After the recent Central Italy earthquake, you are probably asking yourself: is it still safe to buy a house in Italy? Are homes anti-seismic? And which interventions are necessary to make them earthquake resistant?

The answer is, living and owning a house in earthquake prone areas is possible, if done wisely.

But to know more about it, we have interviewed an engineer who works in Italy, an expert in this field, Luciano Augello from Design? Studio Associato. He will give us an outline of the situation in the country at the moment and will talk about earthquake proof and resistant building structures in Italy.

1. Engineer Luciano Augello, what is the situation in Italy from the seismic prevention point of view?

Italy’s anti-seismic norms regulating the design and construction of buildings are based on a national law from 1974 that established the criteria for seismic classification of the Italian territory and the creation of technical norms. These have undergone a slow evolution thanks to advances in the research and new studies. So the new code has been officially released in 2008 and took effect starting from July 1st, 2009. It probably will undergo a further update before the end of this year.

Well, Italy’s building heritage is mainly previous to these dates therefore not subject to precise anti-seismic norms. Up until today there is no obligation for interventions to adapt these properties to the present laws unless one decides to make structural works of a certain relevance like raising, enlarging or changing the destination of use of a property, etc. Nonetheless, a seismic retrofit of the majority of existing buildings is possible in order to make them more secure. It is necessary a preliminary “seismic vulnerability analysis” made by a technical expert to determine the flaws detected and the level of safety that can be reached (established together with the buyer), and the project for the necessary interventions aimed to reach a certain level of global and local seismic improvement of the building, where possible.”

2. What can be made to enhance the seismic resistance of an existing property in Italy?

The most common properties on the Italian territory are masonry structures (i.e. stones and bricks) for which there are several practicable interventions to improve their seismic performance. The choice of the techniques to apply and urgency of the intervention depend on the results of the “seismic vulnerability analysis”. In any case, it is possible to get an idea about the vulnerability conditions of your own house by gathering the following information:

✓ Year of construction;
✓ Building precedents or works that may have modified the original structure of the house;
✓ Plans of the building to evaluate the “regularity of the building” (rectangular, square or compact plans are preferable);
✓ The materials used to build load-bearing walls (e.g. if the walls are in bricks or stone, the vulnerability increases in case the material is heterogeneous in size and type and laid badly);
✓ The materials used to build the floor slab and roof;
✓ The presence of possible damaged patterns or possible excessive degradation of certain portions of the building;
✓ The presence of excessive loads on the floor slab (e.g. crawl spaces).

After this initial screening, a study of a detailed improvement and possible predisposition of a project for the interventions can be made together with an expert figure of your own choice. In general, the most frequent techniques applied to consolidate buildings in bricks or stone are the following, a single one or in a combination of two or more can be made:

building box behaviour

Repair of possible pre-existing damage and/or the reduction of the flaws due to gross errors;
Elimination of elements of great vulnerability on which nothing can be done;
Improvement of connections among structural elements – walls, floors, roofs – essential to build a unit with a “box behaviour”, that means guaranteeing an adequate stability and global resistance of the building thanks to a good anchoring between its main parts.
Proper connection devices are for example metallic or different material tie-rods which are stiffed in the walls at the floor level along the two principal directions of the structure, and anchored by means of rosehead washers bearing plates. They are able to implement the connection between walls and avoid/decrease the probability of out-of-plane failure.”

tie-rods
tie-rods in a property in Umbria

This is how tie-rods look like in this retrofitted home in Umbria:
Other techniques include the use of confining rings, tie beams, etc.
Improvement to reduce excessive roof deformability. In many cases this can be achieved by providing a further layer composed by wooden planks, with orthogonal direction with respect to the existing structure. The use of metallic belts disposed in a crossed pattern and fixed at the extrados of the wooden floor or the use of metallic tie-beams bracings may improve the stiffening effect.
Improvement of walls‘ mechanical characteristics through consolidation techniques or, when possible, their substitution. Some techniques are reinforced injections, insertion of diatoni (masonry units disposed in a orthogonal direction with respect to the wall’s plane) and cuci-scuci:

cuci-scuci

Reduction or elimination of the non-contrasted load of roofs, arches and vaults (use of chains);

vault chians

Possible improvement of the foundation system that can be achieved for example through enlargements and consolidations or the use of micropiles to support the structure. They increase their seismic performance and minimize the foundation deflection because of its high pullout and bearing capacity.”

3. How much does it cost to earthquake proof your house in Italy?

Earthquake retrofit cost for an existing property in Italy is established through a detailed analysis measuring of all the items foreseen by the structural intervention project. So it is quite difficult to establish a priori its cost because the work need to optimise an ancient building cannot be standardised. However, based on my experience, the cost of the interventions can vary indicatively between 30 – 100 €/m² for small repairs or “local interventions” (from small repairs to the substitution of a portion of floor slabs); 100 – 200 €/m² for interventions of seismic improvement (treatment of the walls to increase their mechanical characteristics, ductility in particular), and more expensive for more invasive and complex interventions of seismic adaptation. They are costs that can sometimes result comparable to construction costs of a finished anti-seismic building (planned according to the laws) or in some cases higher.”

Esperto

Luciano Augello lives in Le Marche region and is a civil engineer specialising in the planning of work in reinforced concrete, lamellar wood, steel and stonework; evaluation of the structural safety and seismic vulnerability of existing buildings; diagnostics and structural reinforcement. Today he is part of the “Design Studio Associato” team based in San Benedetto del Tronto.