Report #: 67

Report Date:

Country: VENEZUELA

Housing Type:

Housing Sub-Type:

Author(s): Argimiro Castillo Gandica, Francisco Lopez Almansa

Last Updated:

Regions Where Found: Buildings of this construction type can be found in Merida, Tachira and Trujillo, comprising the Andean states in Venezuela. This housing covers almost 40% of the total building stock in the city of M#rida. This type of housing construction is commonly found in urban areas.

Summary: This is an urban housing construction type found in the Andean states of Venezuela. In some cities e.g. Merida this construction accounts for 40% of the total building stock. Typical buildings of this type are two to three stories high.Typically, there are two or three bays in the longitudinal direction (spaced at 3 to 4 m) and four or five bays in the transverse direction (4 to 5 m apart). The main load-bearing system consists of reinforced concrete frame (columns and beams) with hollow clay tile masonry infill walls. Roof structure consists of lightweight roofing (zinc and/or acclimatized galvanized sheets) supported by I-shaped steel beams. The roof level of a building is used as a terrace with an one meter high masonry parapet that serves as a guardrail on the slab perimeter. This is a nonengineered construction i.e. these buildings are constructed by the owners. Due to the lack of adequate detailing in the longitudinal and transverse steel reinforcement bars, beam-column connections are inadequate and do not provide the continuity required for adequate seismic performance.

Length of time practiced: 25-60 years

Still Practiced: Yes

In practice as of:

Building Occupancy: Other

Typical number of stories: 2-3

Terrain-Flat: Typically

Terrain-Sloped: Off

Comments:

0.03 up to 0.05 meters typical separation distance between buildings

Plan Shape: Rectangular, solid

Additional comments on plan shape: Typical shape of a building plan for this housing type is rectangular, with proportions (width/length) ranging from 1/3 to 1/4.

Typical plan length (meters): 12-15

Typical plan width (meters): 3-5

Typical story height (meters): 2.8

Type of Structural System: Structural Concrete: Moment Resisting Frame: Designed for gravity loads only, with URM infill walls

Additional comments on structural system: The vertical load-resisting system is reinforced concrete moment resisting frame.

Reinforced concrete frames generally provide acceptable lateral load resistance, depending upon quality adequacy and upon the detailing of structural elements (columns and beams). In this case, several of the items are inadequate: the detailing of the reinforced concrete columns and beams, e.g., excessive stirrup spacing (same distance of element's section base); the tie anchorage (angle of anchorage is 90# instead of 135# as recommended in seismic codes); and the location of the laps in longitudinal reinforcement for columns (laps are provided at the bottom of columns in successive stories). The roof structure consists of lightweight roofing (zinc and/or acclimatized galvanized sheets) supported by I-shaped steel beams.

Gravity load-bearing & lateral load-resisting systems: See Figure 2.

Typical wall densities in direction 1: >20%

Typical wall densities in direction 2: >20%

Additional comments on typical wall densities: Two possibilities regarding wall density exist depending on position of the building in the block; there are Inner and Corner buildings Wall Density respectively.

Wall density for Inner Buildings:

Floor Number Total Wall Area longitudinal direction Total Wall Area transverse direction Typical Wall Density long. dir. Typical Wall Dens. trans. dir 1 114.24 56.96 1.28 0.64 2 119 64.72 1.33 0.62

Wall Density for Corner Buildings:

Floor Number Total Wall Area longitudinal direction Total Wall Area transverse direction Typical Wall Density long. dir. Typical Wall Dens. trans. dir 1 108.48 56.96 1.21 0.64 2 114.2 64.72 1.28 0.72

Wall Openings: Usually, openings are produced at the front and the back of the building, having door and window openings on the first level and two windows in successive levels. The openings range from 5 to 10% of the overall wall area.

Is it typical for buildings of this type to have common walls with adjacent buildings?: No

Modifications of buildings: Modifications respond to vertical growth, balconies, new windows, staircases for separate access to upper levels. Usually, when a new level is constructed, an external staircase facing the facade is built to permit separate access to upper levels. Windows and balconies are located in the facade and back walls. In lateral walls, windows are built when possible due to lateral proximity between buildings.

Type of Foundation: Shallow Foundation: Reinforced concrete isolated footing

Additional comments on foundation: See Figure 2

Type of Floor System: Other floor system

Additional comments on floor system: Composite hollow clay tiles and steel joists;

Floors may be considered as rigid diaphragms. Special inspection must be performed on floor connection with beams, to guarantee transmission of lateral loads.

Type of Roof System: Roof system, other

Additional comments on roof system: Steel joists and metal sheathing (zinc/aluminum);

Roof may not be considered as a rigid diaphragm, due to the reduced sections (at most IPN 80), the low connectivity between joists and the lack of connection with the rest of the structure (absence of a collar beam on top of walls in roof level).

Additional comments section 2: When separated from adjacent buildings, the typical distance from a neighboring building is 0.03-0.05 meters.

Who is involved with the design process?: Other

Roles of those involved in the design process: As an auto-constructed type, construction professionals (Architects and/or Engineers) are not involved in the design or in the construction process. Professional intervention is unaffordable for the inhabitants of these settlements.

