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Abstract
Membrane structures are hugely popular in architectural design and are
increasing in their abundance within buildings. There is an increasing trend
concerning the use of membrane structures within architectural design. It is
important to recognize the reasoning behind the growth in popularity: why
are so many architects starting to use the design feature within their
designs? The features of the membrane structure have been provided; an
analysis of the strengths and weaknesses provides strength to the reasoning
behind its use. This study examines a variety of different factorsconcerning the membrane structures. It provides a detailed study of the use
of membrane structures within building design; additionally, all of the
different contributory factors have been referenced, such as the structural
components and mechanical usages. Much primary and secondary research
has been referenced to illustrate the breadth of the topic.
Membrane structures have been used in architecture for over 50 years;
therefore, there is a large back catalogue of research papers that focus on
them. The study follows a case study structure and uses 12 examples of
membrane structures within architecture. Each case study provides a real-
life example of how membrane structures have been successfully applied tomodern day architecture. Additionally, it examines the complexity behind
the construction of membrane structures and materials. It is important to
understand the structural components that make it so appealing to
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architects. The associated advantages and disadvantages of membrane
materials have been examined. Furthermore, the relationship between the
construction components and the integrated design has been mentioned. All
of these factors provide a strong understanding behind the use of membrane
structures, explaining how they can be used and why they are becoming so
popular.
IntroductionMembrane Structures
Membrane structures consist of thin membrane or fabric as a major
structural element. A membrane has no compression or bending stiffness,
therefore it has to be prestressed to act as a structural element. Major
applications of membrane structures occur mainly in large span lightweight
roof structures, temporary buildings such as tents and shelters. The
analysis, design and construction of such structures is a field that has
developed very considerably during the last 50 years.
Membrane structures are one form of architectural feature that arebecoming hugely popular within modern day engineering. They are
becoming majorly prominent in many designs. Although they have been
used in architecture for over 50 years, their use an aesthetic and ergonomic
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feature is becoming more apparent. Much of society is unaware of the
detailed specification behind the membrane structures. The complexity of
the construction process, involving all of its contributory materials, is
unknown to many people within the industry.
The history of membrane structure
A German designer by the name of Professor Frei Otto amazed architects
from around the world with his design of the Pavilion of the Federal Publicof Germany for the EXPO held in 1967 (Roy, 1967). At the time it was
standard to observe structures composed of steel and glass. Professor Freis
membrane structure was lightweight, slim and soft which provided
something new and fresh to the architectural field. His design was also very
different from any other designs at the time, as he used curved surface
areas which were made brighter due to the translucency of the membrane
material.
Membrane structures that closely resemble tent like structures came from
Germany. These were sturdy and reliable structures that quickly came to
form a vital aspect of modern day architecture which quickly spread across
the globe. Even in present times these structures are still regarded as veryreliable and still well suited to specific types of structures.
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In an essay he wrote in 1961, Professor Otto argued that buildings should
not be viewed or designed as fixed structures into which people can be
squeezed into. He further put forward his viewpoint that buildings should
grow along with us, and be renovated in such fashion. Otto stated that the
minimal structural material developed through extensive research was also
present in the natural environment, and that it was possible to utilize
properties present within organists to produce aspects of the membranes.
(Koch, 2004).
Otto reminded the world that although tents had been in existence for over
30,000 years and are considered as easy to construct, they are in fact
extremely difficult to structure correctly and that precise tent construction
is among the most difficult methods of construction.
Otto and his colleagues published an article in 1965 known as
Spannweiten, which detailed all of their findings in the research of
membranes structures from an architectural perspective. This paper
received attention from academics and experts in the field from across the
globe. Otto went on to work with other experts at the institute for
Lightweight structures where advancements in technology were made.These advancements were put into practice when the German Pavilion was
constructed for the 1967 Expo in Montreal (Roy, 1967). This building went
on to significantly shape the worlds knowledge of membrane structures
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and symbolized the latest advancements in this technology across the
globe.
The 1970 Expo was held in Japan. Rather than use structural forms
traditional to Japan, the architects decided to use membrane structures for
many of the constructions. Although the Expo showcased the reliable
potential of the membrane structures, they were not widely favored until
many years later (HeeKyun, 2005).
Numerous designs for membrane structures were put forward for The
USAs entry for the 1970 Expo. David Geigers design was accepted as it
was seen as more realistic as well as aesthetically pleasing to the eye. His
idea was to use a low profile air supported membrane for the structure of
the US Pavilion.
The US Pavilion was required to meet safety standards and therefore it was
designed so that in the event that the membrane structure did deflate, it
would not intrude on the spectators seating area or the field. This design
was hailed as further advancement in the development of membrane
structures that potentially allowed the development of air domes. Future airdome structures used the US Pavilion as a model for their designs.
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From 1970 it was the USA that led the way in terms of research and
investment into membrane structures. This paid dividends as Geiger Berger
associates made many new developments within the technology throughout
the 1970s. One such development was the use of PTFE coated glass fiber
membrane as a new membrane material. This material made it possible to
construct enduring, fixed membrane structures throughout the USA(Brown,
2001).
Famous early air dome structures in the USA were the Steve Lacy FieldHouse at
Milligan College which was built in 1974 and the Thomas E. Leavey
Activities Center at Santa Clara University which was built in 1976. These
were hailed throughout the USA as brilliant designs fit for purpose, and it
was these buildings which sparked a high demand throughout the USA for
air dome structures to be built(Mewes, 1993). Entertainment and stadiums
were hugely popular in the USA and they wanted these Domes to protect
them against all types of weather and to be capable of hosting a large
capacity of people. One example of these stadiums that successfully
utilized this technology was the Silver Dome of Pontiac city which was
constructed to be able to seat 80,000 spectators.
Before the construction of these air Domes, large scale spaces were
associated with negative characteristics such as shadowy and stuffy.
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However, this all changed with membrane structures which made it
possible for light to spread around the entire complex. Another great
advantage of the membrane structures are that they could be constructed
very economically, which is why they grew so rapidly throughout the USA
(Mewes, 1993). However, membrane structures used for air domes were
not without their problems. There were a significant number of structural
accidents, the costs associated with continual inflation was high and it was
complicated to control the inflation pressure. As such in the 1980s,
alternative viable structural techniques began to be investigated.
By the mid 1980s membrane structures were not just used to make spaces
bigger, but they had evolved to combine beauty with unique structural
forms. Buildings using this evolved technique included the Lindsay Park
sports center built in 1984 and the Chene Park Amphitheater built in 1990.
Additionally, membrane structure also began to be mixed with glass in
order to generate bright filled spaces (Kaltenbach, 2004). This technique
was particularly prevalent in shopping malls.
The air dome as the dominant structure in the USA was replaced towards
the end of the 1980s by the tensegrity dome which used an efficientsystem of cables and posts to securely cover large spaces. Examples of
buildings utilizing this new method at the time included the Redbird Arena
constructed in 1988, the thunder dome constructed in 1989 and the Georgia
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Balanced from a space frame acting as a compression ring, the membrane
structure of the Rome Olympic Stadium was a bright roof which utilized a
combination of a cable structure and a membrane structure. This was roof
was not only visually pleasing to the eye bit it also did not weigh very
much compared to structures that were used in the past. Other stadiums
such as the San Nicola
Stadium built in 1990 and the Gittlieb-Daimler stadium built in 1993 also
sought to use membrane structures to produce both beautiful and well lit
stadiums with their own blend of creativity (HeeKyun, 2005).
