Analysis And Design Of Mosque 3l3l6f

Analysis and Design of mosque

Industrial Training report 2013

CHAPTER 1 INTRODUCTION Reinforced concrete occupies a leading position modern construction along with pre stressed concrete and steel construction. Proper construction depends upon through knowledge of action of structure and on the knowledge of characteristics and limitations of materials that are used in the construction. The care with work is executed in the site is also important in construction industry. Industrial training always helps to have practical exposure to the different methods of analysis and design in reinforced concrete. it helps to understand theory along with the use of structural engineering software. The entire spectrum of structural engineering field includes analysis, design, detailing , and drafting , also site related problems are under stood. The issue related to soil engineering and the study of soil investigation reports, interpretation of data and foundation design is also understood. Understanding different software tools in structural engineering, its limitations. The major project assigned during training was a multi storied mosque building at Malappuram. Site visits are also conducted during training.

Department of Civil Engineering

1

KMEA Engineering college



CHAPTER 2 ABOUT THE PROJECT Industrial training was on modeling, analysis, deg and detailing of a multistoried mosque building. The proposed site is at Malappuram. Here basement floor, ground floor, first floor, second floor are intended for prayer. The height of building is about 16.7m. The structural system consists of RCC conventional beam slab arrangement. Kerala is considered in seismic zone III as per IS 1893- 2002. Analysis was carried out using a very sophisticated software tool STAAD PRO v8i. Detailed analysis and design was carried out based on architectural drawing available and the results are summarized in the report.


2




CHAPTER 3 DESCRIPTION OF STAAD Pro

3.1 GENERAL STAAD Pro is comprehensive structural engineering software that addresses all aspects of structural engineering – model development, analysis, design, verification and visualization. This uses finite element method for analysis. One can building model, it graphically, perform analysis and design, review the results, and create report all within the same graphical base environment.

3.2 THE MODELLING MODE There are two methods for building a model and asg the structure data using STAAD Pro. a. Using the command file b. Using the graphical model generation mode or graphical interface (GUI) as it is usually referred to. The command file is a text file, which contains the data for the structure being modeled. The file consists of simple English language like commands, using a format native to STAAD Pro. This command file may be created directly using the editor built into the program, or for that matter, any editor which saves data in text form, such as Notepad or WordPad available in Microsoft Windows. The graphical method or creation involves utilizing the Modeling mode of the STAAD Pro graphical environment to draw the model using the graphical tools, and asg data such as properties, material constants, loads, etc., using the various menus and dialog boxes of that mode. If the second method is adopted (using the UGI), the command file gets automatically created behind the scenes


3




Fig 3.1 THE PLAN OF THE STRUCTURE PRODUCED USING STAAD Pro


4




Fig 3.2 ISOMETRIC VIEW OF THE STRUCTURE FROM STAAD Pro


5




Fig 3.3 THE MODEL PROUCED USING STAAD Pro


6




The graphical model generation mode and the command file are seamlessly integrated. So, at any time, the graphical model generation mode can be temporarily exited and access the commend file. When changes are made to the command file and saved, the GUI immediately reflects the changes made to the structure through the command file. The frame of the building after modeling is shown in Fig.

3.3 PERFORMING ANALYSIS AND DESIGN STAAD offers two analysis engines – the STAAD engine for general purpose Structure Analysis and Design and the STARDYNE engine for advanced analysis options. The modeling mode of the STAAD environment is used to prepare the structural input data. After the input is prepared, the analysis engine can be chosen depending upon the nature of the analysis required. Depending on the type of analysis option selected, different types of output files are generated during the analysis process. The STAAD analysis engine performs analysis and design simultaneously. But, to carry out the design, the design parameters too must be specified along with geometry, properties, etc. before performing the analysis. The design code to be followed for design can be selected before performing the analysis/design.

3.4 POST PROCESSING MODE The Post Processing Mode of STAAD offers facilitates for on – screen visualization and verification of the analysis and design results. Displacements, forces, stresses, etc. can be viewed – both graphically and numerically in this mode. Most of the menu items in the post processing mode are the same as in the modeling mode. STAAD also enables preparation of comprehensive reports that include numerical and graphical result. Printable reports may be generated in two ways. Through the STAAD output file and through the report setup facility from the Post Processing Mode. The STAAD output file is a text file containing results, diagrams etc. It is a more versatile facility than the output file in of – level control.


