SEISMIC BASE ISOLATION: RETROFITTING APPLICATION IN STRUCTURES DAMAGED BY EARTHQUAKE

The ever-increasing use of the most advanced seismic protection technologies in structural design can often lead to unexpected results in terms of system efficiency, expexially when the application of technologies is not carried out by satisfying some simple concepts derived from other branches of engineering. Both anti-seismic isolation devices and their correct application in existing structure can lead to a decrease in the safety level in structures with base isolation respect to less innovative anti-seismic technologies in conventional structures. The work presents some critical features in the existing structures with seismic isolation, and the proper controls that the test should highlight to avoid problems in the correct application of the technology, to obtain a real seismic security higher than that of traditional structures. After L’Aquila 6,3 Mw earthquake of 2009, April 6th, about fifty percent of the buildings in the city were severely damaged. Its historical centre and all the surrounding suburbs were severely damaged, causing 309 casualties, and more than 1500 people injured. L'Aquila has been the first Italian important city directly destroyed by a near fault earthquake since Messina earthquake (1908). Many buildings collapsed completely, both in masonry structure and in reinforced concrete ones. Innovative anti-seismic techniques are illustrated, mainly the base isolation anti-seismic systems. Some examples of application in existing building damaged by L’Aquila earthquake (2009) in Italy are shown, demonstrating how the isolation techniques can be applied in concrete structure and even in masonry structure, diminishing the vulnerability level in both cases. Several additional control phases must be applied, regarding the seismic gaps permitting the building movement during earthquakes