Pfs Unit 5 16marks_NoRestriction

8/10/2019 Pfs Unit 5 16marks_NoRestriction

1/21

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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2/21

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.


3/21

b)

By

welding:

,Oo

x

tooxlo

t6

to

xrortomr',

Pl


4/21


5/21

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.


6/21

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:


7/21

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 ,


8/21

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


9/21

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


10/21

.

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


11/21

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


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


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


14/21

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


15/21

.

'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/


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


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.


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'{


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


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


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

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