Associazione Geotecnica Italiana

L

i

a

,Antonio Borri*, Antonio Avorio*, Giovanni Cangi**

SummaryThis article contains a concise report of criteria and methodologies for repairing and consolidating masonry buildings

in historical centres damaged by the 1997 Umbro-Marchigiano earthquake.

The described procedures are containep in the «Handbook for the post-earthquake rehabilitation and reconstruction

ofbuildings", promoted by the Regione ddlrUmbria and directed at designers involved in the reconstruction process.

The aim of this work is to provide opetlative guidelines of an interdisciplinary nature, involving professionals from nu-

merous disciplinary areas.

1. Introduction-

Whilst defining regulations and criteria for thereconstruction process, the Regione dell.Umbriawas keen to draw our attention to the protection andimprovement of historical centres and traditionalbuilding typologies, by promoting and editing ahandbook directed mainly at professionals operat-ing on historical buildings in Umbrial.

With the aim of making the Regione dell'Um-bria.s initiative known throughout the technical andscientific community, which has the greatest interestin such an issue, this article concisely relates someprinciples and typologies of intervention containedin the chapter on methods of intervention. Thischapter deals in particular with interventions on tra-ditional buildings, which, even when lacking therequisites of monumental ones. are neverthelessworthy of attention both as individuai units and forthe unitary whole that they help to define. The text,therefore, illustrates a reconstruction process whichbears in mind aseismic safety and at the same timethe protection of that architectural, historical andenvironmental heritage that the earthquake-pronearea is so rich in.

2. Aims and methodological aspects

The typology and methods of intervening onmasonry buildings, illustrated in the above text,comply with the general principles listed in the spe-cific recommendations ofthe Regione dell'Umbria2and of the Minister for Arts and Culture3

Such provisions are generally of a conservativenature. The aim in particular is to direct designerstowards interventions which combine greater safetywith historical and environmental aspects, whichencourage the reuse of traditional materials andtechniques, the need for an in-depth analysis of thebuilding, and the quest for a satisfactory level ofquality in terms of intervention.

The operative strategy therefore adopted in-volves maintenance, at the same time, respondingto the needs of aseismic behaviour .

In the ambit of "compatible reconstruction..,there is less certainty as to the real efIectiveness ofpartial consolidation which makes the masonrybuilding hybrid, with a mixed behaviour (and attimes inconsistent) between that of historical ma-sonry and that of r .c. elements inserted therein.

To be able to provide a correct diagnosis, it isparticularly important to analyse the building typesand gain an in-depth understanding ofthe structure( often concealed by a series of interventions overtime), preliminary operations which help to pin-point the key to the operation.

If we follow this course of action (in the tradi-

tionallogical sequence: diagnostic-diagnosis-ther-apy), often, at least conceming structures with ade-quate masonry , light, local interventions are suffi-cient to give (or give back) the building the pre-es-tablished level of aseismic safety .

In the handbook particular importance is givento the methods of achieving quality masonry , indis-pensable for counting on adequate mechanical per-formance, and to the links between difIerent ele-ments and different organisms, given the impor-tance of this aspect on the analysis of possible kine-matic collapse mechanisms.

An error that we observe only too often in build-ings undergoing "adjustment'. is when the floors arestifIened without considering whether or not the

.Departrnent orcivil Engineering and Environrnent, Faculty orEngineering, University or Perugia, Italy.

..Freelancer, Città di Castello (PC), Italv.

RWISTA ITALIANA DIGEOTECNICA 4/2001

GUIDEUNES FOR SEISMIC RETROFlrnNG OF ANCIENT MASONRY BUILDINGS 113

common and if anything visible on the lower part ofthe building where the plaster connects with thefoundations, which are not as rigid as the overlyingwa". In these areas, the condition of mortar is evi-dently bad owing to the masonry's constant satura-tion caused by the upward infiltration of water andimpermeability of the concrete. Immediately abovethe foundations, the earthquake therefore encoun-tered a ho"ow wa", where the external wa"s wereconstituted by several centimetres of reinforcedconcrete, while the heavy filling no longer possessedstructural capacity .

masonry structure is able to bear horizontal actionsattributed to it.

