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 #:79
Building Type: Concrete shear wall highrise buildings
Country: Canada
Author(s): John Pao
Svetlana Brzev
Last Updated:
Regions Where Found: Buildings of this construction type can be found in major Canadian cities: Toronto, Montreal, Vancouver, etc. This type of housing construction is commonly found in urban areas.
Summary:

This concrete shear wall high-rise represents a contemporary residential and ...

Length of time practiced: Less than 25 years
Still Practiced: Yes
In practice as of:
Building Occupancy: Residential, 50+ units
Typical number of stories: 12-35
Terrain-Flat: Typically
Terrain-Sloped: Typically
Comments: This is a rather recent construction practice, resulting from the population growth in Canadian urban areas in the last few deca


 

Features

 

 

Plan Shape Other
Additional comments on plan shape In general, buildings of this type are characterized with a regular plan. A typical building plan characteristic for residential high-rises of post-1970s construction is so-called "point block" system. Point block is characterized with a symmetrical plan (square, circular, hexagonal) with a centrally located elevator core, and the apartments are planned along all sides in a ring pattern around the core (Macsai 1976). Shear wall buildings are usually regular in elevation. However, in some buildings located in the downtown areas, lower floors are used for the commercial purposes and the buildings are characterized with larger plan dimensions; these are so-called "podium-type" buildings. In other cases, there are setbacks at higher floor levels.
Typical plan length (meters) 20
Typical plan width (meters) 20
Typical story height (meters) 2.6
Type of Structural System Structural Concrete: Structural Wall: Moment frame with in-situ shear walls
Additional comments on structural system The main elements of gravity load-resisting system are concrete columns (which form so-called "gravity frame"). The columns are typically supported by concrete flat slab structures or two-way slabs with beams. Shear walls also carry gravity loads, according to their respective tributary areas. The main lateral load-resisting system in this scheme consists of the reinforced concrete elevator core, and additional walls located elsewhere in the building as required. Shear walls have a dual role of transferring both gravity and lateral loads. Wall thickness ranges from 500 mm at the bottom gradually reducing to 350 mm at the top floors. The core houses the corridor leading to the residential units, the elevator shaft and stair wells, as well as mechanical and electrical conduits. Typical core plan dimensions are approximately 10 m by 6 m. The core is typically perforated with the openings and designed as ductile wall system according to the Canadian concrete design code. The coupling beams above the openings are designed with diagonal reinforcement provided to ensure ductile seismic response. The base of the core is designed to yield first forming a plastic hinge in this region. Shear wall structures are addressed by the National Building Code of Canada 1995 (NBC 1995) and the Canadian Concrete Code A23.3-94 Design of Concrete Structures (CSA 1994). In terms of the seismic design, NBC 1995 classifies shear wall buildings into the following two categories: nominally ductile and ductile wall systems, with the corresponding force modification factor R values of 2 and 3.5 respectively. It should be noted that R factor reflects the structural ability to perform in a ductile manner under seismic loads (elastic systems are characterized with R value of 1.0). The latest edition of the Canadian Concrete Code was published in 1994, with the previous editions in 1984, 1977, 1973 (limit state design) and 1970, 1966, and 1959 editions (working stress design). Since 1973 the concrete code includes special seismic provisions for shear wall structures. The provisions include requirements for the amount and detailing of horizontal and vertical wall reinforcement. In case of ductile shear walls (R=3.5), in addition to the distributed reinforcement (in both horizontal and vertical directions) with the required ratio of 0.25 % or higher, the code requires the use of concentrated reinforcement with minimum 4 bars at the ends of walls and coupling beams. The required area of concentrated reinforcement (at each end of the wall) is equal to 0.25% of the wall area. The philosophy of code provisions regarding ductile shear walls is based on the expected development of plastic hinges over the lower part of their height; this applies to the walls with no abrupt changes of the strength and stiffness. The provisions for coupled ductile shear walls (walls with openings) recommend the provision of diagonal reinforcement in coupling beams to ensure ductile behaviour and energy absorption capacity in the coupled wall system. The code provisions for nominally ductile shear walls (R=2.0) are less stringent, however the distributed reinforcement ratio (in vertical and horizontal directions) of 0.25% or higher is still required. Dynamic characteristics and seismic response of a typical Canadian shearwall highrise building were studied by Ventura (White 2001). Nondestructive dynamic ambient vibration testing of a 30-storey tower (overall height 85 m) was performed as a part of the study. The test has shown that the fundamental period of the structure was equal to 1.83 sec, whereas the periods in the second and third vibration mode were 1.55 sec and 0.78 sec. The linear damping ratios corresponding to the first three vibration modes were 8.0 %, 6.8% and 6.0 % respectively. The testing was performed while building was under construction and therefore damping ratios reflect the structural damping levels only.
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 Variable wall density.
Wall Openings In the buildings of this type, concrete shear walls are often perforated with openings. Interior walls are perforated with door openings, whereas elevator cores usually have openings on one or more sides (e.g. elevator doors, services etc). A typical size of door openings in the elevator core is 4'-6" (width) by 7'-4" (height).
Is it typical for buildings of this type to have common walls with adjacent buildings? No
Modifications of buildings Except for the removal or modification of light partition walls (usually drywalls), structural modifications in the buildings of this type are not very common. If such modifications are performed, building permit must be issued based on the advice of design professionals (architects and engineers).
Type of Foundation Shallow Foundation: Reinforced concrete isolated footingShallow Foundation: Reinforced concrete strip footingShallow Foundation: Mat foundationDeep Foundation: Reinforced concrete bearing piles
Additional comments on foundation It consists of reinforced concrete end-bearing piles.
Type of Floor System Other floor system
Additional comments on floor system Structural concrete: Flat slabs (cast-in-place) Floor and roof structures are of flat plate construction. Floor structures are considered in the design as rigid diaphragms.
Type of Roof System Roof system, other
Additional comments on roof system Structural concrete: Flat slabs (cast-in-place) Floor and roof structures are of flat plate construction.
Additional comments section 2 When separated from adjacent buildings, the typical distance from a neighboring building is 10 meters.

