World Housing Encyclopedia Report

Country: Chile

Housing Type: Concrete shear wall buildings

Contributors:Ofelia MoroniCristian Gómez

Primary Reviewer:Sergio Alcocer

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........................................................................................ 2Socio-Economic Issues...................................................................................... 3Structural 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 CountryChile

1.3 Housing TypeConcrete shear wall buildings

1.4 SummaryThese buildings are characterized mainly withreinforced concrete shear walls that are builtalong the complete height and in both directions.Some of the walls may be perforated withopenings (coupled walls). The buildings aremultiple housing units, and are found in themajor urban areas in Chile. Stiffness and massdistribution is regular and most of them mayhave a symmetry axis in at least one direction ofthe plant. In general these buildings are quitestiff because they must resist a base shear of5-6.7% depending on the seismic zone and thestory drift must be equal or less than 0.002.Seismic performance is very good, strength andstiffness are controlled, torsional effects areminimal. May have one or two basement floors.Problems that may appear in the future are:reduction in the wall density, introduction of softfloor or torsional 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 X< 75 years< 100 years< 200 years> 200 years

Is this construction still being practiced? Yes NoX

1.6 Region(s) Where UsedThis type exists in all main cities of the country: Iquique, Antofagasta, Concepción, Temuco, Valparaíso,Viña del Mar and Santiago.

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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2 Architectural Features

2.1 OpeningsNot Applicable. In this country there is no standardization for any element: window, door, etc, so it is notpossible to provide an estimate of number or size of openings.

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 According to NCH433.of96 it must be at least 1.5 cmor 0.002 X total height of the building. In addition there are some dispositions about distance to neighborsite or free space for parking. So, individual buildings in a block may be separated up to 10 meters

2.3 Building ConfigurationRectangular

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

2.5 Means of EscapeModern buildings have pressurized stairs and the taller ones also have a helicopter landing strip on thetop.

2.6 Modification of BuildingsThe most popular may be infill balconies. The others may occur but rarely.

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3 Socio-Economic Issues

3.1 Patterns of OccupancyOne family occupies one housing unit.

3.2 Number of Housing Units in a Building70 units in each building.

Additional Comments: It is on average. 10 to 100 units may be in the building and 4 to 10 units in eachfloor.

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> 20 X XOther

Additional Comments: During the day the inhabitants may be one fourth of those that reside in the night.Each unit may have 4-8 inhabitants.

3.4 Number of Bathrooms or Latrines per Housing UnitNumber of Bathrooms: 1Number of Latrines: 0

Additional Comments: Single bathroom in one or two bedroom apartments. Larger apartments may have2 or 3 bathrooms.

3.5 Economic Level of InhabitantsEconomic Status House Price/Annual Income

(Ratio)Very poor /Poor /Middle Class X 50000/20000Rich X 250000/120000

Additional Comments: The prices are expressed in US$. In Chile the income is very non-uniformlydistributed, and the rich constitute less than 10% of the population. Middle class apartments may cost1500-4000 UF (US$37.500-100.000), and the annual income for a family of 4 people may be US$ 20.000Larger apartments may cost 7000-10.000 UF (US$ 175.000-250.000), and the annual income for a familyof 4 people may be US$ 120.000

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 / mortages XInvestment pools XCombination (explain)Government-owned housingOther

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3.7 OwnershipType of Ownership/OccupancyRent XOwn outrightOwn with Debt (mortgage or other) XUnits owned individually (condominium) XOwned by group or poolLong-term leaseOther

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4 Structural Features

4.1 Lateral Load-Resisting SystemShear walls provide adequate strength and stiffness to control lateral displacements.In some cases, lintel beams couple some walls, thus resulting in the reduced lateral displacements. Ifdesigned and detailed properly, those coupling beams dissipate energy when subjected to severeearthquakes and are easily repaired after an earthquake.

4.2 Gravity Load-Bearing StructureShear walls act as lateral as well as gravity load-bearing elements. Beams and slabs carry floor loads.

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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)

2 Massive stone masonry (in lime or cement mortar)Earthen 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-situ X22 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 footingRubble stone (fieldstone) isolated footingRubble stone (fieldstone) strip footingReinforced concrete isolated footingReinforced concrete strip footing XMat foundation XNo foundation

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

Other

Additional Comments: Strip footings are used in firm soil for middle height buildings (6-10 stories), but insofter soils or when there are basement for parking mat footings are used.

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

Masonry VaultedComposite masonry and concrete joist

StructuralConcrete

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

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 tiles

X

Wood plank, plywood or manufactured wood panels on joists supported bybeams or walls

Other

Additional Comments: The floors and the roof are considered rigid in seismic analysis. Post-tensionedslab are used less often than cast in place, but there are some buildings designed by important engineersfirm that do have it. VSL has an office in Chile and they are trying to introduce it.

