RCC Flashcards
stirrups requirement of Column
special confinment zone =At least larger of D, h/6 and 450 mm
Spacing = not more wan D/4. but need
not be less than 75mm nor
mom than 100 mm
spacing in lapping = Spacing of ties in lap length
not more than smaller of
D/2 and 150 mm
beam ductility
maximum bottom r/f = 2.5%
spacing of link in lap joints < 150 mm
for hoop spacing = min(100mm, d/4, )
What is the effect of increasing carbon
content in the steel?
Effect of increasing the carbon content 1n
(a) Decreases the ductility of steel.
(b) Increases the tensile strength of steel.
(c) Increases the hardness of steel.
(d) Decreases the melting point of steel.
(e) Makes steel easier to harden with heat
treatments.
(f) Increases the difficulty of welding of steel.
Mild steel (low carbon steel) contains less than
0.3% carbon. Medium carbon steel contains 0.3
to 0.5% carbon. High carbon steel contains
more than 0.5% carbon. Cast iron contains
more than 2% carbon.
What is ductility? Why is it important?
Ductility can be described as the ability of a
material to undergo large deformations without
rupture before failure. If ductile members are
used to form the structure, the structure can
undergo large deformations before failure. This
is beneficial to the users of the structure as in
case of overloading, if the structure is to collapse, it will undergo large deformations
before failure. This gives a notice to the occupants and provides sufficient time for taking
preventive measures.
If steel is produced in the form of bars, how
will you make it corrosion resistant?
Corrosion prevention of reinforcing bars: The
following methods can be adopted for
prevention of corrosion in reinforcing bars viz.:
(a) Chloride ions in concrete should be limited
to its maximum permissible value which
is 0.15% by mass of cement as per IS:
456.
(b) Corrosion inhibitors like calcium carbonate ‘ aluminium oxide etc. can be added to
concrete which can either be anodic
cathodic or both. ‘
(c) Hot dip galvanizing the reinforcing bars does not affect the bond between concrete and steel but protects the bars from corrosion.
(d) Epoxy coated steel bars show significant resistance to corrosion
Why RCC is used in buildings?
[ESE2006]
RCC in buildings: RCC is predominantly used
in buildings than any other building construction
material. This is because of the fact that RCC
can with stand tensile stresses thereby reducing
the required cross-sectional area of beams,
columns, slabs etc. High rise buildings with
comparatively smaller sections and adequate
ductility is possible only with RCC than any other
construction material.
What is the title of IS 456: 2000?
(ESE2
The title of IS 456: 2000 is “Plain and Reinforced
Concrete- Code of Practice”
What are the different durability criteria givan
in IS 456: 2000?
Mix proportions
(b) Exposure conditions
(c) Shape and size of the aggregates
(d) Material constituents
(e) Freezing and thawing
What do you mean by concrete structure
durability?
The durabil ity of a concrete structure is its abil ity
to serve its intended purposes for a sufficiently
long period of time, or at least during its
expected service life.
However, although a d urable structure is
expected to serve without deterioration to the
extent that major repair is required before expiry
of its design life, it must not be presumed that
durabil ity is a substitution for good maintenance.
Even for a structure that has been designed and
constructed to a high durabil ity standard ,
regular inspection and routine maintenance to
restore the fitness for purpose of the structure
are needed .
What is the maximum strength of concrete?
ESE 2009
The maximum strength of concrete till date is
M80
better to search a good answer on google
What is water reducer? Give examples?
ESE 2009
Water reducer: Many of the admixture reduces
the water requirement of concrete thereby
making it possible to have lower w/c ratio.
These admixture are called as Water Reducers
(a)Lignosulphonic acids and associated salts
(b) Hydroxylated carboxylic acids and assoc1ated salts.
What are the advantages of concrete?
ESE 2009
Advantages of concrete: The following are
some of the advantages of concrete:
(a) Concrete has very high compressive
strength and does not get easily corroded.
(b) Fresh concrete can be handled very easily
and can be moulded into any shaped size.
(c) With steel, concrete can be put in use in
many different structures
(d) Concrete can be spraye on cracks for
repairs etc. by guniting process.
(e) Concrete can be pumped easily and t us
can be laid in difficult locations also.
(f) It is durable and fire resistant
What is the purpose of concrete testing?
ESE 2009
Purpose of concrete testing: Concrete is
tested to assess its quality on certain
parameters like its compressive strength ,
porosity, soundness, workability etc. Defects if
found in concrete testing, then suitable
measures can be adopted thereby ensuring the
safety of the structure.
How much cover is necessary for beams,
columns, slabs and foundation?
(ESE 2009, 2016, 2019)
Cover: The following minimum cover is required for: (a) Beams - 25 mm (b) Slabs -15 mm (c) Columns - 40 mm (d) Foundation-50mm
What are the different tests conducted for flexural design?
Tests for flexural design: As concrete is a
strong material in compression, it can take large
axial and flexural compressive stresses.
