**2. The use of base-isolation and energy dissipation technologies at L'Aquila**

The large number of losses in the property assets caused by the 2009 earthquake, particularly in the case of strategic structures (Hospital, Governance offices, School and University Buildings, infrastructures, Bank Buildings, etc) has demonstrate the large seismic vulnerability of the L'Aquila territory. Probably, the case of the University buildings it is emblematic because these structures were extremely "strategic" from the point of view of the caused disturbance to the local equilibrium reached, before the earthquake, at any level (social, economical, etc). Indeed, the 27000 students attending the classes in the building of the several Faculties constitute a large revitalizing effect for the production realized in the territory of L'Aquila. In contrast the damage suffered by this extremely strategic institution for its territory through the scarce seismic performance of the entire property asset [1] has bad consequence in the reconstruction phase. Notwithstanding the large losses, many projects have been started, immediately after the earthquake, to react immediately to the catastrophic event. Due to a long period of aftershock swarm, still continuing in the area, the main idea, which it was followed, is the realization of safer structures with affordable costs. Therefore, several projects have been realized exploiting the use of passive control for seismic protection, either through the concept of base isolation or by enhancing the dissipation capacity of the structural system. These interventions have been conducted both for buildings devoted to public services and to residential buildings. The realizations using a base isolation system as main seismic protection strategy, available to the author knowledge, are summarized in Table 1 while the structural systems enhanced through dissipative devices are described in Table 2.

In the first one, the use of energy dissipation devices, such as nonlinear fluid viscous dampers, in a peculiar configuration scheme that make use of the concept of dissipative interconnection in adjacent structures, is illustrated. Indeed during the seismic event of 6th April 2009, the edifices of the Engineering Faculty have suffered particularly for seismic induced large structural displacements and accelerations which have brought them out of order due, mainly, to the failure of non-structural elements [3,4], the breakage of wiring and piping systems and the destruction of furniture and machineries. In particular, among the three recently built buildings of the campus, erected in the early 90's, the so-called "Edifice A" presents the most critical damage scenario, which has been objective of a significant rehabilitating intervention. The critical choice during the design stage and testing are illustrated through several analysis conducted with the aim to construct reliable numerical models reproducing the experienced seismic behaviour and the expected enhancement due to the retrofitting. In particular, the main results of a dynamical testing campaign [5] used to calibrate a series of finite element models, able to reproduce the structural behaviour of the Edifice A, at low oscillation amplitude, are here discussed. Nonlinear static and dynamic structural analysis has been used in the evalu‐ ation of the structural performance [4] and of the proposed structural control effectiveness [6]. Device testing [7] and installation procedures have been considered in the overall process to reach high level of confidence in the matching of the rehabilitation goals with the realistically

208 Engineering Seismology, Geotechnical and Structural Earthquake Engineering

In the second one, the use of a wireless sensor network (WSN) for permanent structural health monitoring (SHM) of historic buildings in a seismic area is considered, evidencing the conducted specific activities to customize the system for the continuous assessment of the damaged conditions. On the basis of a defined design strategy [8-10], a permanent structural monitoring systems has been installed on the damaged *Basilica of S. Maria di Collemaggio*, at L'Aquila and it is currently working during the whole day. The main findings in the design, delivery, installation and management of the monitoring systems are presented. A series of tests has been conducted for the monitoring systems and the acquired data have been used for structural identification purpose on the basis of clearly stated procedure [11]. Several regis‐ trations acquired with the systems during local aftershock or more distant, relatively strong, shocks, as for example the recent Emilia earthquake (20-05-2012), are used to demonstrate the possibility given by the dynamic monitoring to produce valuable information for the structural assessment of historical monuments which can be in strongly damaged condition, such as the

**2. The use of base-isolation and energy dissipation technologies at**

The large number of losses in the property assets caused by the 2009 earthquake, particularly in the case of strategic structures (Hospital, Governance offices, School and University Buildings, infrastructures, Bank Buildings, etc) has demonstrate the large seismic vulnerability of the L'Aquila territory. Probably, the case of the University buildings it is emblematic because these structures were extremely "strategic" from the point of view of the caused disturbance

installed seismic protection system.

case of the Basilica.

