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Investigation of the 1716 Algiers (Algeria) Earthquake from HistoricalSources: Effect, Damages, and VulnerabilityAmina A. Abdessemed-Foufa a;Djillali Benouar b

a University of Blida, Blida, Algeria b University of Algiers, Algiers, Algeria

Online publication date: 20 April 2010

To cite this Article Abdessemed-Foufa, Amina A. andBenouar, Djillali(2010) 'Investigation of the 1716 Algiers (Algeria)Earthquake from Historical Sources: Effect, Damages, and Vulnerability', International Journal of Architectural Heritage,4: 3, 270 — 293To link to this Article: DOI: 10.1080/15583050903161352URL: http://dx.doi.org/10.1080/15583050903161352

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INVESTIGATION OF THE 1716 ALGIERS (ALGERIA)EARTHQUAKE FROM HISTORICAL SOURCES: EFFECT,DAMAGES, AND VULNERABILITY

Amina A. Abdessemed-Foufa1and Djillali Benouar

2

1University of Blida, Blida, Algeria2University of Algiers, Algiers, Algeria

This research article presents the consequences of 1716 Algiers earthquake. The damage

records are collected from the Ottoman archives, consular mails, and communications from

scientists and travelers of the eighteenth century. The 1716 Algiers earthquake is one of the

most significant historical events that affected the city (I¼IXMSK). These entire document

sources, in particular those of the Ottoman regency, were carefully analyzed for more

information about this event. This article also makes it possible to have a clear vision of

the damages as well as the vulnerability of the predominant constructions in Algiers. Thus,

the obtained information constitutes an excellent damage database that will enable research-

ers to work out the future seismic scenario in order to protect cultural heritage of the old

nucleus of Algiers and eventually other historical sites that have the same characteristics.

KEYWORDS: historical earthquake, damages database, earthquake-resistantmeasures,

old nuclei of Algiers, Algeria

1. INTRODUCTION

This work is based on the study of Ambraseys and Vogt (1988) of the historicalseismicity of the Algiers area. Indeed, a great number of historical sources were used aswell as those of France, Germany, and England. This latter work gave a global visionabout the historical seismicity of Algiers area. Concerning the 1716 Algiers earth-quake, a general impression about its extent can be noticed, but without specificdetails: that is, the extent of the damage has been shown, without details abouthousing vulnerability and officials’ assessment.

This work presents, in a complete andmore pointed way, new data concerning thepathologies (vulnerability) and topographic localization of the constructions damages.This contribution is based on the analysis of the Arabic files dating from the Ottomanperiod. These files are those of the wakf (habus), which are governed by the religiousauthorities as the hanafi or maleky muftis. During that time, these two rites managedAlgiers. The used files are in general of domanial (bayt al baylik) or financial and fiscal(bayt al mal) acts. Much information is quite detailed there, and those files concerningthe 1716 earthquake and its damages are important. There is no damage data, but theconcerning information is scattered in different files. So, a systematic analysis of great

International Journal of Architectural Heritage, 4: 270–293, 2010

Copyright # Taylor & Francis Group, LLC

ISSN: 1558-3058 print / 1558-3066 online

DOI: 10.1080/15583050903161352

Address correspondence to Amina A. Abdessemed-Foufa, Department of Architecture, Faculty of

Engineering Sciences, University of Blida, Route de Soumaa, BP 270, Douiret 0900 Blida, Algeria. E-mail:

[email protected]

Received 19 December 2008; accepted 4 July 2009.

270

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number of registers was essential in order to determine the main objective of the presentwork, which is to make this earthquake and its characteristics better known. This workalso aims at evaluating the vulnerability of that time’s constructions, some of which arestill present in the site of Algiers, and to emphasize earthquake-resistant techniques thatresulted thereafter. The results obtained in terms of localization of damage could beused in the development of seismic scenario at the historical core; the constructivetechniques highlighted could contribute to the process of conservation of the culturalheritage in the field of restoration. The Casbah of Algiers is a classified UniversalHeritage site. This methodology could also be used as a basis in other territories thathave the same configuration (morphology, architectural typology, and seismicity).

