Skip to main content

RCC (Reinforced Cement concrete) column specifications



RCC (Reinforced cement concrete) Column/Strut

All details about the Column (a compression member in structure)

Column -Reinforced concrete columns are
used to transfer the load of the structure to its foundations. These are reinforced by means of main longitudinal bars to resist compression and/or bending; and transverse steel (ties) to resist bursting force.



The column or strut is a vertical compression member, the effective length of which exceeds three times its least lateral dimension(LLD).

(A) LongItudInaI Reinforcement-

In a reinforced column, the area of
longitudinal reinforcement shall not be less than 0.8 percent nor more than 6 percent of the gross cross-sectional area of the column.

The area of longitudinal reinforcement should normally not exceed 4 percent of the gross cross sectional area of the column. This percentage can be considered as the maximum from practical considerations.

However where bars from one column have to be lapped with those of another column above, the total maximum percentage of 6 percent may be allowed at the lapping. Proper placing and compacting of concrete should be ensured at the place of lapping.

 A minimum number of 4 bars shall be
provided in a rectangular column and 6 bars in a circular column with helical reinforcement.

 The bars shall be not less than 12 mm in diameter and spacing of the bars along the periphery of the column shall not exceed 300 mm.

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

Note - Pedestal is a compression member. the effective length of which does not exceed 3 times the least lateral dimension.

#Dowels and Bar supports-

Dowel and bar supports, spacer bars, bar chairs etc.,should be specifically listed on the structural drawing and should be schedule in that portion of the structure in which they are first required so that they can,be delivered wtth reinforcement and are available for placement in time.
Footing dowles shall be scheduled with footings rather than in column.


(B)Transverse Reinlorcement

 A reinforcement concrete compression
member shall have transverse or helical
reinforcement so disposed that every longitudinal bar nearest to the compression face has effective lateral support against buckling. The effective lateral support is given b transverse reinforcement either in the form of circular rings capable
of taking up circumferential tension or by
polygonal links (lateral ties) with internal angIe not exceeding 135°.

# Pitch and Diameter of Lateral Ties

 Pitch-The pitch of the transverse
reinforcement shall not be more than the least of the following distances(.see in fig. Below 7.6A)
a) the least lateral dimension of the compression member,
b) sixteen times the smallest diameter of the longitudinal reinforcing bar to be tied, and
c) forty eight times the diameter of the transverse reinforcement.

 Diameter -The diameter of the polygonal links or lateral ties shall not be less
than one-fourth of diameter of the largest
longitudinal bar, and in no case less than 5 mm.





# Helical Reinforcement (Spirally Reinforced)(see in above fig. 7.6B)

Pitch - Helical reinforcement shall
be of regular formation with the turns of the helix spaced evenly and its ends shall be anchored properly by providing one and a half extra turns of the spiral preferably with a 135° hook.

Thepitch of the helical turns shall be not more than 75mm or one-sixth of core diameter of the column, nor less than 25 mm or 3 times thediameter of steel bar forming helix.

Tension lap length shall be provided at lap splices.

NOTE - It is important to note that when the ratio of the volume of helical reinforcement provided to the volume of  the core greater than

0.36 ((As/Ac)-1)*(fck/fy)

 the strength of the compression member may be increased by 1.05 times the strength of similar member with lateral ties.

where
As= gross area of the section,

Ac = area of the corn of the helically reinforced column measured to the outside diameter of the helix,

fck = characteristic compressive strength of the concrete

and
fy= characteristic strength of the helical reinforcement
but not exceeding 415 N/mm^2

 Diameter -The diameter shall be not less than one-fourth of the diameter of the largest longitudinal bar, and in no case less than 5 mm.

#Temporary stirrups

At least two temporary stirruls should be provided to hold splices in position(see in fig. Below) or to stiffen the helically bound columns during fabrication.
The stirrups coming above the floor shall not be removed until the next column is erected.

