3. RCC Columns
Reinforced Concrete Column is a structural
member designed to carry compressive
loads, composed of concrete with an
embedded steel frame to provide
reinforcement. For design purposes, the
columns are separated into two categories:
short columns and slender columns.
4. Types of Columns
based on height-width ratio
Short Columns
The strength of short columns is controlled by the strength of the material and
the geometry of the cross section. Reinforcing rebar is placed axially in the
column to provide additional axial stiffness
Long Columns
Long columns are those which have a height and cross sectional dimension
ratio more than 1:12. these columns are usually weaker than short columns of
same cross sectional area and are not generally preferred.
5. Types of Columns
based on their shape
• Spiral Columns
Spiral columns are cylindrical columns with a continuous helical bar
wrapping around the column. The spiral acts to provide support in
the transverse direction and prevent the column from barrelling. The
amount of reinforcement is required to provide additional load-
carrying capacity greater than or equal to that attributed from the
shell as to compensate for the strength lost when the shell spalls off.
With further thickening of the spiral rebar, the axially loaded concrete
becomes the weakest link in the system and the strength contribution
from the additional rebar does not take effect until the column has
failed axially. At that point, the additional strength from spiral comes
into play and prevents catastrophic failure, instead giving rise to a
much slower ductile failure.
6. • Tied Columns
Tied columns have closed lateral ties spaced approximately
uniformly across the column. The spacing of the ties is limited
in that they must be close enough to prevent barrelling failure
between them, and far enough apart that they do not interfere
with the setting of the concrete. The ACI codebook puts an
upward limit on the spacing between ties.
If the ties are spaced too far apart, the column will
experience shear failure and barrel in between the ties
7. Process of
Construction
RCC (Reinforced Cement Concrete) column is a
structural member of RCC frame structured
building. It's a vertical member which transfers
loads from slab and beam directly to
subsequent soil.
A whole building stands on columns. Most of
the building failure happens due to column
failure. And most of the column failure
happens not for design fault but for the poor
construction practice. So, it is very important to
know the construction process of the RCC
column properly.
8. General Steps
Constructing RCC (Reinforced Cement Concrete) Column involves following four
stages of works -
• Column layout work
• Column reinforcement work
• Column formwork, and
• Pouring concrete into column.
9. STEP 1.
Column layout work: In this stage of works the location of columns are
determined practically in field. It is done by laying rope according to grids
shown in the drawing and then mark the location of columns related to rope.
In drawing, column locations are shown related to grid-line with dimension.
Practically, in field, ropes are our grid-line. So we place columns related to
rope-line by measuring dimension shown in the drawing.
STEP 2.
Column Reinforcement work: After marking the column locations, we then
start to place reinforcement as instructed in the structural drawing.
This is normally described in the drawing like -
C1-12#16 mm⌀ and stirrup-10 mm⌀ @ 4" c/c.
That means column C1 will have 12 numbers of 16 mm diameter bar as
vertical bar and 10 mm diameter steel should be placed 4 inch center to
center as stirrup.
or
C2-8#20 mm⌀ + 10#16 mm⌀ and stirrup-10 mm⌀ @ (4"+6”) c/c.
10. SPECIFICATIONS
This is normally described in the drawing like -
C1-12#16 mm⌀ and stirrup-10 mm⌀ @ 4" c/c.
That means column C1 will have 12 numbers of
16 mm diameter bar as vertical bar and 10 mm
diameter steel should be placed 4 inch centre to
centre as stirrup.
or
C2-8#20 mm⌀ + 10#16 mm⌀ and stirrup-10 mm⌀
@ (4"+6”) c/c.
This C2 column's reinforcement specification
means that it'll have 8 numbers of 20 mm
diameter bar as well as 10 numbers of 16 mm
diameter bar as vertical reinforcement and
(4"+6") centre to centre of stirrups placement
means middle-half portion of clear height of
column will have 6" centre to centre spacing of
stirrups and upper one-fourth as well as bottom
one-fourth height of column's clear height will
hold stirrups at 4" centre to centre spacing.
11. STEP 3.
Column formwork: In building, floor height is normally kept 10 feet. If the slab has beam then we
have to pour concrete up to beam bottom level. Suppose, beam height specified in drawing is 1'-6".
