Confined masonry building, Peru

From World Housing Encyclopedia


1. General Information

Report: 50

Building Type: Confined masonry building

Country: Peru

Author(s): Cesar Loaiza, Marcial Blondet

Last Updated:

Regions Where Found: Buildings of this construction type can be found in all parts of Peru, particularly in the coastal region. This type of housing construction is commonly found in urban areas.

Summary: This multifamily housing construction type has been the most commonly used in the urban areas of Peru during the last 35 years. Confined masonry buildings consist of load-bearing unreinforced clay masonry walls confined by cast-in-place reinforced concrete tie columns and beams. Tie columns are cast after the construction of the masonry walls is complete and theyare connected to the tie beams. Confined masonry walls have limited shear strength and ductility; however, buildings of this type typically have a good seismic resistance.

Length of time practiced: 25-60 years

Still Practiced: Yes

In practice as of:

Building Occupancy: Mixed residential/commercial

Typical number of stories: 4-6

Terrain-Flat: Typically

Terrain-Sloped: 3

Comments: Average 6 units in each building; usually there are from 4 to 8 units in each building.


2. Features

Plan Shape: Rectangular, solid

Additional comments on plan shape:

Typical plan length (meters): 20

Typical plan width (meters): 12

Typical story height (meters): 2.7

Type of Structural System: Masonry: Confined Masonry: Concrete blocks, tie columns and beams

Additional comments on structural system: Lateral-load resisting system: The lateral load-resisting system is confined masonry wall system. Confined masonry walls give stiffness to the structure and control lateral drift. Tie columns and post beams prevent damage due to out-of-plane bending effects and improve wall ductility. Tie columns have the longitudinal reinforcement necessary to resist overturning moments. In some cases, reinforced concrete walls are required to avoid cracking of reinforced concrete elements. Gravity load-bearing system: Generally, the same system as described above. Floor and roof structures are composite structures, made of masonry units and concrete joists that transfer the gravity loads to the walls.

Gravity load-bearing & lateral load-resisting systems:

Typical wall densities in direction 1: 4-5%

Typical wall densities in direction 2: 4-5%

Additional comments on typical wall densities: The typical structural wall density is up to 5 %. Total wall area/plan area (for each floor) is 3-5%.

Wall Openings: A typical building has 3 to 4 windows (typically 1 to 2 m wide) in each in the longitudinal direction. In the transverse direction there may be one or two openings per facade.

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

Modifications of buildings: In some cases owners build additional interior walls as a part of the building extension (new rooms or bathrooms).

Type of Foundation: Shallow Foundation: Reinforced concrete strip footing

Additional comments on foundation: Usually the foundation is of plain (unreinforced) concrete unless the soil is clay or silt

Type of Floor System: Other floor system

Additional comments on floor system: Composite masonry and concrete joist; in the analysis, the floors are considered to be rigid diaphragms.

Type of Roof System: Roof system, other

Additional comments on roof system: Composite masonry and concrete joist.

Additional comments section 2: When separated from adjacent buildings, the typical distance from a neighboring building is 0.5-1.0 meters. Average plan area is 260 m.sq. Length varies from 15 to 30 m, and the width varies from 5 to 15 m. Story height varies from 2.5 meters to 2.8 meters.


3. Building Process

Description of Building Materials

Structural Element Building Material (s) Comment (s)
Wall/Frame Clay masonry Characteristic Strength: Compression strength: 12 -16 MPa Shear strength: 0.5 - 0.8 MPa Compression strength depends on the quality of bricks. Mix proportions/dimensions: 1:4 / 90 mm X 12 mm X 24 mm
Foundations Concrete Characteristic Strength: Compression strength: 14 - 18 MPa
Floors Concrete Steel Characteristic Strength: Compression strength: 21- 35 MPa Steel yield stress: 410 MPa
Roof Concrete Steel Characteristic Strength: Compression strength: 21- 35 MPa Steel yield stress: 410 MPa
Other Concrete Steel Characteristic Strength: Compression strength: 21-35 MPa Steel yield stress: 410 MPa

Design Process

Who is involved with the design process? EngineerArchitect

Roles of those involved in the design process: Engineers are in charge of the structural design and construction process. Architects are in charge of the architectural design and in some cases in charge of the construction process.

Expertise of those involved in the design process: Both the structural and the construction engineer should have 5 years of study and minimum work experience of 2 years.