#Large columns

Where reinforcement for very wide columns is to be fabricated in separate cages and erected in sections,they should be held together by at least 12 mm diameter bars spaced at double the stirrup spacing.(see in fig.below).







Thank you
Mukesh kumar (Gyan of engineering)

Comments

Popular posts from this blog

Granular Sub base (GSB) specifications, GSB Grading, layer thickness, Water absorption, Physical requirements (like liquid limit, Plasticity index ,AIV), construction procedure or Rolling , measurement and treatment of GSB as per MORTH 5th revision and Indian standard in Civil engineering

Granular sub-base (GSB) SUB BASE (GSB)– The full form of GSB is granular sub base.it is being laid in road work because it plays two major roles 1- it works as  drainage layer 2- it provides a good sub base to laid base layer on it. How to calculate the quantity, compaction factor value and loose thickness of GSB? To know more information kindly visit on below link 🔗  www.gyanofcivilengineering.com/granular sub-base(GSB) Quantity. Material –     The material to be used for the work shall be natural sand, crushed   gravel, crushed stone, crushed slag, or combination thereof depending upon the grading required use of material like brick metal, kankar and crushed concrete shall be permitted in the lower sub base. The material shall be free from organic or other deleterious constituents. Grading III and IV shall be used in lower sub base. Grading V and VI shall be used as sub-base-cum-drainage layer. Where the sub-base is laid in two layers as upper sub-base and lowe

Wet Mix Macadam (WMM) technical specifications as per MORTH and Indian standard in Civil engineering

WET MIX MACADAM (WMM) sub – base /base:- Wet mix macadam (WMM) act as a base course just below the bituminous layer (bitumen base course or surface course).  The thickness of a single compacted Wet mix macadam(WMM)  layer shall not be less than 75mm.when vibrating or other approved types of compacting equipment are used, the compacted depth of a single layer of the sub-base course may be up to 200mm. How to calculate the loose thickness of WMM, compaction factor and quantity of WMM ? Kindly visit on below link 🔗 https://www.gyanofcivilengineering.com/2020/05/wet-mix-macadam-wmm-quantity-compaction.html Physical requirements   Material finer than 425 micron shall have plasticity index (PI) not exceeding 6. To determine this combined portion, the flaky stone from a representative sample should first be separated out. Flakiness index is weight of flaky stone metal divided by weight of stone sample. Only the elongated particles are separated out from

Full form of various terms used in civil engineering /highway engineering or road work

Full Form of various  terms used in civil engineering  (Highway and expressway)  List of various  acronyms or abbreviations used in civil engineering  TBM- Temporary Bench mark (टे᠎म्‌प्‌ररि बेंच मार्क) BM- Bench Mark ( बेंच मार्क ) / Bituminous Macadam ( बिटुमिनस मैकडम) MSL- Mean Sea Level (मीन सी लेवल) BS- Back sight( बैक साइट) FS - Fore sight  (फोर साइट) HI - Height of Instrument ( हाइट आंफ इन्‌स्‍ट्रमन्‍ट्‌) TS-  Total Station (टोटल स्टेशन) GPS- Global Positioning System (ग्लोबल पोजिशनिंग सिस्टम) ROW- Right of Way (राइट ऑफ वे) MTV- material Transport vehicle (मटेरियल ट्रांसपोर्ट वहीकल) NGL- Natural Ground Level (नेचुरल ग्राउन्‍ड्‌ लेवल ) OGL- Original Ground level (अˈरिजन्‌ल्‌ ग्राउन्‍ड्‌ लेवल ) C&G- Clearing and Grubbing ( क्लियरिंग और ग्रबिंग) EMB- Embankment SG- Subgrade (सबग्रेड) GSB- Granular sub-base WMM- Wet Mix Macadam ( वेट मिक्स मैकडैम) WBM- Water Bound Macadam (वाटर बाउंड मैकडैम) DBM- Dense Bituminous Macadam SDBM- Semi- Dense Bitumino