2. HISTORICAL INVESTIGATION

The Ambraseys and Vogt (1988) studies have substantially improved the under-standing of the earthquake through their use of a great number of basic sources fromthe French Archive, British Foreign Affairs, and historical sources. The remaininglack of damaged constructions in the city, however, made clear the need to furtherinvestigate the Arabic and Ottoman sources and to bring together the results obtainedin such a way as to provide a complete picture of this large earthquake.

This historical research is mainly based on original documents, most originatingfrom institutional sources that provide reliable information regarding the effects of theearthquake, analyzed from different angles (e.g., public, religious, and private admin-istrations). Furthermore the Arabic and Ottoman archival documentation used herehad hitherto been unpublished and had thus been analyzed for the first time in order todepict this seismic event.

The sites preserving the used records for this study are: theAlgerianNationalArchiveCentre (ANA, Algiers, Algeria), the Algerian National Library (Bibliotheque Nationaled’Algerie [BNA],Algiers,Algeria), theOverseasArchive (CAOM,Aix inProvence, France)and the French National Archives (Paris, France). In addition, the religious authorities(malekite and Sunnite) made some important reports about the mosques. With regard toFrench archives, the correspondence between the French Consulate of Algiers and theCouncil of the Navy in Marseilles (France) has been assessed. As a result, it has beenpossible to establish not only a partial database of damages, but also an overall topographiclocation of damages in the old historical nucleus. In addition, the great numbers of Arabsources (acts) describe the effects of this earthquake by providing a very detailed report ofminor construction damages like houses and great buildings such as mosques.

3. 1716 EARTHQUAKE EFFECTS ON ALGIERS

The 1716 Algiers earthquake on February 3 was the largest seismic catastrophefrom theMitidja plains to the Cheliff plains (southeast of Algiers). It occurred at 9:45AM (local time) and caused very serious damages. There was a total collapse ofnumerous houses; many buildings suffered considerable damages and were uninhabi-table (CAOM 1716–1717; Anonymous manuscript n.d.; Consular mail 1716; Gazettede France 1716; Comelin 1720; Ibn Redjeb 1922 [1740]). Not only were the pooresthouses touched but also solid constructions such as palaces, which suffered extensivecracking. With regard to the mosques, they were slightly damaged (only two among100). The earthquake impact was worsened by a huge fire that broke out immediatelyafter the earthquake. In other different areas, whole blocks of houses were either

ALGIERS EARTHQUAKE 271

INTERNATIONAL JOURNAL OF ARCHITECTURAL HERITAGE 4(3): 270–293


totally destroyed or their internal walls collapsed totally. In the higher area of the city,many houses were in danger of collapsing and had to be propped up; some collapsedpartially or subsequently had their upper floors demolished.

On February 26, 1716, a violent earthquake commotion damaged what was leftof the buildings that had resisted the first shock. As a result, the Dey ‘Ali Shaush(Governor) issued new preventive measures to be used during the city reconstruction.To this earthquake, Roussel (1973) assigned the intensity of I¼X MM, whereasAmbraseys and Vogt (1988) determined that this intensity could not be reachedbecause no solid construction was damaged; thus, they assigned an intensity of I¼7MSK. An anonymous map (Algiers 1830), in absence of any map dating from theeighteenth century, can be used as a reliable reference to the earthquake situation.

4. THE MEDINA OF ALGIERS IN 1716

In 1716, Algiers showed the typical characteristics of a medieval MoslemMaghreb city such as Fez (Morocco) and Tunis (Tunisia) (Le Tourneau 1949),where the building blocks are of various sizes, the parcels are fully built, and thehouses are leaning against each other forming a compact unit (Figure 1). In addition, agreat number of narrow and short streets were covered by galleries, on top of whichthe houses extended, thus creating roofed passageways called sabat. Algiers wassurrounded by walls built before 1517 with nine gates and 12 batteries (Figure 2).

Figure 1. Axonometric view of a block (Atelier Casbah 1980).

