REINFORCED CONCRETE

siennatearfulUrban and Civil

Nov 25, 2013 (3 years and 11 months ago)

71 views

REINFORCED CONCRETE


Reinforced

concrete

is

a

composite

material

which

utilizes

the

concrete

in

resisting

compression

forces
,

and

steel

bars

and/or

wires

to

resist

the

tension

forces
.


Concrete has great compressive strength (this is the
ability to support great loads placed directly upon it).


However it has very little strength to resist stresses or
forces that tend to bend or pull it apart.


The compressive strength of concrete is about 10
times its tensile strength.


Steel reinforcement therefore becomes necessary to
increase its tensile strength.


Concrete is cast around reinforcement steel.


As it hardens, it grips the steel to form a bond with it.


This bond becomes stronger as the concrete hardens.

TYPES OF
REINFORCEMENT


Reinforcement steel is
manufactured mainly in three
forms:




Smooth steel bars

(Düz insaat demiri)




Deformed steel bars

(Nervürlü insaat demiri)




Wine mesh steel bars

(Hasır)


Both smooth and deformed bars are
produced in standard sizes.


They are normally designated by a number
of thickness, incating their diameter in mm.


like:


8, 10, 12, 14, 16, 18, 20, 22, 24 with
a difference that deformed bars is not
produced normally in 8 mm. in diameter.


Their standart length is 12 mt.


Main difference

between smooth and
deformed bars is that the load carrying
capacity.


Deformed bar is greater than that of smooth
bars.


Wire mash is normally used to reinforce
concrete
slabs and walls
.


It comes in the form of right
-
angled steel
bars welded to one another at the
intersection points.


Wire mesh reinforcement is manufactured
in various sizes or wire diameters and in
various sizes of spacing.


The spacing and wire sizes may be equal in
both directions or they may vary in size and
spacing to form what is called one
-
way
mesh.

FORM CONSTRUCTION


Concrete and reinforced concrete structures
require forms to provide the desired shape
and surface texture.


Forms may be made of wood, steel,
fiberglass, hardboard and other materials.


The forms must be strong enough to resist
the forces developed by the plastic (liquid)
concrete.


Forms generally have five elements:

1.
Sheathing/ board


2.
Studs/joists


3.
Wales


4.
Braces or supports


5.
Ties and/or spreaders (see bottom the
figure)



Forms

are

applied

to

different

building

components

in

different

ways
.

Therefore

there

are

at

least

six

different

applications

of

concrete

form,

such

as

follows
:

1.
Footing


2.
Walls


3.
Slabs


4.
Steps


5.
Beams or columns


6.
Masonry support



Form

maintenance

is

important

because

it

reduces

the

cost

by

extending

the

life

of

a

form
.



Many

forms

are

damaged

during

stripping

(removing

them

from

cured

concrete)
.



They

should

be

inspected,

cleaned,

repaired

and

lightly

oiled

after

they

are

removed
.



A

wire

brush

may

be

used

to

raise

the

grain

and

roughen

the

surface
.



A

liberal

amounth

of

oil

should

be

applied

a

few

days

before

the

plywood

is

used
.

PLACING STEEL
REINFORCEMENT INTO FORMS


The steel bars are at first stockpiled on site,
and than shaped according to the
measurements, thicknesses and shapes
specified for each unit of reinforced
-

concrete, building component, by the
structural execution design of the building
under construction.


Giving

steel

bars

desired

shapes

can

be

carried

out

on

the

site

through

the

help

of

simple

scaffolding

and

steel

bending

and

hooking

devices

and

levers


The

location

of

the

steel

within

the

concrete

mass

may

differ

as

to

the

type

and

position

of

the

building

component
.



It

may

be

important

to

mention

here

the

theory

about

this

issue

very

briefly
.



When

a

vertical

load

is

placed

on

a

beam

or

slab

that

rests

on

upright

supports,

the

beam

or

slab

tends

to

sag

in

the

center

between

the

supports

(see

the

above

figure)
.


During

this

bending

action,

a

squeezing

force

created

on

the

top

of

the

beam
.



At

the

same

time,

a

stretching

force

is

exerted

on

the

lower

side
.



Where

the

beam

passes

over

the

supported

column

a

sheer

(cutting)

force

is

present
.



Where

the

beam

rest

on

the

column,

the

forces

are

reversed
.



Tension

force

is

on

the

top

and

compression

force

is

underneath
.



In

order

to

equalize

these

forces,

the

main

steel

bars

are

placed

in

the

beam

as

shown

in

the

below

drawing
.


Steel

reinforcement

is

mainlyplaced

wherever

the

tension

occurs
.



The

steel

bars

are

then

bent

accordingly
.

Others

are

added

to

these

bars

for

equalizing

other

pressures

that

the

building

may

be

subjected

like

eartquake

and

wind

pressure
.


The

steel

rods

are

generally

spaced

high

enough

from

the

bottom

of

the

form

to

allow

concrete

to

completely

surround

the

rod
.



Saddles

are

used

to

hold

reinforcement

bars

above

the

bottom

of

the

form
.



Reinforcement

steel

must

be

placed

and

secured

before

any

concrete

is

poured
.



This

is

important

because

flowing

concrete

will

cause

unsecured,

loose

reinforcement

to

drift

or

relocate
.



Each

intersection

is

fastened

by

either

a

soft

wire

tie

or

weld