STRUCTURAL GLAZING

 a report
Case study of Ansal Plaza &
Select City Walk, New Delhi

Peyom Jini
A/1905/2006
3RD YR- B.Arch
SPA, New Delhi
 INTRODUCTI
ON
The use of glass in the structural elements such as facades, Floors and roofs is now a
substantial area. Using glass as a material in its own right with a minimum of
supporting structure to meet modern architectural expectations relating to achieving
maximum transparency, while at the same time creating a robust building envelope. The
use of glass in this way is now very popular and is highly fashionable design solution for
range of building types including commercial, leisure and individual residences.
The transparency and finely detailed nature of structural glazing enables architects to
develop the concept of reducing the physical separation between interior and exterior
spaces without compromising the need for performance.
In the early fifties, the outside of many high rise buildings changed dramatically. The
design of aluminum curtain walls for commercial buildings began to evolve, and
innovative glazing systems were introduced. Glass and metal building facades have
proven themselves cost effective, aesthetically pleasing, energy efficient, and capable of
performing under stringent environmental conditions.
Structural glazing is based on the use of sealants, not only as weather seals, but also for
the structural transfer of loads from the glazing panel to its perimeter structural support.
A high modulus sealant such as silicone meets the requirements of strength, adhesion to
glass and metal, weather resistance and ease of application.
 Structural wall systems with glass panels comprising the facade and
vertical glass mullions to structurally resist wind load and seismic
forces. They are free from visual obstructions, limiting the need for
metal framing to the perimeter creating a seemingly floating glass
façade running away from the main structure.

Wall section trough structural glazing

Wall section trough curtain wall

A Curtain wall is a non bearing exterior enclosure which is supported by a

buildings structural steel or concrete frame. The wall may consist of
preassembled panels or a metal framework which can hold either glass or other
opaque units.
 APPLICATION
•For aesthetic reasons - to give a seamless façade
•To create a particular building feature
•To upgrade existing facades
•To give improved acoustic and air infiltration performance
•To allow even heating and cooling of glass
•To allow easier building cleaning
•Easy replacement of damaged units
•Ease of seal inspection

Basic Components
•framing,
•vision glass,
•structural sealant, and
•Accessories.
With a few exceptions (e.g. sealants with special properties, glass mullions in all glass
systems and sealed unit spacers), the basic components are similar to most window and
curtain wall systems.
 MATERIALS
Silicone is the only type of sealant currently known to possess the structural and weathering
capabilities needed for all-glass designs. The type of silicone sealant used is a one
component, moisture curing, and acetic acid liberating material, commonly referred to as
an acid-curing silicone sealant. It is characterized by ease of application, excellent
adhesion, high flexibility, long-term durability, and a modulus which can meet structural
requirements.
Framing:-Aluminum and galvanized steel have been used for manufacturing
spacers for sealed insulated units. Also, wood, aluminum and vinyl are used as
framing materials for windows. fiberglass and polyurethane frames were introduced
as framing materials. Fiberglass profiles are made by binding fiberglass strands
together in a polyester matrix. The mix is then pultruded (pulled through a heated
dye), where the heat sets the material in the pultruded form.

Glass Panes
Made from high quality float glass, clear or tinted, horizontally
toughened
- Single Glass: 10, 12, 15 and 19 mm thick.
- Double Glazing: Standard 12/15/12 mm both panes toughened.
Alternative configurations can be accommodated, including
combinations with reflective or low emissivity glazing.
Screen printing also available.
Before toughening, each glass pane is pre-drilled with countersunk
holes to precise tolerance to properly accommodate the articulated
fitting.
Types of glass ** Clear Glass * Tinted Glass * Reflective glass
Reflective glasses are the most widely used glass for structural glazing
and curtain walling for reasons such as better light transmission,
reduced heat transfer etc.

Types of reflective glass * Hard coated glass or pyrolytic coated glass *

Soft coated glass or vaccum sputtered coated glass

Hard coated glass: * Better photometric properties than the tinted glass
and are low-performance glass. * Imported in sheet sizes and various
processes like tempering / DGU can be done locally. * This is cheaper
glass as the processes can be done locally saving customs duty * This
glass can be used as single glass in vision as well as spandrel glass

Soft coated glass: Medium performance glass * Superior glass than the
hard coated glass in terms of photometric properties. * Heat
strengthening will have to be done at the source of supply (abroad) and
DGU can be made locally. * This glass can be used as single glass in
vision as well as spandrel glass.
High Performance glass: * Most superior type of glass in terms of
photometric properties. *Can never be used as single glass and the whole
unit with DGU has to be imported from abroad.
PRINCIPAL DESIGN OPTIONS
Point fixing:- glass panels are Glass Fins for wind All Glass Structures:-
connected directly to primary bracing (stiffening):-
structures either via the joints rather than use cables or rely It is feasible for
between panel or by perforating on the primary structure it is structural glazing t be
the glass panel it self. This is also feasible to use glass fins used for facades,
commonly called Planar glazing. set at 90’ to the façade to
The use of toughened glass that
floors and roof , then
provide restraint , wind
can be drilled near its corners bracing and some degree of
it is no surprise that
was combined with a point fixing support. This option also led to some structures have
system that could to be connected the development of toughened been erected that are
at the nodal points of glass fort beams to support almost 100% glass.
pretensioned cable structures horizontal elements such as
hence the weight of each panes is floor and roofs
taken up by the structure
incrementally
 FIXTURES
Mostly Structural Glazing System is based on the concept of a point supported glass
pane suspended by using standard or custom designed brackets fixed to articulated
bolts in the corners of each pane.

