World Housing Encyclopedia Report

Transcription

1 World Housing Encyclopedia Report Country: Algeria Housing Type: Stone masonry apartment building Contributors: Mohammed Farsi Farah Lazzali Yamina Ait-Méziane Primary Reviewer: Marjana Lutman Created on: 6/5/2002 Last Modified: 6/17/2003 This encyclopedia contains information contributed by various earthquake engineering professionals around 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 Engineering Research Institute, the International Association for Earthquake Engineering, the Engineering Information Foundation, John A. Martin & Associates, Inc. or the participants' organizations.

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

3 1 General Information 1.1 Country Algeria 1.3 Housing Type Stone masonry apartment building 1.4 Summary This is a typical residential construction found in most Algerian urban centers, and it constitutes 40 to 50% of the total urban housing stock. This construction, mostly built before 1950s by French contractors, is no longer practiced. Buildings of this type are typically 4 to 6 stories high. The slabs are wooden structures or shallow arches supported by steel beams (jack arch system). Stone masonry walls, usually 400 to 600 mm thick, have adequate gravity load-bearing capacity, however their lateral load resistance is very low. As a result, these buildings are considered to be highly vulnerable to seismic effects. FIGURE 1: Typical Building 1.5 Typical Period of Practice for Buildings of This Construction Type How long has this construction been practiced < 25 years < 50 years < 75 years < 100 years < 200 years > 200 years Is this construction still being practiced? Yes No Additional Comments: This construction was practiced prior to 1950 by French contractors. 1.6 Region(s) Where Used These stone masonry buildings exist throughout the northern Algeria. In particular, the multi-story buildings exist mainly in the major cities e.g. Algiers, Oran, Constantine, Annaba, etc. This construction type may constitute 40 to 50% of the urban housing stock. 1.7 Urban vs. Rural Construction Where is this construction commonly found? In urban areas In rural areas In suburban areas Both in rural and urban areas Page 1

4 Additional Comments: This type of construction is found in the older urban districts. Page 2

5 2 Architectural Features 2.1 Openings The 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 Siting Is this type of construction typically found on flat terrain? Is this type of construction typically found on sloped terrain? (hilly areas) Is it typical for buildings of this type to have common walls with adjacent buildings? Yes No The typical separation distance between buildings is 5 meters 2.3 Building Configuration The building plan for this housing type can be of different forms: rectangular, L-shaped, U-shaped, etc. 2.4 Building Function What is the main function for buildings of this type? Single family house Multiple housing units Mixed use (commercial ground floor, residential above) Other (explain below) Additional Comments: Buildings of this type are also used as offices and hospitals. 2.5 Means of Escape Majority of these buildings have only one exit, and one main staircase inside the building in the case of multi-story buildings. 2.6 Modification of Buildings Modifications are often undertaken by the residents without any professional assistance provided by engineers. The modifications include the demolition of interior walls, opening commercial areas, and the vertical extensions. Page 3

6 3 Socio-Economic Issues 3.1 Patterns of Occupancy In Algeria there is a serious housing crisis. On an average, there are two families occupying the same housing unit: the parents and a son's or daughter's family. 3.2 Number of Housing Units in a Building units in each building. 3.3 Average Number of Inhabitants in a Building How many inhabitants reside in a typical building of this construction type? <5 5 to > 20 Other During the day / business hours During the evening / night Additional Comments: In most cases the women in the families are not working and stay at home during the day. 3.4 Number of Bathrooms or Latrines per Housing Unit Number of Bathrooms: 1 Number of Latrines: Economic Level of Inhabitants Economic Status Very poor Poor Middle Class Rich House Price/Annual Income (Ratio) / 10/1 / / 3.6 Typical Sources of Financing What is the typical source of financing for buildings of this type? Owner Financed Personal Savings Informal Network: friends and relatives Small lending institutions/microfinance institutions Commercial banks / mortages Investment pools Combination (explain) Government-owned housing Other 3.7 Ownership Type of Ownership/Occupancy Rent Own outright Own with Debt (mortgage or other) Units owned individually (condominium) Owned by group or pool Long-term lease Other Page 4

