Assessment and Seismic Improvement with Traditional and Innovative Technologies in the Reuse Design...

2014, VOL. 1, N. 1

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Water and Earth. The Basin Sahrij Labgar in Marrakech

THE ARCHITECTURE OF REASON: TRADITION, HISTORY AND CITY Architecture And City. A Building by Ferdinando Chiaromonte in aples a Re ection on Its Structure of the Urban and Architectural Composition

TOWARD A SEISMIC ARCHITECTURE Assessment and Seismic Improvement with Traditional and Innovative

Technologies in the Reuse Design of San Benedetto Novello in Perugia

CRITICAL FUNDAMENTALS OF ARCHITECTURAL RESTORATIONThe Oil Industrial Heritage in Venezuela. A Heritage in Activity

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Urban Regeneration In San Francisco (Ca, Usa). Environmental Design For Public Realm

INDEX

ESEMPI DI ARCHITETTURA, 2014, VOL.1, N.1

CITIES AND TERRITORIES TO LIVE ELISA PALAZZO, BRUNO PELUCCA URBAN REGENERATION FEASIBILITY USING AHP TECHNIQUE. CASE STUDY OF RECREATING THE LANDS AROUND THE TOMB OF HAFEZ IN SHIRAZ Hassanali Laghai, Faranak Jamshidi 3 WATER AND EARTH. THE BASIN SAHRIJ LABGAR IN MARRAKECH Federica Visconti, Renato Capozzi 15

THE ARCHITECTURE OF REASON: TRADITION, HISTORY AND CITY FEDERICA VISCONTI, RENATO CAPOZZI ARCHITECTURE AND CITY. A BUILDING BY FERDINANDO CHIAROMONTE IN NAPLES: A REFLECTION ON ITS STRUCTURE OF THE URBAN AND ARCHITECTURAL COMPOSITION Guido Corsaro 23

TOWARD A SEISMIC ARCHITECTURE ALBERTO PARDUCCI

ASSESSMENT AND SEISMIC IMPROVEMENT WITH TRADITIONAL AND INNOVATIVE TECHNOLOGIES IN THE REUSE DESIGN OF SAN BENEDETTO NOVELLO IN PERUGIA Fabrizio Comodini, Marco Mezzi, Olimpia Niglio 33

CRITICAL FUNDAMENTALS OF ARCHITECTURAL RESTORATION OLIMPIA NIGLIO THE OIL INDUSTRIAL HERITAGE IN VENEZUELA. A HERITAGE IN ACTIVITY Lucía Sánchez Figueroa 45

PISA BETWEEN RECONSTRUCTION, PRESERVATION AND TRANSFORMATION Fabiana Susini 53

MATERIALS, TECHNOLOGY, INNOVATION AND ENVIRONMENT GIUSEPPE DI GIOVANNI INNOVATION PROCESSES IN BUILDING RETROFITTING Sergio Russo Ermolli 63 URBAN REGENERATION IN SAN FRANCISCO (CA, USA). ENVIRONMENTAL DESIGN FOR PUBLIC REALM Renata Valente 71

TOWARD SEISMIC ARCHITECTURE

ASSESSMENT AND SEISMIC IMPROVEMENT WITH TRADITIONAL AND INNOVATIVE TECHNOLOGIES IN THE

REUSE DESIGN OF SAN BENEDETTO NOVELLO IN PERUGIA

FABRIZIO COMODINI 1

MARCO MEZZI 2

OLIMPIA NIGLIO 3

1 University eCampus, Faculty of Engineering, Novedrate, Como, Italy

2 University of Perugia, Dept. of Civil and Environmental Engineering, Perugia, Italy

3 Graduate School of Human and Environmental Studies, Kyoto University, Japan

Accepted May 30th, 2014

ABSTRACT The paper deals with the design procedures for the refurbishment, seismic improvement and reuse of a class of historical buildings defined ordinary since they have an intermediate relevance within the cultural heritage of a country. The procedures include the basic knowledge, the assessment methods, the design works aimed at defining appropriate cost-effective technologies and methods for the structural and seismic retrofitting. The research is carried out with reference to an emblematic study-case concerning the reuse of the complex of San Benedetto Novello in Perugia as a center for artistic and cultural activities. The complex includes architectural elements attributed to Gaelazzo Alessi and is nowadays partially occupied by offices. The study provides for the evaluation of the structure safety considering both the global and local level with reference to the performance levels expected at the different limit states. The works for seismic improvement have been designed respecting the peculiarities of the ecclesiastical complex and allowing the performances required by the new functions. Special focus is given to the use of innovative restoring and strengthening technologies allowing for works characterized by cost effectiveness and contained invasiveness. Keywords: Seismic assessment, Seismic improvement, Seismic vulnerability, Conservation, Monumentality.

