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"ANALYSIS AND DESIGN OF HIGH RISE G+40 FRAME BASED R.C.C. STRUCTURE"The project is designed for best configuration of the shear walls
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CERTIFICATE
This is to certify that Mr. Rishabh Lala, Mr. Aditya Jain, Mr. Prateek
Singh Choudhary, and Mr. Vedant Mishra, students of Fourth year of
University Dual Degree Integrated Post Graduation Programme have
successfully completed their major project on
ANALYSIS AND DESIGN OF HIGH RISE G+40 FRAME BASED
R.C.C. STRUCTURE
This report is a representation of their work under the supervision and guidance
of Dr. Suresh Singh Kushwah during session 2014-2015.
Dr. SURESH SINGH KUSHWAH
Head of Department
Department of Civil Engineering
Rajiv Gandhi Proudyogiki Vishwavidyalaya,Bhopal
June 2015
ACKNOWLEDGEMENT
Success is epitome of hard work, cogency for fulfilling the mission,
indefatigable perseverance and most of all encouraging guidance and
steering.
It gives me immense pleasure to express my gratitude to Dr. Suresh Singh
Kushwah, Head of Department, his apt mentoring and guidance as well as
support throughout my project kept me on the right track. I also express
my gratitude to all the faculty members of Civil Engineering Department
for their esteemed guidance and able supervision during the course of
project. Their constant encouragement and co-operation made this project
a success.
Lastly, I would like to thank my parents for being the source of motivation
and colleagues who have helped me with their abilities in the completion
of this project.
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ABSTRACT
Besides, food and clothing, shelter is a basic human need. India has been
successful in meeting the food and clothing requirements of its vast population;
however the problem of providing shelter of all is defying solutions. Thus most
current Government policy supports the principle of building in towns and cities at
higher commercial densities. There are many different factors to take into account
when high density is to be delivered in the form of tall buildings.
Hence in order to overcome the problem of higher density requirement,
construction process should be quick, tall and effective to accommodate huge
population in a given area. So we have chosen this topic of “ANALYSIS AND
DESIGN OF HIGH RISE (G+40) R.C.C. STRUCTURE”. Such structures will
definitely provide high density in the form of tall buildings which is necessary to meet
the future needs.
The quickness in R.C.C. construction process and the strength parameters and
effectiveness to bare horizontal loads is very high due to presence of shear walls.
Shear walls are generally used in high earth quake prone areas, as they are highly
efficient in taking the horizontal loads. Not only the earthquake loads but also winds
loads which are quite high in some zones can be taken by these shear walls efficiently
and effectively.
The buildings constructed during the past couple of decades did not take into
account the effect of earthquake and wind loads very effectively. But the effects of
these horizontals loads can prove to be disastrous and thus our project has taken
considerable effect of these loads as specified by the Indian Standard Codes. Moment,
shear and mode analysis of all load combinations as specified by the IS codes have
been done using Computer softwares like AutoCAD, ETABS.
As said by Benjamin Franklin “An investment in knowledge pays the best
interest”. We would like to invest our knowledge to whatever extent we can and
design the building most efficiently.
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Table of Contents
1.INTRODUCTION ...................................................................................................................... 1
1.1Definition ...................................................................................................................... 5
1.2Scope of Work ............................................................................................................... 6
1.3Objective ....................................................................................................................... 6
1.4Methodology................................................................................................................. 7
3.Literature review ................................................................................................................... 4
2.1Indian Standards ........................................................................................................... 8
2.2 Review Of Literature .................................................................................................... 9
3.Earthquake ........................................................................................................................... 10
3.1Earthqake Engineering ............................................................................................... 10
3.2Earthquakes in India ................................................................................................... 12
3.3 Earthquake Resistant Buildings ......................................................................................