As developments were made in technology, PFTW coated glass fiber fabric
came to replace the PVC coated polyester fabric as the material of the
membrane structures in Europe (Kaltenbach, 2004).
There was too much replication of membrane structure designs according
to Frei Otto, and it was not until alternative framing techniques were
developed and that the structures were produced on a greater scale that
many individualist and creative form emerged.
Although Japan used membrane structures within the Expo that they hostedin 1970, there was not much demand for these types of structures in the
immediate years following this Expo. This was because Japan already had
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a uniquely aesthetically pleasing design style and because they were not
used to constructing suspension structures.
This situation changed quickly in the 1980s as design competitions were
hosted in Japan. A lot of the entrees in these competitions provided very
imaginative designs utilizing membrane structures and as such numerous
amazing structures utilizing this method began to be developed throughout
Japan. As this happened many architects began to realize how
advantageous membranes structures could be. Buildings were designed
with membrane structures which served to spread light to specific parts ofthe complex. Additionally, membrane structures allowed indoor crops to be
nurtured by the natural light which was filtered through, and as such the
position of the these plants were also factored into the blue prints of the
structures(HeeKyun, 2005).
Increasingly imitation of structures is become more prevalent around the
world. This was due in part to modern technology and the increased speed
of communication that this technology allows. When advancements in
design are found in one section of the globe, they quickly spread to other
parts.
Structure, Construction Method and Membrane Material
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A construction that directly utilizes the elements of membrane materials is
known as a membrane-structure building. Either a cable frame or a
skeleton frame can form the structure that sustains the membrane. It is
possible for a structure on a small scale to consist of the membrane itself as
the structural material. However, such a process is not possible on a larger
scale structure because the membrane is not strong enough. If used on a
large scale construction it is essential for the membrane to be strengthened
somehow or used in conjunction with a frame (Smith, 2001).
Membrane materials have enough strength to be directly linked to the main
frame unlike other roof materials. A membrane material has a natural
tendency to curve, and although it can endure tension, it cannot withstand
compression or bending. It is a complex task to make a curved surface
using tension, and the process of designing the membrane structures is
dependent on utilizing the tension in a precise fashion (Kaltenbach, 2004).
In the early days it was believed that membrane structures could only be
designed with mechanics in mind and that there was no room for creativity
in the design. However, it was later discovered that although the curved
surface is subject to specific mechanical requirements, there is much roomfor individualistic touches on the periphery of the surface area. Even so it is
important to note that the periphery must still be supported either with
cables or a frame.
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An architect, who is used to working on traditional structures, may find it
helpful to use a skeleton-frame membrane structure when constructing a
membrane structure. This is because the membrane is able to be extended
over steel, word or even a reinforced concrete frame in order to shape the
space (Herzog, 1996).
Balloons actually provided the inspiration for air inflated membrane
structures. Although F.W. Lancheser of England may have been first to putforward the idea for a field hospital, it was the Radar Dome built in the
USA in the year of 1946 that was actually the first time that this structure
had been created for a building on the ground. Following the success of this
dome, similar structures were replicated across the private sector in the
USA. As more of these structures were seen, international interest in these
structures significantly increased.
It is theorized that the use of membranes as structures were used over
30,000 years ago for the tents used by Nomadic tribes. Since these times,
the technology involved with membrane structures has been ever
increasing. These days, membrane structures are now as safe and durable astraditional buildings. This is due in part to the materials that form them.
Synthetic fibers and glass fibers are now utilized and coating materials
have enabled the structures to contain both water and fire resistant
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qualities. Advancements have been made and there are many advantages to
using membrane structures including their qualities of transparency, low
weight and their ability to be applied to frames for large scale spaces. For
instance, it is now possible to cover a large space that would not be
possible with traditional techniques with just one sheet of membrane
material (Kaltenbach, 2004).
However, it must be recognized that membrane materials are not simply
suited for all projects. If just one thin sheet is used then it will be difficultto adequately protect it from tearing as well as being difficult to provide
insulation for heat and sound
Advancements in the materials of the membrane structures have been
continually been made.
Significant advancements have included the industrialization of PVC in
1933, the development of PTFE in 1938, the industrialization of Polyester
fiber in 1947, and finally PTFE coated glass fiber fabric which was
developed in 1972(Mewes, 1993).
PTFE coated glass fiber fabric is considered a fixed long lasting building
material. It is incombustible, strong and durable, as well as having the
advantage of being self-cleaning. In contrast to previous membrane
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materials, PTFE coated glass fiber fabric is not designed to fold or to
detach from its support.
A critical advancement in the development of membrane structures has
been a material known as PTFE coated glass fiber fabric which is very
similar to stainless steel in terms of its durability. Its development as a
material increased the potential of membrane structures to be applied in a
many more circumstances.
However, when this material was first introduced and used in the
construction of permanent buildings in the 1970s, there were doubts in
some quarters regarding the enduring features of the material. In fact some
believed that over time the material would begin to crumble. However, as
of yet there is no sign as of fragmentation in any of the buildings in which
it was used. However, PTFE coated glass fiber fabric is not always favored.
Despite problems with its durability and the tendency for the material to
become easily dirty, there is a high demand for PVC coated fabric of
synthetic fibers as a membrane material due to its cheap rate of production
and the fact that it can be folded (Mewes, 1993).
Membrane structure design techniques are established on allowable unit
stress where the figure of 4.0 as a frequency is internally accepted as the
safety factor for a membrane material (Clough, 1995). Although this figure
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is not as safe as it could be, it is considered adequate as it takes into
consideration the potential decline in the strength of the membrane
material. This safety factor is very low and is possibly only accepted due to
the economical costs associated with this material. In the past damage has
occurred due to tearing in the membrane material. Such tears begun in
small specific areas of the material. In order to ensure adequate safety, the
design of the membranes must consider every detail (Berge, 2001).
Characteristics of Membrane Structures
1. Larger Span
In 1985 a tennis court with a height of 15m and 45.2m span was built in the
International Sports Expo in Japan. In the same year, The Calgary Stadium
was built in Canada, which is 36.5m in height, 112m in span and 11150 in
covered area. In 1988, the Tokyo Dome was built, which is 201m in span
and 56.19m in height. The Georgia Stadium built in Atlanta, US has a
major axis of 235m, has a minor axis of 186m and is 79.24m in total
height. Based on pertinent data, it is speculated that the larger the span of a
building, the better the application of membrane structure will embody itseconomy (Brown, 2001)
2. Beautiful design with fashion sense
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Membrane structures which break through the structural form of traditional
building, is easily manipulated into various types of shapes and is rich in
color. Therefore they are easily formed into night scenes with the
coordination of light. This brings modern beauty to people. What is more,
in combination with technological progress, membrane structures are
known for use in hi-tech modern buildings; the buildings in 21st century.
3. Reduce energy-consuming
Membrane material is relatively good in transmission of light. It has a light
transmittance of approximately 7% to 20%, thus full use can be made of
natural light. During the daytime, without any artificial lighting provided, it
can completely satisfy the needs of various athletic contests. In addition,
membrane material with a reflective index of light over 70% can form a
soft scattering of light in a room with sunlight in order to make people feel
comfortable and dreamlike.
