Chapter 8Glazing System

8.2.1 Performance Criteria

The performance criteria to be satisfied by the glazing system are:

a) Structural stability and safety,

b) Energy efficiency (performance),

c) Visual comfort (light transmittance and reflection),

d) Fire protection (ability to resist/withstand fire),

e) Sound insulation,

f) Air infiltration (wind pressure, stack pressure, fan pressure), and

g) Water penetration (static, dynamic and cyclic pressures).

See Annex F for general guidance on the above.

8.2.2 Design Parameters

To achieve the performance criteria, care should be taken so that components in the system are selected and designed for the following parameters, such that the necessary performance criteria is met both individually and as a system

a) Loading,

b) Deflections and allowable stress,

c) Movements,

PART 6 STRUCTURAL DESIGN — SECTION 8 GLASS AND GLAZING

d) Impact resistance,

e) Acoustic and sound insulation, and

f) Energy performance.

8.2.2.1 Loading

Wind load, live load, dead load, load combinations as per good practice [6-8(11)], seismic load as per

good practice [6-8(8)], and other consequential loading may be considered.

8.2.2.2 Deflections and allowable stress

The deflection of framing members, members supporting brittle materials, metal panels, glass panels and the allowable stress shall be in accordance with 6.3.6.2. The allowable stress shall be in accordance with [6-8(11)].

8.2.2.3 Movements

The glazing system (and its framing elements) shall be able to accommodate the movements caused due to wind loads, seismic loads, live loads, dead load deflection, thermal expansion and contraction of members, and slab deflection, etc.

8.2.2.4 Impact resistance

Any glazing (in the glazing system) within 1 500 mm above the floor level of a building is considered likely to be subjected to human impact and hence, shall comply with the human impact safety requirements given in 7.

8.2.2.5 Acoustics and sound insulation

The recommendations on acoustics and sound insulation given in Part 8 ‘Building Services, Section 4 Acoustics, Sound Insulation and Noise Control’ of the Code shall be applicable.

8.2.2.6 Energy performance

The recommendations on the principal energy performance characteristics of the glazing system shall meet the provisions given in 5.

The primary characteristics required in general are reducing thermal losses and solar gains. For additional reference to visible light transmittance (VLT), solar heat gain coefficient (SHGC) and thermal transmittance (U factor) features, Part 11 ‘Approach to Sustainability’ of the Code shall be referred.

8.2.3 Types of Structural Frame Materials

For the framed/semi-framed systems, materials such as aluminium, stainless steel, uPVC and timber, which are commonly employed are listed hereunder.

8.2.3.1 Aluminium alloy

Extruded aluminium alloy used for structural framing members, shall be fabricated from the most appropriate grade of alloy complying with the relevant standard(s). The thickness of the aluminium sections should be in accordance with structural and hardware fastening requirements and shall be capable enough to meet the design requirements and satisfy the performance requirements.

Such extrusions in framing members and trims shall preferably be extruded aluminium grade 6063-T5, 6063-T6, 6060-T66, similar or stronger. Where 6063-T5 is to be used in shaped structures, supporting structural calculations particularly the stress criteria be ensured. Extrusion alloy 6061 or 6105 are commonly used for higher strength. Aluminium brackets shall be extruded aluminium grade 6061-T6 or approved equivalent. All aluminium alloys used as extruded rods/bars, tubes and profiles shall be compliant with accepted standard [6-8(12)].

Sheets and plates may be obtained from the following alloys of aluminium which also lists their primary characteristics:

a) 1100 — A low strength alloy suitable for applications requiring a high degree of formability.

b) 1135 — Brighter finish when anodized.

c) 3003 — General purpose sheet alloy with fair mechanical properties and excellent formability, susceptible to structural streaking when anodized (noticeable in large flat areas).

d) 5005 — Excellent workability, weldability and corrosion resistance.

e) 5052 — Slightly better mechanical properties and excellent corrosion resistance and weldability.

Other alloys can be used provided that they meet the required physical properties and the specified performance requirements.