4.Design Consideration ........................................................................................... 14
4. 1Desing Consideration ................................................................................................. 14
4.2 Orientation of Columns.............................................................................................. 14
4.3 Loading ....................................................................................................................... 15
4.4Materials ..................................................................................................................... 16
4.5Earthquake Resistant designs ..................................................................................... 16
4.6 Safety ......................................................................................................................... 19
4.7Servicibility .................................................................................................................. 19
4.8 Economy..................................................................................................................... 19
5. Architectural Plan In AUtoCAD
5.1 Plan of Apartments .................................................................................................... 20
6. Modeling in ETABS
6.1 Input Architectural Plan ............................................................................................. 23
6.2 Defining Section Properties ....................................................................................... 25
6.3 Assigning Property To Various Elements ................................................................... 29
6.4Defining and Assigning Loads ..................................................................................... 32
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6.5 Analyzing the structural Behavior .............................................................................. 34
7. Detailed Design of Structure
7.1 Design of Footings ...................................................................................................... 39
7.2 Beams ......................................................................................................................... 39
7.3 Columns ..................................................................................................................... 40
7.4labs .............................................................................................................................. 41
7.5Walls............................................................................................................................ 41
7.6Shear Walls ................................................................................................................. 42
8. Scope for Future Work ........................................................................................................ 56
9. References ........................................................................................................................... 57
List of figures
Figure 3.2.1 Collapse of Intermediate storey of a six storeyed R.C.C. Frame str(Bhuj) ... 11
Figure 3.2.2Damage of RCC Structure due to soft storey at ground floor....................... 11
Figure 3.3.1 Typical Earthquake Resistant Design of Multi Storey .................................. 12
Figure 4.1.1. a. Is preferred over B because of symmetry in Structure ........................... 14
Figure 4.2.1 Orientation of columns is Better in B than in A in given plan ...................... 15
Figure 4.3.1. Line loading on the beams of super structure ........................................... 15
Figure 5 .1.1 AutoCAD Plan of the apartments ................................................................ 21
Figure 5. 1.2Grid lines and column orientation ............................................................... 22
Figure 6.. 1.1 Import AutoCAD File to ETABS ................................................................... 24
Figure 6.1 .2 Final Plan of Structure in ETABS .................................................................. 25
Figure 6.2.1Defining Section Properties .......................................................................... 26
Figure 6.2.2 Defining Beam and Column Properties ........................................................ 27
Figure 6.2.3. Defining Slab Properties ............................................................................. 27
Figure 6.2.4 Defining the wall section Properties ............................................................ 28
Figure 6.3.1 Assigning Properties..................................................................................... 29
Figure 6.3.2.Assigning the slab section properties .......................................................... 30
Figure 6.3.3.Rendered 3D View of Structure ................................................................... 32
Figure 6.4.1. Defining Load Patterns ................................................................................ 33
Figure 6.4.2 Various Load Combination ........................................................................... 34
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Figure 6.4.3 The Applied Live Loads ................................................................................. 34
Figure 6.4.1Defying Load Patterns ................................................................................... 32
Figure 6.4.2 Various Load Combinations ......................................................................... 33
Figure 6.4.3 Applied Live Loads ....................................................................................... 33
Figure 6.5.1 Member force Diagram(Moment 2 -2) ....................................................... 34
Figure 6.5.2 Member force Diagram(Shear 3-3) ............................................................. 35
Figure 6.5.3.Member Force Diagram(Moment 3-3) ........................................................ 35
Figure 6.5.4 Shell Force Diagram(Moment 1-1) ............................................................... 36
Figure 6.5. 5 Deformed Shape(Load Combination IS10) .................................................. 36
Figure 6.5.6 Deformed Shape(Load Combination IS8)..................................................... 37
Figure 6.5.7. Deformed Shape(Load Combination IS I) .................................................... 37
Figure 6.5.3. Member Force Diagram(Moment 3-3) ....................................................... 38
Figure 7.3.1.Special Confining Reinforcement at the joint of Two Floors ....................... 40
Figure 7.3.2. Normal Shear Reinforcement in Columns .................................................. 40
Figure 7.5.1 Location of Shear Walls................................................................................ 42
Figure 7.5.2Pile Cap Details ............................................................................................. 45
Figure 7.5.3 Pile Details .................................................................................................... 46
Figure 7.5.4 Pile Details .................................................................................................... 47
Figure 7.5.5 Orientation of Floor Columns ...................................................................... 48
Figure 7.5.6 Columns Schedule and Cross-Sections ........................................................ 49
Figure 7.5.7 Plinth BeamPlan ........................................................................................... 50
Figure 7.5.8 Beam Plan .................................................................................................... 51
Figure 7.5.9 Beam Schedule and Reinforcement Details ................................................. 52
Figure 7.5.10 Anchorage Details ...................................................................................... 53
Figure 7.5.12 Slab Details ................................................................................................. 54
Figure 7.5.13 Overall Schedule ........................................................................................ 55
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Chapter 1
INTRODUCTION
1.1 Definition:
Reinforced Cement Concrete (R.C.C.) structure is a frame based structure in
which the concrete elements like columns, beams and slabs are reinforced with steel
bars to provide the necessary tensile strength to the structure and thus improve the
strength of the structure on the whole. An RCC framed structure is basically an
assembly of slabs, beams, columns and foundation inter-connected to each other as a
unit. The load transfer in such a structure takes place from the slabs to the beams,
from the beams to the columns and then to the lower columns and finally to the
foundation which in turn transfers it to the soil. The floor area of a R.C.C framed
structure building is 10 to 12 percent more than that of a load bearing walled building.