Priority is hence given to rectifying structuralweaknesses. A preliminary survey suggests a strictlynecessary intervention involving the reconstitutionof resistant mechanisms, if deteriorated, or theirstrengthening if deemed inadequate, alongside theintroduction of new supports where substantialstructural weaknesses have been pinpointed.

Regarding the text in question, particular atten-tion has been lent to the behaviour and possible in-terventions on serial buildings, characteristic of his-torical centres, given the lack ofbibliograph~c refer-ences and complexity of the issue, very differentfrom that ofthe isolated building. 4. Observed kinernatic collaDse rnechanisrns

3. Quality of masonry and seismic behaviourIn buildings where the quality of masonry

proved to be adequate, the damage verified was of-ten ascribable to collapse mechanisms characterisedby the typology and quality of connections betweencomponents of the building itself; connectionswhich, in ordinary static conditions and with the ac-tion ofjust loads, marginally contribute to the over-ali stability of the organism, but in case of earth-quakes assume a decisive role.

In fact, seismic action implicates the onset ofhorizontal forces which the unilateral constraints,generally ideai for resisting verticalloads, are not al-ways able to withstand. Other types of constraint aretherefore needed here and their absence would pro-duce detachments that couldeventually lead to col-

lapse.Out of piane collapse mechanisms have been

observed in a variety of forms, linked to the wall'sparticular constraint conditions. As to historicalbuilding, unmodified by recent interventions, wehave observed horizontal cylindrical hinges aroundwhich revolve entire unheld walls and flexural col-lapses with paraboloid profile in the case of panelsconstrained on three sides. Fig. 1 shows flexural fail-ure in a panel tied to the orthogonal walling, in thepresence of masonry panels effectively tied to theorthogonal walls and with the top side not held byany device.

Fig. 2 shows how the out of pIane behaviour ofthe individuaI units is not largely influenced by thepresence of other buildings. Under the same condi-tions linked to the particular site and building typol-ogy , we have often observed how terraced housing,in the presence ofpremodern support mechanisms,behaves decidedly better in the face of seismic phe-nomena.

Note how the ..historical" solutions tend tomake the neighbouring buildings collaborate (forexample, through retain arches): an antithetical for-mulation compared with current regulations, whichinstead stipulate the creation of joints for the struc-turaI separation of buildings.

Whoever has performed surveys on damagedbuildings hasno doubt noted the importance of themasonry's quality. Whether in large towns or sma"mountain vi"ages, the worst damage has been ob-served in buildings constructed with shapelessmasses of stones or non structural perforated bricks.The rubble visible at ground level and the scantyportions of building sti" standing are evidence ofbad-quality assemblage and precarious mortar .

In these cases we cannot speak of kinematic col-lapse mechanisms, since the masonry wa" does notbehave in the same way as a monolithic solid. Dur-ing an earthquake the wa" crumbles, not possessingan adequate level of internai connection.

Cracks are extremely indicative of the quality ofmasonry .A panel with irregular fractures through-out indicates disconnected masonry with sma"stones arranged in a chaotic fashion, without con-sidering the horizontality of lines. Isolated cracks,on the other hand, reveal monolithic behaviour: themasonry is subdivided into two or more elementswhich maintain their form and shift reciproca"y be-tween themselves. In the latter case, the problemshould be sought out in the overa" functioning ofassemblage and connections rather than in the qual-ity ofthe masonry.

In the case of plastered wa"s, when judging theovera" crack situation we must bear in mind the dif-ference in behaviour of masonry and the layer ofplaster, a particularly marked difference in the caseof thick cement (unreinforced) plaster, often visibleand, at times, entrusted with improbable structuraltasks. Owing to the concrete face's greater rigidity,it absorbs a large part of the initial stress.

