHM) highlighted the safety and cost benefits that can be obtained through the use of SHM-supported predictive models (Figure 3). It is clear from the figure that the LCC is minimized for the case where decisions are aided with predictive models updated through SHM. It is recognized that the above conclusions are obtained from a limited number of application case studies. Clearly more work is needed in this area including physical tests and field data collection to improve our understanding of the underlying phenomena and to reduce prior uncertainties, especially those related with modelling and measurement (epistemic components). © 2006 Taylor & Francis Group

Measuring responses of harbour seals to potential aversive acoustic mitigation signals using controlled exposure behavioural response studies

This work was funded by Scottish Government's Marine Mammal Scientific Support Research Programme MMSS/001/11 and UK's Natural Environment Research Council (NERC), and Department for Environment Food and Rural Affairs (NE/J004251/1) and NERC (National Capability SMRU1001).1.  Some anthropogenic activities pose acute risks for marine species. For example, pile driving could damage the hearing of marine mammals while underwater explosions can also result in physical damage or death. Effective mitigation is required to reduce these risks, but the exclusion zones specified in regulations can extend over hundreds or thousands of metres and seals pose particular problems because they are difficult to detect at sea. 2.  Aversive sound mitigation aims to exclude animals from high‐risk areas before dangerous activities take place by broadcasting specific acoustic signals. Field research is needed to identify signals that might be effective in eliciting short‐term avoidance by marine species such as harbour seals (Phoca vitulina). A series of controlled‐exposure experiments (CEEs) were undertaken to measure seal movements in response to acoustic deterrent devices (ADD) and predator calls, and to assess the effectiveness of candidate signals for aversive sound mitigation. 3.  Seals were fitted with UHF/GPS transmitters providing continuous high‐resolution tracks and real‐time transmissions of their locations. A tracking/playback vessel located seals at sea and transmitted either ADD signals or orca (Orcinus orca) calls over a range of distances while seals were foraging or moving between sites. Behaviour before, during and after exposure was analysed to assess responses. 4.  One‐hundred and ten CEEs were assessed as being of at least ‘adequate’ quality. Of the 71 adequate trials with the Lofitech ADD, all 38 at ranges of <1 km (predicted received level 134.6 dB RMS re 1 μPa) elicited a response. The maximum response range was 3123 m (predicted RL: 111 dB RMS re 1 μPa). However, the responses observed did not always result in substantial movements away from the source, especially for seals that were travelling at the time of the exposures. More work is needed to better understand how exposure risks would be reduced in different scenarios. 5.  The mean net speed of horizontal movements for seals responding to aversive sounds (1.15 m s−1) was only 7% higher than their mean travel speed. 6.  Responses to broadcasts of orca calls were highly variable. 7.  The results suggest that signals similar to those generated by a Lofitech ADD could be used to reduce risks to harbour seals from pile driving and underwater explosions in coastal waters. More work will be needed to develop systems that match the requirements of industry and regulators and to explore whether these results can be generalized to offshore waters and to other phocids.PostprintPeer reviewe

Reliability, risk and lifetime distributions as performance indicators for life-cycle maintenance of deteriorating structures

This is the author’s version of a work that was accepted for publication in Reliability Engineering & System Safety. A definitive version was subsequently published at: http://dx.doi.org/10.1016/j.ress.2013.09.013Structural capacity deterioration is among the main causes of increasing failure probabilities of structural systems, thus maintenance interventions are a crucial task for their rational management. Several probabilistic approaches have been proposed during the last decades for the determination of cost-effective maintenance strategies based on selected performance indicators. However, benefits and drawbacks of each performance indicator with respect to the others should be further analyzed. The objective of this paper is to investigate probabilistic approaches based on the annual reliability index, annual risk, and lifetime distributions for life-cycle maintenance of structural systems. Maintenance schedules are obtained for representative series, parallel, and series-parallel systems considering total restoration of component resistances whenever a prescribed threshold, based on a selected performance indicator, is reached. Effects related to different structural configurations and correlation among failure modes are investigated. The superstructure of an existing bridge is used to illustrate the presented approaches

Biogeography in the deep : hierarchical population genomic structure of two beaked whale species