Hence, there is actual economy in case of RCC framed structures especially where the
cost of land is very high. Also in case of RCC framed structures, the inside planning
of rooms, bathrooms, W.Cs etc. can be altered by changing the position of partition
walls. Thus, there is greater flexibility in planning. Also Speed of construction for
RCC framed structures is more rapid.
Shear walls are vertical elements of the horizontal force resisting system.
Shear walls are constructed to counter the effects of lateral load acting on a structure.
In residential construction, shear walls are straight external walls that typically form a
box which provides all of the lateral support for the building. When shear walls are
designed and constructed properly, and they will have the strength and stiffness to
resist the horizontal forces. In building construction, a rigid vertical diaphragm
capable of transferring lateral forces from exterior walls, floors, and roofs to the
ground foundation in a direction parallel to their planes. Examples are the reinforced-
concrete wall or vertical truss. Lateral forces caused by wind, earthquake, and uneven
settlement loads, in addition to the weight of structure and occupants; create powerful
twisting (torsion) forces. These forces can literally tear (shear) a building apart.
Reinforcing a frame by attaching or placing a rigid wall inside it maintains the shape
of the frame and prevents rotation at the joints. Shear walls are especially important in
high-rise buildings subjected to lateral wind and seismic forces. In the last two
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decades, shear walls became an important part of mid and high-rise residential
buildings. As part of an earthquake resistant building design, these walls are placed in
building plans reducing lateral displacements under earthquake loads. So shear-wall
frame structures are obtained.
1.2 Scope of Work:
The aim of G+ 40 structure is to understand the need of high rise structures to
support the living of large population in a given area. This includes the construction
of a tall structure stabilized against the effects of strong horizontal wind loading and
seismic loading.
The scope is to analyse the structure and then design the structure according to
the deflection, moment and shear of various elements in the structure. For this the
structure is first modelled in ETABS and then analysed based on the investigation of
strength, safety, economy and serviceability. The designing is then done based on the
various Indian Standard Design codes.
1.3 Objective:
The high rise buildings must not only be designed to resist gravity / vertical
loads (due to its self-weight and other living / moving loads), but also designed for
lateral loads of earthquakes / wind. The walls are structurally integrated with roofs /
floors (diaphragms) and other lateral walls running across at right angles, thereby
giving the three dimensional stability for the building structures.
The key objective of shear wall is to build a safe, tall, aesthetic building.
Walls have to resist the uplift forces caused by the pull of the wind. Walls have to
resist the shear forces that try to push the walls over. Walls have to resist the lateral
force of the wind that tries to push the walls in and pull them away from the
building.
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1.4 Methodology:
Step1: The first step was to make an architectural plan for the G+40 structure.
This was done using the software AutoCAD. The plan was of a residential apartment
with six individual flats at each level. The plan that I adopted is one of my internship
projects at Heaven’s Design Bhopal – Project Vishal Heights – Airport Bypass Road,
Bhopal. Columns were marked in 3-D AutoCAD file which was ready for import.
Step2: Location conditions were assumed as with open land so as to maximize
wind effects. Although, Wind Tunnel test have been ignored. Soil condition assumed
is Black soil necessitating the requirement of Pile Foundation. Frame based RCC
Structure with shear walls is decided as the structure type.
Step3: Then the DXF file from AutoCAD was imported to the ETABS 2015
so that the structure could be modelled further. First step in the modelling was
orientation and position of columns required. Various dimensions of columns and
beams were deliberated then chosen with different concrete mix grades so that the
moment and shear load can be tackled and a safe construction is done. The column
orientation and sizes was the most brainstorming affair, keeping in mind stability,
ductility, shear centre, loading positions, torsional stability and mass of the structure.
