BUILDING CODEA building code, or building control, is a set of rules that

specify the minimum acceptable level of safety for constructed objects such as buildings and non building structures. The main purpose of building codes are to protect public health, safety and general welfare as they relate to the construction and occupancy of buildings and structures. The practice of developing, approving, and enforcing building codes varies considerably among nations. In some countries building codes are developed by the government agencies or quasi-governmental standards organizations and then enforced across the country by the central government. Such codes are known as the national building codes.

Scope:

Building codes generally include:

Rules regarding parking and traffic impact

Fire code  rules to ensure safe evacuation in the event of a fire

Requirements for earthquake, hurricane, tornado, flood, and tsunami resistance, especially in disaster prone areas or for very large buildings where a failure would be catastrophic

Requirements for specific building uses (for example, storage of flammable substances, or housing a large number of people)

Energy provisions and consumption

Grandfathering  provisions: Unless the building is being renovated, the building code usually does not apply to existing buildings.

Specifications  on components

Allowable installation methodologies

Minimum and maximum room and exit sizes and location

Qualification of individuals or corporations doing the work

For high structures, anti-collision markers for the benefit of aircraft

NATIONAL BUILDING CODE OF INDIA 2005

The National Building Code of India (NBC), a comprehensive building Code, is a national instrument providing guidelines for regulating the building construction activities across the country. It serves as a Model Code for adoption by all agencies involved in building construction works be they Public Works Departments, other government construction departments, local bodies or private construction agencies. The Code mainly contains administrative regulations, development control rules and general building requirements; fire safety requirements; stipulations regarding materials, structural design and construction (including safety); and building and plumbing services.

The comprehensive NBC 2005 contains 11 Parts some of which are further divided into Sections totaling 26 chapters. The salient features of the revised NBC (see Annex 2) include, apart from other changes made, the changes specially in regard to further enhancing our response to meet the challenges posed by natural calamities and reflecting the state-of-the-art and contemporary applicable international practices.

CONTENTS OF NBC 2005

PART 0 INTEGRATED APPROACH - PREREQUISITE FOR APPLYING PROVISIONS OF THE CODE

PART 1 DEFINITIONS

PART 2 ADMINISTRATION

PART 3 DEVELOPMENT CONTROL RULES AND GENERAL BUILDING REQUIREMENTS

PART 4 FIRE AND LIFE SAFETY

PART 5 BUILDING MATERIALS

PART 6 STRUCTURAL DESIGN Section 1 Loads, Forces and Effects Section 2 Soils and Foundations Section 3 Timber and Bamboo3A Timber3B Bamboo Section 4 Masonry Section 5 Concrete5A Plain and Reinforced Concrete 5B Prestressed Concrete Section 6 Steel Section 7 Prefabrication, Systems Building and Mixed/ Composite Construction7A Prefabricated Concrete7B Systems Building and Mixed/Composite Construction

PART 7 CONSTRUCTIONAL PRACTICES AND SAFETY

PART 8 BUILDING SERVICES Section 1 Lighting and Ventilation Section 2 Electrical and Allied Installations Section 3 Air conditioning, Heating and Mechanical VentilationSection 4 Acoustics, Sound Insulation and Noise Control Section 5 Installation of Lifts and Escalators 

PART 9 PLUMBING SERVICES Section 1 Water Supply, Drainage and Sanitation (including Solid Waste Management)Section 2 Gas Supply 

PART 10 LANDSCAPING, SIGNS AND OUTDOOR DISPLAY STRUCTURESSection 1 Landscape Planning and Design Section 2 Signs and Outdoor Display Structures 

SALIENT FEATURES OF NBC 20051) Inclusion of a complete philosophy and direction for

successfully accomplishing the building projects through Integrated Multidisciplinary Approach right through conceptual stage to planning, designing, construction, operation and maintenance stages

2) A series of reforms in building permit process 

3) Provisions to ensure and certification of safety of buildings against natural disaster by engineer and structural engineer

4) Provision for two stage permit for high rise and special buildings

5) Provision for periodic renewal certificate of occupied buildings from structural, fire and electrical safety point of view

