"Porta Napoli”, L’Aquila

Restoration and seismic improvement of residential complex

 
This complex of 5 buildings represents one of the first examples of “social housing” in Italy, and for this reason it is protected as Historical Architectural Heritage. This compound was built by INCIS (National Institute for Government Employees Houses) around 1925-1930 to host government employees and their families.
These historical buildings have been heavily damaged by the earthquake that hit the region of Abruzzo (central Italy) on April 2009, rated 5.8 on the Richter scale, making them uninhabitable unless extensive and substantial restoration.
Main seismic vulnerability of the buildings was the poor quality of stone masonries, due to roughly-shaped stones, frequently undersized, and low consistency mortar, occasionally applied with undue thickness to compensate stones irregularity.
The aim of the restoration intervention was either a static consolidation and the seismic improvement of the buildings, achieved by reducing the causes of seismic vulnerability.
The intervention was designed on one side to increase walls mechanical strength, in order to make them able to suitable to absorb combined shear, compression and bending stresses typically induced by seismic action, on other side to optimize the structural response of the whole building.
Design strategy was first to repair all items damaged by the earthquake in order to restore original situation, and then to proceed with a global consolidation of the structures, to achieve the seismic improvements level required, and to increase ultimate strength and ductility of the buildings.
Masonry walls consolidation have been achieved through the “reinforced plaster” method, i.e. the application of Fibre Net glass fiber mesh on both faces, connected transversely by mean of FRP connectors, and fixed by mean of a thin (3-4cm) plaster layer.
Thanks to FRP absence of corrosion, mortar was lime-based type, ensuring the best compatibility with the existing masonry, good breathability and resistance.
The use of composite materials instead of steel assure long term durability and a reduced  alteration of walls overall stiffness (inflexibility).
The intervention was extended to all internal and external walls, either stone and bricks ones, at all levels of the building. Consolidation job was completed at the end of 2012 achieving, and often going beyond, expected improvements.
At the moment construction site is in the final stage to perform last finishing.

 

FRP MATERIALS

The acronym FRP (Fibre-reinforced polymers) define the composite materials made of a polymer matrix (thermosetting polyester, epoxy, or vinyl-ester) reinforced by mean of fibers (glass, carbon or aramid). FRP products can be 2 to 10 times stronger than steel, while weight can be less than 1/5, in addition, there are several others well-defined benefits common on all FRP products.
FRP materials have been developed over one century ago, while commercial uses started during early 1930s. Nowadays, thanks to the above mentioned benefits, they are extensively used in the aerospace, automotive, marine, construction industries, as well as sports and hobby equipments.

> HISTORICAL BUILDING CONSOLIDATION
The constant effort to improve and search for new technical solutions, the long term cooperation with research centers, laboratories and universities, the training of technicians and business enabled Fibre Net to develop FIBREBUILD, a range of FRP products and systems for structural reinforcement of existing masonry buildings, whether they are valuable or less.
Any masonry, be it of stone, brick or mixed material, vault, as well as light weight floor screeds or low thickness, can be mechanically improved through FIBREBUILD system, consisting of FRP rods, mesh and accessories.
FRP meshes are integrated with the “reinforced plaster” method, which is widely recognized as the most effective technique, as it guarantees high degrees of improvement on historical and existing walls.
Mesh is fixed by mean of FRP connections evenly distributed over the whole surface of the structure, to achieve better mechanical strength, and avoid thermal bridges. Consolidation is guaranteed over the time by the total absence of corrosion weathering and network compatibility and accessories in FRP with mortars based on lime, gypsum, pozzolana, etc.
FIBRE BUILD systems help building efficient, diffuse and uniform reinforcements, which make the masonry ductile, while keeping the mortar low in thickness and reducing the overall charges, as compared to the conventional reinforcing materials. The results are extremely meaningful seismic improvement.

> REINFORCEMENT OF VAULTS
The consolidation of the intrados and extrados of a vault consists in laying over the whole surface a FRP mesh with the weave size as required for the conditions of the substrate and of the structure. The mesh will adjust to any irregular substrates and the material is very low in weight, which helps easy and fast laying operations. The reinforcement will remain efficient over time also when mortars containing lime, clay, pozzolana, etc. are used. The reinforcement will be secured to the substrate with FRP connecting brackets. 

> REINFORCEMENT OF FLOORS
The consolidation of wooden or of concrete and masonry floors with FIBREBUILD systems consists in making a new concrete slab reinforced with a FRP mesh. The new reinforced slab is then connected to the existing slab through special connections to obtain a new structure featuring greater mechanical performance. Because the FRP sheets are only a few millimeters thick, the reinforcement will fit better in the slab. This means that the load will be better distributed, while the overall thickness remains low. The slab is then joined to the perimeter walls through special FRP brackets.

[by Cecilia Zampa, Pierpaolo Turri]

  

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