Pfs Unit 5 16marks_NoRestriction
Transcript of Pfs Unit 5 16marks_NoRestriction
-
8/10/2019 Pfs Unit 5 16marks_NoRestriction
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PART
.
B
1)
Explain the
differenr
rypes
ofioints
(APR/MAY 2003)
i) Rigid
Joints:
.
Can
take
tensile, compressive, shear
and
bending
moments too.
.
Relative
rotation
and
relative
displacement
are
impossible.
.
Generally
used
for
the
iunction
ofcolumns
to footings.
.
Used forjoining ofindividual
members to
each
other.
Limitationsi
.
Requires
considerable man
power
and
hence minirium
applications.
ii)
Hinge
like
Ioints:
.
Can transmit forces
passing
through
hinges
itself, and also allow
certain
motion
and
rolalions.
.
,oints
osed
in
precast
members
are
usually
hinge
like.
.
Requires
less working time
than
that ofthe
rigid
joints.
.
Execution is
simpler.
iii)
Shod Joints:
.
Used
in industrial construction
and used
for
longspan
only.
.
Chiefly used
in bridge
construction
for long
span
bridges.
iv)Dry
Joints:
.
A
joint
accomplished by
simple
placing
oftwo
members on
each
other and
then
fastening
them
is
called
dry
joint.
.
The
structure becomes
immediately loose
bea ng-
v)
Wetloints:
.
The
joint
rcquiring
not
only
a casting
cement
morlar, but
also
a
subscquent
concreting
is
called
wet
joint.
Eg:
when a
rigid
jointis
formed,
generallythe
Iengthening
ofsteel
bars is byjoining
the
members
by overlapping
[or)
welding
them
wh
jle
the
discontinuity
is avoided
by
a
skilful subsequent
concreting is called wet
joint.
.
Adcqualc
for
the bcaring
ofgreater force.
.
Struchrrc
assembled
used
a
wer
ioint
have a
monolithic
character.
.
Wct
ioints
conlply
with
cha
racl
eI
o
f
material
ofstruchrrelobejoined.
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2)
Explain
in
detait
rhe
different strBctriiat
ionneciiqn;i;p;;;ii
a;ii,ti"E
.;
Junction
typcs/groups
of
Joints
(April/
May
ZO17)
(May
/runc
ZO13J
i.
Ioining
ofcolumn
to footing.
ii.
loining
ofbeam
to top
ofcolumn.
iii.
Joining
ofbeam
at an
tntermediate
ioint.
iy.
Lengthelingofcolumn.
v.
Joining
of beams.
'
vi.
Formirtg
ofjoints
forarcherl
slructrrrr:s.
'
vii.
Joiningofjointsofposttensionstructures.
viii.
loining
ofprecast
to monolithic
RC structures.
iJ
|oining
ofcolumn
to
footing:
.
Usually
rigid.
.
It
may
also
be
hinge-like.
Methods:
A rigid
ioint
can
be
made by
placing
the
column
into calyx
at the
footing
or
by using
welded
joinL
;r)
Culufirn
plared
irlto
a calyx:
COL(JH
-
loc.o
aErNrlB
'
co^r"PETE
F|LL
ATEEL
RATE
.TO
EN&EE
@FT
fos'flIa
aF
cal-t)rlN
Advantages:
.
lt
is
simplcr requires
less
timc
suitablc
for small
column_
(i-cl placing,
pumping,
fixing
of
fhc colurnn and
filling
calyx
with
concrete
is
easier.
.
lhis mcthod is leasl resistivc
to
inaccurrcicsararsingdue
toconstruction.
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b)
By
welding:
,Oo
x
tooxlo
t6
to
xrortomr',
Pl
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c) By welded
ioint:
welding of column
to
foo
b)
Bv
s6.,t Pl"f,.
dvantages:
.
It
is effective
and
wide
spread method.
.
lt is
easily accessible.
.
lt
ensures
the well
executed
work and aiiequate control
.
