1. TRIBHUWAN UNIVERSITY
INSTITUTE OF ENGINEERING
PURWANCHAL CAMPUS, DHARAN
A PROJECT REPORT ON
DESIGN OF ACADEMIC ADMINISTRATIVE BUILDING
Prepared by :- Project advisor:-
1. Abhishek Pokharel (068/BCE/02) Er.Raju Ghimire
2. Animesh Nepal (068/BCE/05)
3. Arif Ali (068/BCE/06)
4. Ganesh Thapa (068/BCE/15)
5. Hasrat Ali Nepal (068/BCE/18)
6. Namu Timilsina (068/BCE/22)
7. Saroj Gautam (068/BCE/38)
Submitted to: Department of Civil
Engineering,Purwanchal Campus,Dharan
2. I
CERTIFICATE
This is to certify that this project entitled “Design of Academic Administrative
Building” has been examined and it has been declared successful for the partial
fulfillment of the academic requirement towards the completion of Bachelor’s Degree
in Civil Engineering.
1. Er.Raju Ghimire ………………..
Project Advisor Date-
2. Er.Raju Ghimire ………………
Head of Department Date-
3. Er.JitendraChaudhary ………………
Campus Chief Date-
3. II
PREFACE
A course entitled “Civil Engineering Project” is prescribed by the TU, Institute of
Engineering as a practicing of case study and helping tool to get familiar with the
practical problems that every professional has to face in their professional life.
This project is the practical use of theoretical knowledge that we acquired during the
four years of Civil Engineering course with application of knowledge we gained from
our respectable teachers and superiors.
We have chosen the project “DESIGN OF ACADEMIC ADMINISTRATIVE
BUILDING”. The course offered in 4th year 1st part namely “Design of Reinforced
Concrete Structure” is a strong base. This course really helped us while designing the
structure and provided the knowledge to design the structure in terms of safety,
economy, stability and efficiency.
During the project work, we got to know thoroughly that how to analyze and tackle the
problems and got the optimal result which will safeguard the lives of people and the
structure itself in the state of seismic disaster.
This project work also helped us to work with Team spirit and the coordination for the
long term work and getting through the problems effectively.
In gist, it was a real enthusiasm and full supportive to work under the guidance of our
project supervisor Er.Raju Ghimire, Er.Yaswant Bikram Sah and Er.Yuman
Shakya who always guided us with valuable tips while tackling the problems and gave
in-depth knowledge of structural engineering. We believe that his valuable guidance and
support is profoundly appreciable and will always help us in our future professional life.
4. III
ABSTRACT
Tribhuvan University, Institute of Engineering, Purwanchal Campus offers a four year
course on bachelor degree in Civil Engineering and at the final semester as the practical
use of the theoretical knowledge that we acquire during the four year we have to
complete a project work. Project on different topics are performed which may be
allocated by the institute or the students may bring the project by ourselves.
One of the major causes of failure of any structure is its improper analysis and design.
So, proper knowledge on analysis and design of structure is utmost necessary. This
project work on “Design of Academic Administrative Building” presents the analysis
and design of structural components of Administrative building. After acquiring the
Architectural drawings of the building, Structural design is carried out: initially by
Preliminary Design and then Detail Design. A preliminary design is carried out for the
structural components of the building using IS-456:2000 and SP-16. Then, the load
calculation is done using IS-875(Part I–V) and IS-1893:2002. The loads acting on the
building comprise of dead loads, live loads and seismic/earthquake loads. After
identification and evaluation of all the loads acting in the building, analysis of structure
is done by providing different load combinations in the computer software SAP 2000
v14. After SAP analysis, results are extracted. Then, Detail Design is carried out taking
the results of severest combination of loads from SAP analysis. The Detail Design of
structural elements is also based on the provisions provided by the relevant codes. After
detail design, the results are tabulated and the structural drawings (detailing) are drawn
showing the results in a prescribed format governed by relevant codes. Thus, the
designed building is ready for the process of construction.
5. IV
ACKNOWLEDGEMENT
Nearing graduation, after which we would qualify as full engineers, the desire to learn
about an analysis and design of structures for structural safety and economic reasons has
motivated us for this project, entitled “Design of Administrative Building.”
To begin with, we would like to express sincere gratitude to our project
supervisor and respected teacher Er.Raju Ghimire, lecturer, IOE, for providing
immense guidance and support. We benefitted a lot in a great deal from his
logical thoughts, experience, incisive comments and critical estimation. His ideas and
methods of dealing in the design of structure are very praiseworthy and appreciable.
He delivered the complete knowledge required to design a safe and economical
structures. We have great sense of gratitude towards our respected teachers Assoc Prof.
Er. Narendra Jung Dangi, Er. Yuman Shakya, Er. Yashwant Bikram Shah. This
project wouldn’t have been completed so successfully without their kind supports,
untiring efforts and encouragements in each and every task. They will be ever
remembered in our memory as very good, kind and generous personalities. Also, we are
extremely thankful towards all lectures who laid foundations on structure during B.E.
courses through semesters 1st through 8th.
Finally, we would like to thank all the persons who helped us directly and indirectly in
completing the project work and preparing this report. We also acknowledge our
gratitude towards each other for such a united coordination amongst the group members
during the project
Project Members
Abhishek Pokharel(068/BCE/2)
Animesh Nepal(068/BCE/5)
Arif Ali (068/BCE/6)
Ganesh Thapa(068/BCE/15)
Hasrat Ali Nepal (068/BCE/ 18)
Namu Timilsina (068/BCE/ 22)
Saroj Gautam(068/BCE/38)
6. V
TABLE OF CONTENTS
CERTIFICATE..................................................................................................................I
PREFACE........................................................................................................................ II
ABSTRACT................................................................................................................... III
ACKNOWLEDGEMENT..............................................................................................IV
LIST OF SYMBOLS AND ABBREVIATION .......................................................... VIII
List of symbols......................................................................................................... VIII
Abbreviations............................................................................................................... X
EXECUTIVE SUMMARY ........................................................................................... XI
PROCEDURE..............................................................................................................XII
CHAPTER 1.INTRODUCTION...................................................................................... 1
1.1 Background............................................................................................................. 1
1.2 Flow chart showing our work division. .................................................................. 2
1.3 Theme of the Project work...................................................................................... 3
1.4 Objectives & Scopes............................................................................................... 4
1.5 Building description................................................................................................ 5
1.6 Location Plan of Administrative Building.............................................................. 6
1.7 Identification of loads ............................................................................................. 6
1.8 Method of Analysis................................................................................................. 7
1.9 Design..................................................................................................................... 7
1.10 Detailing................................................................................................................ 7
1.11 Code of Practices .................................................................................................. 7
1.12 Idealization and Assumption in Analysis and Design .......................................... 8
CHAPTER 2.STRUCTURAL LOADING AND PRELIMINARY DESIGN ................. 9
2.1Introduction............................................................................................................ 10
7. VI
2.2 Structural Consideration ....................................................................................... 10
2.3 Structural Arrangement Plan ................................................................................ 11
2.4 Structural Loading ................................................................................................ 12
2.4.1 Dead load....................................................................................................... 12
2.4.2 Live load ........................................................................................................ 12
2.4.3 Earthquake load ............................................................................................. 13
2.4.4 Other loads..................................................................................................... 14
2.5 Preliminary Design ............................................................................................... 14
2.5.1) Preliminary design of slab........................................................................... 15
2.5.2) Preliminary design of beam......................................................................... 15
2.5.3) Preliminary design of column ...................................................................... 16
2.5.4) Preliminary design of staircase..................................................................... 18
2.5.5) Load calculation ........................................................................................... 18
2.6) Mass lumping ...................................................................................................... 19
2.7) Assessment of lateral loads ................................................................................ 22
CHAPTER 3.MODELLING AND ANALYSIS OF BUILDING.................................. 27
3.1) Analysis of building ............................................................................................ 28
3.2) Beam and Column number.................................................................................. 29
3.3) Load cases and combinations.............................................................................. 29
3.4)Caalculation of storey drift………………………………………………………30
CHAPTER 4. DESIGN SECTION................................................................................ 32
4.1) Design of Slab ..................................................................................................... 33
4.2) Design of Column................................................................................................ 47
4.3) Design of Beam ................................................................................................... 60
4.4) Design of Staircase.............................................................................................. 82
4.5) Design of Foundation .......................................................................................... 84
8. VII
CHAPTER 5.DETAILING OF STRUCTURAL ELEMENT.........................................89
CHAPTER 6. CONCLUSION AND LIMITATIONS.................................................. 91
CHAPTER 7.RECOMMENDATIONS.......................................................................... 93
CHAPTER 8.REFERENCE AND CODES.................................................................... 95
CHAPTER 9.ARCITECTURAL DRAWINGS
CHAPTER 10. STRUCTURAL DRAWINGS
9. VIII
LIST OF SYMBOLS AND ABBREVIATION
List of symbols
Symbols Description
Ac - Area of concrete
Ah - Horizontal seismic coefficient
Ag - Gross area of section
Ast - Area of tension reinforcement
Asc - Area of compression reinforcement
Asv - Area of vertical stirrup
bf - Effective width of flanged section
bw - Breadth of web in T or L – section
D - Overall depth of the section
d - Effective depth of the section
Df - Thickness of the flange T or L- section
fck - Characteristics compressive strength of concrete
fy - Characteristic yield strength of steel
I - Importance factor of the structure
Ix, Iy - Moment of inertia about X- and Y- axis respectively
hi - Height of the ith floor base of frame
k - Performance factor depending on the structural framing system
and brittleness or ductility of the construction
leff - Effective length of the element
lx, ly - Span of slab in the shorter and longer direction respectively
l - Unsupported length or clear span of element
l0 - Distance between points of inflection
10. IX
Ld - Development length of the bar
Mu - Factored moment, Design moment for limit state design
Mu lim - Limiting moment of resistance
Mux, Muy - Factored moment about X- and Y-axis respectively
Muxl, Muyl - Maximum uniaxial moment capacity of the section with axial load,
Bending about X- and Y- axis, respectively
P - Axail load on the element
Pu - Factored axial load, designed axial load for limit state design
pc - Percentage of compressive reinforcement
pt - Percentage of tension reinforcement
Qi - Base shear distributed in ith
floor
Sv - Spacing of stirrup
T - Fundamental time period of building (sec)
V - Shear force
Vu - Design shear force for limit state design, factored shear force
Vus - Strength of shear reinforcement in the limit state design
Vb - Total base shear
Wi - Lump load on the ith floor
Xu - Depth of neutral axis in limit state of collapse
Xu max - Maximum depth of neutral axis in limit state of design
α - Coefficient
αx, αy - Bending moment coefficient for slab about X- and Y- axis restively.