4. Rapid construction speed
The tailoring of diaphragms, the manufacturing of steel cables, steel
structures etc. are finished in factories, and can be used in combination
with lower reinforced concrete structures or structural components. Only
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linkage, installment, positioning and stretch-drawing of steel cables, steel
structures and diaphragms are carried out on the construction site, thus the
installment of construction on site is relatively easy, quick and convenient.
5. Apparent economic benefits
Although, presently construction projects with a membrane structure
require an initial and once-off high investment, the daily maintenance cost
on this type ofstructure is negligible (hence the label free maintenancestructure). Thus, in the long-term, the economic benefits are quite
apparent. If this type of structure is applied to buildings with a super-large
span, more obvious advantages in price will be seen. The economic
advantages of membrane structure are positively proportional to the spatial
span of a building and the technical difficulties associated with
construction.
6. Safety and reliability
Membrane structures are light-weight and its earthquake resistance is
relatively good. Soft membrane structures can tolerate of a huge amount ofdisplacement and overall collapse of building is uncommon. In addition,
membrane material is generally a flame-retardant material. The fire hazard
is minimal.
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7. Easily made into a detachable structure, easy to transport, and can
be used for touring performances, exhibitions and etc.
For example, a music studio designed and made by a company in America,
covers an area of over 300m. However its dismantlement and re-installment
only takes six hours.
_
8. Broad scope of application
From the perspective of location, membrane structures are from Alaska to
Saudi Arabia. The scale of the structures range from small one-man tents
and garden pieces to large buildings that cover with thousands even
hundreds of thousands squared meters of area. Some have even imaged
conceived a small city make of membrane structures.
Basic Properties of Membrane Material of Building
1.Composition and Classification of Membrane Material
The development of membrane structures is closely related to research on
and the application of membrane structure. From early examples such as
PVC, PTFE to the later ones such as ETFE membrane material, the
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development and application of each new type of membrane material has
sharply impacted upon the development of membrane structures.
Contemporaneously, the application of construction membrane comprises
two categories of membrane; a coating fabric and a thermoplastic
compound.
2.Coating Fabric Membrane
Coating fabric membrane material is a type of composite material and isgenerally composed of a substrate, coating and surface course, shown in the
fig. 1. below. A substrate is weaved through various textile fibers which
determine the properties and structural mechanics of the membrane.
Coating and surface course can protect the substrate, and are designed to be
self-cleaning, protect against pollution, and durable. Examples of Common
coating fabric membrane materials include glass fiber membrane materials
made from Teflon coating (generally called PTFE membrane material) and
glass fiber membrane material made from PVC coating (generally called
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PVC membrane material).
Fig. 1. Compositions of Coating Fabric Membrane Material
PVC membrane material is cheap and is divided into several colors such as
white, red, blue and green. It is applied broadly. Soft membrane material
with good tensility is easy to make and to stretch, thus it is easily adaptable
to tailoring errors. However, its durability and self-cleaning properties are
poor. Its properties will change due to outward movement of the coating
mold-increasing agent and ultraviolet effects so that its surface gradually
turns yellow and sticky over time. Moreover, dust and dirt in air are
attached to membrane surfaces and stain the surface and thus reducing light
transmittance. Thus, its service life is decreased. In order to improve the
durability and self-cleaning of this type of membrane material, a PVF or
PVDF surface course can be added to the surface of coating.
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PTFE membrane material has good durability and does not turn yellow or
moldy in the atmospheric environment. Additionally, rainwater will flow
away after forming water drips on the surface as it has good self-cleaning
properties. However, PTFE membrane material is more expensive and is
stiffer. Thus, the folding &rolling of material during transportation and
construction can lower its strength, the convenience of construction of the
membrane material is poorer, and consequently refined calculations are
required during design and tailoring processes.
Substrates of membrane material are weaved into using glass fiber or
polyester fiber yarn. Glass fiber has a certain flexible capacity and a higher
elastic modulus and strength than polyester fiber, however it gradually
becomes smaller. Therefore it does not age well nor does it have a long
service life.
However, due to its brittleness, glass fiber should be processed precisely,
treated properly and carefully. It should be borne in mind that humid and
hot environments an impact on its mechanical property. Polyester fiber, on
the other hand, has a longer life, deformation and it is easy to install.
However, long-term tension and ultraviolet light will gradually result inruffles on the membrane surface. Perception and light transmittance are
both affected over time.
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Basic methods of weaving yarn into substrates of membrane material are
plain weave or panama weaves. Plain weave, also called as basket weave,
is a process that warps yarn tightly to be straight line while weft yarn
crosses upper and lower parts to bypass warp. Warp yarn is weaved
orthogonally at a right angle to weft yarn, shown in Fig. 2. Plain Weave has
several variations of method. For example, weft yarn can bypass a warp
yarn from below, then three warp yarns from top. When the knitting
tightness is relatively high, a substrate of plain weave with relatively high
tensile strength is easily treated directly by a liquid coating agent.However, more coating materials are needed when the thickness of the
substrate equals that of nearly three-layer fiber yarns. In contrast to plain
weave, several fiber yarns can be weaved one time, shown in Fig. 2a. As
shown in Fig. 2-2. And Fig. 2-3. Panama Weave weaves two or three yarns
at one time in the warp direction and the weft direction. When the same
fiber material yarns are adopted, membrane material made using the
Panama Weave can weave several yarns one time. Furthermore, its
mechanical properties are better than that weaved by single yarn in plain
weave.
a) Plain Weave b) Panama Weave
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Fig. 2a. Weaving Methods of Yarns in the Substrate of Fabric Membrane
Materials.
Common resin coating materials include PVC and PTFE. The earliest
application used was PVC which has relatively good flexibility and is easy
to process. However, it reacts poorly to ultraviolet light, thus chemical
changes are common following long-term exposure to sun. Furthermore, it
is a poor self-cleaning material. Therefore, membrane materials externally
coated with PVC are generally applied in temporary structures. However,PTFE is an inert material and thus does no react to exposure to ultraviolet
light. Furthermore, PTFE has a long life in terms of light transmission and
self-cleaning, fire-retardation. In addition, it is not flammable and its
opaque color (initially cream-colored) endures over a long period (25-
30years). Thus, it is commonly applied in permanent constructions.
3.Thermal Polymerization Compounds MembraneMaterials
Thermal Polymerization Compounds mainly refer to ethane-ETFE, and are
often applied in buildings with high light transmittance and rich models. Incomparison to coating fabric membrane materials, ETFE membrane
materials are lighter and thinner, and light transmittance reaches up to 95%,
and thickness is often smaller than 0.3mm (Kaltenbach, 2004). Although
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the strength of ETFE membrane material itself is high, its thickness leads to
common applications of the material in inflatable membrane structures.
These are structural entireties composed of several two-layer or three-layer
air mattress units with a span of usually not more than 5m.
4.Physical properties in building of building membrane properties
As a type of structural form with intensely artistic expressions, the higher
degree of physical building properties of membrane materials should alsosatisfy the needs of the membrane. Physical building properties include
several aspects such as weather resistance, optical property, acoustic
property, thermal property, and fire-resistance property. During the design
of membrane structures, the physical architectural properties of each type
of membrane material, in combination with the overall properties of
membrane structure should be fully understood. Proper materials should be
chosen to correspond to the designs in order to obtain optimal architectural,
economic and technical effects.
