During the E-ELT Dome and Foundations FEED Study, IDOM developed a Base Control System for protection of the
E-ELT Main Structure against the effect of high level earthquakes. The proposed design was aimed to provide an
effective isolation during heavy seismic events, whereas in normal observation conditions it presented a high stiffness to
avoid interferences with the pointing accuracy of the telescope.
In a subsequent phase, a representative prototype was envisaged by IDOM, in close collaboration with GERB, to
evaluate the performance of this system, correlate the results from prototype testing with the behaviour predicted by a
calculation model and finally validate the design conceived during the FEED Study.
The assessment of the results from the prototype tests has been focused on checking the level of compliance with the
demanded requirements: 1) the Base Control System isolates the upper structure from ground in case of high magnitude
seismic events; 2) in operational conditions, the system -by means of Preloaded Devices (PLDs)- provides a stiff
interface with the ground; 3) regarding the performance of the PLDs, the finite element model simulates accurately the
non-linear behaviour, particularly the zero crossing when the direction of the excitation changes; 4) there is no
degradation of the stiffness properties of the seismic devices, after being submitted to a heavy seismic event.
The prototype was manufactured by GERB and pseudo-integrated tests were performed on a shaking table at the
premises of the Institute of Earthquake Engineering (IZIIS) in Skopje, Macedonia.