Step4: Model of the first floor was replicated for 40 storeys after applying
loading. Sectional properties were assigned based on understanding and experience.
Step5: Structure was analysed and mode, deflection, drift checks were
performed.
Step6: Structure was designed based on the analysis output in terms of shear
force and bending moments based on respective code-provisions, using manual
calculations.
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Chapter 2
LITERATURE REVIEW
2.1 Indian Standards:
2.1.1 IS 13920:1993
Ductile Detailing of Reinforced Concrete Structures Subjected to
Seismic Forces – Code of Practice, IS: 4326-1993, "Earthquake Resistant
Design and Construction of Buildings - Code of Practice (Second Revision)",
IS: 456 -2000 “Code of Practice for Plain and Reinforced Concrete”, IS: 2911-
1980, Part III “CODE OF PRACTICE FOR DESIGN AND
CONSTRUCTION OF PILE FOUNDATIONS PART III UNDER-REAMED
PILES”, various sections and clauses were studied for analysis and design of
the model. Code of Practice for Structural Safety of Buildings: Masonry, IS-
NBC-2005: National Building Code of India, was studied for making the
architectural plan of the building, IS: 875-1987Design loads ( other than
earthquake ) for buildings and structures, Part2 Imposed Loads, IS: 875-1987
Design loads ( other than earthquake ) for buildings and structures ,Part 3
Wind Loads, were studied to make proper load combinations of wind and
earthquake forces.
2.1.2 IS 456:2000
For proper installation of reinforcements in Beam-Column joints as per
this code was referred because the structural dimensioning of beams and
columns was inadequate in terms of provisions in IS: 13920-1993. Also the
width depth ratio for slabs and other deigning details were done on the basis
of IS 456:2000 “Plain and Reinforced Concrete- Code of Practice”
2.1.3 SP 34
For the detailing of structural members like beams, columns and slabs
along with the spacing of bars and stirrups was studied from SP34. The
reinforcement detailing of secondary beams and primary beams along with
beam column joints were studied from SP34.
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2.1.4 IS 2911 pile
Pile design formals and various code provisions like clause 5.2.3.1, were
used. The detailing and the pile cap design was studied from the same.
2.2 Review of Literature:
U.H. Varyani described about shear walled buildings under horizontal loads.
Considering in his design, “Reinforced concrete framed buildings are adequate for
resisting both the vertical and the horizontal loads acting on shear walls of a
building”. In his 2nd
edition in 2002 of, “Design of structures” he gave rigidity of
shear wall, torsional rigidity and shear canter of a building in a detailed description.
V. Chandwani, V. Agrawal, N.K. Gupta in the journal IJERA mentioned
“Role of Conceptual Design in High Rise Buildings”. Their paper elaborates the
necessity of conceptual design and differentiating the load resisting system of exterior
and interior structures. They pin pointed Earthquake resistant design and effect of
wind loading as governing structural features.
“IITK-BMTPC Earthquake Tips:: Learning Seismic Design and
Construction“, all 24 tips were studied very carefully and hence their suggestions and
conclusions were applied.
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Chapter 3
EARTHQUAKE
3.1 Earthquake Engineering
An earthquake (also known as a quake, tremor or temblor) is the perceptible
shaking of the surface of the Earth, which can be violent enough to destroy major
buildings and kill thousands of people. Earthquake engineering is one of the more
recent additions to the civil engineering specialties. While all structures have a need to
be designed to be earthquake resistant, it is the proliferation of high-rise buildings
which has sparked the interest in developing earthquake survivability technology.
Seismic events create a number of separate, but interrelated problems for
buildings and other structures. The earthquake itself can move both laterally and
vertically, providing forces to which the structure is not normally subject.
Additionally, earthquakes can cause soil liquefaction, where the soil under a
building flows out from under the foundation, eliminating the structural support that
the building relies on. Other events, such as landslides can be caused by earthquakes,
adding additional hazards.
Earthquake engineering consists of two basic parts: the first is understanding
the effects of earthquakes on buildings and other structures. The second is designing
structures which can withstand the forces brought to bear during an earthquake and
remain safe and serviceable.
3.2 Earthquakes in India
The Indian subcontinent has a history of earthquakes. The reason for the high
frequency and intensity of earthquakes is the Indian plate driving into Asia at a rate of
approximately 49 mm/year. Various places that have received the harshness of
earthquake in India include Latur, Shillong, Bhuj, Andaman, Kashmir etc.
Talking of the Gujrat Earthquake in 2001, a large number of reinforced
concrete multi-storeyed frame buildings were heavily damaged and many of them
collapsed completely in Bhuj in the towns of Kachchh District (viz., Bhuj, Bhachao,
Anjar, Gandhidham and Rapar) and other district towns including Surat and
Ahmedabad. In Ahmedabad alone situated at more than 250 kilometres away from the
Epicentre of the earthquake, 69 buildings collapsed killing about 700 persons.
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Fig. 3.2.1: Collapse of Intermediate storey of a six storeyed R.C.C. Frame str(Bhuj)
Fig. 3.2.2: Damage f RC structure due to soft-story at the ground floor
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3.3 Earthquake Resistant Buildings
The seismic safety of a multi-storeyed reinforced concrete building will
depend upon the initial architectural and structural configuration of the total building,
the quality of the Structural analysis, design and reinforcement detailing of the
building frame to achieve stability of elements and their ductile performance under
severe seismic lading. Proper quality of construction and stability of the infill walls
and partitions are additional safety requirements of the structure as a whole. Any
weakness left in the structure, whether in design or in construction will be fully
revealed during the postulated maximum considered earthquake for the seismic zone
in the earthquake code IS: 1893.
Fig. 3.3.1: Typical Earthquake Resistant design of a multi storey
The main structural elements and their connection shall be designed to have a
ductile failure. This will enable the structure to absorb energy during earthquakes to
avoid sudden collapse of the structure.
Other key points that must be taken under consideration include:
Earthquake resistant design is not earthquake proof design.
Sufficient lateral stiffness is required to ensure that building does not get
damaged under minor shaking.
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The frame should be consistent under major earthquakes also, although it is
allowed to get deformed or have more deflections.
Structural designers have the duty to consider that the structure would be
subjected to an earthquake at least once during the life time of the structure for
which it is designed.
Four virtues of the Earthquake resistant structure are :
a. Good seismic configuration – i.e. Least complexities
b. Lateral stiffness
c. Lateral Strength
d. Good overall ductility
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Chapter 4
DESIGN CONSIDERATIONS
4.1 Structural Configuration
The structural configuration should be regular and symmetrical and as far
as rectangular in nature. The structural centre of rigidity of the structure should
coincide with the centre of mass of the structure; otherwise it would result in the
torsional modes of the structure.
(a) (b)
Fig. 4.1.1: (a) is preferred over (b) because of symmetry in the structure
4.2 Orientation of Columns
The orientation of the columns should be so adjusted that it is symmetrical
their configuration is symmetrical in nature. Again we have to make sure that there
are no torsional modes arising due to the irregular structural configuration. Another
philosophy that is considered during the assignment of the column is that the columns
are oriented in the longer direction. Also care is taken corner and middle columns
could bear the biaxial moments properly
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(a) (b)
Fig. 4.2.1: Orientation of Columns is better in (b) than in (a) in a given plan
4.3 Loading
The various load that need to be considered while deigning a structure
includes the self-weight (viz. the dead weight of the super structure); live load (viz.
the load that the structure will undertake due to the occupants); wall load (viz. the
load of the brick walls or claddings used); wind load (viz. the horizontal load exerted
by wind forces) and earthquake load.
Fig. 4.3.1: Line loading on the beams of super structure
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4.4 Materials
The various material specification and the quantities to be used for
optimum and safe design of structures are as follows:
a. Cement: Ordinary portland cement conforming to IS 269 - 1976 shall
be used along with fly ash after carrying out the design mix from
approved consultant.
b. Reinforcement: Cold twisted high yield strength deformed bars grade
Fe 415 conforming to IS: 1786-1985, or preferably TMT bars of
standard manufacturer e.g. TATA Steel, SAIL or equivalent shall be
used.
c. The following grades of concrete mix may be adopted or as required
for safe design:
For RCC columns in lowest few storeys : M35 – M50
For RCC columns in the middle few storeys : M30 – M40
For RCC columns in the top few storeys : M25 – M35
For beams, slabs, staircase etc. : M25
For raft foundation : M25 or more
d. Max. Water cement Ratio : 0.45
e. Minimum cement content : 300 kg/m3 of concrete.
f. Admixtures of approved brand may be used as per mix design
4.5 Earthquake Resistant Design
There are numerous points to be kept in mind while deigning of earthquake
resistant buildings. Some of the important key features include:
No member should be smaller than 200mm
The width to depth ratio for no member should be smaller than 0.3
The depth of member should not be more than 1/4 of the clear span
The spacing of stirrups over the length 2d should not be less then
the following :
100mm
8 times the diameter of the smallest bar used at the junction
d/4
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Design shear force shall be the maximum of the shear force of the
member as per analysis.