5.Weather resistance of membrane materials
Membrane material, as the covering system of building, is often directly
exposed to the external atmospheric environment. Thus it is affected by
natural phenomena such as daylight, temperature variation, rain wash and
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dust erosion. Thus, the appearance and color, brightness and strength of the
material all gradually deteriorate over time. The weather resistance of
membrane material is a comprehensive index that outlines its years of
service, its aging resistance, self-cleaning ability and intensity attenuation.
Coating materials such as PTFE and PVDF on the surface of membrane
material stem this process. Both are inert materials, thus their chemical
properties relating ultraviolet protection, aging resistance and corrosion
resistance are better than those of PVC coatings. In general, the serviceyear of a PVC membrane material with coated PVDF surface course is over
25 years while the service year of PVC membrane material with coated
PVDF surface course is 10 to 15 years. Therefore, membrane material can
be broadly used in permanent buildings (Kaltenbach, 2004).
At present, weather aging experiments are often undertaken to evaluate the
weather resistance of a membrane material. Generally speaking, tests
investigating the effect of natural climate aging and of artificial weathering
aging are conducted. Laboratory tests often adopt artificially accelerated
climate aging experiments, referred to as Xenon lamp aging experiment.
The light source of the xenon-arc lamp is adopted to continuouslyilluminate the membrane while temperature, humidity, radiant energy,
rainfall cycle and time are controlled to imitate and strengthen principal
environmental factors such as light, heat, oxygen, moisture and rainfall. In
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natural climate conditions the speed of aging of a sample and the
differences of a samples tensile strength underradiant energy over the
course of time is regarded as an indicator of weather resistance.
6.Optical property of membrane material
The optical properties of membrane material refer to of the effects of
membrane material on light of various different wave bands, including such
properties as reflection, transmission, absorption and scattering. Differentmembrane materials display large differences in reflection, absorption and
transmission of light in each wave band. In general, membrane material has
relatively good light transmission. Light transmittance of natural light of
fabric membrane material can reach 20%. However, in double-membrane
buildings, built in accordance with relatively high thermal heat-insulation
properties, light transmittance reaches 4% to 8%. However, the light
transmittance of ETFE can reach 95%, which exceeds that of clear glass
(Kaltenbach, 2004).
Inside membrane structure buildings transmission light produces uniformly
diffused light. The light has no shadow, no dazzle and no significantdirection, thus it is gentle and uniform. During daylight hours, it will satisfy
the light requirements of various indoor activities. Therefore, membrane
structures are especially applied to buildings that demand higher lighting
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specifications, such as sports facilities, exhibition halls and patios. In
addition, during the night, the surface of buildings with membrane
structures can give off a soft light, which can be advantageous in terms of
adverting and in increasing the ease with which buildings are identified.
When interior lighting is used, lamps should be kept at a proper distance
from membrane surface to prevent the heat given off by lamps from searing
the membrane surface.
7.Acoustic properties of membrane material
The acoustic properties of membrane material are similar to its optical
properties and include reflection (reverberation) and transmission loss
properties for the various frequencies of sound waves. Reverberation and
sound absorption properties comprehensively determine the quality of
audio and the soundproof properties of buildings with membrane
structures. Single-layer membrane material has poor acoustic properties
and can result in strong echoes and weak sound absorption. In addition its
soundproof volume is also lower than that of a general palisade structure.
With respect to the vibration of sound waves, membrane material fabrics
have very strong reflectivity which increases the noise level inside
buildings with membrane structures. Buildings with inner concave, in
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particular, such as air supported membrane structures or arch supported
membrane structures, the ceiling can collect the reflection of sound waves
to further impact upon the indoor acoustic environment. However, this
relatively poor sound insulation capacity determines that membrane
structures are not applied to building facilities that demand high noise
reduction.
In general, corresponding architectural measures need be taken to improve
the acoustic environment of buildings with membrane structure. Forexample, the addition of a light and poly-porous bottom cloth to the
membrane can effectively reduce reflection of sound wave and increase
attenuation of transmission of sound waves. Perhaps an acoustic screen
which is hung on the ceiling of membrane structure can increase the
absorption of sound waves. Changing the curved shape of ceiling so that
direction of reflection is changed will also have an impact. Furthermore,
specialized sound-absorption membrane lining can apparently lower
reverberation to increase sound absorption. This has produced good results
in the Georgia Dome and New Denver National Airport where such lining
has been applied. However, when choosing these technical solutions, we
must fully consider the impact of these methods on the performance of themembrane structure in relation to lighting, and fireproofing, for example.
8.Thermal properties of membrane materials
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The thermal insulation performance of buildings with membrane structures
is poor, and at present widely used membrane materials cannot limit the
impact of internal environment very well. The heat transfer coefficient of
single-layer membrane material is large, and refrigeration-consumption is
also high. Therefore, it is only applied to open buildings or in areas with
warmer climate.
When the thermal insulation property of a building is required to be high,
two-layer or multi-layer membrane structure can be adopted. In general,there should be a 25-30cm air buffer between two membranes.
Cold condensed dew inside the membrane surface is also a problem that
needs to be considered. When a membrane structure is applied to buildings
with larger sources of interior humidity such as swimming pool or a
botanical garden for example, damp air easily turns into dew on contact
with the internal surface of membrane. Therefore, measures such as indoor
ventilation, installation of a cold condensed water drain or air circulation
system should be taken.
9.Fireproofing performance of membrane material
Membrane has a good fireproofing performance. The substrate of
membrane material is itself non-inflammable or flame retardant. Glass fiber
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is non-combustible material while polyester fiber is non-flammable
material. When membrane material is applied in half-open buildings such
as the grandstand tent of stadium, the awning of public facilities and
architectural art sketches and in temporary structures fireproofing safety
need not be taken into consideration. However, when membrane material is
applied in a roof system of totally enclosed and permanent buildings, as the
fireproofing of a membrane material in terms of fire-proofing, smoke
volume, toxicity and structural collapse should be comprehensively
considered in order to judge its fire-proofing performance compared totraditional fire-resistant and fire-proofing methods. In enclosed buildings,
utilization of PVC membrane material simply cannot be denied.
After a fire is lit, PVC membrane material is burned through in the third
minute and twelfth second to form an open hole corresponding to the size
of contact surface of flame. Thanks to this hole, heat, smog and gas can be
automatically excluded. This open hole remains until the fire is
extinguished. Early occurrence of the hole results in the emission of heat &
smoke from the building and postpones the collapse of the steel structure,
which is beneficial for staff in public places as more time is given to
evacuate. In comparison, PTFE membrane material only crazes at the jointof membrane surface in the third minute and 35th second after fire is lit,
and finally comes off in chunks along the joint (Kaltenbach, 2004). It is
found from test analysis of interior membrane buildings that the volume of
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CO and CO2 from PTFE membrane material is at least over double that of
PVC membrane material. PTFE membrane material also produces the toxic
gas HF at a level that exceeds critical concentration while PVC membrane
material when burned through does not show evidence of HF. Therefore, it
is concluded that the fire-proofing performance of PTFE judged by
membrane material in accordance with certain standards does not conform
to the practical reaction of membrane structure under fire hazard; therefore
PVC membrane material is better (Kaltenbach, 2004).
Maintaining the stability of the framework of membrane structure in thecase of damage of membrane surface is one another noticeable issue
connected to the fireproofing of membrane structure. In a membrane
structure the membrane material is force-carrying material. Therefore,
regardless of whether the membrane material is burnt through or comes off,
it is always the first part to be damaged. When the membrane material loses
tension because it is damaged, the framework of membrane structure
should not collapse.
