Critical locations are parts of a building most likely to be subject to accidental human impact.
CLASSIFICATION OF CRITICAL LOCATIONS
1AS 1288-2006, Glass in building – Selection and Installation
Guidelines on use of Glass in Buildings – Part A : Human Safety
| Any glass* |
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| Please refer to note 4 *Residual protection is the protection provided to avoid the impact of human being to glass. It is provided on the side of glass where there are chances of Human impact. It can be achieved by providing protection in form of a sill structure or transom, chair rail or a grill inside. Also please refer to recommendations against falling of glass. *Safety glass is not mandatory |
| Safety glass |
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| Safety glass |
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| Laminated safety glass |
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| Laminated safety glass |
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For sketches of examples refer annexure 1
NOTES TO TABLE A
Note 1: ‘Hf ‘corresponds to falling height in case of change in level and ‘Hs’ corresponds to the sill height.
Note 2: For definitions and explanation of terms see annexure 4.
Note 3: In case of mirror glazing, it should confirm to the requirements of other safety glasses unless it is fully backed by a solid material.
Note 4: If the smaller dimension of the pane is 250 mm or less and its area is 0.5 sqm or less, glass not conforming to safety glass requirements may be used, provided that its nominal thickness is not less than 6 mm. (applicable to vertical glazing)
Note 5: Toughened or laminated safety glass or safety organic coated glass should meet respective test requirements as mentioned in clause 6.0 of this document to qualify as safety glazing.
Note 6: The effective Toughened safety glass thickness and/or Laminated safety glass and/or Safety organic coated glass configuration shall be determined case by case with regard to:
Note 7: Precautions against chances of injuries due to broken glass falling on people:
Note 8: For inclusion of glass in furnitures the following standards may be referred:
Note 9: In case of external laminated glass facades, openable portions have to be left at regular distances for fire fighting and smoke exhaust.
Note10: If Insulating Glass Unit (IGU) is used in situations mentioned in this guide then any one of the following will apply:
LIST OF STANDARDS TO BE REFERRED FOR PROPER SELECTION
As mentioned in note 6, page 13, various factors like wind pressure, glass thickness, human load, aspect ratio, glazing type etc. need to be considered before selecting the safety glass. Below are a number of standards available, which can be referred to correctly select the safety glass.
GENERAL SAFETY CONSIDERATION
All Safety glasses shall be procured from certified manufacturers and the product shall conform to relevant standards.
Either a label that cannot be removed and reused or a permanent mark on the glass surface shall mark all the panels of safety glass according to Bureau of Indian Standards (BIS).
Each lable must contain the ISI mark as prescribed by the BIS, manufacturers name, registered trademark or code of the manufacturer or supplier, type of safety glass material, the standard or guidelines to which the safety glass has been tested and the grade of test classification.
If the glasses satisfy the relevant impact test performance requirements (or fragmentation test for toughened glass), in addition to all other appropriate tests to be carried out as listed in the table below, these materials can be classified as safety glass.
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In the above table ‘YES’ indicates test to be conducted.
Boil test for heat strengthened and toughened laminated glass can use laminates from ordinary annealed glass manufactured simultaneously.
DESCRIPTION OF TESTS REQUIRED TO CLASSIFY GLASS AS SAFETY GLASS
Sketches of examples for cases 1 to 5,Table A
CASE 1: Vertical walls – Risk of fall but residual protection or Hs >0.75m
CASE 2: Vertical walls – No risk of fall; Hf < 1.5m & Hs < 0.75m
CASE 3: Vertical walls – Risk of fall; Hf >1.5m & Hs < 0.75m
CASE 5: Glass acting as a balustrade / handrail
Coorelation between maximum glass area and glass thickness (impact load) Recommendatory.
A: FOUR SIDES FRAMED GLASS
In case of framed glass panels supported on four sides starting between the finished floor level and less than equal to 750 mm as described in case 2 & case 3 given in table A the maximum allowable area of the glass panel is as follows:
a) The maximum area of the normal or annealed glass less than equal to 0.5 sqm. Refer annexure 3.
b) The maximum area of the safety glass with respect to its thickness shall be with in the permissible maximum area as defined in the table C below.
Table C
Type of glass | Nominal Thickness | Maximum Allowable area (sqm) |
|---|---|---|
| Tempered Safety Glass | 4 5 6 8 10 12 | 2 3 4 6 8 10 |
| Laminated Safety Glass | 6 8 10 12 | 2 3 5 7 |
| In case of laminated glass the thickness of PVB is not accounted | ||
c) In case of glass panels supported on all four sides starting above greater than or equal to 750 mm or a protection / transom / chair rail is in place permanently from the finished floor level as given in Case 1, table A, the thickness of annealed glass shall be with in the permissible maximum area as defined in table D below.