WMM(Wet Mix Macadam) quantity / Compaction Factor value for WMM / Loose thickness of WMM Layer

Wet Mix Macadam (WMM) quantity / Compaction Factor value for WMM / Loose thickness of WMM Layer  In this article we shall discuss three important points about wet Mix Macadam (WMM) 1- How can we calculate the required WMM  quantity?  2 -  What is value of compaction factor for WMM? 3- How much loose thickness should be taken to get proper compacted layer thickness ?  1- How can we calculate the required WMM quantity? Let us consider Length of WMM Bed(L) = 1 Km = 1000 Met. Breadth of WMM Bed(B)= 7 Met. Thickness of WMM Layer (T)  = 150 mm =0.150 Met. Max. Dry Density (MDD) =2.230 Gram/ Cubic Centimeter = 2230KG/ Cubic metre Note -  The value of MDD is calculated by conducting proctor density test as per IS 2720 (part -28) : 1983 (Reaffirmed - May 2015). Then Volume of WMM Layer = ( Length of WMM Bed X Width of WMM Bed X Thickness of WMM Layer) Volume of WMM Layer = L X B X T  Volume of WMM Layer   = 1000 X 7 X 0.150  Volume of WMM Layer    = 1050 C

Difference between nominal mix and design mix of concrete

Difference between nominal mix and design mix of concrete - Concrete is most extensively used mix to achieve desired properties of structure. There are two methods to prepare the concrete mix. 1-Nominal mix 2- Design mix Nominal mix - Nominal mix specifies the fix proportion of the cement , sand and aggregates. Ingredients of concrete are mixed on the basis of volume. It is a site level mixing of ingredients to prepare concrete mix. Such type of concrete mix is generally used in small quantity or where load is not high. There are many grade of nominal mix concrete like M-5, M-7.5, M-10, M-15 and M-20. In above grades of concrete mix  the letter 'M' refers to Mix where as the value like 5,7.5,10,15 etc indicates the compressive characteristic strength of concrete after 28 days in specified conditios. Unit of this compressive characteristic strength of concrete is  Newton /mm 2. The ratio of various grade of concrete is being given below - M-5 

Dense Bituminous Macadam (DBM) or Bituminous Concrete (BC) layer Quantity / Compaction Factor value / Loose thickness calculation

Dense Bituminous  Macadam (DBM) or   Bituminous Concrete (BC)  quantity / Compaction Factor value for DBM or BC / Loose thickness of DBM or BC Layer  In this article we shall discuss three important points about Dense Bituminous   Macadam (DBM) or Bituminous Concrete (BC) 1- How can we calculate the required DBM/BC quantity?  2 -  What is value of compaction factor for DBM/BC? 3- How much loose thickness should be taken to get proper compacted layer thickness ?  1- How can we calculate the required DBM/BC quantity? Let us consider Length of  DBM/BC layer (L) = 1 Km = 1000 Met. Breadth of DBM/BC Layer (B)= 5 Met. Thickness of DBM/BC Layer (T)  = 50 mm =0.050 Met. Max. Dry Density (MDD) =2.441 Gram/ Cubic Centimeter = 2441KG/ Cubic metre Note  -  The value of MDD is calculated by conducting suitable test . Then Volume of DBM/BC Layer = ( Length of DBM/BC layer X Width of DBM/BC layer  X Thickness of DBM/BC Layer) Volume of DBM/BC Layer = L X B X T Volume o

DBM (Dense Bituminous Macadam) specificatins,layer thickness, physical requirements, aggregate size, grades and its measurements

