Description

The World Housing Encyclopedia (WHE) Report Database contains 130 reports on housing construction types in 43 seismically active countries. Each housing report is a detailed description of a housing type in a particular country. The description is prepared from a number of standard closed-ended questions and some narrative that have been provided by report authors. Each report has five major categories including architectural and structural features; Building Materials and Construction Process; Socio-economic Issues; Past Performance In Earthquakes, Seismic Features and Vulnerability; and Retrofit. All of the housing reports in this database have been contributed by volunteers. If you are interested in writing a housing report please contact the WHE Editorial Board.

About

The World Housing Encyclopedia (WHE) is a collection of resources related to housing construction practices in the seismically active areas of the world. The mission is to share experiences with different construction types and encourage the use of earthquake-resistant technologies worldwide. The technical activities of the WHE are steered by an international team of 22 professionals specializing in different aspects of seismic safety of buildings and structures. They bring relevant experience from 16 seismically active countries across the world. For more information about the World Housing Encyclopedia, visit http://www.world-housing.net/.

General Information

 

Report #:69
Building Type: Confined Masonry Building : Clay brick masonry, with concrete tie-columns and beams
Country: Serbia
Author(s): Nikola Muravljov
Radovan Dimitrijevic
Last Updated:
Regions Where Found: Buildings of this construction type can be found in urban and rural areas of Yugoslavia.
Summary:

This type of construction has been used for single-family and ...

Length of time practiced: 25-60 years
Still Practiced: Yes
In practice as of:
Building Occupancy: Residential, 10-19 unitsResidential, 50+ units
Typical number of stories: 2-4
Terrain-Flat: Typically
Terrain-Sloped: Typically
Comments: Buildings of this type are single family houses frequent, but there are a lot of multiple housing units and mixed too.


 

Features

 

 

Plan Shape Other
Additional comments on plan shape Usually regular shape.
Typical plan length (meters) 10
Typical plan width (meters) 10
Typical story height (meters) 2.8,3.0
Type of Structural System Masonry: Confined Masonry: Clay brick masonry with concrete posts/tie columns and beams
Additional comments on structural system Masonry walls transfer all gravity loads from the roof and floor slabs to the foundations. Minimum thickness for bearing masonry walls is 190 mm (as prescribed by the code). The Yugoslav National Building Code classifies masonry buildings into three categories, depending on the wall layout: - buildings with walls in transverse direction; - buildings with walls in longitudinal direction, and - buildings with walls in both directions. The main lateral load-resisting system for this housing type is a wall structure in with brick walls laid in both directions (transverse and longitudinal) carry lateral seismic forces and transfer them to the foundations. Reinforced concrete posts and tie-beams are effective in increasing the stiffness and ductility in this construction type and providing an improved level of seismic safety for this type of construction. Details of concrete posts and tie-beams are shown in Figure 9. A possible failure mechanism for confined masonry walls is illustrated in Figure 13.
Gravity load-bearing & lateral load-resisting systems
Typical wall densities in direction 1 5-10%
Typical wall densities in direction 2 10-15%
Additional comments on typical wall densities The typical structural wall density varies from 6% to 12%.
Wall Openings According to the Yugoslav National Building Code, size of the openings should not exceed 2.5 to 3.5 meters (depending on the seismic zone). The size can be increased up to 30% if the openings are confined with reinforced concrete posts and tie beams.
Is it typical for buildings of this type to have common walls with adjacent buildings? No
Modifications of buildings The most common pattern of modification in residential houses is complete removal or displacement of interior walls and columns. House owners usually perform modifications without seeking an advice of a competent technician (engineer/architect).
Type of Foundation Shallow Foundation: Reinforced concrete strip footing
Additional comments on foundation Foundation details are illustrated in Figure 10.
Type of Floor System Other floor system
Additional comments on floor system Structural Concrete: waffle slabs (cast-in-place) According to the National Building code, floor/roof must act as rigid diaphragm.
Type of Roof System Roof system, other
Additional comments on roof system Structural Concrete: waffle slabs (cast-in-place) According to the National Building code, floor/roof must act as rigid diaphragm.
Additional comments section 2 When separated from adjacent buildings, the typical distance from a neighboring building is 5 meters. Typical Plan Dimensions: Plan dimensions (i.e. length and width) of this building type should not exceed 40 to 50 meters. Length to width ratio is usually on the order of 3-4. In case the plan dimensions exceed these values, the walls need to be divided into sections by means of control joints. Typical Story Height: Typical floor height for residential buildings is 2.8 m, and 3.0 m for public buildings. Total height for buildings of this type should not exceed 20 meters (according to the code). Typical Span: Typical span (between the adjacent concrete posts) ranges from 3 to 6 m. The National Building Code prescribes the maximum span of 5 meters.