Table D
Nominal Thickness (mm) | Maximum Allowable area (sqm) |
|---|---|
4 5 6 8 10 12 | 0.8 1.2 2.1 3.2 4.4 6.3 |
B: TWO / THREE SIDES FRAMED GLASS
In case of glass panel supported on two/ three sides starting` greater than or equal to 750 mm or has a protection from the finished floor level as given in Case 1, table A, then annealed glass can be used in following cases as mentioned in table E else tempered or laminated glass shall be used.
Table E
Nominal Thickness (mm) | Maximum allowable height of glass (m) | Maximum allowable glass area (sqm) |
|---|---|---|
6mm 8mm 10mm | < 1.2 > 1.2 to < 1.6 > 1.6 to < 2 | 0.9 1.8 2.7 |
B: FRAMELESS / NON-FRAMED GLASS
In case of frameless or non-framed glass panel toughened safety or laminated safety glass shall be used. The thickness of safety glass and corresponding maximum permissible area is given in the following table F:
Table F
Nominal Thickness (mm) | Maximum Allowable area (sqm) |
|---|---|
6 8 10 12 | 3.0 4.5 6.0 7.5 |
In all above cases and in cases wherein the glass area exceeds 7.5 sqm. it is recommended to check and determined thickness of the glass using finite element analysis under wind load as per IS : 875 (Part 3 1987; reaffirmed 1997) for external glazing and / or loads
given in table J, in case of internal glazing or glazing wherein there are chances of human impact.
C: POINT SUPPORTED GLASS For point fixed system the glass area and glass thickness shall be determined by the specific strength analysis and type of point fixing hardware.
Note: If Insulating Glass Unit (IGU) is used in situations mentioned in this guide then any one of the following will apply:
i) If IGU is installed in areas subjected to h u m a n impact on either side then both the panes of the unit shall meet the requirements of this guide. The maximum area specified may be multiplied by 1.5 provided that each of the component glass of the unit otherwise complies with the relevant guidelines of this guide.
ii) In situations where access is restricted to one side of the unit, then only the accessible side should meet the requirements of this guide without the application of above- mentioned factor of 1.5.
Glass Thickness Calculation (wind load) – Recommendatory*
A. WIND LOAD CALCULATIONS
The thickness of the glass supported on all four side to be used in façade, window panels is governed by the following factors:
a) Area to be covered by the window panel.
b) Aspect ratio of window panel (length / breadth) or (longer side / shorter side).
c) Effective wind pressure at the window height
d) Strength/load bearing capacity of glass to be used.
The empirical relation between the wind pressure, area of the glass panel and the required glass thickness is as follows:
Pnet * A = 200.0 * Tk (T < 6 mm)
Pnet * A = 200.0 * Tk + 1900 (T > 6 mm)
Wherein, Pnet = Net design wind pressure (N/m2)
A = area of glass panel (m2)
T = SNT or the standard nominal thickness (mm),
k = is a constant as shown in table H
Determining Pnet:
The wind pressure computation is based on the procedure given in IS: 875 (Part-3) 1987, (Reaffirmed 1997).
Net wind pressure (Pd), may be defined using the following equation:
Pd = Pz x Cp
where, Cp = Net pressure coefficient as per IS: 875 (Part-3) 1987
Depending upon the type of processed glass used net design wind pressure (Pnet) can be calculated as given below:
Pnet = Pd /Pf
Wherein, Pf is the pressure factor dependent on the type of glass as shown in the table G.
Table G: The values of the pressure factor Pf
S. No | Glass Type | Pf |
|---|---|---|
1. 2. 3. 4. 5. | Normal (Annealed) Laminated Tempered Insulating Heat Strengthened | 1.00 0.80 2.50 1.50 1.60 |
Table H: SNT and Corresponding ‘k’ values
‘T’ | ‘K’ | ‘T’ | ‘K’ |
|---|---|---|---|
| 3 mm 4 mm 5 mm 6 mm 8 mm | 1.683 1.732 1.753 1.765 1.570 | 10 mm 12 mm 15 mm 19 mm 25 mm | 1.578 1.583 1.579 1.569 1.569 |
Limiting Aspect Ratio (ARMAX):
The design of the thickness using empirical relation in as detailed above will be valid upto a limiting aspect ratio ARmax. The value of ARmax for different SNT of glass is shown in the following table I
Table I: SNT and Corresponding ‘ARmax.’ value
SNT | ARmax | SNT | ARmax |
|---|---|---|---|
| 3 mm 4 mm 5 mm 6 mm 8 mm | 7.3 6.8 6.5 6.3 5.9 | 10 mm 12 mm 15 mm 19mm 25 mm | 4.9 4.3 3.8 3.3 2.9 |
Side panels, partitions etc on the sides of the walkway, which can be subjected to human impact, need to be designed considering guarding loads given in table J. For four sided supported glass panel the glass thickness required could be calculated by inserting this loads in place of wind load.