However determination of flexural tensile
strength of concrete is important to assess the
load at which cracks may occur. Thus flexural
tensile strength or modulus of rupture test is
conducted on concrete. The modulus of rupture
test is conducted on standard test specimen of
150 mm x 150 mm x 700 mm over a span of
600 mm or 100 mm x 1 00 mm x 500 mm over a
span of 400 mm under symmetrical two point
loading. Modulus of rupture is determined from
the moment at failure as f = M/Z
What do you mean by corrosion in steel in a
concrete columns and beams?
(ESE 2012, 2016)
The chemical or electrochemical reaction etween a material, usually a metal and its en iro ment tha produces a deterioration of the material and its properties is called as ta For steel embedded in concrete COrr�. results in the formation of rust Which �orr�· tour times the volume of the origi n al astwoto none of the good mechanical p Steel Qno oper Corrosion also produces pits and hoi . . f . f . es '" lh. surface 0 retn orctng steel, reduci n g s tr w� capacity as a result of the reduced � sectional area.
What are the various loads acting on floor
and roof?
The various loads acting on a floor are : Self
Weight of the slab itself floor finishes and other
dead loads, live load �tc.
At roofs: The loads acting are the self-weight
of the roof slab, weight of parapet walls, snow
load (if any}, live load etc
What are the differences between LSM and
WSM?
(ESE 2017)
Working Stress Method
• The Stresses in an element is obtained from
the working loads and compared with
permissible stresses.
•
•
•
•
•
The method follows linear stress-strain
behaviour of both the materials.
Modular ratio can be used to determine
allowable stresses.
Material capabilities are under estimat�d
to large extent. Factor of safety are used In
working stress method.
Ultimate load carrying capacity cannot be
predicted accurately.
The main drawback of this method is that
it results in an uneconomical section.
limit State Method
• The stresses are obtained from design
loads and compared with design strengt�.
• In this method, it follows linear strain
relationship but not linear stress
relationship (one of the major difference
between the t wo methods of design).
• The ultimate stresses of materials itself are
used as allowable stresses.
• The material capabilities are not under
estimated as much as they are in working
stress method. Partial safety factors are
used in limit state method.
What are the advantages of preccast
construction?
Since precast is manufact�r�d in a controlled environment 1t 1s eas1er to control the miX,
I d and monitored
quality can be easily controled
much more easily.
Weather is eliminated as a factor u can cast in any weather and get the same
cast m any to perfect mixes
results,
Less labor is required and
can be less skilled.
precast can be installed on site
immediately, there is no waiting or I o
strength and the modularity of
Repeatability-it’s easy to make many copies
of the s ame precast p roduc t; by
maximizing repetition, you can get plenty
of value from a mold and a set-up.
Accelerated curing, by heating the precast
parts, greatly increases strength gain,
reducing the time between casting the part
and putting it into service.
With the ability to so tightly control the
process, from materials to consolidation to
curing, you can get extremely durable
concrete.
What is split tensile strength and how it is
different from conventional tensile strength
of concrete?
(ESE 201 9)
The tensile strength of concrete is about 7 to
15 percent of compressive strength. It is very
d ifficult to perform direct tension test on
concrete specimen as it requires purely axial
force to be applied which is free of any
misalignment and secondary stresses in the
specimen . Thus, indirect tension test is
performed like flexural test or cylinder split test.
IS 581 6: 1 999 specifies the p rocedure of split
tensile strength of concrete. The s pl it tensile
strength of normal density con crete is about 2/
3
rd of modulus of rupture.
What are the different forces that act on a
building situated near the sea?
(ESE 201 9)
Apart from normal loads like dead and live load,
building s ituated near sea is exposed to
following additional forces:
• Wind force
• Tidal force
• Wave force due to sea waves
Why we won’t consider buckl ing c riterion in
cube strength?
( ESE 201 9)
In a cube, the slenderness ratio is near about
3.46 which is close to 3 and for columns with
slenderness ratio about 3 or l ess, crushing is
the failure criterion and thus in cube test,
buckling is not significant.
What is rol ler compacted concrete {RCC)
and how it is d ifferent from ordinary
concrete?
Roller compacted concrete (RCC) is just like
ordinary concrete having the same basic
ingredients viz. cement, water, sand
.
and coar�e
aggregates but it is somewhat dner and st1ff
nough to be compacted by vibratory rollers.
e .
Normally roller compacted concrete requ1res no
form work or finishing and also it does not
contain reinforcing bars. Roller �?m�acted
concrete can be used in the rehab1l 1tat1on of:
In case of slab, what is maximum spacing
of main reinforcement? Why we provide
lateral reinforcement?
In case of slab, m aximum spacing of main
rein orcement is 3d or 300 mm whichever is
less.
La eral reinforcement (in case of columns) is
Pro ided to confine the concrete within the core
and to avoid buckling of main longitudinal bars.
