STRUCTURAL ANALYSIS OF HISTORICAL CONSTRUCTlONS
P. Roca, J.L. González, A.R. Marí and E. Dilate (Eds.)
\O CIMNE, Barcelona 1996
THE STRUCTURAL ANALYSIS IN THE METHOD OF
MONUMENTAL RESTORA TION
A. González
Diputació de Barcelona
Compte d'Urgel 187
08036 BarrelOlla
Spaúl
I wiU begin my pap er with some words of thanks to the organizlI1g
com mittee of this Seminar. This is not merely a formula of courtesy in rcpl)'
to their invitation. I also intend to express my recognition that it has been
considered s uit ab le to place the contributions within in the general context
of monumental restoration from the particular viewpoint of the struct ural
analysis of hi storie buildings.
Though it may su rpri se us , in most mectings such as this it is customary
to analyze the specific aspects of a scie ntific and technical nature without
dealing with the conceptual, social and methodological framewo rk in which
the intervention s are made . I therefore hope that this desire of the organizing
committee to set the discussions within a broader context wiU enrich the
results of the Seminar.
1 wiU not speak of the techniques of structural analysis of historical buildings.
That is the task of you, the specialists. J 0111)' intend , as an architect who
coordinates the multidisciplinary teams devoted to monumental restoration ,
to provide some ideas on the objectives of this analysis, envisaged from
the viewpoint of the discipline as a whole. They are reftections borl1 from
experien ce, some of them made in the company of my brother, Jos Luis
Gonzlez (to whom I owe so much of rny concern to improve my method of
thought each day).
Monumento.} restora.tion is a young discipline, with a history of hardly twn
hundred years. They have been, however, two hundred years of intense
controversy on the theoretical aspects concerning the nature of historical
buildings or the action taken in them , both with regard to the objectives
and the means to be used.
This permanent discussion J and the changes in the socio-cultural framework
in which it is situated J have produced an evolution in both the conceptual
contents and in restoration practice, which has beel1 espcciaUy in tensive in
the last decades of our century.
One reason for this evolution is urban growth and developrnent, the extension
2
STRUCTU H/\L ANALYSIS CF HI $TO R1CAL CONST RUCT10NS
cf industrializalion and the obsolescc llce a f historical buildin g typologies,
together with t he resu lti ng confli cts over the detcri oration ofthe environment
and the historical heritage.
Anothcr rcason is tha! a more profoll ud con cept ual analysis is made of the
nature, extent a nel divcrsity af th e built hi storical heritage th at mu st be
preserved. There is even diversity in the concept af conservation according
to the different cultural and social values af each co unt ry.
Howeve r , we mu st not forgct the development af therapeu tic and analytical
techlliques lhat are applicable to the conservation af thi5 heritage.
In t his new idea af restoration one must emphasize firstly the enhan cement
of the concep! of the Monument.
In the lIew restoratio ll the Monumellt can no longer bc understood from a
partial or fragme ntary view poi nt, wh ich has 50 oftcn produced t heories and
pradices with serio us shortcomings for a pproaching in ter vention in the bu ilt
heritage.
Cert ai nly, the first con di tio n of th e monument is its nature as a hi storical
document., as a result or a sce n ario of fact s, art s, techniqu es and cultures ,
a nd therefore its nature as a report.
But togct her with this natllre as a document , one must normally consider its
vaüd ity as a li ving architectural phenomenon: its capacity to pIay an active
cultural , social, urban or regional role in the presen t, due to its capacity to be
used and due to the presence of a r tistic, sp atial, techn ical anel cOIlstructional
vallles t hat are prope r to archi tedure or engineering.
And finally, as a conseque nce of these two aspects, its nature as a meaningful
element, because it lias symboli c and emblematic values fo r its user , valu es
t.h at mu st also be decisive, like the previo us ones, for t he co nsideration of
t he objectives and strategies of conservation.
The Roman amphithealre of the city of Nmes may serve as an example of this
triple essence. It is a hi sto rical docum ent of co nsider able im portance, and at
the same time a useful sp ace for t he current population an d an emblematic
a nd representative elcment of the city.
Anoth cr con ceptual aspect t h at has suff'ereel a consid erable evolution anel that
is now fashionablc in lhe internationa l for ums of monumental resto ration is
thal of Authenticity.