7




CHAPTER 4 GENERAL PRINCIPLE OF DESIGN 4.1 OBJECTIVES OF STRUCTURAL DESIGN The design of the structure must satisfy the following requirements  Stability : To prevent the overturning , sliding or buckling of the structures, or any part of it under action of loads.  Strength : to resisit safely the stresses induced by the loads in the various structural  Serviceability : To ensure satisfactory performance under service load conditions which implies providing adequate stiffness and reinforcement to contain deflections, cracks widths and vibrations with in adequate limits and also providing impermeability and durability. There are other considerations that a sensible designer ought to bear in mind , viz.., Economy and aesthetics. One can always design a massive structure , which has more than adequate stability, strength and serviceability ,but the ensuing cost of the structure may be exorbitant and the end product far from aesthetics. 4.2 SOIL INVESTIGATION REPORT: The building site is located at Malappuram. The proposed site consists of top layer of very loose sand followed by soft to medium silty clay followed by Lateritic sandy clay with pebbles followed by silty clay/clayey sand followed by very dense sand. From the site observation, the soil condition of the site was medium soil of safe bearing capacity 200 kN/m2. Hence it is recommended foundation for this is isolated sloped footing


8




CHAPTER 5 STRUCTURAL ANALYSIS USING STAAD Pro

5.1 GENERAL Analysis is done using STAAD Pro, as it is widely used for structural analysis and design from Design Engineers International. While doing analysis material and geometric properties are assumed. Loading considered in analysis are dead load, live load, seismic load and wind load. Finally on running program output values are obtained, M15 grade and Fe415 steel is used.

5.2 LOADS CONSIDERED IN THE DESIGN Structural analysis of the structure need to be preceded with the calculation of load imposed on the structure. Various loads taken into for the analysis of the structure include live load, dead load, wind load and seismic load. As the area falls under zone III of the earthquake classification as per Indian Standards, seismic design of the structure is mandatory. IS 875 Part I deals with dead loads, IS 875 Part II with imposed load, IS 875 Part III with wind load and IS 1893 Part I with seismic load. The loading standard not only ensures structure safety of building but also eliminate wastage caused by assuming unnecessary heavy loadings without proper assessment.

5.2.1 DEAD LOAD Dead loads are loads that are constant in magnitude and fixed in position throughout a particular span. It includes self – weight of all structural components in that span. Dead loads have been determined after assuming both material as well as geometric properties of all elements used in the building. Unit weight of RCC and brickwork are adopted as 25 KN/m and 20KN/m respectively.

5.2.2 IMPOSED LOAD The load is assumed to be produced due to the intended use or occupancy of a building, load due to impact and vibration, and dust load, but excluding wind, seismic, and other loads due to temperature changes, creep, shrinkage, differential settlement etc.

Imposed loads assumed for an assembly building shall be load that will be produced by the intended used or occupancy, but shall not be less than the equivalent


9




minimum loads specified by table-1 IS 875 Part II. Live loads of all floors are assumed as 4 kN/m2.

5.2.3 WIND LOAD Wind may be defined as air in motion relative to the surface of the earth. Buildings should always be designed with due attention for the effect of wind. In general, wind speed in the atmospheric boundary layer increases with height from zero at the ground level to maximum at a height called the gradient height. Slight change in the wind direction at this height is neglected in the code. Basic wind speeds (Vb) for different wind zone of India are obtained from IS 875 Part III (Appendix A). From this basic wind speed, the design wind speed (in m/sec) for each storey at height „z‟ is called from Vz = Vb x k1 x k2 x k3 Where,