The first hoop shall not be placed at a distance more than 50mm
Elsewhere the stirrups can have spacing more than d/2
The shortest dimension for members(Beams) should not be less then
300 mm for beams longer then 5m or 4 metres of unsupported
length
Not more than 50% of the bars shall be spliced(Overlapped) at one
section.
Lap splices should be provided only at the central half of the
member
Not more than 150mm spacing should be provided in stirrups in
case of splices.
The spacing of the stirrups shall be not more than .5 x The least
lateral dimension, in case of the column.
Special Confining reinforcement is provided usually for the
discontinuous walls on both sides of the column, where there is no
wall on both the sides, this is due to the fact that the column starts
behaving as short column in case of earthquake and undergoes
brittle failure and hence that part of column needs to be specially
confined.
The column with special confining reinforcement should be
provided in the column when it is terminated in the footing and it
should enter at least 300mm into the footing.
When the point of contra flexure is not within the middle half of the
member (column), Special Confining Reinforcement should be
provided over the complete column.
The spacing of the SCR shall not be more than 100mm and not less
than 75 mm and not less than 1/4 of the minimum member
dimension.
Use minimum 8mm diameter for SPR
8 mm diameter at spacing 70 mm is generally used
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At the end of the column, from which the beams span in all the
directions and all beams are having width at least 0.75 x width of
the respective column face, the SPR can be reduced by 50% , with
spacing not exceeding 150mm.
Lift cores should not be provided at one end of the building as this
may lead to high torsional shear on the columns.
The orientation should be done primarily on the basis of
maintaining the stiffness in the foundation, so that the group piles
do not allow the soil to be weakened. It will act like the roots of the
plants. Hence preventing the movement of the soil in the opposite
directions.
Highly flexible soil makes the footings as good as fixed and rocky
soil makes them fixed. The flexibility is generally seen in case of
isolated footings.
This flexibility creates more chances of lateral sway in the lower
storeys than in the higher storeys. The overall response of the
building turns into shear type.
We design buildings for shear type response, which means the
columns and beams fail in shear.
Hinged column base will lead to the higher mode shape.
No two periods of natural translation should be within 15% of the
natural period of the largest translation.
Buildings consisting of the open ground floors(Stilt Storey), is
problematic, as due to the increased(4 to times) stiffness of the
upper storey, the buildings may fail due to the soft ground storey,
the simple way we can avoid this is by making brick infill at all four
corners, also the ground columns(soft storey columns) should be
designed for 2.5 times shear and moments
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4.6 Safety
Safety consideration is perhaps the most important factor that must be kept
in mind while design of any structure. This safety refers to the safety of the people
present the building as well as their belongings. This is achieved when the designed
structure is under the deflection limits and does not have any storey drifts. Due
consideration must be made for wind loading and earthquake impact.
4.7 Serviceability
A serviceability limit defines the performance criterion for serviceability
and corresponds to conditions beyond which specified service requirements resulting
from the planned use are no longer met. a structure fails its serviceability if the criteria
of the serviceability limit state are not met during the specified service life and with
the required reliability. Hence, the serviceability limit state identifies a civil
engineering structure which fails to meet technical requirements for use even though
it may be strong enough to remain standing. A structure that fails serviceability has
exceeded a defined limit for properties like excessive deflection, vibration of local
deformation.
4.8 Economy
Economy is also an important factor that must be kept in mind while
designing any structure. A structure which is safe and serviceable but not economic
will not be preferred by people over structures which are safe, economic and
serviceable. Thus while designing of any structure the economics factor must also be
taken into consideration.
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Chapter 5
ARCHITECTURAL PLAN IN AUTOCAD
5.1 Plan of Apartments
The architectural plan in AutoCAD consists of the plan layout of the
residential apartments highlighting the dimensions of various rooms. It also shows the
Provision of windows, doors, lift wells etc. Studying this plan carefully, one can
decide thw orientation of columns that must be provided so as to attain stability.
