REPSODY: Response of Soils, Sites and Structures to dynamic stresses - Earthquakes and vibrations -

Risks in French regions are increasing due in particular to artificialisation of land and also climate change. These phenomena must be taken into account in development, infrastructure projects and adaptation of public policies. There are major challenges on the human, material and economic levels. Whether on the scale of cities or more generally at a national level, population and population density are constantly increasing.

Improvement of knowledge about natural phenomena and consideration of the consequences of increasing exploitation of regional resources are absolutely vital areas of study today, in order to attempt to improve protection and resilience against these risks. The REPSODY team proposes to contribute to improving knowledge about the vulnerability and exposure of buildings and civil engineering and geological structures with regard to seismic and vibration risks.

Recent disasters such as in Haiti (2010), Japan (2011, 2016), Nepal (2015), and Italy (2009, 2016) regularly remind us of the need for knowledge about this risk, in order to manage it more effectively. Prediction of movements likely to occur on the ground’s surface enable civil engineers in the long term to dimension their structures in accordance with earthquake resistance standards and to define seismic micro-zoning for normal and listed buildings. It is indeed vital to take account of all the physical phenomena involved: from the fault to the response of the built environment and its interaction with the surrounding ground. The aim is to better understand the most complex phenomena (some of which are still not fully known) using various methods and scales of work.

When characterising a seismic risk, it is necessary, in addition to characterising the hazard itself, to evaluate the seismic vulnerability of geological systems and built structures. In this context, seismological recordings on different scales (earthquake, micro-earthquake, background noise) contribute directly to characterising this vulnerability over a period of time. For example, geophysical measurements based on recordings of seismic background noise are being used increasingly to characterise and monitor unstable geological masses and Railway Engineering structures. New signal processing techniques adapted to these types of object also need to be investigated.

There is also an increasing need to take account of man-made vibrations generated during construction and operation of infrastructures, in an environmental context that is changing considerably, and where the urban fabric is becoming more and more dense. Due to the possible effects of vibrations on existing buildings we have to take into consideration different types of potentially harmful dynamic loads, and to represent them accurately using recently designed tools. In addition, recording of vibrations and their variation over a period of time is the basis for new structural inspection technologies. They detect anomalies in time series of collected values which are then compared to initial values, often associated with satisfactory condition of the monitored structures.