k1, k2 ,k3 = coefficients from IS 875 Part III,

5.2.4 SEISMIC LOAD For the purpose of determining seismic forces, the country is classified in to four seismic zones. Location of the structure falls under area of zone III. The seismic effect, i.e., the intensity and duration of the vibrations, depend on the magnitude of the earthquake, depth of focus, distance from epicenter, soil strata which hold the structure etc. As per IS 1893 Part I, clause 6.1.2, the response of a structure to ground vibration is a function of the nature of foundation soil, materials, from size and mode of construction of structures and duration and characteristics of ground motion. This standard specifies design forces for structures standing on rocks or soil which do not settle liquefy or slide due to loss of strength from ground vibration. Also the following assumptions are made for the earthquake resistant design of structures.  Earthquake causes impulsive ground motions, which are complex and irregular in character, changing in period and amplitude each lasting for a small duration. Therefore resonance of the type as visualized under steady state sinusoidal excitations will not occur as it would need time to build up such amplitudes.  Earthquake is not likely to occur simultaneously with wind or maximum flood or maximum sea waves.  The value of elastic modulus of materials, wherever required, may be taken as for static analysis unless a more definite value is available for use in such condition. The seismic weight of each floor for the analysis is to be taken as its full dead load plus appropriate amount of imposed loads. While computing the seismic weight of each floor,


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the weight of columns and walls in any storey shall be equally distributed to the floors above and below. Percentage of imposed load as taken from table 8 of IS 1893 – 2002 is 50%.

5.3 LOAD CALCULATIONS 5.3.1 SEISMIC LOAD Design horizontal seismic coefficient, Ah = ZISa/2Rg (From IS1893 (Part I)–2002 clause 6.4.2) Where, Z = Zone factor = 0.16 (from IS1893 (Part I)–2002 clause 6.4.2 Table 2) I = Importance factor = 1.5 (from IS1893 (Part I)–2002 clause 6.4.2 Table 6) R=response reduction factor (from IS1893 (Part I)–2002 clause 6.4.2 Table 7) SS = Rock and soil silt factor = 2 (for medium soil)

5.3.2 DEAD LOAD Floor load Dead load of slab = 0.12 x 25 = 3kN/m2 Finishes

= 1kN/m2

Total

= 4 kN/m2

Brick wall load 4.2 m high = 0.23 x 4.2 x 20 = 19.32 kN/m

5.3.3 LIVE LOAD

Live load on floor

= 4 kN/m2

Live load on Roof

= 4 kN/m2

5.3.4 WIND LOAD Basic wind speed in Trivandrum = vb = 39 m/s (from IS 875, Part III) Design wind speed = vz = vb x k1 x k2 x k3 k1 = Probability factor k2 = Terrain and size factor


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k3 = Topography factor Design wind pressure Pz = 0.6 x vz2 TABLE 5.1 WIND LOAD CALCULATIONS

FLOOR

V

K1

k2

PZ (kN/m )

1

40.95

1.00614515

1.05

1

40.95

1.00614515

1

1.0732

1

41.8548

1.05109457

1

1.1026

1

43.0014

1.10947224

m/s

GROUND FLOOR

3.9

39

1

1.05

FIRST FLOOR

8.7

39

1

SECOND FLOOR

12.9

39

ROOF

17.1

39


b

2

VZ (m/s)

HEIGHT m

k 3

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5.4 LOAD COMBINATIONS

The various load combinations that are adopted in the analysis are shown in table

TABLE 5.2 LOAD COMBINATIONS

DL+LL

1.5

DL+WLX

1.5

1.5

DL+WLZ

1.5

1.5

DL+ELX

1.5

1.5

DL+ELZ

1.5

1.5

DL+WLX

0.9

1.5

DL+WL

0.9

1.5

DL+ELX

0.9

1.5

DL+ELZ

0.9

1.5

DL+LL+WLX

1.2

1.2

1.2

DL+LL+WLZ

1.2

1.2

1.2

DL+LL+ELX

1.2

1.2

1.2

DL+LL+ELZ

1.2

1.2

1.2

Z


1.5

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Fig 5.1 WIND LOAD IN X DIRECTION.

