13 th World Conference on Earthquake Engineering Vancouver, B.C., Canada August 1-6, 2004 Paper No. 918 EARTHQUAKE RESISTANT STRUCTURES OF PORTUGUESE OLD ‘POMBALINO’ BUILDINGS Rafaela CARDOSO 1 Mário LOPES 2 Rita BENTO 3 SUMMARY Portuguese ‘Pombalino’ masonry buildings were built mainly in Lisbon Downtown after the 1755’s Lisbon Earthquake. The conception of these buildings included anti-seismic provisions, which are described in this paper. One of the most relevant provisions is the inclusion of an interior three-dimensional braced timber structure named ‘gaiola’ enclosed in masonry walls above the first floor aiming at providing resistance to horizontal forces. Seismic assessment of one representative ‘Pombalino’ Building is discussed, where the influence of ‘gaiola’ walls in its seismic behavior is referred. The expected collapse mechanism of ‘Pombalino’ buildings is discussed, as well as usual strengthening solutions. Seismic assessment of these buildings is discussed based on their actual conservation state and on structural changes on the original structure. INTRODUCTION The Portuguese territory is a seismic prone region. One of the most destructive earthquakes in the history of this country is the Earthquake of the 1 st November of 1755. It was a strong earthquake (estimated Richter Magnitude 8.7) and epicenter in the Atlantic Ocean, at approximately 250km south of Lisbon. The 1755 Earthquake destroyed large areas in Lisbon and Algarve, the southern region of Portugal. In Lisbon, the Earthquake was followed by a tsunami and a fire was out of control for several days, as illustrated in Figure 1. Lisbon Downtown, near Tagus River, was the most destroyed area of Lisbon and was rebuilt following a urban plan. The need of a fast rebuilt and the fear of another earthquake led to the enforcement of new construction rules based on the experience learned from the collapsed buildings due to the earthquake, aiming at providing seismic and fire resistance to the new 1 Research Assistant, ICIST, DECivil, IST, Lisbon, Portugal. Email: rafaela@civil.ist.utl.pt 2 Assistant Professor, ICIST, DECivil, IST, Lisbon, Portugal. Email: mlopes@civil.ist.utl.pt 3 Assistant Professor, ICIST, DECivil, IST, Lisbon, Portugal. Email: rbento@civil.ist.utl.pt