Tuesday, November 24

Half of the 50-year-old buildings facing the sea are vulnerable to an earthquake


General view of buildings built facing the sea in Albufereta, many of which are over 50 years old.

General view of buildings built facing the sea in Albufereta, many of which are over 50 years old.
RAFA ARJONES

About half of the buildings with More than 50 years old built in the first line of the sea in localities like Alicante, San Juan, El Campello, Elche, Santa Pola, and the rest of the coastal municipalities of the province, built in the 60s and 70s of the 20th century, are in risk of harm in case of receiving the impact of a magnitude 6 earthquake on the Ritcher scale, because in their day they got up using bad materials, those of the time on the other hand. A report from the research group on Simulation, Modeling and Testing of Structures of the University of Alicante warns that buildings have become vulnerable in the event of an earthquake from six degrees, and the experts demand your review.

The cause is the deterioration of their structures of concrete, some raised with bad materials and very subject to erosion caused by the wind and saltpeter. Furthermore, they were built without anti-seismic regulations in force, simply because they were not required. “The buildings are not going to fall, but they need a technical revision”, alert Salvador Ivorra, professor director of research. Although problems in balconies and overhangs are usually detected, the pillars on the ground floors are usually the most critical elements.

Fundamental is that communities of owners are aware that the properties must undergo the mandatory technical inspection regulated by the Consell when the building turns 50 years old. There are even municipalities like Santa Pola, which have already cut the review period to 40 years. The province of Alicante is considered a medium risk area regarding the possibility of suffering a earthquake and in fact, earthquakes occur every day most of them mild, between one and four degrees on the Ritcher scale, but experts do not rule out that 6-degree Ritcher earthquakes such as the one that shook Torrevieja in 1829 could occur again, leaving almost 400 dead.

These are buildings of 15 floors or more, exposed to damage from earthquakes of more than 6 degrees

“As for the most vulnerable buildings, those we have studied would suffer significant damage with magnitudes greater than six for two reasons. The materials with which they were built have been damaged by the effect of corrosion due to the salt content of the sea breeze, and then they did not have the current qualities, “says Ivorra.

The professor at the University of Alicante and specialist in Structures maintains that in some cases very invasive interventions are necessary that would imply that the construction was out of use for a long period of time, since it would be necessary to incorporate new beams or even the inclusion of structures to absorb lateral loads generated by the earthquake.

«There are countries that have chosen to raise external structures that allow to strengthen the building, improve the power dissipation capacity against earthquake and, at the same time, with a good design, improve its energy efficiency. This intervention would completely change the aesthetics and would only be possible if there is space on the plot and that urban legislation allows it, ”Ivorra emphasizes. The professor admits that the problem is difficult to tackle.

«The first thing is to know the current situation and check the state of conservation of each and every one of the buildings in a municipality and propose, if necessary, the intervention to ensure their integrity with respect to the project actions. Next, a detailed analysis of each of the buildings should be carried out to know their level of seismic risk and analyze the economic viability of their adequacy, not only in the face of the earthquake, but including in the same intervention the update of the energy efficiency”.

Other interventions, especially in singular buildings, that have been proposed in other countries are, Salvador Ivorra explains, the use of base insulators. “They are devices that could be installed between the foundation and the pillars on the ground floor or at the top of these pillars under the slab on the first floor. They are technological solutions that isolate the building from the earthquake ».

The research team of the University of Alicante Group for Simulation, Modeling and Testing of Structures (GRESMES), led by professor Salvador Ivorra, published their study in the scientific journal Engineering Failure Analysis. The study has focused, in particular, on the analysis of some reinforced concrete towers located on the Alicante coast. «It is something generalized among the buildings of the Mediterranean coast and, specifically, in Alicante. Buildings of 15 floors or more ».

Towers with a lifespan of half a century

The buildings of reinforced concrete are designed to have a lifespan of 50 years. They were built with “good” materials of the time, but with low durability requirements and no earthquake-resistant considerations. In buildings close to the sea, deterioration is usually observed as a consequence of the corrosion of the reinforcements that exist inside the concrete. Depending on the proximity to the sea and its exposure, these levels may be higher or lower, even leading to a considerable reduction in its structural safety.

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