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Wednesday, 31 January 2018

Analysis And Design Of A Multi Storied Residential Building Of (Ung-2+G+10) By Using Most Economical Column Method By Dr P V Surya Prakash

Abstract
Hyderabad is the fifth largest city in our country. As it is rapidly developing in the field of
construction in the city is very costly. The design process of structural planning and design requires
not only imaginations and conceptual thinking but also a sound full knowledge on how a structural
engineer can economies the structure besides the knowledge of practical aspects, such as recent
design codes, bye laws, experience, intuition and judgment. The main purpose of the project is to
ensure and enhance the safety, keeping careful balance between economy and safety (i.e. Most
economical column method). The present project deals with the analysis and design of a multi storied residential building of (ung-2+g+10) by using most economical column method. The dead load &live loads are applied and the design for beams, columns, footing is obtained etabs with its new features surpassed its predecessors, and compotators with its data sharing.our main aim is to complete a multi-storey
building is to ensure that the structure is safe and economical against all possible loading conditions
and to fulfill the function for which they have built.safety requirements must be so that the
structure is able to serve it purpose with the maintain cost.detailed planning of the structure
usually comes from several studies made by town planners, investors, users, architects and other
engineers .on that, and a structural engineer has the main influence on the overall structural design and an architect is involved in aesthetic details.for the design of the structure, the dead load, live load,
seismic and wind load are considered. The analysis and design for the structure done by using a
software package etabs.in this project multistoried construction, we have adopted limit state method of analysis and design the structure. The design is in confirmation with is 456-2000.the analysis of frame is worked out by using etabs

1. Statement Of The Project:
Salient Features: The design data shall be as
follows.
1. Utility of Buildings: Residential Building
2. No of Storey: (UNG-2 +G+10)
3. Shape of the Building: Rectangular
4. No. Of Staircases: ONE
5. No. Of Lifts: One
6. Types of Walls: Brick Wall
7. Geometric Details
a) Ground Floor (G-2, G-1): 3.2 M
b) Floor-To-Floor Height: 3.0 M
c) Height of Plinth: 0.6 M above G.L
d) Depth of Foundation: 2 M below G.L
8. Material Details
a) Concrete Grade: M30, M25 (COLUMNS
AND BEAMS)
b) All Steel Grades:
HYSDREINFORCEMENT of Grade
Fe415
c) Bearing Capacity of Soil: 200 KN/M2

9. Type Of Construction: R.C.C FRAMED
structure
GENERAL PRINCIPLES OF SITE SELECTION:
Site selection has an important bearing on planning and designing of buildings. Generally,
therefore an architect has either to make a choice of suitable site or to plan his building structure to suit the available site. Natural defects of a site will involve considerable expenditure on construction
and maintenance of the building.
1. A site which comes within the limits of an areawhere the by-laws of the local authority enforce
restrictions regarding proportions of plots to built up, vacant spaces to be left in front and
sides, heights of buildings etc. should be preferred.
2. The site should be situated on an elevated place and also leveled on with uniform slopes from
one end to the other so as to provide good and quick drainage of rain water.
3. The soil surface of the site should be good enough to provide economical foundations for
the intended building without causing any problem. Generally for most satisfactory
instructions, the site should have rock, sand or firm soil below 60 to 120cm. layer of light or
even black cotton soil.
4. The situation of the site should be such as to ensure unobstructed natural light and air.
5. 5. The site should have a good land scope but away from quarries, kilns, factories etc.

 TYPES OF LOADS:
Loads are primary consideration in any buildings design because they define the nature and
magnitude of hazards or external forces that a building must resist to provide reasonable
performance (i.e.; safety and serviceability) throughout the structure’s useful life.The
anticipated loads are influenced by a building’s intended use (occupancy and function),
configuration (shape and size) and location (climate and site conditions). Ultimately, the type and
magnitude of the design loads affect critical decisions such has the Material selection,
construction details, and architectural configuration.
Thus to optimize the value (i.e. performance versus economy) of the finished product, it is
essential to apply design loads realistically. While the building consider in this guide are primary
single-family detached and attached dwellings, the principles and concepts related to building loads
also apply to other similar types of construction, such as low-rise apartment’s buildings. In general, the design loads recommended in this
guide are based on:

