columns - wifistudy.com · civil engineering by sandeep jyani. que. minimum diameter of...

Columns• A column may be defined as element used primarily to support axial compressive

loads and with a height of at least three times its least lateral dimension

• Pedestal: It is a short column of effective length not greater than 3 times of least lateral dimension

• In case of pedestal in which the Longitudinal reinforcement is not taken in account in strength calculations, nominal longitudinal reinforcement not less than 0.15 percent of the cross-sectional area shall be provided.

𝒙 𝒙

𝒚

𝒚

𝝀 =𝑳𝒆𝒇𝒇𝒆𝒄𝒕𝒊𝒗𝒆𝑳𝑳𝑫

< 𝟑

Civil Engineering by Sandeep Jyani

Effective Length of column


Que. Effective length of column recommended

by code for a column held in position and

restrained against rotation in both ends is

(a) 0.8 L

(b)0.65L

(c)L

(d)2L


Typical Columns

LongitudinalReinforcement

Ties

Shell

core

1. Tied Column 2. Spiral Column

Structural Steel pipeConcrete

3. Composite Column


For columns, As per IS 456:2000, CL 26.5.3

1. Minimum percentage of steel= 0.8%

2. Maximum percentage of steela) 4% if bar are lapped

b) 6% if bars are not lapped

3. Minimum diameter of longitudinal bars = 12mm

4. Minimum number of bars a) For circular=6

b) For Rectangular=4

5. Maximum spacing of longitudinal bars = 300mm


As per IS code6. Load Carrying capacity of column is increased by 5%

percent when helical reinforcement is provided as a transverse reinforcement

7. Maximum compressive strain in concrete in axial compression is taken to be 0.002

8. Pitch and diameter of lateral tiesA. The pitch of transverse reinforcement shall not more than

the least of the following distances:a) The least lateral dimension of the compression members;b) Sixteen times the smallest diameter of the longitudinal

reinforcement bar to be tied, andc) 300 mm

B. Diameter-A. The diameter of the polygonal links or lateral ties shall not be less

than one fourth of the diameter of the largest longitudinal bar and in no case less than 16mm i.e.

• Greater of ൝𝑑𝑖𝑎 𝑜𝑓𝑚𝑎𝑖𝑛 𝑏𝑎𝑟

4

6 𝑚𝑚


Que. Minimum diameter of longitudinal bars in

columns is

(a) 6 mm

(b)8 mm

(c)12 mm

(d)16 mm


Que. In limit state of collapse for

direct compression, the maximum

axial compressive strain in concrete

is

(a)0.002

(b)0.003

(c)0.0035

(d)0.004


Que. In limit state of collapse for

direct compression, the maximum

axial compressive strain in concrete

is

(a)0.002 compression

(b)0.003

(c)0.0035 (axial compression and bending)

(d)0.004


Que. The diameter of transverse

reinforcement of columns should be equal

to one fourth of the diameter of the main

steel rods but not less than

a) 4mm

b) 5mm

c) 6mm

d) 7mm


Que. Spacing between longitudinal

bars measured along the periphery of

RCC columns should not exceed

a) 150mm

b) 250mm

c) 300mm

d) 500mm


Que. The limit of percentage of

longitudinal reinforcement in a

column is given by

a) 0.15 - 2%

b) 0.8 - 4%

c) 0.8 - 6%

d) 0.8 – 8%


Que. The limit of percentage of longitudinal

reinforcement in a column is given by

a) 0.15 - 2%

b) 0.8 - 4%

c) 0.8 - 6%

d) 0.8 – 8%


As per IS code

7. Pitch and diameter of lateral tiesA. The pitch of transverse reinforcement shall not more

than the least of the following distances:a) The least lateral dimension of the compression members;

b) Sixteen times the smallest diameter of the longitudinal reinforcement bar to be tied, and

c) 300 mm

B. Diameter-A. The diameter of the polygonal links or lateral ties shall not be

less than one fourth of the diameter of the largest longitudinal bar and in no case less than 16mm i.e.