In buildings recently consolidated with the tech-nique of reinforced plaster, most of the damage ver-ified is ascribable to poor functioning of the systemformed by the originaI wa" and two r .c. plasteredfaces. Damage due to in-plane seismic action is less

OTTOBRE -DICEMBRE 2001

114 BoRRI -AvoRIo -CANGI

Fig. 1 -Wall constrained on three sides in the presence or in-plane orthogonal stress. The photo and drawing below reveal

the complete absence or connections between the two races or masonry .

Fig. 1 -Parete vincolata su tre lati in presenza di sollecitazioni ortogonali al piano. Nella foto e nel disegno in basso si può notare la

mancanza totale di collegamenti tra le due cortine della muratura.

~ ~~'5'

;.-9

ly r-,.1

~

rol~

,I'ln

-.J

Fig. 2 -Crumbling fa~ades and historical solutions to the problem.Fig. 2- Crolli dei prospetti e soluzioni storiche al problema.

RWIST A IT AUANA DI GEOTECNICA

115GUIDEUNES POR SEISMIC RETROPI1TING OP ANCIENT MASONRY BUILDINGS

and roof block (and hence a horizontal force ap-plied in the baricentre of the roof itself) produces arigid rotation of the ceiling, which tends to rise upfrom the wa". Therefore lost is the restraining ac-tion exercised by the stringcourse on the underlyingmasonry , which co"apses under acceleration action.

It is interesting to observe the co"apse types dueto coplanar actions, more frequently verified inearthquakes of Umbria and the Marches.

Case A represented in Fig. 5 is characterised bythe rotation of a wedge-shaped masonry element.The closer its diagonaI profile is to the vertical, thepoorer the quality of masonry .Case B reveals seismicstress undoubtedly greater than the former. We canobserve the actual sliding of an even Iarger portion ofmasonry: the nature of the kinematic mechanism isclearly evident from the reciprocal position of cracks.

Mechanism C can be observed alternately withmechanism B and shows masonry of adequate me-chanicaI characteristics in that even moderate ten-sile strength can avoid Mechanism A occurring.

Of considerable interest was the analysis of dam-age mechanisms in the presence of apertures. As anexample, Fig. 6 shows the interpretation of damageto a building in Busche (Gualdo Tadino) through ananalysis of Kinematic mechanisms of the wa" pIane.

The sequence shows the fa~ade wa"'s subdivi-sion into macroelements. Diagram I i"ustrates therotation of the left-hand end part, singled out by theline of apertures (sector A of rotations). The sameapplies for the right-hand end portion, the momentthe seismic stress changes direction. Diagram 3 dis-plays a sliding kinematic mechanism (sector B oftranslations) of the triangular portion, which no

More complex is the case of buildings recentlyretrofitted with the introduction of new concretef1oors. The extent of damage has highlighted thecollapse of entire panels or substantial parts ofthem, while often the f1oor has remained intact.This new collapse type has been tackled accordingto two levels of interpretation: kinematic and dy-namic. The aim of the analyses is to highlight thebehaviour of the f1oor slab -wall system, which doesnot appear to be adequately represented by theusual methods of structural analysis.

Fig. 3 presents a kinematic interpretation withthe singling out of macroelements in the wall whichremain integraI on their inside and whicn shift re-ciprocally around hinges. Above is represf;nted thecase of a rigid f1oor: not being able to adapt to theprofile ofthe top part ofthe wall, it decompresses oreven discharges the perpendicular wall subjected tooverturning. The case demonstrates a f1exural be-haviour of the slender load-bearing wall, owing toaction from tfìe left, while with action from theright, a shear behaviour prevails. In the same Fig.,as a comparison, is an example of a deformablef1oor (with a two-way framework). Here, we can seethe positive effects of a greater deformability.