INTRODUCTION The definition of historical construction refers a large amount of constructions even characterized by very different features. It includes constructions many centuries old and constructions having only few decades of life, constructions built with very different materials, archaeological constructions in ruined state and still operating buildings, constructions having a high architectural or artistic worth and other ones more simple. Many other subjects introducing an element of differentiation within the historical constructions can be found. It is evident that we can refer to historical constructions only in a general way, but if we have to examine special problems we have to focus our attention to a single class of these constructions, or even to a more restrict field. Countries like Italy own a large number of historical construction having a small or intermediate architectural and artistic value generally due to alterations and contaminations operated in their history and frequently in the most recent years or to the decay related to the neglect. Often these constructions risk to be left to their destiny if a motivation for their reuse and a cost effective solution for their safeguard are not found. Opportunities for an appropriate equilibrium among the cost, the effectiveness, the reduced invasiveness of the works allowing for a reuse of the retrofitted construction can be found in the application of the new restoring and strengthening techniques based on the use of innovative technologies. The study of the use of new techniques is particularly interesting for the mechanical performances of the retrofitted structures resulting in composite structural system made of old and new elements. The present research deals with the design procedures for the refurbishment, seismic improvement and reuse of an historical building having a quite noble origin but a quite ordinary status at present. The procedures include the basic knowledge, the assessment methods, the works design aimed at defining practical and appropriate


34 FABRIZIO COMODINI, MARCO MEZZI, OLIMPIA NIGLIO

technologies and methods for the structural and seismic retrofitting. The research is carried out with reference to an emblematic case study concerning the reuse of the church of San Benedetto Novello in Perugia. The objective is to reuse the building as a center for artistic and cultural activities. The structural assessment of the complex of San Benedetto Novello - carried out through a detailed historical-critical study, a geometric and material survey, a direct observation of the structural system supported by diagnostic tests, and a structural analysis - is the basis for a reliable evaluation of the seismic capacity of the structure and then for the subsequent selection of effective improvement works. Special focus is given to the methodology followed in the design and to the application of innovative solutions through which to obtain a reusable, but preserved, construction at a cost compatible with the need to treat a number of such type of constructions. HISTORICAL RECORDS The history of the complex of San Benedetto Novello in the Sant'Angelo quarter in Perugia seems to date back to the early fifteenth century. The historical events of the church of San Benedetto Novello as well as information on particular structural and static solutions adopted for its construction can be found in (Pardi, 1957). According to local information, the church, originally named Santa Maria Novella, was built in 1421 by Giovanbattista da Gubbio and by other of his lay companions who lived near Mount Malbe (Pardi, 2000). This dating is also confirmed by the manuscript of Belforti and Mariotti mentioned by (Guardabassi, 1872; Pardi, 2000). The complex of San Benedetto is an example of the late Gothic period in the first half of the fifteenth century (Pardi, 2000) when the neo Renaissance culture had already begun to produce new ways of doing architecture in neighbouring Tuscany. At those days the Umbrian cultural environment well reacted to the impulse from Florence but, at the same time, it remained firmly rooted in the stylistic forms that had characterized the architecture of the Umbria region for over 250 years. Thus, the church of Santa Maria Novella is a typical example of a late Gothic architecture built together with proto-Renaissance complexes (Pardi, 1975). In 1555, the convent was still fully functional and inhabited, while it is highly uncertain the date on which the convent passed to the Silvestrine nuns, previously living outside Porta Sole at a place currently called Saint Erminio and earlier Saint Benedict (Crispolti, 1648). The bell tower of the church, designed by Galeazzo Alessi, was built in the second half of the sixteenth century. According to geometric and diagnostic surveys performed in recent years, it resulted that the late Renaissance bell tower was built on pre-existing medieval structures, practice very common in that period. Indeed, the old structural element was not abandoned but rather re-evaluated for new buildings. This is a cultural reference also found in other Alessian works even outside the Umbria region. In July 1820, the monastery and church of San Benedetto Novello were suppressed by the Bishop Carlo Filesio Citadinni, who transferred the assets to the seminary and moved the nuns to the convent of Saint Caterina. After a long period of neglect, the entire complex was donated to the Conservatory of Zitelle Pericolanti by the Countess Anna Graziani Baglioni, as also noted by the historian (Siepi, 1826). Despite this intended use, in the late nineteenth century the entire complex fell in a state of alarming deterioration. After World War II, the complex was managed by the Sodality of Saint Martino, which hosted an orphanage run by the Salesian Sisters of Saint Maria Mazzarello, a use that lasted till the end of the 90s of the last century.