Construction Process

Who typically builds this construction type? Other

Roles of those involved in the building process: Construction companies build the buildings of this type and sell them.

Expertise of those involved in building process: Both the structural and the construction engineer should have 5 years of study and minimum work experience of 2 years. Commonly, the construction process is inspected. The designer may visit the construction process once or twice during the construction.

Construction process and phasing: Masonry walls are built with serrated endings, then tie columns are cast against them. After that tie beams, lintels and floors are built simultaneously. The equipment commonly used is: concrete mixer, traveling crane, winch, trucks. Typically not built incrementally, buildings originally designed for final constructed size.

Construction issues: -Walls or opening end zones without confinement; -Poor quality of mortar; -Deficient construction joints; -Inadequate reinforcement detailing at the tie-column-to-tie beam joints.


Building Codes and Standards

Is this construction type address by codes/standards? Yes

Applicable codes or standards: Seismic Design Standards E-030 (1977) National Construction Standards, Masonry Standards E-070 (1998) The most recent code/standard addressing this construction type issued was 1998.

Process for building code enforcement: Municipal authorities approve the structural and architectural design for the building. It is common that the owner hires a private inspector to supervise the construction process.


Building Permits and Development Control Rules

Are building permits required? Yes

Is this typically informal construction? No

Is this construction typically authorized as per development control rules?: Yes

Additional comments on building permits and development control rules:


Building Maintenance and Condition

Typical problems associated with this type of construction:

Who typically maintains buildings of this type? BuilderOwner(s)Renter(s)

Additional comments on maintenance and building condition:


Construction Economics

Unit construction cost: Unit construction cost may vary from 200 to 300 US$/sq m.

Labor requirements: Depending on the technology used, the construction of a typical building may take 2-3 stories per month.

Additional comments section 3:


4. Socio-Economic Issues

Patterns of occupancy: Typically, one family occupies one housing unit. However, in low social classes, two or three families share one housing unit. Each building typically has 6 housing unit(s). Usually there are from 4 to 8 units in each building.

Number of inhabitants in a typical building of this construction type during the day: 5-10

Number of inhabitants in a typical building of this construction type during the evening/night: 10-20

Additional comments on number of inhabitants: Inhabitants during the day range from 5-10 to 10-20; inhabitants during the night range from 10-20 to more than 20.

Economic level of inhabitants: Low-income class (poor)Middle-income classHigh-income class (rich)

Additional comments on economic level of inhabitants: Ratio of housing unit price to annual income: 4:1 Economic Level: For Poor Class the Housing Unit Price is 15,000 and the Annual Income is 3,500. For Middle Class the Housing Unit Price is 40,000 and the Annual Income is 12,000. For Rich Class the Housing Unit Price is 100,000 and the Annual Income is 50,000.

Typical Source of Financing: Owner financedPersonal savingsSmall lending institutions/microfinance institutionsCommercial banks/mortgagesGovernment-owned housing

Additional comments on financing:

Type of Ownership: RentOwn outrightOwn with debt (mortgage or other)

Additional comments on ownership:

Is earthquake insurance for this construction type typically available?: Yes

What does earthquake insurance typically cover/cost: Despite earthquake insurance being available, people living in these buildings do not have enough money to pay it. Insurance covers all costs of damages or the construction of a new building.

Are premium discounts or higher coverages available for seismically strengthened buildings or new buildings built to incorporate seismically resistant features?: Yes

Additional comments on premium discounts:

Additional comments section 4: Despite earthquake insurance availability, people living in these buildings do not have enough money to pay for it.


5. Earthquakes

Past Earthquakes in the country which affected buildings of this type

Year Earthquake Epicenter Richter Magnitude Maximum Intensity
1970 Chimbote 7.8 VI (MMI)
1974 Lima 7.7 VIII (MMI)
1996 Nazca 7.3 VII (MMI)

Past Earthquakes

Damage patterns observed in past earthquakes for this construction type: Wall shear cracking that propagates through tie columns.

Additional comments on earthquake damage patterns:


Structural and Architectural Features for Seismic Resistance

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.