It is
more
economical
for
larger member
thrn
the
calyx method.
iii)
loining
of
beam
to
column on
top ofcolumn:
a) By overlapping
steel bars:
tsi
>tA
A
l-
Wor^
Co[rfl",
weldingr
Tr,rifr
cortreV
1-
hoh"/;'4
f.""
ffi
7,6r'
lYorie^
'
@Y*Job
Simple
method lor
riSid
iunction
fitting
column wilh
beam
at
gi.der.
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b)
.
At the
top
ofthe
column
the
use ofovertapping
steel
with beam
and
subsequating
concrete
is
alone.
Li0litations
.
Demands
more
carc and
skill.
.
Increased
use ofsteel.
.
Execution
of
work is complicated
becauie
the
work
must
bc
performed
at
a
greatest
on a light
scaffold
suspendd
on
the beam
itselt'
CoLr*,'
c)
I
d)
lntcn
cdiatc
lrcam-column
ioints:
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It
is
the
easiest method
[i.e)
placjng
a
beam
on the
top ofthe
column.
At
the resting place,
both the
top ofthe
column and the
underside
ofthe
beam
must
be furnished
with
a
steel
plates
anchored
into
the concrete,
so that
the two
steel
plates
rest
on each
other.
v)
loining
of truss
to
a
column:
--\
,r^t
\Z
err{orcol"-cnt
.d
o"or"[.y
.
'l'he
truss
rests o[
the column
by
its cantiiever]ike
lengthened
upper
chord
while
the
lowel chord
has subsequently
be lengthened
and
joined
to
a coiumn.
For
ve.tical
loads
) The
joint
should
be Hinge-like.
For
horizontal
loads
)
The
joinl
should
be
Rigid.
vi)
foininA
of
column to a beam
at an
interrnediate
level:
cardMrl
f?h'4l
Nq
It
is
appliclblc lor
multi
storeycd
huildings.'l'hclc
are two
mJthojs.
THBDoql|
sevEehL
FttfPd ,
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Mct}lod I:
The
beams
rest
on
cantilever
of
the
column
and
their
top bars
are
welded
to
dowels
protruding from
it.
Method
II:
A beam
shaped
Iike an inverted
'U'
rests
on
cantiiever
protruding Iaterally
from
the column'
The advantage
is
that the
concentric
loading
can also be accomplished
for the outermost
columns
which
is impossible
when
using method
NOTE:
Ifan
additional
reinforcement
is
applied,
the
beam
can
also
be
transformed
to
a
continuous
beam.
vii)
Lengthening
of columns:
.
Columns
are usua)ly
Iengthened
at floor
levels.
.
Intermediate
lengthening should
be
avoided ifpossible.
B@N't'
W2r^
Z
'lu1.,,,[
1cru.-'
)q"d
&*^x11^
.
The upper
columns
rest on
the lower ones
by
a
tongue
Iike extensions.
.
The
steel bars
of the
main reinforcements
are
loined
by overlapping
are looped steel
hars are
welding.
.
'fhen
the
stirrups arc
to
be
placed
.lnd
finally,
the
iolnls must
be
concreted
viii)
loining
ofbeamsl
a)
o'P,Uf
'l'lre
iu
n.rion
oi the beam
is donc
by ovcrlapping
lhc
protruding
skrcl
bars or hy
wclding
th
cnl
logethcr.
10
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The
ioint
is
constructed
by making
the
beam
ends
cantireverlike
and
werding
the
steer
bars
together.
NOTE:
The
verticaljoints
are
better
than
inclined
ioints.
ix)
Forming
otiunction
for
arched
structures:
SrS,""1#
C-'"ol'Y
.
Prccastarches
are
usually produccd
and
assembled
in
the
form
ofthree
hinged
structure,
.'l'he
elimination
of
centreioint
increases
the
rigidityof
the
structure.
.llingeofarchedstructurescanbemadebyusingeithersteel
bars
shoes
or
hjnges
forrned
ofconcreto
.
Stecl
bars
are
expensive.
x)
Joint
for post
tensioned
structures:
11
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.
