“ECO-SCHOOL” in Oliveto Citra (SA), an energy-saving school complex

Structural dissipation by noninvasive external interventions is an advanced technique to improve the seismic performance of buildings without significantly altering their functionality. This approach involves the installation of dissipative devices, such as viscous, hysteretic, or pendulum dampers, applied to facades or elements connecting structure and external reinforcement systems. Such devices absorb and dissipate seismic energy, reducing stresses on existing load-bearing elements and limiting damage in the event of an earthquake. Interventions may include the insertion of dissipative bracing or additional steel frames anchored to foundations, improving safety without compromising the use of interior spaces.

The high energy-saving school complex in Oliveto Citra, dubbed “Eco-school,” is a complex characterized by 5 structural blocks, built in different eras.

The school complex, subject to a careful analysis aimed at identifying the overall level of static safety, has 3 blocks already built and 2 blocks to be built and designed.

The design idea, for the existing structures, is to provide improvement interventions mainly through the insertion of external bracing capable of providing additional energy dissipation of the viscoeltastic type.

For the newly built structures, on the other hand, the design idea is to provide reinforced concrete framed structures in both directions, with indirect pile foundations, and with external steel bracing capable of providing additional energy dissipation, in order to improve the transverse seismic response in occurrence of the seismic demand assessed for the Limit State of Collapse – SLC.  

SEISMIC IMPROVEMENT INTERVENTIONS – SEISMIC DISSIPATION SYSTEMS

For the Eco-school, the existing structures, fall into the type of “frame structures” as reported in section 7.4.3.1 of the N.T.C./18. The pillars are rectangular section (of size 40×50) in the first two levels, while in the last level they undergo along the long side a tapering of 10cm (40×40). The beams, with similar section distribution for all decks, have dimensions 30×50, 30×60, 60×24 and 80×24 cm.

The seismic improvement project consists of:

– introduction of a bracing system to support the frames, made with seismic walls founded on micropiles;

– introduction of passive protection by dissipative bracing structures;

– restoration of proper functionality of seismic joints.

The planned interventions do not substantially alter the current distribution of masses, stiffnesses, and resistances, even in view of the nonstructural elements present such as exterior infill and interior partitions. These interventions, by mitigating the main causes of fragility and vulnerability to seismic actions, allow the building to ensure a substantial increase in performance with respect to the seismic actions required by the standard for the site.

Specifically, the dissipation devices are designed with a low plasticization threshold so as not to change the static and seismic response of the building in the occurrence of seismic events of low intensity and, therefore, the structure was designed to respond, in any case, to the design seismic demand without the presence of additional dissipators.

In the specific case of Oliveo Citra, external inverted K bracing with hysteretic dissipators of the UFP (U-shape Flexural Plate) type were inserted in the transverse header frames of the pre-existing building blocks. The objective of the planned dissipation system is to provide additional energy dissipation in order to improve the transverse seismic response in occurrence of the seismic demand evaluated for the Limit State of Collapse – maximum seismic demand.

Description of seismic bracing

The planned dissipation strategy is implemented by dissipative seismic bracing arranged at the short sides of the building.

The braces are made by means of an inverted K macro system in the meshes of the first two spans of the transverse header frames. The supports are made from box profiles with a circular cross-section of 168mm outside diameter and 12.5mm thickness. These supports are restrained at the base by means of steel collars lining and confining the abutments, made of 20mm-thick welded steel plates. A shaped steel plate is placed at the apex of the K-shaped macro braces on which the bases of the UFP devices will be allocated. The connections between the inclined supports and the lower and upper plates are planned to be bolted. Above the dissipation devices, an additional shaped plate is planned to be engulfed in the upper floor truss. The UFP devices are bolted to the lower and upper bases by 2+2 M16 bolts and counter shimming plate. This makes it possible to provide for their replacement in case of damage or degradation.

 

NEW CONSTRUCTIONS

The new buildings are planned with a framed structure made of cast-in-place columns, beams and floors and equipped with a seismic protection system capable of dissipating energy through the use of devices mounted at external steel braces.

The foundation is of the indirect type on in-situ drilled piles, 50cm in diameter, placed below a lattice of foundation beams of 80×80 section connected with tie beams of 30×80 section. The structure in elevation falls into the type of “frame structures” as reported in Section 7.4.3.1 of the N.T.C./18, in which the pillars are developed in height with a constant rectangular section of 40x60cm, while the beams have for all three decks planned rectangular sections 40×50.

 Description of seismic bracing

Also in the case of new construction, the planned dissipation strategy is implemented by dissipative seismic bracing arranged at the short sides of the building.

Specifically, the braces are made by means of an inverted K macro system in the meshes of the first two spans of the transverse header frames. The supports are made of box profiles with a circular cross-section with an outside diameter of 168mm and a thickness of 12.5mm. These supports are restrained at the base by means of steel collars lining and confining the abutments, made of 20mm-thick welded steel plates. A shaped steel plate is placed at the apex of the K-shaped macro braces on which the bases of the UFP devices will be allocated. The connections between the inclined supports and the lower and upper plates are planned to be bolted. Above the dissipation devices, an additional shaped plate is planned to be engulfed in the upper floor truss. The UFP devices are bolted to the lower and upper bases by 2+2 M16 bolts and counter shimming plate. This makes it possible to provide for their replacement in case of damage or degradation.

 

TERRITORIAL AWARENESS OF SEISMIC RISK

The adoption of seismic dissipation devices is an effective strategy to reduce damage to structures during an earthquake and improve the safety of communities.

Interventions with the adoption of solutions that include dissipation devices, such as those implemented on the Ecoscuola in Oliveto Citra, are essential to raise awareness of the importance and role these tools play in earthquake risk mitigation.

In addition, promoting awareness of these systems through information campaigns, educational events, and practical demonstrations can increase the perception of seismic risk and incentivize adaptation interventions in existing buildings. Spreading awareness among citizens, administrations and professionals in the field contributes to a culture of prevention, fostering more responsible choices in the design and maintenance of buildings for greater territorial resilience.

 

BIBLIOGRAPHY

[1] B. Palazzo, L. Petti “Aspects of structural vibration passive control”. International Journal of MECCANICA 1997;

[2] Petti L., De Iuliis M., “A new approach to design extra-structural dissipation systems in framed structure by considering seismic demand spectra” Proceedings of Fourth World Conference on Structural Control and Monitoring 2006”;

[3] Petti L., De Iuliis M. Optimal Design of Supplemental Dampers in Framed Structures European Earthquake Engineering, Vol. n° 1, 2004.

[4] D. M. Infrastrutture Trasporti 17/01/2018 (G.U. 20/02/2018 n. 42 – Suppl. Ord. n. 8)“Aggiornamento delle Norme tecniche per le Costruzioni”.

[5] Circolare 21 gennaio 2019, n. 7 C.S.LL.PP. (G.U. Serie Generale n. 35 del 11/02/2019 – Suppl. Ord. n. 5) Istruzioni per l’applicazione dell’«Aggiornamento delle “Norme tecniche per le costruzioni”» di cui al decreto ministeriale 17 gennaio 2018.

 

Watch the video: Seismic risk – problems and opportunities – Prof. Ing. Luigi Petti