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7/24/2019 Guide to Fixings for GRC Cladding
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GUIDE
TO
FIXINGS
FOR
GLASSFIBRE
REINFORCED
CONCRETE
CLADDING
Administration
cl0 The Concrete Society
Century House, Telford Avenue
Crowthome RG45 6YS
United Kingdom
Tel: +44
0)
1344 466007
Fax
+44 0) 1344 466008
concsoc@concrete.org.uk
Advisory
Service
26 Gorsey Brow
Billinge, Wigan W N 5 7NX
United Kingdom
Tel: +44
0)
1744 893423
Fax:
+44
0)
1744 892359
rfeny.grca@dial.pipex.com
GRC
GRC
GRC
GRC
GRC
GRC
GRC
GRC
GRC
GRC
GRC
GRC
GRC
GRC
FIXING GUIDE
so110
October 1998. Revised November 1999
International
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Contents
1. Introduction 1
2
Functions o f Fixings 2
3. Design Principles
3
3.1. Overview 3
3.2. Positioning of Fixings 4
3.3.
Allowing
for
Movements 6
3.3.1. Principles of Fixing 6
3.3.2. Shrinkage and Moisture Movements
of
GRC
3.3.3. Thermal Movements of GRC
9
3.3.4. Movements
of
Support Structure
8
10
3.4. GRC Stud Frame Construction 12
4. T y p e s of Fixings 16
4.1. Fixings into GRC 16
4.2. Fixings to Support Structure 19
5
Tolerances
21
5.1. Introduction 21
5.2. Adjustments 21
5.2.1. Angle Support Brackets 21
5.2.2. Restraint Fixings 29
5.2.3. GRC Stud Frame Cladding
33
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6. Fixings
for
Lifting/Handling 34
7. Materials and Durability 37
7.1. Galvanised Fixings 37
7.2. Stainless Steel Fixings 37
7.3. Other Metals 39
7.4. Galvanic Corrosion 40
7 5 Crevice Corrosion
42
7.6. Stress Corrosion Cracking 42
8.
Typical Examples
43
I.
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1.
Introduction
Glass reinforced cement (GR C) is a compo site material comprising a
mixture of hydraulic ceme nt, silica sand, alkali resistant (AR ) glass
fibres and water. Th e glass fibres effectively reinforce the mortar mix
thereby improving its tensile and flexural characteristics.
GRC is a p articularly attractive and durab le cladding material. I t can
be moulded into a wide variety of comp lex shapes and profiles and is
ideally suited to the pop ular fast-track approach o f using lightweight,
prefabricated cladding pane ls for the exteriors of mo dem buildings.
The main advantage
of
GR C panels over the corresponding precast
concrete alternatives
is
the considerable saving in weight. Th is results
in significant sav ings in the costs of transportation, handling and
erection of the panels. If this weight advan tage is considered at the
design stage, it should be possible to effect substantial econom ies in
the design of foundations and superstructures
for
high rise building
constructions. Other notable advantages of GRC cladding are its
durability, chem ical resistance, non-combustibility and go od sound
heat insulation properties.
This publication
is
intended to explain and illustrate acceptable
methods of fixing GR C panels to a building or other structure and
providing fixings for Iiftinghand ling. The basic principles
of
design are
outlined and related to the p racticabilities of ensuring adequ ate
tolerances to allow for erection and the subsequent, comb ined
move ments of the panels and supporting structure. Illustrations of
several different types o f fixings that are in comm on use are given,
together with informa tion abou t the materials used to manu facture
them. Particular reference is made to the need to isolate materials
which might give rise to galvanic corrosion if they were allowed to be
in direct contact with each other. General details of the widely used
GR C stud frame type of construction are also illustrated, together
with recommendations on how to fix the GR C facing
to
the stud frame
Finally, d etails of several fixing sys tems are presented
to
illustrate
typical examp les of securing GRC cladd ing panels to the supporting
structures. The y are not presented in any particular orde r and are only
intended
to
give general guidance.
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2.
Functions
of Fixings
The main functions of fixings for GR C cladding panels are
as
follows:
a.
b.
joints.
C.
d.
e.
f.
