World Housing Encyclopedia Report

Country: Algeria

Housing Type: Stone masonry apartment building

Contributors:Mohammed FarsiFarah LazzaliYamina Ait-Méziane

Primary Reviewer:Marjana Lutman

Created on: 6/5/2002Last Modified: 6/17/2003

This encyclopedia contains information contributed by various earthquake engineering professionalsaround the world. All opinions, findings, conclusions, and recommendations expressed herein are those

of the various participants, and do not necessarily reflect the views of the Earthquake EngineeringResearch Institute, the International Association for Earthquake Engineering, the Engineering Information

Foundation, John A. Martin & Associates, Inc. or the participants' organizations.

Table of Contents

General Information............................................................................................1Architectural Features........................................................................................ 3Socio-Economic Issues...................................................................................... 4Structural Features............................................................................................. 5Evaluation of Seismic Performance and Seismic Vulnerability.......................... 9Earthquake Damage Patterns............................................................................ 11Building Materials and Construction Process..................................................... 12Construction Economics.....................................................................................14Insurance............................................................................................................15Seismic Strengthening Technologies................................................................. 16References......................................................................................................... 17Contributors........................................................................................................ 18Figures................................................................................................................19

1 General Information

1.1 CountryAlgeria

1.3 Housing TypeStone masonry apartment building

1.4 SummaryThis is a typical residential construction found inmost Algerian urban centers, and it constitutes40 to 50% of the total urban housing stock. Thisconstruction, mostly built before 1950s byFrench contractors, is no longer practiced.Buildings of this type are typically 4 to 6 storieshigh. The slabs are wooden structures orshallow arches supported by steel beams (jackarch system). Stone masonry walls, usually 400to 600 mm thick, have adequate gravityload-bearing capacity, however their lateral loadresistance is very low. As a result, thesebuildings are considered to be highly vulnerableto seismic effects.

FIGURE 1: Typical Building

1.5 Typical Period of Practice for Buildings of This Construction TypeHow long has thisconstruction been practiced< 25 years< 50 years< 75 years< 100 years< 200 years X> 200 years

Is this construction still being practiced? Yes NoX

Additional Comments: This construction was practiced prior to 1950 by French contractors.

1.6 Region(s) Where UsedThese stone masonry buildings exist throughout the northern Algeria. In particular, the multi-storybuildings exist mainly in the major cities e.g. Algiers, Oran, Constantine, Annaba, etc. This constructiontype may constitute 40 to 50% of the urban housing stock.

1.7 Urban vs. Rural ConstructionWhere is this construction commonly found?In urban areas XIn rural areasIn suburban areasBoth in rural and urban areas

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Additional Comments: This type of construction is found in the older urban districts.

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2 Architectural Features

2.1 OpeningsThe number, size and position of openings for a typical floor in a building are shown on the typical plan(Figure 3A). The total window and door area is about 25% of the overall wall surface area.

2.2 SitingYes No

Is this type of construction typically found on flat terrain? XIs this type of construction typically found on sloped terrain? (hilly areas) XIs it typical for buildings of this type to have common walls with adjacentbuildings?

X

The typical separation distance between buildings is 5 meters

2.3 Building ConfigurationThe building plan for this housing type can be of different forms: rectangular, L-shaped, U-shaped, etc.

2.4 Building FunctionWhat is the main function for buildings of this type?Single family houseMultiple housing unitsMixed use (commercial ground floor, residential above) XOther (explain below)

Additional Comments: Buildings of this type are also used as offices and hospitals.

2.5 Means of EscapeMajority of these buildings have only one exit, and one main staircase inside the building in the case ofmulti-story buildings.

2.6 Modification of BuildingsModifications are often undertaken by the residents without any professional assistance provided byengineers. The modifications include the demolition of interior walls, opening commercial areas, and thevertical extensions.

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3 Socio-Economic Issues

3.1 Patterns of OccupancyIn Algeria there is a serious housing crisis. On an average, there are two families occupying the samehousing unit: the parents and a son's or daughter's family.

3.2 Number of Housing Units in a Building10-15 units in each building.

3.3 Average Number of Inhabitants in a BuildingHow many inhabitants reside in a typical building of thisconstruction type?