Th e Letter of Veni ce of 1964 says in its preamble t hat 1I11Umanity recognizes
its joint responsibiü ty for the conse rvation of the com mon monumental
h eritage and must aspire to transmit t hese monum ental work s with aU
the wealth of t.heir aut henticity". Thirty years latcr, the very concept of
monumental authen ticity continues to be discussed.
Recently, ex perts of IC OMOS at a meeting in Nara (Jap an) t ried to fin d a
A GONZÁLEZ I S!11Ic!ural :lIlaJys is in rnonumCJl!aJ rCSlOr.:ltlOn
definition that wouId be more respectfu l of the cultural and social valu es of
aU countries. It mu st not be forgoiten that in some easte rn count ries t he idea
of transmi ssion of a monument does not presuppose that it is untouchable ,
since in their opinion they may be destroyed and rebuilt without thereby
losing their authcnticity.
In our cu ltural context we have abo been dernanding a new definition of the
concept of authenticity for some time.
In ou r opinion, authenticity cannot be associated with the or iginality of the
m ateriaJ of which the monument is composed, but. rnust be associated with
the capacity of t-his material - regardless of its chrollology - to certify and
transmit as true (that is to say, as ((authe nti c") the sd of valu es and messages
of the monument, whether documentary, constructional, spatial, artistic or
emblematic.
The authenticity of a molding , a column or a space depends more on whether
it corresponds faithfully to the forms and intentions of its authors than
whet her the materiaIs of which these elements are composed are the original
ones or have beeo rc pl aced.
An examp le of this is t he Courtyard of the Lions of the Alhambra in Granada.
Possibly, most of t he materiaIs that we can see today in it (columns,
pavements, plaster-works, tiIes) are not of the 14th century but were added
in th e modern rcstorations.
However, if t he space corresponds to the original space co nce ived by the
Nazarene master builder, ir the babbling of the water sounds as it did then,
anel ir the beautiful G r a nada sun produces on the walls the interplay of lights
anel sh ades that bewitched our ancestors , who can deny the authenticity
of that Hispanic-Muslim architecture that we transll1it with pride (rom
generation to generation?
This enrichment and evolution of the concept of the rnonument is at the same
time having decisive consequences on the practice of restoratioll.
First ly, each day it seems more evident that. the restoratian of historical
constructions has littI e to do wit.h the restoration of other artistic heritages.
Today we can statc that ir the VerlUs of Milo were architecture... its
restoration would involve giving it back its arl11... anel poss ibly br in ging
its image up to date.
Co nsequ entl y, the inflexibility a f restoration cri teria conçcived in lhe image
af those applied in the restoration of other types of works has di sappcared.
There are no longer universal cri teria of monumental rcstoration that are
preestablis hed by schoo1s ar doctrines. They are defined in eac h case
according to the manument, its órcumstances anel the objcctives of j,he
act ion.
The resto ration af an ancien t car \ViU be very eliffere llt according to whether
the vehicle must be roadworthy. Tf it is only to be e>..hib ited, fhe recovery of
4
STRUCTURAL ANALYS1$ OF HI $TOIHCAL CONSTRUCT10NS
ih original beauty will suffice. If it bas to be roadworthYI lh e engine \ViII have
to be restored or replaced, and it will iJave to be adapt.ed to the prevailing
norms OH indicators, acoll stic signals, safety, etc.
l3ut it may occur that. lhe circumstances or the objcctives of the consc rvation
make a lho roughly differcllt treatment. advi sable.
The car in
gover mncnt. ,
in a military
\Vas to show
which admiraI Luis Carrero Blanco, head af the Spanish
was tllurdcred in Madrid in Oecember af 1973 was cxhibited
museurn just as it. was. Because the objective af the exhibition
the barbarism of that event, no one thought of restoring it.
This flexibility of cri teria according to the objectives has made it necessary
to establish with maximum rigour a method that ensures the scientific
correctness of the whole processo
I \ViU refer to the mcthod which we detlned some years ago in the Local
Architectural Heritage Service of the Provincial Council of Barcelona,
because it is lhe one which I know b est. I am sure tha.t in its essential
aspect it coincides with other methods.