4.6 Typical Plan DimensionsLength: 20 - 20 metersWidth: 20 - 20 metersAdditional Comments: Average area are: 487 m²

4.7 Typical Number of Stories4 - 30In recent years the average is 13 stories.

4.8 Typical Story Height

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2.7 meters

Additional Comments: Variation of story Height is 2.6 m - 2.8 m.

4.9 Typical Span6 meters

Additional Comments: It is on average. Usually span is limited to 4 m - 8 m.

4.10 Typical Wall DensityTotal wall area/plan area (for each floor)For the 95% of the buildings, the wall density is greater than 1.5% in each direction, average value =2.8%Figure 5A shows the variation on time of the wall density which has remain almost constant.

4.11 General Applicability of Answers to Questions in Section 4Reinforced concrete shear wall buildings represent 70-80% of the total buildings (over 5 floor) constructedin Chile. Wall density, story floors, typical span correspond to average values.

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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

5.2 Seismic FeaturesStructural Element Seismic Deficiency Earthquake-Resilient Features Earthquake Damage PatternsWall None High wall density, regular on height lead

to story drift under control, negligibleP-D effect, less sensible tonon-structural elements, plasticityuniformly distributed. In case of damageare easily repaired

Small shear cracks

Frame (columns,beams)Roof and floors Some damage has been reported in

slab with openings, i.e. between stairsand elevators, when there are not lintelsand the slab works as a couplingelement and no special reinforcementshave been provided.

Shear crack in lintels

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5.3 Seismic Vulnerability RatingVulnerability

High (Very PoorSeismicPerformance)

Medium Low (ExcellentSeismicPerformace)

A B C D E FSeismic

Vulnerability Class< 0

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)1985 Llolleo 7.8 VIII1960 Valdivia, X Region 9.5 XI-MMI

Additional Comments: Not many buildings existed in southern Chile in 1960, the only damage cited in theliterature is the hospital in Valdivia. In 1985 only one building partially collapsed in Santiago (VillaOlímpica) and one had to be demolished in Viña del Mar (El Faro de Reñaca). Important damagesoccurred in 5 stories buildings (Canal Beagle) that were located on the top of a hill in Viña del Mar whereimportant acceleration amplification have been measured. A few others buildings in Viña del Mar hadsome walls damaged and some others had non-structural damage. FIGURE 6 shows the EdificioAcapulco building in Viña del Mar, after the 1985 Llolleo earthquake. This building suffered some damagein lintels during 1971 earthquake, that was not properly repaired, so during 1985 new cracks appeared.

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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 Reinforced

Concrete H25-H35steel

1.5-4.0/25-35/1.5-2.0A63-42H or A44-28H

3:1:0.5 6:1:0.5 st/f'c/shear strength(1) sand: cement:water (2)

FoundationsFrameRoof and floors Reinforced

concreteH25-H30

Notes:1. The values that appear in column characteristic strength are : Tension/compression/shear strength.The Chilean denomination is H25- H35. Denomination for concrete: H35 (10) 20/10 means a concretewith a 28-days cubic compressive strength of 35 MPa, with 10% of defective fraction, nominal size ofcoarse aggregate not larger than 20 mm and with slump of 10 cm. Steel A63-42H means maximumtension strength of 630 MPa and yield strength of 420 MPa.2. Mix proportions are: sand: cement: water.

7.2 Does the builder typically live in this construction type, or is it more typicallybuilt by developers or for speculation?It is built by developers and sold to the people who will live in this construction type.

7.3 Construction ProcessThe owner of the land and a construction firm will hire an architectural office and structural engineer todesign the building. They will use modern equipment, crane, premix concrete, etc.

7.4 Design/Construction ExpertiseThe structural engineer will have 6 years of studies and more than 3-5 years of experience. Theconstruction engineer may have 6 years of studies and less experience than the structural engineer.There is no compulsory inspection during the construction and no peer revision of the structural project.The designer may visit the construction site one or two times during the construction

7.5 Building Codes and StandardsYes No

Is this construction type addressed by codes/standards? X

Title of the code or standard: NCh433.of96 Seismic Design of BuildingsYear the first code/standard addressing this type of construction issued: Until 1993 the NCh433.of72 wasin force. The last two numbers indicates the year since the code is in force. Provisionally dispositions todesign this type of buildings existed since 1966.National building code, material codes and seismic codes/standards: NCh433.of96. In addition,ACI318-95 is used for design reinforced concrete elements, with some exceptions: the minimumcompressive strength is 16 MPa, confinements at wall end or diagonal bars in couple beam are rarelyused and a reduced reinforcement cover is allowed. The appendix of the NCh433.of96 states that "theshear wall design doesn't need to follow dispositions 21.6.6.1 to 21.6.6.4 of ACI 318-95.When was the most recent code/standard addressing this construction type issued? 1996

7.6 Role of Engineers and ArchitectsYes, of course they play a role as is explained in 7.3.

7.7 Building Permits and Development Control Rules

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

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

7.10 Process for Building Code EnforcementThe building design must follow the NCh433.of96 code, although no one verifies. In case of damage anarbitrage process may take place at the court of justice.

