Seismic assessment of hollow core concrete bridge piers

Hollow core concrete bridge piers are traditionally believed to be vulnerable to seismic action. However, the seismic vulnerability of such piers has not been investigated fully. In this paper, an analytical model to assess seismic vulnerability of hollow core concrete bridge pier is developed. The model is validated with available experimental results. Code recommendations for hollow core bridge piers are evaluated. It is shown that confinement reinforcement requirements in the codes are sometimes highly conservative and sometimes non-conservative. However, the recently developed confinement reinforcement equations for solid bridge piers at Sherbrooke University can be applied for economic and safe design. It is demonstrated that hollow core bridge piers are not as vulnerable as it is traditionally believed. Such piers can attain expected ductility, if designed properly

Effects of combined sewer overflows on a periurban stream ecosystem: Methodological approach

International audienceHere we develop from a long term field experiment an assessment method of interstitial fauna resilience to combined sewer overflows (CSOs) effect. We address the case of small water courses for which the ratio of CSOs to natural flow can be 1 to much more. Biotic material was collected in the benthic and hyporheic layers. Biotic material focussed mainly on oligocheates species whose diversity, species category and abundance are resumed into metrics, called functional traits (FTrs), giving indications on flux dynamics and nutrient bio-assimilation capacity. The biotic resilience is assessed through the analysis of the response time of the biota to CSOs and natural flow characteristics, here called hydrological indices (HIs). In this aim, a series of hydrological indices are defined to reveal varying aspects of the dynamics of CSOs and natural flows. A main result is that CSOs can have both degrading and boosting effects on the biota of a stony stream. Some CSOs characteristics can explain the physical processes supporting these contrasting effects. In particular the geomorphic characteristics of the water course. Management perspectives emerge from the CSOs hydrological indices and resilience of the biota

Effect of time to onset on clinical features and prognosis of post-sternotomy mediastinitis

AbstractIncubation time affects the clinical features and outcome of many nosocomial infections. However, its role in the setting of post-sternotomy mediastinitis (PSM) has not been specifically studied. The present study aimed to evaluate the impact of time to onset of PSM on the clinical presentation and outcomes of patients. Hospital records of 197 patients who developed PSM over a 10-year period and were treated by closed drainage using Redon catheters were reviewed retrospectively. Follow-up was complete for all included patients (median of 19 months); 98 patients developed early-onset PSM (time from initial operation to PSM <14 days) and 99 patients had late-onset PSM (≥14 days). Patients with late-onset PSM had a higher rate of internal thoracic artery harvest and mediastinal re-exploration after initial operation. Patients with early-onset PSM presented more frequently with septic shock. Microbiological findings differed between early- and late-onset PSM by a higher incidence of Enterococcus species in the former and of Staphylococcus aureus in the latter. Overall mortality reached 34% (n = 66). Rates of superinfection, treatment failure, mediastinitis-related death, mortality at 1 year and overall mortality were all significantly higher in patients with early-onset PSM. Multiple regression procedures identified early-onset PSM as a significant and independent risk factor for both 1-year (OR 2.40; 95% CI 1.12-5.11) and overall (OR 2.11; 95% 1.26-3.53) mortality. In conclusion, the results obtained in the present study support the distinction between early- and late-onset PSM with different clinical and pathophysiological features. Early-onset PSM is associated with a significantly higher morbidity and mortality compared to late-onset PSM

Characterisation by image analysis of anaerobic microbial aggregates under shock conditions

In the present work the characterisation by image analysis of anaerobic biomass under organic and hydraulic shocks was performed. The digester was fed with a synthetic substrate, containing 50% of oleic acid (as COD). Organic and hydraulic shocks were performed by increasing the substrate concentration or by lowering the hydraulic retention time. In both cases the organic loading rate changed from 6 to 30 kgCOD/m³.d. Hydraulic shock induced fast and persistent changes both in the number and length of filaments, but in the organic shock significant changes were detected later and initial values were recovered 840 hours after the shock.Fundação Calouste Gulbenkian (FCG) - post-doctoral research grant.Generalitat de Catalunya. Consell Interdepartamental de Recerca i Innovació Tecnològica (CIRIT) - predoctoral fellowship

