Reinforced concrete frame with concrete shear walls - dual system, Syrian Arab Republic

From World Housing Encyclopedia


1. General Information

Report: 59

Building Type: Reinforced concrete frame with concrete shear walls - dual system

Country: SYRIAN ARAB REPUBLIC

Author(s): Adel Awad, Hwaija Bassam, Isreb Talal

Last Updated:

Regions Where Found: Buildings of this construction type can be found in the main cities of Syria like Damascus, Aleppo, Latakia, Homs, and Hama. This type of housing construction is commonly found in urban areas.

Summary: These buildings are characterized by a combination of shear walls and frames in both directions. The buildings are multiple housing units found in the main cities of Syria. The shear walls are often part of the elevator and service cores, whereas the frames are arranged in-plane, in conjunction with the walls, to support the floor system. Stiffness and mass distribution are irregular and the majority of buildings may experience soft-story or torsional problems. As a result, these buildings are expected to have only moderate seismic resistance.

Length of time practiced: Less than 25 years

Still Practiced: Yes

In practice as of:

Building Occupancy: Residential, 20-49 units

Typical number of stories: 6-15

Terrain-Flat: Typically

Terrain-Sloped: Typically

Comments:


2. Features

Plan Shape: Rectangular, solid

Additional comments on plan shape:

Typical plan length (meters): 30

Typical plan width (meters): 20

Typical story height (meters): 3.1

Type of Structural System: Structural Concrete: Moment Resisting Frame: Dual system Frame with shear wall

Additional comments on structural system: The vertical and lateral load-resisting system is a dual system. Shear walls and frames (columns, beams) carry gravity loading. We can assume that the shear walls provide adequate strength and stiffness to control lateral displacements.

Gravity load-bearing & lateral load-resisting systems:

Typical wall densities in direction 1: 3-4%

Typical wall densities in direction 2: 3-4%

Additional comments on typical wall densities: The typical structural wall density is up to 3 %. The ratio between total wall area/plan area is 1 to 3% (for each floor).

Wall Openings: Area of openings/walls surface area= 20% for inner walls and 40% for outer walls.

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

Modifications of buildings: Buildings of this type haven't a lot of modifications yet.

Type of Foundation: Shallow Foundation: Reinforced concrete isolated footingShallow Foundation: Reinforced concrete strip footingShallow Foundation: Mat foundation

Additional comments on foundation:

Type of Floor System: Other floor system

Additional comments on floor system: waffle slabs (cast-in-place), solid slabs (precast)

Type of Roof System: Roof system, other

Additional comments on roof system: waffle slabs (cast-in-place), solid slabs (precast)

Additional comments section 2: When separated from adjacent buildings, the typical distance from a neighboring building is 10 meters.


3. Building Process

Description of Building Materials

Structural Element Building Material (s) Comment (s)
Wall/Frame Wall: Concrete Characteristic strength:1-3/18-25/1-2 Mix proportions: 1:2:4
Foundations Concrete Characteristic strength:1-3/18-25/1-2 Mix proportions: 1:2:4
Floors Steel Characteristic strength:360-420; Deformed bars
Roof Steel Characteristic strength:360-420; Deformed bars
Other Characteristic strength“360-420; Deformed bars

Design Process

Who is involved with the design process: EngineerArchitect

Roles of those involved in the design process: The designer may visit the construction site, at request.

Expertise of those involved in the design process: The structural engineer will have 5 years of studies and more than 5-10 years of experience.


Construction Process

Who typically builds this construction type? Other

Roles of those involved in the building process: It is built by developers and sold to the people who may live in this construction type.

Expertise of those involved in building process: The construction engineer may have 5 years of studies and less experience than the structure engineer.

Construction process and phasing: The owner of the land will hire an architectural office and structural engineer to design the building. They will use modern equipment. The construction of this type of housing takes place in a single phase. Typically, the building is originally designed for its final constructed size.

Construction issues:


Building Codes and Standards

Is this construction type address by codes/standards? Yes

Applicable codes or standards: Starting from 1997, the seismic design for buildings is mandatory as a law: Syrian Code for Earthquake Resistant Building (1995). Prior to 1997, seismic design was not applicable but the normal Syrian Building Code is used from 1972. The year the first code/standard addressing this type of construction issued was 1972. The most recent code/standard addressing this construction type issued was 1997.

Process for building code enforcement: The building design must follow the Syrian Code 1995. In case of damage arbitration process may take place at the court of justice. There is compulsory inspection during the construction and good revision of the structural project.


Building Permits and Development Control Rules

: 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)Renter(s)

Additional comments on maintenance and building condition:


Construction Economics

Unit construction cost: A unit construction may cost 170-300 USD/m# (USD =50 Syrian pound (SP), on market rate).

Labor requirements: One floor per month.

Additional comments section 3:


4. Socio-Economic Issues

Patterns of occupancy: Each building typically has 21-50 housing unit(s). 45 units in each building. One family typically occupies one unit.