Fig. 4 displays a qualitative dynamic interpreta-tion of overturning in the presence of rigid f1oors.Here, we observe how the dynamics of seismic stressand, in particular, the propagation of accelerationsfrom the foundations to the top of the building,cause "whiplash" to the upper part ofmasonry, po-sitioned perpendicularly to the direction of theearthquake. In such an instance, the presence of arelative acceleration between the top of the walls

Seismic action

w ~

IAI

Figo 3- Kinematic interpretation or out-or-plane mechanism in the presence or a rigid roor elemento

Figo 3 -Lettura statica del meccanismo fùori del piano della parete in presenza di un elemento rigido in copertura.

OTTOBRE- DICEMBRE 2001

BORRI -AvoRIO -CANGI116

~

JV

\ì .\~

~~r.

~

Fig. 4- "Dynamic" interpretation or out-or-plane mechanism in the presence or a rigid roor element.

Fig. 4- Lettura "dinamica" del meccanL5mo fùori del piano della parete in presenza di un elemento rigido in copertura.

5. Kinematic collapse mechanisms in terraced

housing

In the case of terraced housing that has not un-dergone substantial modification, we have pre-dominantly verified partial damage and collapseswith crumbling corners, cymatia and roofs, whilethe rest of the structure has remained intact. Thelimited effectiveness of links between the masonryelements is such that the terraced housing as awhole does not present a uniform behaviour: eachportion supports itself and what rests directlyabove it.

Ionger benefits from the restraint of the Ieft-handIoad-bearing end, now detached.

Note how the pinpointing of sectors is Iargelyconditioned by the Iayout of apertures and presenceof arches on the ground floor .

This behaviour type ofwaIIs subject to in-planeactions is verified in both isolated buildings and ter-raced housing.

In the case ofwaII pIane mechanisms, we can af-firm that considerations evolved through the sin-gIing out of monolithic elements, are significantonly if the quality of masonry is adequate enough to

avoid disintegration.

RWIST A IT ALIANA DI GEOTECNICA

BoRRl -AvoRIO -CANGI118

1---L-~ ~--=-~ 45° Sector o' rotationsI A Sector o' traslation

( /~ ~ "" /' SeismicV / / A""" ~ actlonI ;:;1 /

1/ o

'l''7d,

~

G,/

I

Fig. 7- In-plane damage mechanisms for terraced housing.

Fig. 7- Meccanismi di danno nel piano per edifici a schiera.

ploit the retaining action on the two sides. However ,this occurs only when the fa~ade of the celI isaligned with those of adjacent ones. The oppositecase involves one or two sides unrestrained as indi-cated on the right in Fig. 8.

The kinematic mechanisms of in-plane horizon-tal sliding are instead triggered offby seismic actiongreater than that which triggers the above rotationsand interests a wedge, indicated here as "sector oftranslations" (sector B), forming a wider angle withthe vertical in comparison with sector A. Models ef-fected on typical dimensions and typologies haveprovided numerical results from which it is possibleto establish that for current masonry typologies,earthquakes measuring VII-VIII degrees on theMCS scale (for which a value of C has been adopted(multiplier of inertial mass) equivalent to 0.20 -0.24) produce the crisis owing to the rotation of sec-tor A, while in order to trigger the kinematic mech-anism of translation of sector B, earthquakes re-quire an intensity higher than VIII (and thereforevalues of C generally higher than 0.28).