**L'Aquila**

Immediately after the earthquake one of the main problems, is to found the right compromise between temporary or definitive construction of houses, which can be used to maintain the population at the site. In the case of L'Aquila a peculiar solution to the problem has been provided directly by the National Government, the Project CASE, consisting in 185 buildings constructed in record time to provide a right accommodation to a large amount of the population through the realization of 4.500 apartments in 185 buildings [12]. Every building has the same structure at the ground floor (columns with seismic isolators and a rigid slab), while the superstructures have been made with different construction solutions and materials.

Among public buildings, the new venue of ANAS, the Italian Infrastructure Public Authority for the management of the road network, has been built in a very short time. It has a circular plant and a base isolation system. Furthermore, it was carried out the demolition and recon‐ struction of a portion of the Court Law Building, the construction of the new venue of the Faculty of Letters (with the process started in 2006) and the retrofitting of the Faculty of Engineering, project extensively discussed in the following section 4. As important as the public buildings, there were several retrofitting interventions in residential damaged build‐ ings. Among these, quite interesting it is the case of the condominium in via Rauco, being one of the first examples of a peculiar technology application for the uplift of the buildings. During the realization thanks to hydraulic jacks, it was possible to uplift the building of 60 cm and insert seismic isolators at ground floor level. Another example is the case of condominium Habitat, consisting in 10 buildings of different heights connected to one another by 9 bodies scale, arranged to make a semicircular plant all together. The intervention has been charac‐ terized by the realization of a single rigid slab to the level of the first deck and the cutting of the columns on the ground floor level, to allow insertion of the devices. In this way it was possible to realize a unique isolation system for all the bodies of the condominium.

The data collected regarding structural control systems, recently, realized in L'Aquila are summarized in Tables 1 and 2, in which is specified, for each construction, the type of inter‐ vention, the type and quantity of the devices used and, for some of them, the available specific design characteristics.


**Device Max Horizontal Load (kN)**

211

15

**Device δ max (mm)**

http://dx.doi.org/10.5772/55438

Devices 20 150

4 (Type I) 8 (Type II) 12 (Type III)

2 (Type IV)

24

9

8 (Type II)

4 (Type I)

18 (Type VII) 18 (Type VIII)

14 (Type I)

2 (Type I) 12 (Type II) 15 18 (Type III)

18 (Type I) 17 (Type II) 8 (Type III)

**Number of Devices**

18 (Type II) 20 (Type III) 10 (Type IV) 22 (Type V) 24 (Type VI)

Devices 15 560

**Condominio La** 

**Condominium** 

**Condominium via Milonia, 4**

**Building** 

**Condominium** 

**Edifice A Engineering Faculty**

**Building**

**Building via Rosana - Gioia dei Marsi (AQ)**

**Casetta** 2012 Retrofitting Reinforced

the area of the transept of the Basilica.

**via Milonia, 2** <sup>2012</sup> Retrofitting Reinforced

**corso Federico II** <sup>2012</sup> Retrofitting Reinforced

**Avenia** <sup>2012</sup> Retrofitting Reinforced

**Design and Construction Period**

<sup>2011</sup> Retrofitting Reinforced

**Type of Intervention**

2012 Retrofitting Reinforced

**Table 2.** Examples of interventions using passive energy dissipation systems

**Construction Material**

concrete

concrete

concrete <sup>5</sup> Elasto Plastic

concrete <sup>4</sup> Elasto Plastic

4

**Number Floors of Superstrucutre**

Advanced Applications in the Field of Structural Control and Health Monitoring After the 2009 L'Aquila Earthquake

