Iscarsah newsletter 5 Layout 1€¦ · Khalid El Harrouni, Règlement parasismique des constructions en terre au Maroc (RPCT) Scientiﬁc reports Randolph Langenbach, Rubble Stone

Message of the President of ISCARSAH Stephen Kelley

y dear friends and colleagues!I am writing you from the island of Bohol in the Philippines where I have been consulting with UNESCO and local authorities on natu-

ral disaster damage assessment to cultural heritage brought on not only by the October 2013 Bohol Earthquake but by TyphoonHaiyun/Yolanda which struck in November. The needs here are great for monetary as well as expert technical assistance. The cultural her-itage here is rich and our attention has been focused on a group of Spanish-era churches that are 2 - 300 years in age and composed of tripleleaf masonry walls faced with coral stone that are buttressed and roofed with timber framing and roofing of either clay tile or corrugatedsheet metal. It will be interesting to see if the global community can find ways to aid in restoration and seismic retrofit efforts.It will also be interesting to see if ISCARSAH or other committees can participate as well.

ISCARSAH is in the planning stages of development of a Conservation Engineering training course that would be taught as a module within alarger training course on Risk Preparedness with the International Committee on Risk Preparedness (ICORP). This idea was first discussedduring the ICOMOS GA in Paris in 2011 and was further developed at the recent ICORP meeting in Kathmandu. The idea is to have a well-de-veloped course that would be tailored to regional (climatic, technical, cultural, political, etc.) needs and utilizes regional ISCARSAH instruc-tors along with a core group of experts. The initiative is being spearheaded by Vice President Görün Arun. Please contact her directly orthrough the listserv if you would like to participate.We are finding that the ISCARSAH Facebook and Linkedin sites are a great outreach tool for potential members in the Middle East and Asia.The Facebook page is followed by 369 and the Linkedin page has 179 members. These followers and members grow almost daily and mostare not members of ISCARSAH. We are looking for someone who can dedicate time to the administration of one or both of these sites.The administration has thus far been fairly casual because they are handled by hopeless amateurs (me!).Do we have associate members who might want to take on this task and give this area the attention and expertise that it so richly deserves?Please let us know if you are that person.The year 2014 will prove to be a busy year for ISCARSAH. We are planning to have two meetings: during the SAHC2014 Conference in MexicoCity (week of October 13) and during the ICOMOS General Assembly in Florence (week of November 9). Please stay tuned to the listserv andISCARSAH website for details.We will soon hold an election for positions on the ISCARSAH bureau. I will stand for my last term as President. Both Görün Arun and MayaSegarra-Lagunes will also stand for Vice President. Debra Laefer will stand for Secretary General. That leaves one VP slot that is available. Ifyou are interested please contact me directly. I would like to thank Lyne Fontaine, outgoing SG, for her hard work and fidelity over the pastsix years. I would also like to thank Peter Elliott, outgoing VP, for his hard work and fidelity over the past three years. We as a committeeshould think boldly about the 2017 transition to a new President. Please let us know if you might be interested.

Sincerely,Stephen J. Kelley

President - ISCARSAH

newsletterDecember 2013

1

M

The left transept of Santissima Trinidad Parish Church, a cruciform church constructec circa 1800 in Loay, Bohol, Philippines. This is one of a handful ofSpanish-era churches that were left standing after the October 2013 earthquake.La Purisima Concepción Church located in the fishing village of Guiuan, Samar was constructed in 1718. This is one of the few churches in the Philippineswith its original altars, carvings, painted ceiling, and architecture still intact and was extensively decorated with natural shells embedded in the interiorwalls. These photos reflect the extensive damage from Typhoon Haiyun/Yolanda.

IscarsahInternational Scientific Committee on the Analysis andRestoration of Structures of Architectural Heritage

5

INDEX

Message of the President of ISCARSAHStephen Kelley

Шуховская башня вМосквеŠuchov Tower in Moscow

News from Iscarsah MembersPierre-Yves Caillault, La restauration ducloitre de la cathe drale de ToulOu Un « ecosyste me » medievalretrouvéKhalid El Harrouni, Règlement parasismique des constructions en terreau Maroc (RPCT)

Scientific reportsRandolph Langenbach, Rubble StoneWalls and Reinforced Concrete Frames:Heritage Structures Reveal the HiddenTruth about Risk and Resilience duringthe Haiti EarthquakeAllen Lowry - James Monday,Streets of Jacmel, HaitiStefano Gizzi, El proyecto deconsolidación de la torre de Francescodi Giorgio Martini en Cagli (Italia)Daniel Ureña-Muñoz - Stanislav Pospisil,Comparison of calculated and measureddynamics characteristics of the Church ofSt. Peter and St. Paul, Prague (Czech Republic)

Iscarsah newsletter n. 5/2013

2

News from Iscarsah Members

International Scientific Committee on theAnalysis and Restoration of Structures ofArchitectural Heritage

website:http://iscarsah.icomos.org/

facebook:https://www.facebook.com/pages/IS-CARSAH/263710868630

linkedin:http://www.linkedin.com/groups/IS-CARSAH-Structures-Architectural-Her-itage-3930057

Newsletter n. 5December, 2013ISSN 2306-0182

Editor: María Margarita Segarra LagunesVia Emanuele Filiberto, 19000185 Roma (ITALY)

email: [email protected]

1

2

4

8

10

20

24

27

March 11, 2014

Mr. Vladimir Shukhov!

he International Scientific Committee on the Analysis and Restoration ofStructures of Architectural Heritage (ISCARSAH) was founded by ICOMOS in

1996 as a forum and network for engineers involved in the restoration and careof building heritage. The first meeting of the ISCARSAH took place at the Engi-neering University in Rome in March of 1997 our committee of more than 100members meets yearly in venues all over the world. Members of the ISCARSAHare composed of internationally renowned engineers, scientists, architects, spe-cialists, and educators with representation from Europe, Asia, Australia andNorth and South America.ISCARSAH is extremely distressed to learn of the threat to the Шуховскаябашня in Moscow. As you mention in your letter to President Putin and as wehave followed from the international media, the Communications and PressMinistry has recommended dismantling the Tower before it collapses.We are familiar with the constructivist architectural works of your great grand-father, Владимир ГригорьевичШухов, and realize that his contributionto the built environment is just one of his many achievements. His comparison toGustav Eiffel is apt due to his development of hyperboloid structures of whichMoscow’s 160 meter high Шуховская башня is the most famous example.Its construction date of 1922 is critically important - very little construction tookplace in the Soviet Union at this time due to the economic policies of War Com-munism. Construction focused only on power, industry, and housing during thisperiod and the Шуховская башня is a prescient example leading the wayfor Soviet avant-garde architecture that would flower in 1928.The Шуховская башня, an iconic symbol and landmark in the southern partof Moscow, suffers from a lack of appreciation and proper care as does manyother examples of 20th Century architectural heritage in the world. This tower isalso a “landmark” in many architectural and structure engineering schoolsthroughout the world. It inspires many architects and engineers to use such sys-tems in an innovative manner and to develop innovative structural solutionsthat changed the demands of the construction industry.It would be beneficial for Russian and World Heritage if the administrators un-derstand that the conservation and enhancement of the architectural heritageoffers a platform to observe the continued development of novel technologiesand has to be our commitment to maintain the social, economic and environ-mental traditions.The ISCARSAH stands ready to assist in any manner that you might deem benefi-cial to this critically important cause. Please feel free to add our names to yourletter to President Putin.

Best regards,

Prof. Stephen Kelley (USA), SE, AIA President - ISCARSAHProf. Dr. Gorun Arun (Turkey), Mimarlik Facultesi, Yildiz Technical UniversityVice President ISCARSAHProf. Dr. María Margarita Segarra Lagunes (Mexico-Italy), Dipartimento di Architettura, Universita degli Studi Roma Tre, Vice President ISCARSAHProf. Dr. Debra Laefer (USA), School of Architecture University College DublinSecretary General ISCARSAH

Шуховская башня вМосквеŠuchov Tower in Moscow

T

3Šuchov Tower in Moscow.

Iscarsah newsletter n. 5/2013News from Iscarsah Members

La restauration du cloitre de la cathedrale de ToulOu un « ecosysteme » medieval retrouvéPierre-Yves CaillaultArchitecte en Chef des Monuments Historiques

n matiere de « developpementdurable », les monuments anciens

sont bien souvent riches d’enseigne-ments. Ainsi, lors de la restaurationdu cloitre de la cathedrale de Toul,l’ecosysteme mis au point par lesconstructeurs du Moyen Age pour re-cueillir (et recycler) l’eau de pluievenant des toitures a ete mis au jour,restaure et remis en fonction. Au-delad’une restauration permettant deretrouver les dispositions anciennesdu monument, il s’agit ici de montrerla pertinence et la permanence desprincipes de la constructionmedievale dans le contexte de nospreoccupations actuelles concernantle respect de l’environnement.La cathedrale Saint Etienne, construiteentre le debut du XIIIeme siecle et lemilieu du XVIeme a un cloitre sur soncote sud bati entre 1346 et 1411. A lasuite des degats causes par la Sec-onde Guerre mondiale, d’importantstravaux de restauration ont ete menesmais il faudra attendre les annees1982-1991 pour voir le grand chantierde reconstitution du haut comble (nef,transept et chœur) et ce n’est qu’entre2009 et 2013 que furent restaurees lestoitures du cloitre (encore constitueesde toles), objet de notre recente inter-vention. A cette occasion, nous avonsmene des travaux d’assainissement etd’amelioration du recueil et de l’eva-cuation des eaux pluviales.Alors que notre projet consistait arestaurer et a prolonger l’usage desgargouilles medievales, nous avionsprevu d’enterrer des bacs en betonprefabrique relies entre eux au droitde chacune d’elles et d’evacuer leseaux de pluies ainsi recueillies dansle reseau urbain. Les necessairessondages archeologiques precedantcette operation, realises par l’INRAPsur les prescriptions du ServiceRegional de l’Archeologie revelerentdes fragments d’anciennes canalisa-tions mettant en relation le point

E

Plan de la cathedrale de Toul par Emile Boeswilwald - 2eme moitie du XIXeme siecle.

Iscarsah newsletter n. 5/2013 News from Iscarsah Members

Vue de l’intérieur de la citerne.

4

d’impact de l’eau s’ecoulant des gar-gouilles avec une construction en-terree, une citerne, situee au centredu cloitre. Explorant l’interieur decette citerne, nous avons decouvertune construction en tres bon etat deconservation, constituee d’unecoupole appareillee structuree parhuit arcs rayonnants qui se rejoignentsur un oculus au-dessus duquel etaitposee la margelle d’un puits. Au cen-tre de chacun des quartiers de vouteavait ete menage un exutoire enpierre, contemporain de l’ouvrage. Ildevenait evident que les exutoirescorrespondaient aux canalisations enpierre dont quelques fragmentsavaient ete reconnus par sondages.Les auteurs des sondagesarcheologiques ont pu apprecier lebon etat de conservation de la citerneet mettre en evidence la conceptiond’origine des [...] rigoles en pierreplates grossieres [...] destinees a recu-perer les eaux de pluie qui sedeversent des gargouilles. Le rapportde l’INRAP est complete par l’obser-vation suivante: «...ces rigoles sontaujourd’hui a l’etat d’abandon et nesauraient remplir leur fonction effi-cacement. Un large drain implanteposterieurement a l’est de la citerne, amanifestement pour fonction l’eva-cuation de l’eau qui viendrait la rem-plir. Cette structure marque l’abandonde la citerne et pourrait coincideravec l’obturation de la margelle... ».A partir de cette premiere reconnais-sance archeologique, nous etions con-vaincu de l’interet du dispositif mis aujour, tant sur le plan historique qued’un point de vue technique. En effet,le cloitre est implante en contrebasdes terrains environnants et l’evacua-tion des eaux de pluie dans le reseauurbain ne pouvait se faire de facongravitaire ; de plus, le raccordementau reseau existant imposait de tra-verser des structures anciennes pourrejoindre l’espace public. Rappelonspar ailleurs que les quantites d’eau aevacuer ne concernent pas unique-ment les toitures du cloitre maistoutes celles du flanc sud de lacathedrale.

Plan du cloitre.

En cours de travaux, vue du reseau d'assainissement medieval.