 

Building Materials and Construction Process

 

 

Description of Building Materials


Structural Element Building Material (s)Comment (s)
Wall/Frame Reinforced concreteconcrete compressive strength (fc')= 25-35 MPa Steel yield strength fy= 400 MPa Concrete compressive strength based on the cylinder strength
Foundations Reinforced concreteconcrete compressive strength (fc')= 25 MPa Steel yield strength fy= 400 MPa Concrete compressive strength based on the cylinder strength
Floors Reinforced concreteconcrete compressive strength (fc')= 40 MPa (lower floors) to 30 MPa (upper floors) Steel yield strength fy= 400 MPa Concrete compressive strength based on the cylinder strength
Roof Reinforced concreteconcrete compressive strength (fc')= 30 MPa Steel yield strength fy= 400 MPa Concrete compressive strength based on the cylinder strength
Other

Design Process


Who is involved with the design process? EngineerArchitect
Roles of those involved in the design process This is a fully engineered construction and architects and engineers are involved both in the design phase, in which they are playing a major role.
Expertise of those involved in the design process Architectural design for buildings of this type is developed by certified architects with an university degree in architecture, who are also the members of the Architectural Institute of British Columbia (AIBC), or other similar associations elsewhere in Canada. Structural design is performed by structural engineers, who are holding a university degree in civil engineering from a recognized university and are the members of the Association of Professional Engineers and Geoscientists of British Columbia (APEGBC). In order to become a member of the APEGBC, it is required to practice for at least 4 years. Engineering technologists (college graduates) are also involved in the design process.

Construction Process


Who typically builds this construction type? Contractor
Roles of those involved in the building process Buildings of this type are typically built by developers.
Expertise of those involved in building process This is a fully engineered construction and architects and engineers are involved both in the design phase, in which they are playing a major role, and the construction phase, in which they are performing regular inspection as per the requirements of the APEGBC and the municipalities. Construction professionals include a project manager (usually with a civil engineering degree), and construction labor - tradesmen: carpenters, rebar placers, and concrete placers.
Construction process and phasing The main advantage of this type of "concrete core/flat plate" cast-in-place concrete high rise residential tower is it can be constructed very quickly. Typical floor-to-floor cycle is one week, however three-day cycles are often achievable. The concrete core and columns are formed by "gang forms" that can be stripped and hoisted up to the next floor and reassembled within a few hours. The flat plate floor slabs are formed by forming tables, usually called "fly forms". When the concrete is set, the "fly forms" can be loosened, lowered and "flown" to the next level. An entire floor can be "flown" in a few hours. The primary hoisting equipment required is a tower crane that is positioned within the slab floor area. As the building height increases with the construction of each floor, the tower crane would climb with the building by jacking up at the base of the crane mast. The building exterior envelope may commence the erection prior to completion of the structure (typically the construction of the exterior envelope will commence after about 10 floors of the structure are complete). 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 CSA A23.3-94 Design of Concrete Structures 1959 National Building Code of Canada 1995 (seismic provisions for buildings are included in Section 4) CSA A23.3-94 Design of Concrete Structures (seismic provisions for shear wall structures included in Section 21) The most recent code/standard addressing this construction type issued was 1994.
Process for building code enforcement Building design in Canada must be performed according to the local building bylaws, which are different for different municipalities. These bylaws usually refer to provincial building codes (e.g. British Columbia Building Code), or (if provincial codes are not available) to the National Building Code of Canada. After the construction documents have been prepared, construction drawings are submitted for the approval to the municipality in which the building is located. The drawings are reviewed for compliance with the BC Building Code, as well as City Zoning and Development and Building regulations. For large and complex buildings, plumbing and mechanical systems are also reviewed. During the construction, building inspectors (employees of the municipality) are responsible for inspecting the various stages of building construction to ensure compliance with all applicable codes and bylaws. Once the construction is completed, building occupancy permit is issued (provided that the construction was completed in a satisfactory way).