• Greater of ൝𝑑𝑖𝑎 𝑜𝑓 𝑚𝑎𝑖𝑛 𝑏𝑎𝑟

4

6 𝑚𝑚


Que. The pitch of lateral ties should not

exceed

a) The least lateral dimension

b) 16 times the diameter of longitudinal

bars

c) 300mm

d) All of these


Que. The minimum number of longitudinal

bars provided in rectangular RCC column

a) 2

b) 4

c) 6

d) 8


Que. The minimum number of

longitudinal bars provided in

rectangular RCC column

a) 2

b) 4

c) 6

d) 8


Que. The diameter of transverse

reinforcement of columns should be

equal to one fourth of the diameter

of the main steel rods but not less

than

a) 4mm

b) 5mm

c) 6mm

d) 7mm


Minimum Eccentricity𝑒𝑚𝑖𝑛 ≥

𝑙

500+𝐷

30

> 20𝑚𝑚

Where 𝑙 = 𝑢𝑛𝑠𝑢𝑝𝑝𝑜𝑟𝑡𝑒𝑑 𝑙𝑒𝑛𝑔𝑡ℎ𝑜𝑓 𝑡ℎ𝑒 𝑐𝑜𝑙𝑢𝑚𝑛 𝑖𝑛 𝑚𝑚

𝐷 = 𝑙𝑎𝑡𝑒𝑟𝑎𝑙 𝑑𝑖𝑚𝑒𝑠𝑖𝑜𝑛 𝑜𝑓 𝑐𝑜𝑙𝑢𝑚𝑛 𝑖𝑛 𝑡ℎ𝑒𝑑𝑖𝑟𝑒𝑐𝑡𝑖𝑜𝑛 𝑢𝑛𝑑𝑒𝑟 𝑐𝑜𝑛𝑠𝑖𝑑𝑒𝑟𝑎𝑡𝑖𝑜𝑛 𝑖𝑛 𝑚𝑚

𝑃 𝑃

𝒆 =𝑴

𝑷

𝑫

𝒃

↷𝑴


Design of Column1. Short Column

• Load carrying capacity:𝑃 = 𝑃𝑠𝑡𝑒𝑒𝑙 + 𝑃𝑐𝑜𝑛𝑐𝑟𝑒𝑡𝑒

= 𝜎𝑠𝐴𝑠 + 𝜎𝑐𝐴𝑐𝑆𝑖𝑛𝑐𝑒 𝑇𝑜𝑡𝑎𝑙 𝐴𝑟𝑒𝑎 𝐴 = 𝐴𝑠 + 𝐴𝑐⇒ 𝑷 = 𝝈𝒔(𝑨 − 𝑨𝒄) + 𝝈𝒄𝑨𝒄

𝑨

𝑨𝒄

𝑨𝒔

2. Long Column• Load carrying capacity:

⇒ 𝑷 = 𝑪𝒓{𝝈𝒔(𝑨 − 𝑨𝒄) + 𝝈𝒄𝑨𝒄}

Where 𝑪𝒓 = 𝟏. 𝟐𝟓 −𝑳𝒆𝒇𝒇

𝟒𝟖𝑳𝑳𝑫𝒇𝒐𝒓 𝑹𝒆𝒄𝒕𝒂𝒏𝒈𝒖𝒍𝒂𝒓 𝒐𝒓 𝒔𝒒𝒖𝒂𝒓𝒆 𝒄𝒐𝒍𝒖𝒎𝒏

And 𝑪𝒓 = 𝟏. 𝟐𝟓 −𝑳𝒆𝒇𝒇

𝟏𝟎𝟎𝑳𝑳𝑫𝒇𝒐𝒓 𝒄𝒊𝒓𝒄𝒖𝒍𝒂𝒓 𝒄𝒐𝒍𝒖𝒎𝒏 (𝜸𝒎𝒊𝒏 = 𝑫/𝟒)


