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Thread: Analysis and design of an irregular institutional building with and without floating foundation

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    Analysis and design of an irregular institutional building with and without floating foundation

    PROJECT REPORT
    on
    ANALYSIS AND DESIGN OF AN IRREGULAR INSTITUTIONAL BUILDING WITH AND WITHOUT FLOATING FOUNDATION


    Submitted in partial fulfillment for the award of the degree

    of
    BACHELOR OF TECHNOLOGY

    in
    CIVIL ENGINEERING

    by
    ROHIT RAO 1011110219
    MANJUNATH 1011110229
    PRANAB BARUAH 1011110250


    Under the guidance of
    Ms. S.M.JAYASHREE
    (Assistant Professor (O.G.))

    DEPARTMENT OF CIVIL ENGINEERING
    FACULTY OF ENGINEERING AND TECHNOLOGY
    SRM UNIVERSITY
    (Under section 3 of UGC Act, 1956)
    SRM Nagar, Kattankulathur- 603203
    Kancheepuram District

    APRIL 2015

    PROJECT REPORT
    on
    ANALYSIS AND DESIGN OF AN IRREGULAR INSTITUTIONAL BUILDING WITH AND WITHOUT FLOATING FOUNDATION

    Submitted in partial fulfillment for the award of the degree

    of
    BACHELOR OF TECHNOLOGY

    in
    CIVIL ENGINEERING

    by
    ROHIT RAO 1011110219
    MANJUNATH 1011110229
    PRANAB BARUAH 1011110250


    Under the guidance of
    Ms. S.M.JAYASHREE
    (Assistant Professor (O.G.))

    DEPARTMENT OF CIVIL ENGINEERING
    FACULTY OF ENGINEERING AND TECHNOLOGY
    SRM UNIVERSITY
    (Under section 3 of UGC Act, 1956)
    SRM Nagar, Kattankulathur- 603203
    Kancheepuram District

    APRIL 2015
    BONAFIDE CERTIFICATE

    Certified that this project report titled “ANALYSIS AND DESIGN OF IRREGULAR INSTITUTIONAL BUILDING WITH AND WITHOUT FLOATING FOUNDATION” is the bonafide work of ROHIT RAO (1011110219), MANJUNATH (1011110229) and PRANAB BARUAH (1011110250) who carried out the project under my supervision. Certified further, that to the best of my knowledge the work reported herein does not form part of any other project report or dissertation on the basis of which a degree or award was conferred on an earlier occasion or any other candidate.

    Signature of the Guide Signature of the HOD

    Miss S.M. JAYASHREE Dr. R. ANNADURAI
    Assistant Professor Professor & Head
    Department of Civil Department of Civil
    Engineering Engineering
    SRM University SRM University
    Kattankulathur- 603203 Kattankulathur- 603203


    INTERNAL EXAMINER EXTERNAL EXAMINER


    DATE:
    ACKNOWLEDGEMENT

    We would like to place on record, our grateful thanks to Dr.T.P.GANESAN, Pro Vice Chancellor (P&D), for providing all facilities and help in carrying out this project. We thank Dr. C. MUTHAMIZHCHELVAN, Director (Engg. & Tech.) for the stimulus provided.
    We are extremely grateful to Dr. R. ANNADURAI, Professor and Head, Department of Civil Engineering for the encouragement and support provided during the project work. .
    We express our sincere thanks to the coordinators Dr. K. GUNASEKARAN and Dr. S. SENTHIL SELVAN, Professor, for their valuable suggestions for improvement during project reviews.
    We hereby acknowledge with deep sense of gratitude the valuable guidance, encouragement and suggestions given by our guide Ms. S.M.JAYASHREE, Asst. Professor (O.G.), Department of Civil Engineering, who has been a constant source of inspiration throughout this project.
    We would also like to express this grateful wishes and sincere thanks to the class in-charge Mr. S.PRADEEP, Asst. Professor (O.G.), for all the suggestions given during the course of this project.
    Also, we would like to take this opportunity to thank all the faculty members and non-teaching staff members in the Department of Civil Engineering for their direct and indirect help rendered during the course of the project work.
    We also thank the staff of SRM DTP section for their efforts in composing the project report. We record our sincere thanks to our parents for the support and motivation.
    Last, but not the least, we thank all our friends, who freely helped us in many ways towards the successful completion of this project work.

    ROHIT RAO
    MANJUNATH
    PRANAB BARUAH
    ABSTRACT

    Recent times have witnessed shortage of availability of space due to increase in uncontrolled population growth. Due to this unavailability of proper regular plots we have to adopt for irregular structures and modern construction practices.
    A trapezoidal plot has been selected for the purpose of constructing an irregular structure. The structure is irregular with re-entrant corners. For foundation, pile foundation and floating foundation have been used. The realistic constraints faced were economic, environmental and sustainability. The constraints and overcoming these design constraints are discussed in detail in the project.
    Some of the constraints, in brief, are as follows. Economic Constraints is the design of the building should be done in such a way that the estimation of the building should satisfy the client budget. Environmental Constraints is the particular site considered in this project is located in Assam which falls under seismic Zone V. So Seismic load and lateral forces will be considered while designing. Sustainability Constraints is the design of the building should be done in such a way that it withstands the most vulnerable earthquakes.
    The project shows efficient utilization of the plot size as well as new construction technique (floating foundation). The realistic design constraints were considered in providing a safe structure. For example earthquake load factor was considered while analyzing the superstructure in software. Also thickness of the members was taken as such that even safety as well as serviceability conditions were satisfied.