By
post
tensionin&
it
is ensured
that the
entire
shucture
including
the
joint
only
compressive
can
developed.
.
The
ioints
are
made
by
placing
plane
surfaces side by
side and
then filiing to
gaps
with
cement
mortar. By doing
so,
longer beams
cari also be
produced
from shorter
pre-cast
members-
.
No
drffrculties in making
joints.
.
After casting
of
the
gaps
and
hardening
ofmortar,
the
short
inserted
cables
are
stressed
and
so
rigid
ioints
are established.
xi)
Joining
ofprecast
to
monolithic
RC structures:
.
Achieved
by
placing,
end
ofthe
beam either or tvvo
cantilever
protruding
from
the
colu
mn
or
an
opening
from
in
lhe
shaft
of
thi: column.
Poe"":t
S>
orrtzQ
baxz
.
dot,.Y''
When making
joints
first
of
ali,
a 2.5cm
deep
cavity
is chiselled
out at
the
side
of
the
precast
column.
The
bottom
of
this cavity should
be
roughened
so
as to attain
a
better
bond
b/w the
concrcie
ofthe
mon(rithic
bcam
and
prccast
column.
3
)
Explain
about suspension
of
mcmbcrs:
(APR/MAy
2003)
i)
Suspension
oI nrernbers
by slopinS
cahlc
I
g''&
t2
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jiJ
Suspension
of
members
by using
a
stock.
iii]
Suspension
by
a
triangular
cable
rocks.
i)
Suspension
ofmembers
t
y
sloping
cables:
r
'fhe
menrbers
have
to
be
transporred
Frotn
the
manutacturing location
to the
storing
.
Sometimes
frames
(bridge
crane,
tower
crane,
gantry
crane
etc)
are
usually
used
for
transportation.
o
The
members
are
hanging
from
tle
hook
ofthe
crane.
Method
ofsuspenslon
depends
on
form
and dimension
ofmpmbers.
.
The
suspension
must
be situated
above
the
beam
or
else
the
beam
become
unstable.
ii)
Srlspension
ofmembers
using
a
stock:
sl""f./-giJ
4..^a
.
Stabiliry
ofthe
beam may
be
by enclosing
beam
by
a
stock
(i.e)
by placing
the
girder
into
a
rigid planc.
By
dqing
so, the
suspension
itselfis
transferred
to
a
pointoutside
th(.b.rm.
iii)
Suspension
by
a
triangular
cable
rocl(s:
13
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8/10/2019 Pfs Unit 5 16marks_NoRestriction
12/21
.
Incrcasc
in
the statlility
can be
achieved.
.
Thebranches
ofthe
triangular
cable
rockers
are
ofequal
length
andjoin
at
the
suspension
ioint.
NOTE:
When
the members
are
suspended
at
any
points
a lifi
ing
should
begin
simultaneously.
Jo
sl.Itq
inlo
a
Adok
LIFTING
LIIGS:
kt+y
X,4^
4)
Largc
concrctc roofing
mcmbers:
.
It rests
dircctly
on
the main
girdcrs ofthe hall
struclurcs.
l4
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8/10/2019 Pfs Unit 5 16marks_NoRestriction
13/21
'
Ij;;ttt'."t''
length
corresponding
ro
rhe
frames
[6
ro
10m]
width
is
[1.3
to
.
They
are
direclly
supported
by
the-maln
girders
so
that
purlins
arc
hot
requit.ed.
A large
roofing
member
con
having
a
thick.ess
o,r.r,;'jfi:lT::j:Tli:Tl.".i*""#::.."'s
ribs
aDd
a
srab
.
'l'hese
members
connected
t
unirormcd
continuou,
_-,,u.,orflfn
utnu.
aDd
Lo
the
f'a
me
girdcrs
from
by
5)
Kinds
ofmembers:
i.
Normal
members
for
intermediate
placing.
ii.
Mem h|rs
with
r
cornicu.
iii.
Members
havjng
edves
gufl
er.
iv.loining
members
.