β - Coefficient depending upon the soil foundation system and span
Longer than 10m
λ - Coefficient depending upon bf / bw ratio
δ - Coefficient depending upon pc
11. X
τc - Allowable shear stress in concrete
τbd - Allowable bond stress in concrete
τc,max - Allowable maximum shear stress in concrete with shear
Reinforcement
Τv - Nominal shear stress
Φ - Diameter of bar
Abbreviations
CR - Center of Rigidity
DL - Dead Load
EQ - Earthquake Load
IS - Indian Standard
LL - Live Load
RCC - Reinforced Cement Concrete
12. XI
EXECUTIVE SUMMARY
Rapid urbanization has increased the importance of RCC building in urban areas of
Nepal. The structural safety and serviceability of these buildings may be open to
discussion due to various reasons such as age factors, lack of rigorous structural
analysis, design without considering earthquake and wind forces, change in exposure
and usage conditions etc. Thus people might be living in the buildings which may be
considered not safe for this purpose. Moreover, Dharan, being in severe seismic zone V,
(IS 1893:2002), seismic considerations is necessity
The effectively design buildings could be helpful in saving lives and properties from the
unpredicted failure of the building structures. The aim of reinforced concrete design is
the achievement of an acceptable probability that structures being designed will perform
satisfactorily during their intended life. With an appropriate degree of safety they should
sustain the entire load and the deformation of normal construction and use and have
adequate durability and adequate resistance to the effect of misuse and fire.
We are mainly dealing with seismic analysis and structural design of RCC framed
concrete structure. Our main focus will be on obtaining design output by limit state
method on basis of structural design incorporating seismic considerations Keeping in
mind all these facts and the limitation of the manual calculations, the use computer has
been taken as the important aspect of our project. The help and use of SAP 2000v14.1,
Autodesk (AutoCAD 2013), and other necessary software such as Microsoft Word,
Excel was done for completion of our project report.
Structure and structural elements are normally designed by limit state method. Proper
account is taken of accepted theories, experiment and experience and the need to design
for durability. Calculation alone does not produce safe, serviceable and durable
structures. Suitable materials, quality control, adequate detailing and good supervision
are equally important.
13. XII
PROCEDURE
The entire process adopted for the status evaluation of RCC building can be summed up
in the schematic relation one following other as shown below.
1. Finalize the Architectural drawing
2. Building for Administrative purpose
3. Functional use of each room is analyzed
4. Site parameters like bearing capacity,is obtained
5. Identifying maximum span of beam from drawing
6. Approximating depth of beam from deflection criteria
7. Identifying maximum shortest span from the panel of the drawing
8. Approximating of preliminary depth of slab from deflection criteria
9. Locating the column occupying maximum area of slab
10. Calculating total load on the column (P)
11. Preliminary design of Column, Beam and Slab, fixing of sections and depths as per
code.
12. Modeling in SAP 2000v14.1
13. Assigning loads
14. Run for analysis
15. Interpreting Results
16. Making detail as per IS codes
14. XIII
In load assessment stage: Dead loads, live loads and seismic loads acting or likely to
be acted on the building were determined. Dead and Live loads were assumed based on
IS 875:1987 and seismic loads were calculated by response spectrum method adopting
IS 1893:2002.
During modeling: 3D computer models of building were prepared using SAP 2000.
Beams and columns were modeled as frame elements. The dead loads of the elements
were incorporated by defining the material, frame sections and area sections. The dead
load (DL), live load (LL), earthquake force in X-direction (EQx) and earthquake force in
Y-direction (EQy) were defined as a load case and assigned at appropriate nodes,
lengths and directions.
During the analysis stage: 13 various loads combinations suggested by IS
875(part5):1987 were defined. The computer model was run for above defined load
cases and combination.. The results of analysis were processed to obtain the maximum
internal forces and stresses required for design purpose.
In the design stage: The structural elements were designed by limit state method,
considering limit states of collapse and serviceability. IS: 456-2000 and IS: 13920-1993
was taken as two fundamental codes of practices for design of structural components.
The design aids and handbooks SP-16, and SP-34 of Indian Standards were also
followed.
IN THE DESIGN:
1. The slabs were designed to resist the moment induced by a load combination of
1.5(DL+LL). The adequacy of the section was to resist the shear force and to
fulfill the deflection criteria.
2. Three sections of each and every beam were designed for the combined effect of
flexure. A single section for the same beam were designed for shear. Empirical
methods were adopted to control the deflection of beams. In the whole process
maximum (forces and stresses) of 13 combinations were considered.
3. The longitudinal steel for the critical section of every column was designed
considering biaxial bending along with compression induced due to 13 load
combination. The reinforcements were provided adopting IS 456:2000 and SP
34.
15. XIV
4. Isolated footings below the columns were designed for column axial forces.
Adequacy of the bearing capacity of soil and depth provided to prevent the shear
failure was checked.
5. The staircases were designed for 1.5(DL+LL), where the manual analysis was
done to calculate the forces and stresses. In each design, the concrete section
was maintained same as provided one and reinforcements were varied. Remarks
were made where maximum reinforcement placed inside concrete demands an
increase in the concrete section to withstand the loads.
In the stage of comparison, percentage of longitudinal reinforcement required was
compared with the provided one. The shear and transverse reinforcements were
compared in terms of their spacing, maintaining the diameter same as the provided
ones. The development lengths required were also checked in appropriate places.
The detailing actually done was compared with the code requirements. Finally the
sections of inadequate designs were identified and the correction measures were
recommended
17. 1
1.1 Background
As Dharan is located in high earthquake prone zone, so there may be a chance of serious
accident including loss of life when earthquake occurrs. So, the proper design and
analysis of Administrative Building is required. Otherwise it may lead further more
accidents like the failure of building together with life of people.
A designer has to deal with various structures ranging from simple ones like curtain
rods and electric poles to more complex ones like multistoried frame buildings, shell
roofs, bridges, etc. These structures are subjected to various loads like concentrated
loads, uniformly distributed loads, uniformly varying loads, live loads, dead loads and
dynamic loads. The structure transfers the loads acting on it to the supports and
ultimately to the ground. While transferring the loads to the structure, the members of
the structure are subjected to the internal forces like axial forces, shearing forces,
bending and tensional moments. Structural analysis deals with analyzing these internal
forces in the members of the structures. Structural design deals with sizing various
members of the structures to resist the internal to which they are subjected during their
effective life span. Unless the proper structural detailing method is adopted the
structural member will be no more effective. The Indian standard code of practice
should be thoroughly adopted for proper analysis, design and detailing with respect to
safety, economy, stability and strength.