    TABLE OF CONTENTS

    CHAPTER TITLE PAGE
    LIST OF TABLES viii
    LIST OF FIGURES ix
    ABBREVATIONS x
    1 OVERVIEW 1
    1.1 GENERAL 1
    1.2 OBJECTIVE 1
    1.3 NECESSITY 1
    1.4 SCOPE 1
    1.5 METHODOLOGY 2
    1.6 MAJOR DESIGN EXPERIENCE 3
    1.7 REALISTIC DESIGN CONSTRAINTS 3
    1.8 REFERENCE TO CODES AND STANDARDS 3
    1.9 APPLICATION OF EARLIER COURSE WORKS 4
    1.10 SOFTWARE / EQUIPMENT USED 4
    1.11 EXPECTED OUTCOME 4
    1.12 CONCLUSION 4
    1.13 FUTURE SCOPE 4

    2 INTRODUCTION 5 2.1 GENERAL 5
    2.2 LITERATURE REVIEW 5
    2.3 SUMMARY OF LITERATURE REVIEW 7

    3 OBJECTIVES AND SCOPE 8
    3.1 GENERAL 8
    3.2 OBJECTIVE 8
    3.3 SCOPE 8
    3.4 MATERIALS AND METHODOLOGY 8
    4 RESULTS AND DISCUSSIONS 9
    4.1 GENERAL 9
    4.2 PLANNING 9
    4.2.1 BUILDING DISCRIPTION 9
    4.2.2 PLAN OF THE FLOORS 10
    4.3 ANALYSIS 15
    4.3.1 DIMENSIONS USED FOR MODELING IN SAP2000 15
    4.3.2 MODELING OF THE STRUCTURE 15
    4.3.3 ANALYSIS RESULTS OF THE CRITICAL MEMBERS 19
    4.4 DESIGNS OF STRUCTURAL MEMBERS 20
    4.4.1 DESIGN OF SLAB 20
    4.4.2 DESIGN OF BEAMS 26
    4.4.3 DESIGN OF COLUMN 29
    4.4.4 DESIGN OF PILE FOUNDATION 33
    4.4.5 DESIGN OF FLOATING FOUNDATION 36

    5 CONCLUSION 40
    REFERENCES 41

    LIST OF TABLES
    TABLE TITLE PAGE
    1.1 Reference to codes and standards 3
    1.2 Application of earlier course works 4
    4.1 Dimension of members 15
    4.2 Analysis results 19
    4.3 Dead load transferred from ground column 37

    LIST OF FIGURES
    FIGURE TITLE PAGE
    1.1 Methodology 2
    4.1 Area statement 10
    4.2 Basement plan 11
    4.3 Ground floor plan 12
    4.4 First floor plan 13
    4.5 Second floor plan 14
    4.6 General modelling of the structure 15
    4.7 Modelling with filled material 16
    4.8 Extrude view of the structure 16
    4.9 Top view of the structure 17
    4.10 Critical beam section 17
    4.11 Forces in critical section (Beam) 18
    4.12 Critical column section 18
    4.13 Forces in critical section (Column) 19
    4.14 Slab Detailing 25
    4.15 Beam Detailing 29
    4.16 Column Detailing 32
    4.17 Pile Foundation Detailing 36
    4.18 Detailing of Floating Foundation 39


    ABBREVIATIONS USED

    IS - Indian Standards
    SAP - Structural Analysis Program
    CAD - Computer Aided Drawing
    Fig. - Figure
    c/c - Center to center
    F - Force acting on the building
    fck - Characteristics compressive strength of concrete
    Lx - Length of shorter side of slab
    Ly - Length of longer side of slab
    D - Overall depth of the slab or the beam or the column
    d - Effective depth of the slab or the beam or the column
    Wu - Ultimate design load
    b - Breadth of beam
    Mu - Ultimate moment
    M - Bending moment
    Ast - Area of steel in tension
    Asc - Area of steel in compression
    Ag - Gross area
    Ac - Area of concrete
    Pu - Ultimate load on compression member
    G.C - Ground Column

















    CHAPTER 1

    OVERVIEW
    1.1 GENERAL
    In this chapter discussion about the objectives, necessity, scope, methodology to be followed, design constraints, software used, etc have been discussed in detail.
    1.2 OBJECTIVE
    • To plan an irregular structure.
    • To analyze the irregular structure.
    • To design the irregular structure with Pile Foundation.
    • To design the irregular structure with Floating Foundation.
    1.3 NECESSITY
    • When the soil is so soft that even friction piles will not support the building load, the final option is the use of a floating foundation, making the building like a boat that obeys Archimedes’ principle—it is buoyed up by the weight of the earth displaced in creating the foundation.
    • Because of the way in which they're constructed, floating foundations spread the weight of the structure over the entire base of the building rather than at scattered support spots.
    • Floating foundations are shallow, making them ideal for specific construction situations.
    1.4 SCOPE
    • Preparation of plan.
    • Analysis of superstructure.
    • Design of superstructure.
    • Design of pile foundation and floating foundation.
    1.5 METHODOLOGY
    Figure 1.1 shows the methodology followed step by step for completion of the project.
    PHASE II