CT
b
. .
to secure the cladding panels to the building for the life of the
panels a n d o r building.
to allow translational and rotational movem ents to occur
between individual panels and between the panel(s) and
supporting structure whilst maintaining w aterproofing at the
to provide sufficient adjustment to accomm odate normal
constructional inaccu racies in combina tion with the anticipated
move ments referred to in (b) above.
to maintain integrity of suppo rt and restraint under all
conditions o f exposure (imp act, vibration, wind, fire, etc.) by
minimising local concentrations of stress in the GR C.
to provide lifting points for the cladding during manufacture,
handling and erection.
to ensure that force s transmitted through the fixings are
distributed ov er as wide an area o f GR C a s possible.
Fiuings
for
liyting
should
have F
of S
of at
least
8 to 10
to utilise th e full strength properties of the GR C by providing
supp orts at the base o f the panels and lateral restraints at both
the top and bottom o f the panels.
Th e movem ents in (b) above can be difficult to quantify. H owever. it
should be possible
to
make conserva tive estimates of the magn itudes
and directions of these move ments for the purposes of designing the
fixings and join t sealants.
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3.
3.1
Design Principles
Overview
In order to prod uce a safe, efficient and econom ic fixing system, it is
necessary to understand the basic design principles and criteria.
Th e designer sho uld first identify any constraints which might be
imposed by cond itions on site. Such constraints, if any, may have a
significant influence o n the choic e and detailed design of the fixings.
Typical exam ples of these constraints are problems a ssociated with
access, conflict with fixings for other elements, excessive
misalignments of support elements and conformance to a demanding
programme o f works.
GR C panels shou ld not be over-fixed to the structure as this will
inhibit moisture and thermal m ovem ents and is likely to result in
detrimental cracking
of
the panels. Fixings are usually provided at
each of the four corn er points of the panels.
Th e structural behaviour of the G RC panels under load should be
carefully exam ined. It is advisable to avoid long horizontal panels
(with sp d d e p t h ra tio >4) s bending can cause distress of the GRC in
the vicinity of the fixings du e to rotational and/or translational
movements.
Fixings should also be positioned so as
to
minimise any permanent
stresses which m ight be induced into the panels. Forces transmitted
through the fixings should be distributed over as wide an are a of GRC
as possible. Ad equa te bearing areas must also be provided for the
GR C on the su ppo rts at the base of the panels to avoid distress to the
GRC.
BS 5606:
1990
and BRE Digests 199 and 223 contain important
information abou t inaccuracies to be considered in the design of the
fixings. Adeq uate tolerances must be incorporated into the fixing
system if
i t
is to perform func tions (b) and (c) listed in Section 2.
Ideally, all fixing s should be easily accessible for adjustmen t although
this is not alw ays possible.
I t
is important to remem ber that galvanised fixing comp one nts have a
finite life which is directly proportional to the thickness of the zinc
coating. As
a
general rule, stainless steel fixings should be used
whenever possible because of their high resistance to corrosion.
Stainless steel is an obvious ch oice of material for fixings which are
unavoidably inaccessible (positioned out of sight).
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Separate
fisings
should be provided for lifting/ handling purposes to
avoid possible damage to the perm anent fixings.
The total costs
of
fixings should be considered in the context
of
the
simple balancing equation
Total Cost
of
Fixings
=
MateriaVFabrication Cost s +
Costs of Installation
An increase in materiay fabrication costs , associated with the use of
more expensive an d sophisticated fixings, can be balanced against the
reduction in costs of installation resulting from s avings in tim e on site.
This point should be borne in mind when choosing the type of fixing(s)
to
be used.
3.2 Positioning
of
Fixings
Fixings can be broadly categorised into those which supp ort the self-
weight load of the panels and those which offer restraint. Som e
fixings may be required
to
hlfil both
of
these functions. Ideally, GR C
panels should have no more than four restraint fixings and no more
than two support fixings, as show n in Fig.
3.1.