Study on the Mechanical Properties at the Joint
Node of the Membrane Structure
A. Basic Principles of Design for the Joint Nodes of
Membrane Structure
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The development of designs for membrane structure is the process in which
the overall design and a detailed design of membrane structure
simultaneously interactively influence each other and develop. The basic
function of the joint node of a membrane structure is to safely and reliably
connect each part of the membrane structure to make a whole. After 50
years of development, the current design of the joint nodes of membrane
structure need be beautifully designed, in addition to their basic functions
being realized (Motro, 1996).
B. Direct and brief force transmission paths can effectively transfer
internal force
Negative Gauss Hyperboloid produced by equalization of strain is a
necessary condition in which Tensional Membrane Structure keeps stable.
Brief design for the joint node can simply and specifically pass on complex
membrane surface and force is carried by angle points of the membrane to
other parts of the membrane structure so that there is a continuous
transmission of force flow in line with the analysis and design model.
C. Sufficient intensity, stability and durability
Intensity, stability and durability are basic mechanical properties that all
building structures must satisfy. With respect to membrane structure,
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sufficient node mechanical property an important factor that guarantees the
overall performance of the structure. In terms of the design of joint nodes,
we must consider the possible reduction of the joint node property that may
be caused by local stress concentrations and a weakening of the membrane
material at the joint point so that the mechanical property of the
membranes joint point can be evaluated accurately.
D. Necessary harmony of deformation
In comparison to traditional building structures, membrane structures can
produce large deformations under the impact of external loads. In each
phase of design of the membrane structure, the large deformation property
of the membrane structure must be considered. With respect to the design
of joint points, a certain amount of displacement and rotation must be
permitted in order to guarantee accurate positioning. Meanwhile, we must
also consider the operability on construction of pre-stretch-drawings of
membrane material and twice stretch-drawings.
E. Integrity of architectural appearance
The strong expressive force that membrane structures offer is one of its
principal advantages. Once its mechanical properties are met, the joint
point should be as exquisite and small as possible in order to be in line with
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the overall geometric modeling and architectural appearance of the
membrane structure. The impact of joint point on light transmission, gas
tightness, water tightness and water draining must also be considered.
F. Basic forms of membrane structure to link joint point
The specific forms of joint points of membrane structures are complex.
Moreover, according to the effects and connection of membrane unit, they
can be divided into three basic forms: membrane to membrane, membraneto rigid edge and membrane to soft edge.
G. Membrane to membrane joint point
The main functions of membrane-membrane joint points are to weave
various cutting units of a diaphragm into the whole diaphragm, with
necessary diaphragms added to reinforce it. Basic forms of membrane-
membrane joint points include heat seals, splints, bonding, sutures, belt and
combination mode. Presently, the first three of these forms of membrane-
membrane joint point s are most commonly used engineering project.
Common forms of thermal bonding membrane joint points include lapping,
single-side back sticking and double-side back sticking, shown in Fig. 3.
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Thermal bonding methods include high frequency heat seals, hot air heat
seals and the use of hot soldering irons. Thermal bonding membrane joint
points fuse through membrane coating and shear transfer force, and the
diaphragm a carries uniform and continuous force, thus its joint strength is
strongly related to heat seal form, heat seal method and lap width. For PVC
membrane material, considering the solder ability of PVC coating and
waterproofing requirements, the most commonly used thermal bonding
PVC membrane joint point at present is the single-sided back sticking form
shown in Fig. 3(b), where the covering diaphragm is located in the innerside of the membrane structure. For PTFE and
ETFE membrane material, overlap joints shown in Fig. 5.3(a) is a relatively
commonly used membrane to membrane joint point (Kaltenbach, 2004).
Fig. 3. Thermal Bonding Membrane Joint Point
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A splint membrane joint point is shown in Fig. 4. In the procedure one
screws the bolt tight, clamps two rigid splints and two diaphragms in the
middle tight, and passes on the internal force of the diaphragm from the
bolt-rope of the diaphragm and the rigid splint through friction and
extruding force. Determination of the length of the rigid splint depends on
the size of curvature of the membrane to membrane connecting line. Splint
membrane joint point is often applied in field installations of large
membrane units to avoid the inconvenience of processing plants. Moreover,the connection of single-side splint also fits that of the membrane unit and
the steel boundary components (Kaltenbach, 2004).
Fig. 4. Splint Membrane Joint Point
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Transfer force connecting splints mainly focus on the extruding force
between the bolt-rope and the splint. The clamp force and the individual
stiffness of the splint are large enough so that the bolt-rope and the splint of
the diaphragm can rely on the transfer force to avoid the phenomenon in
which the bolt-rope of diaphragm squeezes into splints. Splint connection
does not rely on the screw bolt and the shear of diaphragm to transfer force.
Therefore, the open size of the membrane should be 2-3cm larger than the
screw bolt so that tearing damage from shear stress between the diaphragm
and the screw bolt in the open hole can be avoided.
Bonding membrane joint points, whose two pieces of membrane units are
bonded together by a special glue water and adhesive, transfers the force
through the bonding of the membranes coating. This form of joint point is
in line with that of the thermal bonding membrane joint point, shown in
Fig. 5. However, bonding membrane joint point is time-consuming, costly
and its quality is not easy to ensure, therefore it is commonly applied in
such cases as field repair of the membrane structure and in the installation
of twice membrane.
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Fig. 5. Bonding Membrane Joint Point
H. Membrane-rigid boundary joint point
Membrane-rigid boundary joint point is applied in connection with the
supporting part between the membrane unit and the membrane structure,such as steel structures, aluminum alloy structures, concrete and timer
structures. In essence, the membrane unit directly connects with the metal
components through specialized metal adapting pieces. At present,
common membrane-rigid boundary joint point are pressing plate
connections, U-style clip connections and metal fastening connections. A
pressing plate connection is shown in Fig. 6. It is almost in line with a
pressing plate membrane-membrane joint point in structure and force-
transfer mechanism. The friction from the clamping of the pressing plate
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and the extruding force between the bolt-rope and the pressing plate passes
on the internal force of membrane to surrounding components.
(a) Membrane-wood structural rigid (b) Membrane-steel structural
rigid joint point joint point
Fig. 6. Pressing Plate Junctional Membrane-rigid Boundary Joint Point
The u-type clip connection method withdraws the edge of the membrane
through the pressing plate and the bolt-rope first, and then it is connected to
the surrounding components through the U-type clip arranged at
proportionate space, shown in Fig. 7. The internal force of the U-type clip
fits the adjustment of membrane boundary and twice the lead-in of
membrane stress.
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Fig. 7. U-type clip connecting membrane-rigid boundary joint point
I. Membrane-flexible boundary joint point
The membrane-flexible boundary joint point mainly refers to various jointpoints connected to flexible cable unit that includes membrane cover
connection, U-type clip, and belt, shown in Fig. 8.
The membrane cover connection refers to the cable body that passes
through the membrane cover formed by the membrane surface, and its
internal force is passed on to the membrane cover from the membrane unit,
then on to the cable unit. Meanwhile, joint points are continuous, and the
transfer of force is uniform. The membrane cover can be formed by a direct
reversal of the membrane material once through the thermal bonding
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method, and is also formed by the addition of a membrane cover. The joint
strength of the membrane cover connection mainly depends on the width of
the membrane cover created by a heat seal, which is similar to the thermal
bonding membrane-membrane joint point. In comparison, a U-type clip
connection fits the condition in which the diameter of a cable body is long
and when force-carrying is large, and its connection mode is similar to that
of a U-type clip with rigid boundary.