Survey of a wastewater treatment plant microfauna by image analysis

The microfauna present in the activated sludge of a wastewater treatment plant is mainly composed by bacteria, protozoa and metazoa. The protozoan species are quite sensitive to physical, chemical and operational processes making them, thus, precious indicators of the state of the plant. Several authors already established relationships between the predominance of certain species or group and some parameters of the plant, such as the biotic indices namely the Sludge Biotic Index. All the above-mentioned procedures demand the identification, classification and quantification of the different species. Normally this is done manually, which implies both time and expertise. In the present work a semi-automatic protozoan recognition procedure by means of image analysis is attempted. The program built for this purpose (ProtoRec v.3) was also used to study the evolution of the microfauna during transient operation times (stoppage and re-run). The results were rather satisfactory in terms of protozoa recognition and the survey of the transient phase allowed verifying the aging and degradation of the microfauna by means of the different predominant species

Estudo por Análise de Imagem do Comportamento de uma Estação de Tratamento de Efluentes sob Condições Transientes

A microfauna presente numa estação de tratamento de efluentes por lamas activadas é composta essencialmente por bactérias, protozoários e metazoários. Os protozoários apresentam uma sensibilidade aos fenómenos físico-químicos e operacionais que os tornam indicadores do estado de funcionamento da estação. A literatura apresenta relações entre a abundância de uma certa espécie ou grupo e parâmetros da estação. Uma outra possibilidade é a qualificação do estado da ETAR através de índices bióticos como o SBI. Todos estes procedimentos exigem uma identificação, classificação e quantificação das espécies presentes. Geralmente isto é feito manualmente, o que implica tempo e muitas vezes a presença de um técnico especializado. Neste trabalho é proposto um procedimento para reconhecimento semi-automático das espécies de protozoários por análise de imagem. Este programa (ProtoRec v.2) foi em seguida utilizado para estudar a evolução da microfauna durante períodos de transição (paragem e arranque da estação). Os resultados obtidos foram satisfatórios em relação ao reconhecimento das espécies pelo programa e o acompanhamento da estação permitiu-nos verificar a degradação e envelhecimento da lama e o aparecimento de protozoários que evidenciam tal facto

Survey of protozoa and metazoa populations in wastewater treatment plants by image analysis and discriminant analysis

The biota present in the activated sludge of a wastewater treatment plant are mainly composed of bacteria, Protozoa and Metazoa. The Protozoa and Metazoa species are important micro-organisms taking part in the ecosystem balance in wastewater treatment plants and are quite sensitive to physical, chemical and operational processes. Several authors have established relationships between the predominance of certain species or groups and some variables of the plant. Such analysis demands the identification and quantification of the different species, which requires skilled workers, specializing in zoology or protozoology, and is time-consuming. To overcome those problems, semi-automatic image analysis and discriminant analysis were carried out for the identification procedures. The overall results were very promising in terms of Protozoa and Metazoa group recognition and of survey of plant conditions. Copyright 2004 John Wiley & Sons, Ltd.Financial support for the co-operation between the Portuguese (Braga) and French (Nancy) teams was provided by the French Embassy in Portugal and ICCTI (Portugal). A. L. Amaral was supported by a PhD grant (PRAXIS XXI/BD/20325/99) of ‘Fundação para a Ciência e Tecnologia’ (Portugal). M. da Motta was supported by a grant of the National Council of Scientific and Technological Development of Brazil (CNPq)

Characterisation by image analysis of anaerobic sludge under shock conditions

In the present work the characterisation by image analysis of anaerobic biomass under organic and hydraulic shocks was performed. The digester was fed with a synthetic substrate, containing 50% oleic acid (as COD). Organic and hydraulic shocks were performed by stepwise increasing the substrate concentration or by reducing the hydraulic retention time. In both cases the organic loading rate changed from 6 to 30 kg COD/m³.d. Hydraulic shock induced a fast decrease in the number of free filaments and in total filament length, which attained a minimum value 51 hours after beginning the shock. The initial filament values were not recovered 340 hours after the hydraulic shock. In the organic shock, the minimum values of these parameters were detected 200 hours after beginning the shock and initial values were recovered 840 hours after. During the hydraulic shock the methanogenic acetoclastic activity was directly correlated to the number and length of free filaments. This result suggests that filaments are predominantly acetoclastic bacteria, probably Methanosaeta.Ministério da Ciência e Tecnologia. Instituto de Cooperação Científica e Tecnológica Internacional (ICCTI), Ambassade de France in Portugal - project no. 203 B4