The project selected by our group is Administrative building located at
Vijaypur,Dharan. According to IS 1893:2000, Dharan lies on zone-V, the severest one.
Hence the effect of earthquake is pre-dominant than the wind load. So, the building is
analyzed for earthquake as lateral load. The seismic coefficient design method as
stipulated in IS 1893:2002 is applied to analyze the building for earthquake. Special
reinforced concrete moment resisting frame is considered as the main structural system
of the building.
The project report has been prepared in complete conformity with various stipulations
in Indian standards, code of practice for plain and reinforced concrete IS456-2000&SP-
16,criteria for earthquake resistant design structures IS1893-2000,ductile detailing of
reinforced concrete structures subjected to seismic forces-code of practice isIS13920-
18. 2
1993, handbook on concrete reinforcement and detailing SP 34. Use of these codes have
emphasized on providing sufficient safety, economy, strength and ductility besides
satisfactory serviceability requirements of cracking and deflection in concrete
structures. These codes are based on principles of limit state of design.
This project has been undertaken as a partial requirement for B.E. degree in civil
engineering. All the theoretical knowledge on analysis and design acquired on the
course work are utilized with practical application.
The main objective of the project is to acquaint in the practical aspects of civil
engineering. We being the budding engineers of tomorrow, are, interested in such
analysis and design of structures which will, we hope, help us in similar jobs that we
might have in our hands in the future.
1.2 Flow chart showing our work division.
Figure 1: Work breakdown structure
PRELIMINARY DESIGN
MODELLING OF
STRUCTURES
ASSIGNING LOADS IN
THE MODEL
ANALYSIS OF
STRUCTURE
DESIGN AND DETAILING
OF STRUCTURES
19. 3
1.3 Theme of the Project work
This group under the project work has undertaken the structural analysis and design of
Academic Administrative Building. The main aim of the project work under the title is
to acquire knowledge and skill with an emphasis of practical application. Besides the
utilization of analytical methods and design approaches, exposure and application of
various available codes of practices is another aim of the work.
1.4 Objectives & Scopes
The specific objectives of the project work are
To design modern administrative building such that every sections of
administrative building like storage, circulation, staff working space, electronic
workstation space, conference room, account section, exam section etc. can be
well managed.
To provide a total document of modern administrative building to C.C.T,
Hattisar, Dharan
Structural element layout in the existing architectural plan.
Preliminary design and estimation of loads for dead, live and earthquake.
Modeling of the building for structural analysis
Detailed structural analysis using structural analysis program.
Structural design and detailing of members.
To achieve above objectives, the following schedule of work is planned
Identification of the building and the requirement of the space.
Estimation of loads including those due to earthquake
Preliminary design for geometry of structural elements.
Determination of fundamental time period by free vibration analysis.
Calculation of base shear and vertical distribution of equivalent earthquake load.
Identification of load cases and load combination cases.
Review of analysis outputs for design of individual components
Design of RC frame members, walls, foundation, and staircase by limit state
method of design
Detailing of individual members and preparation of drawings as a part of
working construction document.
20. 4
Scope
The project work is limited to the structural analysis and design only.
Design and Detailing of following structural elements is performed:
Slab
Beam
Column
Staircase
Isolated footing
Design and layout of the building services like pipeline, electrical appliances, sanitary
and sewage system are not covered.
The project is not concerned with the existing soil condition of the locality. The bearing
capacity of the soil is 150 KN/m2
which is taken as the standard bearing capacity of
Dharan.
General assumptions made for each sections and rooms are :-
a) Exam section
Exam section has space specifications for:-
Confidential room for
i. Personal file
ii. Examination work
Section for scrutinization and Moderation
Section for Examination of answer sheet
Store for exam copies (new/old paper)
Space for head of the section
Space for other staffs
Space for student consultation
Space for examination copy store ( if copies are centrally collected and
then distributed)
Space for separate work copy area(photocopy machine, fax.etc)
b) Account Section
Account section has space specifications for :-
Bill counter
Space for head of the section
21. 5
Space for other staffs
Store for files and records
c) Store Section
Space for Store Section Chief
Rack storage for files.
Space to make a stash for disfunctioning equipments and new products
before its installation.
d) Parking space is only for cars and motor- cycles.
e) Campus chief office and asst. campus office have combine access to the meeting
hall.
f) A waiting Room is for consulting and waiting before entering Campus Chief's or
Asst.Campus Chief's Room. It also contains pantry with small space for lunch
making.
g) Conference Room is designed for 28persons ; the width of room, corridor, and
space allocation is made considering it.
1.5 Building description
Building type : Administrative Building
Structural system : Special moment resistant frame
Type of foundation : Isolated footing
No. of storied : 2 storey with basement
Floor height : 3.35 m
Plinth area : 297.85 m2
Type of sub-soil : Medium soil
22. 6
1.6 Location Plan
Figure 2: Site location
1.7 Identification of loads
Dead loads are calculated as per IS 875 (Part 1) -1987
Seismic load according to IS 1893 (Part 1)-2002 considering job site in Dharan located
at Zone-V.
Imposed loads according to IS 875(Part 2)-1987 have been taken.
23. 7
1.8 Method of Analysis
The building is modeled as a frame structure. SAP 2000 is adopted as the basic tool for
the execution of the analysis. SAP 2000 program is based on finite Element Method.
Due to possible actions in the building, the stress, displacements and fundamental time
periods are obtained using SAP 2000 which are used for the design of the members.
Isolated footing, staircase, slabs are analyzed separately.
1.9 Design
The following materials are adopted for the design of the elements:
Concrete grade M20 for beam,column and slab
Reinforcement steel-Fe415 for slab, foundation, staircase, ties and shear
reinforcement and Fe500 for beam and column.
Limit state method is used for the design of RC elements. The design is based on
IS: 456 2000, SP-16, IS: 1893-2002, SP-34 and reinforced concrete designer’s
handbook are extensively used in the process of design.
1.10 Detailing
Structural frame is considered as a special moment resisting frame (SMRF) with a
special detailing to provide the ductile behavior and comply with the requirements
given in, IS 13920-1993, Handbook on concrete reinforcement and detailing (SP34) are
extensively used.
1.11 Code of Practices
Following codes of practices developed by Bureau of Indian Standards were followed in
the analysis and design of building:
IS 456:2000 (Code of practice for plain and reinforced concrete)
IS 1893 (part 1):2002 (Criteria for earthquake resistant design of structures)
24. 8
IS 13920: 1993 (Code of practice for ductile detailing of reinforced concrete
structures subjected to seismic forces)
IS 875 (part 1):1987 (to assess dead loads)
IS 875 (part 2):1987 (to assess live loads)
IS 875 (part 5):1987 (for load combinations)
SP 16 and SP 34 (design aids and hands book for detailing)
1.12 Idealization and Assumption in Analysis and Design
Various assumptions have been made in analysis and design of the structures, for
consideration of simplicity and economy, viz.:
Tensile strength of concrete is ignored.
Shrinkage and temperature strength are negligible.
Adhesion between concrete and steel is adequate to develop full strength.
Centerlines of beams, columns and shear walls are concurrent everywhere.
26. 10
2.1 Introduction
This section of report deals mainly with following procedures:
a) Structural consideration
b) Structural arrangement plan
c) Preliminary sizing of member
d) Structural loading and assessment
e) Preliminary analysis of the structural members using appropriate method of
analysis of gravity and lateral loads
f) Verification of sizes/sections of members established based on the moments and
forces resulting from preliminary analysis.
2.2 Structural Consideration
Structure should be designed such that it can withstand each and every force that is
likely to occur. It is of paramount importance that the structural form is sound. The
architect achieves the structural configuration and the structural engineer proportions
the member sizes. There are certain principles to be borne in mind. Stating briefly the
structure should:
a) Be simple
b) Be symmetrical
c) Not to be too elongated in plan or elevation
d) Have uniform and continuous distribution of strength
e) Have horizontal members, which form hinges before the vertical members
f) Have its stiffness related to the subsoil properties
27. 11
2.3 Structural Arrangement Plan
This involve determination of the form of the structure, the material for the same, the
structural system, the layout of its components, the method of analysis, and the
philosophy of structural design.
The positioning of column, staircases, toilets, etc. is appropriate done and accordingly
beam arrangement is carried out so that the whole building will be aesthetically,
economically and functionally feasible.