1. Dead load
2. Live load
3. Imposed loads
4. Wind loads
5. Earth Quake load

DEAD LOADS:
This is the permanent of the stationary load like self-weight of the structural elements.
This include the following
a) Self-weight
b) Weight of the finished structure part.
c) Weight of partition walls etc.
Dead loads are based upon the unit weights of elements, which are established taking in
account materials specified for construction, given IS 1911-1967
Dead loads consists of the permanent construction material loads compressing the roof,
floor, wall, and foundation system, including claddings finishes and fixed equipment. Dead load
is the total load of all of the components of the building that generally do not change over time,
such as the steel columns, concrete floors, bricks, roofing material etc.

LIVE LOADS:
These loads are not permanent or moving loads. The following loads includes in this type of
loading: imposed loads(fixed) weight of the fixed seating in auditoriums, fixed machinery, partition
walls these loads through fixed in positions cannot be relieved upon to act permanently throughout the life of the structure. Imposed loads (not fixed) these loads change either in magnitude or position very often such as the traffic loads, weight of the furniture etc. Live loads are produced by the use
occupancy of the building. Loads include those from human occupants, furnishings, no fixed
equipment, storage, and constriction and maintenance activities. As required to adequately
define the loading condition, loads are presented in terms of uniform are loads, concentrated loads, and uniform line loads

LOADING STANDARDS:
The loads that are considered in the
design are based on IS-875-1964.
1. The Dead Loads:
RCC
25kN/m3
PCC 24
kN/m3
Brick masonry 19
kN/m3
Floor finishes 1
kN/m3
2. The Live Loads:
On floors 4 kN/m2
On roofs 3.5 kN/m2
On stairs 5 kN/m2

 IMPOSED LOADS:
Loads produced by intended use occupancy of a building including the weight
movable portions distributed concentrated loads and loads that vibration and impact called imposed
loads estimated by IS 456-2000.

WIND LOADS:
The effects of wind on structures are still not perfectly understood and our knowledge in
this area is constantly improving with the periodic revisions of the applicable wind code provisions.
High winds can cause four types of structural damages which are stated as
1. Collapse
2. Partial collapse
3. Over damage
4. Sliding
Often partial damage occurs most frequently. Wind forces are applied perpendicular to all roofs and
walls and both internal and external wind pressures are considered. Wind is not constant with height or with time, is not uniform over the side of the structure and does not always cause positive
pressure. Both the wind pressure and the wind suction must be taken into account during the
structural analysis.


EARTH QUAKE LOAD:
Seismic motions consist of horizontal and vertical ground motions, with the vertical
motion usually having a much smaller magnitude. The factor of safety provided against gravity loads
usually can accommodate additional forces due to vertical acceleration due to earthquakes. So, the
horizontal motion of the ground causes the most significant effect on the structure by shaking the
foundation back and forth.
However in practice all structures are flexible to some degree but a very flexible structure will be
subjected to a much longer force under repetitive ground motion. This shows the magnitude of the
lateral force on a structure is not only dependent on the acceleration of the ground but it will also
depend on the type of structure (F=Ma). The earthquake load is estimated by response spectrum
method in the project and is as specified by the provisions in IS 1893.

Seismic load can be calculated taking the view of acceleration response of the ground to the super
structure. According to the severity of earthquake intensity they are divided into 4 zones.
1. Zone I and II are combined as zone
II.
3. Zone III.
3. Zone IV.
4. Zone V.

LOAD COMBINTION:
1. For seismic load analysis of a building the code
refers following load combination.
1. 1.5(DL + IL)
2. 1.2(DL + IL ± EL)
3. 1.5(DL ± EL)
4. 0.9 DL ± 1.5 EL
2. For wind load analysis of a building the code
refers following load combination.
1. DL +LL
2. DL+WL
3. DL+0.8LL+0.8WL
Both WL and EL are applied in X and Z direction.
These loads are also applied further in negative X
and Z direction.
So for Seismic analysis there are 18 load
combinations and for Wind load analysis there are
11 load combinations.

STRUCTURAL ANALYSIS:
The procedure of structural analysis is
simple in concept but complex. In detail. It
involves the analysis of a proposed structure to
show that its resistance or strength will meet or
exceed a reasonable expectation. This expectation
is usually expressed by a specified load or the
demand and an acceptable margined of safety that
constitutes a performance goal for a structure. The
performance goals structural design is multifaceted.
Foremost, a structure must perform its intended
function safely over its useful life.