During the day / businesshours

During the evening / night

< 55 to 1010-20 X> 20 XOther

Additional Comments: In most cases the women in the families are not working and stay at home duringthe day.

3.4 Number of Bathrooms or Latrines per Housing UnitNumber of Bathrooms: 1Number of Latrines: 1

3.5 Economic Level of InhabitantsEconomic Status House Price/Annual Income

(Ratio)Very poor /Poor X 10/1Middle Class /Rich /

3.6 Typical Sources of FinancingWhat is the typical source of financing for buildings of this type?Owner Financed XPersonal Savings XInformal Network: friends and relativesSmall lending institutions/microfinance institutionsCommercial banks / mortagesInvestment poolsCombination (explain)Government-owned housing XOther

3.7 OwnershipType of Ownership/OccupancyRent XOwn outright XOwn with Debt (mortgage or other)Units owned individually (condominium)Owned by group or poolLong-term leaseOther

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4 Structural Features

4.1 Lateral Load-Resisting SystemThe lateral load-resisting system consists of the stone masonry walls built in longitudinal and crossdirections. Wall thickness varies from 400 to 600 mm. Field masonry has been used mainly, massivestones only at the corners and around the openings. Low-strength mortar (either cement/sand or mudmortar) has been used. According to the Algerian Seismic Code (RPA99) and the Strengthening guide,many buildings of this structural type, that suffered damages after last earthquakes (El Asnam 1980,Tipaza 1989, Mascar 1994 and Ain Temouchent 1999), have been strengthened. They were confinedwith reinforced concrete ties in vertical and horizontal direction and with RC slabs used as floor and roofstructures. The maximum building height allowed by the Code depends on the seismic zone (17 m, 14 mand 11 m, for seismic zones I, II and III, respectively).

4.2 Gravity Load-Bearing StructureStone masonry walls are the principal elements of the gravity load-bearing structure.

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4.3 Type of Structural SystemMaterial Type of

Load-BearingStructure

# Subtypes

Masonry Stone masonrywalls

1 Rubble stone (field stone) in mud/lime mortar or withoutmortar (usually with timber roof)

X

2 Massive stone masonry (in lime or cement mortar) XEarthen walls 3 Mud walls

4 Mud walls with horizontal wood elements5 Adobe block or brick walls6 Rammed earth/Pise construction

Unreinforced brickmasonry walls

7 Unreinforced brick masonry in mud or lime mortar8 Unreinforced brick masonry in mud or lime mortar with

vertical posts9 Unreinforced brick masonry in cement or lime mortar

(various floor/roof systems)Confined masonry 10 Confined brick/block masonry with concrete posts/tie

columns and beamsConcrete blockmasonry walls

11 Unreinforced in lime or cement mortar (various floor/roofsystems)

12 Reinforced in cement mortar (various floor/roof systems)13 Large concrete block walls with concrete floors and roofs

Concrete Moment resistingframe

14 Designed for gravity loads only (predating seismic codes i.e.no seismic features)

15 Designed with seismic features (various ages)16 Frame with unreinforced masonry infill walls17 Flat slab structure18 Precast frame structure19 Frame with concrete shear walls-dual system20 Precast prestressed frame with shear walls

Shear wall structure 21 Walls cast in-situ22 Precast wall panel structure

Steel Moment resistingframe

23 With brick masonry partitions24 With cast in-situ concrete walls25 With lightweight partitions

Braced frame 26 Concentric27 Eccentric

Timber Load-bearingtimber frame

28 Thatch29 Post and beam frame30 Walls with bamboo/reed mesh and post (wattle and daub)31 Wooden frame (with or without infill)32 Stud wall frame with plywood/gypsum board sheathing33 Wooden panel or log construction

Various Seismic protectionsystems

34 Building protected with base isolation devices or seismicdampers

Other 35

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4.4 Type of FoundationType Description

Shallow Foundation Wall or column embedded in soil, without footing XRubble stone (fieldstone) isolated footingRubble stone (fieldstone) strip footing XReinforced concrete isolated footingReinforced concrete strip footingMat foundationNo foundation

Deep Foundation Reinforced concrete bearing pilesReinforced concrete skin friction pilesSteel bearing pilesWood pilesSteel skin friction pilesCast in place concrete piersCaissons