4
NO RESTRAINT flXlNCS
-
TOP RESTRAINT flXlNGS
- SOTiOM
RESTRAINT &
lOCATlON FlXlNGS
BASE SUPPORTS -
2
NO 8ASE SUPPOR
JS
E L E V A T @N SECTION
Figure
3.1 -
Positioning
of
Fixings
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GR C panels should alway s be supported at their base to ensure that the
permanent direct stresses due to self weight are compressive. This
utilises the full strength properties of the GRC to resist transient
imposed loading. It follows that GRC panels should not be top hung
in service as this would obviously induce permanent, direct tensile
stresses into the panels Th e tensile strength of the panels should be
checked for lifting purpo ses, bearing in mind that
it
is only a tem porary
condition.
In providing support points at the base of the pane ls,
it
is good design
practice to limit the eccentricity (e)
of
the self weight
(W)
from the
support point
(Fig. 3.2
a).
Th is will, in turn, limit the permanent
reactions
in
the top and bottom restraint fixings and hence the ben ding
and shear stresses induced into the panels. Ideally, the eccentricity (e)
should be ze ro, but this
is
rarely achievable. In vertical panels, the
permanent stresses resulting from this eccentricity are usually small.
However, w hen the panel leans at some angle to the vertical, as
illustrated in
Fig.
3.2
b,
the eccentricity (e) increases
and
the induced
stresses may become significant.
H
e (eccentr ic i ty )
W
H
(eccentr ic i ty )
Figure
3.2 -
Eccentricity of Self-Weight
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3.3
Allowing for
Movements
Shrinkage, moisture and thermal m ovemen ts of GRC cladding panels
are time dep endent and su bject to wide v ariations due to the
complexity of the variables inv olved.
In
order to avoid distress and
possible damage to the GR C, fixing systems must allow these
movements to take place unhindered. Additional tolerances may also
be required in the fixings to allow for anticipated movements o f the
supporting structure.
3.3.1
Principles
of
Fixing
Fig 3.3 illustrates a recomm ended fixing sy stem for GRC cladding
panels showing the necessary freedo ms of movement
to
avoid restraint
to the GR C.
VERTICAL & HORIZONTAL
MOVEMENTS
TOP flXING
RESTRAINTS
HORIZONTAL
BOTTOM FIXING
ESTRAINT
LOCATION FIXING:
CAN BE FIXED
OR
ALLOW
HORIZONIAL MOVEMENTS
S SHOW
Figure 3.3
-
Degrees
of
Freedom
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Th e main features of the system are:
a.
b.
Panels on ly have four fixings providing lateral restraint
Vertical support is provided at two points at the base of each
panel
Both the top restraint fixings allow vertical and horizontal
movements
One bottom restraint fixing allows horizontal move me nts whilst
the other ca n be fixed
or
identical to the other bottom fixing
e.
All fixings offer so me degree of rotational freedom.
Sections 4 and 5 illustrate the types of fixings which can be used
to
provide various degrees of freedom to satisfy the requ irements of this
fixing system .
In addition to providing allowances for move ment at the fixing
positions, the detailing
of
building areas around the GRC pa nels should
ensu re that mov em ent of the GRC is not restrained (Fig
3.4).
c .
d.
GR C t D O lN G
fRff 10 MOM
\
Figure
3.4 -
Avoidance of Restraint to
G R C
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3.3.2
Shrin kage and M oisture Movements
of
GRC
As
GR C is wetted and dried it undergoes dimensional changes that are
attributable to shrinkage and.moisture movements. These changes are
more pron ounced than tho se occuring in comparable precast concrete
products. After the GR C panels have been manufactured and cured,
they are allowed to dry ou t and undergo an initial drying shrinkage.
Any subsequent w etting and drying causes reversible m oisture
movements
to
occur.
The se moisture movements are less than the
initial drying shrinkage an d so the GR C suffers an irreversible
shrinka ge during the initial drying process as illustrated in Fig 3.5.
1
EXPANSION
IN WATER
A T E R
S T O R A G E
........ .
....
1
_
~
.
IRREVERSIBLE
...
... ......
I
MOISTURE
MOVEMENT
.
I .. .
D R Y D R Y D R Y
i
i
Figure 3.5 - Shrinkage and
Moisture Movements
of GRC
As a general guide, the irreversible shrinkage amounts to one quarter
to one third of the ultimate drying shrinkage and is largely dependent
on the w aterlcement ratio.