Fig. 1-Layout of the church in the present and original configuration

There is a limited knowledge on the events that took place until the end of 1995, when the University of Perugia becomes the owner of the complex and turns it into the home of the Organization for the Right to Education, while the church continues to fall into great decay. However, some works were done as the restoration of the bell tower in 1981, the consolidation of the right arch of the transept between 1981 and 1984, and the late fourteenth-century frescoes restoration in the left aisle of the church. Pardi (1957) notes that the entire complex was initially built with bricks and lime mortar. The floor of the church was traced back to the fifteenth century and attributed to the pottery school of Deruta given its predominant


35 ASSESSMENT AND SEISMIC IMPROVEMENT WITH TRADITIONAL AND INNOVATIVE TECHNOLOGIES

green, red and blue colors on a white background. Of special interest are the cross vaults of the side chapels, in contrast to those of the central nave. At the exterior large buttresses are placed in the same direction of the vaults ribs to counteract the thrust action. The description evidences the formal and in-plan peculiarities of San Benedetto Novello. From a careful and recent survey of the geometric profile various and successive redesigns of its architect since the original setting of the entire structure can guessed. Indeed many formal and structural irregularities (Fig. 1) that lend credibility to the hypothesis of continuous redesigns are present (De Angelis D’Ossat, 1954). THE KNOWLEDGE PROJECT Since the structure is a protected cultural heritage, the historical and analytical phases have been fundamental to reveal the original features, as well as the changes and damage occurred over time, also due to an inadequate use. The execution of an accurate non-invasive diagnostic campaign was also of great importance. The knowledge path included the following main actions (MIBAC, 2010): historical-critical analysis of the building to identify the evolution and transformations; identification of valued elements (especially some decorative and formal elements); geometric survey of the building in the present status and comparison with prior findings; survey and analysis of deformation and cracks; analysis of materials and preservation status; identification of the structural elements and of their corresponding construction details; analysis of structural damage. All the acquired and analyzed information entered into a process of structural analysis leading to a detailed project of seismic improvement of the complex. Aimed at the structural characterization of the construction, a direct survey was carried out to acquire the crucial data for the geometrical definition of the structural elements of the church and the upper floors (Fig. 2a). At the same time a photographic survey of the structural typologies and cracking phenomena (Mastrodicasa, 2003) was performed (Fig. 2b). Video endoscopic surveys, wall essays, ground penetrating radar surveys, and essays on plasters and floors were used to detect the structural sections. The type and number of tests were chosen with the target of obtaining a correct knowledge of the structures, therefore their localization was diffused but limited, accounting for their invasiveness and cost.

Fig. 2-Cracking phenomena: (a) longitudinal section, (b) lateral façade

After preliminary plaster essays performed to verify the eventual presence of frescos having artistic relevance, video-endoscopic surveys were carried out on the vaults of the church and of the crypt. The surveys allowed to detect of the stratification along the time, to identify the structural typology of the horizontal elements and to clarify the consolidation works made in the past. The results of the survey showed (Fig. 3) that the vaults are built with solid brick and are one brick head thick. Some of them have been strengthened through the realization of collaborating r/c slabs. The floors, sometime consisting of slabs 500 mm thick, do not stand directly on them. Flat jack tests, useful to investigate the masonry mechanical parameters and the stress status induced by the vertical loads, were not allowed. Therefore, basing it on the material characterization resulting from the survey, the masonry mechanical parameters reported in Table 1 were defined in accordance with (NTC 2008). The design values were then derived dividing by a confidence factor FC=1.18 resulting from the partial confidence factors associated with the different aspects of the building knowledge (MIBAC, 2010).