Other

4.5 Type of Floor/Roof SystemMaterial Description of floor/roof system Floor Roof

Masonry Vaulted XComposite masonry and concrete joist

StructuralConcrete

Solid slabs (cast in place or precast)Cast in place waffle slabsCast in place flat slabsPrecast joist systemPrecast hollow core slabsPrecast beams with concrete toppingPost-tensioned slabs

Steel Composite steel deck with concrete slabTimber Rammed earth with ballast and concrete or plaster finishing

Wood planks or beams with ballast and concrete or plaster finishingThatched roof supported on wood purlinsWood single roofWood planks or beams that support clay tiles XWood planks or beams that support slate, metal asbestos-cement or plasticcorrugated sheets or tilesWood plank, plywood or manufactured wood panels on joists supported bybeams or walls

Masonry Masonry and steel jack arch structure X

Additional Comments: Floor and roof structures are not considered as rigid diaphragms.

4.6 Typical Plan DimensionsLength: 25 - 25 metersWidth: 25 - 25 meters

4.7 Typical Number of Stories5

4.8 Typical Story Height3.5 meters

4.9 Typical Span4 meters

4.10 Typical Wall Density5% - 6%

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The ratio of total wall area/plan area (for each floor) in each principal direction is between 5% and 6%.

4.11 General Applicability of Answers to Questions in Section 4This description does not relate to a specific building.

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5 Evaluation of Seismic Performance and Seismic Vulnerability

5.1 Structural and Architectural Features: Seismic ResistanceStructural/ArchitecturalFeature

Statement True False N/A

Lateral load path The structure contains a complete load path for seismic force effects fromany horizontal direction that serves to transfer inertial forces form thebuilding to the foundation.

X

Buildingconfiguration

The building is regular with regards to both the plan and the elevation. X

Roof construction The roof diaphragm is considered to be rigid and it is expected that the roofstructure will maintain its integrity, i.e.. shape and form, during anearthquake of intensity expected in this area.

X

Floor construction The floor diaphragm(s) are considered to be rigid and it is expected that thefloor structure(s) will maintain its integrity, during an earthquake of intensityexpected in this area.

X

Foundationperformance

There is no evidence of excessive foundation movement (e.g. settlement)that would affect the integrity or performance of the structure in anearthquake.

X

Wall and framestructures-redundancy

The number of lines of walls or frames in each principal direction is greaterthan or equal to 2.

X

Wall proportions Height-to-thickness ratio of the shear walls at each floor level is: 1) Lessthan 25 (concrete walls); 2)Less than 30 (reinforced masonry walls); 3)Less than 13 (unreinforced masonry walls).

X

Foundation- wallconnection

Vertical load-bearing elements (columns, walls) are attached to thefoundations; concrete columns and walls are doweled into the foundation.

X

Wall-roofconnections

Exterior walls are anchored for out-of-plane seismic effects at eachdiaphragm level with metal anchors or straps.

X

Wall openings The total width of door and window openings in a wall is: 1) for brickmasonry construction in cement mortar: less than 1/2 of the distancebetween the adjacent cross walls; 2) for adobe masonry, stone masonryand brick masonry in mud mortar: less than 1/3 of the distance between theadjacent cross walls; 3) for precast concrete wall structures: less than 3/4 ofthe length of a perimeter wall.

X

Quality of buildingmaterials

Quality of building materials is considered to be adequate per requirementsof national codes and standards (an estimate).

X

Quality ofworkmanship

Quality of workmanship (based on visual inspection of few typical buildings)is considered to be good (per local construction standards).

X

Maintenance Buildings of this type are generally well maintained and there are no visiblesigns of deterioration of building elements (concrete, steel, timber).