7 4 Structural Features 4.1 Lateral Load-Resisting System The lateral load-resisting system consists of the stone masonry walls built in longitudinal and cross directions. Wall thickness varies from 400 to 600 mm. Field masonry has been used mainly, massive stones only at the corners and around the openings. Low-strength mortar (either cement/sand or mud mortar) 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 confined with reinforced concrete ties in vertical and horizontal direction and with RC slabs used as floor and roof structures. The maximum building height allowed by the Code depends on the seismic zone (17 m, 14 m and 11 m, for seismic zones I, II and III, respectively). 4.2 Gravity Load-Bearing Structure Stone masonry walls are the principal elements of the gravity load-bearing structure. Page 5

8 4.3 Type of Structural System Material Masonry Type of Load-Bearing Structure Stone masonry walls # Unreinforced brick 7 masonry walls 8 Earthen walls 9 Confined masonry 10 Concrete block masonry walls Concrete Steel Timber Various Moment resisting 14 frame Shear wall structure Moment resisting 23 frame Braced frame Load-bearing 28 timber frame Seismic protection 34 systems Other 35 Subtypes Rubble stone (field stone) in mud/lime mortar or without mortar (usually with timber roof) Massive stone masonry (in lime or cement mortar) Mud walls Mud walls with horizontal wood elements Adobe block or brick walls Rammed earth/pise construction Unreinforced brick masonry in mud or lime mortar Unreinforced brick masonry in mud or lime mortar with vertical posts Unreinforced brick masonry in cement or lime mortar (various floor/roof systems) Confined brick/block masonry with concrete posts/tie columns and beams Unreinforced in lime or cement mortar (various floor/roof systems) Reinforced in cement mortar (various floor/roof systems) Large concrete block walls with concrete floors and roofs Designed for gravity loads only (predating seismic codes i.e. no seismic features) Designed with seismic features (various ages) Frame with unreinforced masonry infill walls Flat slab structure Precast frame structure Frame with concrete shear walls-dual system Precast prestressed frame with shear walls Walls cast in-situ Precast wall panel structure With brick masonry partitions With cast in-situ concrete walls With lightweight partitions Concentric Eccentric Thatch Post and beam frame Walls with bamboo/reed mesh and post (wattle and daub) Wooden frame (with or without infill) Stud wall frame with plywood/gypsum board sheathing Wooden panel or log construction Building protected with base isolation devices or seismic dampers Page 6

9 4.4 Type of Foundation Type Description Shallow Foundation Wall or column embedded in soil, without footing Rubble stone (fieldstone) isolated footing Rubble stone (fieldstone) strip footing Reinforced concrete isolated footing Reinforced concrete strip footing Mat foundation No foundation Deep Foundation Reinforced concrete bearing piles Reinforced concrete skin friction piles Steel bearing piles Wood piles Steel skin friction piles Cast in place concrete piers Caissons Other 4.5 Type of Floor/Roof System Material Masonry Structural Concrete Steel Timber Masonry Description of floor/roof system Vaulted Composite masonry and concrete joist Solid slabs (cast in place or precast) Cast in place waffle slabs Cast in place flat slabs Precast joist system Precast hollow core slabs Precast beams with concrete topping Post-tensioned slabs Composite steel deck with concrete slab Rammed earth with ballast and concrete or plaster finishing Wood planks or beams with ballast and concrete or plaster finishing Thatched roof supported on wood purlins Wood single roof Wood planks or beams that support clay tiles Wood planks or beams that support slate, metal asbestos-cement or plastic corrugated sheets or tiles Wood plank, plywood or manufactured wood panels on joists supported by beams or walls Masonry and steel jack arch structure Floor Roof Additional Comments: Floor and roof structures are not considered as rigid diaphragms. 4.6 Typical Plan Dimensions Length: meters Width: meters 4.7 Typical Number of Stories Typical Story Height 3.5 meters 4.9 Typical Span 4 meters 4.10 Typical Wall Density 5% - 6% Page 7

10 The ratio of total wall area/plan area (for each floor) in each principal direction is between 5% and 6% General Applicability of Answers to Questions in Section 4 This description does not relate to a specific building. Page 8