Fig. 3-Endoscopic tests: (a) location along a vault; (b) detailed result of a test

Table 1- Mechanical parameters of the masonry

Type masonry fmd (N/cm2)

0d

(N/cm2) Em

(N/mm2) Gm

(N/mm2) W

(kN/m3)

Blocks in solid brick and cement grout

248 6.95 1398 296 18

In the case of protected cultural heritage, the knowledge should not be limited to the current status but it should also identify, where possible, the changes occurred in the history of building. For a correct understanding of the geomorphological situation, a geological and geotechnical study was performed using surveys combined with penetration tests. SEISMIC HAZARD The site of the church, included within the urban perimeter of the city of Perugia, is located in a slightly hilly area at an altitude of about 460 meters. The subsoil is a soft soil that can be classified as a Category C subsoil with reference to (NTC2008) for which a soil amplification factor SS =1.43 results. Due to the slope of the area also a topographic amplification ST = 1.2 shall be considered. Therefore, considering the seismic hazard at the site, the PGA defining the Life Safety ultimate limit state is 0.311 g, being ag,SLV = 0.181 g the acceleration at the bedrock. GLOBAL VULNERABILITY Aimed at the seismic assessment of an existing masonry construction both global and local behavior shall be considered. In the present case a detailed global analysis of the church, modeled with equivalent frame elements or plane finite elements, was deemed less significant due to the related complexity and uncertainty, therefore a simplified procedure has been performed (MIBAC, 2010). The simplified global seismic assessment consists of the calculation of the return period of the peak ground acceleration corresponding to the attainment of the Life Safety limit state, assuming that it occurs for shear failure of the walls in their plane. The calculation is performed adopting a simplified mechanical model in which the overall shear strength of the building is evaluated story by story for each of the two relevant directions in the plane. Figure 4. shows the isometric views of the models at the various stories.

Fig. 4-Simplified models for global assessment: (a) first level, (b) second level, (c) third level

Based on the value aSLV of the response spectrum corresponding to the achievement of the ultimate limit state, the corresponding return period TSLV of seismic action is determined according to the hazard curve of the site. The seismic capacity is expressed through the safety index



SLVR

SLVTS T

TI,

,

(1) where TR,SLV is the return period of the reference earthquake for the ultimate limit state with respect to the nominal life expected for the building. If IS,T is greater than 1.0, the building is suitable to withstand the expected seismic action, otherwise the safety is inadequate. The seismic capacity can be also expressed in terms of peak ground acceleration through the safety index :

)()(

,,

SLVRg

SLVgaS Ta

TaI

g

(2) where ag(TSLV) and ag(TR,SLV) are the acceleration at the bedrock corresponding to the return period TSLV and TR,SLV, respectively. Finally, the seismic capacity of a protected asset can be also expressed through the residual nominal life

(3)

where TSL is the return period of the seismic action that leads to the achievement of the referred limit state, PVR is the probability of exceeding the limit state considered, and CU is a coefficient accounting for the actual use of the construction that in the present case can be assumed equal to 1.5. For a heritage building it is not strictly required to achieve the standard nominal life provided by the codes for the ordinary buildings. The values of the capacity index resulting from the numerical calculations carried out for the preexisting state are reported in Table 2. It results that the "Life Safety" limit state is not satisfied for both X and Y directions, particularly at the second and third level. The minimum value of the safety index results 0.421 and concerns the X direction at the third level. The ultimate limit state is attained for an earthquake having a peak acceleration at the bedrock ag/g = 0.131 and a return period TSLV equal 300 years. Assuming a probability of occurrence PVR = 10%, the residual life is 21 years.