272 A. A. ABDESSEMED-FOUFA AND D. BENOUAR



4.1. Architectural Typology

According to various historical sources in Algiers (Haedo 1578–1581; Shaw 1808;De Grammaye 1998 [1670]), all houses were alike. Most of them had a central patio orsquare courtyard surrounded by rooms. The Algiers’ house called dar (Figure 3) wascharacterized by two distinct typologies: the first is a house that is organized around apatio, which may be partially covered by a grid for daylight and ventilation, called darshebbak (Figures 4a and 4b). It is raised from the surface constraints of the parcels,which enables the house to have a patio. The second typology of an Algiers houseresults from a diachronic development of the dar shebbak. It is called alwi (Figure 5). Itresults from the narrowness of the parcels and the requirements of the extraversionimposed by the importance of the urban activity. This type of house had neither pationor grid. As a consequence, this house opened on to external space and was generallysituated on the street borders. The houses in Algiers had several stories, with themajority having three stories. The number of houses was estimated at 5000 in theeighteenth century (Venture de Paradis 1983) and is approximately 800 today (CelluleCasbah 2003). In addition to the houses, there are a great number of palaces with fourfloors. The religious buildings (such as the mosques), the military, and the governmentbuildings were well constructed (Devoulx 1875).

4.2. Constructive Typology

4.2.1. Load-bearing walls The vertical structure of buildings was made up ofbricks masonry or mixed masonry (brick and stone) walls with a thickness varyingfrom 30 cm for the poorest quality to 90 cm or more for defense structures. The brickmasonry walls were bound by a lime mortar (Figures 6a and 6b).

4.2.2. Floors and terraces Floor structures, terraces, and lintels were traditionallywooden, without any provided wall ties to link the walls. They were made of non-squared wood. They comprised two orthogonal lines of thuya logs laid out between awooden boarding. On the top, they were laid by stones of different sizes, ground,mortar, and finally ceramic squares (Figures 7a and 7b). Sometimes these floors reach

Figure 2. Drawing of Stopendeal 1680, ‘‘De Stadt Algier’’ (Esquer 1929) and map of historical nucleus of

Algiers (anonymous, 1830).




Figure 3. Plan, section and facade view of traditional house ‘‘Dar.’’ (Reprinted with permission from

Missoum. Copyright 2003 INAS.)




90-cm thickness in palaces because of the superposition of several logs of thuya lines.All houses were covered with terraces andwere all bleachedwith lime. The brick vaultsabove staircases and corridors sometimes replaced wooden floors in palaces andsometimes covered the prayer rooms in mosques.

Figure 4a. Plan of traditional house ‘‘Dar Shebbak.’’ (Reprinted with permission fromMissoum. Copyright

2003 INAS.)




5. DAMAGE TO CONSTRUCTION ELEMENTS

The traditional vertical structure was mainly built to support its own weight aswell as the weight of floors and terraces (in the case of Algiers) and resistant to the wind.These structures were particularly vulnerable to seismic effects because they were not

Figure 4b. Section and facade view of traditional house ‘‘Dar Shebbak.’’ (Reprinted with permission from





Figure 5. Plan, section and facade view of traditional house ‘‘’Alwi.’’ (Reprinted with permission from





Figure 6. (a) Brick masonry walls. (b) Brick masonry walls constructive typology. (Reprinted with permis-

sion from Abdessemed-Foufa. Copyright 2005 Patrone Editore.)




bonded horizontally. Thus, the shape, the size, the weight and the materials used for thehorizontal structure highly influenced the intensity of the seismic damages.

As a general rule, the vulnerability of the common constructions (houses) can beassessed in terms of the vulnerability classes A and B of EMS-98 intensity scale(Grunthal 1998) with reference to ordinary buildings. However, the vulnerability ofmonumental buildings, such as the religious ones, cannot be easily assessed in terms ofvulnerability classes of EMS-98 intensity scale, because these classes are conceivedwith reference to ordinary buildings.

In general, it is well known that the mosques are important monuments; how-ever, they are in fact very vulnerable. In the case of Algiers, the importance of suchbuildings required a certain care during their construction. Thus, vulnerability of classD, which represents the reinforced masonry, must be used because they did notcollapse during this great earthquake. It is very important to note that few of thesemosques suffered from cracks and the collapse of certain parts (Ottoman Archives1716–1717, 1732; Chergui 2007).