Fig 5.2 WIND LOAD IN Z DIRECTION


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Fig 5.3 SEISMIC LOAD in X-Direction

Fig 5.4 SEISMIC LOAD in Z-Direction


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Fig 5.5 BENDING MOMENT DIAGRAM OF GROUND FLOOR

Fig 5.6 SHEAR FORCE DIAGRAM OF GROUND FLOOR


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CHAPTER 6 DESIGN OF RCC BUILDING 6.1 DESIGN OF FOOTING 6.1.1 GENERAL Footing is the type of foundation in which base of wall or column is sufficiently enlarged to act as an individual widened base not only provides stability but is useful in distributing load on sufficient area of the soil. Foundation is the bottom most important component of a structure which generally lies below the ground level. The foundation provided for a RCC beam is called a column footing The column footing is distributing the load over a large area so that the intensity of pressure on soil, and not exceeded safe bearing capacity soil and settlement of structure is kept permissible limit. Types of footings:  Isolated footing  Combined footing  Pile foundation  Continuous footing for walls  Spread footing  Raft or Mat foundation  Strap footing  Cantilever footing 6.1.2 DESIGN OF ISOLATED SLOPED FOOTING Design for: Soil pressure, q = 200 kN/m2 M20, ie., fck = 20 N/mm2 Fe415, ie., fy = 415 N/mm2 Size of column = 600mm x 300mm Design constants For M20 – Fe415 combination, we have:


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= 0.479 and Ru = 2.761 Size of footing W= 2150 kN Self weight of footing shall be assumed as 10% of the column load Total load, P = 2150+215 = 2365 kN Area of footing needed, AF =

= 11.825m2

=

Provide a square footing of size 3.5 m x 3.5 m = 175.5 kN/m2

Net soil pressure acting upward, q0 = Design of footing

Maximum bending moment occurs at the face of column M = q0 (B-bw)2 = 784 kNm Effective depth at the column face, d = √

= 972 mm

Let the effective depth at the column face be„d‟ and that at the edge be 0.2d D = d + 0.2d = 1165 Using an effective cover of 60mm Available depth of footing, d = 1165 – 60 = 1105 mm Effective depth of footing at the edge shall be 0.2d = 195 mm The overall thickness at the edge shall be 195+60 = 255 mm

Check for shear (a) For one way shear V = q0 B [

= 304 kN

Vu = 1.5V = 456 kN Effective depth d‟ at that location = 195 +

(

)]

= 476 mm


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Top width of section = 300 +

= 2510 mm

For under reinforced section, adopt So that xu = 0.4d‟ = 190 mm Width bn at N.A = 2510 +

= 2890 mm

Therefore Ʈv = Vu/bnd‟ = 0.274 N/mm2 Assume P= 0.3% for an under reinforced section Ʈc = 0.384 N/mm2 (From IS 456 table 19) Ʈv < Ʈc

Hence safe

(b) For two way shear Perimeter ABCD = 2 [(a+d)+(b+d)] = 2[600+1105+300+1105] = 6220mm Area of ABCD, A = (a+d)x(b+d) = (600+1105)x(300+1105) = 2.4 m2 Punching shear, Vu = qo [B2-A] = 175.5 [3.52-2.42] = 1728.67 kN = 1.5x1728.67x103/6220x1105 = 0.377 N/mm2

Ʈv = 1.5 Ʈc = 0.25√ Ʈv < Ʈc

= 1.118 N/mm2 Hence safe

Steel reinforcement Ast =

[ –√

] b1d = 2296 mm2

Hence provide 12 numbers of 16mm diameter rods uniformly spaced in the width 3.5m in each direction


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6.2 DESIGN OF COLUMN 6.2.1 GENERAL 

Column forms a very important component of structure.



Column beam which is in turn walls and slabs.



It should be realized that the failure of a column results in a collapse of the structure.



The column is defined as the compression member, the effective length of which exceeds three times the least lateral dimension.



Column may be cost to any of the following shape – square, circular, hexagonal, octagonal.



As per IS 456:2000 a reinforced concrete column shall have longitudinal steel reinforcement shall not be less than 0.80 percentage more than 6 percentage of cross sectional area of the column required to transmit the all loading.



Longitudinal reinforcement is provided to resist compressive load along with the concrete.



The design of column therefore receive importance



The object of stipulating minimum percentage of steel is to make provision to prevent buckling of the column due to any accidental essentially of load on it.



The object of stipulating maximum percentage of steel is to provide reinforcement with such a limit to avoid congestion of reinforcement which would make it very difficult to place the concrete and consolidate it.