    PHASE I

    PHASE II

    PHASE

    I


    Fig. 1.1 Methodology

    1.6 MAJOR DESIGN EXPERIENCE
    The project is a “Structural Design Project”. Design experience in the following areas shall be gained during the course of this project:
    Design of slab.
    Design of beam.
    Design of column.
    Design of pile foundation.
    Design of floating foundation.
    1.7 REALISTIC DESIGN CONSTRAINTS
    Economic Constraints
    The design of the building should be done in such a way that the estimation of the building should satisfy the client budget. In cases like the design of slabs, the slab thickness fixed should satisfy the deflection criteria or else the slab thickness should be increased.
    Environmental Constraints
    The particular site considered in this project is located in Assam which falls under seismic Zone V. So in addition to the dead load and live load considered, loads due to the environment should also be considered. i.e Seismic load and lateral forces will be considered while designing.
    Sustainability Constraints
    The design of the building should be done in such a way that it withstands the most vulnerable earthquakes. For that, serviceability conditions should be considered in a right manner.
    1.8 REFERENCE TO CODES AND STANDARDS
    Table 1.1 shows the Indian Standard codes used in this project.
    Table 1.1 Indian Standard used
    IS456:2000 Plain and Reinforced Concrete
    IS1893(part I):2002 Design of Earthquake Resistant Structure
    IS13920:1993 Structures subjected to seismic forces
    1.9 APPLICATION OF EARLIER COURSE WORKS
    Table 1.2 shows the earlier course work applied in the project.
    Table 1.2 Application of earlier course works
    COURSE CODE AND NAME CONTEXT
    GE0101 – Basic Engineering I Components of a room.
    CE0104 – Computer Aided Building Drawing Preparation of Plan.
    CE0201 – Mechanics of Solids Evaluation of bending moments.
    CE0202 – Strength of Materials Evaluation of Deflection.
    CE0303, CE0304 – Structural Design. Design of RCC system.
    CE0305- Soil Mechanics Soil profile
    CE0306- Foundation Engineering Foundation Details

    1.10 SOFTWARE USED
    SAP2000 Version 15.
    AutoCAD
    1.11 EXPECTED OUTCOME
    Nil settlement in the structure with floating foundation.
    Detailed comparative study made between Floating foundation and Pile foundation.
    1.12 CONCLUSION
    Plan was made in AutoCAD of an irregular structure.
    The building was modeled in SAP2000.
    Analysis and Design using software under process.
    1.13 FUTURE SCOPE
    Manual Design of superstructure will be done.
    Manual design of Floating Foundation and Pile Foundation will be done.
    Comparison between the both will be done.