7.11 Typical Problems Associated with this Type of ConstructionThe main problems are associated with the construction process: construction joints badly done orexistence of honeycombs.

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8 Construction Economics

8.1 Unit Construction Cost (estimate)A unit construction may cost 15-35 UF/ m² (500-1200 US$/m²).

8.2 Labor Requirements (estimate)Nowadays the progress in construction is quite rapid, probably one or two floors per month.

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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

Additional Comments: Earthquake insurance is available as an additional to insurance against fire. In thiscase the premium cost is almost doubled

9.2 If earthquake insurance is available, what does this insurance typicallycover/cost?In case of damage, this insurance will cover repair work.

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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)

Lintels damage Rebuilt the lintel or fixed with epoxy.Shear cracks in walls The wall is thickened with a new mesh or confined element are added

at the extremes.

Additional Comments: This is not a common activity in Chile. FIGURES 7A and 7B show strengthening ofearthquake damaged building shown on FIGURE 6. Columns have been added to the extreme of onewall.

10.2 Has seismic strengthening described in the above table been performed indesign practice, and if so, to what extent?No

10.3 Was the work done as a mitigation effort on an undamaged building, or asrepair following earthquake damage?Only after an earthquake some buildings have been repaired, when some constructive deficienciesappeared. Edificio Acapulco in Viña del Mar, suffered some damage in lintels during 1971 earthquake,that were not properly repaired, so during 1985 new cracks appeared. FIGURES 6 and 7A show theAcapulco building after the 1985 earthquake and after repaired work was done.

10.4 Was the construction inspected in the same manner as new construction?Probably not.

10.5 Who performed the construction: a contractor, or owner/user? Was anarchitect or engineer involved?A contractor and an engineer were involved hired by the owner/user.

10.6 What has been the performance of retrofitted buildings of this type insubsequent earthquakes?No earthquakes have occurred in Central Chile since 1985.

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11 ReferencesDufflocq Julio, (1998), "Criterios tradicionales utilizados en Chile en el diseño de muros de hormigónarmado" , Civil Engineer Thesis, Universidad de Chile

Gomez Cristián, (2001) , "Caracterización de sistemas estructurales usados en las viviendas dehormigón armado y albañilería reforzada en Chile", Civil Engineer Thesis, Universidad de Chile.

Guzmán, M. (1998), "Caracterización de tipologías estructurales usadas en el diseño de edificios altos enChile", Civil Engineer Thesis, Universidad de Chile.

Kupfer, M., Lagos R., (1999), "Apuntes para el curso CI52G, Proyecto de Hormigón Armado", Depto deIng. Civil, Universidad de Chile.

Moroni, M., Guzmán M., (1998) "Evolución de las Tipologías Estructurales usadas en Chile en EdificiosAltos", Boletín de Información Tecnológica, Año 5, Nº 12, pp 25-27.

Sarrazin, M. (1992), "History of Chilean Seismic Regulations", Bulletin IISEE, Vol 26.

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12 ContributorsName Ofelia Moroni Cristian GómezTitle Civil Engineer / Assistant Professor Civil Engineer / Research AssistantAffiliation University of Chile University of ChileAddress Casilla 228/3 Casilla 228/3City SantiagoZipcodeCountry Chile ChilePhone 562-678-4372 562-7441153Fax 562-689-2833 562-6892833Email mmoroni@cec.uchile.cl crgomez@cec.uchile.clWebpage

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13 Figures

FIGURE 1: Typical Building

FIGURE 2: Key Load bearing Elements

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FIGURE 3A: Plan of a Typical Building

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FIGURE 3B: Plan of a Typical Building

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FIGURE 4: Typical wall section, slab and beam

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FIGURE 5A: Wall density # A Key Seismic Feature

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FIGURE 5B: Wall density

FIGURE 6: Edificio Acapulco, Viña del Mar, 1985 Llolleo Earthquake

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FIGURE 7A: Seismic strengthening (Edificio Acapulco building damaged in the 1985 Llolleo eq.). Acolumn has been added to the exterior of a wall.

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FIGURE 7B: Seismic strengthening (Edificio Acapulco building). The exterior wall has been thickenedwith a new steel mesh.

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