Connection Brackets
Standard star-shaped (four holes) or perimeter (two
holes) connection brackets or other custom designed,
purpose made brackets can be used to pick up and
connect the threaded stem of the articulated fitting.
These brackets must be pre-designed in order to allow for
djustments due to tolerances either from the steel
structure or from the glass drilling

Spring Suspension Points

For large areas of suspended structural glazing it is advisable to
consider this special spring box suspension component to fix the
first row of glass panes to the supporting beam.
These springs will guarantee that the weight of the glazed wall is
always shared equally between the support points. In addition, the
spring will serve as a shock absorber for the entire glass system in
the event of breakage of one pane and the consequent instant
change in the load path.
 ARTICULATED BOLT
TheFITTINGS
key element of the system is the Articulated Bolt Fitting connection (Rotule). It consists
of a stainless steel stud with an integrated spherical bearing set into a hole in the glass in
such a way to centre the fixing loads on the neutral axis of the glass.
This design not only allows for the absorption of differential movement between the fixing
structure and the glass but it would also ensure that the hole in the glass will never be
loaded in bending during wind deflection or structural movement.

•It consists of a stainless steel countersunk head, housing a

spherical bearing with a threaded stem, obtained by means of
cold forming without welding.

•The spherical head has a stem with male or female threads to

allow for connection to the supporting bracket. The element that
houses the spherical head has a matching countersunk design in
order for it to be inserted into the countersunk hole in the glass.

•The Rotule is tightened to the glass by means of a threaded

locking washer.
The tightening torque is predetermined and is normally made off
site to avoid any inaccurate assembly on site which in turn might
create unforeseeable stresses in the system.
 During the assembly of the fitting through the glass, any direct
contact between steel and glass must be carefully avoided. For
this purpose thermoplastic materials are interposed to ensure
that the entire surface of the hole is loaded uniformly.

A pure aluminium bushing interlayer, which is initially soft and

gets harder after time when loaded, has proved to be the ideal
fitting to protect the countersunk hole in the glass. In addition, it
tends to follow the shape and imperfections of the hole in the
glass. This bushing is furthermore coated in Teflon (PTFE) to
prevent bimetallic corrosion between steel and aluminium.

The interposed element between the locking washer and the

glass is made of a thermoplastic material.

Joints
- Glass to glass joints are filled with suitable elastic silicone mastic.
- Perimeter joints may be sealed by means of extruded silicone weather seal
gaskets, to create a flexible joint to accommodate movements and dimensional
tolerances
 Cylindrical hole and standard bolt
For this kind of fitting, the dead load due to the glass weight is
concentrated in the area around the hole itself.

The glass is rigidly connected to the supporting bracket. This fitting

does not allow any differential movement between the glass and the
supporting structure.

Countersunk hole and countersunk bolt

This assembly produces a flush glass wall.
Any applied load (dead load, wind load, impact) concentrates in the area
around the countersunk hole.
Concentrated high stresses, along with imperfections on the surface of the
countersunk hole, may easily cause a breakage to start in that area.
Differential movement between the glass and the structure is not possible in this
system.
Countersunk Hole and Spring Plate
This system allows the glass some movement in respect of the supporting
structure and also gives the glazed area a completely flush appearance.
Movement is possible through the use of spring plates and countersunk bolts
located between the glass and the supporting bracket.
It should be noted however that, once the bolt is tightened to the supporting
bracket, and when glass deflection occurs, due to e.g. the wind load, the area
around the hole is supporting a considerable stress concentration.
Typical Structural Glazing Designs
There are three basic structural silicone sealant glazing systems which have evolved in the past
two decades, the all-glass, four-sided and two-sided systems.

The all-glass system offers maximum see-through visibility (using

supporting glass mullions). This system may be appropriate for
certain applications such as racetracks, store-fronts, showrooms and
lobbies

The four-sided system: - features a continuous all glass appearing curtain

wall from the exterior, but the glass panels have outside support from the
interior (Figure 8). It is also known as total-wall glazing, flush-glazing, zero
glazing, butt glazing or capless glazing. It incorporates continuous
horizontal and vertical curtain wall-like construction without traditional
metal stop retention (i.e. there is no wrap-around support channel).

The two-sided system : - (also known as the strip window or semi-cap

less system) features a continuous all-glass appearing strip on the
exterior, but the glass panels have two-sided support from the interior
(Figure 9). The system is similar to regular butt joint glazing except
that a metal mullion is used on the indoor side of the vertical glass
butt joint.
STRUCTURAL FRAMING
SYSTEMS
DIFFERENT FRAMING
SYSTEMS
ANSAL PLAZA, NEW
DELHI

Here the vertical mullions and horizontal transoms are

installed on Aluminum brackets which are anchored to
the columns/slabs.

Cut to size glass is fixed on the grid work with pressure

plates. (The glass is held Mechanically)
Cover cap is snap fit on the pressure plates for aesthetic
look.

In the above system 90% of the work can be done at

site.
SELECT CITY
WALK,SAKET, NEW DELHI

Here the vertical mullions and horizontal transoms are

installed on steel brackets which are anchored to the
columns/slabs.
Cut to size glass is fixed on the grid work with pressure
plates. (The glass is held Mechanically)
Cover cap is snap fit on the pressure plates for aesthetic
look.
Spider system is used to fix the big hoardings on the
front façade.