Integral abutment bridges: Investigation of seismic soil-structure interaction effects by shaking table testing

In recent years there has been renewed interest on integral abutment bridges (IABs), mainly due to their low construction and maintenance cost. Owing to the monolithic connection between deck and abutments, there is strong soil-structure interaction between the bridge and the backfill under both thermal action and earthquake shaking. Although some of the regions where IABs are adopted qualify as highly seismic, there is limited knowledge as to their dynamic behaviour and vulnerability under strong ground shaking. To develop a better understanding on the seismic behaviour of IABs, an extensive experimental campaign involving over 75 shaking table tests and 4800 time histories of recorded data, was carried out at EQUALS Laboratory, University of Bristol, under the auspices of EU-sponsored SERA project (Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe). The tests were conducted on a 5 m long shear stack mounted on a 3 m × 3 m 6-DOF earthquake simulator, focusing on interaction effects between a scaled bridge model, abutments, foundation piles and backfill soil. The study aims at (a) developing new scaling procedures for physical modelling of IABs, (b) investigating experimentally the potential benefits of adding compressible inclusions (CIs) between the abutment and the backfill and (c) exploring the influence of different types of connection between the abutment and the pile foundation. Results indicate that the CI reduces the accelerations on the bridge deck and the settlements in the backfill, while disconnecting piles from the cap decreases bending near the pile head

Análise da informação geológico-geotécnica dos maciços graníticos ao longo dos trechos enterrados do metro ligeiro do Porto

O Metro Ligeiro do Porto é uma das obras públicas de maior dimensão em Portugal envolvendo uma rede de cerca de 70 km. A parte enterrada compreende 11 estações, sendo 5 por técnicas mineiras e 6 do tipo cut-and-cover, e dois túneis por tuneladoras TBM-EPB. A sua construção tem levantado problemas, sobretudo relacionados com a heterogeneidade dos maciços graníticos atravessados. Os problemas envolvidos têm conduzido a preocupações acrescidas na caracterização dos maciços e na selecção das tecnologias construtivas. A prospecção geotécnica tem-se baseado na recolha da informação de campanhas de sondagens e ensaios, o que permitiu o estabelecimento, na fase de projecto, de classes geomecânicas e respectivos parâmetros definidores. Na presente comunicação, são apresentados resultados da análise das campanhas geotécnicas efectuadas e de correlações estatísticas entre parâmetros. Está em desenvolvimento um sistema computacional com utilização de técnicas de inteligência artificial, tendo em vista a caracterização de parâmetros geomecânicos para a modelação de obras subterrâneas em maciços graníticos. Fez-se uma aplicação do sistema para maciços rochosos graníticos com vista à comparação dos resultados com os grupos e parâmetros geomecânicos adoptados no projecto

Habit Formation, Incomplete Markets, and the Significance of Regional Risk for Expected Returns

This paper introduces a consumption-based capital asset pricing model (CCAPM) that combines undiversifiable income shocks and external habit formation. Using US state-level data, the paper provides realistic estimates for preference parameters when the external habit of the state investors is based on the consumption of the four Census regions. The model also implies four asset pricing factors: the cross-sectional means of consumption growth and habit growth (capturing national systematic risk) and the cross-sectional variances of consumption growth and habit growth (capturing regional systematic risk). This four-factor model has greater power in explaining expected returns than the CCAPM described in Breeden (1979)

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved