- DEFINITIONS*
1)PCC:
• plastic mass,
• have a low tensile strength
Ø • Use where the compressive force is more
2)RCC:
• for increasing the tensile strength of concrete.
• Steel prevents temperature and shrinkage stresses .rcc composite material.
• Thermal expansion is the same in concrete and steel.
ADVANTAGES:
• Strength-tensile and compression
• Durability-up to 100 years
• Moldability- easily moldable
• Economy-cheaper than steel and prestressed concrete, maintenance cost is low
• Transportation-easily available material, RMC is used ready mix concrete factory made
• Fire resistance is more
• Permeability: impermeable(अà¤ेद्य) to moisture
• Seismic resistance: extremely resist
DISADVANTAGES:
• Heavy structure
• Lots of Shuttering, centering, and formwork, require skilled labor
• Require time to gain full strength
• Can't use it immediately like steel structure
APPLICATION OF RCC :
- Residential and commercial structure.
- Earth retaining structure example: abutments for bridges and retaining walls for earthen embankments.
- Big conference hall, aircraft hanger,r.c.c shells,r.c.c folded plates for an industrial structure where the large column-free structure is required
- Marine structures like wharves, quay walls, watchtowers, and lighthouse
- R.c.c poles for power transmission
- Pavement for highway and airport runways
- Atomic structure due to superior radiation
- The foundation of any structure
RCC SYSTEM:
- Structural (beam-column, slab)
- Non-structural (partitions, false ceiling)
- One-dimensional (beam, column, arches)
- Two dimensional system(slab ,plates, shell)
- Three-dimensional ( thick pipes, domes, walls of nuclear reactor vessel)
RCC SYSTEM IN BUILDING:
- way slab system: slab subjected to maximum flexure at the center of span maximum shear at support under gravity load
- Two-way floor system: all edges supported on a column and subjected to flexure in 2 direction
Figure from n krishna raju book
- Beam and slab floor system: typical floor and beam system used in general residential buildings and commercial building
Figure from n krishna raju book
- Flat slab floor system: slab is supported on a column directly without a beam preferred for large span offices, and garages, where headroom is less
The figure is from n Krishna Raju sir's book
- Grid floor system: in this floor, the system beam is spaced at the close interval in a perpendicular direction and support a thin slab, used in large space office for column-free spaced
The figure is from n krishna raju sir's book
- Multistory vertical frame system: column, beam, and slab forming a 3d structure.
The figure is from n Krishna Raju sir's book
- Shear wall system: consists of a solid wall covering the overall height of the building located at lift or staircase regions situated also as an exterior wall for controlling excessive deflection of building, its also called core in a tall building.
The figure is from n Krishna Raju sir's book
3)MATERIAL USED IN R.C.C
3a)CONCRETE: made-up of cement aggregate water
1) Necessity for good concrete?
• Homogenous mix
• Compaction
• Sufficient Curing
• Good water-cement ratio considering strength and workability
• All increased in the right proportion
• Water free from organic substances
• Cement should be of good quality and measured by weight, not by volume
2) Grade of concrete:
• m10 to m 80 sometimes up to 100
• M10 = Where m stands for 'mix' and 10 is characteristic compressive strength n/mm^2
• R.C.C WORK-not less than m20
• For post-tension work -m35 and above
• For post-tension prestressed -m40 and above
3) Property of concrete:
A)compressive strength: characteristic compressive strength is the strength below which only 5 percent of tests are expected to fail. denoted by fck and concrete mix should be designed for target strength
Target strength = characteristic strength (at 28 days)+ 1.656 *standard deviation
B)tensile strength: flexure strength of concrete is generally referred to as tensile strength denoted by far
Fcr=0.7sqrt fck
C)Modulus of elasticity: it depends upon the size of aggregates and mix proportion, types of cement but generally in the absence of data it is calculated by the empirical formula
Ec=5000sqrt Fck
D) shrinkage of concrete: environment condition and humidity influence the shrinkage of concrete and water content affect shrinkage
Total shrinkage strain =.003 (in the absence of data)
Shrinkage influences the deflection of concrete member
Ø E) creep of concrete: in elastic time-dependent strain developed in concrete under sustain loading
Cement content, water cement ratio, aggregates cement ratio, temperature, humidity, size of the structural element, type of loading, and period of loading influence the creep of concrete.