Structural/Architectural Feature Statement Seismic Resistance
Lateral load path The structure contains a complete load path for seismic force effects from any horizontal direction that serves to transfer inertial forces from the building to the foundation. TRUE
Building Configuration-Vertical The building is regular with regards to the elevation. (Specify in 5.4.1) TRUE
Building Configuration-Horizontal The building is regular with regards to the plan. (Specify in 5.4.2) TRUE
Roof Construction 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. N/A
Floor Construction 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. TRUE
Foundation Performance There is no evidence of excessive foundation movement (e.g. settlement) that would affect the integrity or performance of the structure in an earthquake. TRUE
Wall and Frame Structures-Redundancy The number of lines of walls or frames in each principal direction is greater than or equal to 2. TRUE
Wall Proportions Height-to-thickness ratio of the shear walls at each floor level is: Less than 25 (concrete walls); Less than 30 (reinforced masonry walls); Less than 13 (unreinforced masonry walls); TRUE
Foundation-Wall Connection Vertical load-bearing elements (columns, walls) are attached to the foundations; concrete columns and walls are doweled into the foundation. TRUE
Wall-Roof Connections Exterior walls are anchored for out-of-plane seismic effects at each diaphragm level with metal anchors or straps. N/A
Wall Openings TRUE
Quality of Building Materials Quality of building materials is considered to be adequate per the requirements of national codes and standards (an estimate). TRUE
Quality of Workmanship Quality of workmanship (based on visual inspection of a few typical buildings) is considered to be good (per local construction standards). TRUE
Maintenance Buildings of this type are generally well maintained and there are no visible signs of deterioration of building elements (concrete, steel, timber). FALSE

Additional comments on structural and architectural features for seismic resistance:

Vertical irregularities typically found in this construction type: Other

Horizontal irregularities typically found in this construction type: Other

Seismic deficiency in walls: Limited ductility and the absence of tie columns diminishes shear strength.

Earthquake-resilient features in walls: Good transfer of seismic forces

Seismic deficiency in frames:

Earthquake-resilient features in frame:

Seismic deficiency in roof and floors:

Earthquake resilient features in roof and floors:

Seismic deficiency in foundation:

Earthquake-resilient features in foundation:


Seismic Vulnerability Rating

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

High vulnerabilty Medium vulnerability Low vulnerability
A B C D E F
Seismic vulnerability class |- o -|

Additional comments section 5:


6. Retrofit Information

Description of Seismic Strengthening Provisions

Structural Deficiency Seismic Strengthening
Columns Installation of additional shear reinforcement in tie columns (Figure 7)
Parapets and nonstructural walls (new construction) Parapets are confined with tie-columns and bond-beams. When parapets are located between tie-columns, walls are isolated through construction joints.

Additional comments on seismic strengthening provisions:

Has seismic strengthening described in the above table been performed? Yes, parapets are confined and non structural walls are isolated from the structure.

Was the work done as a mitigation effort on an undamaged building or as a repair following earthquake damages? The seismic strengthening was done in a new construction.

Was the construction inspected in the same manner as new construction? N/A

Who performed the construction: a contractor or owner/user? Was an architect or engineer involved? Usually engineers are involved.

What has been the performance of retrofitted buildings of this type in subsequent earthquakes? Good seismic performance: parapets resist overturning forces and cracking effects were reduced in non structural walls..

Additional comments section 6:


7. References

  • Harmsen y Mayorca, 1997, de Estructuras de Concreto Armado, Pontificia Universidad Catolica del Peru.
  • Norma Peruana de Albanileria E-070, 1998, Capitulo Peruano del ACI.
  • Norma Peruana de Sismorresistente E-070, 1998, Capitulo Peruano del ACI.
  • Quiun, San Bartolome, Torrealva, Zegarra, 1997, El Terremoto de Nasca del 12 de Noviembre de 1996, Pontificia Universidad Catolica del Peru.
  • San Bartolome, 1994, Construcciones en Albanileria, Pontificia Universidad Catolica del Peru.
  • San Bartolome, Munoz, Rodriguez, 2001, Fuerzas as de para Edificaciones de Albanileria, Pontificia Universidad Catolica del Peru.

Authors

Name Title Affiliation Location Email
Cesar Loaiza Professor Civil Engineering Dept., Catholic Univ. of Peru POB 1761 100 Lima, Peru cloaiza@pucp.edu.pe
Marcial Blondet Professor Civil Engineering Dept., Catholic Univ. of Peru POB 1761 100 Lima, Peru mblondet@pucp.edu.pe

Reviewers

Name Title Affiliation Location Email
Sergio Alcocer Director of Research Circuito Escolar Cuidad Universitaria, Institute of Engineering, UNAM Mexico DF 4510, MEXICO salcocerm@iingen.unam.mx
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