**P.R.ENGINEERING COLLEGE**

**DEPARTMENT OF CIVIL ENGINEERING**

__Question Bank__**Sub. Code/Name:**CE1351-Design of Reinforced concrete and Masonry structures

**Year/Sem: III / VI**

__UNIT – I__

__RETAINING WALLS__

__PART-A__
1. What is a Retaining wall?

Retaining walls are generally used to
retain earth or such materials to maintain unequal levels on its two faces. The
soil on the back face is at a higher level and is called back fill. Retaining
wall are extensively used in the construction of basements below ground level,
wing walls of bridge and to retain slopes in hilly terrain roads.

2. What are the disadvantages of gravity retaining
walls?

Gravity walls of stone masonry were
generally used in the earlier days to the height of the earth fill. The advent of
reinforced concrete has resulted in thinner retaining walls.

3. What are the types of retaining walls?

Retaining wall can be classified structurally as

1.Cantilever retaining wall

2.Counter fort retaining wall

4. What is a cantilever retaining wall?

The most common and widely used
retaining wall is of cantilever type. Vertical stem resisting earth pressure
one side and the slab bends like a cantilever. The thickness of the vertical slab
is large at the bottom and decreases towards the top in proportion to the
varying soil pressure.

5. What is a counter fort retaining wall?

Counter fort retaining walls are used
for large heights exceeding 5 mts of earth fill. In counterfort retaining wall
the vertical stem is designed as a continuous slab spanning between the
counterforts. Counter forts are designed as cantilever beams from the base
slab.

6. What are the forces acting on a
retaining wall?

Forces acting on a retaining wall are

1.Lateral earth pressure due to the back fill

2.Vertical forces including weight of soil, stem,
heel, toe, and soil fill above the toe.

3.The soil pressure
developed to resist the earth pressure and other vertical forces acting on the heel
and toe.

7. Define Active Earth pressure.

If the soil exerts a push against the
wall by virtue of its tendency to slip laterally and seek its natural slope
(angle of repose) thus making the wall to move slightly away from the back
filled soil mass. This kind of pressure is known as AEP.

8. Define Passive earth pressure.

The pressure or resistance which soil
develops in response to movement of the structure towards it is called the
Passive Earth Pressure.

9
What are the
stability conditions should be checked for the retaining walls?

The stability
of retaining walls should be checked against the following conditions The wall
should be stable against sliding

(a) The wall should be stable against Overturning

(b)
The wall should be stable against
Bearing capacity failure.

10 What is meant by backfill?

The material retained or supported by a retaining wall is
called backfill.

11 What is meant by surcharge?

The position of the backfill lying
above the horizontal plane at the elevation of the top of a wall is called the
surcharge.

12 What
is a gravity retaining wall?

A gravity retaining wall is the one in
which the earth pressure exerted by the backfill is resisted by dead weight of
the wall, which is either made of masonry or mass concrete.

13 What
is meant by submerged backfill?

The sand fill behind the retaining
wall saturated with water is called submerged backfill.

14 What
is the function of counterforts in a retaining wall?

The stem of the counterfort retaining
wall acts as a continuous slab supported on counterforts.The counterforts take
reactions both from the stem as well as the heel slab. Since the active
earthpressure on stem acts outwards, and net pressure heel slab acts downwards,
the counterforts aresubjected to tensile stresses along the outerface of the
counterforts.

15 What is meant by back
anchoring of retaining wall?.

When the height of
retaining wall is much more, it becomes uneconomical to provide counterforts.
In order to reduce the section of stem etc. in the high retaining walls, the
stem may be anchored at its back. The anchor practically takes all the earth
pressure and B.M and S.F. in the stem are greatly reduced.

16 When is the design of shear key
necessary?

When the wall is unsafe in sliding, shear key will have
to be provided

__PART – B__
1. Explain the steps to be followed in proportioning
and design of retaining walls.

2. Design a reinforced concrete cantilever retaining
wall to retain earth level with the top of the wall to a height of 5.5 m above
ground level. The density of soil at site is 17 KN/Cu.mts with a safe bearing
capacity of 120 KN/sq.mts. Assume the angle of shearing resistance of the soil
as 35degrees. Further assume a coefficient of friction between soil and
concrete as 0.55. Adopt M20grade concrete and Fe415 HYSD bars.