11 5 Evaluation of Seismic Performance and Seismic Vulnerability 5.1 Structural and Architectural Features: Seismic Resistance Structural/ Architectural Feature Lateral load path Building configuration Roof construction Floor construction Foundation performance Wall and frame structuresredundancy Wall proportions Foundation- wall connection Wall-roof connections Wall openings Quality of building materials Quality of workmanship Maintenance Other Statement True The structure contains a complete load path for seismic force effects from any horizontal direction that serves to transfer inertial forces form the building to the foundation. The building is regular with regards to both the plan and the elevation. The roof diaphragm is considered to be rigid and it is expected that the roof structure will maintain its integrity, i.e.. shape and form, during an earthquake of intensity expected in this area. The floor diaphragm(s) are considered to be rigid and it is expected that the floor structure(s) will maintain its integrity, during an earthquake of intensity expected in this area. There is no evidence of excessive foundation movement (e.g. settlement) that would affect the integrity or performance of the structure in an earthquake. The number of lines of walls or frames in each principal direction is greater than or equal to 2. Height-to-thickness ratio of the shear walls at each floor level is: 1) Less than 25 (concrete walls); 2)Less than 30 (reinforced masonry walls); 3) Less than 13 (unreinforced masonry walls). Vertical load-bearing elements (columns, walls) are attached to the foundations; concrete columns and walls are doweled into the foundation. Exterior walls are anchored for out-of-plane seismic effects at each diaphragm level with metal anchors or straps. The total width of door and window openings in a wall is: 1) for brick masonry construction in cement mortar: less than 1/2 of the distance between the adjacent cross walls; 2) for adobe masonry, stone masonry and brick masonry in mud mortar: less than 1/3 of the distance between the adjacent cross walls; 3) for precast concrete wall structures: less than 3/4 of the length of a perimeter wall. Quality of building materials is considered to be adequate per requirements of national codes and standards (an estimate). Quality of workmanship (based on visual inspection of few typical buildings) is considered to be good (per local construction standards). Buildings of this type are generally well maintained and there are no visible signs of deterioration of building elements (concrete, steel, timber). In some cases, the use of these buildings is changed False N/A 5.2 Seismic Features Structural Element Seismic Deficiency Wall - Poor mortar strength; - Walls not tied together; Roof and floors -Not monolithic; -Not rigid in-plane; Earthquake-Resilient Features Earthquake Damage Patterns - -cracks, and total collapse in some cases; -Very low seismic resistance; Page 9

12 5.3 Seismic Vulnerability Rating Seismic Vulnerability Class High (Very Poor Seismic Performance) A 0 Vulnerability Medium B C D E Low (Excellent Seismic Performace) F 0 - probable value < - lower bound > - upper bound Page 10

13 6 Earthquake Damage Patterns 6.1 Past Earthquakes Reported To Affect This Construction Year Earthquake Epicenter Richter magnitude(m) El-Asnam Tipaza Mascara Ain-Témouchent Maximum Intensity (Indicate Scale e.g. MMI, MSK) (MMI) VIII-I (MSK) VIII (MSK) VIII (MSK) Additional Comments: Damage patterns vary from diagonal ""-cracks to total wall collapse, and partial to total collapse of the roofs/slabs. Earthquake, Total Number of Apartment Buildings (all types), Damage level (MSK scale) El-Asnam, Tipaza, Mascara, Ain-Témouchent, Page 11

14 7 Building Materials and Construction Process 7.1 Description of Building Materials Structural Element Building Material Walls Field stone in cement or mud mortar Foundations Field stone in cement or mud mortar Roof and floors Vaulted bricks Characteristic Strength massive stones used at the corners and around the openings Mix Proportions/ Dimensions Comments Data not available 7.2 Does the builder typically live in this construction type, or is it more typically built by developers or for speculation? This construction was practiced prior to 1950 by French contractors. 7.3 Construction Process Owners and contractors were involved in the construction of this type. The stone blocks were laid by hand and the basic construction equipment was used. 7.4 Design/Construction Expertise The level of expertise of all parties involved in the design and construction process was at the worldwide level of the th Century. 7.5 Building Codes and Standards Yes Is this construction type addressed by codes/standards? No 7.6 Role of Engineers and Architects Only architects had a role in the design/construction of this housing type 7.7 Building Permits and Development Control Rules Yes Building permits are required Informal construction Construction authorized per development control rules No Additional Comments: Permits are now required for public buildings for the vertical extensions, structural interventions and for repair and strengthening. 7.8 Phasing of Construction Yes Construction takes place over time (incrementally) Building originally designed for its final constructed size No 7.9 Building Maintenance Who typically maintains buildings of this type? Builder Owner(s) Renter(s) No one Other Page 12