DESIGN OF SLABS:
Assume:
fck = 20 N/mm2
fy = 415 N/mm2
Dimensions of slab: 4.39 × 3.65m
Let Short span = Lx = 3.65m
Longer span = Ly = 4.39m
Ly/L = 4.39/3.65 = 1.20 <2
Hence, te slab is to be designed as a Two way slab
Thickness of slab
Effective depth d=Span/28
= 3650/28
=130.35mm
Let take max depth = 140mm
Total effective depth =140mm
Overall depth = 165mm
Effective spans
Lx = 3.65+0.14 = 3.8m
Ly = 4.39+0.14 = 4.53m
Ly/Lx = 4.53m/3.8m = 1.20< 2 (Two way
slab)
Loads on slab
Dead load = 0.165 x1x 25 = 4.125 KN/m2
Live load = 5.0 KN/m2 Floor
finish =1 KN/m2
Total load = 4.125+5.0+1 = 10.125 KN/m2
Factored load (wu) = 1.5 x 10.125 = 15.187 KN/m2
Design moments and shear forces
Mux = αxwLx
2
Muy = αywLx
2
Where αx, αy are the bending coefficients for two
way slabs for the one long edge and one short
edges are discontinued and negative.
For Ly/Lx = 1.20
αx (-ve) = 0.060
αx (+ve) =0.045
αx (-ve) = 0.047
αx (+ve) =0.035
Mux (-ve)= αx (-ve) × w (lx) 2
=0.060 × 15.182 × 3.82
Mux(-ve)= 13.15 KN-m
Mux(+ve) = αxwLx
2
=0.045 × 15.187 × 3.82
Mux(+ve)= 9.86 KN-m
Muy(-ve)= αy(-ve) × w(lx)2
=0.047 × 15.187 × 3.82
=10.37 KN-m
Muy(+ve)= αy(+ve) × w(lx)2
= 0.035 × 15.187 × 3.82
Muy(+ve)= 7.67 KN-m
Shear force Vu= wu lx /2
= (15.187 x 3.8)/2
= 28.85 KN
Min depth required
Mu = 0.138 × fck × b × d2
13.15x106 = 0.138 × 20 × 1000 × d2
d =69.05
Equation
d = 69.05<140
Hence provided depth is adequate
Reinforcement
Along x-direction (short span)
Mux = 0.87 fy Ast d{1 –( Fy Ast/ Fck b d)}
13.15x106 = 0.87x 415x Astx140 {1 – (415
×Ast/20x1000x140)}
Ast = 271.03mm2
Using 10mm dia bars
Spacing of bars
S = (ast /Ast ) × 1000
= ((π/4×10)2 /271.03) × 1000
=289.77mm = 280mm
Max spacing
i. 3×d = 3×140
= 420 mm
ii. 300 mm
Whichever is less
Hence provide 10mm dia bars @ 280mm spacing
Along y-direction (longer span)
These bars will be placed above the bars in xdirection
d= 140-10 = 130mm
Muy = 0.87 fy Astd {1 – ( Fy Ast/ fckbd)}
10.37x106 = 0.87 × 415 × Ast×130 {1- (415 ×
Ast/20×1000×130) }
Ast = 229.32 mm2
Using 10 mm dia bars
Spacing of bars
S=( ast /Ast ) × 1000
= { ( (π / 4)× 102)/229.32 } × 1000
S = 343.10 mm≈300mm
Max spacing
i. 3×d = 3×140
= 420 mm
ii.300mmWhichever is less
Hence provide 8 mm dia bars at 300mm spacing
Check for shear
τv = (Vu/(b×d) )
= { (28.85 ×103)/(1000 × 140) }
τv = 0.20 N/mm2
%of steel ={ ( 100 ×Ast)/b × d }
= { (100× 243.13) /(1000 ×140) }
= 0.17
As per IS code for M20 concrete
τc = 0.299 N/mm2
τv< τc
0.20<0.299
Hence provided slab is safe

BEAM DESIGN:
A reinforced concrete beam should be able to resist tensile, compressive and shear stress
induced in it by loads on the beam.

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