This is confirmed by surveys carried out on var-ious residential blocks of historical building, wherethe non-bounded cells rev,eal fractures that system-atically reappear, though in each case with varyingdegrees of instability, according to the distributionof apertures on the various f1oors and where sectorB's collapse is a result of activation of sector A's kin-ematic mechanism. Only in cases where the qualityof masonry is decidedly better (adherence is suffi-cient to avoid subdivision ofthe wedge near the freeside) can we verify the presence of sliding. Gener-ally, however, the level of damage is fairly con-tained, proving how kinematic mechanisms whichinterest sector Bare less violent.

a) Actions perpendicular to the wall plane: over-turning of the single cells.In terraced housing, the extent of damage dueto actions perpendicular to the walls is largelythe same as that of isolated buildings.

b) In-plane actions: effects of seism on the fa<;adewall and main inside wall.Parallel towhatwe may observe for a single ma-

sonry wall, we can examine the in-plane response ofthe terrace block in relation to possible kinematicmechanisms of rotation and translation. The formerare triggered offby moderate horizontal stress, suf-ficient to isolate from the rest of the masonry struc-ture a wedge-shaped macroelement diverging up-wards. The wedge, determined by the quality of themasonry and presence of apertures, tends to rotatearound the hinge produced by the particular con-straint conditions (chains, retaining and restrainingelements). For the sake ofbrevity, this wedge is in-dicated as "sector of rotations" or sector A. In thisway, the main effect of the kinematic mechanism isemphasised, essentially consisting of a rigid rotationofthe wedge. Walls sensitive to this collapse type aregenerally those of the end cells not bounded byother cens. Due to actions originating from the cen-tre of the terraced housing, the end cen behaves asan isolated structure. It therefore offers no guaran-tee of stability in the face of horizontal seismic ac-tions. Such an occurrence is sometimes preventedby premodern aeseismic support mechanisms whichprove to be very effective. In fact, to quash the ten-dency to overturn it is often sufficient to employ de-vices which restrain (tie-rods) or retain ( proppingarches, buttresses).

The units that benefit from the restraint of thebordering cens are more stable, being able to ex-

