COMMERCIAL HIGH RISE BUILDING DESIGN -4
Tall Buildings Standards and Codes
• ASHRAE has provided "HVAC Design Guide for Tall Commercial Buildings"
• Main standards are International Building Code (IBC), International Code Council (ICC), and National Fire Protection Association (NFPA)
• There are 32 standards for fire fighting and another 132 standards in place for fire fighting equipment as mentioned by the Bureau of Indian Standards.
• Local regulations / City codes are importance
• In Mumbai special "High rise Building committee (HRC)" made to support the BMC
NBC - 2016:
• Stringent guidelines for disaster, fire safety and structural safety for high-rises given in NBC
• National Building Code (NBC) has limitations with respect to detailed guidelines for designing of building services for Super High Rise Buildings.
International Building Code, Section 909 — Smoke Control Systems
ASHRAE — Principles of Smoke Management
ASHRAE — Applications. Chapter 52 — Fire and Smoke Management
NFPA 101 — Life Safety Code
NFPA 92A — Standard for Smoke-Control Systems Utilizing Barriers and Pressure Differences
NFPA 92B — Standard for Smoke Management Systems in Malls, Atria, and Large Spaces
National Building Code of India -2016, Part 4 — Fire and Life Safety Authority Having Jurisdiction (AHJ)
PLANNING CONSIDERATIONS IN HIGH RISE OFFICE BUILDINGS
The current trend for constructing office buildings is to build higher and higher. High-rise buildings are more expensive to construct per square meter, they produce less usable space and their operation costs are more than conventional buildings. The space efficiency, as well as the shape and geometry of the high-rise building need to satisfy the value and cost of the development equation. Yeang (1995) stated in his book The Skyscraper: Bioclimatically Considered" that net-to-gross floor area should not be less than 75%, while 80% to 85% is considered appropriate.
Factors affecting the design of high-rise buildings vary from place to place, such as local climate, zoning regulations, cultural conditions, technological opportunities etc. Generally the more simple and regular the floor shape is, the easier it is to respond to user requirements in terms of space planning and furnishing.
Square, circular, hexagonal, octagonal and similar plan forms are more space efficient than the rectangular plans with high aspect ratios and irregular shapes. Buildings with symmetrical plan shapes are also less susceptible to wind and seismic loads.
LEASING DEPTH:
Leasing depth or lease span is the distance of the usable area between the exterior wall and the fixed interior element, such as the core or the multi-tenant corridor. Smaller core-to-exterior window dimensions allow the users to maintain a relationship with the outside, thus benefiting from the natural light. According to Ali and Armstrong (1995) the depth of lease span must be between 10.0 and 14.0 m for office functions, except where very large single tenant groups are to be accommodated]
Floor-to-floor / Floor-to-ceiling Height:
The floor-to-floor height of a building is a function of the required ceiling height, the depth of the raised floor (if used), the depth of the structural floor system and material and the depth of the space required for mechanical distribution. The floor-to-floor heights range between 3.73 m and 4.20 m with an average of 3.98 m.
PLANNING OF SERVICE CORES IN HIGH RISE OFFICE BUILDINGS:
Service cores are an increasingly important aspect of building design, architecturally especially in High Rise buildings. In high tech building the size of service cores tends to increase thereby affecting the building's net to gross area ratio.
Simply stated, a service core is defined as those parts of a building that consist of elevators, the elevator shafts, the elevator lobby, staircases, toilets, E&M services, riser ducts. Its structure can also contribute to the structural stability of the building.
Service cores typically contain the following elements
Elevator shafts.
Elevator lobby.
Staircases — both main & fire escape.
Toilets.
Ancillary rooms such as pantry.
Mechanical vertical service riser-ducts e.g. for electrical power & lighting, water. sewerage pipes. rainwater downpipes. firefighting. exhaust ducts etc.
Mechanical vertical fire protection risers for sprinklers. hose reels- wet & dry
CORE DESIGN & TYPOLOGY
The proper core placement depends on following major aspects which need to be addressed are functionality of spaces, fire escape regulations, overall structural stability, E&M services, building typology and cost.
Smart core design plays a key role in the office buildings of the 21 century.
The position of the service core in relation to usable areas in the floor plate essentially determines the vertical circulation system of the building and how the other services are distributed.
Based on the location on the floor plate the cores can be classified as under:
Central core
Split Core
End core
Atrium Core
Selecting the correct criteria for the core design will help find the solution that will best meet the building's objectives.
For instance, if unencumbered clear internal space is one of the main aims of the design, a single-ended core may be the best solution although the permissible distance from the furthest corner of the space to the fire escape may be a limitation.
CENTRAL CORE
Horizontal circulation is easier.
Requires mechanical ventilation only
ADVANTAGE:
It allows all window space to be utilized as rental office space.
Permits offices to varying depth to receive natural light.
lt is suitable in terms of access and in some cases may be equidistant from all sides.
Simplifies area division.
DISADVANTAGE:
The central interior location limits the depth of the offices.
It requires an access corridor around its perimeter.
Some examples of the central core: Petronas Twin Tower, Malaysia
TENANT DISTRIBUTION
SPLIT CORE
Individual elevator can be designated for different group.
Horizontal circulation occupies more space.
Can have Natural Ventilation.
END CORE
Location of core leading to inefficiency in large floor plate.
Can have Natural Ventilation.
ATRIUM CORE
Horizontal circulation is not convenient for large floor plates.
Can have Natural & Mechanical Ventilation.
TENANT DISTRIBUTION
SERVICE CORE & COOLING LOAD
There is also a correlation between the location of the service core and the cooling loads of the building.
The split-core design with cores oriented east west, with glazing to the north and south has a lower cooling load compared to a central-core design. The cores on the east west elevations reduce the high solar gain. The service core can be placed to serve as solar buffers, thereby enabling a passive low-energy configuration.
DESIGN SYSTEM SHOULD AVOID THE HIGHEST COOLING LOAD
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