5.1. Minor Building (House) Damage

A systematic reading of the registers gathered in 22 microfilms, of the ANA andCAOM archives, limited to the period going back to 1715 to 1724, was established. Thistemporal delimitation was made according to the amount of time close to the seismicevent for the best determination of the damages. From the analysis of the Arab andOttoman registers one notices that the constructions were constantly maintained thanks

Figure 7. (a) Traditional wooden floors. (b) Traditional wooden floors constructive typology. (Reprinted

with permission from Abdessemed-Foufa. Copyright 2005 Patrone Editore.)




to the type ofmaintenance action (reconstruction and repair works) and themoney spentfor this purpose. Thus, theArab andOttoman sources refer to the damages type and alsoto the reconstruction and the repair works undergone. Consequently, in order to avoidthe arbitrary and tomove away from hazardous interpretations, this work was limited tothe actions carried out immediately after the earthquake.

5.1.1. Total collapse of houses According to the analysis of the Ottoman Files(domanial acts 1716), 14 houses collapsed. However, Comelin (1720), Delphin (1922),Shaw (1808), and Carette (1850) had reported that 200 houses collapsed and that mostof the dwellings were ruined. According to an anonymous Arab manuscript (1637),the country houses called the fahs around Algiers collapsed entirely. The historicalsources as de Tassy (1830) and Burzet (1866–1869), confirmed that the fahs weredestroyed at a distance of approximately 3 km around the city. Carette (1850) andBurzet (1866–1869) reported that the aftershock of February 26 made the damageeven more serious for the houses that did not collapse after the main shock. For thiscurrent research article, the authors assessed the grade 5 of damage.

5.1.2. Wall destruction According to the Ottoman Files (1716), many houses (162)were slightly damaged and repairs were conducted, while others (24) were severelyfissured. For this research article, the authors assessed the grade 2 and 3/4 of damage,respectively.

5.1.3. Floor rupture According to the Ottoman Files (1716), related to the cadastralacts, it was revealed that many first floors (37) of the houses collapsed after theearthquake. Comelin (1720) wrote about the event: ‘‘. . . The house of the ambassadorof France was one of the most beautiful of Algiers. It had three floors before the lastearthquake, now only two floors remain’’ (14). For this research article, the authorsassessed the grade 4/5 of damage.

5.2. Monumental Building Damage (Mosques and Palaces)

There is no detailed report on monumental building damage. The only informa-tion found is restricted to the registers of the religious buildings (claim of real estate).These registers defer all the operations of maintenance, which took place regularly onthe damaged buildings (e.g., earthquake, floods, war). Only two damaged mosqueshave been described:

� The Great Mosque of Algiers (Djama’ al kabir) presented several cracks on thenorthwest walls or the ‘‘qibla’’ walls (Religious Acts 1716–1717; Devoulx 1846;Chergui 2007; Abdessemed-Foufa 2007). The reparations took place only in 1732(Religious Acts 1732; Devoulx 1870; Barges 1877; Chergui 2007; Abdessemed-Foufa 2007).

� The cupola of Sha’ban Khudja mosque collapsed. The reconstruction took placeonly in 1728 (Religious Acts 1716–1717; Chergui 2007; Abdessemed-Foufa 2007).

For this research article, the authors assessed the grade 2/3 of damage for the GreatMosque of Algiers and the grade 4/5 of damage for the Sha’ban Khudja mosque.

Only two mosques were damaged (Chergui 2007), and their damage degree isrelatively considerable (Abdessemed-Foufa 2007), taking into account the fact that




load-bearing walls were fissured and a cupola was destroyed. But considering thenumber of mosques in Algiers, which corresponds to roughly 100 mosques, one canconsider that this type of buildings did not suffer great damage.

It was said that many palaces were destroyed or severely damaged; however,only two of them were described:

� Dar ‘Aziza Palace (the French Embassy): The first floor collapsed as described bythe French Consul S. Clairembaut (Consular mail 1716) and later by Comelin(1720). The damage was thus significant in this residence.

� Dar al Sultan (Al Djenina) Palace, the residence of the regency and the governmentduring that time (Klein 1937): The palace, suffered many cracks, and the Dey AliShaush decided to leave the palace immediately with his court to find a provisionalrefuge in Burdj Mulay Muhammad (called later Fort de l’Etoile).

For this research article, the authors assessed the grade 4/5 of damage for the Dar‘Aziza Palace and the grade 2/3 of damage for the Dar al Sultan Palace.