Table J: In case of side panels – Design loads in different buildings
Type of Buildings | Line load UDL KN/m run | UDL (infill) KN/ sq m | Point Load KN |
|---|---|---|---|
| Residential | 0.36 | 0.5 | 0.25 |
| Office Building, Hotels, Hostels, Library, Museum, Hospital & Schools | 0.74 | 1.0 | 0.50 |
| Cinema, public buildings & points of assembly | 3.00 | 1.5 | 1.50 |
Where UDL means Uniformly Distributed Load
B. OTHER AREAS
For other areas not mentioned in this annexure refer to the previous clauses.
* Reference – Use of Glass in Building, by Shri N.K. Garg, Scientist, Central Building Research Institute (CBRI), Rourkee
Definitions
For the purpose of this guide the definitions given below will apply:
| Area: | The area of a panel between sightlines after glazing, calculated using the sight size. |
|---|---|
| Annealed Glass: | Another term for “ordinary” glass, most commonly used for float glass. |
| Aspect Ratio: | The ratio of a longer side of panel to its shorter side. |
| Balustrade: | A low wall forming a parapet to a stair, ramp, balcony, raised level, or a change in level. |
| Back Putty: | The portion of the putty remaining between the glass and the depth of the rebate after the glass has been pushed into position. |
| Beads or Glazing Beads: | A strip of wood, metal or other suitable material attached to the rebate to retain the glass. |
| Bite: | The width of silicone used to bond the fin or frame member to the edge of the glass panel. |
| Bedding Putty: | The compound placed in the rebate of the opening into which the glass is bedded. |
| Bent Glass: | Flat glass that has been shaped while into hot cylindrical or other curved shapes. |
| Bevelling: | The process of edge finishing flat glass to a bevel angle. |
| Block (Setting Block): | A small piece of wood, lead or other suitable material used between the edges of the glass (generally the bottom edge only) to centralize the glass in the frame (frequently called a setting block). |
| Building: | A structure, constructed with any matrials whatsoever for any purpose whether used for any habitation or not and includes – “Assembly building”, which means a building or part thereof where groups of people congregate or gather for amusement, recreations, social, religious, patriotic, civil, travel and similar purpose. “Assembly building” includes buildings of drama and cinema theatre, drive-in-theatres, assembly halls, city halls, town halls, auditoria, exhibition halls, museums, mangal karyalayas, skating rinks, gymnasia stadia, restaurants, eating or boarding houses, places of worship, dance halls, clubs, gymkhanas, road, air, sea or other public transportation stations and recreation piers. |
| Business Building: | Any building or part thereof used for transaction of business and / or keeping of accounts and record therefore offices, banks, professional establishments, court houses being classified as business buildings, if their principal function is transaction of business and / or keeping of books and records. |
| Chair Rail: | A fixed glazing bar, or rigid push bar, that provides protection from human impact. |
| Clear Glass: | Transparent glass. |
| Conbustible material: | The material which when burnt adds heat to a fire when tested for combustibility in accordance with the IS 3808-1966: Method of Test for Combustibility of Building Materials, National Building Code. |
| Corridor: | It means a common passage or circulation space including a common hall. |
| Distance Piece: | A small piece of wood, lead or other suitable material used to locate the glass between the bead and the back of the rebate, and prevent lateral movement. |
| Door: | A hinged, sliding or otherwise supported openable barrier providing entrance to and exit from a building, corridor or room. Doors may be framed or unframed. |
| Double Glazing: | Glazing that incorporates two panels, separated with an air space, for the purpose of sound insulation or thermal insulation or both. |
| Edge Polished: | Usually applied to flat glass, the edges of which have been polished after cutting. |
| Edging: | Grinding the edge of flat glass, to a desired shape or size. |
| Exposed Edge: | A glass edge that is not covered. |
| External Wall: | An outer wall of a building not being a party wall even though adjoining a wall of another building and also means a wall abutting on an interior open space of any building. |
| Faceted Glazing: | Flat panes of glass installed vertically at an angle to each other, to form a faceted curve. |
| Fin: | A piece of glass positioned and fastened to provide lateral support. |