Moisture movements tend to decrease with
age and are mainly governed by the cemen t content. The typical
variation
of
ultimate drying shrinkage
(%)
with the sa d c e m e n t ratio is
indicated in Fig 3.6.
- =
3
W
W
m
cI_
z
Ln
z
w
r
n
c
z
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0.3
0. 2
0.1
0.0
S,AXD : CERlENT R A T I O
Figure 3.6 - Variation
of
Drying Shrinkage with Sand/Cem ent Ratio
Current practice is to use sandjcement ratios of between 0.5
:
1
and
1 : 1.
The se result in a fiee shrinkage or moisture move ment in
the region of
0.15% or 1.5
mm/metre length.
3.3.3
Thermal
Movements
of GRC
The magnitude
of
thermal movements in GR C can be of
a
similar order
to shrinkage and moisture movem ents.
If
these move ments are
restrained, sign ifican t stresses can be induced into the GR C.
Th e coefficient
of
expansion ( )
of
G RC
is
within the ran ge
of 10
to 18
s
10d C. hermal dimensional changes in the GR C can be
calculated
fiom
the well-known formula
AL = a
A T L
where
A L =
change inlength
a = coefficient of linear expansion
L
=
length over which
AL is
being
AT
=
change in temperature
and
measured.
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Example
Assuming a rise in tem perature
(AT)
of
30
C and a value of
coefficient of linear expans ion (a)f 18 x lO /OC a 2.500 metre long
panel will expand by
( 1 8 x 1 0 - 6 x X O x 2 . 5 x 1 0 0 0 ) m m= 1 .35m m
G RC cladding panels o f single skin construction are usually stiffened
with ribs formed aroun d expanded foam. Sandwich panels are doub le
skin construction with a core of expanded foam. In both cases, the
GR C on opposite sid es of the core material
is
likely to exp erience
different condition s
of
temperature, hum idity and moisture content.
These differing conditions have a tendency to produce bowing o f the
panels. This bow ing only occurs to a limited extent in ribbed G RC but
can be very pronou nced in sandw ich construction. Clearly, som e
account o f this bow ing m ust be mad e if it is likely to affect the
performance of the fixings. Care must be taken to place fixings in
positions w hich do no t restrict this bowing, otherwise significant
seconda ry stresses ca n be induced into the GRC panels.
3.3.4 Move me nts
of
Supporting Structure
The movem ents that are com mon to both concrete and steel structures
are:
i
a.
elastic deformation under load
b.
sway of the building under load
C. thermal movem ents
d.
e.
deflections of beam s under load
possible differential settlements of the foundations.
In addition, concrete structures are subject to shrinkage/m oisture
mov emen ts and cree p of the concrete under sustained loading.
Panels of single
skin
constrriction are now
generally used in
preference to sandwich
panels because the
latter are prone to
bowing and
concentrations of
dvferential
temperature
/
siirittkage stresses.
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It
is generally very d ifficult to quantify these movem ents with any
degree
of
accuracy
so
a
conservative approach should alw ays be used.
Constructions which alleviate the effects of ariy of these movements
should be used whene ver possible. One method of overcom ing
problems associated w ith the deflections of the main beams and floor
slabs of the building is to provide a se parate, adjustable steel
framew ork, wholly sup ported at ground level, for supp orting the GRC
cladding as shown in Fig 3.7 a. This construction allo ws the main
beam s to d eflect indepen dently whilst still giving lateral restraint to the
secondary support steelwork which is supporting the GR C cladding.
Th e construction shown in Fig 3.7 b must not be used as the tops and
bottoms of the
GRC
panels are fixed to different lengths of steelwork
which can m ove relative to one another.
Secoridary steelwork
srrpport system s f o r
GRC cladding patiels
should be adjiistable
in both horizontal
directions to offset
possible out-of-
tolernme(s) of the
main steelwork.
PCE PACXINC
AS REQEED\
m aAoO0pH
HaES I R I
NMI
rO1EfiA CE
Pl ff PACKING
UAN BEAU
-i"
C E U C
LML
mc WMti
EBINC
LEML
Figure 3.7
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3.4 Stud
Frame Construction
A GR C stud frame cladding panel consists of a single skin of
GRC
attached to a prefabricated fram e, usually metal, by m eans of L-shaped
flexible anchors (termed flex anch ors) and support anchors
known
s
gravity anchors) as indicated in Fig
3.8.
