Seismic performance of group pile foundation with ground improvement during liquefaction

A pile foundation with ground improvement under the footing is a composite foundation with the objectives of enhancing the seismic performance and rationalizing the substructure by combining the pile foundation with ground improvement. Although the effectiveness of this method has been confirmed in previous studies for application to soft grounds, the applicability of this method to liquefiable grounds has yet to be fully investigated. In this study, therefore, centrifuge model tests and finite element analyses were conducted to clarify the effectiveness of this method and to ascertain the improvement in strength (stiffness) when the method is applied to a liquefiable ground. Firstly, in order to investigate the effect of an improved ground on the behavior of the pile foundation during liquefaction, dynamic centrifuge model tests were conducted for three cases with different strengths of the improved ground. Then, three-dimensional soil–water coupled finite element analyses of the centrifuge model experiments were performed to validate the applicability of the analytical method. After that, parametric studies, in which the strength of the improved ground and the input ground motion were changed, were conducted using the same analytical model. The results confirmed that the horizontal displacement of the pile heads was reduced by the improved ground even in the liquefiable ground, and that the effect of this reduction was more remarkable in cases of high stiffness of the improved ground. Furthermore, it was possible to reduce the bending moments at the pile heads by applying the ground improvement. However, since the bending moment at the boundary between the improved ground and the natural ground became the local maximum, there was an optimum stiffness of the ground improvement at which the maximum bending moment of the piles was reduced. This is because improving the ground around the pile heads has the same effect as extending the footing. It was thus concluded that the behavior of the pile foundation is similar to that of a composite foundation comprised of a caisson and group piles

Individual and environmental factors associated for overweight in urban population of Brazil

Background: Obesity is a significant global public health problem and the main cause of many chronic diseases in both developed and developing countries. The increase in obesity in different populations worldwide cannot be explained solely by metabolic and genetic factors; environmental and social factors also have a strong association with obesity. Thus, it is believed that the current obesity epidemic is the result of a complex combination of genetic factors and an obesogenic environment .The purpose of this study was to evaluate individual variables and variables within the built and social environment for their potential association with overweight and obesity in an urban Brazilian population. Methods: Cross-sectional study was carried out in a sample of 3404 adults living in the urban area of the city. Information from the surveillance system for chronic diseases of Brazilian Ministry of Health was used and individual data was collected by telephone interviews. The database was geocoded using the Brazilian System of Postal Codes for participant residences. An updated, existing list based on the current addresses of supermarkets and hypermarkets in the city was used as an indicator variable of the availability and access to food. Georeferenced information on parks, public squares, places for practicing physical activity and the population density were also used to create data on the built environment. To characterize the social environment, we used the health vulnerability index (HVI) and georeferenced data for homicide locations. Results: The prevalence was 44% for overweight, poisson regression was used to create the final model. The environment variables that independently associated with overweight were the highest population density, very high health vulnerability index and the homicide rate adjusted for individuals variables. The results of the current study illustrate and confirm some important associations between individual and environmental variables and overweight in a representative sample of adults in the Brazilian urban context. Conclusions: The social environment variables relating to the socioeconomic deprivation of the neighborhood and the built environment variables relating to higher walkability were significantly associated with overweight and obesity in Belo Horizonte.This study was funded by Brazilian Ministry of Health (number 134/209). G. Velásquez- Meléndez is researcher from the National Council for Scientific and Technological Development (CNPQ) and the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)