Table 2 - Global capacity indexes

IS,ag IS,T VN pre

existing improved incr %

pre existing

improved pre

existing improved incr %

Level 1 dir. X 0.957 0.972 1.60 0.940 0.984 47 49 4.63

dir. Y 0.969 0.986 1.74 0.974 1.023 49 51 5.03

Level 2 dir. X 0.803 0.854 6.44 0.569 0.680 28 34 19.49

dir. Y 0.864 0.888 2.76 0.703 0.759 35 38 8.07

Level 3 dir. X 0.722 0.928 28.52 0.421 0.861 21 43 104.6

dir. Y 0.765 0.959 25.36 0.496 0.946 25 47 90.5

VULNERABILITY FROM COLLAPSE MECHANISMS OF MACRO-ELEMENTS Observing the damage caused by earthquakes to historical masonry buildings it can be found that they depend on local collapse mechanisms of macro-elements identified within the construction (Giuffrè, 1993; Doglioni, 1994). In the present case the mechanisms were defined taking into account the recognizable structural elements, the observed cracks, as well as the provisions of the Italian guidelines (MIBAC, 2010). In particular the following mechanisms were analyzed: overturning of the façade, overturning of the side walls, in-plane collapses of the triumphal arch, out-of-plane collapse of the apse, overturning of the bell tower, collapse of frescoed walls. Table 3 reports, under the headings existing, the computed safety indexes IS,ag, IS,T and the residual life VN in the existing status for each of the considered mechanisms. Specific works to improve the seismic capacity for each of the mechanisms were designed, as presented in a successive chapter, and their effectiveness were evaluated obtaining new values of IS,ag, IS,T, VN reported in the same Table 3 under the headings improved.

RVU

SLN P

CTV 1ln



Table 3 - Capacity indexes of the macro-elements mechanisms

IS,ag IS,T VN

existing improved % incr existing improved existing improved % incr Façade: out-of-plane rotation 1.011 2.276 >100 1.096 10.989 55 549 >100

Side wall: out-of-plane rotation 0.210 1.221 >100 0.013 1.874 1 94 >100

Side wall: ejection of the top corner 0.807 1.348 67.12 0.577 2.482 29 124 >100

Triumphal arch: two pillars mechanism 0.674 2.530 >100 0.347 >>1 17 742 >100

Triumphal arch: one pillar mechanism 0.779 3.967 >100 0.523 >>1 26 2659 >100

Apse: overturning of the angled section 0.525 2.160 >100 0.170 >>1 9 473 >100

Bell tower: global overturning 0.674 1.033 52.3 0.347 1.166 26 87 >100

Bell tower: overturning of the top portion 0.619 1.530 >100 0.272 >>1 14 178 >100

Frescoed wall: out-of-plane rotation 0.453 1.055 >100 0.112 1.238 8 93 >100

The first considered mechanism consists of the overturning of the main façade. In general the mechanism is controlled by the boundary conditions, by the presence of windows, rosettes, cornices, pilasters, by the thrusts of roof and vaults, and by the dynamic interaction with orthogonal macro-elements. The front wall of San Benedetto Novello is characterized by the presence of a porch that rests on half of the horizontal length of the facade throughout the first level (Fig. 5a and Fig. 5b). The main façade is also characterized by a pediment and by buttresses added over the years to counteract the thrusts of the internal vaults. The facade does not present rosettes or openings in axis with the main entrance or elements preventing the out-of-plane tilting. The thickness of the walls varies from 800 mm at the base to 400 mm at the top. The restraining effectiveness of the side walls is difficult to estimate. The relevant examined mechanism concerns the out-of-plane rotation of the facade around an axis located at the first level elevation (Fig. 5c). The safety indexes in the original status are slightly greater than one (Table 3) but the result is strongly influenced by the degree of efficiency of the continuity between the facade and the side wall.

Fig. 5-Façade: (a) localization in plant (b), front view, (c) collapse mechanism analyzed

The "side wall" macro-element can be identified considering the geometry of the openings and the connections with the other structural elements. In particular, the side walls have a significant interaction with the roof, because the main beams are supported by the side walls, and their reactions represent a significant factor in the mechanism activation. The analysis concerns the portion of the wall on the presbytery shown in Fig. 6a.



Fig. 6-Side wall: (a) localization in plant, (b) front view, (c) and (d) : collapse mechanisms analyzed

The wall withstands the thrust of the wooden roof, at the top, and the thrusts of the cross vaults at the basement and at the first level. The wall is characterized by openings modified during the years and irregularly distributed; near the load transfer areas of the vaults, buttresses designed to contain the horizontal thrusts are encountered, increasing the resisting section at the base (Fig. 6a and Fig. 6b). The wall thickness varies from 1,100 mm at the basement and first level to 450 mm at the last level. Accounting for the actual boundary conditions the most probable collapse mechanisms are the out-of-plane rotation of the wall (Fig. 6c) and the ejection of the top corner (Fig. 6d) that result characterized by very low values of the safety indexes (Table 3). The third relevant mechanism concern the pointed triumphal arch that separates the hall from the presbytery. The arch already presents some cracks. The assessment has been performed with reference to two possible collapse mechanisms shown in Fig. 7. The values of the safety indexes reported in Table 3 evidence the lack in seismic capacity of the element and the need for a significant upgrading.