It is also considered that palaces did not suffer high damages, considering thatonly two among 12 palaces were damaged. One can conclude that the great buildingssuch as mosques and palaces are resistant to the earthquake loads and did not suffergreat damages during the 1716 earthquake.

5.3. Pathologies Recorded

Following the readings of the various types of damage, several pathologies wererecorded as themain cause of the damage. The three main pathologies (vulnerabilities)are:

� The bad construction of masonries, which was a direct cause of destruction and thecollapse.

� The absence of links between the walls, which caused their collapse.� The absence of anchoring of the floors to the load-bearing walls and the absence of

their linkage, which contributed to the collapse of the higher floors.

These pathologies represent the two important lack of damage such as inadequatestructural integrity (bad construction) and inadequate structural resistance (absenceof links and anchoring).

6. STATISTICAL ANLYSIS OF RESULTS

6.1. Synthetic Information

Three types of technical expressions related to the actions of maintenance werefound in the registers. This terminology of the maintenance practices are related to thecontext of their application:

� Bina (construction): In this context, bina means the rebuilding of what wasdestroyed by the earthquake.

� Islah (repair): Islahmeans the repair of what was damaged by the earthquake (suchas cracks).

� Tarki’ (partial repair): Tarki’ means the repair of certain parts of the buildingsdamaged by the earthquake.




6.2. Statistical Analysis of Results

A detailed damage description of 1716 Algiers earthquake on February 3 isavailable for 240 minor buildings (houses) and four monumental buildings (twomosques and two palaces) among 5000 houses, 12 very important palaces, and roughly100 mosques. There was the analysis of 22 microfilms in Algiers (Algeria), and 22microfilms in Aix En Provence (France). Each microfilm analyzed contained 10registers. The statistical analysis is reported in Tables 1 and 2 and in Scheme 1 andTable 3. Tables 1 and 2 summarize, respectively, the number of houses and the greatbuildings such as mosques and palaces that were damaged in each area. Scheme 1 andTable 3 represent the conclusive registers (number) where information was collected.

The map used in this work (Figure 8) has been established by Devoulx (1846),who identified six districts in Algiers. This map correlated damaged houses, palaces,and mosques with their addresses and enable the authors to locate them (Figure 9).

The total number of conclusive registers is 15, which corresponds to the realresult obtained after the analysis of 44 microfilms, thus 440 registers of the AlgerianNational Archives (ANA) and the Overseas Archive of Aix en Provence, France(CAOM). Only seven of ANA among 220 registers and eight of the CAOM among220 registers gave conclusive results, i.e., information on the state of the damage thatcan constitute a first database in term of vulnerability and pathology of constructionsduring this great earthquake.

It should also be emphasized that this analysis does not cover all constructions ofAlgiers. Consequently, the quantified results are representative of constructions con-cerning these registered houses on the domanial acts (Ottoman Files 1715–1724).

The identification of the stricken area and damaged building is demonstrated onthe historical map (Figures 8 and 9). The map of stricken areas is shown in Figure 8.

Collapses, destructions, several cracks, referring to cumulative effects of the1716 earthquake, are available for the remaining 240 houses, two religious buildings

Table 2. Assessment and damage grades of minor buildings after the 1716 Algiers earthquake

Type of damage Slightly damages

Destruction

of floors Several cracks Total collapse Total damages

Grades 2 4 3/4 5

Houses 76 27 15 8 126

Non identified Houses 86 13 9 6 114

Total 162 40 24 14 240

Percent 67.5% 16.66% 10% 5.83% 100%

Table 1. Statistical interpretation of the analysis results (conclusive and non conclusive registers)

Registers state Algiers archives CAOM archives Total

Registers number 220 Registers 220 Registers 440

Conclusive Registers number

(containing information)

07 08 15

Percentage 03.18% 03.64% 03.41%

No conclusive Registers 213 212 225




Scheme 1. Graphic interpretations of the historical resources results (OttomanArchives) of the 1716Algiers

earthquake on February 3 from all the archived data gathered from 1715 to 1724: a) the references

mentioned a total number of 440 registers; b) and c) according to the Algiers and Overseas Archive

(CAOM [Aix in Provence, France]) archives and the obtained results, the total number is 15 registers.




and two palaces. According to these historical sources, four types of damages weredefined. They were classified in terms of EMS-98 damage grades:

� Damage of grade 5 was assessed when the sources clearly reported ‘‘total collapse’’.� Damage of grade 4 was assessed when the sources reported simply ‘‘collapse or

destruction’’.� Damage of grade 3 was assessed when the sources reported ‘‘several cracks’’.� Damage of grade 2 was assessed when the sources reported ‘‘slightly damaged’’.