3. A Cantilever type retaining wall is
to be designed to support a bank of earth 4m above the ground level on the toe
side of the wall. The backfill surface is inclined at an angle of 15 degrees with
the horizontal. Assume that good soil is available for foundations at a depth
of 1.25m below the ground level with a safe bearing capacity of 160KN/m and an
angle of shearing resistance of 30degrees .Assume co-efficient of friction
between soil and concrete as 0.5,Adopt M-20 grade concrete and Fe-415 HYSD
reinforcement. Assume the unit weight of soil as 16kN/m

^{3}
.4. Design a counter fort type retaining
wall to support an earth fill of 7.5m above ground level. The foundation depth
may be taken as 1.5m below the ground level. The safe bearing capacity of soil
at site is 150KN/m

^{2}. .Unit weight of soil may be taken as 16KN/m^{3}and an angle of shearing resistance of 30 degrees. Assume the value of coefficient of friction as .55.Adopt M-20 grade concrete and Fe-415 HYSD bars. Sketch the details of reinforcements in the retaining wall.- Design a cantilever retaining wall
to retain earth with a backfill sloped 20 degrees to the horizontal. The
top of the wall is 5.5m above the ground level. Assume the depth of
foundation as 1.2 m below the ground level with a safe bearing capacity of
capacity of 120Kn/m
^{3}.The unit weight of backfill is18KN/m^{3}and an angle of shearing resistance of 35 degrees .Also assume the coefficient of friction between soil and concrete as 0.55.Adopt M-20 grade concrete and Fe-415HYSD steel bars.

__UNIT – II__

__WATER TANKS__

__PART-A__
1. Mention the grade of concrete which
is used in the construction of water tank.

Richer concrete mix of grades M20 to
M30 are commonly used in the construction of water tanks. High quality
concrete, in addition to providing water tightness, also has higher resistance
to tensile stresses developed in the tank walls.

2. Mention
the three factors that must be considered while designing a RCC tank.

i. Strength ii. Water tightness iii. Overall stability

3. Water are the types of reinforced concrete water
tanks?

i.Tanks resting
on ground ii.underground
tanks iii.elevated water tanks.

4. Mention
the reinforcement details that should be provided in a water tanks.

Minimum area of steel is 0.3 percent of
gross area of section upto 100mm thick, reduced to 0.2 percent in section up to
450mm thick. For sections above 225mm thick, provide two layers of reinforcement. The percentage of reinforcement
in base or floor slab resisting directly on ground must be not less than 0.15%
of the concrete section. The minimum cover to all reinforcement should be not
less than 25mm or the diameter of the bar whichever is greater.

5. Define the term: Dome:

A Dome is
defined as a thin shell generated by the revolution of a regular curve about one
of its axes.

6. Define the following terms:

i. Latitude:

The circle of
each ring in a dome is called Latitude.

ii. Meridian circle:

The circle drawn through two
diametrically opposite points on a horizontal diameter and the crown is known
as meridian circle.

7. Define the following terms:

i. Radial:

The joint
between successive horizontal rings is called radial.

ii. Meridian thrust:

The reaction between the rings is
tangential to the curved surface giving rise to compression along the medians.
The compressive stress is called meridional thrust or meridional compression.

8. Mention the thickness and steel requirement of
dome.

A minimum thickness of 7.5cm is
provided to protect steel. Minimum steel requirementis 0.15% for mild steel
bars and 0.12% for HYSD bars of the sectional area in each direction meridionally
as well as along the latitudes.

9. What are the three types of joints in water tank?

i. Movement
joints

a. Contraction

b. Expansion

c. Sliding

ii.
Construction joints

iii. Temporary
open joints

10. What
is the foundation specification for small capacity tanks?

For small capacity tanks individual
footings for columns can be provided. Infact, the type of footing will depend
upon the nature of soil and type of staging. In case of low lying areas
of low safe bearing capacity with high ground water table, pile footings
are provided. In any case of foundation slab, lean mix of 1:4:8, 150mm thick
may be provided as levelling course.