The principle elements of a R.C.C. building frame are as follows:
a) Slabs to cover a large area
b) Beam should support the slabs and the walls
c) Columns to support beams and
d) Footing to distribute concentrated loads over a large area of supporting soil.
After making an architectural plan of the building, the structural planning of the
building frame is done. This involves determination of the following:
a) Column position
b) Beam locations
c) Spanning of slabs
d) Layout and planning of stair
e) Selection of the type of footing
The analysis of the building was done by the estimation of dimensions of various
structural members such as slab, beam, column, staircase with the help of preliminary
design. The different types of loads such as vertical load (dead + live and finishes) and
lateral load (earthquake) were calculated.
Earthquake being pre-dominant, only its effects was taken for lateral loads. Also,
combinations of such loads were taken into consideration. With the help of
SAP2000v14.1, element stresses of beams and columns were calculated.
28. 12
2.4 Structural Loading
The building frames are designed for dead loads, live loads and earthquake loads.
2.4.1 Dead load
Dead load is produced by self-weight of slabs, beams, columns, walls, parapet walls,
staircases, and so on.
Dead load from slab is transferred as trapezoidal and triangular loads on beams.
Dead load from slab is transferred as uniformly distributed load on beams.
Self-weight of beam is considered as uniformly distributed load.
Self-weight of column is considered as the point load acting on the joint.
2.4.2 Live load
The magnitude of live load depends upon the type of occupancy of the building. These
are to be chosen from code IS875:1987(part II) for various occupancies. The live load
distribution varies with time. Hence each member is designed for worst combination of
dead load and live loads. A reduction in live load is allowed for a beam if it carries load
from an area greater than 50m2
. The reduction is 5% for each 50m2
subjected to
maximum reduction of 25%.
Similarly all the floors of a residential or an office building may not be loaded
simultaneously. Therefore, the code permits reduction in live loads in design of
columns, walls and foundations as specified below:
Table 1: Reducion of live load in stories.
Storey below the top most level Reduction,% of live load
First 0
Second 10
Third 20
Fourth 30
Fifth and sixth 40
Over sixth 50
Since we are designing the multistoried Administrative building, live load intensity is
taken as per IS 875:1987(part II).
29. 13
2.4.3 Earthquake load
Earthquake or seismic load on a structure depends on the side of the structure,
maximum earthquake intensity or string ground motion and the local soil, the stiffness
design and construction pattern, and its orientation in relation to the incident seismic
waves. Building experiences the horizontal distortion when subjected to earthquake
motion so building should be designed with lateral force resisting system. For design
purpose, the resultant effects are usually represented by the horizontal and vertical
seismic coefficient αh & αv. Alternatively, the dynamic analysis of the building is
required under the action of the specified ground motion or design response spectra.
Since the probable maximum earthquake occurrences are not so frequent, buildings are
designed for such earthquakes so as to ensure that they remain elastic and damage-free.
Instead, reliance is placed on kinetic energy dissipation in the structure through plastic
deformation of elements and joints. The design forces are reduced accordingly. Thus,
the main philosophy of seismic designs is to reduce collapse of structure rather than a
damage free structure.
Method of seismic analysis:
There are basically two methods to determine the earthquake force in the building.
a) Seismic Coefficient Method or Static Method
b) Response Spectrum Method or Modal Analysis Method or Spectral Acceleration
or Dynamic Method
c) Time History Analysis
a) Seismic coefficient method:
The seismic coefficient method is generally applicable to building up to 40m in height
and those are more or less symmetrical in plan and elevation.
A building may be modeled as a series of 2D plane frames in two orthogonal directions.
Each node will have three degree of freedom: two translations and one rotation.
Alternatively, a building modeled as a 3D space frame. Each node will have six degrees
of freedom: three translations and three rotations, the wind loads and earthquake loads
are assumed not to act simultaneously. A building is designed for the worst of the two
30. 14
loads. The fact that the design forces for the wind are greater than the seismic design
forces does not obviate the need for seismic detailing.
b) Response Spectrum Analysis
This method is applicable for those structures where modes other than the fundamental
one affect significantly the response of the structure. In this method the response of
MULTI DEGREE OF FREEDOM (MDOF) system is expressed as the superposition of
model response, each modal response being determined from spectral analysis of
SINGLE DEGREE OF FREEDOM (SDOF) system, which is then combined to
compute the total response. Modal analysis leads to the response history of the structure
to a specified ground motion.
2.4.4 Other loads
Other loads such as earth pressure, surcharge pressure and uplift pressure if exists are
also loaded.
2.5 Preliminary Design
Preliminary sizes of the flexural members of the structural system i.e. slab and beams
are worked out as per the limit state of serviceability (deflection) consideration by
conforming to IS456:2000 CL.23.2.1. Similarly, for the compression member, i.e.
columns, the cross sectional area of the column is worked out from the net vertical axial
load on the column lying in the ground floor assuming suitable percentage of steel. The
net vertical axial load on each column is worked out from the factored dead load and
live load on the contributing area, which is taken as half of the slab areas adjacent to the
column under consideration. The load is increased by 25% for the earthquake load to
give the net vertical load.
31. 15
2.5.1) Preliminary design of slab
For two way slab
Slab ID: 1S4 (i)
From deflection criteria
We have,
xl
d (IS 456-2000 Cl. 23.2)
where, (Cl. 23.2.1)
α=32 (for continuous) (a)
β=1 (for span less than 10m) (b)
γ= 1.2 (c)
δ= 1(for no compression steel) (d)
λ=1 (for no web) (e)
And, C/C length = 5 m, Clear span (L) = 4.62 m
1*1*2.1*1*32
3354
d = 90mm
Adopt Effective Depth (d) = 105 mm
Overall Depth (D) = 105+25 mm, D = 130mm
2.5.2) Preliminary design of beam
Beam D12:
From deflection criteria
For limit state of serviceability factor.
We have,
depth
span
Where, α β γ δ λ are modification factor.
32. 16
Here longest c/c span = 6.15m
1510to
depth
span
Take 15
15/6150depth = 410 mm
Adopt Depth (D) = 450mm; 40 mm clear cover
Assume D/B = 1.667
Width (B) = 273.33mm
Adopt Width (B) = 300mm;
Secondary beam :-
l/15 = 3.84/15= 256 mm,
take 260 mm, d’
=40 mm
D=300 mm
B/D=2/3
B= 2/3 x 300 = 200 mm
Hence, size of beam = 300 mm x 200 mm
2.5.3) Preliminary design of column
Load influencing area = (18’6”x20’4”)/4 + (9’10”x18’6”)/4 + (12’7”x9’10”)/4 +
(12’7”x20’4”)/4
= 234.34 ft2
= 21.77 m2
Roof:-
LL = 1.5x21.77 = 32.66 KN
33. 17
DL(slab) = 25x0.2x21.77 = 108.85 KN
DL(beam) = 25x.55x.25x9.33 = 32.07 KN
FF=2x81.77 = 43.54 KN
TOTAL = 217.12 KN
Floors(1st
floor+ ground floor) :-
Slab= 108.85 KN
Beam = 32.07 KN
FF= 1.4x21.77 = 30.48 KN
LL= 3x21.77= 65.31 KN
Partition wall = 9.33x20x.127x3 = 71.09 KN
TOTAL = 242.49 KN + LL = 307.8 KN
Total load on basement column = roof load+1st
and ground floor+columns x 3
= 217.12+307.8x2+3x10.5 (assuming 3.5 KN/m
self wt. of column)
= 864.22 KN
Considering 30% for eq load and 1.5 as load factor
= 864.22x1.5x1.3
= 1685.23 KN
Now we have,
Pu = 0.4 fck Ac + 0.67fyAsc
Assuming Asc = 0.02 Ag (assuming 2% steel)
Ac = 0.98 Ag
Or, 1685.23x103
= .4X20X.98Ag + .67x415x.02Ag
Therefore Ag = 125754.05 mm2
Therefore required section = 380 mm x 380 mm
34. 18
2.5.4) Preliminary design of staircase
The purpose of staircase is to provide pedestrian access between two vertical floors of a
building. The geometrical forms of staircase may be different depending upon the
requirement.
In our case there is one type of staircase, open well staircase. In this case the stair is
spanning longitudinally in which, supports to the stair are provided parallel to the riser
at the top and bottom of the stair.
Stair slabs are generally designed to resist dead load, live load. Design of stair case can
be carried out according to IS: 456:2000 by considering effective length, distribution of
loading and depth of section.