Regu lar spacing of the flex anchors ensures that the effects of wind
loading are even ly distributed over large areas of the panels. Th e
spacing of the flex an chors is governed by the strength of the G RC but
is usually no m ore than 600 mm n each direction. These anch ors offer
lateral support
to
the G RC facing whilst allowing some degree of
rotation and shrinkage/mo isture movem ent of the
GRC.
Th e gravity
anc hors are positioned along the bottom of the panel and support the
self-weight of the GR C.
I t
is important
to
understand certain basic
principles when detailing this form
of
construction. These principles
are illustrated below in Figs
3.9,3.10
and 3.1
1
for easy reference.
See
also GRCA
Pu blicatiori
'GRCit i Use -
Strid Frame
Cladding
POINRNG IOWAROS
ENRf OF
PANEL
ELEVATION ON
BACK
OF PANEL
G C PANE1
\
CRC GONCING
PAD
ROLLfO
lN fO
BAUINC CRC
SECTION 1 -
Figure
3.8
- G R C Stud Frame Cladding Panel
1 2
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INSUFFICIENT MICKNESS
O
ANCHOR
PAD AR XIND
TACK flLOIkG
G
FLEX ANCHOR
IS GENfRALLY
UNRELIABLE AND
SUBJECT TO
F A l l C u E
FAliORE
INCORRECT7
I
7 I N C :
flp v
PAD
TO
BE MAINTAINED
AROUND FLEX ANCHOR
VERTICAL
SECTION
S N D FRAME
ANCHOR
W l l l
IMPEDE
FREE MOVEMENT OF
CRC SKIN
OR
LOCK
NUT CAN
BE USED
Figure
3.9
- Do s an d
Dont s with Flex Anchors
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i
INSUfFlCJENT THICKNESS
OF
I h
BONDING
PAD AROUND
G R A V ~ T Y
\
(
ONDING
PAD .
\
/
\
GRC PANEL
FULL STRENGTH M L D
-NO T TACK WELDING
I I: :I
PLASTIC TUBE CAN BE
USED TO DE-BONO
GRAVlTY ANCHORS
BONDING PAD SHOULD
NOT EXTEND PAST BEND
IN GRAVTY ANCHOR
GRAWTY ANCHORS POINT r O W A R D s
CENTRE
O
PANEL
SO
A S NOT TO INHIBIT
SHRINKAGE AND MOISTURE MOMMENT
LAN
Figure
3.10 - Do s
and
Dont s with
Gravity A nchors
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FULL STRENGTH WELD
-NOT TACK WELDING
\
STUD FRAME
(SECURED
TO
MAIN BUILDING)
GRC PANEL
VERTICAL SECTION
\
\
SUFFlClENT CLEARANCES
TO ALLOW SHRINKAGE,
MOISllJRE AND THERMAL
MOVEMENTS
OF
PANELS
PLASTIC SLEEVES CAN "F/
USED TO DE-BOND
GRAVlTY ANCHORS
FRAME
Figure
3.11
-- Alternative, T-B ar G ravity Anchor
Figure
3.1
1 illustrates an alternative T-bar type of gravity anchor which
is sometimes used. Th e recommended details shown in Figs 3.5 to 3. 1
inclusive are intended to give the GRC panels freedom
of
movement.
adequate lateral support and vertical suppo rt at their base.
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4.
Types of Fixings
4.1 Fixings into GRC
Ideally, sockets cast into the GR C should be used as a means
of
securing the GR C panels to the building. How ever, it
is
not always
possible to adopt this method and face fixing of the panels an d o r use
of
dowels are the only alternatives. In all cases, the loads in the fixings
should be spread over as large an area of GR C as possible. Many of
the standard fixings in comm on use for other materials can be used
or
readily adapted for use with G RC . Th e three main types of cast-in
sockets are illustrated in F ig
4.1.
,
4
CONE TYPE
CROSS PIN ANCHOR TYPE
. , ..
