Critical Evaluation of Practice Report: BNV7045, Civil Engineering

This report presents a critical evaluation of glazing practices in civil engineering, focusing on conventional mechanical mounting systems. It begins with an introduction to glass as a building material and its increasing use in facades, leading to advancements in installation technologies. Chapter Two delves into various glazing systems, including structural glazing, curtain walling, and bolted glazing, detailing their components and applications. It emphasizes the importance of location blocks, silicone sealants, setting blocks, and other components. Chapter Three explores professional knowledge through interviews with industry experts, including a glazing professional, architect, and main contractor, discussing challenges related to sealant application, substrate compatibility, and environmental conditions. Chapter Four examines quality control measures. The report concludes with a summary of findings and highlights the importance of adhering to industry standards and best practices in glazing systems.

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CRITICAL EVALUATION OF PRACTICE
By (Name)
Course
Professor’s name
University name
City, State
Date of submission

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TABLE OF CONTENT
CHAPTER ONE:INTRODUCTION...........................................................................................3
CHAPTER TWO : TECHNOLOGICAL AREA: CONVENTIONAL MECHANICAL
MOUNTING..................................................................................................................................3
CHAPTER THREE – PROFESSIONAL KNOWLEDGE, PROBLEMS AND
SOLUTIONS................................................................................................................................11
INTERVIEW WITH MR JONES A GLAZING PROFESSIONAL..............................................11
ARCHITECT..............................................................................................................................12
MAIN CONTRACTOR...............................................................................................................13
CURTAIN WALL SUPPLIER....................................................................................................13
STRUCTURAL SILICONE SUPPLIER.....................................................................................14
CHAPTER FOUR :QUALITY CONTROL.............................................................................16
CHAPTER FIVE:CONCLUSION.............................................................................................17
REFERENCES............................................................................................................................18

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CHAPTER ONE: INTRODUCTION
Glass is a very popular building material with architects and engineers. This is because of the
ability to transmit light and provide a linkage between the interior and exterior spaces while still
presenting a modern sophistication. In the beginning of the twentieth century the ability to bring
light into the interior while, capturing the exterior environment was very limited. This however
changed with the introduction of steel and concrete. With technological advancements and
structural solutions, the use of glass on small openings advanced and it glass was used
structurally and covered larger openings. Later on glass was used on full building facades and
sometimes formed the entire building envelopes. This shift in the use of glass has precipitated a
demand in new technologies for glass installation and the mounting of glass systems.
Figure 1: Building glass facades in Sri Lanka
Source: google images

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CHAPTER TWO: TECHNOLOGICAL AREA: CONVENTIONAL MECHANICAL
MOUNTING
Glazing
This refers to the facades of a building comprising of glass. It is derived from the word glass.
Some of the common glazing systems on accounts of explicit knowledge include:
1. Structural glazing
2. Curtain walling
3. Bolted glazing
4. Fin supported glazing
5. cable stayed glazing
6. suspended glazing
Structural glazing
Structural glazing refers to the utilization of a silicone sealant that exhibits strength and
high performance to bond glass to the structural members of a building (Aiello, et al., 2011). The
sealant used in this case has to undergo thorough testing for structural glazing purposes. This
type of technique can be utilized with most of the glass types.
Some of the components of a structural glazing system include:
1. Location blocks
2. Silicone sealant
3. Setting blocks, gaskets and spacers
4. Structural framing
5. Glass

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Figure 2: Actual site installation of panels’ beings handled from inside
Source: design drawing by BES
According to Kelly, his mental development on personal construct theory meant to improve or
construct new technology and ideas that improve the quality of life and by giving us different
experience and observations. The glazing system has not been left out by the personal construct
theory to create or construct new technological components to improve the operation of the
structural glazing system. There are different parts of the structural glazing system have to be
assembled together either in shop or on site to form the structural glazing system with the help of
constructs work mechanism. This can be done either manually by glazing professionals or
mechanically. Mechanical mounting and bonding of the structural systems and components
involves the use of machines and specialized building information modelling software to fit the
different parts together. It allows for easy and fast assembly of the entire system. Some of the
components of a Structural glazing System include:
Location blocks- these are glass edges that help restraining the glass units location in the
structural frame for the efficient transmission of loads imposed on the glass.

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Silicone sealant: This special adhesive is strong and compatible and is used to block the
penetration of unwanted elements including water, air, dust, or heat through the joints of the
structural system (Bennison, et al., 2008). They are based on the polymers of silicon and exist in
three types including oxime cure, acetoxy cure and alcoxy cure (Arasteh, 2008). For internal
applications, the acetoxy cure is recommended while for external use the oxime and alcoxy
cures, which are neutral in nature, are recommended since they possess better waterproofing
capabilities as well as adhesive properties (Bennison, et al., 2008). The neutral silicones (oxime
cure and alcoxy cure) are recommended for surfaces where acetic acid cannot be used.
There are different factors considered in the selection of the sealant:
1. The glazing system type being used
2. The parameter of the design to be achieved
3. Glazing contractor requirements
Setting blocks, gaskets and spacers – these provide the required support for the glazing material
in relation to glass size, techniques of glazing and the conditions in the use of the glazing
(Koccaz, et al., 2008). Some of the factors considered in the choosing of these elements by the
glass manufacturer include:
1. The size of the glass installation
2. The location within the building envelope or structural frame
3. The hardness of the element as a factor of its ability to resist loads
4. The compatibility of the elements or fabricated materials of the parts with the sealant to
be used in the fixing and the preformed rubber parts. It is important that the materials
used do not react with the silicon sealant and result in a color change (Konstantin and

