Revista Recursos Hdricos

DOI:10.5894/rh35n1-1
O texto deste artigo foi submetido para reviso e possvel publicao em janeiro de 2014, tendo sido aceite pela Comisso de Editores Cientficos Associados em abril de 2014. Este artigo parte integrante da Revista Recursos Hdricos, Vol. 35, N 1, 5-22, maio de 2014.

Eroses localizadas em pilares complexos de pontes: Desempenho de modelos de previso existentes

Local scour around complex bridge piers: Performance of existing predictors

Mario Enrique Moreno¹, Lcia Teixeira Couto², Rodrigo Maia³, Antnio Heleno Cardoso⁴

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1 - Mestre em Engenharia Civil, Doutorando da Faculdade de Engenharia da Universidade do Porto e Bolseiro de Investigao do Laboratrio Nacional de Engenharia Civil
2 - Investigadora Auxiliar do Laboratrio Nacional de Engenharia Civil /// membro da APRH n. 720
3 - Professor Associado da Faculdade de Engenharia da Universidade do Porto /// membro da APRH n. 1678
4 - Professor Catedrtico do Departamento de Engenharia Civil, Arquitetura e Georrecursos do Instituto Superior Tcnico

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RESUMO
A previso rigorosa da profundidade de cavidades de eroso associadas a pilares complexos, utilizados como apoio de tabuleiros de pontes, pode no ser garantida pela utilizao dos mtodos actualmente existentes. De entre esses mtodos, destacam-se os de Auckland, o HEC-18 e o do FDOT. Neste artigo, analisa-se o respetivo desempenho comparando as previses que fornecem com conjuntos de dados obtidos em laboratrio para seis modelos de pilares, cinco dos quais publicados em literatura da especialidade. A esses dados, adicionaram-se os de ensaios conduzidos no LNEC para um modelo de pilar de dimenses mais prximas de dimenses reais do que as dos outros pilares estudados.
Os trs modelos de clculo apresentam desvios de previso em relao s medies que dependem da posio do macio de encabeamento relativamente ao nvel inicial do leito; em geral, os maiores desvios ocorrem quando o macio se encontra parcialmente enterrado. Em face dos resultados da anlise dos desvios, conclui-se que o modelo FDOT aquele a que est associada uma menor probabilidade de previses por defeito, ou seja, aquele que produz previses seguras para uma maior percentagem de situaes que podem ocorrer na prtica da engenharia.

Palavras-chave: Pontes em leitos fluviais, eroso localizada, pilares complexos, previso da profundidade de eroso.

ABSTRACT
The rigorous prediction of local scour depth around complex piers, used to support bridge decks, may not be guaranteed by the predictors available at present. Among the available predictors, those of Auckland, HEC-18 and FDOT are the most popular. In this article, the performance of the tree methods is analysed, by comparing the respective predictions with sets of laboratory data for six pier models, five of which published in specialized literature. Data from tests carried out at LNEC for a pier model with dimensions closer to real situations than those of the other tested piers has been included in the data set.
The three prediction models lead to deviations between predictions and observations depending on the pile cap position relatively to the initial bed level; mostly, the higher deviations occur when the pile cap is partially buried in the bed. Given the deviation analysis results, it can be concluded that FDOT method has a lower probability for under predictions, meaning that this is the method that gives safer predictions for a larger percentage of situations that can be found in engineering practice.

Keywords: Bridges in riverbeds, local scour, complex piers, scour depth prediction.

 

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