Fig. 7-Triumphal arch: (a) localization in plant; (b) and (c) : collapse mechanisms analysed

Fig. 8-Apse: (a) localization in plant, (b) front view, (c) collapse mechanism analysed

The apse is a polygonal in-plan three-dimensional macro-element having a roof, made of wooden struts, that applies thrusts toward the outside of the apse along its top perimeter.



Openings with irregular distribution and vaults applying thrusts at the mid height of the walls represent further factors influencing the vulnerability of the macro element (Fig. 8). The walls thickness is constant along the total height and equal to 900 mm. The considered collapse mechanism involves the separation of the corner portion with out-of-plane rotation and the formation of oblique cracks on the side walls of the apse (Fig. 8c). The mechanism is characterized by a low activating acceleration (Table 3) evidencing the lack in seismic capacity and the need of a protecting device. The bell tower is adjacent to the back façade and to the apse of the main structure. The continuity between them is not actually effective because of existing vertical cracks along the contact surface with width increasing from the bottom to the top. The bell tower is 30 m height and has a square base with 3,500 mm wide sides. The wall thickness is 1000 mm, almost constant along the height. The bell tower includes two bell cells: the first one is located at the level of the main building roof and the second one at the tower top. The collapse mechanisms concerning the overturning of the entire bell tower as well as the collapse of the portion overlying the roof of the main body are analyzed (Fig. 9).

Fig. 9-Bell tower: (a) localization in plant, (b) and (c) : collapse mechanisms analysed

The collapse mechanisms of the bell cells are not investigated because they are prevented by the presence of ties installed at the level of the impost of the bell cell arches. The seismic safety level in the original status is insufficient as shown by the values in Table 3. A frescoed nonstructural wall represents a particular element within the church. On the right side of the transept a partition wall was erected in the sixteenth century because of functional needs requiring the separation of the area of the chapels and nave from the area of the transept and apse and the wall was then frescoed (Fig. 10).

Fig. 10-Frescoed wall: (a) front view, (b) localization in plant, (c) collapse mechanism analysed

At the contact between the wall and the vault on the non-frescoed side cracks can be observed that prove the detachment of the wall due to the absence of mutual insertions among the frescoed wall, the vaults and the perimeter walls. The safety limit of an out-of-plane overturning collapse of the wall should be evaluated (Liberatore, 2000). Fig. 10 shows the wall location, a picture of the fresco, and the potential collapse mechanism. In this case, the "artistic damage" limit state is evaluated and the computed safety indexes in the existing status reported in Table 3 shows the inadequacy of the present configuration. DESIGN FOR THE SEISMIC IMPROVEMENT The designed structural works are aimed at the preservation of the structure but also at the improvement of the seismic capacity (Cifani et al, 2004; Rocchi, 2003). An approach that can definitely achieve the full seismic protection of a historic building as well as of its artistic content consists of the adoption of a base isolation system (Mezzi et al, 2011).



In the present case the isolation option is not practicable due to the presence of a crypt at the basement level therefore alternatives works, both traditional and innovative, are designed. To improve the global capacity of the construction some solid brick masonry walls are added at the second and third level, while some of the existing masonry walls are reinforced with cement plaster reinforced with glass fiber net (Fig. 11).

