Rationalising assessment approaches for masonry arch bridges

Masonry arch bridges, most of which have far exceeded modern design lives, have demonstrated themselves to be sustainable structures with low life-cycle costs. However, increased traffic loading and material deterioration over time necessitate periodic reassessment of these structures. There are numerous different analytical methods available for the assessment of masonry arch bridges. The expectation is that for increasing levels of assessment complexity an increase in load capacity converging on the ultimate capacity would be achieved. In this paper it is demonstrated that this is not always the case. This has cost implications for both the bridge assessment itself and for costs associated with load restrictions and strengthening measures. Five different assessment methods were selected to assess a set of 11 single-span bridges, ranging in span from 2·4 m to 15·2 m, with the objective of reviewing and rationalising current assessment guidelines for masonry arch bridges. The bridges chosen are a representative sample of the stone arch bridges on the Irish National Roads network. It was found that there is a significant variation in assessed capacity depending on the assessment method used. Limit state analysis methods were found to generally result in higher ratings for segmental bridges while elastic methods resulted in higher ratings for three-centred or semi-circular bridges. Assessment ratings found using the Military Engineering Experimental Establishment (MEXE) method were difficult to rationalise across the bridge set considered in this study. Following a review of the origins of the MEXE method and its current form as set out in the assessment guidance, it is recommended that its use as the predominant tool in a simplified assessment procedure is not appropriate and that a more rational approach is required for a more realistic and reliable calculation of bridge capacity. The development of an improved assessment methodology is being considered as part of the current study. </jats:p

The early evolution of land plants, from fossils to genomics: a commentary on Lang (1937) ‘On the plant-remains from the Downtonian of England and Wales'

© 2015 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited. The file attached is the published version of the article

System Identification of a Building from Multiple Seismic Records

This paper describes the identification of finite dimensional, linear, time-invariant models of a 4-story building in the state space representation using multiple data sets of earthquake response. The building, instrumented with 31 accelerometers, is located on the University of California, Irvine campus. Multiple data sets, recorded during the 2005 Yucaipa, 2005 San Clemente, 2008 Chino Hills and 2009 Inglewood earthquakes, are used for identification and validation. Considering the response of the building as the output and the ground motion as the input, the state space models that represent the underlying dynamics of the building in the discrete-time domain corresponding to each data set are identified. The time-domain Eigensystem Realization Algorithm with the Observer/Kalman filter identification procedure are adopted in this paper, and the modal parameters of the identified models are consistently determined by constructing stabilization diagrams. The four state space models identified demonstrate that the response of the building is amplitude dependent with the response frequency and damping, being dependent on the magnitude of ground excitation. The practical application of this finding is that the consistency of this building response to future earthquakes can be quickly assessed, within the range of ground excitations considered (0.005g–0.074g), for consistency with prior response—this assessment of consistent response is discussed and demonstrated with reference to the four earthquake events considered in this study. Inclusion of data sets relating to future earthquakes will enable the findings to be extended to a wider range of ground excitation magnitudes

Characteristic Vertical Response of a Footbridge Due to Crowd Loading

The characteristic vertical vibration of a flexible footbridge subject to crowd loading is examined in this paper. Typically, bridge vibrations produced from a crowd of pedestrians are estimated by using an enhancement factor applied to the effect caused by a single pedestrian. In this paper, a single pedestrian model, represented by a spring mass damper, which incorporates variables such as pedestrian mass and body stiffness, is used to calibrate a computationally efficient moving force model. This calibrated moving force model is further used in Monte Carlo simulations of non-homogenous crowds to estimate characteristic vertical vibration levels. Enhancement factors, which could be applied to simple single pedestrian moving force models in estimating the response due to a crowd are thus derived. Such enhancement factors are then compared to previously published values. It is found that the greatest difference between the spring mass damper and moving force models respectively occurs when the bridge frequency is at the mean crowd pacing frequency. For bridges with frequencies even slightly removed from this mean, moving force models appear adequate

Multiple-locus variable number of tandem repeat analysis (MLVA) of Irish verocytotoxigenic Escherichia coli O157 from feedlot cattle: uncovering strain dissemination routes

<p>Abstract</p> <p>Background</p> <p>The identification of the routes of dissemination of <it>Escherichia coli (E. coli) </it>O157 through a cohort of cattle is a critical step to control this pathogen at farm level. The aim of this study was to identify potential routes of dissemination of <it>E. coli </it>O157 using Multiple-Locus Variable number of tandem repeat Analysis (MLVA).</p> <p>Results</p> <p>Thirty-eight environmental and sixteen cattle faecal isolates, which were detected in four adjacent pens over a four-month period were sub-typed. MLVA could separate these isolates into broadly defined clusters consisting of twelve MLVA types. Strain diversity was observed within pens, individual cattle and the environment.</p> <p>Conclusion</p> <p>Application of MLVA is a broadly useful and convenient tool when applied to uncover the dissemination of <it>E. coli </it>O157 in the environment and in supporting improved on-farm management of this important pathogen. These data identified diverse strain types based on amplification of VNTR markers in each case.</p

Controlling Blown Pack Spoilage Using Anti-Microbial Packaging

peer-reviewedActive (anti-microbial) packaging was prepared using three different formulations; Auranta FV; Inbac-MDA and sodium octanoate at two concentrations (2.5 and 3.5 times their minimum inhibitory concentration (MIC, the lowest concentration that will inhibit the visible growth of the organisms) against Clostridium estertheticum, DSMZ 8809). Inoculated beef samples were packaged using the active packaging and monitored for 100 days storage at 2 °C for blown pack spoilage. The time to the onset of blown pack spoilage was significantly (p < 0.01) increased using Auranta FV and sodium octanoate (caprylic acid sodium salt) at both concentrations. Moreover, sodium octanoate packs had significantly (p < 0.01) delayed blown pack spoilage as compared to Auranta FV. It was therefore concluded that Auranta FV or sodium octanoate, incorporated into the packaging materials used for vacuum packaged beef, would inhibit blown pack spoilage and in the case of the latter, well beyond the 42 days storage period currently required for beef primalsDepartment of Agriculture, Food and the Marin

Assessing Integrated Pest Management Implementation and Knowledge Gaps in South Dakota

A survey of commercial pesticide applicator training participants was carried out during 2015 winter pesticide certification meetings to assess integrated pest management (IPM) knowledge gaps. Overall, the majority of the respondents reported that they have adequate access to IPM information and that they apply IPM principles in their pest management programs. Preventive fungicide use was identified as a regular practice by half the respondents and was dependent on the region of the state. Participants identified basic pest identification as an area in which more resources are needed. Online information and field days were the preferred options for accessing outreach and Extension