5


Le maitre d’ouvrage fut rapidementacquis a notre nouveau projet consis-tant a reconnai tre l’ensemble dureseau ancien, a le restaurer et a lecompleter afin de retrouver l’e quili-bre qu’avaient mis au point les con-cepteurs du Moyen A ge. Nousdecidions alors de mettre au jourl’ensemble du reseau enterre, ta chequi fut confie e a Cecile Travers,archeologue specialiste des jardinshistoriques. La fouille systematiqueentreprise sous sa direction a permisde reconnaitre un ouvrage en bienmeilleur etat que les sondages pre al-ables ne laissaient espe rer.En coordination avec les tailleurs depierre, les canalisations reconnuesont ete restaurees en conservation etles parties manquantes ont ete com-pletees par des elements en PVC afinde retablir la continuite du systeme.Dans l’ouvrage medieval, seules huitgargouilles etaient reliees a la« citerne » centrale (celles des quatreangles et du milieu de chaque cote ducloitre). Nous avons partiellementconserve notre projet initial par lamise en œuvre de bacs enterres audroit de chaque gargouille. Ces bacsrelies entre eux deversent l’eaurecoltee dans les anciennes canalisa-tions restaurees vers la citerne ; ceuxqui ne sont pas directement situes au-devant d’un canal en pierre sedeversent lateralement et alimententles canaux situes de part et d’autre.

Interieur de la citerne, detail d'un exutoire.

Vue du cloitre apres la remise en service du reseau d'assainissement.

Toul, Cathédrale Saint-Etienne. Citerne du cloitre. Plan et coupe (P. Y. Caillault, ACMH, juillet 2013).

6


Ainsi, le systeme medieval a eteameliore permettant desormais derecolter l’eau issue de toutes les gar-gouilles et les bacs enterres reliesdeux a deux previennent l’eventuellesurcharge de l’un d’entre eux.Le fond de la « citerne » analyseapres en avoir vide le remblai qui s’ytrouvait (operation archeologique ef-fectuee par C. Travers) s’est reveleconstitue d’un empierrement et nond’un dallage comme on pouvaits’y attendre. Apres de fortes pluies, la « citerne »se remplit avec l’eau canalisee depuisles gargouilles puis, son niveaus’abaisse progressivement et laisse enpermanence une quantite d’eau suff-isante pour y puiser de quoi arroserles vegetaux du cloitre.Plutot qu’une citerne, il s’agit d’un «puits perdu » dans lequel on peut atout instant puiser de l’eau...Notre chantier aura permis de donnerune seconde vie a cet ingenieux dis-positif et peut-etre de mieux tirer leslecons que nous donnent l’analyse etla comprehension des edificesdu passe.

Vue du cloitre apres les travaux (angle nord/est).

7

Vue du cloitre apres les travaux (angle sud/ouest).


I. Introduction

La construction en terre a héritéd’une tradition vernaculaire, destechniques et des solutions judi-cieuses qui ont évolué avec l’espritet l’objectif, de mieux valoriser lespropriétés des matériaux locaux etplus particulièrement le matériauterre de construction. Elle repré-sente un patrimoine socioculturelde plusieurs générations, et le té-moin authentique de notre archi-tecture traditionnelle.Durant les dernières décennies, laprotection sismique des construc-tions en terre a été au centre d’in-térêt de décideurs, professionnels,chercheurs, utilisateurs et cons-tructeurs. Tous ces acteurs sontpresque unanimes sur le fait que laconstruction en terre n’est pasaussi vulnérable qu’on le croyait,vis-à-vis des secousses sismiquescar plusieurs constructions en terreà travers le monde, notammentnos remparts imposants, nos médi-nas impériales et nos Kasbah etKsour en pisé, en adobe et en terrecuite, ont survécu les événementshistoriques de séismes destructeurs.Cette performance sismique est lerésultat de l’utilisation des règles debonne pratique concernant le choixde matériau terre, d’une conceptionsimple et régulière, des conditionsde mise en œuvre de qualité, dessystèmes de protection contre leseffets de l’eau et finalement les dis-positions constructives concernantparticulièrement les fondations etsoubassements, les ouverturesdans les murs, les renforts d’at-taches et de contreventement hori-zontal (diaphragmes) et vertical(renforts et structures en bois in-corporées).Il est donc de notre devoir de val-oriser d’une manière rationnelle lesperformances de la construction enterre pour qu’elle demeure entreautres, la solution économique etécologique retenue de l’habitat enmilieu rural. Il faut noter que plusieurs pays dis-posent de documents normatifs etguides destinés à la protection sis-mique des constructions en terre.Le Règlement Parasismique des

Règlement parasismique des constructions enterre au Maroc (RPCT)Khalid El HarrouniEcole Nationale d’Architecture, Rabat Instituts, Morocco

Constructions en Terre vient d’êtreadopté au Maroc. Ce qui permet dedoter notre patrimoine de construc-tions en terre de normes et derecommandations techniques pourpromouvoir ce secteur de construc-tion en milieu rural et même en mi-lieu urbain au même titre que lesconstructions en matériaux conven-tionnels. Plusieurs travaux au niveau nationalet international ont été réalisés envue d’élaborer les spécificationstechniques des constructions enterre : pisé, adobe, bauge, maçon-nerie de pierres et briques de terrecompressées. La mise en application du Règle-ment Parasismique des Construc-tions en Terre vise les aspectsimportants suivants :• Le développement d’une architec-ture écologique en harmonie avecl’héritage vernaculaire, et l’exploita-tion des expériences riches et sécu-

laires de cet héritage ;• La prévention de l’extension del’informalité, et éviter son expansionau milieu rural ;• La préservation de la diversité ar-chitecturale du pays ;• La participation au ralentissementde l’inévitable exode rural ;• La réalisation d’économie d’én-ergie en freinant la généralisationdu recours aux matériaux à haut in-trants énergétiques (acier, cimentset autres) et en réduisant les fraisde transport des matériaux de con-struction par l’utilisation et la valori-sation des matériaux locaux. Les conditions socio économiques,techniques et technologiques ac-tuelles, à court et moyens termes dumilieu rural ne permettent pasd’avoir recours d’une manière systé-matique à l’architecte et à l’ingé-nieur. Pour atteindre les objectifscités ci-dessus, ce règlement estconçu en deux volets pour être plusflexible et faciliter sa mise en appli-cation.• Premier volet : Guide Parasis-mique d’Auto–Construction en TerreCe règlement concerne les construc-tions en terre qui sont réaliséessans faire appel aux études archi-tecturales et techniques. Ce guideest un recueil de prescription derègles de bonne pratique et desavoir faire en matière de protectionsismique des constructions en terre.Ce guide est plus simple à mettreen œuvre et convient parfaitement

Ksar Jranat, Erfoud (Réhabilitation par Al Omrane).

Séisme Al Hoceima (Nord du Maroc) en2004, milieu rural.

8


9

18%g à 20%g). 5) La hauteur maximale des mursporteurs en terre est 4m pour uneconstruction à un seul niveau et6.5m pour une construction à deuxniveaux.Les zones d’accélération maximalesont données par la carte de zonessismique au Maroc.

Référence: Royaume du Maroc, « RèglementParasismique des Constructions enTerre (RPCT2011) », Bulletin Offi-ciel n. 6206, 21 Novembre 2013.

pour réglementer l’auto construc-tion en terre.• Deuxième volet: Règlement Para-sismiques des Constructions enTerre (RPCT)Ce règlement est destiné aux archi-tectes, ingénieurs et technicienschargés de la conception et le di-mensionnement des constructionsen terre. Il concerne les perform-ances requises des structures decontreventement des constructionsen terre vis-à-vis des séismes.

II. Domaine d’application durèglement RPCT

Le concepteur doit être en mesurede trouver des solutions adaptées etoptimisées au contexte du projet deréalisation d’une construction enterre pour atteindre les perform-ances sismiques requises. Les prin-cipes de base de la justificationparasismique des constructions enterre sont similaires à ceux de lamaçonnerie non armée. Le principedes Etats Limites est adopté pourune mise en conformité avec celuide la conception et le dimension-nement des constructions en maté-

riaux conventionnels.Le Règlement Parasismique desConstructions en Terre s’applique :1) Aux constructions en terre sou-mises à l’obligation de recours à unarchitecte et à un bureau d’étudespour l’obtention du permis de con-struire. Les éléments porteurs prin-cipaux sont des murs en adobe,pisé, bauge ou moellons de pierresà mortier de terre. Le matériau terrepeut être stabilisé ou non. 2) Les Constructions sont limitées àun niveau en zones d’accélérationmaximale (de 18%g à 20%g) et àdeux niveaux en zones d’accéléra-tion maximale (de 10%g à 16%g).3) Les constructions en terre d’im-portance vitale de type : hôpitaux,cliniques, établissement de protec-tion civile, les postes de police, lesbâtiments administratifs de centrede décision en cas de séisme, sontlimités à un seul niveau dans toutesles zones.4) Les constructions en terre des-tinées au grand public de type :écoles, universités, bibliothèques,musées, grands lieux de culte,centres commerciaux, etc.…, sontlimitées à un seul niveau en zonesd’accélérations maximales (de

Zones sismiques au Maroc.


Rubble Stone Walls and Reinforced Concrete Frames:Heritage Structures Reveal the Hidden Truth about Risk and Resilience during the Haiti EarthquakeRandolph LangenbachBuilding Conservator (www.conservationtech.com)

ntroductionThis article is about the effects of the 2010 earthquake in Haiti, a subject I have long wished to share with my

ISCARSAH colleagues. With it, I also wish to honor the contributions of the other members of the World Monu-ments Fund/ICOMOS mission to Haiti undertaken after the earthquake to help in the effort to preserve the re-markable collection of 19th and early 20th century houses of traditional construction, almost all of which, althoughdamaged to varying degrees, survived the earthquake. These houses, which had become known by the Englishterm, “Gingerbread Houses” (not “pan-espice” as it would be in French), had previously been listed by the WorldMonuments Fund on their ‘Watch List’ of structures at risk.

Three of the members of the WMF mission team: Steve Kelley, Patrick Sparks and I, are members of ICOMOS-IS-CARSAH. The two other members included architect Martin Hammer, noted for his international disaster recoverywork in Pakistan and particularly for his work with straw-bale construction, and a builder, Kevin Rowell, noted forhis work using traditional materials and technologies. All of the team members generously agreed to volunteer forthis mission, with only a small stipend for the preparation of the mission report which became a book co-authoredby all members of the team and published by the World Monuments Fund. This book can be downloaded in Eng-lish, French or Spanish for free from the World Monuments Fund Website that can be accessed from this link:www.haiti-patrimoine.org

The Gingerbread Houses of Port-au-PrinceThis article describes the findings of that mission, as well as the use of the Pictometry aerial survey data that Pic-tometry International generously donated to ICOMOS for the mission. For the mission, this aerial survey was ofimmeasurable importance because the oblique views allowed us, together with the Haitian homeowners in meet-

ings at the co-sponsoring organiza-tion FOKAL, to identify the locationof their Gingerbread Houses betterthan straight-down aerial and satel-lite views, by revealing their archi-tecture from the side. Theirsignificance became increasinglyclear when I began to use them tosurvey the earthquake damageacross the entire damage district.

Using Adobe Photoshop to merge thehundreds of Pictometry photographstaken from the belly of an aircraftinto large maps where the side viewsof every building were visible taughtme the power of this data to providean impartial and comprehensive viewof the building construction and theextent and nature of the damageover large areas of the damage dis-trict – areas when seen from theground would be only in the best ofcircumstances a small portion of thescene. Even the most impartial ob-

server on the ground would tend to migrate towards areas where the damage was most pronounced, which then af-fects the objectivity of the assessments, while the comprehensive aerial views can help to avoid this problem.

When our team arrived in Port-au-Prince in April of 2010, four months after the earthquake, we had seen the imageryin the news and early reconnaissance reports. We were first taken to the Oloffson Hotel where we found ourselves in a120 year old three story unreinforced brick masonry building in excellent condition that had never closed after the earth-quake. The only marks on it left by the earthquake were cracks so small that to show them in slide shows later, arrowsand circles were needed to point them out, even though a new 9 story hotel lay completely pancaked behind it. In fact,the largest crack found in the walls of this building turned out to be from a rusty bolt embedded in the brick wall!

I

Figure 1. Like a scene from Dante’s Inferno, central Port-au-Prince, 4 months afterthe earthquake.

10

Iscarsah newsletter n. 5/2013 Scientific reports

11

We then began to survey the historic late nineteenth century houses, almost all of which had suffered through ahalf-century of neglect, some of which were constructed of rubble stone masonry laid in earth mortar, confinedonly by piers of fired brick in deteriorated lime mortar. Almost all of these houses - even those of rubble stone -were still standing. Some were heavily damaged, but almost all were still standing after an earthquake which wasby then reported to have killed as many as a quarter-of-a-million people!