| Fire resistant: | It means the time during which a fire resistant material i.e. material having a certain degree of fire resistance, fulfills its function of contributing to the fire safety of a building when subjected to prescribed conditions of heat and load or restraint. The fire resistance test of structures shall be done in accordance with IS 3809-1966 Fire Resistance Test of Structure. |
| Fire Separation: | It means the distance in metre measured from any other building on the site or from another site or from the opposite side of a street or other public space to the building. |
| Flat Glass: | A general term covering sheet glass, float glass and various forms of rolled and plate glass. |
| Float Glass: | A form of flat glass produced by reheating the continuous ribbon of glass whilst it floats over a bath of molten metal. |
| Frame: | A structure manufactured from timber, metal, glass or other durable material or combinations of materials such as glass fins and structural sealant, supporting the full length of a glazed panel edge. |
| Frameless Glazing: | See unframed glazing. |
| Front Putty: | The compound forming a triangular fillet between the surface of the glass and the front edge of the rebate. |
| Fully framed glazing: | Panels that have all edges framed. |
| Glass: | An inorganic, non-metallic material produced by the complete fusion of raw materials at high temperatures, into a homogeneous liquid, which is then cooled to a rigid, condition essentially without crystallization. |
| Glazing: | The securing of glass in prepared openings in windows, door panels, partitions and the like. |
| Guarding: | Glass used to prevent people falling wherever there is a change in floor level by means of a permanent barrier. |
| Heat Soaking: | Heat Soaking is done on toughened glass by reheating to a temperature of 290 oC and keeping it at this temperature for eight hours and cooling it gradually. The glass can break spontaneously and without provocation due to possible impurity of Nickel Sulphide in basic glass used for tempering. This risk of spontaneous breakage can be minimised by heat soaking process by forcing such glasses to break in the factory itself. |
| Heat Strengthened Glass: | Glass which has been heated past its softening point and chilled rapidly to increase its strength and make it thermally safe, but which breaks like annealed glass. |
| Heat Strengthened Laminated Safety Glass: | Laminated Safety Glass utilizing two or more panels of heat-strengthened glass in the make up. |
| Infill balustrades: | Balustrades in which the supported glass resists an infill pressure and / or point load applied to the glass panel. |
| Insulating Glass Unit (IGU): | The standard configuration for residential and commercial windows consisting of a sealed unit of two panes of glass separated by a metal spacer. |
| Internal Partition: | An interior dividing wall or such portion of an interior dividing wall that is not a door, side panel, shopfront or atrium wall. |
| Laminated Glass: | A composite material consisting of two or more sheets of glass permanently bonded together by a plastic interlayer material. |
| Laminated Safety Glass: | Laminated glass that satisfies the requirements for a safety glazing material according to this guide. |
| Maximum Thickness: | The thickness of a panel of glass at the maximum thickness tolerance. |
| Manifestation: | Any technique for enhancing a person’s awareness of the presence of transparent glazed areas. |
| Minimum Thickness: | The thickness of a panel of glass at the minimum thickness tolerance. |
| Mirror: | A piece of glass silvered on one side, with a protective paint coating. |
| Nominal Thickness: | A numeric designation used for reference purposes that indicates the approximate thickness of glass. |
| Non-combustible: | It means not liable to burn to add heat to a fire when tested for combustibility in accordance with the IS:3808-1966, Method of Test for Combustibility of Building Materials. |
| Non-residential Buildings: | Buildings other than those defined above such as hotels, hostels, motels, shops, offices, schools, public assembly buildings, and factories and those parts of the residential buildings common to a group of dwellings such as common circulation areas in blocks of two or more flats. |
| Safety organic-coated: | A glazing material consisting of a piece of glass coated and permanently bonded on one or both sides with a continuous polymeric coating, sheet or film, which meets the test requirements of the safety glazing standards. |
| Pane: | Single piece of glass cut to size for glazing. |
| Panel: | An assembly containing one or more panes. |
| Parapet: | It means a low wall or railing built along the edge of the roof or a floor. |
| Partition: | It means an interior non-load bearing divider, one storey or part storey in height. |
| Partly framed glazing: | Panels that have one or more edges unframed. |