Fig. 11-Global seismic improvement: (a) second level, (b) third level

The strengthening works on the walls have been calibrated to increase the overall capacity in the X direction at both the levels, and in the Y direction at the last level only. Moreover, at the last levels the addition of steel ties in both longitudinal and transversal direction is provided to produce a box-like behavior of the whole building (Fig. 5) and the addition of steel curbs is provided to improve the diaphragm behavior of the floors. The steel ties are equipped with in-series SMAD devices (Fig. 12b) to also supply a dissipative capability to their conventional tying effect, improving their effectiveness in case of earthquake. The works are compatible with the state of the higher levels resulting from recent rehashing and characterized by minor conservation needs. The values of the global capacity index for the improved state are reported in Table 2. In this retrofitted state the ultimate limit state is attained for an earthquake having ag/g = 0.168 and a return period TSLV = 613 years, the residual nominal life VN is equal to 34 years. In addition to the works aimed at improving the global capacity of the church, specific works were designed for each of the mechanisms locally interesting the macro-elements of the complex to improve their seismic capacity. The seismic capacity associated to the mechanisms was re-evaluated and the values of IS,ag, IS,T, VN in the improved status are reported in Table 3 under the headings improved. Concerning the mechanism of the main façade, in spite of the values of the safety index slightly greater than one resulting in the existing status, a new evaluation in the retrofitted status was performed accounting for the seismic improvement derived by the already mentioned addition of steel ties provided in both longitudinal and transversal direction. The new evaluation leads to a doubled value of IS,ag. With reference to the side walls, the designed works providing for introducing steel ties at the floor levels and steel curbs at the last level allow to avoid the out-of-plane overturning (Fig. 11 and Fig. 12) with significant increase of the safety index IS,ag up to 1.35 (Table 3). To counteract the lateral thrust of the triumphal arch, the project provides for the inclusion of an innovative lightweight extradosed tying system. It consists of slightly pretensioned inclined bars fixed with polymeric binders within the lateral masonry walls and connected to a top FRP beam located above the arch key. The system, avoiding an eccentricity of the ties with respect to the level of the horizontal thrust of the arch does not generate shear actions on the portions of the lateral masonry walls located between the impost and the key levels of the arch. The values of the safety indexes in the improved status, reported in Table 3 show the effectiveness of the proposed improvement. To counteract the collapse mechanism of the apse, the design provides for the insertion of a top steel curb along the perimeter walls of the apse connected to the walls of the main body. The restraining action applied by the steel curb produces the expected improvement as shown by the increased value of the safety indexes resulting from the analyses of the improved configuration (Table 3). For the bell tower, the designed works provide for restoring the continuity between it and the main body through links consisting of composite bars anchored in the masonry.



Fig. 12-Particulars of the seismic improvement design

Moreover an innovative technique is provided consisting of four slightly pre-tensioned dissipating cables located at the four bell tower corners running the entire height and including SMAD devices. The dissipating cables allow to reduce the lateral displacement and to increase stability, thanks to the added stiffness. Moreover, thanks to the effect of the in series dissipating devices, they give a supplementary energy dissipation during the seismic attacks that further contribute to reduce the shifts and to increase the seismic resistance of the tower. A special steel frame and a new foundation are provided at the top and bottom of the tower, respectively, to anchor the tie rods (Fig. 13). The designed works allow to improve the seismic capacity as it results from the values of the safety indexes in the retrofitted status reported in Table 3.

Fig. 13-Seismic improvement of the bell tower

Fig.14-Seismic improvement of the frescoed wall

For restraining the development of the collapse mechanisms of the frescoed wall the design provides for an original synergetic use of a light wooden frame bonded with polymeric resins that stiffen and prevent the overturning. The solution consists of the installation of a wooden framework (Fig.14) connected to the non-frescoed side of the wall and to the vault structures.



