Spanish building sector professionals are not still aware of the fact that Spain is a seismic country. Urban regulations determine a building’s volume enclosure without any seismic resistant design planning. They consider earthquakes as acting on single pieces of the system: buildings, rather than on the real seismic scenery: the city.
Worldwide, seismic building codes are written for engineering application, rarely accompanied by guidelines related to architectural or urban features, even modern cities enforce the use of certain irregular building configurations such as set-backs, soft first stories, adjacencies, etc (1).
Experience indicates the well known high vulnerability of these configurations but they are still present today worldwide. Every time an earthquake strikes a contemporary city, reports about the damage show that these configurations are not recommended in seismic places, but nobody pays attention. The first stories of buildings are mostly used for social events, parking, commercial and business purposes, and other activities that require layouts free of walls (2).
Our modern lifestyle also means an increase of movement and speed; maybe we are now living on a non seismic area, but sooner or later, be it working, visiting, enjoying holidays, or otherwise, we will put our feet down on a seismic location. Are we really ready to do it? The answer is NO! L'Aquila and Lorca are witnesses to it.
1. INCORRECT URBAN PLANNING
Urban regulations in cities located in seismic zones, as Lorca is in Spain, usually do not include special seismic provisions, and are just the same as those located in non-seismic-prone areas. The NCSE02 code needs urgent revision: nine people died in Lorca, none of them due to structural collapses. Geotechnical matters such as the influence of local ground amplification should be reconsidered. Buildings with reinforced concrete structures but with set-backs, short columns, ground soft story, or incorrect anchoring of the non-structural elements, are examples of existing architectural configurations unsuitable for a correct seismic behaviour, and lots of cities worldwide are in the same situation. The earthquake that ravaged the Italian town l’Aquila evidenced that other European areas share the same risks.
|SANTA MARIA DE LAS HUERTAS SANCTUARY SERIOUSLY DAMAGED|
SANTA MARIA DE LAS HUERTAS SANCTUARY SERIOUSLY DAMAGED
Actions should be taken in order to prevent similar effects in historical places with the same tectonic situation: Granada, Córdoba, Murcia, Alicante, Torrevieja..., which are potentially laying on the same risks: closer active faults, on grounds capable of doubling or even tripling the power of seismic waves.
|SANTA MARIA DE LAS HUERTAS SANCTUARY|
Spain is the country with the second most important number of National Heritage sites in the world, behind Italy and ahead of China. It seems both appropriate and necessary to make an investment in the future of Spain, one of the most important countries in the World regarding cultural tourism and still not developed enough. Sadly some of our leaders still are unaware of it. Spanish Heritage (historical, artistic, architectural, landscape, gastronomic and so on) should be promoted to the highest post in the scale of priorities, those regions with the most important cultural or historical richness should be provided with special plans related to seismology and heritage preservation. Possibly, one of the most ambitious tasks to assume in future days may be the reinforcement of churches, palaces, convents, castles, etc., like those now painfully damaged in Lorca, as well as to foresee their behaviour during an earthquake, like the one that shook Lorca, on Wednesday, the 11th of May.
LORCA: THE MORE DENSE BAROQUE CONCENTRATION IN EUROPE, THE WORST CULTURAL HERITAGE DISASTER IN EUROPE SINCE THE 1997 EARTHQUAKE THAT STRUCK ASSISI IN ITALY
3. PEOPLE IN EUROPE ARE NOT TRAINED FOR SEISMIC EVENTS
|ARE PEOPLE IN EUROPE PREPARED ?|
|THE ANSWER IS: NO!|
4. WHAT ABOUT THE GEOTECHNICAL RESPONSE OF THE GROUND?
It is also important to underline the fact that Lorca is a very rich geotechnical site, with regards to the soil textures and specimens. The Guadalentín River and all its sediments form a cuvette capable of amplifying the seismic waves, doubling or tripling their magnitude, as seen. Due to the fact that part of these materials can be qualified as collapsible, the consequences are difficult to foresee. The year before, the FAM (Alhama de Murcia Fault) was in an inter-seismic period with no activity, thus, it was quite predictable that something was going to happen; some tectonic experts even announced it. The unexpected issue was not the earthquake itself but the top basic acceleration measured (0,41g).
5. URBAN PLANNING AND GEOLOGICAL MICROZONING: TWO OPPOSITE DIRECTIONS
Tectonic and/or seismic research should be coordinated with micro-zoning and urban planning development, in order to make the location, volume, number and height of buildings as well as their other significant characteristics consistent with the geological and seismic ground information available. Furthermore, urban development of areas with high seismic risk should require the previous elaboration of local maps, including among other natural risks, the seismic risk. Urban designers and city planners, created from the 19th to 20th centuries a new architectural and city planning paradigm that guided the evolution of contemporary cities, all around the world, in the opposite direction of geologists advices and risk researchers, which is still present nowadays.