/
Figure 4.1 - Cast-In Sock ets
Figure
4.2
-
Encapsulation of
Cast-In Soc ket
I t
is very impo rtant that cast-in soc kets are encapsulated
in
an adequate
volume of G R C with good fibre distribution around them. The ends of
these sockets should be left slightly proud of the GRC as shown in Fig
4.2. This avoid s the possible adv erse effects of overtightening against
the face
of
the GR C during fixing.
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The actual performance and minimum edge distance of cast-in so ckets
will be specified by the manufacturer. How ever, as a general rule, the
socket should not
be
placed any nearer to the edge of the
GRC
than the
e.
O/A LENGTH OF
CAST IN SOCKET
=
1
T
3
1.71L
O/A LENGTH OF
CAST IN SOCKET
=
L
,L
T
1.71L
C 2
1.70L
c
T
O/A
LENGTH OF
CAST IN SOCKET
=
L
11
O/A
LENGTH OF
CAST IN SOCKET = L
T
2 1.71L
C
2
1.701
- T
Figure
4.3
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Face fixing
of
the panels is sometimes used, particularly when acc ess
for fixing the panels is restricted
andor
when the panels are very sma ll
(Fig
4.4).
r
MAIN STRUCTURE
OVERSIZED POCKET
WlTH TAPERS
TO ASSIST
MANUFACTURE
AND ERECTION
U-SHAPED PACKS
AS RiOUlRED
ANGLE SUPPORT
DOWEL WELDED TO
SUPPORT ANGLE
CAST-IN WASHER
MAIN
BUILDING
GRC PANEL
/
I I
Figure 4.4
Figure 4.5
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4.2
Fixings
to Supporting Structure
4.2.1
Concrete Structures
Fixing into concrete
is
usually
by
expansion fixings, resin fising s or
cast-in fixings.
a .
Expan sion Fixings
(
Fig 4.6)
When these are tightened, a sleeve is forced along a cone
or
a pair of
cones into the surrounding concrete. The fixing holds
by
a combination
of keying and friction.
I -
-
Figure 4.6
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b.
Resin Fixing s
(Fig
4.7)
Resin fixings rely on the ability of the resin to transmit the force in the
steel rod
by
bond into the surrounding concrete. These fixings can be
used closer together and at closer edge d istances than expansion bolts.
Th e time taken for the resin to set and the fixing to achieve its work ing
strength will vary according to the ambien t temperature.
Figure
4.8
c. Cast-in Fixings (Fig 4.8
These are generally cha nnels with ancIlorsfixed to the back and are
cast into the conc rete. In conjunction with 'T' head bolts, these fixings
allow the fixing position to move along the length of the channel.
Channels can be used at close centres and at closer edge distances than
other fixings.
I t is
recommended that cast-in channels are used wherever possible.
These a llow greater adjustment, can be positioned around the
reinforcement and used closer to the edge of the concrete. Cast-in
fixings are also more effective when used in the tension zone
of
reinforced conc rete beams.
4.2.2 Steelwork Structures
Fixings are usually bolted to structural steelwork, through p re-drilled
holes
or
holes drilled on site, though w elding is som etimes used
to
fasten fixing c om ponen ts to supp ort steelwork.
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5.
Tolerances
5.1
Introduction
GR C panels cannot be produced to an exact size nor can buildings be
constructed precisely to line and level. Con sequently, a degree of
tolerance sh ould be incorporated into fixing systems for cladding
panels to avoid fixing problems o n site.
I t
is also essential not
to
use
movem ent allowan ces in fixing components as tolerance. When the
panels are finally fitted, the mov emen t allowance s are required to avoid
possible distress to the GRC panels. The designer should refer to BS
56 6:
1990
an d relate the specified tolerances
of
the support structure
to tolerances required
for
the cladding panels. Ho wever, it is not
always possible to allow
for
the combination of building movements,
panel m ovem ents and worst tolerances, as this would result in
acceptably w ide joints between the G RC panels. In such cases, an
accurate site survey w ould enable the designer to address these
problem s, mainly by customising the panels andor fixings.
Notwithstanding this, some reliance must also be placed on the skills of
the erection team to overco me toleran ce difficulties o n site.