RWIST A IT ALIANA DI GEOTECNICA

GUIDEUNES FOR SEISMIC RETROFITrING OF ANCIENT MASONRY BlJILDINGS119

Seismicaclinn o=:>

~ ~,,/ ,

~~~ticalline ~

OverlurninR HinKe in presence a contrasl e\ement

Fig. 8 -Conditions which influence in-plane collapse in terraced housingFig. 8- Condizioni che influenzano il colLasso nel piano nell'edilizia a schiera.

With regard to both kinematic mechanisms ofsector A and sector B, we can thus affirm that eachcell absorbs the actions transmitted by its precedingstructure ana- discharges stress onto the successivecell (buttress function). The most serious problemsare hence located in walls which have a free end: inthis zone the presence of apertures is therefore crit-icaI.

6.1. Chaining intervention~

Owing to the considerable influence exercisedby the apertures on the formation of wedges, pre-carious situations are verified, for instance, in blocksused for business purposes where the ground floorrooms are transformed and given large openingswhich make the wall inadequate to resist horizontalseismic stress.

It is interesting to note that transferring the ob-servations made for the far;ade wall to the centraIwall of the block (generally possessing fewer open-ings), the extent of damage is much less significant.On the whole, the centraI wall performs a decisivestatic function and acts as a backbone, stabilised bythe perpendicular walls. If many terraced blockshave managed to resist seismic action, it is probablydue to this greater "integrity" of the backbone wall.

As to the factors determining the formation ofhinges in one point rather than another, we can af-firm that it is generally the geometric particularitieswhich dictate the conditions of the extremities. Thehinge around which sector A rotates is identified bythe difference in rigidity introduced by the staircasewall. Such a point also delimits the line below whichthe flow of tension may reach foundation level with-out provoking sliding.

In the absence of toothing between the fa<;adewall and perpendicular walls, when even the an-chorage of the floor slabs appears ineffective, thewall's resistance to perpendicular actions is essen-tially linked to slendemess; in these conditions thewall offers little resistance to overturning ( 1 st dam-age mode) and may be pushed beyond the limit ofequilibrium even by relatively moderate forces. Inthese cases, the wall's low resistance to overturningcan be effectively compensated through a better ar-rangement of restraining elements. In fact, the con-straint produced by the wooden floor in the face ofseismic action is a unilateral type: the wall cannotshift inward and is prevented from shifting outwardonly by the friction produced from the effect of thefloor's weight on the wall. It is obviously not possibleto rely solely on the effectiveness of friction, nor onthe toothing between perpendicular walls.

The vulnerability of the building is thereforestrongly conditioned by damage mechanisms of thelst mode, and their control is the prime aim of anypreventive intervention. In this report, for the sakeof brevity, we will only be examining the chainingintervention, in an endeavour to pinpoint and de-fine the criteria of placing and dimensioning. Tothis end, it is necessary to follow a parallel course,flanking kinematic analysis with the design solution:to introduce a chain means to modify the resistantscheme, therefore, it is important to re-examine thestructure in order to identify the new damage mech-amsms.

The chains are generally positioned at floorlevel. The tie-rod must transfer to the transversalwalls the force which would otherwise cause over-tuming of the outer wall. The mechanical problemthus involves pinpointing a channel for this trans-mission, which neither presents weak rings nor trig-gers dangerous concentrations of stress.

6. Examples of plates

Below is a summary of some indications andplates regarding: a) chaining interventions; b) roofstringcourses.

OTTOBRE- DICEMBRE 2001

120 BoRRI -AvoRIo -CANGI

Tie-rods positioned near the transversal wallsare the most efIective, but it is often necessary topIace anchors in intermediate positions also. Thelatter solution should also be considered when thelength of the tie-rod is not sufficient to guaranteethe formation of a discharging arch (created by seis-mic thrust) inside the wall. Generally, the distanceshould not be more than 10 times the width of thewal1 (and in any case not more than 5 m) and suchdistances between two centres should also be evalu-ated in relation to the existence and frequency ofpassing elements.

The damage mechanisms which interest ma-sonry wal1s stressed by coplanar seismi~ actions (2nddamage mode) are triggered easily, but general1yimplicate rather high multiplier valu~s of col1apseand hence rarely reach the point of col1apse. Thewal1, fractured by in-plane horizontal action, slidesover itself or revolves around a hinge due to the ef-fects of seismic action but, if wel1 constructed, doesnot loseits load-bearing capacity.

If the wal1 has been built according to regula-tions, this form of damage can be defined as ductile,in the same way as constructions in r .c. and steel: infact, the cracks in the masonry wal1s can be severalcentimetres wide without there being a dangerousloss of equilibrium.