10 (Type III) <sup>2012</sup> Retrofitting

concrete <sup>3</sup>

concrete

Reinforced

<sup>4</sup> Elasto Plastic Devices

Elasto Plastic Devices

Elasto Plastic Devices

<sup>4</sup> Viscous Dampers

**Seismic Protection System**

Devices

concrete <sup>4</sup> Elasto Plastic

The data are evidencing the impact of the structural control technology either in the immediate intervention after the earthquake and in the longer reconstruction phase. To the author knowledge, at the city of L'Aquila during the earthquake, base isolation systems or passive energy dissipation devices were not protecting any in-service structure. Only the building of the Faculty of Letter of the University of L'Aquila was under construction, with the isolators on-site but with the superstructure incomplete and the edifice not finished [13]. To have a complete picture, it can be cited that two hysteretic metallic force limiters were installed in the year 2000 at the end of a light truss structure connecting transversally the slender walls of the nave of S. Maria di Collemaggio [14]. The performance of these devices under the earthquake is still under investigation by different research groups, due to the partial collapse occurred in

Therefore, immediately after the earthquake the base isolated system at L'Aquila, excluding the peculiar project CASE, reaches the number of 20 interventions with a total number of one thousand (1000) installed devices (as reported in Table 1). The data permits to notice that two main classes of seismic bearing insulator have been installed based on viscoelastic behavior (rubber bearing - RB) or friction (sliding pendulum bearing - SPB). The installed devices are almost the same number in each of the two classes (45% RB – 55% SPB). Several data are missed, because are currently not available, as for instance, the average design period of the base isolation systems. Table 2 shows a synthesis of the realized interventions using passive energy dissipation devices. To the author knowledge, three hundred (300) passive devices have been already installed after the earthquake, mostly based on reaching dissipation through the

**Table 1.** Examples of interventions using a base isolation system in the city of L'Aquila.


**Table 2.** Examples of interventions using passive energy dissipation systems

**Substructure**

**Construction Material**

**Building**

**Design and** 

**Construction** 

**Type of** 

**Intervention**

**Period**

**ANAS** 2009 - 2010

**C. A. S. E. Project**

2009-2010

Buildings for

Steel and reinforced

concrete columns,

reinforced concrete rigid

slab.

Homeless

(185 buildings)

**Auditorium** 2010 - 2012

**Car Dealership Ford** **Residential Building**

**Table 1.** Examples of interventions using a base isolation system in the city of L'Aquila.

**Condominium Habitat** **Residential Building** 

2011

Retrofitting

Reinforced concrete

Reinforced concrete

6

Friction Pendulum Bearings

Friction Pendulum Bearings Elastomeric Bearings - HDRB

Elastomeric Bearings - HDRB

42 (2 different sizes)

30

26

Friction Pendulum Bearings

**via Rauco** **Condominium** 

2011

Retrofitting

Reinforced concrete

Reinforced concrete

> **Domus Prima**

**Condominium Fortuna 2**

**Condominium** 

2012

Retrofitting

Reinforced concrete

Reinforced concrete

> **Borgo dei Tigli**

**Condominium Aguglia** **Condominium Amiterno**

**Condominium Barattelli**

**Condominium Leonardo**

**Condominium Acrie -** 

2012

Retrofitting Retrofitting

Reinforced concrete

Reinforced concrete

Reinforced concrete

Reinforced concrete

> **Building C2**

**Condominium Andromeda**

 2012 **Faculty of Letter** 2006 - 2012

**Court Law Building -** 

2011

Demolition and reconstruction

Reinforced concrete

3 Buildings: 1 in steel, 2 in reinforced buildings.

3

Friction Pendulum Bearings


72 (2 different sizes)

17

52 (4 different sizes)

**Building B** **3 Buildings** 

2011

Demolition and reconstruction

Reinforced concrete

Reinforced concrete

3

Elastomeric Bearings

**via Francia** **Building** 

2012

Demolition and reconstruction

Reinforced concrete

Reinforced concrete

3

Elastomeric Bearings

Elastomeric Bearings

**via Cadorna** **Condominium S. Antonio** 

2012

Demolition and reconstruction

Reinforced concrete

Reinforced concrete

> **- Building A**

Demolition and reconstruction

Reinforced concrete

Reinforced concrete

6 (build. A,B)-7 (build. D)-1 (build. C)