 

Building Materials and Construction Process

 

 

Description of Building Materials


Structural Element Building Material (s)Comment (s)
Wall/Frame Wall: Bricks/hollow clay tiles mortar Frame:Concrete posts and tie-beams: - Concrete -Steel reinforcement Wall: Characteristic Strength- Bricks : from 7.5-20 MPa Hollow clay tiles: from 5.0 to 20.0 MPa Mortar: from 5-15 MPa) Frame: Characteristic Strength- Concrete posts and tie-beams: Concrete minimum strength 20 MPa Steel: minimum yield stress 240 MPa Mix Proportion/Dimensions- Concrete posts and tie-beams: Minimum 3 fractions of gravel and 250 kg/sq. m of cement
Foundations Concrete and steel reinforcement Characteristic Strength: Concrete: minimum compressive strength 15 MPa Steel: minimum yield stress 240 MPa Mix Proportion/Dimensions: Minimum 3 fractions of gravel and 200 kg/sq. m of cement Foundation details are illustrated in Figure 10.
Floors Concrete -Steel reinforcementCharacteristic Strength: Concrete strength 15-30 MPa steel yield stress min. 240 MPa Mix Proportion/Dimensions: Minimum 3 fractions of gravel and 300 kg/sq. m of cement Details of prefabricated floor-slab construction are shown in Figure 11.
Roof Concrete -Steel reinforcementCharacteristic Strength: Concrete strength 15-30 MPa steel yield stress min. 240 MPa Mix Proportion/Dimensions: Minimum 3 fractions of gravel and 300 kg/sq. m of cement
Other

Design Process


Who is involved with the design process? EngineerArchitect
Roles of those involved in the design process Architects and engineers design buildings of this type. If certified engineers are not involved in the building design (i.e. non-engineered construction), National Building Code allows the construction of a building up to max. two-storey high. Engineers and architects work jointly on developing project for buildings of this construction type.
Expertise of those involved in the design process

Construction Process


Who typically builds this construction type? Builder
Roles of those involved in the building process Typically, builders (developers) build the housing of this type. In some cases, builders live in the houses of this type, too.
Expertise of those involved in building process
Construction process and phasing In this construction system, brick elements must be built and tied together in a specific way. Thickness of reinforced concrete vertical posts must be equal to the wall thickness. Minimum reinforcement to be provided in vertical posts consists of 4 -14 mm diameter steel bars tied with 6 mm diameter stirrups spaced at 250 mm on centre. Tie beams are constructed after the bricklaying is completed. Minimum reinforcement required in the tie beams consists of 4 - 12 mm diameter bars tied with 6 mm stirrups at 250 mm on centre spacing. In seismic areas lime/cement mortar has to be used. The construction of this type of housing takes place incrementally over time. Typically, the building is originally designed for its final constructed size. In some cases there are changes and differences between the designed and the constructed building. In such case, National Building Code prescribes the development of technical documentation describing the "as constructed" condition. Modifications (especially vertical expansion) for the buildings of this type are common, especially in case of single-family houses.
Construction issues