| Rebate: | The part of a surround; the cross section of which forms an angle into which the edge of the glass is received. |
| Residential Buildings: | Buildings and such portions of buildings used as separate dwelling houses and flats, but not incorporating common circulation areas in blocks of two or more flats. |
| Residual protection: | It is the protection provided to avoid the impact of human being to glass. It is provided on the side of glass where there are chances of Human impact. It can be achieved by providing a sill structure or a grill inside. |
| Shower doors, shower screens and bath enclosures: | The panels, doors or windows a enclosing or partially enclosing a shower or bath. |
| Side Panel: | A panel (operable or inoperable) located adjacent to a doorway. It may or may not be in the same plane as the doorway. |
| Sloped overhead glazing: | Glazing that is inclined at less than 75 degrees to the horizontal and located, wholly or partially, directly above an area that may be used by people. |
| Span: | The dimension between supports. For panels supported on all four edges, it corresponds to the smaller of the sight size dimensions. |
| Spandrel: | That portion of the exterior wall of a multistory commercial building that covers the area below the sill of the vision glass installation. |
| Toughened laminated safety glass: | Laminated safety glass utilizing two panels of toughened safety glass in the make up. |
| Unframed glazing: | Panels without framed edges. |
| Wardrobe doors: | Doors that provide access to built in storage areas, excluding those fitted to pieces of furniture that are not built into the building. |
| Window: | It means an opening other than a door, to the outside of a building which provides all or part of the required natural light, ventilation. |
| Window Sill: | Solid wall (Brick or concrete wall) starting from the finised floor level to the base of first window or structural member consisting of a continuous horizontal metal/wooden forming the lowest member of a framework or supporting structure. |
Definitions
Relevant Codes / Standards / Publications
For the purpose of making this document the following codes / standards were referred:
– IS : 2553 (Part 1) – 1990 – Safety Glass – Specification.
– IS : 2835 – 1987 – Specification for Flat Transparent Sheet Glass (third revision)
– IS : 875 (Part 3) Reaffirmed 1997 – Codes for the Wind Loads.
– IS : 3548 – 1988 – Code of Practice for Glazing in Buildings
– IS : 10439 – 1983 – Code of Practice for Patent Glazing
– IS : 7760:1985 – Specification for steel glass-front cabinet
– 16CFR Ch II (1-1-04 Edition) – Part 1201 – Safety Standards for architectural glazing materials.
– ANSI Z 97.1 – 1984 (R1994) – Safety Glazing Materials – Used in Buildings – Safety Performance Specifications and Methods of Tests.
– AS: 2208 – 1996 – Safety Glazing Materials in Buildings
– AS 1288 – 2006 – Glass in Buildings – Selection and Installation.
– BS : 6206 – Part 4 – 1995 – Specifications for impact performance requirements for flat safety glass and safety plastics for use in buildings
– BS : 6262 – Part 4 – 1994 – Code of Practice for Glazing for Buildings – Safety related to Human Impact
– BS : 6262 – Part 6 – 1997 – Code of Practice for Glazing for Buildings: Special Applications
– BS : 952 – For nominal thickness of glass.
– BS : 8000 – part 7 – 1990 – Workmanship on Building Sites – Code of Practice for Glazing
– BS : 5516-1 – 2004 – Patent Glazing and Sloped Glazing for Buildings – Code of Practice for Design and Installation.
– BS : 8213 – Part 4 – 1990 – Windows, Doors and Rooflights: Code of Practice for the Installation of Replacement Windows and Doorsets in Dwellings
– BS EN : 12600 – 2002 – Glass in buildings – Pendulum tests – Impact test method and classification for flat glass
– BS : 7499 – 1991 – Specification for inclusion of glass in the construction of furniture, other than tables or trolleys, including cabinets, shelving systems and wall hung or free standing mirrors
– BS : 7376 – 1990 – Specification for inclusion of glass in the construction of tables or trolleys
– BS EN : 1727 – 1998 – Domestic furniture, storage furniture, safety requirements and test methods
– BS EN : 1153 – 1996 – Kitchen furniture, safety requirements and test methods for built-in and free standing kitchen cabinets and work tops
– JIS R 3206 – 1997 – Tempered Glass
– JIS R 3205 – 1997 – Laminated Glass
– DIN 52 337 – Methods of testing flat glass for use in buildings – pendulum impact tests.
– Glass Association of North America Installation Guide.
– Use of Glass in Building, by Shri N.K. Garg, Scientist, Central Building Research Institute (CBRI), Rourkee.
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