8.2.3.2 Stainless steel

Mullions, panels, fascia, column covers, windows, doors, trim, roofing, gutters, flashing, hardware and other items where minimum maintenance is anticipated, shall be of austenitic stainless steels of Type 301, 302 and 304 complying with accepted standard [6-8(13)] and employed for their mechanical properties as they are highly corrosion resistant for all normal exposures.

For interior decorative applications, where regular maintenance will be provided, Type 430 may be used as it has lesser corrosion resistance properties. For external applications like in coastal regions where maximum resistance to corrosion is required, stainless steel shall be of Type 316. Particular attention shall be paid to the direction of the rolling grain on self-finished stainless steel components where the finish is aesthetically important. All screws, nuts, bolts, washers, self-tapping screws and other fastenings, including those used for the hardware, shall be of stainless steel Type 304, 316, 430 complying with accepted standard [6-8(13)]. Type 316 based steel fasteners, etc, shall be preferable when they are used in coastal regions on the exposed side.

8.2.4 Surface Finishes

The commonly employed surface finishes are listed hereunder:

a) Aluminium frame — The main types of aluminium frame coatings are as follows:

1. Anodized finish,

2. Powder paint finish, and

3. PVDF coating.

b) Steel frames — Surface finish on stainless steel frames plays a major role in its resistance to corrosion and hence it is an important design aspect to be clearly specified. The types of surface finishes listed here shall be in accordance with applicable relevant standards:

1. Mill,

2. Ground,

3. Brushed,

4. Polished,

5. Bead blasted,

6. Electro polished,

7. Coloured, and

8. Patterned.

Electro polishing of steel frames shall be done in accordance with available standards.

c) Timber frames — The function of finishes on timber is two-fold, first to improve the durability of the frame and second to add to the aesthetics. Unfinished, unprotected timber weathers as a result of gradual changes to its physio-chemical structure brought about by temperature and moisture content variations. The finishes may be of the following types:

1. Conventional opaque systems — Water and solvent borne,

2. Natural finishes — Semi-transparent and opaque, and

3. Water repellent preservatives, wood primers, undercoats and finishing coats (gloss, semi-gloss, flat and low sheen).

Based on the application, the appropriate type of finish shall be chosen.

8.2.5 Types of Anchorages

Anchorage are used primarily to join the mullions and transoms to the beam or slab through an appropriate bracket. The two basic types of anchors commonly used are:

a) Stud anchors — Used where the mullions have to be fixed to the face of the beam or slab.

b) Flush anchors — Used where the mullions have their start point or termination at a slab/beam or skirting.

Factors influencing the selection of anchors and to ensure proper performance of the anchor during its service life are:

1. Diameter — The following parameters shall be calculated for the selection of the anchor diameter:

i) Dead load acting on the anchor,

ii) Live load incident to the anchor (wind load- tensile or shear), and

iii) Weight of bracket, aluminium channels and other associated components.

2. Length — The length of the anchor is primarily based on the thickness of the glazing components which have to be fastened to the base material. Insufficient length shall lead to pull out failure.

3. Material — Stainless steel and galvanized iron are the two main types of materials used in the manufacturing of anchors.

4. Coating — The following type of coating shall be used based on the specific environmental condition met with:

PART 6 STRUCTURAL DESIGN — SECTION 8 GLASS AND GLAZING

5. Load direction — Based on the orientation of the anchor, they are incident to shear loading, tensile loading and combined loading of force and hence the proper diameter and depth of anchorage shall be selected.

6. Base material — The material characteristic of the base material also plays a major role in avoiding failure in the anchorage. The material shall be of suitable grade, have minimum thickness, shall be properly cured and have the necessary compressive stress.

7. Anchor spacing and edge distance — Anchor spacing is the minimum distance between two anchor centre lines without an influence on the tensile or shear failure load of either anchor. The load bearing capacity of an anchor is influenced by an adjacent anchor and thus the minimum anchor spacing specified by the manufacturer shall be adhered. Due to reduced material volume, a minimum edge distance shall be maintained to prevent the edge from breaking away prematurely when the anchor is installed, and also to achieve the full load bearing capacity of the anchor.