    CHAPTER 2

    INTRODUCTION
    2.1 GENERAL
    In this present era land utilization has become an important factor. Plots available now days do not guarantee a perfectly regular space. So for the sake of efficient land utilization adoption of plan irregular structures should be undertaken. New construction practices have revolutionized the Civil Engineering field. The concept of Floating Foundation is one of the new construction practices that are being adopted throughout the World. The concept is based on Archimedes' principle indicates that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces. This concept is being applied to the soil. When the soil is so soft that even friction piles will not support the building load, the final option is the use of a floating foundation, making the building like a boat that obeys Archimedes’ principle—it is buoyed up by the weight of the earth displaced in creating the foundation. Because of the way in which they're constructed, floating foundations spread the weight of the structure over the entire base of the building rather than at scattered support spots. Floating foundations are shallow, making them ideal for specific construction situations. A comparison has been made in this project between pile foundation and floating foundation to understand its concepts better.
    2.2 LITERATURE REVIEW
    S. Mohsenian et al., (2011), investigated the Geotechnical Aspects for Design and Performance of Floating Foundations. From his study, he found that Floating foundations are often practical when foundations must be placed over deposits of compressible soil and when deep foundations are expensive. The aim of the paper is to study parameters affecting the behavior of floating foundations, including the kind of floating foundations, depth of excavation, and imposed pressure by the superstructure. Herein, 3 buildings ranging from 15 to 25 stories with gross foundation pressures from 195Kpa to 342Kpa are studied for 4 soil types ranging from very soft to strong type. The basic purpose of the paper is to study the settlement variation amongst different soil profiles. Problems of design and construction of floating foundation consists of excavation, water lowering, bottom heave, settlement and structure problems. It was concluded that increasing the excavation depth decreases the amount of maximum settlement because of reducing the net pressure on the sub-soil. (Ref. - Geo-Frontiers 2011: Advances in Geotechnical Engineering (edited by Jie Han, Daniel E. Alzamora), Geo-technical aspects for Design and Performance of Floating Foundations, Page: 56-65 )
    Kolios et al., (2010), did a study and published a journal on Reliability of floating foundation concepts for vertical axis wind turbines. Offshore wind turbines are developing at a rapid pace. They are designed to resist both functional and site specific wind, wave and seismic forces. By far the most common turbine configuration is the HAWT (Horizontal Axis Wind Turbine) and development of these machines is largely centered about drive train and blade issues with some work concerning foundations/supporting structures. Several teams around the world are developing floating supporting structures for HAWT, mainly for deep water deployment. This paper describes the development of a floating support structure for Vertical Axis Wind Turbines (VAWT) with particular focus on structural/survival risk and reliability. Unlike Oil & Gas floating support structures, wind turbine floaters need to resist significant dynamic wind and machine loading in addition to wave excitation. This theory can now be used in buildings. (Ref. - “Reliability of floating foundation concepts for vertical axis wind turbines”: http://www.researchgate.net/publication/202267812.)
    S. G. Chung et al., (2010), did a study and published a journal on Performance of a medium tall building supported by a floating foundation on the Nakdong River deltaic deposit. A medium-tall building, which has a floating foundation with irregular-shape in plane and different loading conditions at each part, was built on thick soft soil where it's condition varies spatially, in the Nakdong River delta. A comprehensive design for ground improvement and the building as well as field monitoring of them have been adopted during and after the construction. Despite the difficult conditions that are seldom found in the world, the building has been successfully constructed, indicating that the measured settlements were within the allowable values. A discussion especially focuses on the settlements that occurred during the construction. Also while drafting this journal reference from “Golder, H.Q. (1975). Floating Foundation.Foundation Engineering Handbook, edited by H.F. Winterkorn and H.Y. Fang, Van Nostrand Reinhold Co, pp. 537–555” was taken, which briefly discussed about the soil conditions and settlement problems and about soil sampling and it’s properties. In this journal, the design concept of the floating foundation and ground improvement as well as field monitoring during and after the construction of the embankment and building are presented.
    (Ref.- Performance of a medium tall building supported by a floating foundation on the Nakdong River deltaic deposit.)
    .
    2.3 SUMMARY OF LITERATURE REVIEW
    Earlier the concept of Archimedes’ principle was used for gas and oil floating support. It was then used for supporting offshore wind turbines developing floating support structure for Vertical Axis Wind Turbines (VAWT) with particular focus on structural/survival risk and reliability. This concept was then applied to onshore structures. From the above journals it can be understood that
    Problems of design and construction of floating foundation consists of excavation, water lowering, bottom heave, settlement and structure problems.
    The discussions especially focus on the settlements that occurred during the construction.
    Increasing the excavation depth decreases the amount of maximum settlement because of reducing the net pressure on the sub-soil.



    CHAPTER 3

    OBJECTIVES AND SCOPE
    3.1 GENERAL
    The objective, scope, the grade materials used with their unit weights and the methodology followed in the project has been discussed in this chapter.
    3.2 OBJECTIVE
    The objective of this project is to construct a structure in an irregularly shaped plot so an irregular structure giving the best possible utilization of the plot space has to be planned accordingly. The foundation has to be designed with Pile Foundation and Floating Foundation. For the sole purpose of modern construction techniques, Floating Foundation has to be opted for. Planning and analysis of the structure has to be done using software (AutoCAD and SAP2000) and the design of the irregular structure has to be done manually.
    3.3 SCOPE
    The scope of the project is to prepare the plan in AutoCAD. Then modelling of the superstructure and analysis is done using SAP2000. For better understanding of concepts, design of the structure is done manually. Since this site is situated near the Brahmaputra river, the soil is very loose. So the structure has been designed with Floating Foundation and Pile Foundation.
    3.4 MATERIALS AND METHODOLOGY
    The materials used while designing the structure are Fe415 grade steel, M25 grade concrete. Brick work was done for the walls using nominal size bricks of unit weight 19.20 kN/m3. The methodology followed in this project is as follows. The first step is to make the plan of the structure of the irregularly shaped plot. Then we proceed for size fixation. Modeling and analysis of the superstructure is done using SAP2000. The design of the superstructure and foundation is done manually.


    CHAPTER 4

    RESULTS AND DISCUSSION
    4.1 GENERAL
    This chapter discusses about planning, analysis and design of the proposed Institutional Building. The plan was made using AutoCAD and the analysis of the superstructure was done in SAP2000 in order to obtain the member forces. The designing of the structural members, pile foundation and floating foundation was done manually in order to have a better understanding of the concepts.
    4.2 PLANNING
    The description of the structure and floor plan are discussed in this chapter.
    4.2.1 BUILDING DESCRIPTION
    The proposed building is an irregular institutional building in Assam.
    Total floors S+2
    Each floor area 98.05 sq. m
    Total built-up area 392.02 sq. m
    Floor height 3.2 m
    Total no. of rooms 6 rooms per floor
    Total no. of washrooms 1 each floor
    Width of Main staircase 2.20 m
    Width of inner staircase 0.90 m
    Outer wall thickness 0.230m
    Inner wall thickness 0.115m
    Type of structure framed structure

    4.2.2 PLAN OF THE FLOORS

    Figure 4.1 shows the statement of the area that the structure will use.


    Fig. 4.1 Area Statement


    The following Figures 4.2, 4.3, 4.4 and 4.5 show the plan of the basement, ground, first and second floor of the structure respectively. The respective level of the floors are -1.5 m, +1.5 m, +4.8 m and +8.1 m for the basement, ground, first and second floor of the structure respectively with 0 m being the ground level.