Fig. 8. Membrane-flexible boundary joint point
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Philosophy, engineering and material
A membrane-structure building is a building in which active use is made
of the characteristics of membrane materials. Membrane materialscommonly used nowadays are PVC coated polyester, PTFE coated glass
fiber fabrics and recently a third material: ETFE-foil.
Hence the name fabric structures or fabric architecture is sometimes
encountered in literature.
The structure supporting the membrane can be a skeleton frame or a cable
frame. If the membrane itself is used as a structural material, the structure
can only be small in scale because of the limited strength. In a large-scalestructure, the membrane must be reinforced in some way or combined with
a frame. A membrane naturally forms a curved surface and can resist
tension but not compression or bending. This is the reason why membrane
structures are often put under the heading of tensile structures.
Lightweight, thin and soft are some of the main characteristics of
membrane structures, mostly enveloping large spaces by curved shapes.
Another important characteristic of membrane building is the fact that the
inherent architectural language of membranes isinvariably
morphologically independent of the historical, geographical, architectural
andsocial context into which they are introduced. In this respect they can
represent a neutralintervention whilst still possessing their own strong
architectural identity. (Koch, 2004)
As mention earlier on Modern membrane structures were first developed
in Germany, where their basic properties, structural characteristics and
design methods were elucidated and their formal potential wassystematically investigated. These structures were first called tent
structures, but now the most common name is membrane structures.
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Form, structure and design
The concept
To obtain an understanding of a structural form tracing the flow of tensionand compression forces throughout its elements is essential. Bending
elements, or beams, are the most common structural elements for simple
structures. The simplest structural elements are those in which load is
carried by a single element, where the extremes are the suspended cable in
pure tension or an arch in pure compression.
These are both two-dimensional, but if these systems move into three
dimensions it gets more complicated. The simple (catenary) cable will then
become a bidirectional cable net (just as the arch becomes a bidirectionalgrid shell). This net may then be triangulated and finally developed into
woven and coated structural fabric. At each stage, load is carried in tension
alone.
Since for both structural concepts the material will be thin the generated
stresses can be referred to as membrane stresses. In this respect, both
systems can be referred to as membrane structures for their load-carrying
mechanism. In this thesis only membrane structures will be discussed
which also refer to their construction material/foil.
The ability of a membrane to carry load is increased by the introduction of
curvature to the surface. The amount of deflection under load is controlled
by both the degree of curvature and the amount of permanent stress, or pre-
stress, in the membrane. Two fundamental classes can be distinguished for
membrane shapes, those with negative and those with positive surface
curvature: anticlastic and synclastic respectively (fig. 9.) The first class are
the hyperbolic paraboloid (4-point sail), the simple saddle and the cone andthey all exhibit negative Gaussian curvature. The second class contain for
example domes where the curvature is the same in all directions and the
stabilisation should be realized by permanent internal inflation pressure.
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Fig. 9. Negative and positive surface curvature [1]
Two basic components can be distinguished in membrane structures: the
membrane itself and the support structure. The membrane may be
connected directly to the support structure or via edge-cables. The support
structure transmits the tension forces from the membrane to the ground.
When the supporting structure is rigid, both systems may be structurallyanalyzed separately. When a flexible boundary is applied this is not the
case.
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Primary structures
Membrane structures can have an analogy of skin and bone, with the
bones performing the primary and the skin the secondary load-bearing
functions. The primary structure meant here is the earlier mentionedsupport structure. Four basic primary structures can be distinguished with a
fifth membrane type structure. The simple Saddle, the arch-supported
structures, point or mast supports, the ridge-and-valley principle and the
fifth group the air-supported structures.
Arch-supported structures
Membrane saddle areas are created between the support lines along
the arch members when applied correctly. The arch functions as aLoad-bearing element subjected only to compression. The membrane is
then subjected to purely tension stresses.
Arch-supported structures are suited for large-scale structures, where big
spans should be reached and an appropriate geometry should be provided
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for the membrane (e.g. Hangar in Brand). Other constructions are suited as
well, namely spoked-wheel constructions, cable nets and mast structures
(e.g. Millennium Dome).
Mast supported structures
A minimal type of structure in this category can be achieved by a single
supporting mast with appropriate cable stay (and three other anchor points
may be on the ground). With this a cone structure can be created, which
can also be put in a row. Another separation within this type can be made
when no mast/support is wanted on the ground area. The flying mast is
introduced with a supporting structure above the membrane (figure 10).
Fig.10 Flying mast example [1]
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Ridge-and-valley support structuresThis principle is based on setting out cables with opposite curvatures next
to each other. The upper cable is called the ridge-cable and the lower thevalley-cable.
Air-supported structures
This type of structure is different because the supporting element of the
membrane is air. The system is based on air pressure between the ground
and the membrane (figure 11). Incorporating a support ring that is capable
of resisting horizontal loads, can create dome forms.
In these domes, again, a higher pressure is maintained in the entireinternal
space.
From time to time, helium-filled pneumatic structures in the form ofcushions are investigated, such as the Cargolifter (airship hangar). In
general, inflated structures are being used more and more as secondary
systems for smaller spans. Here, high-transparency foils
(ETFE) are used for many types of cushion.
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Another type resulted from this, the so-called air-supported linear elements
such as inflated arches or even beams.
Fig.11. Pneumatic dome example [1]
Retractable structures
Membrane structures especially designed for roofs are required to change
form. The most common way for membranes is to fold the skin and
packing it together. Distinction can be made between retractable structures
with a radial system, parallel sliding-folding structures, umbrella structuresand sliding roof elements.
Membrane Engineering
Many of the concepts for the form finding, analysis and design of
lightweight and long span structures originated from the observation of
structures in nature and from physical modeling techniques. The latter
principally through work at the Institute for LightweightStructures (IL), Stuttgart University directed by Frei Otto [3] (Appendix
4A). The engineering science was aided by SFB64 (1976-84), the first
special research group, directed by Leonhardt, Argyris, Linkwitz, Otto and
others at the University of Stuttgart [4, 5].
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SFB64 pulled together all the technology, design method and material
science that was necessary to successfully design and construct the
Olympic Stadium at Munich [6]. Argyris and Haug outlined the
background to the development of matrix based numerical methods for the
analysis of tension structures.Membrane engineering covers the numerical procedures for the form-
finding, load analysis and patterning of these stressed-membrane tensile,
non-linear structures. Any analysis must account for relatively large
displacements since membrane structures undergo significant surface
movement in order to carry load. Accurate fabrication information for the
membrane, cables and support structure must be provided to the contractor.
Physical and numerical modeling
Early developments in tensile architecture were based upon physical
models using soap films (for minimal surfaces), stretch fabric and wire,
done by Otto, Gaud, Happold, Arupet al. Very accurate physical models
were created to derive to cutting patterns. Physical models are still used
today (during conceptual design stages), but the principal design stages of
form finding, load analysis and patterning are done by the use of
computers.
The computer-based numerical modeling of structures is based upon the
finite element method. The geometry is presented by a series of points and
finite beams (or masts) between them, covered by fabric modelled by
triangular elements with each three connecting points. From this the
element stiffness matrices are assembled, but since membrane structures
have additional on-off non-linearitys (slacking cables and wrinkling
membrane as a result), determining the equilibrium state of membrane
structures needs form-finding capabilities that does not exist in standard
structural analysis systems.