The basic principies 011 which our method (which we have called the
" Objective Restoration " method ) is based are the foUowing:
Firstly, the e qu itable understanding and valuation of lhe three dimensions
of the triple essence of the Monument to which I have referred above: t he
aspects of lhe monumenl as a document or a work of architecture, and the
meaningful or emblemalic aspects. Also the concept of authenticity as it has
been defined.
Secondly, thal elemental principie in all the o rders of human activity, which
is often forgot ten: the need to adapt the means to the end. The aims or
objectives, which must always res pond to the social interest, are defined
according to the triple essence of the monument, its circumstances and the
sacio-cultural and historical environment of the action. Anel the means,
which involve a dual scientific and creative asped, are chosen according to
their efficiency for achieving the objectives, taking into account lhe available
resources.
FinaUy, as a third principIe, lhe acceptance of the universality of the metho d ,
but not of the criterioll of action, which, as we have seen, must be denned in
each case.
The method b ased on these principies distinguishes three main sections
ar phases of the adion ou the monumcnt: the previous knowledge, the
int ervention itself and, between the two, a reflection and determination of
the ends, means and criteria.
The essence aí these three phases is thi s: the greater the knowledge is, the
more objectivc the reftection \ViU be and the more appropriate (that is to say,
more effedive with less errort) the intervention.
Â.
GONZÁLEZ I Sl rUCIUr::l1 analysis 111 monurnClllal rcSlOralion
5
Th e knowlcdge phase is s ubdivided into two stages. The fir st is that of
preliminary diagnosis, in which on the basis of th e preliminary analys is of the
exis ting informatioIl , the scope and depth of the secon d stage of research'and
definitive diagnosis are considered. This stagc is therefore highly important
since it wili avoid eco llolll.ic waste alld permit a greater efficiency in the
second stage.
In lhe third stagc, oncc th c monumcnt has bcen understood in depth, t he
ob jectives, the available resources and the criteria anel means to employ in
its restoration or conservation are analyzed.
The fourth and fifth stages, as s ubphases of lhe intervention phase, envi sage
the projects, the car rying out of the work anel ot her indis pensabl e tasks,
such as the promotion o f the partici pation of society through the public
elissemination of the projects.
The stage of knowledgc, which is the one that 1110st interests us here ,
contains a series of projccts and studies t hat envisage the three aspects of
the monument: the documentary aspects, the co nst ruct.ional aspects, and
the emblematic aspect s.
The first include aU the studies that pursue knowledge of the monument
as a historical document o Firstly, the archaeology projects and the other
co ncu rrent sciences (nurni smatics, ceramography, phys ical anthropology,
dendrochronology, etc.), that is to say, the hi stori ca l stu di es t hat are based
on the analysis of the materiai s of the monumellt.
Secondly, the do cumentary hi storical studies, the analysis of the history
from the written , graphic, photographic or verbal documentation on the
11l0nument. And also, the analysis t hat can be provided by the history of art
or the history of construction.
They are not , of cou rse, c10sed studies, b ut s hould be related to each other
in order to contrast t he info rmation that they ge nerate.
An importanl
mOllulllent as a
of this study is
t he monument,
form s part.
aspect of the stage of knowledge is the analy sis of the
material object, of its physical reality in the presen t. A facet
what we have called the " physical-co nstructive analys is" of
of which the structural anal ys is dealt with in thi s Seminar
Before continuing , I wish to make a termin ological definition. I use the
word architecture (und erstoo d as art or as a work resu lting from this art)
as sy nonymou s with construction, a concept that includes both bu ildin gs
and other objects of engineering. To use this synonym generally faciLitates
the exposition and evielently does Hot involve any attempt to subordinate
or di sdain any of the disciplines that share with architecture the art of
construction .
Th e ph ysical-const ructi onal analysis is und erstood as the functional analysis
anel the analysis of the state of conser vation anel safe ty of the mOllument,
which is understood as a building system , and of the various sub systems,
6
STRUCTURAL ANALYSIS OF H!STOR1CAL CONSTRUCT IONS
elements, types of masonry and material of wh ich it is made up. An essential
aspect of this physical~constructive analysis, as I said before, is the struct ural
analysis.