To put this in perspective, a quarter-of-a-million fatalities places this earthquake side-by-side with the Tangshanearthquake of 1976, which caused more fatalities than any other in the 20th century – by an order of magnitude,and more than all but one in all recorded history. With the poverty and bad construction known to exist in Haitithis seemed plausible, especially since it was initially reported by the USGS that this earthquake was calibratedin their initial ‘shakemaps’ as a Modified Mercalli Intensity (MMI) of IX in Port-au-Prince – a statistic that wouldlater change, as is reported below.1

Figure 2. Left: April 2010 Exhibition at FOKAL in Haiti of murals if the Gingerbread District made from Pictometry images.Right: View showing the Gingerbread houses picked out of the aerial images by their distinctive architecture. The NationalPalace, which collapsed, is visible in the upper left.

Figure 3. The unreinforced brick masonry Hotel Oloffson, Port-au-Prince after the earthquake.

Iscarsah newsletter n. 5/2013Scientific reports

Determining earthquake intensity in the absence of instrumentationAt the time of the earthquake, it was the widespread collapse of the more formally constructed buildings in Port-au-Prince that undoubtedly fed the perception that a classification of the intensity as an MMI-IX and even an MMI-X (asis still reported in Wikipedia) was correct – not just in the epicentral area near Léogâne, but also extending throughPort-au-Prince, 34 km to the east, and even including Pétionville, an additional 8 km further east. At that timeit was thought that the fault rupture extended under Port-au-Prince, but this was later determined by USGS tobe incorrect.

Two buildings that may have influenced the setting of a high MMI were the pancake collapses of the five star HotelMontana, and the former five star hotel used by the UN to house its staff in Haiti (Figures 4 & 5). The Hotel Mon-tana had been heavily used by visiting US governmental officials. These two collapses alone killed the head of theUN mission together with much of its staff, as well as a number of US and European dignitaries. Knowledge of theseevents spread fast, including to the US Geological Survey (USGS) which within hours of the earthquake began pub-lishing their famous shakemaps that, in addition to instrument data where it existed, included subjective databased on analysis of the initial news reports and over the phone interviews.

Unfortunately, there were at that time no seismographs in or near Haiti, and so the use of the Modified MercalliScale criteria to classify the damage became particularly important as a measure of the ground shaking in thisearthquake. Since it must have seemed inconceivable to USGS that these hotels would be less structurally soundthan the shanty-town houses that surrounded Port-au-Prince by the hundreds of thousands, the estimation of ahigh death toll seemed reasonable.

But then, how does one reconcile the still-standing houses with walls of rubble stone, or the practically undamagedOloffson Hotel with an MMI-IX or X? The reaction of many when told of this is to say that the sites may have ex-perienced less shaking than those areas that were devastated – a not unreasonable response. In fact, a detailedgeological study was conducted by a team from the University of Texas, Austin shows the soil strata under the down-Town area to be more responsive to seismic vibrations. However, just up the slope behind the Oloffson a modernnine-story reinforced concrete hotel building pancaked. The chances of a difference in seismic shaking in such closeproximity being the reason for such a difference in building performance seems very remote, although the differ-ence in height and stiffness of the buildings may have contributed to the difference in performance. Similarly,throughout the Gingerbread district, which is to the east of the area identified by UT as being the most vulnerableto seismic resonance, the intermingling of the surviving Gingerbread houses with many buildings of more recentconstruction – usually of RC or concrete block with RC floors, many of which collapsed – made it unconvincing toexplain differences in the extent of damages and collapse by underlying soil differences alone.

The Gingerbread houses were of three main construction types: (1) brick and rubble stone masonry, (2) bracedwood frame with brick or rubble stone infill, known there by its French name colombage, and (3) 100% bracedwood frame of traditional timber framing and/or American balloon framing with wood board cladding. One im-portant feature of those of masonry is that most, if not all, had an iron band imbedded in the walls at the floor androof levels – which did help to restrain the walls from spreading. Such probably exists in the Hotel Oloffson, butbecause the building remained intact, and surface hardware, if it exists, is hidden by the wood verandas. Neitherthis, nor any existence of rubble masonry in its walls could be confirmed, but the existence of a tie and the ab-sence of rubble stonework are both likely, considering the building’s good performance.

In almost all cases, the timber framing elements were compromised by termite damage and/or fungal decay –which was in a few cases very extensive. Despite the almost universal lack of maintenance and commonly founddecay, it was rare to find even a partial collapse at any of these houses, regardless of construction type. In thebuildings with rubble stone, in quite a few instances, the rubble stone sections of the walls showed different gra-dations of damage from the shedding of exterior stucco to the partial or total falling out of a stone panel – leav-ing the building still standing on the brick piers which surrounded the rubble sections of the walls.

This damage survey of the Gingerbread houses turns out to be particularly significant when one considers thatGiuseppe Mercalli largely used masonry buildings to calibrate the scale above the level of VI when, in the late 19th

12

Figure 4. Five star collapses in Petionville: left: Hotel Montana before, and centerafter the earthquake (Google images).

Figure 5. UN Headquarters after theearthquake (Google images).


century, he developed the scale that bears his name. An earthquake classified as a IX on the MMI scale would beexpected to cause “Damage to masonry buildings… from collapse to serious damage” whereas what was found inthe WMF survey seems closer to the description for an MMI-IV: “…damage to some poorly built unreinforced ma-sonry buildings [and] some cracks even in better built masonry buildings if not reinforced.” Thus the OloffsonHotel would qualify as a “better built masonry buildings,” while the brick and rubble stone mixed constructionhouses, because of the existence of the rubble stone in clay mortar, inarguably can serve as examples of “poorly builtmasonry buildings.” So, using these examples, it would seem that this earthquake is more accurately classified asan MMI-VII, rather than an MMI-IX or X, as has been often cited.

A ‘Desktop’ Damage AssessmentIn the months following the WMF mission, Pictometry generously agreed to extend my access after their invita-tion to give an address at their annual conference in Orlando, Florida. With this opportunity and the Orlando ad-dress in mind, I began to survey the entire damage district in what I call a ‘desktop’ damage assessment. The WMFmission had already made us all aware of what seemed to be a counter-intuitive discrepancy between the perform-ance of the more than century-old Gingerbread houses of brick, rubble stone, and timber construction that we hadcome to survey and the rest of the building stock in which the reported quarter-of-a-million people died. However,earthquakes often show anomalies where even seemingly identical buildings constructed next to each other at the

same time can show radically dif-ferent damages, with one collapsedand the other showing minimaldamage. Although a century ormore old, these were constructedas upper class houses in what isnow largely a world of urbanpoverty in Port-au-Prince.

The first step in my desktop surveywas to take the results of a WorldBank sponsored post-earthquakedesktop survey and compare it withthe visual information provided bythe four directions of oblique viewsin the Pictometry data. The WorldBank had asked members of EERIand the earthquake engineeringcommunity to access a special layerin Google Earth which had high-resolution straight-down imageryfrom a flown survey rather than

satellite imagery, and from this imagery mark those buildings showing evidence of partial or total collapse.2 Sincestraight down photography shows the roofs rather than the sides of buildings, this required judgment based onthe debris field around buildings and the distortion of the roofs.

This allowed me to look first at those areas with evidence of concentrated areas of damage – where the red marksfrom that survey were densely packed. Following that, I looked at increasingly large areas – mainly over the in-formal settlements known as “bidonvilles” or “tin-can-cities” – where the largest concentrations of the populationare located. The results of this were revealing. In summary, despite the fact that there were significant areas of

13

Figure 6. Brick and empanelled round-rock rubble stone construction, as is typically found in many of the Port-au-Prince “Gin-gerbread” Houses from the late 19th century, showing different levels of damage from onset, to collapse of the rubble panels.Center: The 2 ½ story Villa Castel Fleuri Mansion was of rubble stone between brick piers and window surrounds, and onlythe staircase projection collapsed. The onset of inelastic deformation of the rubble stone panels is visible where the surfacestucco has come off. Right: The Dufort House still standing on its brick piers after the collapse of the rubble stone panels.This house is now being restored by FOKAL. Many reinforced concrete buildings nearby collapsed.

Figure 7. Left: Pancake collapse of a reinforced concrete building that was lo-cated in the Gingerbread District of Port-au-Prince. Right: As a remarkable exam-ple of the inherent strength and resilience of a well-constructed reinforcedconcrete building, this one in Rikuzentakata, Japan was swept onto its side andcarried upstream by the March 10, 2011 earthquake and tsunami without beingcrushed or collapsed (AFP/Getty).


concentrations of building collapses, area after area in the heart of the damage district were revealed as havingremarkably little visible evidence of even partial collapses.

In fact, a good number of the buildings in the bidonvilles identified in the World Bank survey as collapsed turnedout to be misidentified only because they were constructed with roofs that were uneven and discolored – the kindof thing impossible to be able to see from straight-down images alone. Interestingly, the World Bank surveyproved to be far more accurate for the downtown commercial buildings than for the bidonvilles because there thecollapses were more easily discerned.

There were areas – as confirmedby the news and reconnaissancephotography on the ground – whichdid show extensive or completedevastation, and for these, the Pic-tometry images also have proved tobe a remarkable diagnostic re-source.3 Unlike with Google Maps orGoogle Earth, working directly withthe Pictometry website allowed meto download the actual original pho-tographic images as jpgs. This thenenabled me to be able to importthem into Photoshop, and align twosequentially shot images so that thearea of overlap could be excised. Thisthen allowed the export of the im-ages as stereo pairs.

One may ask why this would providescientific data beyond the possibleentertainment value of looking atruins in 3D, but it proved to be in-valuable. It showed that every sur-veyed area in the bidonvillesettlements where the damage waswidespread or total to be located ona steep slope, and those areaswhere there were few or no col-lapses, the slopes were less. Look-ing at these intact areas morecarefully, the damage that one couldsee in the areas where the damagevisible from the air consisted only ofisolated wall collapses (often of wallsthat were under construction at thetime of the earthquake and thuswithout roof or top plates), while inthe steep areas, total collapsescould often be seen where buildingshad cascaded down the hillside, withone perhaps falling on one below, ora foundation being undermined in amini-landslide. If one considers thatpoor people will probably not botherto build retaining walls, or if theyhave, perhaps they have done sowithout the engineering know-howor access to the proper materials toassure that they will resist earth-quake vibrations, this difference be-

tween the sites is logical. In fact, many of the retaining walls in Haiti, where they did exist, were of dry laid roundriver stones between widely spaced concrete columns.

When I embarked on this desktop survey, I did not have a particular idea of what I would find, as my access tosites during the short visit to Haiti for the Gingerbread mission was focused on that one particular area. I had theopportunity to make only a single trip to the city center – which was forced by circumstance to be particularly short

Figure 8. View of 4 Carrefour Feuilles area bidonville, close to the city center, Port-au-Prince (© Pictometry).

Figure 9. View of 4 Carrefour Feuilles area bidonville, close to the city center, Port-au-Prince showing the unsophisticated rough construction of informal settlementdwellings, with incomplete frames, round-rock rubble stone retaining walls, andunreinforced concrete block construction – that nevertheless did not collapse(Source: Carlos Barria-Reuters).

14


when we helped a mother find medical help to save the life of her baby burned badly from a campsite fire. In fact,I expected to find in the desktop survey what the news reports had described – almost total devastation withinthe informal settlements. The vast encampments of displaced people seemed to reinforce this impression, butmany of these people, I later learned, were displaced from buildings that were still sound, but which they wereafraid to return to.4

As I moved systematically in Pictometry over the landscape of Port-au-Prince, scene after scene came into viewshowing intact buildings, and I began to realize that this was potentially a significant finding. This was especiallythe case when a similar survey over the city center revealed the kind of almost total devastation that one expectedto find throughout the bidonvilles, but which turned out to be concentrated only on particularly steep sites.

There were three areas that were particularly representative of these findings: informal settlements (1) on thehillside above Pétionville a short distance from where the Hotel Montana and the UN residential hotel had stood,(2) on the hillside nearest the city center, the National Palace and the Gingerbread district, and (3) the area knownas Cite Eternal located on an alluvial fan closer to the epicenter than almost all of the rest of Port-au-Prince. In thecase of (1) no collapses could be found, and the damage was thus limited to repairable damage to the dwellings.Colleagues of mine, architects Christopher Andrews and Seth Wachtel of the San Francisco Bay Area, visited thissettlement subsequent to the earthquake and confirmed the finding that little damage and displacement of theoccupants occurred at this site. At (2), a hillside area showed pockets of heavy damage, but the vast preponder-

Figure 10. City Eternal an informal settlement on an alluvial fan next to downtown Port-au-Prince, with insets (left) showing2, 3, and 4 story buildings still standing without visible damage, and only evidence of one collapsed building in the view, and(right) evidence of the collapse of RC frame structures, including an open air market structure among other buildings.