Dimension of staircase
a. Type = open well
b. Width = 5’
c. Tread = 11”
d. Riser = 6”
e. Steps = 19 steps
f. Waist slab = 160 mm
2.5.5) Load calculation
Wall load :-
Type 1 = .254x(3.35-.55)x20 KN/m
= 11.38 KN/m , 20 % reduction
Type 2 = 7.11 KN/m
Paraphet wall = 20x.130x1 = 2.6 KN/m
Reduction = 20 % FOR wall opening
Roof terrace water proofing = 1.5 KN/m2
Floor finish = 0.5 KN/m2
35. 19
Floor finish for floors = 1.5 KN/m2
Dead load for slab = 25 x thickness
= 25 x .130
= 3.25 KN/m2
1. Roof
Dead load = 3.25+1.5+.5
= 4.25 KN/m2
Live load = 1.5 KN/m2
2. Floors
Dead load = 4.75 KN/m2
Live load = 3 KN/m2
Table 7: Load Intensity Assignment As per IS Code
Room Name
Load (
KN/m2
)
Room Name
Load (
KN/m2
)
Conference Room 4 Store room 5
Staff room 2.5 Meeting Room 4
Rooms for general use
with separate storage
2.5
Rooms for general use
with separate storage
4
Bath and toilet rooms 2 Circulation area 4
Campus Chief room 2.5 Exam Section 3.5
Work copy area 3.5 Passage 4
Stair Case 4 Roof 1.5
2.6) Mass lumping
Measurement Data
1. Number of column
a) Supporting first floor = 26
b) Supporting second floor = 26
c) Supporting roof = 26
2. Length of beam
36. 20
a) First floor = 181.83 m
(Along with projection up to slab projection and subtraction of
intersection of beams at joints)
b) Second floor = 181.83 m
(Along with projection up to slab projection and subtraction of
intersection of beams at joints)
c) Roof = 181.83 m
(Along with projection up to slab projection and subtraction of
intersection of beams at joints)
d) Roof top = 181.83 m
(Along with projection up to slab projection and subtraction of
intersection of beams at joints)
3. Length of wall
10” wall
a. 1st
floor = 67.57 m (opening)+21.43 m (non opening)
b. Ground floor = 62.55 m (opening)+29.06 m (non opening)
c. Basement = 85.65 m (non opening)
5” wall
a. 1st
floor = 61.14 m
b. Ground floor = 74.83 m
Load :-
1. slab
Ground floor :-
Area = 265.23 m2
Dead load = 25x265.23x0.13 = 862 KN
1st
floor :-
Area = 281.68 m2
Dead load = 25x281.68x0.13 = 915.46 KN
Roof :-
37. 21
Dead load = DL of roof + roof top load
= 862+311.04
= 1173.04 KN
2. Beams
Total length of beam = 181.83 m
Mass = 181.83x0.45x0.3x25 KN
= 613.69 KN
3. Column
No. of column in each floor = 26
Load = 26x25x0.462
x3.35 = 460.76 KN
4. Wall/partition wall
10” wall
1st
floor = 67.57 m (opening)+21.43 m (non opening)
Ground floor = 62.55 m (opening)+29.06 m (non opening)
Basement = 85.65 m
Load = (67.57+62.55)x11.38+(21.43+29.06)x14.22+85.65x14.22 = 3416.67 KN
5” wall
1st
floor = 61.14 m
Ground floor = 74.83 m
Load = (61.14+74.83)x7.22 = 981.703 KN
5. Roof top
Slab = 19.02x25x0.130 = 61.82 KN
Wall = 17.53x14.22 = 249.22 KN
Total = 311.04 KN
6. Staircase
Of each floor = 13.66x1.524x2x2+11.22x1.524x2 = 117.47 KN
Parapet wall(length) = 266.5’ = 81.23 m
Parapet wall(load) = 81.23x2.6 = 211.2 KN
Live load :-
Roof = (265.23x1.5) KN = 397.85 KN
38. 22
1st
floor = 265.23x3 = 795.69 KN
Ground floor = 265.23x3 = 795.69 KN
Table 9: Mass Lumping
Member Roof First floor Ground
Slab 1173.04 915.46 862
Beam 613.69 613.69 613.69
Column load 230.38 460.76 460.76
Walls 536.84+217.35 536.84+217.35 562.53+266.02
Staircase 58.74 117.47 117.47
Roof top 311.04 - -
Parapet wall 211.2 - -
Total dead load 3352.28 3690.12 3491.59
2.7) Assessment of lateral loads
It is the load acting horizontally in accordance with storey masses of building. Seismic
weight is the total dead load plus appropriate amount of specified imposed load. While
computing the seismic load weight of each floor, the weight of column and wall in any
storey shall be equally distributed to the floor above and below the storey. The seismic
weight of the whole building is the sum of the seismic weight of all the floors. It has
been calculated according to IS: 1893-(part I)-2002.
IS: 1893-(part I)-2002 states that for the calculation of the design seismic forces of the
structure, the imposed load on the roof need not be considered.
The wind load and earthquake load are assumed not to act simultaneously. A building is
design for the worse condition of the two loads. In our case, earthquake forces govern
lateral load. Thus assignment of lateral load is carried out according to IS: 1893-(part I)-
2002. There are basically two methods to determine the earth quake force in the
building:
39. 23
a) Seismic Coefficient Method or Static Method
b) Response Spectrum Method or Modal Analysis or Spectral Acceleration Method
or Dynamic Method
c) Time History Method
The seismic coefficient method is generally applicable to building up to 40m height and
those are more or less symmetrical in plan and elevation. This method basically consists
of calculation of base shear VB the base shear VB is given by the following equation:
WAV hB
g
S
R
IZ
A a
h **
2
Where, 1
R
I
Where,
Ah = Horizontal seismic coefficient value
Z = Zone factor for max considered earthquake condition given in IS: 1893
(Part-I) 2002 clause 6.4.2, Table-2
R = Response reduction factor given in IS: 1893 (part I) 2002 clause
6.4.2, Table-7
g
Sa
= Spectral acceleration depending upon the period of vibration and
damping as given in IS: 1893-(part I)-2002. Clause 6.4.2, Figure -2
I = Post – disaster importance factor depending on the life and function of
structure, historical value or economic importance as IS: 1893 (part I)
2002, Table-6
W = Seismic weight which includes
a) Floor wise dead load consisting of weight of floor, beams,
parapet, fixed permanent equipment and half the walls and
column etc. above and below
40. 24
b) Reduce live load on the building (25% of live load for
LL ≤ 3.0KN/m2
and 50% of LL > 3.0 KN/m2
)
T = Estimates natural or fundamental period of vibration of the building in
Second
= 0.075xH0.75
, for moment resisting concrete building
= 2/1
09.0
sD
H , for braced concrete building
H = Total height of building in m in a direction perpendicular to the applied
earthquake force.
Ds = Dimension of building in m in a direction parallel to the applied
earthquake force.
After calculating the base shear VB the distribution of earthquake force on different
floor is determined as follows:
Bn
i
ii
ii
V
hW
hW
Qi *
1
2
2
Where;
Qi = Horizontal force acting at any floor i
Wi = Weight of ithstorey assumed to be lumped at ith floor
Hi = Height if ith floor above base of frame
n = Number of storey of the building
Once the floor loads are obtained the frame can be analyzed by Portal or Cantilever
Method or Stiffness Matrix Method.
41. 25
The design storey shear in any storey is distributed to the various element of the vertical
lateral force resisting system in proportion to their rigidity considering the rigidity of
diaphragm.
For X-direction For Y-direction
Z (zonal factor) = 0.36 (v-severe)[IS 1893 (part
I): clause 6.4.2: Table-2]
I (Importance factor) = 1.5[IS 1893 (part I):
clause 6.4.2: Table-6]
R (Response reduction factor) = 5 [IS 1893
(part I): clause 6.4.2: Table-7]
Z (zonal factor) = 0.36 (v-severe) [IS 1893
(part I): clause 6.4.2: Table-2]
I (Importance factor) = 1.5[IS 1893 (part I):
clause 6.4.2: Table-6
R (Response reduction factor) = 5[IS 1893
(part I): clause 6.4.2: Table-7]
Ta=0.075*H0.75
Where,
H=height of building
Ta=0.075*10.050.75
Therefore,
Ta= 0.42
For medium soil sites (cl-6.4.5)
0.55≤Ta≤1.0
5.2
g
Sa
Ta=0.075*H0.75
Where,
H=height of building
Ta = 0.075*10.050.75
Therefore,
Ta= 0.42
For medium soil sites (cl-6.4.5)
0.55≤Ta≤1.0
5.2
g
Sa
Since, all parameters (Z, I, R, g
Sa
) are equal for both X and Y direction, the Base Shear (VB) and
Design Lateral force at floor (Qi) are also same for both direction.