Elastomeric Bearings (HDRB) and sliders

77 + 34

31 Type I, 11 Type II, 15 Type III, 9 Type IV, 6 Type V, 5 Type VI

2.6

1

492

14000

2012

Retrofitting

Reinforced concrete

Reinforced concrete

2012

Retrofitting

Reinforced concrete

Reinforced concrete

2012

Retrofitting

Reinforced concrete

Reinforced concrete

Single building Friction Pendulum Bearings

Friction Pendulum Bearings Friction Pendulum Bearings

44

66 (3 different sizes)

26

Elastomeric Bearings - HDRB

Elastomeric Bearings - HDRB

19 (2 different sizes)

2012

Retrofitting

Reinforced concrete

Reinforced concrete

2012

Retrofitting

Reinforced concrete

Reinforced concrete

2011

2012

New construction

Retrofitting

(19 bodies

Reinforced concrete

Reinforced concrete

3 (edges) and 5 (center)

Friction Pendulum Bearings

2.75

277 (4 different sizes)

32

47 (3 different sizes)

21

300

390

350

300

355

350

connected)

Reinforced concrete

Reinforced concrete

2011

New construction

Reinforced concrete

Reinforced concrete

New construction

Reinforced concrete

Laminated wood

Single building

Elastomeric Bearings

14

18

17

Elastomeric Bearings

Elastomeric Bearings

New construction

Reinforced concrete

Reinforced concrete

3

Elastomeric Bearings - HDRB

60

**Superstructure**

**Superstrucutre Number Floors**

**Seismic Protection Device**

Wood, steel, or

3

Friction Pendulum Bearings

> concrete.

3000

**Bearing** 

**First Mode** 

**Vibration Period** 

**(sec)**

**Base Isolation** 

**Vibration Period** 

**(sec)**

**Bearing** 

**Max Vertical Load** 

**(kN)**

**δ max** 

**(mm)**

3000

3000

260

0.5

4

40x28 buildings=1120 Type I (r. c. columns)

**Number of Bearings** 40x91 buildings=3640 Type I (steel columns)

32x3 buildings=96 Type I (steel columns)

40x61 buildings=2440 Type II (steel columns)

32x1 buildings=32 Type II (steel columns)

3000

210 Engineering Seismology, Geotechnical and Structural Earthquake Engineering

The data are evidencing the impact of the structural control technology either in the immediate intervention after the earthquake and in the longer reconstruction phase. To the author knowledge, at the city of L'Aquila during the earthquake, base isolation systems or passive energy dissipation devices were not protecting any in-service structure. Only the building of the Faculty of Letter of the University of L'Aquila was under construction, with the isolators on-site but with the superstructure incomplete and the edifice not finished [13]. To have a complete picture, it can be cited that two hysteretic metallic force limiters were installed in the year 2000 at the end of a light truss structure connecting transversally the slender walls of the nave of S. Maria di Collemaggio [14]. The performance of these devices under the earthquake is still under investigation by different research groups, due to the partial collapse occurred in the area of the transept of the Basilica.

Therefore, immediately after the earthquake the base isolated system at L'Aquila, excluding the peculiar project CASE, reaches the number of 20 interventions with a total number of one thousand (1000) installed devices (as reported in Table 1). The data permits to notice that two main classes of seismic bearing insulator have been installed based on viscoelastic behavior (rubber bearing - RB) or friction (sliding pendulum bearing - SPB). The installed devices are almost the same number in each of the two classes (45% RB – 55% SPB). Several data are missed, because are currently not available, as for instance, the average design period of the base isolation systems. Table 2 shows a synthesis of the realized interventions using passive energy dissipation devices. To the author knowledge, three hundred (300) passive devices have been already installed after the earthquake, mostly based on reaching dissipation through the exploitation of confined material in the elasto-plastic regime during the earthquake. Only in the case of the Edifice A of the Engineering Faculty Building forty-three (43) nonlinear viscous fluid dampers of three different types have been installed looking for the increase of dissipation through the relative velocity of adjacent sub-structures.