The summary of damage grades is reported in Tables 2 and 3.

7. NEW EARTHQUAKE-RESISTANT CONSTRUCTIVE MEASURES

The analysis of the earthquake damage indicated that there were two maincauses of the heritage masonry buildings damage:

� Inadequate structural integrity: lack of connection between structural walls at floorlevels, which resulted into out-of-plane vibration, separation, and collapse of the walls.

Table 3. Damage grades of important buildings after the 1716 Algiers earthquake

Important buildings Grade 2 Grade 3 Grade 4/5 Total collapse Grade 5

Great Mosque of Algiers x

Shaban Khudja Mosque x

Dar Aziza Palace x

Dar al Sultan Palace x

Figure 8. Stricken areas (Abdessemed-Foufa 2007).




� Inadequate structural resistance: this resulted into typical diagonal shear crackingand disintegration of walls and, consequently, partial or total collapse of buildings.

For some cases, inadequate structural layouts were the major reasons for partial and/or total collapse.

After the partial destruction of the city of Algiers and its suburban areas, theDey‘Ali Shaush (Governor) decreed to Algier’s population some preventive constructivemeasures (Chesneau 1892). These different techniques have been rediscovered follow-ing a detailed archeological report in situ investigation during the years 2001–2005 onthe historical site of Algiers (Abdessemed-Foufa 2005; 2007).

These traditional preventive measures represent the authenticity of Algiersconstructions. The reconstruction carried out since 1716 has been to the higheststandards of contemporary seismic code and practice. From 1716 onward, new con-structive techniques have been developed for the prevention of masonry structures,especially in the case of interventions for the sake of reconstruction.

7.1. Reinforced Load-Bearing Walls

The brick masonry load-bearing walls were reinforced by a kind of wood calledthuya. Three logs of this thuya were inserted along the width of the wall. They wereregularly distributed every 80–120cm. This kind of disposition of materials—in whichone is rigid and the other flexible—allows absorption of the shear force during theearthquakes (Figure 10). In addition, the walls show very few cracks and do notcollapse. In fact, according to the dynamics of the structures, the elements in masonryplay a significant role in the earthquake response of the building. The lateral

Figure 9. Recorded damages of Algiers’s 1716 earthquake (Abdessemed-Foufa 2007).




earthquake loads tend to deform the panel of masonry in parallelogram shape, causingthe formation of a diagonal rod of compression, which acts at the level of the angles.However, the walls are split in several parts—three or four parts according to the heightof the wall. One of the most important reasons (inadequate structural resistance) forthis lack of damage is the damping from the friction induced in the masonry. Thus, thediagonal shear cracks in the walls of brickmasonry will decrease, so the lateral loads aredistributed with each new layer with a difference of materials. This will prevent thewalls undergoing significant deformation. These walls respond favorably to the earth-quake excitation; it is thus certain that these walls were designed so as to be able to resistthe earthquake loads. This disposition of materials avoids shearing and the effect of rodin the wall because the latter is subdivided in several parts.

These various typologies were compared to those highlighted by the researchwork of Poursoulis (1999; 2000) for Minoan Palace. This technology of reinforcementof masonry with timber was also used in the Greek traditional construction industriesdating back from the Antiquity to the nineteenth century (Touliatos 1992).

7.2. Links of the Walls

The brick masonry walls were also linked to the other by an alternate crossing ofwood logs. In fact Carette (1850) wrote:

I noticed in the old Moorish houses in demolition an excellent precaution taken bythe builders to consolidate the angles. It consists in placing horizontally, every fifty

centimeters in height pieces of wood of approximately two meter long. These partincorporated in the masonry, were prolonged alternatively according to eachperpendicular walls. I saw houses sapped at the base and half demolished, butstill standing due to this artifice of construction’’ (91–93).

