Buildings from the sixties and seventies on the Alicante coast do not resist the shock of an earthquake
UA/DICYT The University of Alicante Research Group in Structure Essay, Simulation and Modelling (GRESMES), led by Professor Salvador Ivorra Chorro, has recently published in the journal Engineering Failure Analysis the study Seismic behavior of 1960's RC buildings exposed to marine environment in which they analyse in depth some buildings located on the coast of Alicante, built in the sixties and seventies, concluding that these properties will not resist the effect of an earthquake.
The scientific study focuses on the analysis of some reinforced concrete buildings located on the Alicante coast. However, as Ivorra Chorro confirmed, "it is something that happens, more often than not, among the buildings on the Mediterranean coast, particularly in Alicante". They are 15-floor buildings from the 1960s and 70s. In that period, quake-proof building regulations were known but not applied. Buildings at that time were constructed without taking earthquakes into account or the action of the wind, which causes concrete and steel to deteriorate to a greater extent due to airborne sea salt. The expert highlights the reduced quality of the materials with which they were built. According to current measures, these properties are not strong enough to resist an earthquake. It is noteworthy that these buildings were constructed without considering possible seismic actions which, since the 70s, is mandatory in the Alicante area.
The working team, made up of engineers and architects belonging to GRESMES, from the UA Civil Engineering Department, has made use of the maps provided by the Alicante City Council. They have verified that these maps correspond to the buildings constructed and, following that, they have built a calculation model to provide evidence of the deterioration that would occur to both the original building and the building to date in the event of an earthquake. In neither case can the buildings resist an earthquake.
Reinforced concrete buildings are designed to have a useful life of fifty years with the current regulations. After fifty years of life, they will begin to have more problems, although they will not fall down immediately, the professor stated. Depending on the aggressive agents to which the buildings are exposed, their life cycle can be extended or shortened. According to Salvador Ivorra, a large part of the buildings on the Alicante coast were built in the 60s and 70s with “good” materials at that time, although with limited durability requirements and earthquake proof measures. The UA study reveals today’s high vulnerability of all these buildings.
In seaside buildings, a high degree of deterioration is usually observed as a consequence of corrosion of steel reinforcement inside concrete. Depending on the proximity to the sea and exposure, these levels might be higher or lower, leading to a considerable reduction in structural safety conditions. The effect of corrosion can be seen in cornices, balconies, railings, etc. and emergency repair works must be carried out to prevent detachments. Damage to these external elements leads many owners associations to take action in the repairs of this type of buildings, not only aesthetically, but also structurally, in not always the best way. Also, in refurbishment of low structures, coatings are removed and pillars show signs of high deterioration with a low resistance capacity.
The study carried out by GRESMES analyses in depth some buildings located on the coast of Alicante, taking into account their original structure, the actions considered originally (mainly their own weight and use overload), construction details and evolution of corrosion. Experts have firstly assessed the evolution of concrete carbonation and after that, the steel reinforcement section loss, considering at all times the qualities of structural materials of the time (the 60s and 70s), which were much lower than those used with current designs, even in high-performance buildings of that time. Researchers emphasise that these buildings were constructed without considering possible seismic actions which, since the 70s, is mandatory in the Alicante area.
Once the current situation of reinforced concrete and its resistant capacity have been analysed after more than 40 years of service, experts have constructed a numerical model to simulate the behaviour of buildings with a number of extraordinary actions, including the impact of a possible earthquake. Once the structure has been analysed in both the original project and today’s conditions, researchers have provided evidence that in neither of the two cases could it resist an earthquake. The construction features the provisions of beams and pillars are some of the aspects that avoid these buildings to be earthquake-resistant. The UA professor can certainly say that these buildings will not resist the impact of an earthquake.
The conclusions of the scientific study reveal that a comprehensive technical inspection in buildings is required to analyse the degree of deterioration and perform the necessary intervention and reinforcement to ensure structural safety, both for regular and special actions.
Salvador Ivorra Chorro is a university professor in the area of Continuum Mechanics and Structure Theory at the University of Alicante's Department of Civil Engineering, where he coordinates the Structures Laboratory. He is the leading researcher of the Group in Structure Essay, Simulation and Modelling and deputy director of the Department mentioned above. He holds a PhD in Industrial Engineering (Mechanical Engineering) from the Polytechnic University of Valencia. Since January 2017, he has been the project manager of the Spanish State Plan for R&D+i in the Construction area of the Spanish State Research Agency. His research activity has been focused on the dynamic behaviour of structures and structural reinforcement, and he has devoted an important part of his research to the structures belonging to our historical heritage.
David Bru, Antonio González, F. Javier Baeza, Salvador Ivorra, Seismic behavior of 1960's RC buildings exposed to marine environment, Engineering Failure Analysis, Volume 90, 2018, Pages 324-340, ISSN 1350-6307. https://doi.org/10.1016/j.engfailanal.2018.02.011.