This document discusses columns in construction. It includes: 1. A list of group members for a project on columns. 2. Descriptions of different types of columns - long columns which can buckle, short columns which fail from crushing, and intermediate columns which can crush and buckle. 3. The construction process for reinforced concrete columns including layout, reinforcement, forming, and pouring concrete. 4. Potential failure modes of columns from compression failure, buckling, or a combination of both. 5. Definitions of terms like slenderness ratio, crippling/buckling load, and uniaxially loaded/eccentrically loaded columns.

2. Group members
1-Muzammil Hussain
2- Umair Niazi
3-Zamin Haider
4-Hassan Raza
5-C.Muhammad
6-Aqeel Hamza

3. Muzammil Hussain

4. WHAT IS COLUMN?
 Column is a vertical structural member. It
transmits the load from ceiling/roof slab
and beam, including its self-weight to the
foundation. Columns may be subjected to
a pure compressive load. R.C.C. columns
are the most widely used now-a-days.

5. Columns
 Columnscarry primary Axial Loads and thereforeare
designed forcompression.
 Additional loads from snow, wind orother horizontal
forces can cause bending in thecolumns.
 Columns then need to bedesigned forAxial Load and
Bending.

6. Columns History
Like many of our English-language
words, column originates from Greek and Latin words.
The Greek kolophōn, meaning a summit or hill, was
where temples were built in places like Colophon .The
ideas of columns in Western civilizations come from the
Classical architecture of Greece and Rome. Classical
columns were first described by an architect named
Vitruvius (c. 70-15 BC). Further descriptions were
written in the late 1500s by the Italian Renaissance
architect Giacomo da Vignola.

7. Column Forces
F External
WCOL (External
R1 (Internal)
R2 (Internal)
RSoil (External)
WFTG (External)
Horizontal loads caused by wind,
snow, seismic or internal building
load

8. COLUMN LOAD TRANSFER FROM
BEAMS

9. What is the definition of the slenderness
ratio of a column?
 Slenderness ratio is the ratioof the length of a column
and the least radius of gyration of itscross section
 Often denoted bylambda
 λ = le/rmin

10. Umair Khan

11. Radius of gyration
nd A is the
Radiusof gyration is used todescribe thedistribution
of cross sectional area in a columnaround
its censorial axis. The radius of gyration is given by the
following formula.
 R.g= i/A
 Where I is the second moment of inertia.a
total cross-sectionalarea.

12. Uses of slenderness ratio
 It is used extensively for finding out thedesign load as
well as in classifying various columns in
short/intermediate/long
 Example-
Short Steel column - lambda is less than 50.
Intermediate - 50 -250
Long - 250 above.

13. Why this is important?
 Long columns undercompression can fail via both
buckling (bending side ways) as well as crushing.
Various formulas to calculate such failure
characteristics extensivelyuse the useof this ratio.

15. Types Of Columns
 Long Columns
 Short (Strut) Columns
 Intermediate Columns

16. Long Column
When the ratioof effective length to the least radius of
gyration is greater than 45, then it iscalled a long column.
A long column is subjected to bendingmoment
inaddition to direct compressive stress.
The load carrying capacityof a long column is less than a
short column
The load carrying capacityof a long column depends upon
slenderness ratio (slenderness ratio increases then the
capacity of the columndecreases)

17.  LONG COLUMN :
 When length of column is moreas compared to
its lateral dimension, it is called long column.
Long Column
Le/rmin >50
Where,
Le = effective length of column
rmin = Minimum radius of gyration

18. Real world example:
 Here in picture we can see long columns on front of
building in “The White house” WashingtonD.C(USA).

19. Short Column:

When the ratioof effective length to the least lateral
dimensions of the column is less than 12, then it is
called a shortcolumn.
(or)
When the ratioof effective length to the least radiusof
gyration is less than 45, then it is called a shortcolumn

20. SHORT COLUMN :
 When length of column is lessas compared to its
lateral dimension, it is called Shortcolumn.
Short Column
Le/rmin <50
Or,
Le/d < 15
 Crushing Load : The load atwhich shortcolumn fails
by crushing is called crushingload.