    Fig. 4.2 Basement plan




    Fig. 4.3 Ground floor plan


    Fig. 4.4 First floor plan

    Fig. 4.5 Second floor plan
    4.3 ANALYSIS
    The modelling and analysis of the super structure and the critical section has been found out as discussed below.
    4.3.1 DIMENSIONS USED FOR MODELING IN SAP2000
    Table 4.1 shows the dimension of the members used in the structure.
    Table 4.1 Dimension of members
    MEMBER WIDTH (mm) DEPTH (mm)
    COLUMN 300 600
    BEAM 350 550
    SLAB THICKNESS 115


    4.3.2 MODELLING OF THE STRUCTURE
    The following Figures 4.6, 4.7, 4.8 and 4.9 show the various views of the
    structure which has been modelled in SAP2000 software.


    Fig. 4.6 General modeling of the structure


    Fig. 4.7 Modelling with filled material


    Fig. 4.8 Extrude view of the structure


    Fig. 4.9 Top view of the structure

    The following Figures 4.10 and 4.11 show the properties of the critical beam section.


    Fig. 4.10 Critical Beam Section


    Fig. 4.11 Forces in critical section (Beam)

    The following Figures 4.12 and 4.13 show the properties of the critical column section.


    Fig. 4.12 Critical Column Section


    Fig. 4.13 Forces in critical section (Column)

    4.3.3 ANALYSIS RESULTS OF THE CRITICAL MEMBERS
    Table 4.2 shows the values of the bending moment, shear force and axial load of the critical sections.
    Table 4.2 Analysis results
    Critical Section Bending Moment (kNm) Shear Force (kN) Axial Load (kN)
    Left End Middle Right End Left End Right End
    BEAM NO: 29 261.041 -23.025 -332.869 257.221 308.408
    COLUMN NO:43 36.36 13.81 -8.73 15.03 15.03 3557



    4.4 DESIGN OF STRUCTURAL MEMBERS
    This chapter deals with the design and detailing of slabs, beams, columns and footing.
    4.4.1 DESIGN OF SLAB
    DATA:
    Concrete = M25
    Steel = Fe415
    Depth = 115 mm
    Shorter Span = 4.243 m = Lx
    Longer Span = 5.281 m = Ly

    Step 1: Rate of Longer Span to Shorter Span

    Hence the slab to be designed is a “Two way slab” with provision of torsion at the corner.

    Step 2: Depth of Slab
    Adopted depth of slab = 115mm = overall thickness = D
    Assuming = 10 mm
    Nc = 30mm [page 47, IS 456: 2000]
    Therefore Effective depth = d = = 80 mm

    Step 3: Effective span
    Shorter side
    Lx* = (Clear span + Effective depth)
    Lx = 4.323 m
    Similarly, for longer span
    Ly = 5.361 m

    Step 4: Loads
    S/W of slab = kN/m2
    Live Load = 4 kN/m2
    Floor Finish = 0.5 kN/m2
    Total Load = 7.375 kN/m2
    Therefore Total factorial load = (7.3751.5) kN/m2
    = 11.0625 kN/m2
    Therefore W = 11.0625 kN/m2

    Step 5: Ultimate design moments

    Referring to Table 26 (IS456: 2000)
    (For two adjacent edges discontinuous)
    αx (+) (positive moment at mid span)
    αx (+) = 0.046 [By interpolation]
    αx (-) (Negative moment at continuous edge)
    αx (-) = 0.061
    Also
    αy (+) (positive moment at mid span)
    αy (+) = 0.035
    αy (-) (Negative moment at continuous edge)
    αy (-) = 0.047
    Therefore we have
    αx (+) = 0.046
    αx (-) = 0.061
    αy(+) = 0.035
    αy(-) = 0.047
    Now
    Mx = αx wlx2 (4.1)
    My = αy wlx2 (4.2)

    Therefore
    (1) Mx(+) = 9.51 kNm
    (2) Mx(-) = 12.61 kNm
    (3) My(+) = 7.24 kNm
    (4) My(-) = 9.72 kNm
    Also
    (4.3)
    = 23.92 kN

    Step 6: Check for depth
    (4.4)
    12.61106 = 0.138fck b d2
    d = 60.46 < 80 mm
    Hence Safe

    Step 7: Reinforcement details
    (4.5)

    Case 1:
    Mx(+)=9.51kNm


    Ast = 355.41 mm2
    Providing 10 mm bars:
    Spacing = {
    {300 mm
    {3d = 240 mm
    Therefore provide 10 mm @ 220 mm c/c
    Also
    Ast (provided) = 357 mm2
    Case 2:
    My(+) = 7.24 kNm


    Ast = 265.26 mm2
    Providing 10 mm bars
    Spacing = {
    {300 mm
    {3d = 240 mm
    Therefore providing 10 mm @240 mm c/c
    Case 3:
    Mx(-) = 12.61 kNm


    Therefore Ast = 485.47 mm2
    Providing 10 mm bars
    Spacing = {
    {300 mm
    {3d = 240 mm
    Therefore providing 10 mm @160 mm c/c
    Case 4:
    My(-) = 9.72 kNm