Another very important aspect regards the dis-tribution of shearing actions on the brace wal1s. Inthe case of rigid floors, the generaI procedure of cal-culation currently used permits the apportioning ofhorizontal forces according to the rigidity of the var-ious load-bearing wal1s. In the presence of wooden,steel and brick floors, it is necessary to attribute eachportion of wal1 only with horizontal forces producedby verticalloads, which in static conditions rest onsuch a portion (areas of influence).

The chaining intervention also has positive ef-fects in the face of second-mode kinematic mecha-nisms. However, in-plane resistance only increasesif the tie-rod reaches portions of masonry where theaction transmitted by the tie-rod head can be dis-charged to the ground.

6.2. Roof stringcourses

The effectiveness of roof stringcourses stronglyconditions the safety of the building. It is not possi-ble to interpret the stringcourse's action in relationto 1 st and 2nd mode mechanisms: in fact, the actionof these devices is much more complex and their ef-fectiveness depends on how they reduce the thrustof the roof beams, distribute verticalloads in staticconditions, apportion horizontal forces producedby seismic action, link the perpendicular walls, andachieve a box-like behaviour. In actual fact, it is im-

possible to obtain alI these characteristics at thesame time, save through interventions that coulddeform the masonry structures, with serious dam-age, if badly performed, to the safety of the build-ing. It would therefore be appropriate to focus onjust some of the "fundamentaI" functions, Iike theIink between waIIs, controI of thrust and attainmentofbox-Iike behaviour.

Two already experimented soIutions are pro-posed in pIace of the classic r .c. stringcourses: thereinforced masonry stringcourse and chain-string-course in steeI (plates C and D).

While the first contributes to the apportioningof Ioads, the purpose of the steeI stringcourse is toreduce the thrust of the roof and Iink the verticaI

walling.Summarised below is a Iist of the positive and

negative characteristicsof the two systems:Stringcourse in reinforced masonry:

-requires dismantling of roof;-easy execution on horizontaI surfaces; it is more

difficult to follow the sIope of the gables;-has a good verticaI deformability which permits

it to discharge weight onto the underlying ma-sonry, avoiding the so-called "beam effect" ofthe r.c. stringcourses [7];

-the reinforcement may be used to restrain theeaves or brick or stone cornices;

-can be made of brick or stone in respect of theaesthetics of the building;

-does not create problem of cold bridges.Stringcourse in steeI:

-can be effected with or without dismantling theroof;

-can be applied to a single waII or the entire topperimeter so as to form a reinforcement ring;

-in masonry with horizontaI or very irregular cur-vatures, it is necessary to mould the section barand IeveI the area of support;

-does not re-distribute roof thrust onto portionsof waII, which continue to receive the same ver-ticaI and horizontaI Ioad, and hence does notnegatively alter the building's resistant mecha-rnsms;

-in unplastered buildings it has strong aesthetic

impact; ,-requires Iittle maintenance (anti-rust treatment)

if not covered with plaster;-intervention is reversible.

The soIutions Iisted in plates C and D undoubt-edly provide devices for the reduction in thrust ofthe roof structure's orientation, for Iinking the waII-ing and, in the case of the reinforced masonrystringcourse, for distributing verticaIloads withoutsignificantly altering the overaII functioning of thehistorical masonry building.

RWIST A IT AUANA DI GEOTECNICA

121GUIDEUNES POR SEISMIC RETROPI1TING OP ANCIENT MASONRY BmLDINGS

tage from seismic risk, of lhe Minister for Arts, Culture andEnvironment, and subsequently adopted, with some integrations, by the Higher Council ofPublic Works).

Conclusions

For the sake of brevity, this article relates onlysome of the criteria and methodologies contained inthe text arranged for the Regione dell'Umbria. It isnecessary to refer to the handbook for a more in-depth examination of the work carried out.

Manuale pratico per la riparazione diantichi edifici in muratura

Notes

SommarioNel presente articolo vengono riportati, in fonna sintetica,

alcuni dei criteri e delle metodologie per gli interventi diriparazione e consolidamento degli edifici in muraturaappartenenti ai centri storici danneggiati dal sisma umbro-marchigiano de11997.

Le procedure descritte sono contenute nella pubblicazione"Manuale per la riabilitazione e la ricostruzione postsismicadegli edifici" promosso dalla regione dell'Umbria e diretto aiprogettisti impegnati nella ricostruzione.

Lo scopo è quello di fornire indicazioni operative di carattereinterdisciplinare coinvolgendo professionalità proveniente damoltePlici aree disciplinari.

1 The Volume was coordinated by Prof. Francesco Gurrieri,

Dean of Florence's Faculty of Architecture, and the chapter"Repair and consolidation of masonry buildingsM was entru-sted to Prof. Antonio Borri of~rugia's Faculty ofEnginee-ring, with the collaboration of Ing. Antonio Avorio of thesame Faculty and Ing. Giovanni Cangi, freelancer in Città di

Castello (PG).2 Regione del1'Umbria, Recommendations for desig-ning and effec-

ting reconst7UCtion and restoration processes, with repair and seismicimprovement, compatible with the protection of architectural, histori-cal and Imvironmental aspects.

3 General Instn-:ciions for drawing up restoration projects for architec-

ture ofhistoric-artistic value in a seismic zone, approved on 29/10/96 bv the national Board for the protection of Cultural Heri-

01TOBRE- DICEMBRE 2001