5.2 Adjustments
Ad justm ents will be required in all three planes, the degree of
adjustmen t necessary will depend o n the type
of
structure, individual
tolerances (structures and G RC panels), site control and the overall
finished tolerances to be achieved.
5.2.1 Angle Support Brackets
Adju stments in the fixing of angle support brackets may be provided in
several ways as follows:
Figure
5.1
- Packing
Shims
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In-plan adjustment ca n cause problems o n site.
A
minimum bearing
area
of GRC
on the suppo rt must be m aintained to avoid distress to the
GRC. Packing shim s (plate or horseshoe w ashers) should gen erally be
limited to a maxim um thickness of 12
mm.
Packs should b e positioned
such that their lower ed ge is at or below the start of the bend in the
angle as indicated (Fig 5.1).
/
Figure
5.2
Oversize holes in co njunction with serrated washers provide multi-
directional adjustm ent with a positive
lock.
Packing shims are used to
provide in-plane adjustment as shown in Fig 5.2.
Horizontal slotted holes facilitate lateral adjustment. Vertical
adjustment can be provided by fixing the angle slightly low and seating
the cladding on tw o
or
more PTFE packs as indicated (Fig
5.3).
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Figure
5.3
Figure 5.4
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Channel fixings anchored to the backing support can provide considerable
fixing adjustm ent in one direction only (vertical or horizontal).
A
toothed
channel should be used to provide vertical adjustment and a positive lock.
In this case, horizontal slotted holes in the angle provide the necessary
adjustment as show n
in
Fig 5.4.
1
horizontal adjustment. Packing shi ms are used to provide in-plan
. .
I.
AA
C CLADOING
PANEL
CRC CLADDING
8 - J
PANEL
S
APPROMD
RE9LlEN1
FILLER
~~~
Figure 5.5
2 4
..
t
~
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Angle support brackets may incorporate dowels or welded flats to
provide horizontal fixture for the GRC panel
as
indicated in Fig 5.5 a,
b
and c.
Incorrect fixing
of
angle supports, as shown in Fig
5.6,
can result in
bearing problems. Angle
supports
with only o ne fixing bolt are to be
preferred as they take le ss time to fix and have the capacity to rotate
and provide the intended bearing area.
P o s s t e L E DISTRESS
TO GRC IN BEARING
SECTION
AND /
OR
GRC CLADDING
PANEL
POSSIBLE
DISTRESS
/TO GRC IN 8EARINC
/
IXING BOLTS
.
ANGLE
SUPPORT
FRONT VIEW
Figure
5.6 -
Incorrect Fixing
of
Seating
Cleats
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P o s s i e i E
DISTRESS TO
DUE TO HIGH BEARING
PRESSURES.
EOUCEO BEARING
AREA
SECTION .
AND
1 OR
GRC
I
REOUCEO BEARING
AREA
FRONT V l EW
PossieiE
OISTRESS
TO GRC
DUE TO
HIGH
BEARING
/
R E s w x S
Figure
5.7 -
Problems
with
Undersized Packs
Reductions in bearing from using undersize packings can result
in
excessive bearing pressures and possible distress to the
GRC
(Fig
5.7).
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\
\
F
Figure 5.8
PACKINGS AS
\
TAINLESS STEEl
ANGLE SUPPORT
\
RESILIENT
FILLER
P o n e l s d o n o t hove i n d e p e n d e n t
h o r i zo n t a l adjJstrnent
8 o d p o ck i n g co n re su l t
in
r o t o t i n g s/s onqle s u p p o r t a n d
d i s t r e s s
to
GRC
\
STAINLESS STEEL
DOWEL
IN
HOLE
THROUGH ANGLE
SUPPORT
COMBINED
FIXING
FOR ADJACENT PANELS
The com bined fixing shown in
Fig
5.8
is
some times used
for
lighter
GRC
panels. it does
not,
however,
allow
independent horizontal and
in-plane adjustme nts
of
the upper and lower panels.
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i
f
- Allows independeni hor iz sntd
SLOTTED HOLE IN
STAINLESS STEEL pone15
FLAT FOR VERTICAL
adjus tment c f upper ond lower
/
DJUSTMENT
@cd
packinq
con
result
in
rolation
of
s/s anyle support
STAINLESS STEEL FLAT
WlTH
PACKINGS AS
REQUIRED
STAINLESS STEEL
FIXING SOCKET
Figure
5.9
An alternative, preferred detail which do es allow separate adjustment
of
the upper and lower panels
is
illustrated in
Fig 5.9.