Number of inhabitants in a typical building of this construction type during the day: >20

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

Additional comments on number of inhabitants:

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

Additional comments on economic level of inhabitants: Ratio of housing unit price to annual income: 4:1 Notes: 1. Below are the general guidelines related to the economic status of the inhabitants: Very Poor = lowest 10% of the population (per GDP) Poor = lowest 30% of the population Middle Class = from the lowest 30% up to the top 20% of the population Rich = top 20% of the population. Additional comments: GNP per capita, in 1997, was $1120. GDP per capita, in 1996, was $1288. Economic Level: For Middle Class the Housing Unit Price is 25000 and the Annual Income is 6000. For Rich Class the Housing Unit Price is 40000 and the Annual Income is 15000.

Typical Source of Financing: Owner financedPersonal savingsCommercial banks/mortgages

Additional comments on financing:

Type of Ownership: RentOwn outrightOwn with debt (mortgage or other)Long-term leaseOther

Additional comments on ownership: Other: Ownership by heritage.

Is earthquake insurance for this construction type typically available?: No

What does earthquake insurance typically cover/cost:

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:


5. Earthquakes

Past Earthquakes in the country which affected buildings of this type

Year Earthquake Epicenter Richter Magnitude Maximum Intensity
1719 Aleppo 5.5 (MMI) VIII
1759 Damascus 7.5 (MMI) X
1796 Lattakia 6 (MMI) VIII
1822 Aleppo/Al-jaziereh 7 (MMI) IX-X
1827 Harem/ Aleppo 6 (MMI) VIII

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Past Earthquakes

Damage patterns observed in past earthquakes for this construction type: Data about earthquakes taken from (Ambraseys, 1983), starting from 18th Century up to date. But estimation of values (Magnitude M and Maximum Intensity MMI) were made by us depending on our findings and experience. Most of the building destroyed were of adobe and stone masonry particularly in urban regions.

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. FALSE
Building Configuration-Vertical The building is regular with regards to the elevation. (Specify in 5.4.1) FALSE
Building Configuration-Horizontal The building is regular with regards to the plan. (Specify in 5.4.2) FALSE
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. TRUE
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 N/A
Quality of Building Materials Quality of building materials is considered to be adequate per the requirements of national codes and standards (an estimate). FALSE
Quality of Workmanship Quality of workmanship (based on visual inspection of a few typical buildings) is considered to be good (per local construction standards). FALSE
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: No flexural tension reinforcement; and no confinement at the wall ends.

Earthquake-resilient features in walls:

Seismic deficiency in frames: No special transverse reinforcement at the critical region (joints).

Earthquake-resilient features in frame:

Seismic deficiency in roof and floors: Weak connection between roof, floors and walls; and no lintel beams.

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:

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6. Retrofit Information

Description of Seismic Strengthening Provisions

Structural Deficiency Seismic Strengthening

Additional comments on seismic strengthening provisions: Seismic strengthening has not been done in Syria so far.

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

Was the work done as a mitigation effort on an undamaged building or as a repair following earthquake damages?

Was the construction inspected in the same manner as new construction?

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

What has been the performance of retrofitted buildings of this type in subsequent earthquakes?

Additional comments section 6:


7. References

  • Statistical Abstract 1999 Central Bureau of Statistic, Damascus 1999
  • Earthquake Damage in the Arabic Region Ambraseys,N,N. Assessment and Mitigation, UNESCO publication , pp. 11-15 1993
  • Scientific Fundamentals for Assessment and Mitigation of Earthquake Risk in Syria Awad,A. Damascus University Journal (“Issues of Applied Research”) Vol. 9, No 33-34, pp.21-47 1993
  • Human Development Report 1999 United Nation Development Program (UNDP) Oxford University Press, NY 1999
  • Seismic Design of Reinforced Concrete and Masonry Buildings Paulay,T. and Priestley,M.J.N. John Wiley and Sons 1992
  • Syrian Code for Earthquake Resistant Design and Construction of Building Syrian Engineers Order, Damascus Damascus 1995
  • European Marcoseismic Scale 1998 (EMS98) Gruenthal,G. European Seismological Commission (ESC), Luxembourg 1998

Authors

Name Title Affiliation Location Email
Adel Awad Civil Engineer/Professor University of Tishreen P.O. Box 1385, Latakia , SYRIAN ARAB REPUBLIC tuniv-lat@net.sy
Hwaija Bassam Civil Engineer/Associate Professor, University of Tishreen P.O. Box 1385, Latakia , SYRIA tuniv-lat@net.sy
Isreb Talal Civil Engineer University of Tishreen, Latakia , SYRIA tuniv-lat@net.sy

Reviewers

Name Title Affiliation Location Email
Ravi Sinha Professor Civil Engineering Department Indian Institute of Technology Bombay rsinha@civil.iitb.ac.in
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