X

Other In some cases, the use of these buildings is changed X

5.2 Seismic FeaturesStructural Element Seismic Deficiency Earthquake-Resilient Features Earthquake Damage PatternsWall - Poor mortar strength; - Walls not tied

together;- X-cracks, and total collapse in somecases; -Very low seismic resistance;

Roof and floors -Not monolithic; -Not rigid in-plane;

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5.3 Seismic Vulnerability RatingVulnerability

High (Very PoorSeismicPerformance)

Medium Low (ExcellentSeismicPerformace)

A B C D E FSeismic

Vulnerability Class0

0 - probable value< - lower bound> - upper bound

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6 Earthquake Damage Patterns

6.1 Past Earthquakes Reported To Affect This ConstructionYear Earthquake Epicenter Richter magnitude(M) Maximum Intensity (Indicate

Scale e.g. MMI, MSK)1980 El-Asnam 7.3 X (MMI)1989 Tipaza 6.2 VIII-IX (MSK)1994 Mascara 5.6 VIII (MSK)1999 Ain-Témouchent 5.8 VIII (MSK)

Additional Comments: Damage patterns vary from diagonal "X"-cracks to total wall collapse, and partial tototal collapse of the roofs/slabs. Earthquake, Total Number of Apartment Buildings (all types), Damagelevel (MSK scale) 1 2 3 4 5 1980 El-Asnam, 4844 439 1304 1351 863 887 1989 Tipaza, 4511 1480 1102223 426 1280 1994 Mascara, 1874 470 302 351 212 539 1999 Ain-Témouchent, 3398 1062 606 684 528518

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7 Building Materials and Construction Process

7.1 Description of Building MaterialsStructural Element Building Material Characteristic Strength Mix Proportions/ Dimensions CommentsWalls Field stone in

cement or mudmortar

massive stones used at thecorners and around theopenings

Data not available

Foundations Field stone incement or mudmortar

Roof and floors Vaulted bricks

7.2 Does the builder typically live in this construction type, or is it more typicallybuilt by developers or for speculation?This construction was practiced prior to 1950 by French contractors.

7.3 Construction ProcessOwners and contractors were involved in the construction of this type. The stone blocks were laid by handand the basic construction equipment was used.

7.4 Design/Construction ExpertiseThe level of expertise of all parties involved in the design and construction process was at the worldwidelevel of the XXth Century.

7.5 Building Codes and StandardsYes No

Is this construction type addressed by codes/standards? X

7.6 Role of Engineers and ArchitectsOnly architects had a role in the design/construction of this housing type

7.7 Building Permits and Development Control RulesYes No

Building permits are required XInformal construction XConstruction authorized per development control rules X

Additional Comments: Permits are now required for public buildings for the vertical extensions, structuralinterventions and for repair and strengthening.

7.8 Phasing of ConstructionYes No

Construction takes place over time (incrementally) XBuilding originally designed for its final constructed size X

7.9 Building MaintenanceWho typically maintains buildings of this type?BuilderOwner(s) XRenter(s) XNo oneOther

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7.10 Process for Building Code EnforcementNot applicable - building codes are not applicable to this construction practice.

7.11 Typical Problems Associated with this Type of ConstructionProblems with maintenance - most of this construction is in a lamentable state.

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8 Construction Economics

8.1 Unit Construction Cost (estimate)10 000-15 000 Algerian Dinars /m² (150-200 $US/m²)

8.2 Labor Requirements (estimate)Information not available.

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9 Insurance

9.1 Insurance IssuesYes No

Earthquake insurance for this construction type is typically available XInsurance premium discounts or higher coverages are available for seismicallystrengthened buildings or new buildings built to incorporate seismically resistantfeatures

X

9.2 If earthquake insurance is available, what does this insurance typicallycover/cost?

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10 Seismic Strengthening Technologies

10.1 Description of Seismic Strengthening ProvisionsType of intervention Structural Deficiency Description of seismic strengthening provision usedRetrofit(Strengthening)

Cracks in the stone masonry walls RC jacketingLack of integrity Installation of horizontal and vertical RC ties at exterior and steel ties

in the interior, see Figure 6A

10.2 Has seismic strengthening described in the above table been performed indesign practice, and if so, to what extent?These strengthning techniques were used to repair and strengthen the damaged buildings after theAlgerian earthquakes reported in this contribution. A guide for using these seismic strengtheningtechniques is available in Algeria ("Méthodes de Réparation et de Renforcement des Ouvrages" wasedited by CGS in 1992).

10.3 Was the work done as a mitigation effort on an undamaged building, or asrepair following earthquake damage?Vulnerability studies for strategic buildings were done in 1996 at Algiers City, and some buildings of thistype were strengthened as a result of the study.