Expertise of those involved in the design process: No professionals (Architects and/or Engineers) are involved in the design or construction process.

Who typically builds this construction type?: Other

Roles of those involved in the building process: The builder lives in this construction type.

Expertise of those involved in building process: Builders mainly count on some experience in building construction. Semi-skilled level seems to suit adequately the expertise of the builders.

Construction process and phasing: Construction process is performed in vertical phases, i.e. a level at a time. Common practice is to build foundations and columns for the first level, leaving columns longitudinal steel bars to be spliced. After concrete curing, the walls are built. Beams are built over walls, and afterwards the first slab (hollow clay tiles with steel joists) is constructed. The owner typically builds with no more than two helpers. The entire process is performed at the building site with ordinary building tools; no special machinery or equipment is used. The construction of this type of housing takes place incrementally over time. Typically, the building is originally not designed for its final constructed size. Construction phasing depends on the availability of money. These resources are obtained from savings and from the cooperation of other family members. Usually the inhabitants collaborate in the building process.

Construction issues

Is this construction type address by codes/standards?: No

Applicable codes or standards:

Process for building code enforcement: Official authorities have no process or strategy for building code enforcement.

Are building permits required?: No

Is this typically informal construction?: Yes

Is this construction typically authorized as per development control rules?: No

Additional comments on building permits and development control rules:

Typical problems associated with this type of construction: Inexistent seismic detailing features in reinforced concrete works. Connections between floors and structural frames do not guarantee lateral force transmission and may induce displacement of slabs with respect to the frames generating damage to columns. Parapets in uppermost levels represent a dangerous collapsible feature. The absence of collar beams and horizontal reinforcement in uppermost walls may produce out-of-plane inertial loads. Gap between adjacent buildings (not greater than 10.0 cm.) creates risk of pounding effect.

Who typically maintains buildings of this type?: Owner(s)

Additional comments on maintenance and building condition:

Unit construction cost: Unit construction cost: 87000 Bs. (120 US$) per square meter of built-up area.

Labor requirements: For each level, with a three worker team, 45 to 55 days are required to complete the construction.

Additional comments section 3:

Damage patterns observed in past earthquakes for this construction type: See Figure 6.

Additional comments on earthquake damage patterns: Wall: Cracks in walls, parts of walls collapse, great cracks in windows and around doors.

Frame: Shear failure in connections between columns and beams, and between columns and foundations, excessive lateral displacements, cracking and spalling concrete columns due to inadequate confinement.

Roof/Floors: Roof- great movements may be generated in roofs, total dismantlement and consequent collapse may occur. Floors- great movements may inflict damage in confinement and walls.

Other: Column failure at level where slabs of neighboring construction pounds.

The main reference publication used in developing the statements used in this table is FEMA 310 Handbook for the Seismic Evaluation of Buildings-A Pre-standard, Federal Emergency Management Agency, Washington, D.C., 1998.

The total width of door and window openings in a wall is: For brick masonry construction in cement mortar : less than ½ of the distance between the adjacent cross walls; For adobe masonry, stone masonry and brick masonry in mud mortar: less than 1/3 of the distance between the adjacent cross walls; For precast concrete wall structures: less than 3/4 of the length of a perimeter wall.

Vertical irregularities typically found in this construction type: Other

Horizontal irregularities typically found in this construction type: Other

Seismic deficiency in walls: No reinforcement is visible throughout the walls (neither horizontal nor vertical). Poor quality mortar and cracked masonry units.

Seismic deficiency in frames: -Stirrup and tie spacing is not compliant to recommendations of less than d/2 spacing in beams and d/4 in columns, neither in beams nor in columns. Spacing is regular throughout all members and is usually d or more. Anchorage hooks into member cores are g

Seismic deficiency in roof and floors: Roof may not be considered as a rigid diaphragm due to the lack of adequate connectivity within its elements and with the walls (absence of a collar beam on top of walls at this level).Connections between floor and frames must be inspected to guarantee adequate linking and load transmission.

Other seismic deficiencies: Risk of pounding effect. Not enough gap between adjacent buildings, distance is not greater than 10.0 cm.

For information about how seismic vulnerability ratings were selected see the Seismic Vulnerability Guidelines

Additional comments section 5: See Figures 4 and 5.

Additional comments on seismic strengthening provisions: For the moment, seismic strengthening provisions have not been performed, either in design or in retrofitting.

Has seismic strengthening described in the above table been performed?: No

“Basic Concepts of Seismic Codes, Vol.1, Part I, Non- Engineered Construction”, IAEE, 1980.

#Evaluaci#n preliminar del sismo de Car#aco del 9 de Julio de 1997, Estado Sucre, Venezuela (Versi#n Revisada)#, FUNVISIS (Fundaci#n Venezolana de Investigaciones Sismol#gicas), Caracas, Octubre 1997.

FEMA 310 Handbook for the Seismic Evaluation of Buildings: A Pre-standard Federal Emergency Management Agency, Washington, D.C. 1998