Thus,
g
S
R
IZ
A a
h **
2
Where, Ah = Design horizontal seismic coefficient. [Cl-6.4.2]
44. 28
3.1) Analysis of building
Earthquake resistance design of a structure is done in order to provide the structure with the
appropriate dynamic and structural characteristics so that the structure would response to an
acceptable level without failure during an earthquake. The design is aimed in achieving of
acceptable probability of the structure of performing well during its intended life period.
Designed with appropriate degree of safety, the structure should withstand al the loads and
deformation from its normal construction and during its use. They should possess adequate
durability and resistance to misuse and fire.
For the purpose of seismic analysis, we used the structure analysis program SAP2000. In
Sap2000, we modeled the structure as rigid floor diaphragm system. A floor diaphragm is
modeled as a rigid horizontal plane parallel to global X-Y plane so that all points of any floor
diaphragm cannot displace to each other in X-Y plane.
In SAP2000, we have done 3D analysis and receives load in trapezoidal form. Earthquake
load is calculated as per seismic coefficient design using code IS 1893:2002.
Figure 4: Modeling of Administrative building
45. 29
3.2) Beam and Column number
Beams:
There are total 150 numbers of beams of 450*300 mm
Columns:
There are 78 numbers of columns in the structure. The floor-floor height
is 3.65m, and the size of column is 380*380 mm
Materials used for construction and different loads applied are well
defined to run the program. Also the load combinations are also entered
for the program.
3.3) Load cases and combinations
Altogether four loads are considered here for structural analysis and they are:
i. Dead load (DL)
ii. Live load (LL)
iii. Earthquake load (EQx)
iv. Earthquake load (EQy)
Different load cases were made and combinations of different loads to obtain the most
critical element stress in structural course of analysis.
For beam elements, following load combinations were adopted:
i. 1.5(DL + LL)
ii. 1.2(DL + LL + EQx)
iii. 1.2(DL + LL - EQx)
iv. 1.2(DL + LL + EQy)
v. 1.2(DL + LL - EQy)
vi. 1.5(DL + EQx)
vii. 1.5(DL - EQx)
46. 30
viii. 1.5(DL + EQy)
ix. 1.5(DL – EQy)
x. 0.9DL + 1.5EQx
xi. 0.9DL - 1.5EQx
xii. 0.9DL + 1.5EQy
xiii. 0.9DL - 1.5EQy
The loads to be used to determine the size of foundation should be the service loads and
not to be factored loads. The loads to be used are:
i. Dead load + Live load
ii. Dead load + Earthquake load
ii. Dead load + Live load + Earthquake load
3.4) Calculation of Storey Drift
Roof 29.23 7.80 13.41 OK
First Floor 21.43 11.67 13.41 OK
Ground Floor 9.76 9.76 13.41 OK
Roof 29.23 7.80 13.41 OK
First Floor 21.43 11.67 13.41 OK
Ground Floor 9.76 9.76 13.41 OK
Roof 29.23 7.80 13.41 OK
First Floor 21.43 11.67 13.41 OK
Ground Floor 9.76 9.76 13.41 OK
Roof 29.23 7.80 13.41 OK
First Floor 21.43 11.67 13.41 OK
Ground Floor 9.76 9.76 13.41 OK
Frame 4-A-D
Frame 3-A-D
Frame 2-A-D
Frame 1-A-D
Storey Drift Calculation
Floor Storey Drift(Vi) ∆Vi
Permissible
Value
Remarks
47. 31
Roof 32.25 8.67 13.41 OK
First Floor 23.58 12.91 13.41 OK
Ground Floor 10.67 10.67 13.41 OK
Roof 31.41 8.43 13.41 OK
First Floor 22.98 12.57 13.41 OK
Ground Floor 10.41 10.41 13.41 OK
Roof 30.53 8.18 13.41 OK
First Floor 22.35 12.20 13.41 OK
Ground Floor 10.15 10.15 13.41 OK
Roof 29.23 7.80 13.41 OK
First Floor 21.43 11.67 13.41 OK
Ground Floor 9.76 9.76 13.41 OK
Roof 29.23 7.80 13.41 OK
First Floor 21.43 11.67 13.41 OK
Ground Floor 9.76 9.76 13.41 OK
Roof 29.23 7.80 13.41 OK
First Floor 21.43 11.67 13.41 OK
Ground Floor 9.76 9.76 13.41 OK
Roof 29.23 7.80 13.41 OK
First Floor 21.43 11.67 13.41 OK
Ground Floor 9.76 9.76 13.41 OK
Frame 5-A-D
Storey Drift Calculation
Floor
Permissible
Value
∆ViStorey Drift(Vi) Remarks
Frame D-1-7
Frame C-1-7
Frame B-1-7
Frame A-1-7
7-A-D
6-A-D
49. 33
4.1) Design of Slab
Slab is rigid plate which acts as roof or floor during the construction of building in
which all the points are equally displaced when the load is applied on a point on a slab.
Slab is a flexural element and there are mainly two types of slab based on the ratio of
longer to shorter span of room. They are as follow:
i. One way slab: It is a slab with the ratio of longer to shorter span greater than 2
and the coefficient for it can be used from Table 26.b (IS 456:2000).
ii. Two way slab: It is the slab with the ratio of longer to shorter span less than or
equal to 2 and the coefficient for it can be used from table 26.a (IS 456:2000).
There are ten types of two way continuous slab depending upon the length and the
discontinuous edge. The conditions to be satisfied for use of these conditions are
a) The loading of the adjacent span should be the same.
b) The span in each direction should be approximately equal.
The span moment per unit width (which are considered as positive in sign) and the
negative moments at continuous edge for these slabs are calculated from the equation:
Mx=αxwlx
2
from span lx
My=αywlx
2
from span ly
Spacing of bars on slab:
i. Maximum spacing in main bar:
a) 3 times the effective depth
b) 300 mm, whichever is less
ii. Maximum spacing in distribution bars
a) 5 times the effective depth
b) 450 mm, whichever is less
Reinforcement requirement in slab:
i. Maximum reinforcement:
Astmax = 4% of area of slab
ii. Minimum reinforcement:
Astmin = 0.12% of area of slab
50. 34
Flow chart of slab design:
Determine factored load W=1.5(DL+LL)
WD=1.5DL, WL= 1.5LL
Determine ratio ly/lx
NO
If ly/lx < 2 One way slab
Yes
Two way slab IS code 456-2000, table 12 Determine moment coefficients
Determine type of panel
E.g. two adjacent cont. edge Calculate moment at mid, edge
M = MD+ML
Determine moment coefficients, MD = αDwlx
2
, ML = αLwlx
2
IS code 456, Table 26, e.g. long, short span,
Edge, mid
Calculate
2
xuxx lWM
2
xuyy lWM
Ast>Ast min
Calculate area of steel Ast= 0.12% bD
M = 0.87*fy*Ast(d – fyAst/fck*b)
Sv< 300 mm
Determine spacing of bars or 3d
51. 35
Design of slab (Two edges dis-continuous)
Slab ID = 10
ly (long span)= 4.85
lx (short span)= 3.84 226.1
84.3
85..4
x
y
l
l
Hence, two way slab
Thickness of slab:
Overall depth (D) = 130 mm
Dia. Bar used (ɸ) = 8 mm
Clear cover = 20 mm
Effective depth (d) = 150-20-10/2 = 110 mm
Design load:
Factored load (Wu) = 1.5* 8.75KN/m2
(Wu) = 13.13 KN/m2
Bending Moment:
Bending Moment Coefficient:
We have,
In x-direction
Mux (-ve) =0.052*13.13*3.842
= 9.91 KNm
Mux (+ve) =0.039*13.13*3.842
=-7.65 KNm
In Y-direction
αx-= 0.052 αy-= 0.037
αx+= 0.039 αy+=0.028
52. 36
Muy (-ve) =0.037*13.13*3.842
=6.43KNm
Muy (+ve) =-0.028*13.13*3.842
=-4.87KNm
Check for effective depth for Max. Bending moment:
For fy= 415Mpa &fck=25Mpa
Mmax
9.91*10^6 =0.138*fck*b*d2
*10^6 = 0.138*20*1000*d2
d =71.02 mm < 105 mm (Hence, safe)
Adopt d=105mm
So, D =130mm
Area for steel reinforcement
For long span (y- direction)
dbf
Af
dAfM
ck
sty
styux
**
*
1****87.0
105*1000*20
*415
1*125**415*87.010*91.9 6 st
st
A
A
By solving, we get
Astx-= 175.71 mm2
>Ast minimum(156 mm2
)
Check for spacing:
Us 8 mm ɸ bar for longer direction.
