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Chihuahua, Mexico

Hadayeghi A.,CIMA | Shalaby A.S.,University of Toronto | Persaud B.N.,Ryerson University
Accident Analysis and Prevention | Year: 2010

A common technique used for the calibration of collision prediction models is the Generalized Linear Modeling (GLM) procedure with the assumption of Negative Binomial or Poisson error distribution. In this technique, fixed coefficients that represent the average relationship between the dependent variable and each explanatory variable are estimated. However, the stationary relationship assumed may hide some important spatial factors of the number of collisions at a particular traffic analysis zone. Consequently, the accuracy of such models for explaining the relationship between the dependent variable and the explanatory variables may be suspected since collision frequency is likely influenced by many spatially defined factors such as land use, demographic characteristics, and traffic volume patterns. The primary objective of this study is to investigate the spatial variations in the relationship between the number of zonal collisions and potential transportation planning predictors, using the Geographically Weighted Poisson Regression modeling technique. The secondary objective is to build on knowledge comparing the accuracy of Geographically Weighted Poisson Regression models to that of Generalized Linear Models. The results show that the Geographically Weighted Poisson Regression models are useful for capturing spatially dependent relationships and generally perform better than the conventional Generalized Linear Models. © 2009 Elsevier Ltd. All rights reserved.

Zmigrodzki S.,CIMA
Large Structures and Infrastructures for Environmentally Constrained and Urbanised Areas | Year: 2010

The existing open air aquatic complex on Sainte-Hélène Island was chosen to host 2005 Aquatic Sports World Championships. The old concrete pools built in 1953 had to be replaced by new structures and fit in the existing site. In the new layout, the swimming pool was relocated which led to problems due to soil conditions. The soil was sensitive and heterogeneous so settlements and resulting lateral displacements had to be considered in the design in order to respect dimensional criteria for Olympic pools. To guarantee the quality of works within a tight schedule, the upper section of the walls was made of prefabricated steel panels. As result, the rigid "box" formed by the concrete corridor around the pool was lost. Consequently, a combination of soil consolidation, interaction of soil-structure and phasing of construction-backfilling became part of design.

Godat A.,University of Quebec | Legeron F.,Universite de Sherbrooke | Bazonga D.,CIMA
Thin-Walled Structures | Year: 2012

This paper presents experimental tests conducted to investigate the local buckling behavior of thin-walled tubular polygon steel columns. The experimental program consists of six stub columns with three different cross-sections, octagonal (eight-sided), dodecagonal (twelve-sided) and hexdecagonal (sixteen-sided), tested under concentric compression. For each cross-section, two values of the plate slenderness ratio (plate width-to-thickness ratio) are considered. Accurate measurements of geometrical imperfections are taken prior to the test. The experimental results show that the local buckling mode of failure depends on the type of the cross-section. Moreover, the plate slenderness ratio is the main factor controlling the local buckling capacity. Design equations provided in the ASCE 48-05, the EC3 and Migita and Fukumoto to predict the local buckling capacity of tubular polygons are evaluated against experimental results of 22 polygons tested under concentric compression available in the literature. Based on drawbacks observed in the design equations, the Loovs equation developed on basis of the ultimate stress concept is adjusted with new fitting parameters to fit for tubular polygon columns. The accuracy of the new equation is evaluated through a comparison with the experimental results. © 2011 Elsevier Ltd. All rights reserved.

Carvalho A.,University of Aveiro | Monteiro A.,University of Aveiro | Solman S.,CIMA | Miranda A.I.,University of Aveiro | Borrego C.,University of Aveiro
Environmental Science and Policy | Year: 2010

Climate change alone may deeply impact air quality levels in the atmosphere because the changes in the meteorological conditions will induce changes on the transport, dispersion and transformation of air pollutants. The aim of this work was to evaluate the impact of climate change on the air quality over Europe and Portugal, using a reference year (year 1990) and a IPCC SRES A2 year (year 2100). The Hadley Centre global atmospheric circulation model (HadAM3P) was used to provide results for these two climatic scenarios, which were then used as synoptic forcing for the MM5-CHIMERE air quality modelling system. In order to assess the contribution of future climate change on O3 and PM concentrations, no changes in regional emissions were assumed and only climate change forcing was considered. The modelling results suggest that the O3 monthly mean levels in the atmosphere may increase almost 50μgm-3 across Europe in July under the IPCC SRES A2 scenario. In Portugal, this increase may reach 20μgm-3. The changes of PM10 monthly average values over Europe will depend on the region. The increase in PM10 concentrations during specific months could be explained by the average reduction of the boundary layer height and wind speed. © 2010 Elsevier Ltd.

Carvalho A.,University of Aveiro | Monteiro A.,University of Aveiro | Flannigan M.,University of Alberta | Solman S.,CIMA | And 2 more authors.
Atmospheric Environment | Year: 2011

In a future climate scenario forest fire activity over Portugal will substantially increase and consequently area burned and forest fire emissions to the atmosphere are also expected to increase. This study investigated the impact of future forest fire emissions on air quality over Portugal under the IPCC SRES A2 scenario. Reference and future climate change scenarios were simulated using the MM5/CHIMERE air quality modelling system, which was applied over Europe and over Portugal, using nesting capabilities. The initial and boundary conditions were provided by the HadAM3P model simulations for the reference and the future climate. The forest fire emissions were estimated using a methodology, which included the selection of emission factors for each pollutant, burning efficiency, fuel loads and the predicted area burned. These emissions were added to the simulation grid using specific parameterizations for their vertical distribution. Modelling results for Portugal pointed out that future forest fire activity will increase the O3 concentrations of almost 23 μg m-3 by 2100 but a decrease of approximately 6 μg m-3 is detected close to the main forest fire locations. Future forest fire emissions will also impact the PM10 concentrations over Portugal with increases reaching 20 μg m-3 along the Northern coastal region in July. The highest increases are estimated over the north and centre of Portugal where the area burned projections in future climate are higher. © 2011 Elsevier Ltd.

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