Seismic floor isolation using recycled tires for essential buildings in developing countries

Historical earthquakes in developing countries, particularly in South America, have caused devastating effects in essential buildings, such as hospitals. As a result, some structural retrofits and new designs of essential facilities in South American countries have concentrated on increasing the seismic design forces beyond what is normally required by building codes. This increased-strength approach can lead to quasi-elastic structural response during earthquakes with much larger induced floor accelerations than expected from code-designed structures. In critical structures, sub-par performance of critical non-structural elements, such as medical equipment in a hospital, due to high-induced floor accelerations can have consequences as devastating as structural failures. Passive seismic protection systems, such as seismic isolation, provide a practical means of controlling seismic demand and are now common in developed countries. However, the applications of protection systems have been far fewer in developing countries due to economic considerations and lack of technical expertise. This paper presents the experimental and numerical studies supporting the development of a novel low-cost sustainable protection system incorporating recycled automobile tires for isolating designated floors or rooms in essential buildings in developing countries. The main innovation of the proposed floor isolation system is the geometric arrangement of the rubber tires that allows isolation from both, horizontal and vertical floor accelerations. Horizontal and vertical cyclic testing conducted on tire specimens are first described followed by the development of a numerical model able to reproduce the experimental results. Finally, an existing case-study hospital in Ecuador is considered for evaluating numerically the seismic performance of the proposed floor isolation system.