15

ance of the tightly packed cluster of homes that spread over the hills showed little damage visible from the airwithin the high resolution of the Pictometry images (Figures 8 & 9).

Number (3), known as Cite Eternal, was even more remarkable for a number of reasons in addition to beingcloser to the epicenter (Figure 10). One would normally expect that an alluvial soil site like this would be partic-ularly vulnerable – especially for taller buildings, but three and four story structures appeared in the imagery tonot show visible damage, although there may be damage invisible from the air. Also interesting was to find thatseveral buildings around a large central market structure that were of more formal construction of reinforcedconcrete frame with infill walls collapsed. The rest of the settlement consisted of construction that was morecommon to informal buildings, which could only be loosely described as confined masonry or simply concreteblock construction.

This particular observation was consistent with the larger issue that defines what has happened to the building stockin this earthquake. If the buildings in the informal settlements not on steep sites proved to be more earthquake-resistant than expected, one must then ask the question why. As has been documented by the University ofTexas – Austin geologists, the soil strata differences can account for some of the excess of damage in the citycenter, but it is not enough to simply turn to the geological reports to explain all of the difference that one finds.If so, then what about Cite Eternal which, at best, is on similar, but more recent, alluvial strata to that under thedowntown area where the concentration of the collapses of formal multi-story buildings of recent origin occurred– including many government buildings.

Does this defy the improbability that poor people without training on land they do not own would use higher qual-ity materials, better engineering, and better construction quality control than that found in the formal, contractor-built, and even sometimes engineered structures downtown and in Pétionville? The answer to this question is no.The quality of the design, construction and even the materials used in the informal settlements was in fact quitepoor as one would expect – they just did not often collapse (Figure 9).

The clue that I believe helps to explain this is the performance of the brick and rubble stone Gingerbread houses.This provides some evidence that the earthquake shaking in most of Port-au-Prince was no greater than an MMI-VII. Only an understanding of this explains the survival of the rubble stone houses and the informal settlementhouses – the earthquake, although big, was simply not as strong as had been thought. In fact, the USGS did reportthat the earthquake was only an MMI-VII in Port-au-Prince in their last and most accurate shakemap published onMarch 4, 2010 after all of their scientific data had been reported and analyzed and this was also the same as wasreported by the UN/European Commission. If this is all true, then the most challenging question is why did theformal construction – most of which was of reinforced concrete – fail so catastrophically?

It would be easy here to list all of the reasons why a reinforced concrete moment frame with infill building constructedin Haiti would have defects, such that could cause a collapse in an earthquake, but my ISCARSAH colleagues wouldalready know these reasons. In fact, one colleague from Ove Arup Engineers in Haiti for OXFAM prepared a list ofreasons which he shared with me of what he observed were faults he frequently found in the construction of RC build-ings. The list came to 20 items, any one of which could have caused the onset of a collapse.5 However, what is in-teresting to explore here in relationship to the Pictometry data is why the slum housing – much of which was madeof concrete and which, as I have mentioned above, even of lower construction quality than that of the downtownRC frame buildings – did better.

At this point in the analysis two facts have been determined: (1) It appears that a reasonable calibration of theshaking using the criteria set by the Modified Mercalli Scale that shows that the earthquake over much of Port-au-Prince, including the city center area, was in the range of an MMI-VII rather than higher. (2) Except for the steepsloped areas, the informal housing of a mixture of concrete block and partial concrete frame and slab elementswith site-mixed concrete, salvaged rebar and other materials constructed with little or no training, even if mani-festing damage, almost entirely remained standing.

Thus, what still needs to be determined is why a greater share of these poorly made houses – many of whichwere of more than one story – survived than of the downtown buildings. The conclusion that I have come to isthat, no matter how rough the construction was in the bidonvilles, the houses were primarily constructed withsolid walls, and the reinforced concrete framing elements did not constitute the primary lateral-resisting struc-tural system.

In recent years, ‘confined masonry,’ in which infill walls are constructed before the reinforced concrete frames,has increasingly been found to be quite resilient. The problem with even applying such terms-of-art in thebidonville areas is that many of the houses had incomplete frames, misplaced rebars, large rock pockets, andother faults, but all needed walls to serve as buildings – and for poor people room sizes are small, and thus alevel of redundancy is inevitable, as well as the fact that walls go to the ground without an open ground levelstory (Figures 9 & 10). Because this earthquake was an MMI-VII rather than a IX masonry buildings, by defini-tion, of poor construction are expected to survive with significant damage – so their survival is to be expected,as it is consistent with the survival with damage of the rubble stone buildings.

16


17

That then is what is significant about the findings of this Pictometry study – the multi-story RC moment framebuildings with infill masonry that collapsed did so at a level of shaking that did not collapse 19th century buildingsconstructed of brick and rubble stone, the only reinforcing in which was an iron tie at the second floor level. TheseRC collapses happened over a wide enough area to buildings of varying height with enough difference to make itdifficult to attribute this phenomenon to building-ground resonance alone, as, for example, was a very importantphenomenon in the 1985 Mexico City Earthquake.

After arriving at these findings from the Pictometry desktop-survey, I have found that two scholars on the EERIreconnaissance team, Anna Lang and Justin Marshall, came to similar conclusions based on their inspection ofbuildings on the ground in the bidonvilles, as well as in the city center.6 In their paper, they agree that Haitian RCconstruction is generally so haphazard that even the use of the term “confined masonry” gives credit for confine-ment that is incomplete – so they used the terms “column-first” and “wall-first” to distinguish these two types bythe order in which the walls and framing elements were constructed. They reported that they observed that “In-filled frame systems [‘column-first’] performed poorly and account for the majority of structural collapses[whereas] buildings assembled in a manner similar to confined masonry [‘wall-first’], however, performed well andexperienced little damage.” They found this to be the case even though they found that the construction of the‘wall-first’ buildings were usually seriously flawed and deficient, which they describe in detail.

How can one fix this in the future? This is a subject for another article, but one place to begin is to explore arecommendation that all construction – except that meeting certain engineering oversight and peer review, withon-site supervision and quality control – be of construction which does not in any way depend on the beam/col-umn intersections of frames for lateral resistance. Such can be of confined masonry, as is already popular in manydeveloping countries, ideally with published and widely circulated guidelines. Consistent with Lang and Marshall’sobservations, and also with the experiences in India where the government has included “Rules of Thumb” andsimple to use guidelines for non-engineered buildings which serve in lieu of formal codes, a requirement that non-engineered RC construction be ‘wall-first” would be a manageable first step towards improved life-safety condi-tions for such construction. For more formal and taller buildings, shearwalls, or the ‘Armature Crosswalls’ I haveproposed for a more economical alternative, are more dependable than moment frames alone.7 Exploring how toimplement such provisions in Haiti and other places similarly at risk, both for existing buildings and for future newconstruction, is an important subject to explore further than is possible in this article.

Casualties under PancakesAfter undertaking this study, one is forced to ask: “Where did the oft-reported quarter-of-a-million people die?”The corollary to this question is: “Where did this large casualty estimate come from?” Early in this research, I cameacross a report that may have served as an early stimulus for such a large figure. It published by RMS (Risk Man-agement Solutions) Corp only 10 days after the earthquake. This report predicted that the casualties could be ashigh as 250,000 people8. This conclusion was based on a USGS shakemap published four days after the earthquakethat showed the fault rupture extending under central Port-au-Prince, and an estimated intensity of MMI-IX. Inthe weeks following the earthquake, the Red Cross reported casualties in the range of 40,000 to 50,000, but themuch larger number has seemed to stick, being consistently cited within fifty thousand either way for the past fouryears. This has been particularly interesting since the data to back up such high numbers was so weak, and be-cause Haiti lacked census data to be able to establish the pre-earthquake population of the area with any certaintyand getting an accurate count in the chaos of the post-earthquake environment was impossible.

It is interesting also to see why RMS did come up with this casualty estimate of 250,000 fatalities. On page 7 ofthe report, it says:

The building vulnerability was assumed to map on average to unreinforced masonry construction, which is ex-tremely susceptible to collapses and heavy enough to cause significant casualties to occupants. This is consistentwith the prevalent construction type in the urban regions of Haiti (i.e., blocks/concrete), but actual constructionpractices vary and include reinforced concrete, reinforced masonry, and unreinforced self-constructed buildings.

After I found this RMS report, I contacted the author of the report, Patricia Grossi, and asked her: “If at the timeyou wrote the report, the USGS shakemap had been the one later published on March 4, which reported an MMIVII for Port-au-Prince, would your casualty estimate been different? Her answer was “absolutely – it would havebeen much lower.” Thus, perhaps an answer to the question of where the quarter-of-a-million people died, mayonly be that countless numbers of people did die, but not a quarter-of-a-million. The purpose of my research hasnot been to call into question the body count – and in my experience even the 46,000 to 85,000 people later es-timated by anthropologist Timothy Schwartz in a report for USAID that was found and published by the Associ-ated Press on June 2, 2011 is still a vast number of casualties, beyond the scope of wholly accurate counting andof huge impact on the survivors. It is in scale with that experienced in Pakistan in the 2005 Kashmir earthquakeand in Iran in the 2003 Bam earthquake, and exceeds the official estimates of even the two catastrophic earth-quakes in Turkey in 1999 combined.

My purpose was to try to isolate what can be learned by the Haitian tragedy that may constructively change ourthinking about how to influence building construction and maintenance in areas of earthquake risk – by accept-


ing the fact that bad construction of buildings is inevitable. After the earthquake there have been concerted effortsto improve the education of Haitian engineers and builders to raise the standards of reinforced concrete construc-tion, but it is equally important to approach the problem of building construction from a philosophical standpoint– that is to accept the fact that a certain percentage of buildings will be substandard, and thus try to modify thecommon structural systems in use today such that substandard does not inevitably mean they be so extremelydangerous as they proved to be in Haiti. The difference is what has been demonstrated by the still standing prim-itive houses in the bidonvilles and the pancaked downtown commercial and government buildings. It is not a dif-ference in quality of construction, but a basic difference in typology.

There is a simple reason why RC frames can be so vulnerable if mistakes are made. Design level earthquakes areexpected to cause structural damage, even to well-constructed buildings that meet modern codes. With an RCframe structure – the beam/column connections are thus expected to begin to break. Under such circumstances,preventing the building from collapsing, while at the same time allowing its structural frame to yield - that is anengineer’s art of the highest order - way beyond the knowledge and capacity of the usual contractors responsible forbuilding these structures. Thus what is needed particularly in developing countries with limited training, enforcementand inspection is the use of construction typologies that are less dependent on good design, and constructionquality, than is standard RC infill ‘column-first’ frame construction.

ConclusionA report on the Calabria earthquakes of 1905 and 1908 by Italian engineers in the 1932 treatise by John RipleyFreeman described the damage to reinforced concrete dwellings in Melicucca in 19059. Exactly what kind of RC

structural system is the subject ofthe description is not known, butthe quotes are interesting never-theless in light of the vast differ-ences found in the RC buildings inthe Haiti earthquake. It says the“reinforced concrete… dwellings…were nearly all tumbled down inspite of the fact that… the shockswere less violent than elsewhere…because of the poor quality of ma-terial used, and lack of proper jointsor connections between thevariousmembers…” In this description theysaid these were houses whosebuilders…classed… as “reinforcedconcrete structures [but] the sub-committee reported that they hadno right to this classification”.

In the next paragraph, they de-scribed “four structures of rein-forced concrete in Messina (wherethe shaking was much greater)which remained wholly unharmed…examples of the capabilities of thismaterial when properly used.”These quotes indicate that over acentury ago, near the beginning ofthe modern invention and use ofreinforced concrete, it was alreadybeing discovered that variations inconstruction quality resulted in thedifference between perfect per-formance and catastrophe. It isalso interesting to see that profes-sional expectations of its potentialfor good performance should meanthat the use of the term “rein-forced concrete” should not be al-lowed. Today, a century later, thesame spread from superlative toabysmal performance in earth-quakes is still a characteristic ofthe system.