11. What
are the methods available for the analysis of circular tank?

i. IS code
method ii. Reissner’s method iii. Carpenter’s method iv. Approximate method

12. What are movement joints in water
tanks?

These joints require the incorporation
of special materials in order to maintain water-tightness while accommodating
relative movement between the side of the joints. All movement joints are
essentially flexible joints.

13. What is contraction joint in water
tanks?

A contraction
joint is a typical movement joint which accommodates the contraction
of the concrete.

14. What is meant by expansion joint in
water tanks?

It is a movement joint with complete
discontinuity in both reinforcement and concrete, and is intended to
accommodate either expansion or contraction of the structure.

15. What
are underground water tanks?

Underground water tanks are used for
storage of water received from water supply mains operating at low pressures,
or received from other source.

16. What are conditions under which the
walls of underground water tanks designed?

(a) Tank full with water, with no earthfill outside.

(b) Tank empty, with full earth pressure due to saturated earthfill.

17. What are the four components of design
of underground water tanks?

(i)
Design of long
walls

(ii)
Design of short
walls

(iii)
Design of roof
slab

(iv)
Design of base
slab

18 What are two methods of analysis of
rectangular tanks?

(i)
Approximate
analysis

(ii)
Exact analysis
based on elastic theory

19 Where are domes used?

(i) Roof of
circular areas

(ii) Circular
tanks

(iii) Hangers

(iv) Exhibition
halls, auditoriums and planitoriums and

(v) Bottoms of tanks, bins and bunkers

__PART-B__
1. An open rectangular tank 4m x 6m x 3m deep rests
on firm ground. Design the tank. Use M20mix.

2. Design a circular tank with flexible base for
capacity of 400000 liters. The depth of water is to be4m, including a free
board of 200mm.Use M20 concrete.

3. Design an underground water tank 4m x 10m x 3m
deep. The sub soil consist of sand having angle of repose of 30 degree and
saturated unit weight of 17KN/m3.The
water table is likely to rise up to ground level. Use M20 concrete and HYSD
bars. Take unit weight of water as9.81KN/m3

4. Design the side wall of a circular tank of
capacity1.5 lakh litres of water. The depth of the tank is limited to 2.5m. The
joint between the wall and base as flexible. The base slab rest on the ground.
Use M 20 grade concrete.

5. Design a spherical dome over a circular beam for
the following data

a. Inside diameter of room = 12m

b. Rise
of dome = 4m

c. Live
load due to wind, snow,etc = 1.5 KN/m2

The dome has an opening of 1.6m
diameter at its crown. A lantern is provided at its top, which causes a dead
load of 22KN acting along the circumference of the opening. Use M20 concrete and
Fe415 steel.

6. Design a conical dome roof for a
room with base diameter as 12m. The live load due to wind, snow, etc may be
taken as 1000N/mm2.The
height of the roof is 4m.

__UNIT – III__

__SELECTED TOPICS__

__PART-A__
1. What
is a stair case?

A staircase consists of a number of
steps arranged in a series, with landings at appropriate locations, for the purposes
of giving access to different floors of a building.

2. Define
tread:

Tread:

The horizontal portion of a step was
the foot rests is referred to, as tread.250 to 300 mmis the typical dimensions
of a tread.

3. Define
Riser

Riser is the vertical distance between
the adjacent treads or the vertical projection of the step with value of 150 to
190 mm depending upon the type of building.

4. Define
Going:

Going is the
horizontal projection of an inclined flight of steps between the first and last
riser.

5. What are the types of staircases?

They are
broadly classified as

i.Straight
stair

iiQuarter
turn stair

iii.Half turn
stair

iv.Dog
legged stair

v.Open
newer stair with quarter space landing

vi.Geometrical
stairs such as circular stair, spiral stair, etc.

6. What
is a flight?

A flight is the length of the staircase
situated between two landings. The number of steps in a flight may vary between
3 to 12.

7. What
is the minimum rise and tread in residential buildings?

In residential
buildings, the rise may vary between 150mm to 180mm tread between200mm to
250mm.

8. What
is the minimum rise and tread in public buildings?

In public
buildings, the rise may vary between 120mm to 150mm tread between200mm to
300mm.

9. Mention
the places where the following staircase
can be used

Ã˜ Single flight staircase is used in
cellars or attics where the height between floors is small and the frequency of
its use is less.