Building Codes and Standards


Is this construction type address by codes/standards? Yes
Applicable codes or standards The year the first code/standard addressing this type of construction issued was 1987. Technical regulations for construction in seismically prone areas, Title of the code or standard: Technical regulations for masonry construction. For all newly constructed buildings, building permits confirming that the construction has been done in conformance with the National Building Code must be issued; the code also prescribes the seismic zone the buildings are located in. Yugoslavia (and Serbia) are the part of the Balkan Peninsula, which is known to be one of the most seismically prone regions of Europe. However, until the catastrophic 1963 Skopje (Macedonia) earthquake, there were no seismic codes or regulations in the country. In 1964, the Preliminary National Building Code (including the seismic provisions) was issued. The latest edition of the National Building Code was issued in 1987. In addition to the National Code, Euro Codes have been used in the country as well.
Process for building code enforcement For all newly constructed buildings, building permits confirming that the construction has been done in conformance with the National Building Code must be issued; the code also prescribes the seismic zone the buildings are located in. Yugoslavia (and Serbia) are the part of the Balkan Peninsula, which is known to be one of the most seismically prone regions of Europe. However, until the catastrophic 1963 Skopje (Macedonia) earthquake, there were no seismic codes or regulations in the country. In 1964, the Preliminary National Building Code (including the seismic provisions) was issued. The latest edition of the National Building Code was issued in 1987. In addition to the National Code, Euro Codes have been used in the country as well.

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? Owner(s)
Additional comments on maintenance and building condition In the urban areas, public companies take care of maintenance for the housing stock.

Construction Economics


Unit construction cost Construction cost is about 100 to 150 $US/m# of built-up area (structure only), whereas the price of the finished building is on the order of 200 to 300 $US/m# of built-up area.
Labor requirements Construction of a typical building of this type (built-up area of 120-200 m#) takes approximately 6 months, depending on the finances. It should be also noted that this type of construction requires a limited number of trained labor and technical personnel. Majority of the other construction labor involved in this type of construction are generally unskilled.
Additional comments section 3

 

Socio-Economic Issues

 

 

Patterns of occupancy Usually one family occupies one housing unit. Each building typically has 10-20 housing unit(s). It varies from one unit per building (single-family house) to 50 units in condominiums.
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
Economic level of inhabitants Low-income class (poor)Middle-income class
Additional comments on economic level of inhabitants In the last 10 years, the economic situation in Yugoslavia has been very bad. The average net salary is less than 50 $ US per month. Economic Level: For Poor Class the ratio of the Housing Price Unit to their Annual Income is 50:1. For Middle Class the ratio of the Housing Price Unit to their Annual Income is 30:1.
Typical Source of Financing Owner financedCommercial banks/mortgagesGovernment-owned housing
Additional comments on financing
Type of Ownership RentOwn outrightOwn with debt (mortgage or other)Units owned individually (condominium)
Additional comments on ownership
Is earthquake insurance for this construction type typically available? Yes
What does earthquake insurance typically cover/cost The annual insurance rate is 0.45% of the building value increased by 15% to account for earthquake risk.
Are premium discounts or higher coverages available for seismically strengthened buildings or new buildings built to incorporate seismically resistant features? No
Additional comments on premium discounts
Additional comments section 4

 

Earthquakes

 

 

Past Earthquakes in the country which affected buildings of this type


YearEarthquake Epicenter Richter Magnitude Maximum Intensity
1969Banja Luka
1980Kopaonik
1980Banja Luka
1987Kraljevo
1998Mionica
1999Trstenik
6.4
5.7
6.2
4.9
5.7
5.1

Past Earthquakes


Damage patterns observed in past earthquakes for this construction type Damage to confined masonry buildings in these earthquakes was not extensive. Figure 14 shows damage to masonry buildings in the 1998 Mionica earthquake (magnitude 5.7). A number of older unreinforced masonry buildings were damaged in the earthquake however confined masonry buildings performed well and did not suffer any significant damage, as illustrated in the figure.
Additional comments on earthquake damage patterns Typical Earthquake Damage Patterns (Wall): Diagonal tension cracks