Figure 10. Reinforced bricks masonry walls by logs of wood and three dimensional reconstruction of the

walls. (Reprinted with permission from Abdessemed-Foufa. Copyright 2005 Patrone Editore.)




This linking system at angles constitutes a traditional reinforcement technique toprevent the vertical walls from tearing apart (Figure 11). The walls partitions arelinked to their perpendicular walls. The connections are often embedded of themasonry and the logs of wood, which are laid out transversely and longitudinally inthe crossing walls. Several historical constructions around the world (Turkey,Kashmir, India) are reinforced by logs of wood, a matter noticed in the recent earth-quakes (Gulhan and Guney 2000; Langenbach 2007).

7.3. Reinforced Masonry Arches

One of the particular details at Algiers is the arch–column departure in whichthree logs of wood are superposed on two layers of bricks. This system guaranteesa good resistance to forces during earthquake by a slip movement or by rolling(Figure 12a and 12b). In another way, at the intersection of the two arcades, from

Figure 11. Three dimensional reconstruction of the linked angles by wooden logs. (Reprinted with permission

from Abdessemed-Foufa. Copyright 2005 Patrone Editore.)




three to five logs of thuya are inserted inside the bricks masonry to absorb the seismicforces (Figure 13a and 13b). In addition, this gallery of arcades is connected to theload-bearing walls by a discharging arch located at the angles of the gangways and bytimber that is tie connected along the gallery walls (Figure 14).

Figure 12. (a) Arch-Column departure details one layer of three logs of thuya inserted between the brick

masonry. (b) Three dimensional reconstructions of the arch-column departure details. (Reprinted with

permission from Abdessemed-Foufa. Copyright 2005 Patrone Editore.)




This constructive technique was also used in buildings of the historical nuclei inMiliana (Algeria), which is located at 120 kmwest of Algiers. This old city was damagedby the earthquake of 1724 (Shaw 1808). During the post-earthquake reconstruction,these preventivemethods of reinforcement of the capital were used (restoration project ofthe Mosque andMedersa of Sidi Ahmed Ben Youcef, Miliana, Algeria 2007–2008).

Figure 13. Wooden logs inserted at the intersection of the arcades (Abdessemed-Foufa 2007).

Figure 14. Discharging arches of the gallery. (Reprinted with permission from Abdessemed-Foufa.

Copyright 2005 Patrone Editore.)




7.4. Wooden Floors

The traditional wooden floors are constituted by a superposition of two layers ofwood and between them a battening is inserted. This system facilitates the absorptionof the lateral loads by slip movement or rolling (Figures 15).

8. CONCLUSION

The demolition of Algiers after the 1716 earthquake probably explains theabsence of historical sources such as the damage surveys that would have allowedmapping the distribution of the whole city. The interpretation of the available sources(Ottoman Files) describing the damage was limited to the houses that were managedby the religious institutions. One must take into consideration that it is only a partialinterpretation of the effects of this great earthquake.

The Roussel study (1973) came to the conclusion that the intensity assessed inAlgiers considered that the damage was an intensity of XMM. However, the study ofAmbraseys andVogt (1988), suggesting an investigation on the seismicity of the regionof Algiers, concludes that it is improbable that the intensity could reach X MM,because not many buildings were damaged.

The damages of 240 minor buildings and four important buildings were assessedin terms of EMS-98 intensity. This data, although not useful for detecting possibleamplification or disamplification areas, can provide useful information about thevulnerability of the serving buildings and can also serve as an input to evaluate theintensity of the earthquake.

The study presented in this article should be extended in order to provide moredetails about the collapse of the other buildings such as traditional baths (hammam)and military barracks. The rediscovery and the revival of earthquake-resistant tradi-tional techniques, which has been used during the reconstruction of Algiers after the1716 earthquake, can be reused in the field of the preservation of historical buildings inAlgiers.

Figure 15. Wooden floors. (Reprinted with permission from Abdessemed-Foufa. Copyright 2005 Patrone

Editore.)




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APPENDIX

Figure A1. Anonymous Arabic Manuscript from the ANA (Algiers, Algeria).




usthb foufa final paper

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