Ã˜ Quarter turn staircase flight generally
runs adjoining the walls and provides uninterrupted space at the centre of the
room. Generally used in domestic houses where floor heights are limited to 3m.

Ã˜ Dog legged staircase is generally
adopted in economical utilization of available space.

Ã˜ Open well staircases are provided in
public buildings where large spaces are available.

Ã˜ In congested locations, where space
availability is small, Spiral stairs are provided.

10. Define
flat slab.

A flat slab is a typical type of
construction in which a reinforced slab is built monolithically with the
supporting columns and is reinforced in two or more directions, without any
provision of beams.

11. What
are all the components of flat slab?

i.Drop
of flat slab

ii.Capital
or column head

iii.Panel

12. Define
drop of flat slab.

Drop is that
part of the slab around the column, which is of greater thickness than the rest
of the slab.

13. Define
capital or column head.

Sometimes the diameter of a supporting
column is increased below the slab. This part of column with increased diameter
is called column head.

14. Define
panel of flat slab.

It is the area enclosed between the
centre lines connecting adjacent columns in two direction sand the outline of
the column heads.

15. Write
the different types of flat slabs?

i.Slabs without drops and column heads

ii.Slabs
without drops

iii.Slab with
drops and column with column head

16. What
are the methods of analysis of flat slab?

(i) The direct
design method (ii) The
equivalent frame method

17. What
are all the assumptions made in equivalent frame method?

i. The structure is considered to be made of
equivalent frames longitudinally and transversely.

ii. Each frame is analysed by any established method
like moment distribution method.

Iii The
relative stiffness is computed by assuming gross cross section of the concrete alone
in the calculation of the moment of inertia.

iv. Any variation of moment of inertia along the axis
of the slab on account of provision of drops should be considered.

18. What
are all the assumptions made in direct design method?

(i) There shall
be minimum of three continuous spans in each direction.

(ii) The panel shall be rectangular,
and the ratio of the longer span to the shorter span within a panel shall not
be greater than 2.0.

19. Explain
about box culvert shortly.

A box culvert is continuous rigid frame
of rectangular section in which the abutment and the top and bottom slabs are
cast monolithic. A box culvert is used where a small drain crosses a high embankment
of a road or a railway or a canal- specially when bearing capacity of soil is
low.

20. Give
the names of various types of bridges.

i.Solid
slab bridge or deck slab bridge.

ii.Deck
girder bridge or T-beam bridge.

iii.Balanced
cantilever bridge

.iv.Rigid frame culvert.

v.Arch
bridge.

vi.Bowstring
grider bridge.

vii.Continuous
girder or arch bridge.

__PART - B__
1 Design one of the flights of
stairs of a school building spanning between landing beams to suit the following
data.

i. Type of staircase : waist slab type

ii. Number of steps = 12

iii.
Tread T =300mm

iv.
Riser R =160mm

v.
Width of
landing beams = 400mm

vi.
Materials: M-20
concrete and Fe-415 HYSD bars.

2. Design a dog-legged stair for a
building in which the vertical distance between floors is 3.6m.Thestair hall
measures 2.5m x 5m.The live load may be taken as 2500N/mm2.Use M20 concrete, and
HYSD bars.

3. Design the interior panel of a flat
slab 5.6m x 6.6m in size, for a super imposed load of 7.75kN/m2.Provide two-way
reinforcement. Use M20 concrete and Fe 415 steel.

4. Design the interior panel of a flat
slab for a warehouse to suit the following data:

i.
Size of
warehouse 24m x 24m divided into panels of 6m x 6m.

ii.
Loading
class-5kN/m2

iii.
Materials: M-20
Grade concrete and Fe-415 grade HYSD bars.

5. Design a box culvert having inside
dimensions 3.5m x 3.5m.The box culvert is subjected to a superimposed dead load
of 12000N/m2 and
a live load of 45000N/m2 from the
top. Assume unit weight of soil as 18000N/m3 and angle of repose of 30degree.Use M20 concrete and Fe415 steel.