Funding for this research was provided by the Office of Naval Research, Award numbers N000141613017 and N000142112712. ABO was supported by a partial studentship from the University of St Andrews, School of Biology; OEG by the Marine Alliance for Science and Technology for Scotland (Scottish Funding Council grant HR09011); ELC by a Rutherford Discovery Fellowship from the Royal Society of New Zealand Te Aparangi; NAS by a Ramon y Cajal Fellowship from the Spanish Ministry of Innovation; MLM by the European Union’s Horizon 2020 Research and Innovation Programme (Marie Skłodowska-Curie grant 801199); CR by the Marine Institute (Cetaceans on the Frontier) and the Irish Research Council; and MTO by the Hartmann Foundation.The deep sea is the largest ecosystem on Earth, yet little is known about the processes driving patterns of genetic diversity in its inhabitants. Here, we investigated the macro- and microevolutionary processes shaping genomic population structure and diversity in two poorly understood, globally distributed, deep-sea predators: Cuvier’s beaked whale (Ziphius cavirostris) and Blainville’s beaked whale (Mesoplodon densirostris). We used double-digest restriction associated DNA (ddRAD) and whole mitochondrial genome (mitogenome) sequencing to characterise genetic patterns using phylogenetic trees, cluster analysis, isolation-by-distance, genetic diversity and differentiation statistics. Single nucleotide polymorphisms (SNPs; Blainville’s n = 43 samples, SNPs=13988; Cuvier’s n = 123, SNPs= 30479) and mitogenomes (Blainville’s n = 27; Cuvier’s n = 35) revealed substantial hierarchical structure at a global scale. Both species display significant genetic structure between the Atlantic, Indo-Pacific and in Cuvier’s, the Mediterranean Sea. Within major ocean basins, clear differentiation is found between genetic clusters on the east and west sides of the North Atlantic, and some distinct patterns of structure in the Indo-Pacific and Southern Hemisphere. We infer that macroevolutionary processes shaping patterns of genetic diversity include biogeographical barriers, highlighting the importance of such barriers even to highly mobile, deep-diving taxa. The barriers likely differ between the species due to their thermal tolerances and evolutionary histories. On a microevolutionary scale, it seems likely that the balance between resident populations displaying site fidelity, and transient individuals facilitating gene flow, shapes patterns of connectivity and genetic drift in beaked whales. Based on these results, we propose management units to facilitate improved conservation measures for these elusive species.Publisher PDFPeer reviewe

Looking forward through the past: identification of 50 priority research questions in palaeoecology

1. Priority question exercises are becoming an increasingly common tool to frame future agendas in conservation and ecological science. They are an effective way to identify research foci that advance the field and that also have high policy and conservation relevance. 2. To date, there has been no coherent synthesis of key questions and priority research areas for palaeoecology, which combines biological, geochemical and molecular techniques in order to reconstruct past ecological and environmental systems on time-scales from decades to millions of years. 3. We adapted a well-established methodology to identify 50 priority research questions in palaeoecology. Using a set of criteria designed to identify realistic and achievable research goals, we selected questions from a pool submitted by the international palaeoecology research community and relevant policy practitioners. 4. The integration of online participation, both before and during the workshop, increased international engagement in question selection. 5. The questions selected are structured around six themes: human–environment interactions in the Anthropocene; biodiversity, conservation and novel ecosystems; biodiversity over long time-scales; ecosystem processes and biogeochemical cycling; comparing, combining and synthesizing information from multiple records; and new developments in palaeoecology. 6. Future opportunities in palaeoecology are related to improved incorporation of uncertainty into reconstructions, an enhanced understanding of ecological and evolutionary dynamics and processes and the continued application of long-term data for better-informed landscape management

Co-operative group teaching and learning in the Greek and Cypriot primary education

Co-operative group teaching and learning is a child-centred teaching approach based on the theory of constructivism. In literature on educational studies, co-operative teaching and learning is generally defined as learning that takes place in an environment where pupils in small groups share ideas and work collaboratively in order to complete academic tasks. A large number of research carried out on co-operative teaching and learning has shown that this method has positive effects on pupils' school achievement in mixed ability and ethnocultural classes. The aim of the present study is to compare the Greek and Cypriot primary school teachers' and pupils' views about the efficacy of cooperative teaching and learning in mixed ability and multi-ethnic classes. A similar comparative study has not been carried out. The sample of the study consisted of 113 teachers (59 Greek and 54 Cypriot) and 161 pupils (80 Greek and 81 Cypriot), 9-11 years old. A quantitative methodology was used and data were collected through questionnaires. Results revealed that pupils' and teachers' perceptions about co-operative group teaching and learning were positive. However, the Cypriot primary school teachers and pupils exhibited more positive attitudes towards group work's efficacy and a better understanding of co-operative group teaching and learning compared to the Greek teachers and pupils respectively. © Common Ground, Stavroula Kaldi, Diamanto Filippatou, Maria Onoufriou