Form-finding
Goal is to create a satisfactory long-term behaviour of a membrane
structure, done by creating either a uniform or smoothly varying
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distribution of stress within the warp and fill (or weft) directions of the
fibres. These fabric-weave directions, in the end, should ideally coincide
with the directions of the principal curvatures of the surface.
In practice an iterative process of form generation (finding) and load
analysis is undertaken, which is done by computer programs. It is farbeyond the scope of this assignment to discuss the exact process
undertaken by designer and his/her computer program.
Load analysis
After introducing the material properties above load analysis (self-weight,
snow, wind) can be started. Now the non-linear behaviour of the structure
under load is analyzed using the finite element model from earlier. As saidbefore, the final form of the structure will be developed through an iterative
cycle of form adjustments and load analysis (figure 12).
Fig.12.Load analysis of a saddle shaped roof [1]
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Cutting patterns
After the form finding and load analysis stage, it is needed to translate the
found form into realizable pieces (after the pattern orientation). These
pieces are so-called cutting patterns. The curved (and usually doublecurved) membrane cannot be build up from flat planes easily. It is done, by
the computer program, by the geometric unfolding of a set of sequential
triangular finite elements into a plane.
The way then to develop cutting patterns with computer programs is to
introduce deformation and compensation for the cutting patterns (figure
13). The use of geodesic seam trajectories helps to optimize the use of
material by providing a set of balanced patterns with equal material anglesand thus preventing banana-shaped patterns.
Fig 13 Cutting pattern generation and Compensation [1]
Details
The details, such as anchorage, are of importance for this thesis in such a
way that the extent, in which the sealing of the entire space is facilitated, is
relevant for the sound insulation as well as for room acoustics. But since
the main focus of this thesis will be on sound insulation, all connections
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should be carried out in such a way that no sounds leaks appear. For triple-
layer membrane detailing, please refer to figure 14.
Seams
The connection between the different pieces of membrane (cutting patterns)
is usually made by seams formed in a double overlap. Glueing is also
possible; however, the available methods often offer not enough weather
resistance. When the surface layers (coatings) are made from PVC, the
connection can also be made by welding. In the factory multiple cutting
patterns are connected using seams and these bigger pieces are then
connected on the construction site. These seams give different detailing.
For detailing, please refer to figure 14.
Anchorage to the ground
Most of the examples seen in this chapter are of open roofing and small
canopies. These membrane structures are not relevant to this thesis,
because sound energy will leave (or enter) the structure at the open gaps
around the membrane. What relevant is here, is the sound tight connection
with the ground. Please refer to figure 14 for detailing on this matter.
Four details for a normal triple-leaf membrane structure. 1) membrane itself(including seams)
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,2) connection between membrane and the supporting mast, 3) connection between
membrane roof and membrane wall, 4) connection between membrane and asupporting (neighboring) structure.
The material
The Latin word membrane means a parchment or skin [7, 8]. The
membrane has a tradition of thousands of years old, but only in the last
decades membrane construction plastics became important. A membrane is
a flexible building component that is stabilized only under tension. So its
mechanical tensile strength and elastic qualities are important for the
design. Up to the present about 90% of all membrane projects used one of
the three following kinds:
- PTFE (polytetrafluorethylene)-coated glass fibre,
- PVC (polyvinylchloride)-coated polyester fabric, and
- ETFE (ethylenetetrafluorethylene)-foil.
Reason for this is that they have successfully been used in the past and so
they are extensively tested and proved. ETFE-foil for instance is a
transparent and high-performance foil mainly used for pneumatic cushions.
Today for each of these materials different strengths can be produced andthe properties are expanded to the higher requirements in regard to energy,
low-emissivity, translucency, fire safety and sound absorption and
transmission.
One example of this new development is the membrane roof of the New
Bangkok International airport (figure15). More is described in the
preceding chapter. In the following sections most of the materials used in
practice will be discussed and categorized.
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Fig. 15 Bangkok International Airport roof system and model photo [1]
Material types, qualities and characteristics
Products used for membranes may be divided into two main groups [8]:
anisotropic and those at least an approximate of isotropic materials. The
latter have identical mechanical properties in both main directions and are
mainly thin thermoplastic skins, or more rarely metallic sheeting, in the
building industry. Anisotropic membranes can be seen as technicaltextiles or fabrics. These fabrics may then be divided into three main
groups according to their manufacturing: knitted, woven and non-woven
(fleece, layered fibres). Woven fabrics consist of threads, which each
consist of several hundred individual fibres. The fibres may be natural
(cotton, silk, hemp or flax), mineral, metallic or synthetic.
During the industrial production process of high-quality membrane
materials the yarn (long continuous length of interlocked fibres) used for
the fabric is twisted in the weaving mill, using bond types specific to the
product. The direction of the fibres along the long length of a roll ofmaterial is known as the warp direction, while the perpendicular direction
across the roll is the weft (or fills) direction. Two weaving techniques are
used for membrane structures: the basket weave (warp/weft thread is 1/1)
or the Panama weave (2/2 or 3/3). For uncoated fabrics this is the end
result.
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When coated products are wanted, after a series of further pre-treatments
the raw fabric is coated on both sides with for example PVC, PTFE or
silicone. When coated extremely careful and not overlapping the seams of
the coating and the base material, higher strengths then the material itself
can be reached. The coating protects the fabric; against for examplemoisture and UV light, and ensures an accordingly long life. Coatings
presently on the market are PTFE, ETFE, TFA/PFA, THV, FEB and
PVDF, but are better known through their trade names such as Teflon,
Hostaflon, Polyflon, Toyoflon or Tedlar.
For external use only foils made on a fluoropolymer basis can be applied
successfully made for example of ETFE. An extrusion process ensures high
quality, consistent material thickness and maximum transparency. These
are sometimes brought under the heading of fluoroplastic foils.One of the most important criteria for the variety of materials available
today is the protection against the elements. Three main groups can be
distinguished from the text above
[1]: water tight (closed or coated), water permeable (open or uncoated)
materials and foils. All groups can be used internally, but for the open
materials to be used externally they must be weatherproof; i.e. for
protection against the sun for example. Both groups are discussed here,
since both types of materials are used for multi-layered systems.
Closed / coated materials
Two main products, already seen above, can be distinguished: PVC-coated
polyesters and PTFE-coated glass fabrics (other groups are PVC-coated
glass fibre and silicone-coated glass fibre). The PVC-coated polyesters are
low flammable and can have different surface finishes, such as
fluoropolymer top-coat. This type is in particular resistant against crackingduring folding. Another surface top-coat is laminated Tedlar film, which
provides good protection against UV-light (figure 16-1). The PTFE-coated
glass fabrics have a long life expectancy, are incombustible and have a low
coefficient of adhesion which provides them with good self-cleaning
capabilities (figure 16-2.1 and 2.2).
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In the fluoropolymer coated glass fabrics, in contrast to PTFE-coated glass
fabric, material is offered which can be printed and PTFE-laminated glass
fabric is under development which is not coated but laminated on both
sides with transparent fluoropolymer film for better translucency (figure
16-3).A new development recently is the highly translucent material on a purely
PTFE basis, which after a special coating can be welded and is rainproof
(figure 16-4). Silicone-coated glass fabric is an inexpensive alternative for
PTFE-glass and its main characteristic is its resistance to soiling (figure 16-
5.1 and 5.2).