53. 37
Spacing (S) = 1000*area of one bar/Astx =1000 * 50.26/15.71 =286 mm
Adopt spacing (S) = 280 mm < (3*125=375 or 300mm, whichever is small)
Area provided, Ast =
280
4
8
*1000
2
= 179.5 mm2
Check for minimum percentage of steel:
130*1000
100
*5.179
*
100
*% ,
Db
Ap providedst
= 0.14%> 0.12% (OK) (IS: 456-2000, Clause 26.5.2.1)
Hence, Use 8 mm ɸ bar @ 280 mm c/c
For long span (y- direction): for support
dbf
Af
dAfM
ck
sty
styux
**
*
1****87.0
105*1000*20
*415
1*105**415*87.010*65.7 6 st
st
A
A
By solving, we get
Astx+= 218.5 mm2
>Ast min
Check for spacing:
Use 8mm ɸ bar for shorter direction.
Spacing (S) = 1000*area of one bar/Astx =
5.218
4
8
*1000
2
=230 mm
Adopt spacing (S) = 230 mm (3*125=375 or 300mm, whichever is small)
Area provided, Astx- =
300
4
10
*1000
2
= 218.5 mm2
Check for minimum percentage of steel:
54. 38
130*1000
100
*5.218
*
100
*% ,
Db
Ap providedst
= 0.17 % > 0.12% (OK) (IS: 456-2000, Clause 26.5.2.1)
Hence, Use 8 mm ɸ bar @ 230 mm c/c
For long span (X- direction): for support
dbf
Af
dAfM
ck
sty
styuy
**
*
1****87.0
105*1000*20
*415
1*105**415*87.010*43.6 6 st
st
A
A
By solving, we get
Asty-= 175.71mm2>Ast minimum
Check for spacing:
Use 8 mm ɸ bar for longer direction.
Spacing (S) = 1000*area of one bar/Ast,x =
71.175
4
8
*1000
2
=286 mm
Adopt spacing (S) =280 mm (3*125=300 or 300mm, whichever is small)
Area provided, Ast =
280
4
8
*1000
2
= 179.5 mm2
Check for minimum percentage of steel:
130*1000
100
*5.179
*
100
*% ,
Db
Ap providedst
= 0.14% > 0.12% (OK) (IS: 456-2000, Clause 26.5.2.1)
Hence, Use 8 mm ɸ bar @ 280 mm c/c
For long span (X- direction): For mid span
55. 39
dbf
Af
dAfM
ck
sty
styuy
**
*
1****87.0
By solving, we get
Asty+= 131.90mm2
<Ast minimum
Check for spacing
Use 8 mm ɸ bar for longer direction.
Spacing (S) = 1000*area of one bar/Ast,x =
9.131
4
10
*1000
2
= 384 mm
Adopt spacing (S) = 300 mm (3*125=375 or 300mm, whichever is small)
Area provided, Ast =
300
4
8
*1000
2
= 168 mm2
Check for minimum percentage of steel
130*1000
100
*168
*
100
*% ,
Db
Ap providedst
= 0.13 % > 0.12% (OK) (IS: 456-2000, Clause 26.5.2.1)
Hence, Use 8 mm ɸ bar @ 300 mm c/c
Check for deflection
(l/d)provided=3.84*1000/125=30.72
fs=0.58fy (area of steel required / area of steel provided)
fs=0.58*415 (130 / 156) = 200.58 N/mm2
(l/d)max= (l/d)basic*kt*kf*kc=30.72*1.5*1*1=46.08>(l/d)provided ( OK)
105*1000*20
*415
1*105**415*87.010*87.4 6 st
st
A
A
56. 40
Hence, it is safe in deflection
Check for shear force
Maximum shear force:
2
* xu lW
V
KNV 78.23
2
8.4*91.9
Nominal shear stress: 2
/23.0
105*1000
1000*78.23
mmN
bd
V
v
Percentage of tensile stress= %17.0100
105*1000
5.179
100 xx
bd
A
p st
t
Shear strength for M20 concrete for 0.17% steel,
Mpac 19.0
Shear strength in slab, kcc '
For D = 150mm, k=1.3
2'
/25.03.1*19.0 mmNc (IS: 456-2000, clause 40.2, Table 19)
2'
/23.025.0. mmNeivc Hence, safe.
No shear reinforcement is required.
Check for Development length
M1 at support
Moment of resistance offered by 8 mm ɸ bars @ 180 mm c/c.
dbf
Af
dAfM
ck
sty
styx
**
*
1****87.0,1
105*1000*20
5.276*415
1*125*5.276*415*87.0
= 11.79*10^6 N-mm.
Development length of bar:
57. 41
bd
s
DL
*4
*
(IS: 456-2000, clause 26.2.1)
6.1*2.1*4
415*87.0*8
DL
mmLD 1.376
Lo = 12ɸ or d, whichever is greater. i.e., 120mm or 125mm
Lo = 125 mm
oD L
V
M
xL 1
3.1 (IS: 456-2000, clause 26.2.3.3)
Hence, safe in development length
58. 42
4.1.1) Slab reinforcement :-
FIRST FLOOR
Note: Moment is in KNm and Spacing is in
mm.
Detailling in Slabs
Slab Type
Mux Muy
Spacing (along X
direction)
Spacing(along Y
direction)
Torsional Reinforcement at
corners
Length
on
Spacing
at
Spacing at
(-ve) (+ve) (-ve) (+ve)
At
Support
At Mid
span
At
support
At Mid
Span
both axis
cont.
edge
discont.
Edge
67 Two adjacent edge discont. 4.87 3.63 4.27 3.18 300 300 300 300 560 440 220
68 one long edge discont. 4.00 3.00 3.36 2.54 300 300 300 300 560 440
69 Two adjacent edge discont. 3.71 2.80 3.29 2.45 300 300 300 300 560 440 220
70 Two adjacent edge discont. 3.71 2.80 3.29 2.45 300 300 300 300 560 440 220
71 one long edge discont. 4.72 3.54 3.36 2.54 300 300 300 300 560 440
72 Two adjacent edge discont. 5.45 4.09 4.27 3.18 300 300 300 300 560 440 220
76 one short edge discont. 3.91 2.91 3.37 2.54 300 300 300 300 560 440
77 Interior Panel 3.36 2.54 2.91 2.18 300 300 300 300
78 one short edge discont. 3.01 2.24 2.59 1.96 300 300 300 300 560 440
35 one long edge discont. 2.86 2.18 0.86 0.65 300 300 300 300
79 one short edge discont. 3.01 2.24 2.59 1.96 300 300 300 300 560 440
80 Interior Panel 3.91 2.91 2.91 2.18 300 300 300 300
81 one short edge discont. 4.36 3.27 3.37 2.54 300 300 300 300 560 440
73 one long edge discont. 6.21 4.79 4.03 3.05 280 300 300 300 610 480
59. 43
74 Interior Panel 4.85 3.61 3.61 2.71 280 300 300 300
11 Interior Panel 4.04 3.09 2.75 2.06 280 300 300 300
10 one long edge discont. 9.91 7.65 6.43 4.87 280 300 180 230
9 Interior Panel 4.04 3.09 2.75 2.06 280 300 300 300
8 Interior Panel 3.75 2.83 3.24 2.43 280 300 300 300
7 one long edge discont. 5.51 4.13 3.92 2.97 280 300 300 300 660 520
82 Two adjacent edge discont. 6.53 4.90 5.12 3.81 280 300 300 300 610 480 240
83 Two adjacent edge discont. 6.53 4.90 5.12 3.81 280 300 300 300 610 480 240
15 Two adjacent edge discont. 5.76 4.35 5.11 3.80 280 300 300 300 670 530 265
16 Two adjacent edge discont. 5.58 4.21 4.95 3.68 280 300 300 300 670 530 265
ROOF
Detailling in Slabs
Slab Type
Mux Muy
Spacing (along X
direction)
Spacing(along Y
direction)
Torsional Reinforcement at
corners
Length
on
Spacing
at
Spacing at
(-
ve)
(+ve) (-ve) (+ve)
At
Support
At Mid
span
At
support
At Mid
Span
both axis
cont.
edge
discont.