21. INTERMEDIATE COLUMN:
Column is intermediatewhen
4d < L < 30d
and
30 < Le /r min < 100 or Critical slendernessratio.

22. INTERMEDIATE COLUMN:
Column is intermediatewhen
4d < L < 30d
and
30 < Le /r min < 100 or Critical slendernessratio.

23. Zamin Haider

24. Column Construction
process
 Constructing RCC (Reinforced Cement Concrete)
Column involves following four stages of works.
1. Column Layout work.
2. Column Reinforcement work.
3. Column Formwork.
4. Pouring Concrete into column.

25. 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.

26. 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)

27. 3. Column
formwork
Column formwork is a term used for structures that are used
to support forms or molds for poured concrete columns. It
can be as simple as a reinforced cardboard tube for small
cylindrical columns or very complex forms constructed
from many pieces of wood and metal

28. 4. Pouring concrete into
column
For small quantity of concrete volume we normally
depend on machine-mix concrete and for large concrete
quantity we order ready-mix concrete.
Because, if you use moving pump with ready-mix concrete
and if you want not to exceed 5 feet height range for
dropping concrete that would be difficult

29. Curing
Concrete which is moist cured for 7 days is
about 50% stronger than uncured concrete

30. Chaudhry Muhammad

31. Failure Modes of COLUMN
 Column may fail in oneof three condition
 Compression failure of concrete orsteel
reinforcement
 Buckling
 Combinationof buckling and compression failure
 Compression failure is likely tooccurwith columns
which are short andstocky.
 Buckling is probablewith columnwhich are long and
slender

32. Failure modes of columns
Compression
failure Buckling

34. CRIPPLING LOAD OR BUCKLING
LOAD
 The load at which, long column starts buckling(bending)is
called buckling load or crippling load.
 Buckling of column depends upon the followingfactors.
1. Amount of load.
2. Length of column
3. End condition of column
4. C/s dimensions of column
5. Material of column.

35. Failure Modes
 Short Columns – fail by crushing
(“compression blocks or piers” Engel)
 fc = Actual compressive stress
 A = Cross-sectional area of column(in2)
 P = Load on the column
 Fc = Allowable compressive stress per codes
 Intermediate Columns – crush and buckle
(“columns” Engel)
 Long Columns – fail by buckling
(“long columns” Engel)
 E = Modulus of elasticity of the columnmaterial
 K = Stiffness (curvature mode) factor
 L = Column length between pinned ends(in.)
 r = radius of gyration = (I/A)1/2
c c
A
f 
P
 F

r

 
 KL
fcr  2  Fcr
2
E

36. Aqeel Hamza

37. WHAT IS UNIAXIALLY LOADED
COLUMN?
WHEN A COLUMN IS SUBJECTED
TO EITHER COMBINED AXIAL
COMPRESSION (P) AND
MOMENT (M) AS IN FIG-1 OR
ONLY AXIAL LOAD (P) APPLIED
AT AN ECENTRICITY e=(M/P) AS
IN FIG-2 SO THAT THE COLUMN
IS TRYING TO BEND ABOUT
ONLY ONE AXES OF THE
COLUMN CROSS SECTION IS
KNOWN AS UNIAXIALLY
LOADED COLUMN.

38. CROSS SECTION OF UNIAXIALLY
LOADED COLUMN

39. IN THIS CASE,COLUMNS
ARE SUBJECT TO
TENSION OVER A PART
OF THE SECTION AND
IF OVERLOADED MAY
FAIL DUE TO TENSILE
YIELDING OF THE
STEEL ON THE SIDE
FARTHEST FROM THE
LOAD.

40. Eccentric Loaded Columns
When the load acting on the
column is offset from the
centroid of the column, then
it establishes the bending of
column along with the axial
stress. This offset loading of
the column is referred as
eccentric loading.

41. Eccentric loading will not be at the middle of cross-
section of the column. It will be at some distance from
the middle of the column either towards right or left
corners of the column. The distance between the
middle of cross-section of the column and the eccentric
load is referred as eccentricity symbolized by e.
Increase in the eccentric load increases the axial load
and the moment acting on the column. This makes the
column to bend additional increasing the bending of
column.