The
members
can
be
solely
from
RC
or
combined
with
porous
hollow
tiles.
.
The
heat
insulation
oFthe
roo
t,es
or some
other
s,n,r"
;lil,'ffi
jjil""T:,l,o:ffiT:;:Xr1rffH."T-
'
[:"ii[::"'*'
amountins
to about
1
to
2cm
rrequentrvo."i"
ilu
,o
,nr..u.r",
or
.
These
must
be
equalised
bya
subsequently
mortar
Iayer
and
the
heat
insulating
items
have
to
be
embedded
into
this
mortar
tEdge
rib
Dimensions
are:
.
For
spans
of
6,
9
and
12m,
the
widrh
is
usually
4,
S and
6m.
The
depth
varying
from
25
to
50cm.
These
widths
are
r
around
rhe
bottom
b*.
,t*"
[ff;i;",;:r
encasing
the
adequate
cover
of
concrete
6)
Rocl(ers
used
for plane
members:
.
Ifthe
member
is
[o
be
lifted
at
more
than
B
points.
.
Distortion
in
thc
member
takes
place.
15
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4)
How
stresses can be
eliminated
during erection olprecast
elemerlts. (May/Iune
2Ot2)
Surplus
stresses are
forms when
memters are hoisted
and
placed.
These
stresses
are
called handling or erection
stresses.
.
In
good
method
ofconshuction
is
characterised
by
elimination
ofthose stresses.
.
It
should
be
eliminated
iD
such
a
way
that
no
additional reft
is required.
.
The
stresses due to wind
or other
external
forces
are
avoided
by a temporary
racing
ofthe
placed
members
facening.
lfI"q
ilJ
H*^J
A-
{
(D.L
t
1**-l
d.,
L
.'lhc
hoistingof
a
straight
beam is
accomplishcd
by
liiting it
at
2pts.'
16
eusl
/o,,v";y
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8/10/2019 Pfs Unit 5 16marks_NoRestriction
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.
'I'he
location
ofthesc
2pts
depends
on
tlre reft
ifthe
bcam
is the
s.s
one,
the
lifting pt
should
be at the
ends
or
in
such
a manner
that
tlre aralsing
moment
should
be
equalised.
.
When hoisting
a continuous
beam,
post
tcnsioning
is
necessary.
B)
Girrlers:
position.
COLUMNS:
A
girder
having
a length
of 25cm
is
clutched
at
Zpts
when
ir
is
hoist
but
the
tilting
of
same
girder
requires
atleast
4
Iittlng
pts.
'l'hese
pts
should
be
determined
based
on equal
moments
simultaneously
taking
iflto
consideration.
'l'he
reft
design
[o
resist
force affecting
the beam,
in
its
final
The
mostadvantage
pt
for
lifting
should be
first
determined.
The
column
dividing hoisting
acts
like a
s.s
beam
with
the
cantilever
at
the
end,
loaded bythe
dead weigh
temporary post
tensiooing
must
be worked
out,
so that
additional
reft
is
not required.
l-,f,J."q
p.iJl
ELI
MINATION
METHODS:
'llhe
stresses
developing
in membcrs
in
lhe finalposition.
An
additional
reft
may
bc
sometimcs
is finished-
during
hoisting
and
placing
differs
these araise
require
but
Becomes
unnecessary
after
placing
1/
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8/10/2019 Pfs Unit 5 16marks_NoRestriction
16/21
.
Hence
the
additional
stresses
as
well
as
reft
required
to
resist
them
should
be
eliminated.
5) What
are
thc
methods
used
in stress
elimination
in
precast members:
(
i)
a. By
an
l-profile
steel
beam
to the
girder'
b.
Using
Post
tensioning.
ii)
Bracing
of
two stancilions'
iii)
Temporary
Post
tensioning'
iv) MultiPoint
PickuP..
i)
By
an
l-profile
steel
beam
to
the
girder:
.
This
is
most
simple.
.
The
ends ofsteelbeam
are
merged
to stanchion
while its
middle
is stresses
to the
stanchion
by the
bolts
of
an inserted
stirrup
which
Frcsses
it down'
.