Design of Column3. Circular Column

a) With separate ring used as a stirrup:𝑷 = 𝑪𝒓{𝝈𝒔𝑨𝒔+ 𝝈𝒄𝑨𝒄}


Design of Column3. Circular Column

b) With helical reinforcement𝑷 = 𝟏. 𝟎𝟓 × 𝑪𝒓 × {𝝈𝒔𝑨𝒔+ 𝝈𝒄𝑨𝒄}

For helical reinforcement, following criteria has to be satisfied𝟎. 𝟑𝟔𝒇𝒄𝒌

𝒇𝒚

𝑨𝒈

𝑨𝒄

− 𝟏 ≤𝑽𝒉

𝑽𝒄

• 𝑨𝒈 = 𝒈𝒓𝒐𝒔𝒔 𝒂𝒓𝒆𝒂 =𝝅

𝟒𝑫𝒈

𝟐

• 𝑨𝒄 = 𝒄𝒐𝒓𝒆 𝒂𝒓𝒆𝒂

• 𝑽𝒉 = 𝒗𝒐𝒍𝒖𝒎𝒆 𝒐𝒇 𝒉𝒆𝒍𝒊𝒄𝒂𝒍 𝒓𝒆𝒊𝒏𝒇𝒐𝒓𝒄𝒆𝒎𝒆𝒏𝒕= 𝒂𝒓𝒆𝒂 𝒐𝒇 𝒉𝒆𝒍𝒊𝒄𝒂𝒍 𝒓𝒇 × 𝒍𝒆𝒏𝒈𝒕𝒉 𝒊𝒏 𝒐𝒏𝒆 𝒍𝒐𝒐𝒑 × 𝒏𝒐. 𝒐𝒇 𝒕𝒖𝒓𝒏𝒔

=𝝅

𝟒∅𝒉

𝟐× 𝝅𝑫×𝟏𝟎𝟎𝟎

𝒑𝒊𝒕𝒄𝒉

• 𝑽𝒄 = 𝒗𝒐𝒍𝒖𝒎𝒆 𝒐𝒇 𝒄𝒐𝒓𝒆 𝒇𝒐𝒓 𝟏𝒎= 𝟏𝟎𝟎𝟎𝒎𝒎×𝑨𝒄𝒐𝒓𝒆

= 𝟏𝟎𝟎𝟎 ×𝝅

𝟒𝑫𝒄

𝟐

• 𝑫𝒉 = 𝒅𝒊𝒂 𝒐𝒇 𝒄𝒆𝒏𝒕𝒓𝒆 𝒕𝒐 𝒄𝒆𝒏𝒕𝒓𝒆 𝒉𝒆𝒍𝒊𝒄𝒂𝒍 𝒔𝒕𝒊𝒓𝒓𝒖𝒑

𝒑 = 𝑷𝒊𝒕𝒄𝒉 𝒐𝒇𝒉𝒆𝒍𝒊𝒙

𝑫𝒉𝑫𝒈 𝑫𝒄


Que. Load Carrying capacity of column is

increased by …… percent when helical

reinforcement is provided as a transverse

reinforcement

(a) 5%

(b) 4%

(c) 6%

(d) 0.05%


Que. Load Carrying capacity of column is

increased by …… percent when helical

reinforcement is provided as a transverse

reinforcement

(a) 5%

(b) 4%

(c) 6%

(d) 0.05%


𝑷 = 𝟏. 𝟎𝟓 × 𝑪𝒓 × {𝝈𝒔𝑨𝒔 + 𝝈𝒄𝑨𝒄}

UTTAR PRADESH PUBLIC SERVICE COMMISSION

Combined State Engineering Services

(General Recruitment/Special Recruitment)

EXAM DATE07 JUNE 2020

692 VACANCIES

SANDEEP11

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columns - wifistudy.com · civil engineering by sandeep jyani. que. minimum diameter of...

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