So, the casting height of our column will be 8'-6". And our formwork height will be 8'-6". But one thing
should be considered here is that dropping concrete from above 5' height isn't suggested during
pouring. Because it leads concrete segregation. So we should make one-side of column formwork
within 5 feet height range. After casting 5 feet of column, we just lift the short side up to full-casting
height of column next day.
Another way to cast column without segregation is to keep a small window at 5 feet level of full-
height formwork. After casting up to that level, close the window and cast the rest of the column.
STEP 4.
Pouring concrete into column: Casting column is easy. For small quantity of concrete volume normally
constructors depend on machine-mix concrete and for large concrete quantity and order ready-mix
concrete.
Because, if moving pump with ready-mix concrete is used to not exceed 5 feet height range for
dropping concrete that would be difficult.
Leave it to dry for 3-4 days by regularly watering the freshly casted column.
13. RCC Beams
A beam is a structural elements that is capable of withstanding load primarily by resisting
against bending. The bending force induced into the material of the beam as a result of the
external loads, own weight, span and external reactions to these loads is called a bending
moment. Beams are characterized by their profile (shape of cross-section), their length, and
their material.
Concrete can provide a cost effective solution offering a composite beam and floor solution
which will reduce overall depth and weight with connections developed to your requirements.
Beams are traditionally descriptions of building or civil engineering structural elements, but
smaller structures such as truck or automobile frames, machine frames, and other mechanical
or structural systems contain beam structures that are designed and analysed in a similar
fashion.
14. Introduction to
Beams
Historically beams were squared timbers but are also
metal, stone, or combinations of wood and metal such as
a flitch beam. Beams generally
carry vertical gravitational forces but can also be used to
carry horizontal loads (e.g., loads due to an earthquake or
wind or in tension to resist rafter thrust as a tie beam or
(usually) compression as a collar beam). The loads carried
by a beam are transferred to columns, walls, or girders,
which then transfer the force to adjacent
structural compression members. In light frame
construction joists may rest on beams.
15. Classification of beams
on the basis of supports
Classification of beams based on supports:
• Simply supported - a beam supported on the ends which are free to rotate and have no
moment resistance.
• Fixed - a beam supported on both ends and restrained from rotation.
• Over hanging - a simple beam extending beyond its support on one end.
• Double overhanging - a simple beam with both ends extending beyond its supports on
both ends.
• Continuous - a beam extending over more than two supports.
• Cantilever - a projecting beam fixed only at one end.
• Trussed - a beam strengthened by adding a cable or rod to form a truss
17. Types of beams
• Edge/Spandrel Beams – span around perimeter to provide a bearing edge on one side
for flooring slabs and structure above.
• Spine Beams - Provide a bearing edge on two sides for flooring slabs.
• Lintel Beams - Span over door or window opens, to provide bearing for structure above.
• Balcony Beams - These are beams cast with an integral balcony.
• Raker Beams – Can be designed and supplied with required bearing for terracing units.
18. Thin walled
beams
A thin walled beam is a very useful type of beam (structure). The
cross section of thin walled beams is made up from thin panels
connected among themselves to create closed or open cross
sections of a beam (structure).
Typical closed sections include round, square, and rectangular
tubes. Open sections include I-beams, T-beams, L-beams, and so
on.
Thin walled beams exist because their bending stiffness per unit
cross sectional area is much higher than that for solid cross
sections such a rod or bar. In this way, stiff beams can be
achieved with minimum weight. Thin walled beams are
particularly useful when the material is a composite laminates.
19. Construction of
Beams
• Lay down the steel beam - as the adjacent picture shows beams are the core of the plinth
beam. Beams have a loop every 6" that holds it together.
• Setup re-inforcement - before concrete is poured, re-inforcement has to be established to provide
rectangular shape to the beam. This takes majority of effort as planks have to be nailed properly
in place and once concrete is poured they need to be removed.
• Pour the concrete - next step is to pour the concrete. As concrete is poured, mason ensures that it
is evenly spread and smoothens out any edges. He also needs to ensure the height of the beam is
consistent throughout the periphery.
• Remove re-inforcement - concrete turns solid within 24-hour and final step is to remove the
planks leaving the beam intact.