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Fig. 5.1.1 AutoCAD plan of the apartments
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Fig. 5.1.2: Grid lines and column orientation
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Chapter 6
MODELLING IN ETABS
6.1 Import Architectural plan
The first step of modelling is the preparation of the frame of the structure.
This was done by importing the architectural plan made in AutoCAD. The .DXF file
of AutoCAD can be imported to ETABS easily by selecting File => Import => .DXF
file of Architectural grids.
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Fig 6.1.1 Import AutoCAD file to ETABS
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Fig 6.1.2: Final Plan of structure in ETABS
6.2 Defining Section Properties
The main step after getting the position of columns and beams in ETABS
is to define the various cross sections of these elements. Defining these
members include assigning the type of cross section and its dimensions,
the material used (concrete mix deign in this case).
The members can be defined by Define => Section Properties. Frame, slab
or wall sections whichever is to be defined.
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Fig. 6.2.1: Defining Section Properties
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Fig. 6.2.2: Defining Beam and Column properties
Fig. 6.2.3: Defining Slab properties
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Fig. 6.2.4: Defining the wall section properties
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6.3 Assigning Properties to various elements
These definitions can be assigned to different members by either selecting
them individually with mouse button clicks or by selecting them from the
select tool in the toolbar.
Fig. 6.3.1: Assigning properties
The sections assigned to any member can later be changed at any point of
time, very easily and effectively. In way the properties can be changed and then
analysed to check which dimension and type of member is more suitable for any
given requirement. This easy to use and nice graphical user interface makes the use of
ETABS easy, efficient and thus reliable.
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Fig. 6.3.2: Assigning the slab section properties
After assigning various section properties, we may have a glance of how
the structure might look when it will be constructed. This can be seen by extrude
command from the tool bar.
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Fig. 6.3.3: Rendered 3D view of the structure
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6.4 Defining and Assigning Loads
After the completion of assignment of various properties, the next step
then is to assign loads to the various members. These loads include primarily the dead
load of the structure which is computed by the software itself. It is then followed by
assigning area loads at the slab levels which will come in the form of live load. Line
load on to beams may be assigned where cantilever slabs are present. The load is
automatically transferred from the slabs, to the beam and then columns and then
finally to the foundation provided.
Fig. 6.4.1: Defining Load Patterns
For this the load patterns must be defined first as shown in Figure. Also
Load combinations must be defined as per Indian Standard Codes. The software itself
creates some combinations as per the code in the software itself.
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Fig. 6.4.2: Various Load Combinations
Fig. 6.4.3: The applied live load
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6.5 Analysing the Structural Behaviour
This is perhaps the most important part for any structural designer. After
the structure has been analysed, it is of prime importance that the behaviour of
structure could be understood using the analysis results. The analysis results include
the moment, shear and torsion at any given section. Some of the analysis results are
shown in the figures below.
Fig. 6.5.1: Member force diagram (Moment 2-2)
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Fig. 6.5.2: Member force Diagram (Shear 3-3)
Fig. 6.5.3: Member force diagram (Moment 3-3)
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Fig. 6.5.4: Shell force diagram (Moment M 1-1)
Fig. 6.5.5: Deformed Shape (Load Combination: IS 10)
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Fig. 6.5.6: Deformed Shape (Load Combination: IS 8)
Fig. 6.5.7: Deformed Shape (Load Combination: IS 1)
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Fig. 6.5.8: Plan View of the Moment Diagrams
The above analysis results were considered and formed the basis of our design. The
moments were used to design the beams and axial load given by the software, formed
the basis of the bi-axial bending design of the columns. The Beams were also checked
for the shear forces.
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Chapter 7
DETAILED DESIGN OF STRUCTURE
7.1 Design of footing :
The pile foundation was considered to be best fit for the loads
coming on the fixed restraints. The loads coming were in the range of
7000 KN to 11000 KN and hence piles were designed on the basis of
the loads coming on the columns. Combined piles- group of three piles
having diameter 400 mm and 600 mm were taking at appropriate
restraints.
The piles caps were designed on the basis of the bending moments
and hence checked for punching shear. The Pile Caps act like slabs
which distribute the load on the piles. The piles were given
reinforcement on of 12mm longitudinal.
The shearing angle considered for our analysis is Ф = 35 and the
number of under – reams in the 12 metre long pile were 4. The
average unit weight of the soil considered for our analysis was – 2 x
10-3
kg/cm3. The values obtained on the basis of the shearing angle
were : Nq = 41.4, Ny = 42.4 (Bearing Capacity Factors).