    Ast = 364 mm2
    Providing 10 mm bars


    Spacing = {
    {300 mm
    {3d = 240 mm
    Therefore providing 10 mm @ 210 mm c/c

    Step 8: Check for shear stress
    Vu = 23.92 kN
    Now

    Therefore (4.6)

    Therefore τc = 0.25 0.36
    0.446 x
    0.50 0.49
    X = 0.462 N/mm2
    Therefore τc = 0.462 N/mm2
    Also
    Ks = 1.30
    Ks τc = 0.4621.3 = 0.6 N/mm2
    Also
    τc max = 3.1 N/mm2
    Therefore τv < ks τc
    τv < τc max.
    Hence no shear reinforcement is required.
    Step 9: Check for deflection
    Pt = 0.446
    Also,



    Fs = 239.62 ≈ 240 N/mm2
    Therefore Modification factor = 1.46
    Now,


    Hence deflection criteria is satisfied.
    The following figure 4.14 shows the detailing of the critical slab.
    488mm

    3843mm



    Fig. 4.14 Slab Detailing
    4.4.2 DESIGN OF BEAMS
    Given data:
    Span = 2.1 m
    Width = 350 mm = b
    Depth = 550 mm = d
    Mu (max) = 332.87 kNm
    SF (max) = 308.41 kN

    Step 1: Check for lateral stability/lateral bucking (Page 39, clause 23.3)
    Allowable

    L = 21 m or 55.68 m [Lesser of the two]
    Now actual length (2.1 m) < allowable length
    Hence Safe
    Now, Factored Moment Mu = 332.87 kNm
    Factored Shear SF = 308.41 kN
    Now,
    Assuming Mu = Mu limit = 332.87 kNm
    332.87106 = 0.13825350d2
    d = 525.04 m
    Hence Safe
    Now
    Actual Mu = 332.87 kNm
    Therefore Mu limit = 0.138253505502
    Mu limit = 365.26 kNm , therefore Mu < Mu limit
    Hence singly reinforced beam (under reinforced section).

    Step 2: Calculation of Steel
    Since the section is under reinforced, we have
    Using equation G.1.1 (b) [IS 456:2000]

    (4.7)


    Ast = 2010 mm2
    Taking 32 mm bar
    No of bars required =
    [Taken in even no.s]
    Also Ast (prov.) = 2412.74 mm2

    Step 3: Distance between any two bars
    Minimum distance between two bars is greater of the following:
    (a) Size of aggregate + 5m = 20+5 = 25 mm
    (b) Size of the bar = 32 mm
    Therefore Minimum distance = 32 mm

    Therefore 3 # of 32 mm @ 90 mm c/c.
    Check for Ast min & Ast max
    Ast min =
    = 453.19 mm2

    Hence Safe

    Step 4: Check for Shear
    Vu = 308.41 kN


    [Table 19, IS 456:2000, Page 73].
    Therefore τc = 0.65 N/mm2
    Now, τv max = 3.1 N/mm2
    Therefore τv > τc Hence shear reinforcement is required
    Selecting 2-L vertical stirrup of = 8mm.
    Asv = = 100mm2.
    Vuv = Vu - Vc

    = 308.41 – 125.13
    = 183.28 KN
    Therefore (4.8)

    Check for max. spacing
    Max. spacing = 0.75 or 300 mm (whichever is less)
    Therefore Max. spacing = { 0.75d = 412.5
    {300 mm
    {108.34 mm
    Therefore provide 8 mm 2-L vertical stirrup @ 105 mm c/c
    Check for Asv min

    (4.9)

    Hence Safe
    Step 5: Check for deflection

    Fs = 192.5 N/mm2 [Figure 4, IS456:2000, page 38]
    Pt = 1.04
    Therefore Modification factor = Mt = 1.1
    Therefore Mc = 1 [No compression reinforcement]
    Allowable l/d = 261.111 = 28.6.
    Actual Hence Safe

    The following figure 4.15 shows the detailing of the critical column.


    Fig. 4.15 Beam Detailing

    4.4.3 DESIGN OF COLUMN
    Given:
    Pu = 3557 kN
    b = 300 mm
    d = 600 mm
    Mx = 36.36 kNm
    My = 8.74 kNm
    Fe415 and M25 grade concrete

    Step 1:
    Length = 3.3m
    = 3300 mm

    Step 2: Slenderness ratio
    λ = effective length/least radius of gyration

    Since it is less than 12, it should be designed as biaxial loaded short column.
    Step 3:
    Assuming nominal cover as 40mm and 25mm diameter


    From IS 456:2000, Chart 44, page 129
    We take d’/D = 0.10

    Step 4:

    = 0.79
    (4.10)

    kNm
    (4.11)

    Therefore, from graph [IS456:2000, Chart 44, page 129]

    P = 0.1225
    = 3%
    (4.12)


    Note: Reinforcement distributed along 4 sides as it is biaxial
    Taking diameter as 32 mm

    No. of bars
    Provide 8 bars of 32 mm
    Ast (prov.) = 6434 mm2

    = 3.57
    = 0.14
    (4.13)

    From graph [IS456:2000, Chart 44, page 129]
    (4.14)

    = 0.085253006002 = 229.5 kNm

    From graph [IS456:2000, Chart 46, page 131]
    (4.15)


    = 128.25 kNm
    Step 5:
    (4.16)


    = 3955.2 kN

    So, for 0.8 of the value

    Step 6: Check for Bresler’s empirical formulation
    (4.17)

    = 0.029 < 1
    Hence it is safe

    Step 7: Design of lateral tie
    L = {
    {8 mm
    L = 8 mm
    Spacing = {300 mm
    {1632 mm
    {300 mm
    Provide 8 mm @ 300mm spacing
    The following figure 4.16 shows the detailing of the critical column.