8.2.6 Hardware Materials

The material, geometry and finish of all the hardware materials shall be as per the requirement and should not affect the performance of the glazing system. All materials and finishes shall be as per relevant Indian Standards and tested before installing into the system in accordance to relevant Indian Standards.

1) Processes in levelling:

i) The sill bottom level of all the glazing elevations is to be checked by fixing a common benchmark and the reading should be recorded at minimum one metre distance.

ii) After taking the reading we can locate the highest and lowest point and then we can decide upon common level of all glazing elevations.

iii) The benchmark shall be a permanent mark, hence we shall be using oil paint mark in form of upside triangle

iv) The levels of all beam bottoms and up stand, if any, coming across the glazing elevations at all floors are to be measured.

v) Any other point that can affect fabrication drawings to be noted.

2) Processes in surveying:

i) The total width shall be measured using a theodolite and recorded at one plane.

ii) It shall be cross checked by measuring existing column to column (at other plan) distance.

iii) The two end point RCC shall be measured for plumbness. If any difference is observed, adjust the reading of first two steps.

8.4.3.1 Anchorage

a) Anchor installation shall be carried out by appropriately qualified personnel and under the supervision of the person responsible for technical matters of the site.

b) Installation shall be in accordance with the manufacturer's specifications and drawings using the tools indicated in the technical documents.

c) Use of the anchor shall be only as per that supplied by the manufacturer and without changing/exchanging the components of an anchor.

d) Checks before placing the anchor to ensure that the strength class of the concrete in which the anchor is to be placed is in the range given and is not lower than that of the concrete to which the characteristic loads apply.

e) Edge distance and spacing shall be not less than the specified values without minus tolerances.

8.4.3.2 Sub-structures

a) In order to avoid physical contact with the panels and frames during sealant application, which might cause adhesion loss, use of powder-free latex gloves shall be used, during panel placement.

b) Proper alignment and setting out of the sub-frame is critical in ensuring the ease of operation of the window/door.

c) Anchor/bolt heads and joints between external wall and sub-frame should be sealed with sealant for effective water tightness.

d) Prior to fixing the main frame, the sub-frame should be checked for any physical damages and any damaged sub-frame should be repaired or replaced.

e) Setting out of the sub-frame should also be verified before the installation of the main frame.

f) Dust and debris accumulated in the sub-frame could affect the alignment and fixing of the main frame and may also cause blockage to the weep holes, resulting in overflow of any

PART 6 STRUCTURAL DESIGN — SECTION 8 GLASS AND GLAZING

incidental water into the interior, and so it shall be properly cleaned before assembly.

8.4.3.3 Sealants

a) All components (glass and framing member such as aluminium) receiving the structural glazing silicone sealant shall be wiped thoroughly with a clean cloth dampened with a cleaner recommended by the manufacturer, and immediately followed by a dry wipe, using clean cloth.

b) All surfaces once cleaned/primed shall be handled carefully so as not to contaminate the surface.

c) The substrates shall be kept free from moisture, condensation, dust and other impurities.

d) An application temperature range of $+10^{\circ}\mathrm{C}$ to $+40^{\circ}\mathrm{C}$ (or as specified by the manufacturer) is recommended and shall be adhered to.

e) Substrate temperatures in excess of $+50^{\circ}\mathrm{C}$ will adversely affect curing process and also the adhesion of the sealant to the substrate.

8.4.3.4 Installation

The framing and fixing system of the panel should, in no case, cause shear stresses in the panel, either under the impact of external forces or due to differential expansion of components. The following shall be taken care of:

a) All framing shall be checked prior to glazing to assure that the opening is square, plumb and secure so that the uniform sealant bite, face and edge clearances are maintained.

b) Inspect all butt and mitre joints and if found open, they shall be sealed using sealants prior to glazing.

c) Minimum edge clearances shall be maintained between glass and sash, as mentioned by the manufacturer.

d) Setting blocks shall be used to support the glass unit which shall prevent the addition of stress applied on the structural tensile bead due to the self-weight of glass.

e) Adhesion tests shall be performed by the contractor/agency at the beginning and during the installation process.