15 7.10 Process for Building Code Enforcement Not applicable - building codes are not applicable to this construction practice Typical Problems Associated with this Type of Construction Problems with maintenance - most of this construction is in a lamentable state. Page 13

16 8 Construction Economics 8.1 Unit Construction Cost (estimate) Algerian Dinars /m² ( $US/m²) 8.2 Labor Requirements (estimate) Information not available. Page 14

17 9 Insurance 9.1 Insurance Issues Yes Earthquake insurance for this construction type is typically available Insurance premium discounts or higher coverages are available for seismically strengthened buildings or new buildings built to incorporate seismically resistant features No 9.2 If earthquake insurance is available, what does this insurance typically cover/cost? Page 15

18 10 Seismic Strengthening Technologies 10.1 Description of Seismic Strengthening Provisions Type of intervention Structural Deficiency Retrofit Cracks in the stone masonry walls (Strengthening) Lack of integrity Description of seismic strengthening provision used RC jacketing 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 in design practice, and if so, to what extent? These strengthning techniques were used to repair and strengthen the damaged buildings after the Algerian earthquakes reported in this contribution. A guide for using these seismic strengthening techniques is available in Algeria ("Méthodes de Réparation et de Renforcement des Ouvrages" was edited by CGS in 1992) Was the work done as a mitigation effort on an undamaged building, or as repair following earthquake damage? Vulnerability studies for strategic buildings were done in 1996 at Algiers City, and some buildings of this type were strengthened as a result of the study Was the construction inspected in the same manner as new construction? No Who performed the construction: a contractor, or owner/user? Was an architect or engineer involved? Contractor performed the construction, and engineers were involved What has been the performance of retrofitted buildings of this type in subsequent earthquakes? Good. Page 16

19 11 References Benedetti D., Benzoni G., Parisi M.A. (1988). Seismic Vulnerability and Risk Evaluation for Old Urban Nuclei, Earthquake Engineering and Structural Dynamics, Vol. 16, Boutin, C., E. Ibraim, et S. Hans (1999). Auscultation de Bâtiments Réels en Vue de l'estimation de la Vulnérabilité, Vème Colloque National PS "Génie Parasismique et Réponse Dynamique des Ouvrages", ENS 3-3- Cachan, 1, C. Boutin, S. Hans, E. Ibraim (2000). Pour une approche expérimentale de la vulnérabilité sismique, Revue française de génie civil, vol 4 (6), pp 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 Parasismiques Algériennes (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 et Vulnérabilité du Bâti Existant. Thèse de Doctorat, Observatoire de Grenoble, LGIT, Université Joseph Fourier. Karnik V., Schenkova Z., Schenk V. (1984). Vulnerability and the MSK Scale, Engineering Geology, 20, Page 17

20 12 Contributors Name Title Affiliation Address City Zipcode Country Phone Fax Webpage Mohammed Farsi Head of Department CGS Kaddour Rahim St, BP 252, HUSSEIN-DEY, Algiers Farah Lazzali Researcher CGS Kaddour Rahim St, BP 252, HUSSEIN-DEY, Algiers Algeria (213) (213) Algeria (213) /49 (213) Yamina Ait-Méziane Researcher CGS Kaddour Rahim St, BP 252, HUSSEIN-DEY Algiers Algeria (213) /49 (213) Page 18

21 13 Figures Page 19

22 Page 20

23 FIGURE 1: Typical Building Page 21

24 Page 22

25 FIGURE 2: Perspective Drawing Showing Key Load-Bearing Elements FIGURE 3A: Typical Building Plan Page 23

26 FIGURE 3B: Typical Roof Plan Page 24

27 Page 25

28 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) Page 26

29 FIGURE 5B: Typical Earthquake Damage- Collapsed Roof of a Masonry Building (1989 Tipaza earthquake) Page 27

30 FIGURE 5C: Typical Earthquake Damage-Cracking in the Wall Corners Page 28

31 Page 29

32 FIGURE 6A: Seismic Strengthening Techniques - Provision of Horizontal and Vertical RC Ties at the Exterior and Horizontal Steel Ties at the Interior FIGURE 6B: Seismic Strengthening Techniques-An Example of a Strengthened Building with Vertical and Horizontal RC Ties at the First Floor Level Page 30

33 Page 31

34 FIGURE 6C: Seismic Strengthening Techniques - Construction of RC Ties Page 32