    Fig. 4.16 Column Detailing (Ductile elevation and cross sectional view)
    4.4.4 DESIGN OF PILE FOUNDATION
    Given Data
    Let us assume that the column is resting on 4 piles.
    The diameter of piles = 300 mm
    Therefore spacing of piles is equal to 3 times the diameter of piles = 900 mm
    Size of the pile cap ≈ 5 times the diameter of the pile
    Assume depth of pile cap = 800 mm

    Step 1: Total loads on piles
    Self-weight of pile cap = 1.51.50.825 = 45 kN
    Load on column = 3557 kN
    Total load on piles = 3602 kN
    Therefore Load on each pile

    Step 2: Moment on piles
    M1 = 36.36 kNm
    M2 = 15.030.8 (due to shear force) = 12.024 kNm
    M = 36.36 + 12.024 kNm
    M = 48.384 kNm
    Total load on each pair of pile (load always occurs on pair of piles)
    (4.18)

    P = 26.88 kN
    Total load on pile = 900.5 + 26.88 = 907.38 kN ≈ 930 kN
    Therefore factored load = 930 1.5 = 1395 kN
    Pu = 1395 kN

    Step 3: Depth of the pile (height of the pile)
    (4.19)

    Here Qu = Pu = 1395 kN
    q˳ = surcharge
    k=1.75
    = 17˚
    Ap = area of pile = 0.30.9 = 0.09m2
    D = diameter of pile
    S = 4DH = 40.3H = 1.2H
    1395 = 1.2H [20+9H]1.75tan17˚+ 0.09[0.50.31810+18H15]
    1395 = [24H+10.8H2]0.535 + 2.43+24.3H
    1395 = 12.84H + 5.778H2 + 2.34+24.3H
    5.778H2 + 37.14H = 1392.66
    H2 + 6.43H – 241.03 = 0
    H = 12.64 m

    Step 4: Reinforcement details
    (4.20)

    Asc = 1846.67 mm2
    No of bars = 6
    = 20 mm
    Therefore

    Step 5: Design of lateral ties
    L = { mm (cannot be less than 6 mm)
    {6 mm
    But available size of bars in market starts from 8 mm
    Therefore L = 8 mm
    Spacing = {300 mm
    {1620 = 320 mm
    {300 mm
    Therefore provide 8 mm L @ 300 mm c/c
    Step 6: Design of helical ties
    Provide nominal cover 40 mm
    Core diameter
    = 220 mm
    Assume = 8 mm
    (Page 41, 39.4.1, IS456:2000)
    ρs = (volume of spiral reinforcement/volume of core)
    (4.21)
    ρs= 0.88/Spacing
    Now, (4.22)

    St 38 mm
    Now check page 49 (d) helical reinforcement [IS 456:2000]
    Max. spacing (not more than 75 mm) = {
    Min. spacing (not less than 25 mm) = {3 8 = 24 mm
    {25 mm
    Therefore provide 8 mm @ 35 mm c/c.

    Step 7: Design of pile cap
    P = M/S
    M = 2(1395 0.15)
    M = 418.5 kNm
    (4.23)
    418.5 106 = 0.138 25 1500 d2
    d = 284.37 mm
    = 284.37 + 75 + 25 =384.37
    D = 384.37 ≈ 385 < 800 mm
    Safe
    Now
    d = 385 – Nc
    = 385 – 75 – 25 = 285 mm
    (4.24)

    4067.08 – Ast + 5.8810-5Ast2 = 0
    Therefore Ast = 5067 mm2
    = 25
    Ab = 491 mm2
    No of bars = 10.31 ≈ 12 no.s
    Therefore provide 12 # 25 mm both ways (top & bottom).
    The following Figure 4.17 shows the detailing of the footing.





    Fig. 4.17 Pile Foundation Detailing (Top view and Pile Cap cross sectional view)

    4.4.5 DESIGN OF FLOATING FOUNDATION
    Table 4.3 shows the dead load of the structure transferred from ground column obtained from SAP2000.