Figure 11. National Palace in Port-au-Prince after the earthquake and partial demolition, revealing the reinforced concrete frame infilled with rubble stone (©Pictometry).

Figure 12. Detail view showing the reinforced concrete frame with round rock rub-ble stone infill of the 1916 structure exposed during the demolition of the ruins ofthe National Palace.

18


In Haiti, the two iconic symbols of the destruction wrought by this earthquake were the National Palace (Figure 11,12) and the National Cathedral. Both were reinforced concrete. The cause of the collapse of these twostructures, as well as many other 100+ year old churches, was the corrosion of the rebars after a century of expo-sure to moisture in the tropical environment. Yet only a few blocks away from both, and resting on the very soilidentified as subject to the highest shaking, is another structure that few have seen and which has rarely been inthe news, but which stands as a remarkable monument to resilience when almost every building around it collapsed– the Saint Louis de Gonzague Chapel (Figure 13). It was as high and about half the length of the cathedral, andabout 20 years older – but little damage was visible on the exterior. The structure was of brick masonry with an ironor steel frame. Not only has it not rusted out, despite its age, it has remained standing, even as all of the schoolbuildings around it, some of concrete, and others of timber, collapsed. Much still needs to be known about thischurch, but perhaps when we are looking at this structure we are looking at the future, and not just at the past.Embodied in this magnificent survivor may be at least one idea of how we can build durable and safebuildings in earthquake areas that can remain standing after an earthquake a century later.

Footnotes1 A more detailed discussion of this research will be published in: Randolph Langenbach (forthcoming) “Was Haiti in 2010 thenext Tangshan in 1976” ICOMOS Symposium: Tangible Risks, Intangible Opportunities: Long-Term Risk Preparedness andResponses for Threats to Cultural Heritage, Beijing, China, 2012, Proceedings.2 http://www.unitar.org/unosat/node/44/14253 Further information by scholars in a number of different disciplines can be found in the papers contained in the “2010 HaitiEarthquake Special Issue” of Earthquake Spectra, Volume 27, Number S1, October 2011, published by EERI, Oakland, Ca. USA.4 http://www.buffalo.edu/news/releases/2010/01/10872.html5 Kubilay Hicyilmaz. 2010. Email correspondence with author dated May 31, 2010. To see the list, go to:http://www.haiti-patrimoine.org/Haiti-RC.pdf6 Anna F. Lang and Justin D. Marshall. 2011. “Devil in the Details: Success and Failure of Haiti’s Nonengineered Structures,” Earth-quake Spectra, Vo. 27, No. S1, Earthquake Engineering Research Institute (EERI), Oakland, Ca., USA.7 Randolph Langenbach. 2008. Learning from the Past to Protect the Future: Armature Crosswalls, Engineering Structures, El-sevier. Vol. 30, No. 8, August 2008, pp. 2096-2100 (www.conservationtech.com/armaturecrosswalls.html)8 RMS FAQ: 2010 Haiti Earthquake and Caribbean Earthquake Risk:http://www.rms.com/publications/Haiti_Earthquake_FAQ.pdf 9 John Ripley Freeman (1932). Earthquake Damage and Earthquake Insurance, McGraw-Hill, New York.

Photos by © Randolph Langenbach, except as marked.

19

Figure 13. Saint Louis de Gonzague Chapel ca. 1890 in central Port-au-Prince showing external lightweight steel frame onmasonry walls.


Streets of Jacmel, HaitiAllen Lowry AIA

James Monday Architect

elsewhere in Caribbean. We are fo-cused on the restoration, renovationand re-development of two port areastreets and the beauty of buildings andculture dating to the mid-19th Century.

Jacmel IntroductionJacmel was founded in 1634, and wasone of the major commerce centers inthe Caribbean for coffee and cocoacrops grown on the mountainous southcoast of Haiti. Most buildings in Jacmeldate to the 18th and 19th centuries andare unchanged from their originalforms. Jacmel was the original and bestdeep-water port for Haiti. Many shipscalled here daily to exchange exportcrops for fuel and hardware goods. Theoriginal Douane (customs) buildingand virtually all merchant and ware-

house buildings remain, though all re-quire extensive repair. Though never amajor recreation center, Jacmel ac-quired and retains a reputation asHaiti’s “artist colony”. This is a solidfoundation on which to build Jacmel’sfuture. This quiet corner of Haiti offersbeautiful beaches and soft breezes.The town’s downtown district offers astrong immersion in Haitian cultureand art, in a setting of fine old historicbuildings. This project will demon-strate how sensitive restorations canpreserve the past while securing a vi-able commercial and cultural future forJacmel, in defiance of historical politi-cal and cultural oppression over thepast four centuries.This study was begun in 2012 with athree week trip to Port-au-Prince andJacmel. We visited many sites and metpeople from all walks of life, witnessingtheir struggle and their power to over-come incredible hardships. Allen Lowryreturned in 2013 to conduct additionalresearch and to establish better localrelationships. It is clear that a more

AbstractThis prospectus states a need andposits a scope of work for the renova-tion of the Historic Port area of Jacmel,Haiti. After 200 years of importantcommercial activity, the historic core isin ruins and in danger of being lost toneglect and improper development.Now a UNESCO World Heritage WatchList Site, the need for preservation ismore widely perceived.Known as a unique cultural arts centerfor Haiti, as well as for its uniqueyearly Kanaval celebrations, Jacmelhas nonetheless remained isolatedenough to fail to attract capital invest-ment that would have kept it healthy.Lacking dependable air service, goodroads or a serviceable port for cruiseships, Jacmel stands to miss out on thecurrent wave of development seen


20

21

comprehensive effort is required to ac-curately evaluate and frame a workablemaster plan for the historic port andcommercial/cultural center of Jacmel,especially now that it is on the UNESCOWorld Heritage Site Watch List. We be-lieve that our expertise and ability toform consensus with residents can beinstrumental in creating a balancedplan between restoration, preservationand new development for Jacmel.We intend to help create an engine forthe indigenous arts culture in Jacmel tostimulate change for economic pros-perity in the region by establishing anenvironmental workshop where artistsand critical thinkers take charge oftheir future and resolve their conflictswith internal and external govern-ments and corporations who havelorded over them to fulfil their own in-terests. We believe that the Jacmelianculture has the power to stimulatechange and that by creating a space fordialogue and activism within this artscolony, new opportunities for re-imag-ining economic realities will emergeand prevail over traditional institu-tional conflict and oppression.We hope that this prospectus willlead to joint venture partnerships andfunding to produce a report similar tothe Preservation of The GingerbreadHouses of Haiti, by the World Monu-ments Fund / ICOMOS, the PrinceClaus Fund and FOKAL; and that wewill be able to establish a communitybased field office in Jacmel to reachthese goals.

Jacmel HistoryFounded before Haiti’s independencefrom France in 1804, Jacmel’s portserved the transport needs of largecommercial operations, exchangingcrops such as coffee, cacao, sugar andtobacco for foreign trade products.Once wealthy, the city of 60,000 wasthe first on the Hispaniola Island tohave electricity, street lighting andtelephones. Jacmel has strong ties toSouth America and was once home tonotables such as Simon Bolivar andJohn James Audobon.The large scale of trade necessitated

large processing and storage facilities.The port area has many fine examplesof old masonry warehouses, manyworthy of preservation. Streets weregenerally wide and offered shadedsidewalks to pedestrians through a se-ries of connected arcades and over-hanging balconies. Many of those builtof wood burned down in fires, notablythe fire of 1895 from which there wasonly modest permanent recovery.Today, the streets of Jacmel are gener-ally hot and barren and often unpaved.Virtually, all human activity takes placein the few areas of shade, or indoors.Signage and street lighting are virtu-ally non-existent.

Jacmel: Typologies of the cityafter the 2010 Earthquake The Ministry of Public Works, Trans-

port and Communications (MTPTC)and The Institute for the Protection ofNational Heritage (ISPAN) are re-sponsible for “tagging” all damagedbuildings in Haiti with ratings that in-dicate the structural integrity and theoccupancy risk to the public withpainted stencils and freehand strokesof numbers & colors that are a kind ofinstitutional graffiti. Artists (particu-larly in the small coastal town ofJacmel) have added their own hiero-glyphic narrative on current condi-tions that are transitive andephemeral in nature (due to their useof pastel crayons & chalk). The citywalls and doorways are their can-vasses. If the message is embedded inthe medium, their art delivers a pow-erful statement of their struggle &their optimism in recovery.


Assessment of Buildings & Sites for Development in the Historic Port District.MTPTC Designation RED: UNSAFE. The building is not reusable with out major structural repairs.MTPTC Designation YELLOW: RESTRICTED USE. The building is temporarily unserviceable, withsignificant structural damage.MTPTC Designation GREEN: SAFE. The building is serviceable, with no or minor structural dam-age.VACANT PROPERTY: Suitable for Development.

22

Jacmel: Typologies of the cityDouane / Historic Port DistrictJacmel is under consideration by UN-ESCO as a World Heritage site and iscurrently on their Watch List. RueCommerce and Rue St. Anne are mostassociated with this history but are inprecarious shape due to the 2010earthquake. Every new restorationproject will leverage both tourist anddonor funds necessary to launch andcontinue life in this remote but beauti-ful region of Haiti.

Jacmel: Typologies of the cityRue du CommercePreservation, Redevelopment StrategyIn general, Jacmel buildings are madeof un-reinforced masonry brick or con-crete block walls with minimum rein-forced concrete or wood beam floors.


This method of construction results inbuildings that are extremely suscepti-ble to failure in seismic or ground set-tlement situations.Poor foundations can exacerbate fail-

ures during ground movement events.“X” shaped wall cracking and failuresare classic indications of structureslacking sufficient strength to resisteven minor seismic events.

Jacmel Commerce Street.

23

Haiti has demonstrated its exposureand susceptibility to major earthquakedamage and loss of life, particularly inthe southern regions.The Plantain Garden Zone Fault, activein 2010 is a major threat to strike again.In Jacmel, the typical mode of wall fail-ure expresses this condition; and indi-cates a need for customizedpreservation and restoration techniquesfor walls built in this fashion. Failure toaddress this threat will lead to furtherdamage, destruction and loss of life.Such damage will continue to set Jacmelback and will create a real and per-ceived danger to visitors and investors.The risk to investment in Jacmel’s futuredevelopment will be extremely limitingwithout establishing and enforcingproper standards for repair.Restoration of Jacmel’s “historic fabric”is essential to its economic and cul-tural recovery. Historic fabric is origi-nal construction, including the originalmaterials, design, finish and placementthat allows measurement of the his-toric truth of the built environment.One may repair original constructionand preserve historic value by restoringand reinforcing what remains, or by re-placing structure and buildings withmaterial of identical type and origin.When streets are repaired, build themback better with adequate drainage,raised sidewalks & underground utili-ties. Add integrated solar poweredlighting to increase pedestrian safetyat night. Add street names at street corners:painted on buildings by local artists.When buildings are renovated, buildthem back better with engineered seis-mic reinforcing materials.If new buildings are not realistic, retro-fit building façades and convert vacantlots to other uses, like pocket parksand local vendor markets.Add new lightweight porticos andcolonnades wherever possible tostrengthen the fabric of Jacmel’s archi-tectural heritage.

Jacmel: Typologies of the cityRe-DevelopmentEvery site within the Historic Port Dis-

trict will be fully documented and eval-uated by a team of trained restorationarchitects & engineers to determinethe structural integrity and potentialfor preservation, restoration and/ornew development. Every proposed restoration project willbe evaluated for its construction costand economic potential within a newmaster plan and guidelines for HistoricPort District Standard Guidelines. Adaptive re-use of existing buildings

will be given first priority, to includenew spaces for shops, restaurants, gal-leries, artist’s studios, outdoor marketsand housing. With additional funding support, newdevelopment sites for hotels, cafés,restaurants & shops along the Embar-cadero will be recommended underHistoric Port District Standard Guide-lines that we will write in partnershipwith local artists, planners and criticalthinkers.