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 pathThe 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-VerticalThe building is regular with regards to the elevation. (Specify in 5.4.1)TRUE
Building Configuration-HorizontalThe building is regular with regards to the plan. (Specify in 5.4.2)TRUE
Roof ConstructionThe 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.TRUE
Floor ConstructionThe 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 PerformanceThere 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-RedundancyThe number of lines of walls or frames in each principal direction is greater than or equal to 2.TRUE
Wall ProportionsHeight-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 ConnectionVertical load-bearing elements (columns, walls) are attached to the foundations; concrete columns and walls are doweled into the foundation.TRUE
Wall-Roof ConnectionsExterior walls are anchored for out-of-plane seismic effects at each diaphragm level with metal anchors or straps. TRUE
Wall OpeningsTRUE
Quality of Building MaterialsQuality of building materials is considered to be adequate per the requirements of national codes and standards (an estimate). TRUE
Quality of WorkmanshipQuality of workmanship (based on visual inspection of a few typical buildings) is considered to be good (per local construction standards).TRUE
MaintenanceBuildings of this type are generally well maintained and there are no visible signs of deterioration of building elements (concrete, steel, timber).TRUE

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 Low shear strength and diagonal tension cracking as a result of brittle seismic response of unreinforced masonry walls subjected to seismic shear forces and gravity loads; brittle behavior.
Earthquake-resilient features in walls Typical brick strength is more than 20 MPa.
Seismic deficiency in frames
Earthquake-resilient features in frame
Seismic deficiency in roof and floors In some cases inadequate rigidity of roof and floor slabs
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 vulnerabilityLow vulnerability
ABCDEF
Seismic vulnerability class o

Additional comments section 5

Retrofit Information

 

Description of Seismic Strengthening Provisions


Structural Deficiency Seismic Strengthening
Walls: Low shear strength and diagonal tension cracking as a result of brittle seismic response of unreinforced masonry walls subjected to shear forces and gravity loads; brittle behavior Reconstruction of damaged walls; New reinforced concrete w all overlay; Injection grouting of cracks; Application of carbon fiber laminates bonded diagonally to the walls

Additional comments on seismic strengthening provisions
Has seismic strengthening described in the above table been performed? Yes, all strengthening methods were used in design practice. Structural engineers provide design specifications for the seismic strengthening design.
Was the work done as a mitigation effort on an undamaged building or as a repair following earthquake damages? In most of the cases, seismic strengthening has been performed as a part of post-earthquake rehabilitation (e.g. after the 1979 Montenegro earthquake or 1998 Mionica earthquake).
Was the construction inspected in the same manner as new construction? Yes
Who performed the construction: a contractor or owner/user? Was an architect or engineer involved? Usually it was owner/user who performed the construction, with competent participation of an architect and engineer.
What has been the performance of retrofitted buildings of this type in subsequent earthquakes? The buildings that were seismically upgraded were generally not subjected to another major earthquake. However, it is expected that the strengthened buildings would show improved seismic performance if subjected to an earthquake.
Additional comments section 6

 

References

Collection of Yugoslav Codes and Standards : Lateral Forces - Masonry Belgrade, Yugoslavia 1995


Selected Chapters of Earthquake-Resistant Construction Petrovic,B. Structural Book, Belgrade, Yugodslavia 1985


The Earthquake Influence on Buildings in the Region of Mionica Acimovic,B. Proceedings, Institute for Testing Materials IMS, Belgrade, Yugoslavia 1998


Masonry and Wooden Construction Muravljov,M. and Stevanovic,B. Faculty for Structural Engineering, Belgrade, Yugoslavia 1999


Effects of Concrete Posts in Block and Brick Walls Muravljov,M., Muravljov,N. and Denic,D. Congress SIG, Vrnjacka Banja 1999


Authors



Name Title Affiliation Location Email
Nikola Muravljov Senior Structural Engineer Structural Engineering Department, IMS Institute Bul. Vojvode Misica 43, Belgrade 11 000, SERBIA koljaka@eunet.yu
Radovan Dimitrijevic Consultant Advisor Duros Company Ace Joksimovica 102 Zarkovo, Belgrade 11 000, SERBIA rakadim@eunet.yu

Reviewers


Name Title Affiliation Location Email
Svetlana N. Brzev Instructor Civil and Structural Engineering Technology, British Columbia Institute of Technology Burnaby BC V5G 3H2, CANADA sbrzev@bcit.ca