Having considered th is methodological framework in which I reei t he
structural analysis of historical buildings should be examined, I will now
refer to the comments that I announced at t he beginning.
F irstly, I believe it is necessary to state my conviction that in order to
effective1y approach t he physical-construction al analysis in genera l and the
structural analysis in particular, it is indispensable to envisage the physicalmaterial reality of the historical building with a constructional mentality that
is as dose as possible to that of the period in which it was b uilt, avoiding the
current analytical mentality that shows ao excessive tenden cy to perform a
fragmenta ry analysis of that reality.
The current building culture is unlikely to be useful for the com prehension
of most of the monuments that we restore. The mental pat terns - the
mentality - generated by industrialization, the application of p roced ures
intended for new buildings, or the separation between strudure and enclosure
wallings, between permanence and stability, and other many fragmentations
that have allowed building culture to evolve positively in Qur cent ury, h inder
an understanding of the behavioural reality of the b u ildings of the past.
This does not deny th e validity of current science a nd technology, b u t merely
the fad that they are endowed with a timeless validity that is useful for the
comprehension of the past. It is clear t h at the current methods serve as
techniques of analysis of the material microreality af the monuments, a r to
develop sophisticated techniques of consolidation and reinforcement. But the
culture in which they are located is useless in itself for an understanding of
what t hey analyze and reinforce.
An example of this is the frequent erro r of terminological interpretat ion
consisting in not differentiating the so different meanillgs t h at t he term
"st ructure" has had in the 19th and 20th centuries, or interpreting a work
of ashlar arches and pillars in terms of the behaviour of rein forced concrete.
Another fundamental asped to take iuto accoun t in order to guarantee the
efficiency of the str uctural analysis is the interrelationship of all knowledge
about the monument, whethcr of a physical.construdion al nat ure - in which
the structural analysis is included - or of a historical nature .
As I said before, the physical·constructional analysis makes reference to the
m onument understood as a present physical reality, apparently regardless
of its historical nature.
However, this analysis should be made after
the hi storical studies, since these can provide many data t h at facilitate
the comprehel1sion of that physical-construd ional reali ty. Not only the
chronological data of the constructioIl, but the data they can explain : for
exampl e, the pathogcn esis, the origin of t he d amage. The warks of st rudu ra l
anaJysis, therefore, sho uld be programmed and performed in coordination in
t he knowledge stage of the met hod.
A. GONZÁLEZ I Structurnl ano.lysis in monumental reslorali on
7
It aIso occurs with the strllctllral intervention project that it canuot be
disconnected from the general restoration project, since this is approached
according to certain ends, rneans and criteria analyzed on the basis of the
com plex essence of the monument (as a document, as a work of architecture
and as a meaningful object) and of its overall problems.
The st ructural interventioll project shou ld HOt impose actions that may be
contrary to the objectives anel cri teria of the general ilction consiclcrccl on
the basis of the general analysis of the monument. An example: a correctin g
structural restoration of damage Of physical-material anomalies must take
into account the documentary and meaningful aspects that the externaI
manifestation of pathologies may have, which should perhaps be maintained
apparent as an illformative or even commemorative datum.
With respect to the structural intervention project, 1 believe it is suitable
to cite the recommendatiolls that arose from the discussion of the Ravello
Group, in which I have the honor of representing Spain. lt is a working group
sponsored by I COMOS and other international organizations that met last
May in that Italian town to discuss the structural aspects of restoratioll.
These are the recommendations:
"The structuraI restoration project"- says the elocument of Ravello - " must
be based on a methodology not of numerical codes but of methodological
codes."
"The project must include an expIanatory report which includes the
description of the research program , the causes of the damage and the
deterioratiou, the evaIuat ion of the safety, the comparison between possibIe
alternatives and the justification of t he options finally chosen , anel a
monitoring plan to be applied in the course of the work, indicating the
purpose of each control anel the instruments to be used. The controIs shoulel
continue after t he work has finished in order to check the results."
"Concerning the evaluati on of the safety" , continues the elocument of
Ravello , "it must be based on t h e joint consideration of the historico-critical
analysis of the construction in its context, the qualitative evaluation based
011 an examination of the building, and t he t heoretical analysis through
mathematical models. The conclusions that are obtained and that may be
incorporated in the intervention projects mllst be based on a criticai analysis
of the results of the process , without losing sight of the relative importance
of the diverse information that has been obtained."