Preservation, Renovation and New Development in the Historic Port District.BLUE: Re-developed under Historic District Standard Guidelines.GREY: Renovated under Historic District Standard Guidelines.GREEN: Restored under Historic District Standard Guidelines.ORANGE: New Development Site designed to meet Historic District Standard Guidelines.

n el marco de la actividad de tutela y conservación que lleva a cabo la Soprintendenza per i Beni Architettonicidelle Marche (Italia), se ha previsto, para el año 2014, el inicio de las obras de restauración de una estructurade gran interés y valor histórico, perteneciente al sistema defensivo diseñado por el arquitecto del siglo XV

Francesco di Giorgio Martini – célebre por su Tratado de Arquitectura Civil y Militar –, hoy en un estado que amenazala completa ruina, causada en parte por la destrucción sistemática e intencional iniciada ya pocas décadas despuésde su construcción.Se trata de un torreón colocado en la cima de una colina, con vista hacia al centro histórico de Cagli, pequeñapoblación, sugestiva y bien conservada, que surge en el centro de Italia y constituye todavía hoy un notable ejem-plo de ciudad renacentista. Dicha torre es uno de los pocos residuos aún existentes del sistema fortificado que pro-tegía la ciudad y que constituía uno de los ejemplos más significativos de edificios de carácter militar realizados porel arquitecto de Siena en las Marcas del Norte1. Los escasos restos conservados y que hoy en día se muestran irregulares y discontinuos, aislados y en grave estadode decadencia, estuvieron, al contrario, perfectamente y magistralmente conectados entre ellos, come se puede apre-ciar en la perspectiva aérea de Francesco di Giorgio Martini, conservada en el Códice Magliabechiano de la BibliotecaNacional de Florencia2. El dibujo muestra cómo la torre superior estuvo ligada a la torre circular inferior por medio de

un pasaje subterráneo, que todavíaexiste, aunque parcialmente ocluido.Como mencionado anteriormente, ladestrucción deliberada comienza yaen la época del Duque Guidobaldo daMontefeltro (hijo del célebre Duquede Urbino, Federico da Montefeltro),el cual, en 1502, durante la guerracontra el hijo del papa Alejandro VIBorgia (el Duque de Valentinois), or-denó su desmantelamiento. La des-trucción no fue, sin embargo, total,ya que se conservó enteramente latorre inferior y una parte de las es-tructuras defensivas que fueron in-corporadas en el cercano conventode los frailes capuchinos, erigido amediados del siglo XVI.Dada su importancia histórica, laSoprintendenza ha incluido en su

El complejo fortificado de Cagli en eldibujo de Francesco di Giorgio Martini.(Florencia, Biblioteca Nacional, CódiceMagliabechiano II. 1. 141, fol. 68 v.).

24


El proyecto de consolidación de la torrede Francesco di Giorgio Martini en Cagli (Italia)Stefano GizziSoprintendenza per i Beni Architettonici delle Marche - ICOMOS Italia

E

Vista panorámica de Cagli. En primer término, la torre inferior.

El convento de los capuchinos (a la izquierda) y las ruinas de la torre superior (a laderecha).


programa trienal de intervenciones,la restauración de los restos de latorre superior, gracias a la disponi-bilidad de recursos extraordinariosrecabados de los fondos de lalotería, que permitirán ejecutar laobra en tres fases3.Desde el punto de vista estructural,uno de los temas preocupantesconcierne el acentuado debilitamientode la base de los muros de mam-postería de la torre. A primera vista,la intención sería la de reconstruir in-tensivamente las partes faltantes; sinembargo, es importante señalarcómo ya, en proyectos anterioreslamentablemente no financiados, laSoprintendenza había adoptado elcriterio de la mínima intervención(según la acepción acuñada por Gus-tavo Giovannoni), es decir limitandolo más posible la transformación de laimagen del edificio. Por lo tanto, elproyecto se concentra sobre todo enla reintegración del núcleo de mam-postería, en línea con otras interven-ciones efectuadas en Italia sobre todoen contextos arqueológicos, como elTemplo de Venus Cnidia en la VillaAdriana, la tumba de los Horacios yCuriacios en Albano o los diversossepulcros de la época romana exis-tentes en la via Appia Antigua. Efectivamente, este tipo de inter-vención se ha afirmado, desde losinicios del siglo XX, en varios monu-mentos famosos de la antigüedad,empezando por la restauración, delos años Veinte del Novecento y di-rigida por Jules Formigé, de los Tro-feos de Augusto en La Turbie (MonteCarlo), quien logró detener, restau-rando únicamente el núcleo, el dete-rioro muy avanzado de ese edificiode la época imperial.

Porción del sistema defensivo superior y su estado de deterioro.

Las estructuras de la torre superior con el paisaje de las Marcas.

A la izquierda y al centro, ambientes interiores abovedados; a la derecha, detalle del núcleo de mampostería, con insercionesde la piedra llamada marmarone rosado, presente en otros edificios militares de Francesco di Giorgio Martini.

25

Los muros de la torre superior deCagli están constituidos por un relle-no de mampostería realizado enpiedra caliza, mezclada con frag-mentos de piedra y de ladrillo. Lapiedra caliza es la llamada mar-marone rosado de Cagli, diferentedel marmarone almendrado, pre-sente en las fachadas de los palaciosmonumentales de la zona. Se tratade una piedra compacta y dura, quese encuentra en otros edificiosatribuidos a Francesco di GiorgioMartini, existentes en el territorio delas Marcas4. El paramento original,del que se conserva sólo una partemuy limitada, está también rea-lizado en piedra caliza y en piedrarosada de Cagli, dispuesta en hiladasregulares, mientras que en algunaspartes, probablemente de épocasposteriores, se presenta como unopus listatum. En otros puntos deledificio se reconocen diferentes in-tervenciones efectuadas a partir delsiglo XVI; sin embargo las más in-congruentes parecen ser las ejecu-tadas en épocas más cercanas a lanuestra, de las que desafortunada-mente no se conserva docu-mentación alguna. El acabado finalde las torres, tanto de la superiorcomo de la inferior, consistía en unafina capa de revoco, de la cual sehan encontrado algunos restos bajola cornisa de la torre inferior, que, alcontrario de la superior, se encuen-tra muy bien conservada y ha sidorestaurada recientemente. El proyecto de restauración sebasa en el uso de técnicas y detecnologías tradicionales, con rein-tegraciones de la mampostería fal-tante, efectuadas al pie de los

muros para evitar el riesgo de colapso por cargas puntuales, así como en la restitución mínima de algunos sillarescon el fin de otorgar mayor resistencia a la base. Se evitarán inserciones ocultas de elementos metálicos, que daríanlugar a un comportamiento estático muy localizado, y someterían el antiguo núcleo a una función puramente estética.Si bien es cierto que del marmarone rosado existen varias canteras históricas en los alrededores de la ciudad, unode los problemas de esta intervención es que tales canteras están hoy protegidas por la ley y no está ya permitidoextraer material; sin embargo se debe recordar que, en otros países del Mediterráneo, en el caso de la restauraciónde algunos monumentos excepcionales se ha permitido volver a cavar la piedra de las canteras cerradas, como hasucedido, por ejemplo, con las de mármol pentélico, que el arquitecto Manolis Korrès logró reabrir para intervenir enel Partenón. La operación se completa con el uso de un mortero a base de cal, libre de sal, mezclado con arena depozzolana, capaz de garantizar una excelente resistencia. Se prevé también la eliminación de los empujes de la tierray la remoción de las raíces y de la vegetación, prestando la máxima atención a la relación con el contexto ambientaly paisajístico de los alrededores. Se trata, por ahora, de una intervención dirigida más a la consolidación que a la re-construcción de una hipotética facies de la torre superior, que sólo sería posible realizar en caso de que se encontraranueva documentación de archivo.

Notas1 M. Dezzi Bardeschi (ed.), Francesco di Giorgio e l’ingegneria militare del suo tempo, Artigraf, Firenze 1968; G. Volpe, La Rocca diCagli, en F. P. Fiore – M. Tafuri (ed.), Francesco di Giorgio architetto, Electa, Milano 1993, pp. 226-229; D. Cardamone, L’ “inge-gnario” Francesco di Giorgio Martini nelle Marche, in “Rimarcando”, n. 2, 2007, pp. 68-73.2 Firenze, Biblioteca Nazionale, Codice Magliabechiano II. 1. 141, fol. 68 v.3 Director Regional de Bienes Culturales Lorenza Mochi Onori, Soprintendente Stefano Gizzi, Proyecto Biagio de Martinis, ConsulenteMario Lolli Ghetti.4 Cfr. A. Mazzacchera, La Rocca e il Palazzo pubblico del Duca Federico da Montefeltro. Nuovi documenti e riflessioni sulle fabbrichedi Francesco di Giorgio a Cagli, en F. Colucci (ed.), Contributi e ricerche su Francesco di Giorgio nell’Italia Centrale, Simposio di Studi,(Urbino, 22 marzo 2003), Ed. Comune di Urbino, Urbino 2006, nota 51 a p. 128.


Estado de deterioro de la base del murode la torre.

La torre inferior, recién restaurada.Interior del pasaje de conexión entre lastorres superior e inferior.

La torre superior, reducida a núcleo, confragmentos en opus listatum.

26

27

Scientific reports Iscarsah newsletter n. 5/2013

Comparison of calculated and measured dynamics characteristics of the Church of St. Peter and St. Paul, Prague (Czech Republic)Daniel Ureña-Muñoz - Structural Engineer - Universidad de Costa Rica

Stanislav Pospisil - Structural Engineer. ITAM Czech Republic

he Church of St. Peter andPaul, in Prague, Czech Re-public, is a historical con-struction. It was observed

that the triangular gable wall inthe façade, due to the ringing ofthe bells, started to vibrate out ofits plane. The dynamic propertiesof the church were measured withaccelerometers in 2002, and thenit was concluded that the gablewas in resonance with the ringingof the bells, so it was necessary toretrofit it. In the year 2007, afterthe retrofit of the gable, again thedynamic properties of the churchwere measured, and it was con-cluded that the gable was not inresonance with the ringing of thebells.The values of the dynamic charac-teristics of the building, before andafter the retrofit of the gable, wereobtained only using experimentaltechniques. In this investigationthese parameters were obtainedwith structural models, and thenthey were compared with the ex-perimental values.With the structural model and theexperiment for the year 2002, itwas possible to determine that thegable was in resonance due to theringing of the bells. And in withthe model and the experiment forthe year 2007 it was possible toconclude that the retrofit worksavoid the resonance phenomena.

1. IntroductionThe Church of St. Peter and Paul,is a historical construction thatwas built between the 19th-20thcenturies with traditional materi-als (stone, bricks, covered withslate on wooden truss). It was ob-served that the triangular gablewall in the façade, due to the ring-ing of the bells, started to vibrateout of its plane. Because of thissituation, the dynamic propertiesof the church were measured withaccelerometers in 2002, and thenit was concluded that the gablewas in resonance with the ringingof the bells, so it was necessary toretrofit it. In the year 2007, after

T the retrofit of the gable, again thedynamic properties of the churchwere measured, and it was con-cluded that the gable was not inresonance with the ringing of thebells.The values of the dynamic charac-teristics of the building, before andafter the retrofit of the gable, wereobtained only using experimentaltechniques. The other possibilityto obtain these values is withstructural models. In this investi-gation these parameters were ob-tained with structural models, andthen they were compared with theexperimental values.If the mechanical properties andgeometrical characteristics thatare necessary to take into accountfor the model are conservative,and the boundary conditions areaccording to the real conditions,the values are going to be accept-able (in the tolerance range). In this specific case, the experi-mental results of the frequency ofthe historical building were veryuseful because they helped to cal-ibrate the analytic model.

1.1 State of the artThe mechanical properties of his-torical constructions, together withtheir complex configurations, oftenmake it difficult to apply dynamicactions in order to study theirstructural response.In structures as bell towers, themotion of one or more of the bellspresent can be exploited to pro-duce distinct dynamic actions. Inthat case, it is possible to comparethe experimental dynamic behav-ior of such a tower with the valuespredicted by discrete models. Thisprocedure was followed in differ-ent historical buildings, for in-stance:(a) Matilde's Tower in San MinitaoItaly (Beconcini et al, 2001).(b) The Wisłoujście Fortress inGdańsk, Polland (Szymczak et al,2006).(c) The Arch-Cathedral Belfry inVilnius, Lithuania (Szymczak et al,2006). (d) San Nicolás bell tower in Va-lencia, Spain (Ivorra et al, 2006).In all the cases, according to theresults that were obtained in the

Figure 1. Discrete Models of Historical Constructions(a) Matilde's Tower in San Mini-ato, Italy (Beconcini et al., 2001); (b) The Wisłoujście Fortress in Gdańsk, Polland

(c) The Arch-Cathedral Belfry in Vilnius, Lithuania (Szymczak et al, 2006); (d) SanNicolás bell tower in Valencia, Spain (Ivorra et al, 2006).

investigations, when the values ofthe frequencies were compared,they were acceptable becausethey were in the tolerance range(±10%). The experimental valuescorresponds to the frequenciesvalues that were measured "insitu" with accelerometer. The pre-dicted values were obtained withdiscrete models. The pictures ofthe towers and their structuralmodel are presented in Figure 1.