Edge
25 Two adjacent edge discont. 3.16 2.39 2.81 2.09 300 300 300 300 560 440 220
26 one long edge discont. 2.63 1.97 2.21 1.67 300 300 300 300 560 440
45 Two adjacent edge discont. 3.16 2.39 2.81 2.09 300 300 300 300 560 440 220
46 Two adjacent edge discont. 3.16 2.39 2.81 2.09 300 300 300 300 560 440 220
63. 47
4.2) Design of Column
The column section shall be designed just above and just below the beam column joints and
larger of the two reinforcements shall be adopted. The end moments and end shear are
available from computer analysis. The design moment should include the following:
The additional moment if any, due to long column effect as per Cl.39.7 of IS 456:2000
The moments due to minimum eccentricity as per Cl.25.4 of IS 456:2000
All columns are subjected to biaxial moments and biaxial shears. The longitudinal
reinforcements are designed for axial force and biaxial moment as per IS 456:2000. Since
analysis is carried out considering center line dimension, it is necessary to calculate moments
at the top or at the bottom face of the beam intersecting the column for economy. The critical
load combination may be obtained by inspection of analysis result.
The building is symmetrical and all columns are of square section. The procedure used for
exact design of members subjected to axial load and biaxial bending is extremely laborious.
Therefore, IS 456:2000 permits the design of such members by the following equations:
(Mux 𝑀𝑢𝑥𝑙⁄ )α
+ (Muy 𝑀𝑢𝑦𝑙⁄ )α
≤1
Puz =0.45*fck*Ac + 0.75*fy*Ast
Where,
Mux = moment about X axis
Muy = moment about Y axis
Muxl = maximum uniaxial moment capacity in X axis
Muyl = maximum uniaxial moment capacity in Y axis
fck = characteristic strength of concrete
fy = characteristic strength of steel
Ac = gross X-section area of column
Ast =area of reinforcement bars
64. 48
Flow Chart of Column Design:
Select Maximum
3
2
32
MM
MM
MMM
uy
ux
u
Take corresponding axial
Load (Pu)
Calculate minimum
Eccentricity ex and ey
Calculate moment due to minimum
Eccentricity by Muxe= Pu*ey and C
Muye= Pu*ex
Take,
Mux = Max. of Mux and Muxe Calculate Pu/Puz
Muy= Max. ofMuy and Muye
Design as biaxial bending Determine n from
Table from Pu/Puz and n
Assume d’ and final ratio d’/D
If 1
11
nn
uy
uy
ux
ux
M
M
M
M
Assume suitable Asc and
Find P = Ast / (BD)
Calculate the ratios Increase Asc and find p.
Pu/(fck*BD) and p/fck
Determine Muxl, Muyl using
Appropriate chart from SP-16 C the assumed reinforcement is OK.
with ratios p/fck, d’/D and Pu/(fck*BD)
65. 49
Design of column :-
Size of column = 380 mm x 380 mm
Mux = 16.451 KNm
Muy = 171.2 KNm
Fck = 20 N/mm2
Fy = 500 N/mm2
Pa = 362.9 KN
Solution:-
Reinforcement is distributed equally on four sides
Assuming % of steel to be 2.7%
Now,
p/fck = 2.7/20 = 0.135
we have,
effective cover (d’
) = 50 mm
so, d’
/d = 50/300 = 0.1
Now,
09.0
380*380*20
1000*9.362
*
bDf
P
ck
u
Now,
Referring to chart no. 48,
19.0
* 2
bDf
M
ck
ux
Now,
Mux1 = 0.19x20x380x3802
= 204.58x106
Nmm = 204.58 KNm
Again,
66. 50
For fy = 500 N/mm2
and d’
/d = 50/380 = 0.1
19.0
* 2
bDf
M
ck
uy
Therefore, Muy1 = 204.58 KNm
Now,
Puz = 0.45*fck*Ac + 0.75*fy*Asc = 3x106
Now, Pu/Puz = (362.9x1000)/3x106
= 0.13
Now, from table Pu/Puz<0.2
So αn = 1
Now,
1
11
nn
uy
uy
ux
ux
M
M
M
M
Or, 1
58.204
2.171
58.204
451.16
11
Or, 0.91 ≤ 1
Hence, ok.
taking % of steel = 2.7%
therefore, area of steel(Ast) = (2.7/100)x380x380 = 3898.8 mm2
Now,
Taking 25 mm dia rods
A = (∏x252
)/4 = 491 mm2
No. of bars = Ast/A
=3898.8/491 = 7.94 = 8 nos
Again,
Design of lateral ties
67. 51
Diameter:- greater of
1. Shall not be less than 6 mm
2. Shall not be less than one-forth of the dia of the largest bar = 6.25 mm
Therefore, dia. Of lateral ties = 8 mm
Spacing:-
Should be lesser of
1. 300 mm
2. 16 x diameter = 400
3. Least lateral dimension = 380 mm
Therefore, pitch of lateral ties = 300 mm.
76. 60
4.3) Design of Beam
The beam is flexural member which distributes the vertical load to the column and
resists the bending moment. The design of the beam deals with the determination of the
beam section and the steel required. Here, we have considered different sizes of beams
at different points, so we have computed the steel requirement with respect to the beam
section.
For convenience, we have considered all the sections as under-reinforced ones. The
singly reinforced and doubly reinforced sections are designed as per the requirement,
i.e. comparison with the limiting moment, Mu, lim.
IS 456:2000 (Annex G, Cl.38.1) is referred for the calculation of the required steel in
the beam. For the singly reinforced section, steel is calculated by using the formula
from G.1.1.b.
Mu =0.87*fy*Ast*d*[1- Ast * fy/ (b*D*fck)]
Limiting moment of the resistance is given by the equation:
Mu, lim=0.36*Xu, max/d *(1-0.42 Xu, max /d) bd2
fck
For the section with the compression reinforcement, where the ultimate moment of
resistance of the section exceeds the limiting value Mu,lim, the compression
reinforcement may be obtained by
Mu - Mu, lim =fsc *Asc(d-d’)
Where,
Mu = ultimate moment of resistance of the section
Mu, lim =limiting moment of resistance
Xu =neutral axis depth
xu,max =limiting value of Xu
D = effective depth
D = width of the compression face
d’ = effective cover
fy = characteristic strength of the reinforcement
fck = characteristic strength of concrete
77. 61
fsc =design stress in compression reinforcement corresponding to
strainof 0.0035*( xu,max-d’)/ xu,max
Ast =area of the tension reinforcement
Asc = area of compression reinforcement
Total area of tension reinforcement in the doubly reinforced beam sections shall be
obtained by
Ast=Ast1 - Ast2,
Where,
Ast=total tension reinforcement
Ast1=area of tensile reinforcement for singly reinforced section for Mu, lim
Ast2= Asc* fsc/0.87fy
Design of beam:
Design of beam :-
Beam no. 271
Shear force(max at support) = 76.88 KN
Moment :-
Left support +ve moment = 22.09 KNm
Right support +ve moment = 9.73 KNm
Left support –ve moment = 98.98 KNm
Right support –ve moment = 105.68 KNm
Mid span moment = 74.33 KNm
Ast for maximum +ve moment :-
74.33x106
= 0.87fyAst(d-(fyAst)/(fckb))
78. 62
Therefore, Ast = 457.63 mm2
Minimum area = (0.85bd)/fy
= 209.1 mm2
(ok)
Hence, Ast= 457.63 mm2
Hence, using 2-16mm dia bars & 1-12mm dia bar
Ast,prov= 515.22 mm2
Ast for maximum –ve moment :-
105.68x106
= 0.87fyAst(d-(fyAst)/(fckb))
Therefore, Ast = 683.77 mm2
Using 2-16 mm & 2-12 mm dia. Bars
Ast,prov = 628.31 mm2
Design of shear :-
V = 76.88 KN
Τu = Vu/(bd) = (76.88x1000)/(300x410) = 0.64 N/mm2
Pt = 515.22/(300x450) = 0.4%
For pt = 0.4 %
Design shear strength of concrete (τc) = 0.432 N/mm2
Here, τu>τc. hence shear reinforcement is required.
Strength of shear reinforcement (Vus) = Vu – τcbd
= 23744 N
Adopting 8 mm – legged stirrup
Asv = 2x∏x82
/4 = 100.5 mm2
Spacing of shear reinforcement = (0.87fyAsvd)/Vus
= 626.56 mm
The code requires spacing should not be less than least of 1. 300 mm
2. 0.75d = 307.5 mm
79. 63
Hence, spacing = 300 mm
Again, spacing should not less than least of the following as per IS 13920
1. d/4 = 102.5 mm
2. 8db(db = dia of largest bar) = 8x16 = 128 mm
Hence, spacing = 100 mm