6) Provision for empowering engineers and architects for sanctioning plans of residential buildings up to 500 m2 

7) Inclusion of detailed town planning norms for various amenities such as educational facilities, medical facilities, distribution services, police, civil defence and home guards and fire services

8) Revision of parking requirements for metro and mega cities

9) Up-dation of special requirements for low income housing for urban areas

10) Inclusion of special requirements for low income housing rural habitat planning

11) Revision of the provisions for buildings and facilities for physically challenged

12) Fire safety norms completely revamped through detailed provisions on Fire Prevention, Life Safety and Fire Protection 

13) Inclusion of new categories of starred hotels, heritage structures and archeological monuments for fire safety provisions

14) Substitution of halon based fire/extinguishers fire fighting system

15) Promotion to new/innovative building materials/technologies

16) Inclusion of latest provisions for earthquake resistant design and construction

17) Inclusion of details on mult-disaster prone districts

18) Inclusion of new chapter on design and construction using bamboo

19) Chapter on prefabricated and composite construction for speedier construction

20) Updation of provision of safety in construction

21) Complete revision of provision on building and plumbing services in line with applicable international practices

22) Provisions on rain water harvesting

23) Inclusion of new chapter to cover landscaping needs

AERODYNAMIC FORCES ON BUILDINGS

• A structure immersed in a given flow field is subjected to aerodynamic forces.

• For typical tall buildings, aerodynamic forces includes are drag (along-wind) forces, lift (across-wind) forces and torsional moments. The along wind forces act in the direction of the mean flow.

• The along wind motion primarily result from pressure fluctuations on windward and leeward faces and generally follows fluctuations in the approaching flow.

• The crosswind forces act perpendicular to the direction of mean wind flow.

• The common source of crosswind motion is associated with ‘vortex shedding’.

• Tall buildings are bluff as opposed to streamlined bodies that cause the flow to separate from the surface of structure, rather than follow the body contours. For a particular building, the shed vortices have a dominant periodicity defined by the Strouhal number.

• Hence, the building is subjected to periodic cross pressure loading which results in an alternating crosswind forces.

• The torsional motion is developed due to imbalance in the instantaneous pressure distribution on each face of the building.

• In other words, if the distance between elastic center of the structure and aerodynamic center is large, the structure is subjected to torsional moments that may significantly affect the structural design.

• It has been recognized that for many high-rise buildings, the crosswind and torsional responses may exceed the along wind response in terms of both limit state and serviceability designs

WIND EXCITATION

• The motion of tall buildings occurs primarily in three modes of action along wind, across wind, and torsional modes.

• For a rectangular building with one face nearly perpendicular to the mean flow, the motion is measured in the along wind and across wind directions as well as in the torsional mode.

ALONG WIND MOTION

• Along wind or simply wind is the term used to refer to drag forces.

• Under the action of the wind flow, structures experience aerodynamic forces including also the drag (along wind) force acting in the direction of the mean wind

• The structural response induced by the wind drag is commonly referred to as the along wind response. The along wind motion primarily results from pressure fluctuations on windward (building’s frontal face that wind hits) and leeward face (back face of the building).

ACROSS WIND MOTION

• The term across wind is used to refer to transverse wind. The across wind response, is a motion in a plane perpendicular to the direction of wind. In the design of most modern tall buildings, the across wind response often dominates over the along wind Response.

• For instance, the wind tunnel test Building showed that its maximum acceleration in across wind direction at its design wind speed is about 1.2 times of that of the in along wind direction

• Buildings are very sensitive to across wind motion, and this sensitivity may be particularly apparent as the wind speed increases.

• Wind induced instabilities of modern tower-like structures with excess slenderness, flexibility and lightly-damped (insufficient mechanical preventions against sides way such as use of tuned mass dampers) features could cause considerably larger across wind responses.

• Besides, while the maximum lateral wind loading and deflection are usually observed in the along wind direction, the maximum acceleration of a building loading to possible human perception of motion or even discomfort may occur in across wind direction.