 DENSE BITUMINOUS MACADAM(DBM) DBM acts as a bituminous  base course and thickness of a single compacted  layer shall be 50 mm to 100 mm.  In this article we shall discuss about Technical specifications of DBM (Dense Bituminous Macadam), layer thickness, physical requirements, aggregate size, grades and its measurements A-Scope : The work shall consist of construction in a single layer of DBM on a previously prepared base or sub-base. The thickness of a single layer shall be 50 mm to 100 mm. B - Material : The choice of binder material shall be stipulated in the contract or by the engineer, where viscosity grades of bitumen are specified, they are referred to by a designation in accordance with IS: 73. Where modified bitumen is specified, it shall conform to the requirements of IRC:SP:53 and IS:15462. Selection criteria for viscosity grade bitumen based on highest and lowest daily mean temperatures at a particular site are ]given in table no -1. 1-Coarse Agg

Civil engineering interview questions in Roadway/Highway /Expressway department

  Welcome friends, We shall learn about the various questions which are frequently ask by an  interviewer In the field of infrastructure.  So let's get start....... EMBANKMENT/SUBGRADE/BORROW AREA •Liquid Limit  <50% •Plastic Limit  < 25% •Proctor Density(Min. Value) For Embankment =1.52 to 1.60 gram/cubic centimeter For Subgrade= 1.75 gram/ cubic centimeter Sub-grade top • Field Dry Density (FDD) For Embankment= min. 95% For Sub grade = min. 97% •Number of test For Embankment = 1set/3000 sq.meter(1set=10pits) For subgrade= 1set/2000 sq.meter (1 set=10 pits) GRANULAR SUB- BASE •Maximum thickness of single compacted layer = 200 mm • Minimum thickness of single compacted layer( only when GSB is laying in two layers) = 150 mm •Max. Allowable size of aggregate =75mm •Number of grading of GSB = 6 •Liquid limit  should not be  more than 25% ( test procedure as per IS 2720 (part 5)). •Plasticity index should  not be more than 6%

Process of laying of DBM/ BC( weather limitations, Rolling of laid material and cleaning of bed)

First of all i want to tell you that DBM act as bituminous base course while BC acts as wearing course. LAYING OF DBM(Dense Bituminous macadam) /BC(Bituminous concrete)  Laying of DBM/BC is done with the help of paver. There are following points which clearly indicates detailed process of laying. To know more about the bituminous concrete (BC) ,please click on below link......... https://gyanofcivilengineering.com/2020/05/bituminous-concrete-bc-specifications.html 1-Weather and seasonal limitations- Laying shall be suspended: A- In presence of standing water on the surface B-When rain is imminent, and during rain, fog, or dust storm C-When the base/binder course is damp D-When the air temperature on the surface on which it is to be laid is less than 10°C for mixes with conventional bitumen and is less than 15°C for mixes with modified bitumen E- When the wind speed at any temperature exceed the 40 km per hour at 2 m height. 2-Cleaning of surface- The

Bituminous Concrete (BC) specifications viz. Layer thickness, Mix and material requirements, grading , laying trials, Rolling , Construction procedure, transport and joint specifications, surface finish and quality control,measurement and rate etc..as per MORTH and Indian Standard

Bituminous concrete(BC)- Bituminous concrete( BC) is used for wearing  course and profile corrective courses.BC is generally laid in single layer on a previously prepared bituminous bound  surface. The thickness of single layer of BC shall be 30mm,40mm and 50mm. 1 -MATERIAL A- Bitumen - The bitumen shall be viscosity graded paving bitumin complying with IS 73 or specified in contract aggrement. The type and grade of bitumen to be used would depend upon the climatic condition and the traffic. Selection criteria of viscosity graded (VG) paving bitumens based on climatic conditions B- Coarse Aggregate It consist of crushed rock,crushed gravel or other hard material retained on 2.36 mm sieve. It shall be clean ,hard,durable and of cubical shape,free from dust,and  soft organic and other deleterious substances. The aggregates  shall satisfy the physical requirements of table  no. -2 (Table no. 500-16 ,as per MORTH 5th revision) where crushed gravel is proposed