6. Design a solid slab bridge for
class A loading for the following data.

Clear span = 4.5m

Clear width of road ways = 7m

Average thickness of
wearing coat = 80mm

Use M20 mix. Take unit weight of concrete as 24000N/m3

__UNIT – IV__

__YIELD LINE THEORY__

__PART-A__
1. What
is meant by yield lines?

The failure of reinforced concrete slabs
of different shapes such as square, rectangular,circular with different types
of edge conditions is preceded by a characteristic pattern of cracks,which are
generally referred to as yield lines.

2. What are the characteristic features of yield
lines?

i.Yield lines end at the supporting edges of the
slab

ii.Yield lines are straight

iii.A yield line or yield line produced
passes through the intersection of the axes of rotation of adjacent slab
elements.

iv.Axes of rotation
generally lie along lines of supports and pass over any columns.

3. State the principle of virtual work.

If a deformable structure in
equilibrium under the action of a system of external forces is subjected to a
virtual deformation compatible with its condition of support, the work done by
these forces on the displacements associated with the virtual deformation is
equal to the work done by the internal stresses on the strains associated with
this deformation.

4. What are the two methods of determining the
ultimate load capacity of reinforced concrete slabs?

(i) Virtual
work method (ii) Equilibrium
method

5. What is the direction of yield line in one way
slab?

In one way slab, the direction of yield line is
perpendicular to the direction of steel.

6. What is the direction of yield line in two way
slab?

In two way slab, the direction of yield line is not
perpendicular to the direction of steel.

7. What is the concept of yield line method?

In the yield line method, the
computation of ultimate load is based on the pattern of yieldlines that are
developed in the slabs under conditions approaching collapse.

8. Who innovated yield line theory?

This method was innovated by Ingerslav (1923) and was
greatly extended and advanced by Johanssen

9. What is an yield line?

A yield line is defined as a line in
the plane of the slab across which reinforcing bars have yielded and about
which excessive deformation under constant limit moment continues to yield leading
to failure.

10. What is meant by an orthotropically reinforced
slab?

If the
reinforcement in the two directions is not the same, it is said to be
orthotropically reinforced slab.

11 What is meant by an isotropically
reinforced slab?

The ultimate
moment of resistance in an isotropically reinforced slab, in any direction, is the
same.

12 Define static indeterminacy of a
structure.

If the conditions of statics i.e.,Î£H=0,Î£V=0 and Î£M=0
alone are not sufficient to find either external reactions or internal forces
in a structure, the structure is called a statically indeterminate structure.

13.
Define:
Unit load method.

The external load is
removed and the unit load is applied at the point, where the deflection or rotation
is to found.

14 What is the absolute maximum bending
moment due to a moving udl longer than the span of a simply supported beam?

When a simply supported beam is
subjected to a moving udl longer than the span, the absolute maximum bending moment occurs when
the whole span is loaded .Mmax max =
wl / 8

15. State the location of maximum shear
force in a simple beam with any kind of loading.

In a simple beam with any kind of load,
the maximum positive shear force occurs at the left hand support and maximum
negative shear force occurs at right hand support.

16. What is meant by maximum shear force
diagram?

Due to a given system of rolling loads
the maximum shear force for every section of the girder can be worked out by
placing the loads in appropriate positions. When these are plotted for all the sections
of the girder, the diagram that we obtain is the maximum shear force diagram. This
diagram yields the ‘design shear’ for each cross section.

17. What do you understand by the term
reversal of stresses?

In certain long trusses the web members
can develop either tension or compression depending upon the position of live
loads. This tendency to change the nature of stresses is called reversal of
stresses

18. What is the moment at a hinged end of a
simple beam?

Moment at the hinged ends of a simple
beam is zero.

19. Define similitude.

Similitude means similarity between two
objects namely the model and the prototype with regard to their physical
characteristics:

•Geometric similitude is similarity of form

•Kinematic similitude is
similarity of motion Dynamic and/or mechanical similitude is similarity of masses and/or forces

20. Define
: Trussed Beam.

A beam strengthened by providing ties and
struts is known as Trussed Beams.

