• Document: EARTHQUAKES AND REABILITATION OF OLD MASONRY STRUCTURES: A VIEW ON THE WORLD PRACTICE
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Conferência Internacional sobre Reabilitação de Estruturas Antigas de Alvenaria EARTHQUAKES AND REABILITATION OF OLD MASONRY STRUCTURES: A VIEW ON THE WORLD PRACTICE SISMOS E REABILITAÇÃO DE ESTRUTURAS DE ALVENARIAS NO MUNDO ACTUAL CARLOS SOUSA OLIVEIRA Prof. IST, Researcher, ICIST/IST csoliv@civil.ist.utl.pt Extended Abstract Earthquakes for a long time have caused great damages in old masonry construction as buildings, monumental structures, bridges, etc. Recent earthquakes in the 21st century, such as Kashmir (Pakistan) 2005, L´Aquila (Italy) 2008, Shichuan (China) 2008, Port-au-Prince (Haiti) 2009, Maule (Chile) 2010, Christchurch (New Zealand) 2010 and Van (Turkey) 2011 have confirmed this trend. The 20th century is full of cases of great destruction to the masonry stock, causing a great number of casualties (hundred thousand), heavy injuries (many hundred thousand) and millions of homeless. Even in Portugal, earthquakes in the last century were responsible for the great damage caused in 1909 in the Continent and in 1926 (Faial), 1973 (Pico), 1980 (Terceira) and 1998 (Faial) (Azores). Of course not only old masonry structures (MC) have suffered from the strength of earthquake ground shaking. Reinforced concrete structures (RC), especially the structures built until the modern codes came into practice, i.e., mid 1980´s, suffered quite severely in many instances due essentially to either bad detailing of construction and under defined seismic action. Even nowadays, in more technological advanced countries, problems may arise due to lack of control in the implementation of new seismic codes. We can say that research in RC and steel construction have gone through great developments and if on the part of ground motion there are no “surprises”, the seismic performance of these typologies are very much under control and modern codes have been able to tackle well with these loads. The Japan March 11, 2011 is the best “experiment” to ascertain these statements. With so much damage caused by the tsunami, the behavior of the RC stock was quite good given the long and strong ground motion subjecting those structures. The same can be said about the Chilean and the New Zealand earthquakes, but not for Italian or Turkish earthquakes (and Lorca, Spain 2011), where modern RC brick infill structures suffered quite severely. In respect to this topic it is now the right time to refer that definition of ground motion has been one of the most critical issues responsible for some of the past great disasters. In fact, in many instances, earthquakes have occurred in locations where responsible authorities for setting code provisions did not act in the best way, or by neglecting historical lessons (case of March 11 2011 Japan Tohoku earthquake and tsunami, Haiti, 2010), or by under predicting seismic action as the cases of blind faults nearby populated areas (Sichuan, Athens 1999, etc.). Each time a new event occurs there is always something new to learn or to confirm, theories to validate or reject, models to upgrade, ideas to renovate, policies to rethink. The most recent case of Japan earthquake is full of new information which will definitely change the way earth science, earthquake engineering, social-economical sciences and earthquake management are being taken by the world most advanced earthquake communities. Similarly to what has happen with the 1755 earthquake which caused a great revolution in all those fields including philosophical theories established up to the 18th century, the Japan earthquake of 11 March 2011 will be a mark on the World Society in the way those sciences deal with unexpected events of such great impact. Questions such as how to use urban spaces in danger of futures tsunamis that may occur with a very low probability, which level of ground motion to use in connection with retrofitting of structures, effects of very long duration of motions (only reported on historical eyewitnesses accounts and never looked nowadays) on steel or concrete, masonry and geotechnical structures, are among the important issues to be discussed in the future to correct present-day practices. The situation in the World (existing construction) Figure 1 presents the World-Wide damage distribution in the 20th century by geographic regions and by structural type. It is clear that the masonry buildings 111 International Conference on Rehabilitation of Ancient Masonry Structures Fig 1. Distribution of World-Wide damage in the 20th century by geographic regions and by structural type. (in M. Lopes Editor, 2008). Elements for characterizing the situation in Portugal The situation in Portugal with respect to construction is of great apprehension as far as earthquake safety is concern, as still t

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