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

Dynamic Load Balancing and Efficient Load Estimators for Asynchronous Iterative Algorithms

In a previous paper~\cite{HPCS2002}, we have shown the very high power of asynchronism for parallel iterative algorithms in a global context of grid computing. In this article, we study the interest of coupling load balancing with asynchronism in such algorithms. After proposing a non-centralized version of dynamic load balancing which is best suited to asynchronism, we verify its efficiency by some experiments on a general Partial Differential Equation (PDE) problem. Finally, we give some general conditions for the use of load balancing to obtain good results with this kind of algorithms and discuss the choice of the residual as an efficient load estimator

Performance comparison of parallel programming environments for implementing AIAC algorithms

International audienceAIAC algorithms (Asynchronous Iterations Asynchronous Communications) are a particular class of parallel iterative algorithms. Their asynchronous nature makes them more efficient than their synchronous counterparts in numerous cases as has already been shown in previous works. The first goal of this article is to compare several parallel programming environments in order to see if there is one of them which is best suited to efficiently implement AIAC algorithms. The main criterion for this comparison consists in the performances achieved in a global context of grid computing for two classical scientific problems. Nevertheless, we also take into account two secondary criteria which are the ease of programming and the ease of deployment. The second goal of this study is to extract from this comparison the important features that a parallel programming environment must have in order to be suited for the implementation of AIAC algorithms

A decentralized convergence detection algorithm for asynchronous parallel iterative algorithms

We introduce a theoretical algorithm and its practical version to perform decentralized detection of the global convergence of parallel asynchronous iterative algorithms. We prove that even if the algorithm is completely decentralized, the detection of global convergence is achieved on one processor under the classical conditions. The proposed algorithm is very useful in the context of grid computing in which the processors are distributed and in which detecting the convergence on a master processor may be penalizing or even impossible as in Peer to Peer computations framework. Finally, the efficiency of the practical algorithm is illustrated in a typical experiment

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