Concerning the cri teria of the project of restoration of the structural as pects,
the document advises: " No intervention should be made until it has been
checked that the safety leveis are actually insufficient. The intervention must
be proportional to the safety objectives and therefore as minimal as possible.
As a general criterioll, the trend must be to conserve and respect the original
concept and techniques of the structural system of the monllrnent anel,
when possible, the measures taken should be reve rsible, so that they can
be rep laced by more suitable measures in the light of new knowledge".
8
STRUCTURAL ANALYS IS
or HI STOR ICAL CONSTRUCTIONS
"In no case wiU measures be chosen whose result cannot be verified ar that
cou ld produce harmful secondary effects. Concerning the dilemma between
traditional techniques and new technologies ) each case mu st be cons idered
individuaU y, giving preference to the techniques that involve the greatest
res pect for the original work and that are the least aggressive ."
" All the materiais used in restoration af a st ructural type mu st be examined
in d etail, and ooe must have documented evidence not anly of their
characteristics, but also of their compatib ility with the original materiais,
in arder to avoid as (ar as possibl e harmful secondary effects. "
" Furthermorc, the difficulty af evaluating real safety levels and the possible
benefits of th e intervention may suggest an intervention in stages with lhe
subsequent adoption of cornplern entary or corredive meas ures. Thus , the
meas ures can be minimal an d , especially in the prese nce of evolutionary
phenomena, they can be adapted graduaUy according to response of the
strudure."
case~" , concludes th e document of Ravello, "upon finishing the
the organi:mtion responsible for the conservation should be given the
complete docum entation and a description of the projeds and the general
lines of maintenan ce."
"In aU
wo rk ~,
I wiU fini sh hy calling the attention to some points that see m to me to be
essential at this important time for the defini tive generalized io staUation of
structural allalys is in the area of monumental restoration.
The first poiot is the need for a safety code that is applicable to the
monuments a nd is different (rom that which is applicable to the design of
new buildings anel structures. In thc latter case, the safety caeffi cients must
take into account the un ccrtainty of the good execu tian of the building ar
th e projected st ru ct ure. However , in t h e analysis of the safety of historical
construction s, the checking of t heir real behavior over a long history is a most
importaot empirical e1ement that can permit t he modification of the res ult s
obtained from the t heoretical calculations.
I a lso wish to cali the attention to the need, in parallel to the advances
in techniques and methods of strudural analysis, for mcchanism s to be
established that enable easy preliminary diagnosis, with the greatest possible
precision , of wheth e r these analyses need to be applied.
An indiscriminate generalízation of stru dural analysis m et hod s call make
the restoration process m ore expensive, with t he consequent negative effeds.
Thus, the compan ies specialized in carrying out the analy sis sho uld not be
the same as those t hat prescrib e its need , something that is increasingly
co mmon, at least in our country.
F'urthermore, both the analytical methods and preliminary diagnosis
m cthods should be designed and adapted b earin g in mind their application
to rnonuments of me dium or low complexity because they are t he most
abundant. A techn ique of st ructural analysis designed solel y a ccording to
large monuments may be ineffedi ve for the whole discipline of monumental
A. GONZÁLEZ I SlruClural analysis in monumcntal rc:.l0r.llion
9
restoratioll.
And fina lly, I put to your conside ration the advisabiüty of not encouraging
a new culture of Hstrudural restoration" as an end in itself, apparently
regardless of the essential objedives of monumental restoratioll. It is in
this sense that I c1aimcd in the Ravello Group - and now J am doing; it here
- that we should BOt speak of strudural restoratioll , but of the C:strud uraJ
aspects of restoration" .
I hopc that this Seminar wiU provide a11 the spccialists gathered here with
spccific technical knowlcdge to make their work more effective cvery day.
And J also sincerely hope that the indispensablc reflection on resloration
in general wiU aUow them to situate this particular knowledge in a wider
II1cthodological frarnework whose purpose is to guarantee the pro tectioll and
the coUective enjoymellt of the monumental heritage that we have inherited
and that we must jointly transmit to future gencrations.