6.2.2DESIGN OF RECTANGULAR COLUMN

Material constants

Use M20 grade concrete and HYSD steel bars of grade Fe415. For M20 Concrete, fck

= 20 N/mm2

For Fe415 Steel, fy

= 415 N/mm2

Preliminary dimensioning Depth of column, D


= 600 mm

20




Breadth of column, B

= 300 mm

condition is one end fixed and other hinged Uned length,

= 4.3 m

As per IS 456:2000, Table 28 Multiplication factor for effective length =0.65

Type of column

Longitudinal reinforcement (0.8% is minimum steel area of column as per IS 456:2000) Assume

of steel =

= 0.1

Uniaxial moment capacity of section about xx-axis Assume, Diameter of bar

= 20 mm

Clear cover

= 40 mm

d‟

=clear cover +half the bar diameter = 40+10 =50

Taken


= 0.1

21




Results from STAAD Factored axial load , Pu = 2262 kN Factored moment in x-direction, Mux = 61.74 kNm Factored moment in y-direction, Muxy = 5.89kNm

= 0.628 Assume , reinforcement is equally distributed on four sides Refer chart 48 of SP 16:1980,for

=0.628,

and

,we

get =0.06 = 129.6 kNm

Uniaxial moment capacity of section about yy-axis b =600 mm D =300 mm

= taken

= 0.2

Refer chart 50 of SP 16:1980, for

=0.628,

and

, we get

=0.06 = 64.8 kNm


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Calculation of Puz Refer chart 63 of SP 16:1980, for pt = 2%, fck= 20 N/mm2 and

Puz =

,

= 2700 kN

Refer chart 64 of SP 16:1980, for

we get, permissible value of

&

=0.9

So the percentage of steel assumed is correct. = Provide 12 numbers of 20 mm ϕ bars distributed equally on four sides. Lateral ties According to IS 456:2000, clause 26.5.3.2(c) The diameter of lateral ties shall be not less than 1. One fourth of the diameter of the largest longitudinal bar = 6 mm Hence adopt

of lateral ties as 6 mm

Pitch According to IS 456:2000,clause 26.5.3.2(c) The pitch of transverse reinforcement shall be not more than the least of the following distances:


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i. The least lateral dimension =300 mm ii. Sixteen times the smallest diameter of the longitudinal reinforcement bar =16 =320 mm ii. 300 mm Hence adopt pitch as 300 mm According to IS 13920:1993 clause 7.4.1 Special confining reinforcement should be provided over a length lo from each t face, towards mid span ,where lo shall not be less than i. Larger lateral dimension of column =600 mm ii. One-sixth of clear height of column =

= 466.67 mm

iii. 450 mm Hence adopt lo as 600 mm According to IS 13920:1993 clause 7.4.6 spacing of hoops used as special confining reinforcement:

Hence adopt spacing of hoops =75 mm So provide 6 mm ϕ bars at 75 mm c/c up to a length of 600 mm from face of the t towards mid span and 6 mm ϕ bars at 300 mm c/c at all other places. Special confining reinforcement for column and t details (according to IS 13920:1993)


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6.3 DESIGN OF BEAMS

6.3.1 GENERAL A beam is structural element that is capable of withstanding load primarily by resisting bending. The bending force induced in to the material of beam as result of the external loads, own weight, span and external reactions to these loads is called a bending moment. Beams generally carry vertical gravitational forces but can also be used to carry horizontal loads (ie., loads due to an earthquake or wind). The loads carried by beam are transferred to columns, walls or girders, which then transfer the force to adjacent structural compression . In a light frame construction the joists the joists rests on the beam. Beams are characterized by their profile (the shape of the cross section), their length and their material. In contemporary construction, beams are typically made of steel, reinforced concrete, or wood. The common type is I-beam or wide flange beam. This is commonly used in steel – frame buildings and bridges. Other common beams profiles are C-channel the hollow structural section beam, the pipe and the angle. 6.3.1 DESIGN OF DOUBLY REINFORCED BEAM