NCSE 02 CODE has proved to be very effective regarding structural elements, but needs to be revised and completed, in reference to: Constructive non-structural elements, such as, parapets, cornices, installations, partitions and others: there is a lot to do regarding their design, location, anchorage, flexibility, etc. There is also an obvious need for reinforcing masonry walls, either made of bricks or of stone in those places where they are traditionally used. Local seismotectonic zoning is required, above all in zones where it is well known that seisms of the L’Aquila or Lorca type could happen in the future. New maps are required, as well as new approaches to the response spectrums from waves generated by the activity of shallow or superficial faults. It is urgent too, to revise the values of the contribution coefficient k after the experience in Lorca.
An increase of the basic acceleration values of the zones close to active faults is needed, especially in towns in line with the ones already identified with recent activity, and in the future, with those to be discovered. Major investigation, study and consideration of all the layers of the ground affected by foundations which may receive seismic waves is needed. The code classification in types I, II, III and IV is too vague and indeterminate to prevent structural damage due to geotechnical reasons.
Real geotechnical effects should be considered, revising the C coefficient associated to the ground. It is not enough to quote the possibility of liquefaction of granular soils, there is a wide range of deflections not considered in NCSE 02, such as collapses, densifications, reactivation of consolidations, etc., either in soil or in rock. Part of the new text to include as an extension of the in force code should have a geotechnical and geomechanical character according to the effects on buildings and infrastructures.
The appearance of new seismic zones should also bring about the exigence to adapt, as far as possible, the existing buildings to this new code. The Spanish Technical Building Code (CTE) included two important new concepts: the need to guarantee the safety requirements of structures, not only in the design phase but also during the execution phase, and while the building is in use. Also, it underlines the requirement of maintaining buildings properly in order to guarantee their performance and behaviour during their useful life.
This essential requirement is very important for seismic-resistant structures of existent buildings, that could have been designed complying with former codes. It is absolutely necessary to extend the Technical Buildings Inspection (ITE), already in force in many cities in Spain, to the whole country, with a special emphasis upon those structures in high seism risk areas. That would be the best option to reach our goals.
6. THE LESSONS LEARNT
Lorca should become an in situ research laboratory for the whole of Europe. Earthquake consequences require a much deeper and extensive multidisciplinary analysis, in order to establish the lessons-learnt for seismologists, geologists, engineers, architects and stakeholders. It is never too early to achieve final consistent conclusions about seismic events an their consequences in Europe, we are in time to point out a series of striking combined causes, if we are clever they can be a source of knowledge and wisdom.
In Spain, we have the first opportunity to apply the content of the NCSE02 article 1.3.3 after being classified VII-VIII, in such an extended area. The content is this: “...after a high intensity seism, a report of every construction located in areas with intensity equal o higher than VII (EMS scale) should be drafted, in order to analyze the consequences of the earthquake on it, as well as to determine the kind of measures to be taken in relationship. The author of the report should be the technical expert responsible for the maintenance, or if there was not one, the proprietor or legal owner of the construction...”.
Actions must be taken in order to raise public awareness. It is essential to raise the awareness of the population in general, especially the building sector, regarding the existence of areas highly vulnerable to earthquakes in the Spanish geography. The time has come to determine the preventive actions to be adopted as well as to plan all the procedures to follow in case of a high magnitude seism’s striking. These two should be the main objectives to be promoted by the administration, as well as the transmission of a clear message: Spain is a country with seismicity capable of killing and injuring people, seriously damaging buildings, infrastructures or heritage, or even paralyzing the whole economic activity of the second largest region in the country.
WHAT HAPPENED TO LORCA?
7. CONCLUSION: EUROPE IS STILL PARALYZED (AMONG OTHER QUESTIONS) WITH REGARDS TO SEISMIC EVENTS
A final reflexion to highlight, regarding what Lorca suffered last May or l’Aquila in 2009, once more, is that reconnaissance reports, published shortly after every earthquake strikes contemporary historical cities all around the world, always describe failures in buildings’ configurations identified in codes as non-recommended in seismic zones.
|LEARNING TO SURVIVE|
And, of course, people's behaviour before, meanwhile and after a seismic event. A minimun seismic culture correctly trained will be enough for an implementation of autoprotection philosophy, and a benefit for both the individual and community, and most of all, it will save lots of lives across Europe. A necessary lesson to be learnt from childhood. Spanish, and almost all European people are illiterate in this regard. So we technicians, must call our neighbors to awareness, especially after the l’Aquila and Lorca events: Let's go Europe...!
Lorca, Wednesday May 11 2011
(1) (2) L. Teresa Guevara-Pérez SEISMIC REGULATIONS VERSUS MODERN ARCHITECTURAL AND URBAN CONFIGURATIONS
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