__PART - B__
1 A reinforced concrete square slab, 3.5m X 3.5m is simply
supported at the ends and is reinforced with 8mm diameter bars spaced at 150mm
centres both ways. Determine the safe service live load if the average effective depth of slab
is 100 mm and the total thickness of
slab, inclusive of flooring, is 160mm. Use M20 concrete and Fe 415 HYSD bars

2 A rectangular slab 4m X 5m is
simply supported at the ends.Design the slab to carry super – imposed service
load of 5 kN / m2, if the slab is to be
isotropically reinforced Use M20 concrete and
Fe 415 HYSD bars

3 A triangular slab has equal side
lengths of 4.5m is supported on two
edges and is isotropically reinforced with 8mm dia. bars of Fe 415 grade, spaced at 125mm centres both
ways. Determine (i) Ultimate moment
capacity (ii) ultimate collapse load. The total thickness
of slab may be assumed as 120mm in M20
grade concrete.

4 Design a circular slab of
5m dia, simply supported along
the edge,to carry a service live load of
5 kN / m2. Use M20 concrete and
Fe 415 HYSD bars

__UNIT – V__

__BRICK MASONRY__

__PART-A__
1. What is cross sectional area of Masonry unit?

Net cross sectional area of a masonry
unit shall be taken as the gross cross sectional area minus the area of
cellular space. Gross cross sectional area of cored units shall be determined
to the outside of the coring but cross sectional area of groves shall not
be deducted from the gross cross sectional area to obtain the net cross sectional
area.

2. What is bond in a brick masonry?

Arrangements of masonry units in
successive courses to tie the masonry together both longitudinally and transversly; the arrangement
is usually worked out to ensure that no vertical joint of one course is
exactly over the one in the next course above or below it, and there is maximum
possible amount of lap.

3. How will you calculating effective
length, effective height and effective thickness?

The height of a wall to be column to be
considered slenderness ratio. The length of a wall to be column to be
considered slenderness ratio. The thickness of a wall or column to be
considered for calculating slenderness ratio.

4. What meant by lateral support?

A support which enables a masonry
element to resist lateral and/or restrains lateral deflection of a masonry
element at the point of support.

5. What is the slenderness ratio for walls?

For a wall, Slenderness ration shall be
effective height divided by effective thickness or effective length divided by
the effective thickness is less.

6. What is the slenderness ratio for walls and
columns?

For column slenderness ration shall be
taken to be the greater of the ratios of effective heights to the respective
effective thickness in the two principal directions. Slenderness ratio for a
load-bearing column shall not exceed 12

7 What is slenderness ratio in brick
masonry structures?

In brick masonry structures, For a wall
slenderness ratio shall be the effective height divided by the effective
thickness or effective length divided by the effective thickness which ever is
less.

8 What is slenderness ratio in brick column masonry
structures?

For a column slenderness ratio shall be
taken to be the greater of the ratios of effective height s to the respective
effective thickness in the two principal directions. Slenderness ratio
of a load-bearing column shall not exceed 12.

9. What is reinforced brick work?

Reinforced brickwork is a typical type
of construction in which the compressive strength of bricks is utilized to bear
the compressive stress and steel bars are used to bear the tensile stresses in
the slab.

10. What is the thickness adopted for reinforced brick
slab?

The thickness of slab may be kept as
100mm to 200mm.

__PART- B__
1. Explain the factors to be considered while
designing brick masonry with respect to stability and lateral supports on the
structure.

2. What are the factors to be considered while
determining the effective height of wall and column sand effective length of
walls?

3. Explain the design procedure to design axially and
eccentrically loaded brick walls

4. Design an interior panel of a flat slab, 5.5mx5.5m
for a live load of 5000 N/m2. Use M20 grade concrete and Fe415 grade
steel.

5. Derive from principles the ultimate design moments
for a rectangular simply supported slab panel using yield line approach.

6. A square interior panel of an intermediate floor
is of effective dimension 5mx5m. The live load on the floor is 2.5 kN/m2. Finishes is 1 kN/m2.. Analyse the slab using yield line approach and design
the slab. Use M20 concrete and Fe415
steel.

7. Design a solid square masonry column of height
2000mm, to carry an axial load of 150KN. The column is tied at the top and bottom.
Include the self weight of the column for the design.

8. Design a solid wall of a single storey mill
building that is 3000m in height, securely tied with roof and floor units and
supporting two beams on either side of it that exerts reactions of 30KNand
20KN. The thickness of the wall is 230mm. The beam bears on the wall is 115mm.
Assume uniform bearing stress. Neglect the load due to self-weight