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 In some cases there are problems associated with the slab construction. Slabs are relatively thin and there is a problem associated with the perforation through the slab (ducts, etc.).
Who typically maintains buildings of this type? Owner(s)Renter(s)
Additional comments on maintenance and building condition

Construction Economics


Unit construction cost Unit cost for the structural part only is around CAN$ 220/m# ($US 140/m#), and the cost of the competed building with finishes (excluding the underground parking) is approximately CAN$ 880/m# ($US 560/m#).
Labor requirements The construction progresses at a pace of approx. 1 floor/week (in some cases it may be 1 floor/4 days). The construction crew (for concrete part) includes 20 people.
Additional comments section 3

 

Socio-Economic Issues

 

 

Patterns of occupancy One family typically occupies one housing unit i.e. apartment. In case of smaller housing units, one person occupies one housing unit. Each building typically has more than 100 housing unit(s). 100-200 units in each building. The number of housing units depends on the size of the building (plan dimensions, number of stories, etc.)
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 In general, 300 to 500 inhabitants occupy one building.
Economic level of inhabitants Middle-income classHigh-income class (rich)
Additional comments on economic level of inhabitants The two main categories of inhabitants in buildings of this type are: families with lower income who cannot afford to own a single-family house (this is mainly the case with rental buildings) and younger professionals/couples who desire to live in an urban area (this applies both to the case of rental buildings and condominiums). Economic Level: The ratio of Housing Price Unit to middle class annual Income is 3:1.
Typical Source of Financing Personal savingsCommercial banks/mortgages
Additional comments on financing
Type of Ownership RentOwn 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 In case of apartment buildings, insurance covers the insured contents. The deductible is usually 5 to 6% of the inured value (depending on the insurance agency), irrespective of the type of the building and the location.
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

Past Earthquakes


Damage patterns observed in past earthquakes for this construction type Buildings of this type have not been subjected to the effects of damaging earthquakes in Canada so far.
Additional comments on earthquake damage patterns -Shear failures corresponding to diagonal tension, web crushing, or sliding shear (if shear strength is less than flexural strength); - Shear cracking around wall openings; - Buckling of longitudinal bars in boundary regions of plastic hinge zones (in cas

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 OpeningsN/A
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 - Inadequate amount of vertical reinforcement in the wall end zones (boundary elements); - Inadequate lap splices causing non-ductile flexural failure
Earthquake-resilient features in walls #NAME?
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 vulnerabilityLow vulnerability
ABCDEF
Seismic vulnerability class o -|

Additional comments section 5 Seismic deficiencies and earthquake damage patterns described in the above table are not expected to occur in case of shear wall structures designed according to building code requirements.

Retrofit Information

 

Description of Seismic Strengthening Provisions


Structural Deficiency Seismic Strengthening

Additional comments on seismic strengthening provisions Seismic strengthening of newer buildings of this type had not been performed in practice, as it is considered that these buildings meet the code requirements and would be able to resist the effects of possible earthquakes.
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? Not applicable
Was the construction inspected in the same manner as new construction? Not applicable
Who performed the construction: a contractor or owner/user? Was an architect or engineer involved? Not applicable
What has been the performance of retrofitted buildings of this type in subsequent earthquakes? Not applicable
Additional comments section 6

 

References

1996 Census Profile of British Columbia Statistics Canada www.bcstats.gov.bc.ca/data/dd/c96drdat.pdf 1996


High-Rise Building Structures Schueller,W. John Wiley and Sons, Inc., New York 1977


Design of Concrete Structures, A23.3-94 CSA Canadian Standards Association, Rexdale, Ontario, Canada 1994


Macsai, J. et al. (1976). Housing. John Wiley and Sons, USA.


NBCC (1995). National Building Code of Canada 1995. National Research Council of Canada, Ottawa.


NRC (1992). Manual for Screening of Buildings for Seismic Investigation. Institute for Research in Construction, National Research Council of Canada, Ottawa, Canada.


White, T.W. (2001). A Comparison of Linear and Non-Linear Three Dimensional Dynamic Analysis of a Vancouver Style Reinforced Concrete High-Rise Building, Department of Civil Engineering, University of British Columbia, Vancouver, Canada.


Urban Housing Construction in British Columbia, Canada Ventura,C.E., Robertson,J., and Brzev,S.N. Procs. of the 7th US Conf. on Earthquake Engineering, Boston, Page 28 2002


Bogdonov Pao Associates Ltd., www.bogdonovpao.com


Evaluation of Structural Earthquake Damage to Buildings in Southwestern B.C. Blanquera,A. Department Of Civil Engineering, University of British Columbia, Earthquake Engineering Research Facility, Technical report No. 00-03, Vancouver, Canada 2000


Authors



Name Title Affiliation Location Email
John Pao President Bogdonov Pao Associates Ltd. 426 West 6th Avenue Vancouver, BC jpao@bpa-group.com
Svetlana Brzev Instructor British Columbia Institute of Technology 3700 Willingdon Avenue, Burnaby, BC sbrzev@bcit.ca

Reviewers


Name Title Affiliation Location Email
Ofelia Moroni Civil Engineer/Assistant Professor University of Chile Santiago , CHILE mmoroni@cec.uchile.cl