10.4 Was the construction inspected in the same manner as new construction?No.

10.5 Who performed the construction: a contractor, or owner/user? Was anarchitect or engineer involved?Contractor performed the construction, and engineers were involved.

10.6 What has been the performance of retrofitted buildings of this type insubsequent earthquakes?Good.

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11 ReferencesBenedetti D., Benzoni G., Parisi M.A. (1988). Seismic Vulnerability and Risk Evaluation for Old UrbanNuclei, Earthquake Engineering and Structural Dynamics, Vol. 16, 183-201.

Boutin, C., E. Ibraim, et S. Hans (1999). Auscultation de Bâtiments Réels en Vue de l'Estimation de laVulnérabilité, Vème Colloque National PS "Génie Parasismique et Réponse Dynamique des Ouvrages",ENS 3- 3- Cachan, 1, 298-305.

C. Boutin, S. Hans, E. Ibraim (2000). Pour une approche expérimentale de la vulnérabilité sismique,Revue française de génie civil, vol 4 (6), pp. 682-714.

Coburn A.W., Spence R.J.S., Pomonis A. (1992). Factors Determining Casuality Levels in Earthquakes:Mortality Prediction in Building Collapse, 10th WCEE, Madrid, Spain.

Centre National de Recherche Appliquée en Génie Parasismique (2000), Règles ParasismiquesAlgériennes (RPA99), Alger, Algérie

Cochrane S.W., Schaad W.H. (1992). Assessment of Earthquake Vulnerability of Buildings, 10 WCEE,Madrid, Spain.

European Seismological Commission (1993). European Macroseismic Scale 1992, Grünthal G. Editor,Luxembourg.

Farsi M. N., Belazougui M. (1992). The Mont Chenoua (Algeria) earthquake of October 29th, 1989:Damage assessment and distribution, 10WCEE, Madrid, Spain.

Farsi M. N. (1996). Identification des Structures de Génie Civil à Partir de Leurs Réponses Vibratoires etVulnérabilité du Bâti Existant. Thèse de Doctorat, Observatoire de Grenoble, LGIT, Université JosephFourier.

Karnik V., Schenkova Z., Schenk V. (1984). Vulnerability and the MSK Scale, Engineering Geology, 20,161-168.

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12 ContributorsName Mohammed Farsi Farah Lazzali Yamina Ait-MézianeTitle Head of Department Researcher ResearcherAffiliation CGS CGS CGSAddress Kaddour Rahim St, BP 252,

HUSSEIN-DEY, AlgiersKaddour Rahim St, BP 252,HUSSEIN-DEY, Algiers

Kaddour Rahim St, BP 252,HUSSEIN-DEY

City AlgiersZipcode 16040 16040 16040Country Algeria Algeria AlgeriaPhone (213) 21 49 55 46 (213) 21 49 55 47/49 (213) 21 49 55 47/49Fax (213) 21 49 55 36 (213) 21 49 55 36 (213) 21 49 55 36Email mnfarsi@cgs-dz.org lazzali@cgs-dz.orgWebpage

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13 Figures

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FIGURE 1: Typical Building

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FIGURE 2: Perspective Drawing Showing Key Load-Bearing Elements

FIGURE 3A: Typical Building Plan

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FIGURE 3B: Typical Roof Plan

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FIGURE 4: Critical Structural Details-Wall-Roof Connection and Vaulted Brick Floor Structure

FIGURE 5A: Typical Earthquake Damage -Partial Roof Collapse (1999 Ain-Temouchent earthquake)

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FIGURE 5B: Typical Earthquake Damage- Collapsed Roof of a Masonry Building (1989 Tipazaearthquake)

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FIGURE 5C: Typical Earthquake Damage-Cracking in the Wall Corners

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FIGURE 6A: Seismic Strengthening Techniques - Provision of Horizontal and Vertical RC Ties at theExterior and Horizontal Steel Ties at the Interior

FIGURE 6B: Seismic Strengthening Techniques-An Example of a Strengthened Building with Verticaland Horizontal RC Ties at the First Floor Level

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FIGURE 6C: Seismic Strengthening Techniques - Construction of RC Ties

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