Evaluating effectiveness and optimum design of isolation devices for highway bridges using the fragility function method

Dynamics of Structures: Theory and Applications to Earthquake Engineering by Anil K. Chopra

Benchmarking railway vibrations – Track, vehicle, ground and building effects

An update state-of-the-art review of the behaviour of isolated bridges to seismic excitation is presented. The review includes the literature on theoretical aspects of seismic isolation, parametric behaviour of base-isolated bridges and experimental studies to verify some of the theoretical findings. A brief review of the earlier and current base isolation devices, proposed or implemented, is given, and aspects for future research in the area of isolation of bridges are included.

http://www.ejse.org/Archives/Fulltext/200301/08/20030108.pdf

Seismic behavior of isolated bridges: A-state-of-the-art review

[1] The seismic signals of hundreds of rockfalls within Dolomieu crater, Piton de la Fournaise volcano, Reunion Island, have been analyzed to investigate a possible link between physical rockfall-generating processes and associated seismic signal features. Moreover, indirect observation of rockfalls via the seismic signals they generate can provide useful data for studying volcanoes and the temporal variations of their structure. An increase in the number of rockfall events and their volumes might be an indicator of structural weakness and deformation of the volcano associated with potential eruptive activity. The study focuses on a 10 month period following the 6 April 2007 crater floor collapse within Dolomieu crater, from May 2007 to February 2008. For granular flows a scaling law is revealed between seismic energy and signal duration. A semiempirical approach based on both analytical analysis and numerical simulation of these flows shows that a similar scaling law exists between the difference of potential energy computed for an event and its propagation times and also emphasizes the effect of local topography on this scaling law. Simulated and observed data were compared to evaluate the proportion of potential energy dissipated in the form of seismic waves and confirm a direct link between the seismic energy and potential energy of a given granular flow. The mean ratio of seismic to potential energy is of the order of 10−4, comparable to the range of values observed in previous studies. A simple method based on these ratios is proposed to estimate the volumes of rockfalls from their seismic signal. Observed seismic energy and the frequency of rockfalls decreased at the beginning of the studied period and reached a stable level in July, thus suggesting a postcollapse relaxation time of Dolomieu crater structure of about 2 months from seismic signal analysis, which is confirmed by deformation data. The total rockfall volume over the study period is estimated to be 1.85 Mm3.

/pdf/slope-instabilities-in-dolomieu-crater-reunion-island-from-3ekn7obvh4.pdf

Slope instabilities in Dolomieu crater, Réunion Island: From seismic signals to rockfall characteristics

Prediction model for low frequency vibration from high speed railways on soft ground

A semi-empirical model for predicting low frequency vibration that may annoy building occupants in areas with soft ground conditions has been developed and used for the planning of a new high speed railway line in Norway. The model has a statistical formulation, and predicts both expected values and confidence limits for the vibration. The model is based on a large number of vibration measurements in Norway and Sweden. To manage the systematic and unified handling of the measured vibration data needed to develop the model, a database has been defined and established. It is hoped that more institutions could agree on using one common data structure and start data interchange. This would make more data available for continued improvements of empirical prediction models and for validation of numerical vibration simulation codes.

Earthquake response of a base-isolated bridge subjected to strong near-fault ground motion

The road along the Oshli ´ð hillside in the West Fjords region of Iceland is one of the most hazardous roads in Iceland due to avalanches, rockfalls and debris flows. The road has little traffic, but nevertheless traffic accidents caused by the severe conditions at the site are common. A number of avalanche tracks are found on the hillside. In some of these tracks, avalanches occur more frequently than in others. When there is an avalanche threat, avalanches generally flow over many tracks in a short time. Monitoring vibrations in the tracks with the highest avalanche frequency can indicate when avalanches start flowing down the hillside in a snowstorm, and avalanche hazard can then be declared with the specific site indicated. The same methodology can be used for rockfalls and debris flows, which are strongly affected by weather conditions and typically occur in clusters. Based on this knowledge, a research project was initiated in February 1996 with the objective of developing an automatic system based on seismic measurements to detect and analyze avalanches on the Oshli ´ð hillside and to instantly

/pdf/automatic-detection-of-avalanches-and-debris-flows-by-26muxbbvr7.pdf

Automatic detection of avalanches and debris flows by seismic methods

Multichannel analysis of surface waves (MASW) is a fast, low-cost, and environmentally friendly technique to estimate shear wave velocity profiles of soil sites. This paper introduces a new open-so...

/pdf/tool-for-analysis-of-multichannel-analysis-of-surface-waves-3dr5uu1ns3.pdf

Bjarni Bessason

Papers

Prediction model for low frequency vibration from high speed railways on soft ground

Prediction model for low frequency vibration from high speed railways on soft ground

Earthquake response of a base-isolated bridge subjected to strong near-fault ground motion

Automatic detection of avalanches and debris flows by seismic methods

Tool for analysis of multichannel analysis of surface waves (MASW) field data and evaluation of shear wave velocity profiles of soils