1.2 ScopeFor the structural model, becauseit was focused in study the re-sponse of the gable, before andafter the retrofit, only a section ofthe structure was modeled, withFinite Element Analysis, using thesoftware SAP 2000. For thismodel, the elements were consid-ered as shells (2D elements), thesoil was considered as completelyrigid, the masonry was assumedas homogeneous and isotropic,and the analysis was carried outonly in the linear range.The calcu-lated dynamic characteristics corre-spond to the eigen frequencies

values obtained with the dynamicanalysis of the structural model. For the measured dynamic char-acteristics, the previous data(ITAM Reports) for the year 2002(before the retrofit) and the year2007 (after the retrofit) weretaken into account. In both casesthe structure was excited by theringing of the bells, and then thefrequencies were obtained analyz-ing the results in the frequencydomain. The results that were an-alyzed in this investigation werethe values that were obtained dueto the dynamic excitation causedby the bells J1 and J2.

2. Description of the StructureThe Vratislav II´s Kostel Sv Petraa Pavla (Church of Sts Peter andPaul) is located in Vyšehrad, inPrague, Czech Republic. Accordingto the ISCARSAH (InternationalScientific Committee For Analysisand Restoration Of Structures ofArchitectural Heritage) Recom-mendations (2001), it is very im-portant to recognize thatconventional calculation tech-niques and legal codes or stan-dards oriented to the design ofmodern constructions may be dif-ficult to apply, or even inapplica-ble, to ancient structures. Andbecause of that, it states the im-portance of a scientific, multidisci-plinary approach involvinghistorical investigation, inspection,monitoring and structural model-ing and analysis (Figure 2).So according to these recommen-dations, it was reviewed the his-tory of the church, the presentcondition (structural configura-tion), the monitoring (data), andthen the structural model that wasperformed.

2.1 HistoryThe history of the Church of St.Peter and Paul at Vyšehrad startsafter the year 1070, when theKing Vratislav I founded the Chap-ter House. According to Necavátal(2000), the church has been re-built and modified since 1070, soits history could be divided in 7periods (the time line is shown inthe Figure 3): I. Romanesque(First Stage); II. Romanesque(Second Stage); III. Early gothic;IV. High gothic; V. Renaissance;VI. Baroque; VII. Neo Gothic. Theseventh building stage was a neo-Gothic reconstruction, which has

been preserved up to the present.It took place between 1885 and1903 according to plans of themaster builder, Joseph Mocker. Re-garding the bells, they have beenpreserved from the original Ren-aissance section of the building,and they now grace the presentneo-Gothic church.

2.2 Present Condition (Struc-tural Configuration)The cathedral was built with tradi-tional materials (stone, bricks,covered with slate on woodentruss). The building is made up ofthree naves (Figure 4, plan view);its total width is 30 m and thelength 56 m . The height of theroof crest is 28 m. As it could beobserved in Figure 5, there aretwo towers in the façade: bothhave the same height: 60 m. Thesquare cross-section of each toweris 7 m × 7 m, the bells are hung inclassical wooden stools placed atthe level about 29 m. There aretwo old bells in the southern tower(J1, J2), four recently mountedones in the northern tower (S1 –S4). All bells exert swaying motiondriven separately by electric mo-tors. Besides, there is a set of 12stable bells with clappers con-trolled by computer in northerntower, used for playing some song. The material of the walls is ma-sonry mainly constituted by stoneand lime mortar. The thickness ofthe masonry of the building variesbetween 0.3 m and 1.2 meters, itdepends where the masonry is lo-cated in the building. Basically thethickness of the lateral walls is 1m, and the thickness of the wallsthat are in the façade is 1.2 m.Regarding the mechanical proper-ties, conservative values for thismasonry are: specific weight 22KN/m3 and elastic modulus 4 GPaBetween the two towers, it is alsopossible to see the gable, but itsdescription is in the next section.The church interior was recentlyrefurbished and also its structureseems to be in good order andcondition (Figure 6). In the lateralview (Figure 7), it could be seenthat also the state of the walls arein good condition.

2.3 The GableA gable is the generally triangularportion of a wall between the edgesof a sloping roof. The shape of thegable and how it is detailed dependson the structural system being used

Scientific reportsIscarsah newsletter n. 5/2013

Figure 2. ISCARSAH Recommendations (2001): History; Present condition; Moni-toring; Structural Modeling.

Figure 3. Time Line.

28

29


(which is often related to climateand availability of materials) andaesthetic concerns. Thus the type ofroof enclosing the volume dictatesthe shape of the gable.In the Church Sts Peter and Paul,the triangular gable wall over themain entrance starts at the heightof 19.60 m above the church floor,its width between both churchtowers is 9.0 m and the height ofits rectangular part fixed into thetowers is 2.60 m. The height ofthe free-standing triangular part is8.70 m and the cross on its topreaches the height 30 m. Thegable wall does not lean againstthe wooden construction of theroof covering the main nave of thechurch. The thickness of the ma-sonry of the gable is 0.57 m, butthe niches containing statues re-duce it to 0.27 m. (Figure 8).In the year 2002, a study of thechurch (ITAM, 2002) concludedthat the swaying bells excite thestructure by considerable horizon-tal forces with frequencies of one,two and three multiple of the bellsmotion. This excitation can be am-plified by resonance effect of anarbitrary structural element, whichis tuned to one of these frequen-cies. Because of that, some works(repair measures) were developedin the gable.

2.3.1 Repair Measures of thegableIn order to change the natural fre-quency of the gable, some steelplated were anchored in the gableand fixed to the structure of theroof. In the Figure 9 (a) is pre-sented in red, the position in thelateral view of these steel plates. In the Figures 9 (b) is presentedthe detail of how the steel platewas anchored in the gable andthen fixed in different timber ele-ments. The objective was to takeadvantage of the stiffness of thetimber truss out of the plane (thisstructural element is presented inthe sketch in the figure 9 (c).With this work, it was possible tochange the restrictions of themovement of the gable out of itsplane, and as it was reviewed inthe experimental tests it helped toavoid the resonance phenomena.Also in the structural mode, it isgoing to be possible to take intoaccount this retrofit.

3. Monitoring (Data)The data that was analyzed corre-

Figure 4. Plan View. (Necavátal, 2000); Figure 5. Front View (Necavátal, 2000).

Figure 6. Interior of the Church (Necavátal, 2000); Figure 7. Lateral View(Necavátal,2000).

Figure 8. Main facade and detail of the gable.

Figure 9. Details of the retrofit of the gable (ITAM, 2007): (a) Lateral view; (b) Detailof the retrofit; (c) Detail of the timber truss.

sponds to the measurements onthe church building that were doneby ITAM (Institute of Theoreticaland Applied Mechanics, Academyof Sciences of the Czech Republic)in the year 2002 and 2007.

3.1 Explanation of the Proce-dureThe ringing of the bells was usedin order to excite the structure.There are two old bells in thesouthern tower (J1, J2). The bellsexert swaying motion driven sepa-rately by electric motors. Besides,there is a set of 12 stable bellswith clappers controlled by com-puter in northern tower. The char-acteristics of the bells are given inTable 1 and the picture of one ofthe bells is presented in Figure 10.

In order to recover the structuralresponse of the structure, due tothe dynamic excitation of the ring-ing of the bells, 12 measuringpoints were chosen on the frontwall of the church They wereplaced in the following positions: 5

along the height of the southerntower, 5 on the gable wall, and 2on the northern tower. The de-scription of each point is describedin Table 2 and in Figure 11 is pre-sented the position of each point. In each point an accelerometerwas placed. For instance in theFigure 12 is presented the ac-celerometer in the point 8 and inthe Figure 13 is presented the ac-celerometer in the point 10. Theobjective was to measure the ac-celeration out of the plane of allthese points due to the swaying ofeach bell.

3.2 Evaluation of the ResultFor each point, once its data wasanalyzed, the Root Mean Square(RMS) of the displacements in mil-

limeters (mm) and the frequencypeaks in Hertz (Hz) were evalu-ated. As the registrations weremore or less of the sinusoidalshape, the informative maximumamplitudes were checked as √2 ×RMS value.

So for instance, due to the dy-namic excitation of the ringing ofthe bell J1, in 2002, it was possi-ble to recover in the point 6 thegraph that is presented in the Fig-ure 14. In those graphs is possibleto determine according to thespectral density (mm2/s) the peakthat correspond to the frequencyrelated with the modes of struc-ture.According to the results for thepoint 6, is possible to determinethat the peak is related with a fre-quency of 0.88 Hz, and the otherpeaks of spectral density with fre-quencies of , 1.76 Hz and 2.64Hz. The frequency that has thehighest value of spectral density is0.88 Hz, so for this reason in theTable 3, this value is underline. Inthe Table 3, is presented the val-ues of the peaks frequencies foreach point, due to the dynamic ex-citation with the ringing of the bellJ1 and the bell J2. In this Table, as it was commentedbefore, the value of the frequencythat has the highest value of spec-tral density in each point in under-lined. The other value that ispresented corresponds to the RMSof the displacement in millimeters.In the structure, the swaying bellsexcite it by considerable horizon-tal forces with frequencies of one,two and three multiple of thebells’ motion. This excitation canbe amplified by resonance effectof an arbitrary structural element,which is tuned to one of these fre-quencies. The important vibrations found onthe construction were those of thefree standing triangular gable overthe church entrance. It behaved asa cantilever and - due to the reso-nance effect – amplifies the negli-gible excitation of the base intoabout centuple response of thetop. Actually, in the Table 3, thehighest value of RMS displacementis for the point 6, and this one islocated in the top of the gable.In the report of 2002, the ITAMstated that: “The gable wall of thechurch under consideration ismost probably damaged due tothe ageing process of its masonry,and has to be retrofitted either byrestoration the mortar joints or byreinforcing the gable, e.g. by anadditional supporting system in-side the church garret.” Due tothis recommendation, it was per-formed a retrofit work, that is de-scribed in the section 2.3.1 Repair


Figure 10. Bell J1.

Figure 11. Measuring points in thefaçade (ITAM, 2002)

Figure 12. Measuring Point in the Façade, Point 8; Figure 13. Measuring Point in theFaçade, Point 10.

30

31


Measures. Once all the works ofretrofit were done, in 2007 theITAM was asked again to measurethe dynamic response of thestructure, and specifically of thegable due to the ringing of thebells. The results of the measuresof 2007, and there correspondvalue of 2002, are presented inthe Table 4.So according to these results, it ispossible to determine that the fre-quency of 0.88 Hz is not presentanymore in the structure once theretrofit work was done. This fre-quency was related in 2002 withthe resonance of the gable, andaccording to the results of 2007,the retrofit is good, because it

changed the boundary conditionsof the gable, and then its naturalfrequency, in the way that nowa-days the gable is not in resonancewith the ringing of the bells.

4. Structural ModelInitially, it was used a simplemodel for the Gable, the problemwith this model, was that it waspossible to obtain a good approxi-mation of the first mode, but forthe other modes, second or third,the results were so far of the ex-perimental value.Because of this situation, a modelof the façade was carried out, andthe elements where shells (2-D el-ements with thickness).

The masonry corresponds to a his-torical construction, so to be con-cerned about the cracks andgeneral damaged in the masonry,a value of effective inertia wastaken into account. Because of thisconsideration, instead of a valuegross value of the second momentof inertia (Igross) a value of effec-tive inertia was calculated and itwas part of the input in the me-chanical properties. The relation of the effective Inertia(Ieff) and the gross Inertia(Igross), is established with thefollowing equation:

In this equation α corresponds toa rigidity coefficient. This value ofα varies between 0.5 and 1. Ac-cording to the results that wereobtained, the values of frequencythat were closer or at least in thetolerance range were when a valueof a was considered equal to 0.6,so the results that are presentedcorrespond to this value of α.

4.1 Model for 2002For the model of year 2002, ini-tially a model focus on the gablewas performed (Figure 15), theproblem with that model was thefact that the eigen frequency was1 Hz, and then the values of theeigen frequencies for the modestow and tree were 4.5 Hz and 5.8Hz. Values that if they are com-pared with the experimental val-ues are so far away, specially forthe second and third mode.The problem with this first modelapproach is related with the factthat the boundary conditions thatwere taken into account did notreflect the real situation of theconnection of the gable and thetowers. The restriction out of theplane was completely fixed, butthe real situation is that there is astiffness associated due to thewalls out of the plane and the me-chanical properties of the masonrythat influences it. In this modelwas assumed that the restrictionsout of the plane (the green pointsin Figure 15) were fixed, but thereal situation as it was com-mented, is that they could moveout of the plane but with the re-striction of the towers, walls out ofthe plane and the façade.