Hence
the
developing
bending
moment
due
to
the dead
load
is bound
by
the steel
beam
and
the
remaining
by the
stanchion,
without
any
additional
reft'
.
After
the
beam
has
been
hoisted
by
450,
the temporary
reft steel
beam
becomes
unnecessarY
and
can
be removed
.
For large
structure,
(great length
& strong
forces]
this
method
is
unsatisfactory'
.
IJence
for
those structures
post
tensioning
can
be adopted'
3oo..r"
i
-FoP.L
beoJn
Ne5
".5*
rro*gJ
t
o'a-
bs
A
Po{lz
beat.
'ilrL
-*J
+"
te
tor'o
61
n^, oil,,,,-
hill
18
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8/10/2019 Pfs Unit 5 16marks_NoRestriction
17/21
. 'l'he
tenslonlng
force
rs
controlled
bymeasuring
thc.reaction
force
developing
abovc
thc
lifting pin
using
a nlat.r{rrtletcr.
.
When
the
column
has
been
hoisted,
the
equipment
used
for
post
tensioning
has
to
be dismantled
before placing
begins_
ARACING OF
TWO
STRUCTIIRES:
.
It is done
by
placing
two
stanchion
ofa
plane
[u IJe
transported,
so
that the
moments
arising
at
the supports
are
climinated.
.
Developments
of
negative
stresses
are
overcome
by
the
bracings
provided.
By
using
hydraulic
iack
the hoisting
is
done. After placing,
the
bracing
bar
i.
.._ouea.
-_lo"psa
hsl
@:r
,
.sh",,r;^q
&t
on
-
t-r
e
,J,r
H{&a,-t'
JocJ.L
The
elimination
ofstresses
is
achieved
by
temperory
post
tensioning
of
a
shorter
section
ofthe
column.
The required
tensioning
force
is providecl
by
a
hydraulic
jack.
The
girder
is lifted
at
two
pts,
The
sfressing
cables
are lead
in
as in
a
way
that
the
moment
developing
from
post
tensionin&
djminishes
to the
necessary
degree,
the
moment
arising
due to dead
load.
Multipoint
Pickup:
.
It is
one ol thebestsolulion\firrtheeliminationoferectionstressesforeg:hoisting
of
a
truncatcd
cone
like
rool over
a
ce,nent
silo.
.
Ihc
roofwas
liJrcd
at dual pts
,n a statically
determined
manner
using a
three pt
suspension.
-
8/10/2019 Pfs Unit 5 16marks_NoRestriction
18/21
This resulted iD
truncated cone
the elimination oferection
stresses
in the Iower edge
ring
and
shaped
roof:
(
'Tin'oeo*l
-cor\'o-
sl,rfp.A
rr'{
-
8/10/2019 Pfs Unit 5 16marks_NoRestriction
19/21
)By
Overlapping
hooked
Stcct
bars.
'
The
len8thening
of
steel
bars
by
over,e.hihd i.
-^l
-
^_-
.-- .
.
subiccred
to
rension
*"o*n"."
,l",iflLiliis
not
pernritted
when
the
concrcre
is
'l'he
most
suitable
welded
joint
welde
's4
s:sA-
oI
four
welds
and
two
laps.
d
leDgthening
is
in
arc
welded
ioint,
consisting
Length
ofLap
=
2*3.Sd
=
7d.
Diameter
=
O.7d
d
)Diameter
of
steel
har
lengtherled.
.
Grade
ofsteel
uscd-
.
;::ty
steet
Crades
34.218.
50,
35
Bmk
can
be
welded,
the
carbon
conrerr
is
almost
B)
According
to
cerman
Standards
(DIN
4225):
.
The
cube
strength-ofcement
m(
*."#,,:,j.[[:,j,off[T:fl1i:;,_1ff
:ilT:11,J:"r;surinsadequa,e
].:;Hi:Il""
r,rltar
its
top
must
be ar
teast
3cm,
is
compressive
force
is
to
be
Caps
between
slabs
like
beams
are
toformed
like grooves,
which
when
filled
up
ith
C.M
is
appropriate
for
the
transmission
ofshear.
