Shake Table Tests: France

Through a collaborative European project (Univ. of Roma 1, Univ. Of Sheffield, Univ. of Patras and Ghent University) shaking table tests were performed at the CEA (October-November 2004), The objective was to investigate two types of strengthening strategies (retrofits) and techniques on a seismically under-designed R/C frame structure: a) FRP strengthening, and b) Two types of viscous dampers (shown in blue or yellow). This research was triggered by the collapse of a school in an 1998 earthquake in Italy (in which there was a large number of fatalities), and aimed at the development of simple design equations.

Two series of tests were performed: a) 5 seismic tests from 0.05 g to 0.4 g on original frame; b) 6 seismic tests and 5 sine sweep tests on the retrofitted frame. Retrofitting was performed with FRP by the Freyssinet company.

The first series of tests (without retrofit) were mostly localized around the nodes of 1st and 2nd level. The 1st natural frequency dropped from 1.9 Hz to 0.68 Hz. Following retrofitting, the natural frequency increased to 1.4 Hz, and dropped back to 0.68 Hz after the second series of tests. Damages under FRP strengthening (split) were visually observed at the base of column 1, 2 and 4. There were also some indications of initial diagonal tearing of FRP strengthening at the first level in one of the columns. Similarly, it was determined that use of the simple viscous dampers greatly improved the seismic response of the structure.

Specimen tested on CEA's shake table with and without RPF retrofit, with (and details of) two sets of dampers.