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Konvin Assoc Ltd, 2011). A change of color is therefore proof that there is a chemical
reaction which may in the end lead to the total loss of adhesive force between the
structural silicon sealant and the members it is joining, either glass or metal upon
exposure to ultraviolet light. For example, neoprene and EPDM (ethylene propylene
diene monomer rubber) which are organic rubbers change in color upon exposure to
ultraviolet light leading to a resultant loss in the adhesive force of the sealant (Konstantin
and Konvin Assoc Ltd, 2011). The two rubbers are therefore not to be used in a structural
glazing system since they are not compatible
Types of structural glazing
1. Four sided framed glazing
2. Two sided framed glazing
3. Slope glazing
4. Frameless glazing
5. Glass fin glazing
Four sided framed glazing:
This is the most wide used system of structural glazing mainly because it is economical
In this system of structural glazing, a pre-fabricated frame that is made of horizontal and vertical
support members is installed on the building. Glass is supported by a frame that is fabricated on
the four sides and anchored in the frame. In this system glass is used as an infill panel (Serpico,
et al., 2010).

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Figure 3: four sided framed glass Source: (Serpico, et al., 2010)
Two sided framed glazing
In this type of structural glazing the glass is fabricated on two sides for support in either the
vertical or the horizontal direction while on the other two sides silicone is used. This system of
glazing also involves prefabrication of the members before they are assembled on site
(Strickland, et al., 2012).
Figure 4: two sided framed glazing Source: (Serpico, et al., 2010)

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Slope glazing
This is structural glazing done on slanted surfaces of building. Special glass is used in these
systems with the European standards approving only splinter proof laminated glass for use in
these kind of systems (Suarez, et al., 2012). The glass weight is also a major issue of
consideration in these systems.
Tooth shape glazing
Tooth shape glazing involves specialized glass panels. They are manufactured in stages with the
exterior panels being produced first followed by an internal panel (Suarez, et al., 2012). The
inner surface of the internal panel houses a structural joint for each glass unit.
Figure 5: Tooth shape glazing Source: (Suarez, et al., 2012)
Frameless glazing
Also referred to as bolted or spider glazing system. In this type of structural glazing, the glass is
tied to the structural frame using hardware like spider fixtures (Woelfert & Engr, 2007). This
kind of glazing gives a seamless look to the facade of the glass. The joint sealant in these
systems has a structural function

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Figure 6: frameless glazing Source: (Woelfert & Engr, 2007)
Glass fin glazing
Glass fin glazing involves the placing of perpendicular sheet of glass on the façade of the
building to add strength to the glass façade (Suarez, et al., 2012). The bonding to the building
structure is done using special sealants and hardware.
Advantages of structural glazing
1. Allows for wider flexibility in the design of buildings.
2. Prevents breakage of glass as a result of extreme thermal conditions
3. Prevents the infiltration of water and unwanted air
4. Contributes to the overall increase in the thermal efficiency of buildings. This is due to
the reduction or total elimination in the exposure of the exterior metal framing.

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It is also important to address lateral and horizontal floor movement in the design due to wind
movement and imposed load. This aspects can induce racking in façade panels causing panel
deformation.
Figure 7: panel mode of movement due to building sway
Figure 8: floor bracket and curtain wall profile Source:
Rajan at BES consultant
CHAPTER THREE – PROFESSIONAL FACTUAL KNOWLEDGE, PROBLEMS AND
SOLUTIONS
Most of the experts gave their opinion on accounts of tacit knowledge of what they have learnt
throughout their profession. The interviewed professionals included glazing expert, architect and
main contractor.
INTERVIEW WITH MR JONES A GLAZING PROFESSIONAL
INTERVIEWER: what are the major constraints you face in the application of the sealant?
JONES; The main factors that affect the strength of a sealant after application include
The shelf life of the sealant: this refers to the duration that the sealant has been stored before use
The substrate and structural sealant compatibility, effectiveness in preparation of the surfaces for
the application of the sealants. This is done by priming or cleaning of the surface. The quality of

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application of the sealant tom the surfaces. Proper application should ensure good contact
between the surfaces and not have air voids, the duration allowed for the curing of the units that
are assembled in the factory and on site before movement of the units or removal of temporary
stops in the field (Kinowski, et al., 2016). The conditions of the environment at the time of
applying the sealants. These weather elements may include rain, temperatures, dust, and air and
they affect the quality of the application. Variation in the finishes of the metal used in the
structure, which may vary between different patches. The varying affects the ultimate strength of
the assembled members.
Caution should be exercised in the use of sealants to be used in structural glazing. Only tested
silicone sealants that possess adequate strength for the resisting of the loads imposed on the
structure should be used (Haldimann, et al., 2008). They are referred to as structural sealants.
General or multipurpose sealants if are not fit for structural glazing for a variety of reasons
detailed below:
- Exhibition of low cohesive strength
- Use of these sealants may result in deflection of glass edges when exposed to high wind
load (Kinowski, et al., 2016). The deflection could lead to the displacement of the spacer
bar and eventual rupturing of the primary seals in insulating glass units resulting in
breakdown of the unit.
In accounts of reflective knowledge, it is important to note that various glass types have special
considerations in their installation and use. For instance in the use of insulating glass a
verification of the compatibility of the edge seal of the insulating glass and the sealant to be used
must be done (Scandlyn, et al., 2010). In addition to that, the glass to be used must be high
quality insulating glass with a dual seal and a secondary silicone seal.