Due to lack of data creep is calculated as =ultimate creep strain /elastic strain
According to is 456:2000
Age of loading: 7 days 28days 1 year
creep coefficient: 2.2 1.6 1.1
Creep is directly proportional to the deflection
The above coefficient is very useful for calculating the time-dependent deflection of concrete members
Ø F) Coefficient of thermal expansion:
it is mainly influenced by the type of aggregates used in the structure IS456 Table 24
3b)cement:
• OPC is generally used in construction
• Compressive strength of cement based on cement-sand cubes
• this cube face area is 50 cm^2
• Cube made up of 1 part cement and 3 part sand by weight not by volume because volume changes with the environment
50kg cement volume -34.7 liter
• Three types of grade define cement 33,43,53
• Max cement content for R.C.C=450KG /M^3
3c) reinforcing material:
1)Why we provide -
• it takes all the tensile stresses developed in the structure
• Increase the strength of concrete
• Prevent crakes due to creep and shrinkage
• Make the section thinner compare to plain cement concrete
2)Checkpoints for steel:
• Provide perfect bond to transfer stresses from concrete to steel
• Should be cheap, easily available, durable
• Coefficient of thermal expansion should be nearly the same as concrete
• Should be workable easy to cut join
• Should not react to other increases in RCC
3) WHY STEEL?
ADVANTAGES:
• Strong enough to take tension, compression, torsion, shear
• Provide good bond for concrete
• Ductile behavior-more the ductility more the elongation of steel before failure,, gives warning t time before failure
• Longer life, easily available
DISADVANTAGES:
• Rusting- because of porous concrete or not providing proper cover
• Loses strength at high temperature
4)TYPES OF STEEL BAR:
A) Mild steel plain bar-
a) cold work mild steel bar(Fe250)
{IS432:1966 part 1}
b) hot rolled mild steel bar
{IS1139:1966 part 2}
B)High yield strength deformed bar
a) cold work deformed bar
Fe415{IS1786:1979}
Fe500 {IS1786:1979}
b) hot rolled deformed bar
{IS1139:1966 part 2}
C) other 1
Hard-drawn steel wire fabric
Wire mesh {IS 1566:1967}
D)Other 2
Rolled steel member
Angel, channel section, T section joist { IS 222:1975}
E) other 3
a) Thermo mechanically treated bars (TMT)
b) corrosion resistance steel(CRS)
KEY POINTS OF BAR
# MILD STEEL bar(Fe250):
• Yield strength=250 n/mm^2
• More ductile than deformed bar
• But have low strength and weak bond
# HIGH YIELD STRENGTH DEFORMED Bar(Fe450,500):
• Higher percentage of carbon than mild steel
• Strength is higher than mild steel
• Hot rolled hysd , cold worked hysd also called CDT(cold twisted deformed)
• CDT has higher strength about 50 %more yield strength compare to plain bar
• yield stress of the deformed bar is at .002 strain value in the strain stress curve also called 0.2 percent proof stress
#TMT(THERMOMECHANICALLY TREATED BAR)
• Outer surface is harder than hysd
• SAIL(steel authority of India);RINL(Rashtriya Ispat Nigam Limited produces TMT in India
ADVANTAGES :
• High strength
• Better ductility
• Superior corrosion resistance
#CRS(CORROSION RESISTANCE STEEL BAR):
• Latest developments
• Carbon content 0.18% less than hysd
• Corrosion resistance content chromium is 1.5 %
• SAIL(steel authority of India);TISCO(Tata iron and steel company )produces TMT in India
#WIRE FABRIC:
• Made up of welding or weaving steel in the form of mesh
• Used in road pavement
5) WHY HYSD IS PREFERRED FOR R.C.C?
• High strength
• Better bond- 60%beter than mild steel
• Economy- cost is same as mild steel but in overall structure, hysd is economic because of the strength amount of steel used in the structure is reduced which gives economy to structure
Grade 0.2 % proof stress or
Yield stress or
Characteristic strength
In n/mm^2
FE -250 250 n/mm^2
FE-415 415 n/mm^2
FE-500 500n /mm^2
FE-550 550 n/mm^2
TMT or CRS (Fe-500) 500n/mm^2
Wire fabric 480n/mm^2
Types of loads on the structure
Structures are designed to sustain the load given below
1) DEAD LOAD:
• Permanent load
• Self-weight
• Depends on unit weight of material(for concrete =25kn/m^3
• Examples:-floor finish ,self weight of element used in structure(beam ,column, slab),wall load
• Is875 part 1
2) LIVE LOAD:-
• Load changes from time to time
• Examples -loads of people, Machine, furniture
• Called imposed load
• Is875 part 2
3) WIND LOAD:-
• Depends upon the velocity of wind, shape of the structure, size of the structure
• Is 875 part 3
4) SNOWLOAD:-
• Is875 part 4
5) EARTHQUAKE LOAD:-
• Depends upon the location of the building
• Is1893:2016 latest code
• India has 4 seismic zones
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