'l'hc
bcst
concrctc
quality
to
be
considered
in
the
case
ofan
in-situ
concrcting.
i)
is
C 300
if
the
srnallcst
dimension
is
not
less
than
1ocm.
(
t*d
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8/10/2019 Pfs Unit 5 16marks_NoRestriction
20/21
iiJ is C225 ifthe smallest
dimension
is
3cm-
The
permissible
compressive
stres$
is
50
I(P/cm2
in thc
case ofioint
lcss than 1cm
widc.
C)
According to soviet
code:
'l'he
quality
ofconcrete
used for 0re
co[cretiilg
ofioints shall bei
Be er
by
1q than
ihat of
the
joinl
members,
provided
lhe
plan
does not comprise
any special
stipulation.
lf
the
ioints
between the
precast
members are
ofsmallsize
and non-refd,
the cross
section
ofthese
joints
cannot subiected to
either compressive
or
shear.
If the
joints
are oflarger
size and refd,
their
c/s
can be taken into account
because
widcrioints
make easier
and
better
concreting
possible.
D)
According
to Austriatr
code:
Similar
to the
Hunga
an code.
Specifies
the value
ofthe
permissible
Shear stress
is the
precast
and
the in-situ
conc rete at only hall
of lhe
value of
thc
sheJ
r
slress
can be considered.
Safety
ofjoints against
failure should not less than
3
fold.
Joining
of
prefabricates
in
shucturalwalls.
B)
Explain
the
ioint
technique and
materials used in
detail?
(Nov/Dec
2013)
Ioint
techniques
normally
employed are:
.
Welding
if
cleats or
projecting
steel
.
overlapping
reinforcemenl
loops and
linking
stcel
grouted by concrete-
.
Rcinforced
concrete ties
all round a slab
.
Pl-estressing
.
Epoxy
grouting
.
Ilolts
and nuts connection.
and
.
A combination
ofthe
above.
ll
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8/10/2019 Pfs Unit 5 16marks_NoRestriction
21/21
Materials for
concrete
ioints:
There
are numerous different materials
used
in fbrming
joints
in
concrete slabs, but the
nlost
conT
nlon are
.
Flexible board
. Dowels
.
Sealants
Flexibldboard:
.
A fibrous,
compressible, flexible board
such
as
flexcell, it
is
cheap
and
readily
available from
builder's merchants
in
pre-cut
strjps ofthe
required
depth,
especially
tor creating
expansron
lolnts.
.
It
is
typically
12mm,
20mm or 2smm thick and right thickness for the
joint
should
be chosen.
.
No
joint
should
be
wider than 30mm.
Dowels:
.
400
-
600mm lon&
Z0
32mm in
diameterand
manufactured
from
grade
250steel.
Sealants:
There are three
main types
.
Hot
poured,
usually
bitumirous
in origin. Not as widely
used
now
a days as
they
once
were.
.
Cold applied,
often
a
two
part poly
sulphide mix incorpora'ting
resins and
curing
agent.
Usually
applied via a mastic
gun
and smoothed
with a
putty
knife.
.
r
Preformed
elastomeric, expensive and need to be
squeezed
and inserted into a
scrupulously
clean and
w(ll
l0bricated
perfectly
formed
joint.
9)
Explain
the
design
ofExpansion
ioints
in
Precast Structures
(APR/MAY 2013)
(Nov,/Dec
2013)
(MaylJune
2011)
Expansion
joints
are
necessary
in
precast
structures
in
order to allow for the
expansion
and cooling
ofvarious
members due
changing
in
tcmperature.
ln precast
structures^
the shrinkage
takes
place
before the assembling ofmembers,
therefore the
spacing
oI
expansion
joints
may
bo
1.5 to 2 times
greater
than
in monolithic structures.
I-xpansion
joints
are
usually formed
at
the
joint
ofroofing members and
main
girders.
2l