    Table 4.3 Dead load transferred from ground column

    Ground Column Axial Load (kN) Ground Column Axial Load (kN)
    G.C1 184.86 G.C25 324.24
    G.C2 236.89 G.C26 311.92
    G.C3 212.27 G.C27 484.23
    G.C4 251.91 G.C28 306.87
    G.C5 196.80 G.C29 156.81
    G.C6 248.86 G.C30 241.04
    G.C7 370.38 G.C31 439.10
    G.C8 338.68 G.C32 488.91
    G.C9 396.11 G.C33 378.08
    G.C10 287.86 G.C34 343.97
    G.C11 307.20 G.C35 363.25
    G.C12 433.59 G.C36 156.15
    G.C13 376.73 G.C37 299.92
    G.C14 287.37 G.C38 399.77
    G.C15 286.28 G.C39 240.73
    G.C16 412 G.C40 357.89
    G.C17 402.60 G.C41 326.99
    G.C18 290.95 G.C42 149.93
    G.C19 258.24 G.C43 391.94
    G.C20 359.59 G.C44 209.99
    G.C21 430.59 G.C45 141.59
    G.C22 300.40 G.C46 202.17
    G.C23 315.34 G.C47 149.39
    G.C24 551.07


    Data Given
    Size of raft = 45.5 X 21.25 m
    γ = 18 kN/m3
    Total load = 14601.45 kN
    Step 1: Net foundation pressure
    Gross foundation pressure = q
    (4.25)

    Provide depth of foundation = 650 mm = Df
    (4.26)
    = 3.4 kN/m2

    Step 2: Bearing capacity
    Cu for soft grey silty clay soil = 30 kN/m2
    Now
    (4.27)
    = 5.0
    Therefore qnet (n) = Cu Nc
    = 30 X 5.0 = 150 kN/m2
    Therefore = 44.1 > 2.5
    Hence safe

    Step 3: Immediate settlement
    qu = 3.4 kN/m2
    B = 21.25 m
    v = 0.75
    = 2.14
    Cu (avg.) = 30 kN/m2
    Now, E = 700 X Cu = 700 X 300 = 21000 kN/m2
    Therefore (4.28)
    = 0.0032 m
    (4.29)
    = 781.5 kNm/m

    Step 4: Reinforcement Details
    (4.30)


    Using 32 mm bars
    No. of bars
    Spacing
    Provide 6 # 32 mm bars @ 160 mm c/c
    Minimum reinforcement of slabs = 0.12 %
    = 0.12/100 x 650 x 1000
    = 780 mm2/m < 4067 mm2/m
    Hence safe
    The following Fig.4.18 shows the detailing of the Floating foundation.







    Fig.4.18 Detailing of the Floating foundation


    CHAPTER 5

    CONCLUSION

    • Sufficient knowledge on planning and analysing using software has been gained.
    • The structure has been designed manually to have a better understanding of the design procedure.
    • Knowledge on design procedures and detailing of the members as per codal provisions has been gained.
    • Understanding of the foundation with respect to the soil requirements has been gained.
    • The particular site considered in this project is located in Assam which falls under seismic Zone V. So in addition to the dead load and live load considered, load factor of seismic load is considered.
    • The dimension of the slab is 5231 mm x 4243 mm. For the middle strip portion, the shorter dimension Lx, the reinforcement details is 10 mm dia. bars @ 220 mm c/c. and along the longer dimension, the reinforcement details is 10 mm dia. bars @ 240 mm c/c. For the edge strip portion, the reinforcement details is 10 mm dia. bars @ 240 mm c/c.
    • The reinforcement detailing of the beam consists of 3 no. of 32 mm dia. bars @ 90 mm c/c. at the bottom and 2 no. of 12 mm dia. Hanger bars at the top.
    • The reinforcement detailing of the column consists of 8 no. of 32 mm dia. bars and 8 mm dia. lateral ties @ 300 m c/c.
    • The reinforcement detailing of the Pile Foundation is 6 no. of 20 mm dia. bars with 8 mm dia. lateral ties @ 300 mm c/c. The pile cap consists of 12 no. of 25 mm dia. bars on both sides.
    • The reinforcement detailing of the Floating Foundation consists of 6 no. of 32 mm dia. bars @ 160 mm c/c and 4-L shear stirrup.


    REFERENCES

    1. Geo-Frontiers 2011: Advances in Geotechnical Engineering (edited by Jie Han, Daniel E. Alzamora), Geo-technical aspects for Design and Performance of Floating Foundations [Page: 56-65].
    2. Performance of a medium tall building supported by a floating foundation on the Nakdong River deltaic deposit.
    5. Golder, H.Q. (1975). Floating Foundation. Foundation Engineering Handbook, edited by H.F. Winterkorn and H.Y. Fang, Van Nostrand Reinhold Co, pp. 537–555.
    7. Tomlinson, M.J. (1995) Foundation Design and Construction. Longman Scientific & Technical, Singapore.
    8. ISRN Civil Engineering (2012), Pile Foundation. Design of Pile Foundation, edited by P. J. S. Cruz and I. Smith, Goldwind Science & Technology Company Ltd, China.
    10. National Building Code (NBC) for dimensions.
    11. IS456:2000, Plain and Reinforced Concrete – Code of practice, BIS, New Delhi.
    12. SP: 16, “Design Aids For Reinforcement Concrete” BIS, New Delhi.
    13. IS1893(part I):2002, “Code of Practice for Earthquake Resistant Design of Structures” BIS, New Delhi.
    14. IS13920:1993, “Code of Practice for Ductile Detailing Of Reinforced Concrete Structures Subjected To Seismic Forces” BIS. New Delhi.
    15. Varghese. P.C.,”Limit State design of Reinforced concrete”, Second edition, Prentice-Hall of India Private Limited, New Delhi.

    Last edited by ajaytopgun; 23rd September 2015 at 12:01 PM.