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Fir7.1.1 Manual Calculations for Footing Design (Pile Bearing Capacity)
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Fir7.1.2 Manual Calculations for Footing Design (Pile Bearing Capacity)
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7.2 Beams
The plinth beams were grouped on the basis of the analysis and
these were hence designed based on their grouped bending moments.
The beams of further storeys having approximately similar bending
moments designed as per bending moment and checked for shear.
Proper shear reinforcement was provided. The design philosophy that
was used her was – ductility of structure should be maintained.
Therefore the beams are designed with less grade concrete as compared
to that of columns.
7.3 Columns
The columns were checked for axial compressive loads based on the
analysis and hence grouped in 4 types i.e. C1, C2, C3, C4; depending
on the axial loads of plus / minus 15% from the average were grouped
together and hence designed for the higher side.
Confined shear reinforcement was provided at beam and column joints
and at places of varying stiffness.
Fig. 7.3.1: Special Confining Reinforcement at the Joint of two floors,
ETABS Design Check
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Fig. 7.3.2: Normal Shear Reinforcement in Column
7.4 Slab
Slabs were analysed as shells in ETABS which can bear some
moments and also transfer the loads on the respective beams. The
moment coming on slab was analysed and was in the range of 5 to
15KN/mm2. The slabs were designed on using formulae given in
IS:456 2000 and tensile reinforcement based on the bending moment
were provided. Slabs designed were of two types – i.e. One Way and
Two Way slabs.
7.5 Walls
The loads for façade work was considered in the analysis and
hence we propose that only façade work should be used for outer walls.
For internal brick walls, a proper gap should be considered in between the
columns and the walls. This gap should be filled with thermacol and
hence plastered. This is done to avoid the increase in stiffness in the actual
site and compared to the actual model which could result in the change in
the time period.
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7.5 Shear Walls
Shear Walls are used to resist the lateral loads. They may prove to be
economical if designed properly. They are used resist the earthquake loads. Shear walls
used to resist the wind loads and earthquake loads. We have designed the shear walls of
350 of M-35. Their location depends on the stiffness required and care should be taken to
avoid any torsional rigidity. Various combinations of sheer walls were tried and this is
the configuration, which gave best results in terms of deflection, torsional mode shape,
and economy.
Fig. 7.5.1: Location of Shear Walls
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Chapter 8
SCOPE FOR FUTURE WORK
Future work should be concentrated on the use of damper that should like
Tuned mass Damper, Tuned liquid mass damper and their effects along with
economy. This can also be analysed in the software ETABS. This can have have
tremendous effects on the time period of the structure and can result in avoiding the
condition of resonance.
A Mass Damper, analysed as spring mass system results in increasing the
mass of the combined system and keeps the time period away from that of the
earthquake frequency.
Day by day the demand for the high rise is increasing and the number of
floors is also increasing as the money power is increasing. But for architectural and
structural limitations, the damper can come handy, especially in India, where
knowledge in this sector is limited to few.
The studies have to be conducted on the availability of the materials for
proper construction of the damper and also on the codal provisions should be worked
out for damping effects
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Chapter 8
REFERENCES
IS 456:2000 “Plain and Reinforced Concrete- Code of Practice”
IS 13920:1993 Ductile Detailing of Reinforced Concrete Structures
Subjected to Seismic Forces – Code of Practice
IS: 4326-1993, "Earthquake Resistant Design and Construction of
Buildings - Code of Practice (Second Revision)"
IS: 456 -2000 “Code of Practice for Plain and Reinforced Concrete”
IS: 1904-1987 “Code of Practice for Structural Safety of Buildings:
Foundation
IS: 1905-1987, Code of Practice for Structural Safety of Buildings:
Masonry
IS-NBC-2005: National Building Code of India
IS: 875-1987Design loads ( other than earthquake ) for buildings and
structures, Part2 Imposed Loads
IS: 875-1987Design loads ( other than earthquake ) for buildings and
structures ,Part 3 Wind Loads
V. Chandwani, V. Agrawal, N.K. Gupta in the journal IJERA mentioned “Role of
Conceptual Design in High Rise Buildings”.
IS 2911 - 1980, Part III “CODE OF PRACTICE FOR DESIGN AND CONSTRUCTION OF PILE
FOUNDATIONS PART III UNDER-REAMED PILES”