The connection between the wall and the wooden frame is made with polymeric bonding while the connection with the perimeter structures is made with removable mechanical elements. The wooden buttresses will be hidden through a plasterboard wall. The solution will prevent the overturning of the septum practically without increasing the mass. The materials used meet all the requirements of conservation and compatibility with the original materials. The proposed solution is effective and produces a significant seismic improvement of the safety index IS,ag up to value greater than one (Table 3) guaranteeing the safeguard of the frescos. CONCLUSIONS The performed study concerns the seismic assessment and the design of the seismic upgrading for the reuse of the complex of San Benedetto Novello in Perugia. This emblematic case study is representative of that number of ordinary historical constructions having an intermediate architectural and artistic worth that can overcome the risk to be definitely abandoned only if cost effective and not impacting solutions for their retrofitting can be defined within an hypothesis of their reuse. The assessment in the existing and in the improved status is carried out at both global and local level. The analysis at local level requires to identify and evaluate multiple collapse mechanisms. The mechanisms are related to the geometry, to the structural configuration and to the cracking map featured in the structure. This approach requires special professional know-how and computational capabilities oriented to the particular mechanism. Different kinds of indexes can be introduced to define the vulnerability of the various mechanisms expressing different aspects of the vulnerability. In particular, the index expressed in terms of the residual nominal life allows to establish a priority among the works to be adopted within the financial plan of the project. In the examined case study an effort was made to pursue the double objective of seismic improvement and architectural preservation. This was made possible providing structural works that combine traditional and innovative techniques and materials. Some original solutions provided in the design have been evidenced: the use of the pre-tensioned dissipative cables equipped with SMA devices to stiffen, strengthen and enhance the seismic response of the bell tower; the synergetic use of a wooden frame bonded with polymeric resins to the frescoed walls with a stiffening and connecting effects; the extradosed FRP beam - bars tying system to counteract the lateral thrust of the triumphal arch. Particular attention was focused on the chemical and physical compatibility of the materials employed, so as not to cause any alterations to the historical appearance of the complex of San Benedetto Novello. The results of the assessment of the building in the improved status indicate that the proposed solutions allow a significant increase of the safety index up to the integral seismic protection at the life safety limit state for most of the relevant collapse mechanisms. In those cases where the required level of seismic upgrading has not been pursued the achieved performances are anyhow adequate for the reuse of an historical building. REFERENCES Crispolti C., 1648, Perugia Augusta, Perugia. Siepi S., 1826, Descrizione topologico-istorica della città di Perugia anno 1822, Perugia. Guardabassi M., 1872, Indice-guida dei monumenti pagani e cristiani esistenti nella provincia di Perugia, Perugia. De Angelis D’Ossat G., 1954, L’architettura sacra dal Medioevo in Umbria, in “Umbria nella storia, nella letteratura e nell’arte”, p. 36, Bologna. Pardi R., 1957, La chiesa di S. Benedetto in Perugia. In Palladio, pp. 42-44. Firenze: Giunti Editore spa Pardi R., 1975, Monumenti medievali umbri. In raccolta di studi di architettura religiosa. Perugia : Ed. Volumina. Giuffrè A., 1993, Sicurezza e conservazione dei centri storici – Il caso di Ortiga, Bari , Editori Laterza Liberatore D., 2000, Vulnerabilità dei beni archeologici e degli oggetti esibiti nei musei, p.118 Roma: CNR- Gruppo Nazionale Difesa dai Terremoti. Pardi R., 2000, La chiesa di San Benedetto in Perugia, in “Architettura Religiosa medievale in Umbria, Centro italiano di studi sull’alto medioevo”, pp.505-510, Spoleto : Centro italiano di studi sull'alto Medioevo Doglioni F., 2000, Codice della pratica per la progettazione degli interventi di riparazione, miglioramento sismico e restauro dei beni architettonici danneggiati dal terremoto umbro marchigiano del 1997, Bollettino Ufficiale della Regione Marche. Mastrodicasa S., 2003, Dissesti statici delle strutture edilizie, Milano, Hoepli. Rocchi P., 2003, Trattato sul consolidamento, Roma, Mancosu. Cifani G., Lemme A., Cialone G., Martinelli A., 2004, Linee guida preliminari per gli interventi di riparazione del danno e miglioramento sismico per gli edifici di culto e monumentali, In Edifici di culto parte prima, Bollettino Ufficiale Regione Molise n.7 del 01.04.2004,. MIBAC - Ministero per i Beni e le Attività Culturali, Circolare n.26 2 dicembre 2010, Linee Guida per la valutazione e riduzione del rischio sismico del patrimonio culturale – allineate alle nuove Norme Tecniche per le Costruzioni, Gazzetta Ufficiale della Repubblica Italiana . Mezzi M., Comodini F., Rossi L., 2011, Base Isolation Option for the Full Seismic Protection of an Existing Masonry School Building. Civil-comp proceedings, Chania, Crete, Greece.

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The International Journal EdA Examples of Architecture was founded in 2006. The Journal with the requirement of ‘peer re-

iew , was reated to disseminate s ienti papers pu lished universities and research centers, in order to focus attention on the critical reading of the projects. The intention is to create a place for a cultural de ate on interdisciplinar topics, with the aim to investigate issues related to different elds of stud rang-ing from histor , restoration, architectural and structural design, technolog , landscape and the cit

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Assessment and Seismic Improvement with Traditional and Innovative Technologies in the Reuse Design...

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