4
A L T E R N A T I V E
FIXING
D E T A I L
SiAlNLESS STEEL
FLA
1
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5.2.2 Restraint Fixings
Details of typical restraint f ix in g are s h o w in Fig 5 10 (at the top of
the GRC panel) and
Fig
5.1 1 (at the bottom of the
GRC
panel).
GR
PANEL
PACKING
STAINLESS STEEL
FIXING
SOCKET
CLEARANCE
-
METAL TUBE AND PLASZC
SEPARA TlNC SL EE K
PTFE WASHERS
TYPICAL FIXING DE
TAIL
r
rop
OF
GRC
PANG
Fixinq socket sliqh ly proud of
sur face
10
ensure that
forcei
applied during
liqhteninq cannot pcll aut fixinq.
solation
o f mild
sk l and stcinless steel
ensued b y plaslic i c b c and PTFE washers.
Figure 5.10
-
Restraint Fixing at Top
In the top fixing (Fig
5
IO), the cast-in s ocket should be slightly proud
of the GRC surface
to
ensu re that forces applied durin g tightening
cannot pull
i t
out. Tolerances can be provided by the use of packs and
oversize holes. Isolation of the m ild steel and stainless steel
components, to prevent an y galvanic corrosion, is ensured by the use
of PVC tubes and
PTFE
washers.
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T Y P I C A L SUPPORT D E T A I L
A T BOTTOM C O R N E R
.
Fixings give a measure
of
hor izonld
ond ro la l ional movemenl by
use of
PTFf
washers.
SPANNING HORIzONlALLY)
Toleronces calered
for
by use of
pocks
ond oversize
holes
m
ploles which ore
welded
to
hor izonla l ly spanning sup por l
onqle.
lsololion of
mi ld sleel ond sloinless
sleel ensured by PVC lube ond
PTFf
washers.
SIMILAR
TO
ABOM
Figure
5.1
1
-
Restraint F ixing at Bottom
Th e bottom fixing (Figure 5.1 1 ) provides lateral restraint and supports
the weight
of
the panels. Tolerances are again provided by the use of
packs and oversize holes. Isolating tubes and washers are required to
prevent the possibility
of
galvanic corrosion.
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4
SOUARE STAINLESS
Preferred detail because
of qoad tderances and
freedom o f
movement
to
1
T
RC CLADDING I
lsdatirm
01
mad steel
and
stainless
sleel
ensured b y PV tube and
P lFE washers
I
I
VIEW
A
Figure 5.12
A combined fixing which provides se at in g, lateral restraint,
good
tolerances and freedom of movement for the
GRC
panels is illustrated
in Fig
5.12.
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P R O B L E M A R E A S
-
T O L E R A N C E S
OR
PROBLEM EVEN MORE LIKELY
IF
THIS DISTANCE
IS RELATIVELY LARGE
Figure 5.13 - Problems with Cast-In Sockets
Cast-in sock ets being way out
of
tolerance are commo n (Fig
5.13).
Care shou ld be taken during manu facture to ensure that the positioning
and alignment of cast-in sockets is as accurate as possible. In addition,
outsized holes an d/or other adjustments should be provided in the
support comp onents to avoid this becoming a problem on site.
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5.2.3
GRC Stud
Frame
Cladding
When the stud frame
is
suspended ov er the freshly sprayed
GRC
facing, to facilitate bonding o f the flex and gravity anchors onto the
facing, the frame mu st be placed within tight tolerances to avoid
problems with erection
and
jointing of the panels o n site.
Figure
5.14
highlights the critical dimensions
of
the stud frame panel
with typical tolerances for m anufacture of panels
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i
6.
Fixings
for
Liftingmandling
Separate fixings should be provided
for
lifting purposes to avoid possible
damage to the permanent fixings. Lifting points should be placed a s close
to the centre
of
gravity of the panel to ensure that
it
hangs as near vertical
as possible when being lifted/handled (Fig 6.1).
Recommended