Three foils are normally used, namely ETFE foil, THV foil and PVC foil.
ETFE foil is mostly used as double layer system in pneumatic structures
(and cushions). Advantages are the low self weight, full recyclability, highlevel of UV translucency and a self-cleaning surface with different
printings (figure 16-6 and 7).
Open / uncoated materials
The first groups are the uncoated or impregnated narrow or broad mesh
fabrics. PTFE fabric (one of the fluoropolymer fabrics) still dominates this
group and is used for the more exclusive projects (figure 16-8). Cotton
fabrics and (woven) metal fabrics are not less behind the PTFE fabric. For
textile suspended ceilings PTFE-coated glass lattice fabric (figure 16-9) can
be used.
Another group are the monofil fabrics made of fluoroplastic which are
produced with or without coating. They have excellent weatherproof
qualities and allow pleasant diffused light and have a high resistance to
soiling (and are expensive) (figure 16-10).
Micro-perforated acoustic membranes can be produced in the form of
textiles and also as perforated transparent foils with very good acousticabsorbency values [1]. An example
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1 2.1
2.2 3
4 5.1
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5,2 6
7 8
9 10
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11 12
Fig. 16Different kind of membrane materials [1]
1 PVC-coated polyester
2.1 PTFE-coated glass fibre fabric2.2 PTFE-coated glass fibre fabric - light3 PTFE (fluoropolymer)-laminated glass fibre
4 PTFE fabric5.1 Silicone-coated glass fabric - light
5.2 Silicone-coated glass fabric6 ETFE-foil
7 ETFE-foil with printing
8 PTFE (fluoropolymer) fabric
9 PTFE-coated glass lattice fabric
10 Fluoropolymer monofil fabric11 Micro-perforated membrane(polycarbonate- or ETFE-foil)
12 Acoustic polyester fabric
is the micro-perforated foil made from polycarbonate- or ETFE-foil. These
have excellent absorption qualities, according to [1], and are used more and
more, so that the improvement of the acoustic environment is less
expensive afterwards (figure 16-11).
Then there is the groups of uncoated or impregnated narrow or broad
weave fabrics (e.g. incombustible glass fabrics) and can be produced in a
wide range of characteristics, optimizing lighting and acoustics. Another
example is the polyester fabrics groups which can be seen in figure 16-12.
Properties overview
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In table 1 all relevant properties (known so far) per material type are
summed up. Only properties relevant to the subject of this thesis are
presented. Since sustainability and durability are always an important issue
nowadays this is also mentioned. Whether or not the materials arerainproof, fire resistant, UV-light resistant, translucent, light reflective,
self-cleaning, resistant to chemicals or suitable for folding membranes are
left out of the table. These can be found in [1, 8].
Properties and qualities mentioned in the table are sustainability,
recyclability, durability, self weight, total thickness, Youngs modulus
(elasticity) and tensile strength.
Values for sound insulation and absorption are scarse and not complete,
which are therefore not mentioned in table1.Most of these properties are not well documented. Or just not known (yet).
The bending stiffness is so far unknown, it can only be said that it is very
low. For permeability (applies only to meshes in practice) the flow
resistance is sometimes mentioned and is of importance later on (Moulder
and Merrill said that when a membrane is coated, it is impermeable, thus
the airflow resistanceR is infinite).
Manufacturers and producers
Producers and manufacturers producing membrane materials do this under
a brand name usually. Brand names Mehlers Valmex or Ferraris
Prcontraint series. Fabric types are also better known for their brand
names, like Teflon, Kevlar, etc. Some of the most seen manufacturers are
Ferrari Industry, Mehler Tex-nologies (coated fabrics), Verseidag
Technologies (coating and composite technology) and Heytex.
Since most materials on the market are common types, described earlier,
differ in strength, thickness, UV-resistance, the ability to self-cleaning,colour, etc., only some are interesting for this thesis. Table1 is
supplemented by the values found at the manufacturers(Heytex, Verseidag,
Mehler and Ferrari).
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Table 1 Material properties Recyclability: ++ is excellent,+ is good, 0 is neutral
*Polyester fibre itself has a Youngs modulus of 7.5 kN/mm2 and Aramide fibres112kN/mm2.
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Other special materials
Thermal insulation materials play an important role in the building
industry. Recently transparent thermal insulation materials for multi-
layered systems are produced and used effectively (figure 17-2).Stainless steel mesh materials have acquired an importance since the 1980s
and can be produced in a lot of different ways (different wires, cables and
weaving methods) (figure 17-3).
Gas-tight membrane materials (as analogy to glass products) have been
used in the area of helium filled membrane constructions for airships and
experimental studies. It encompasses polyurethane-coated, low-
flammability and light polyester fabric. The loss of helium is minimized
but materials that are completely impervious to helium are not yetavailable. PVC-coated aramide fibre fabrics are made from one of the
strongest synthetic fibres (Aramide or aromatic polyamide) on the market
today (with a maximum failing strength of 24.500 N/5cm). These fabrics
will be chosen when strength is important and where elasticity and
translucency of less importance. Also from Aramide fibres comes the
Kevlar fabric (usually with a PVC coating) which is more and more used
(especially for experimental use) as Kevlar fibre Air Tubes. As mentioned
before, these high pressure air tubes can take on the support function of a
beam, an arch, or a grid becoming a type of frame structure. Teflon
(PTFE)-coated glass-fibre fabrics and a variety of special coatings were
specifically developed to provide fire resistance, self cleansing, durability
and can withstand a tremendous temperature difference. This came from
the space industry, just like Spectra vibers, which consists of Vectran, a
high performance thermoplastic yarn spun from liquid crystal polymers.
Tenara is a woven Teflon fabric probably best known from the dental floss
fibres. It has the drape and feel of fine silk, withstanding continuously
folding and unfolding without fatiguing the yarns and is manufactured byGoreTex.
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1 2
3Fig. 4.8Different kind of special membrane materials [1]
1 Fluoropolymer-coated low-e acoustic glass fabric
2 Membrane insulation material
3 Stainless steel mesh
Project examples
1.Case San Nicola StadiumBari, Italy, 1990
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In 1990, World Cup was held in Italy and the country has built eight
stadiums to accommodate the event. This is one out of the eight stadiums
for the event. By rearranging the spectators seats within the stadium using
310 crescent shaped concrete beams, an oval shaped is eventually formed.
It is split into different segments and one such segment consists of 26 largepetals located in the upper deck.
The building does not longer feels so heavy on the eyes as slits were in
placed between the petals.
This also demonstrates the circulation areas, accommodating all the entries
and exits doorways thus it meets the health and safety requirements.
Computer simulations were used beforehand in order to maintain the
aesthetic side of the stadium.
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A special glass coated with PTFE fibre roof, designed by Over Arup &
Partners were used in order to protect the spectators of the outdoor weather
conditions. There are two levels to this roof; the principal level consists of
box shaped beams built from the top.
The second level consists of supporting beams for floodlights and trussmade using steel and cables. This method of build has ensured tension
within the whole structure. Bristol University has assisted in the project by
using computer simulation to monitor the wind flow ofthe stadium. Arups
computer programs such as Fablon and General Structural Analysis
program were used to create the simulation.
This was vigorously tested to ensure the wind does not have an unwelcome
affect to the spectators.
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