Table 3. Results for 2002 (ITAM, 2002).

Table 4 . Comparison of the Results Measured Before (2002) and After (2007) theRetrofit.

Figure 14 Measuring points in the façade Points 4 (2002). (ITAM, 2002).

Because the model that was per-formed did not bring good approx-imations, and the boundaryconditions that were assumed didnot reflect the real situation, itwas decided to model a section ofthe building.In the Figure 16 is presented thesection of the church that wasconsidered. The reason of whyalso the towers were included inthe model was that they couldhelp to model better the restric-

tions out of the plane and also thatin them are the bells and thespires, and they are considerableweighs that influence the result ofthe eigen values.According to the recommendationsof Lourenço, 2001, that were al-ready commented in section 3.1,

in this 3 D model, the elementsthat composed it, are 2D shell el-ements.Once the geometrical configura-tion of structural model of 2002was figured out, it was defined thethickness of each element.In the model different colors wereassigned to a specific thickness,according to that selection, in theFigure 17 is presented the façadeof the model. The four values ofthickness that were determinedwere 30 cm, 60 cm, 100 cm and120 cm, and respectively the col-ors that were assigned weregreen, red, yellow and blue.


Figure 15. Simple Model of the Gable.

Figure 16. Section of the Church thatwas Modeled.

Figure 17. Thickness of the Shell Elements in the Structural Model.

Figure 18. Change in the Length of the Walls Perpendicular to the Façade.

32

33


In the façade presented in Figure17, is possible to see that thethickness of the gable is 30 cm,and in its top is 60 cm, in order toconsiderer the fact that in thispart has a spire. The sculpturesthat are in this area were not in-cluded because they are notlinked to the gable.For the tower there is a sectionwere the masonry is thicker, it isbetween the height of 19 m and29 m. Because of that reason inthe model is possible to see that inthis section of the tower the colorof the elements is red (60 cm)Another important fact that had tobe considered was the openings,specially the arches over windowsand door openings. Initially thearches were not considered, butonce the first results were ob-tained, it was observed that theyinfluenced the stiffness of thefaçade out of the plane. The walls out of the plane wereconsidered, because they are re-lated with the restriction out of theplane of the façade. In the modelthose walls were review in order torepresent as much as possible itsinfluence in the restriction out ofthe plane of the façade. In themodel as it is presented in Figure18, the difference of the length ofwall was considered; the thicknessof those walls is constant.

4.1.1 Results of the model2002For the model of 2002, three eigenvalues were obtained. The firstmode is related specifically withthe gable. It consists in the oscil-latory movement of the gable outof its plane, the value of the eigenfrequency is 0.83 Hz, in the Figure57 is presented the modal shape.As it could be seen, in Figure 17,the movement is related with thegable out of its plain. Just in orderto take into account, the excitationdue to the bells was 0.44 Hz, sothe value of this mode corre-sponds to a harmonic of thatvalue, so clearly the gable is inresonance.For the second mode, i is relatedwith the towers, moving out of theplane of the façade. In the struc-tural model, it was obtained twovalues of eigen values that werevery closed, 1.35 Hz and 1.36 Hz.In order to compare those valueswith the experimental values, theywere grouped as mode 2, but inorder to see the difference in the

mode shape, they were called mode2a and mode 2b. The modal shapeof the mode 2a corresponds to themovement of the two towers in thesame direction, out of the plane ofthe façade, The mode 2b corre-sponds to the movement of the

towers in opposite directions, againout of the plane of the façade.For the third mode, the modalshape is related with the towers,moving in the plane of the façadein the same direction and movingout of the plane of the façade inopposite directions. The reason ofthis movement is that in plane

there is transversal symmetry butin the longitudinal axes there is anasymmetry, the value of the fre-quency is 1.95 Hz.

4.2 Model for the year 2007For the model of the year 2007, inorder to considerer the retrofit ofthe gable, some restriction wereplaced for the gable, in the Figure20, is presented the restrictionsout of the plane that were as-sumed in the model.

4.2.1 Results of the model2007Once the restrictions out of theplane were assumed, in order totake into account the retrofit, themodels shapes that were obtainedare described. With the retrofit

due to the restriction out of theplane of the gable, as it was ex-pected, the mode related with it,disappeared. So for the model for2007, only two eigen values wereobtained.The first mode corresponds to thesecond mode before the retrofit. Asit happened with the mode 2 for the

year 2002, in this case, it was ob-tained two values for the mode 1.The modal shapes were calledmode 1a and mode 1b. In thestructural model, it was obtainedtwo values of eigen values thatwere very closed (1.35 Hz and 1.36Hz) In order to compare these val-ues with the experimental values,they were grouped as mode 1, butin order to see the difference in themode shape, they were calledmode 1a and mode 1b. The modal

Figura 19. Mode 1 (Model for Year 2002).

Figure 20. Model of the Structure for 2007 (after the retrofit).

shape of the mode 1a correspondsto the movement of the two towersin the same direction, out of theplane of the façade.The mode 1b corresponds to themovement of the towers in oppo-site directions, again out of theplane of the façadeThe mode 2 corresponds to themode 3 for the structure in 2002.The modal shape is related withthe towers, moving in the plane ofthe façade in the same directionand moving out of the plane of the

façade in opposite directions. Thereason of this movement is that inplane there is transversal symme-try but in the longitudinal axesthere is an asymmetry. The valueof the frequency is 1.95 Hz.5. Comparison of the results


The results of frequencies that wereobtained "in situ" were comparedwith the values that were calcu-lated, this comparison was donebefore and after the retrofit, as it isshown in the sketch in Figure 21.

5.1 Experimental results of theData 2002 and 2007According to the analysis for eachpoint, it is possible to determinethe value of the value of the fre-quency related for each mode ofthe structure. Those values are

presented in the Figure 22, andthen they are going to be com-pared with the results obtained inthe model.

5.2 Results of the ModelAs it was explained in section 4,

the results were obtained for avalue of α equal to 0.6. The resultsof the frequencies for the struc-tural model for the year 2002 be-fore the retrofit are presented inthe in Figure 23. And the frequen-cies that were obtained with thestructural model are presented inFigure 24.

5.3 ComparisonIn order to compare the calculatedfrequencies with the measuredfrequencies, it was defined a tol-erance range of 10 % for the val-ues. This tolerance was assumedin order to accept that is not pos-sible to take into account in themodel all the conditions of thematerials, structural elements andthe building, the variability in themechanical properties of the ele-ments and the assumptions thatwere described before in thescope.

5.3.1 Before the retrofit, 2002In the Figure 25 is presented theresults of the model whit their re-spectively tolerance range. As itcould be seen, all the values that

Figure 21. Comparison of the results.

Figure 22. Experimental Frequencies. Results of the Experi- Figure 23. Frequencies of the Model 2002. Frequencies Be-

Figure 24. Frequencies of the Model 2007. Frequencies afterthe Retrofit 2007. Figure 25. Comparison of the First Mode, 2002.

34

35

were obtained "in situ" are in thetolerance range.As it was commented before, thevalue for the first mode was re-lated strongly with the value of theeffective inertia. If the analysis iselastic, in order to obtain better re-sults is important to take into ac-count that value α, because it is away to consider the loss of sectionand internal cracks of the masonry.For the second mode the value isrelated with the stiffness of thesprings. In this specific case, avalue was taken (1 Ton/mm), andit was conservative. This valuecould be obtained also with exper-imental tests in situ or anotherpossibility is to model all the struc-ture and then check this value. The third mode is just in the limit.In monitoring, the higher modesare more difficult to measure. Theother fact is that this mode his re-lated with a lateral movement andis accomplished with the move-ment in opposite directions of thetowers.The reason of that movement isbecause this section has only onesymmetrical axes; the longitudi-nal is not symmetric so in thismode is possible to determine tor-sion in the modal shape. Since theaccelerometers were only placedin the façade, and they weremeasured the acceleration onlyout of the plane, it is possible thatthe values recovered were only re-lated with the participation of themode in that direction.

5.3.2 After the retrofit, 2007For the year 2007, it is only com-pared the first mode. As it wasdone for the first mode in the pre-

vious model, it was defined a tol-erance range (±10%). In thegraph of the Figure 26 is presentedthe comparison of the results.Those values are so close, and theresults are acceptable in the waythat the value obtained in the ex-periment is the range of toleranceof the value that was obtained inthe model.In both cases, it was proved thatthe retrofit works, it completelyavoided the resonance phenomenain the gable.According to the results that wereobtained in the model and in theexperiment, once they were com-pared it was found that:- in the structural model and theexperiment for the year 2002, itwas possible to determine that thegable was in resonance due to theringing of the bells- in the structural model and theexperiment for the year 2007, itwas possible to determine that theretrofit works avoided the reso-nance phenomena.

6. Conclusions- It is possible to obtain values offrequencies with a structuralmodel close to the values thatwere obtained with the experi-ment, if in the model the values ofthe mechanical properties of themasonry are conservative and theboundary conditions reflect thereal situation of the structure.

- In the analysis of the results ofthe dynamic response of the build-ing, it was necessary to review thefrequencies that were recovered ineach measured point, in order toobtain the frequencies of the build-ing. It was found in the results of2002, that because some pointswere related with the first mode, itwas not possible to measure thefirst frequency in those points (2,12 and 20).

- When performing a linear dy-namic analysis in a historical build-ing, in order to take into accountthe loss of section and internalcracks of the masonry, a value ofeffective inertia, as opposed togross inertia, yields results closerto the measured values.

- With the structural model andthe experiment for the year 2002,it was possible to determine thatthe gable was in resonance due tothe ringing of the bells. Also in the

Figure 26. Comparison of the firstmode 2007.

model and the experiment for theyear 2007 it was possible to con-clude that the retrofit works avoidthe resonance phenomena.

- In the structural model it waspossible to exclude elements thatwere part of the building as bellsand spires, and obtain acceptableresults because their inertialmasses were included in themodel. Without these masses, thevalues of eigen frequencies werenot in the acceptable range.

7. References1. Beconcini M., Bennati S., SalvatoreW., Structural characterisation of amedieval bell tower. Historical Con-structions, Portugal 2001.2. Beconcini M., Croce P., MengozziM., Dynamic Monitoring and Model Up-dating of a Masonry Bell Tower in Pisa,in Structural Analysis of HistoricalConstructions, New Delhi 2006.3. Ivorra S., Pallarés F., Romero M.,Numerical and Experimental Study ofthe Dynamic Behaviour of San NicolásBelltower (Valencia, Spain), in Struc-tural Analysis of Historical Construc-tions, New Delhi 2006.4. International Scientific CommitteeFor Analysis And Restoration Of Struc-tures of Architectural Heritage (IS-CARSAH), Recommendations for theAnalysis, Conservation and StructuralRestoration of Architectural Heritage.Barcelona 2005.5. Lourenço, P., Analysis of historicalconstructions: From thrust-lines toadvanced simulations Historical Con-structions, Guimarães 2001.6. Morassi A., Dynamic methods fordamage detection in structures, NewYork 2008.7. Necavátal B., Kaptulní chrám sv.Petra a Pavla, in Histórická spolecnostStary Velehrad sídlem na Velehrade,Praha 2000.8. SAP2000, V10, Computers andStructures, Berkeley 2005.http://www.csiberkeley.com/products_SAP.html 9. Szymczak C., Tomaszewska A.,Walukiewicz H., Application of Struc-tural Dynamic Methods in Diagnosis ofHistoric Buildings, in Structural Analy-sis of Historical Constructions, NewDelhi 2006.10. Ústav teoretické a aplikovanémechaniky. Posudek účinku nově za-věšeného zvonu na dynamickéchování věží kapitulního chrámu sv.Petra a Pavla v Praze – Vyšehradě,Praha 2002.11. Ústav teoretické a aplikovanémechaniky. Posudek účinku nově za-věšeného zvonu na dynamickéchování věží kapitulního chrámu sv.Petra a Pavla v Praze, Vyšehradě,Praha 2007.


Documents

Iscarsah newsletter 5 Layout 1€¦ · Khalid El Harrouni, Règlement parasismique des constructions en terre au Maroc (RPCT) Scientiﬁc reports Randolph Langenbach, Rubble Stone