Fig6.1: Bending moment diagram


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Fig.6.2 : Shear force diagram Material constants Use M15 grade concrete and HYSD steel bars of grade Fe415. For M15 Concrete, fck

= 15 N/mm2

For Fe415 Steel, fy

= 415 N/mm2

Preliminary dimensioning Width of the beam =230 mm Depth of the beam =600 mm Assume 25 mm clear cover and 20 mm ϕ bars Effective depth =600-25-10 = 565 mm Ultimate moments and shear force (Left end) Ultimate bending moment, Mu = 177.18kNm Ultimate shear force, Vu

=134.9 kN

Limiting moment of resistance (

)

= 0.138 = 0.138 = 151.98 kNm

Mu

(

)

, Hence design as doubly reinforced section


26




2.413 pt

0.818

(from SP16:1980)

Pc

0.106

(from SP16:1980)

1062.99 (required),mm2 1256 (provided),mm2

(#4,20ɸ)

(required),mm2

137.75 226.08

(provided),mm2

(#2,12ɸ)

Ultimate moments and shear force (Mid span) Ultimate bending moment, Mu = 101.53 kNm Ultimate shear force, Vu

=14.021kN


)

= 0.138 = 0.138 = 151.98 kNm

Mu

(

)

, Hence design as single reinforced section 1.33

pt

0.417

(from SP16:1980)

542 (required),mm2 628 (provided),mm2


(#2,20ɸ)

27




Ultimate moments and shear force (Right end) Ultimate bending moment, Mu = 96.91 kNm Ultimate shear force, Vu

=109.171kN


)

= 0.138 = 0.138 = 151.98 kNm

Mu

(

)

, Hence design as single reinforced section 1.32

pt

0.413

(from SP16:1980)

536.7 (required),mm2 628 (provided),mm2

(#2,20ɸ)

Table 6.1: Reinforcement details of beam Details

Left end

Mid span

Right end

Moment

177.18

101.53

96.91

134.9

14.021

109.17

2.413

1.33

1.32

0.818

0.72

0.72

0.106

0.003

0.003

1062.99

935.64

935.64

KNm Shear KN

pt (from SP16:1980)

Pc (from SP16:1980)

(required),mm2


28




942

1256

942

(provided),mm2

(#4,20ɸ,)

(#3,20)

(required),mm2

137.75

-

-

226.08

226.08

226.08

(#2,12ɸ)

(#2,12ɸ)

(#2,12ɸ)

(provided),mm2

(#3,20)

Check for shear stress As per IS 456:2000 clause 40.1

= = 1.038 N/mm2 (

=

)

= 0.966

As per IS 456:2000 ,table 19 Permissible stress ,

=0.59 N/mm 2

As per IS 456:2000 clause 40.4, Strength of shear reinforcement, Vus = Vu

(τc b d) ) –(0.59

= (134,9

)

=58.23 KN


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= 1.03 kN/cm As per SP 16:1980, table 62 Provided

= 1.037 kN/cm

Use 8mm ϕ 2 legged stirrups @ 250 mm c/c According to IS 456:2000, clause 26.5.1.5, The spacing of stirrups in beams should not exceed the least of a) 0.75d =0.75

=423.75 mm

b) 300 mm Maximum spacing of shear reinforcement = 300 mm Therefore provide 8 mm Φ 2 legged stirrups @ 250 mm c/c up to a distance of 0.25 Lef from the face of the and provide 8 mm Φ 2 legged stirrups @ 300 mm c/c in all other places.


30




6.4 DESIGN OF STAIRCASE 6.4.1 GENERAL Staircase in a building, facilitate easy vertical movement of person from one floor to another. Stairway, staircase, stairwell, flight of stairs or simply stairs are names for construction design to bridge a large vertical distance by dividing in to smaller vertical distance called steps. Stairways may be straight around or may consist of two or more straight piece connected at angles. Special stairways include escalators and ladders. Alternative to stairways are elevators, stair lifts and inclined moving sidewalks as well as sanitary inclined sidewalks.

TYPES OF STAIRCASE  Dog legged staircase  Open well staircase  Spiral staircase  Quarter turn staircase 6.4.2 DESIGN OF DOGLEGGED STAIRCASE Material Constants:Concrete, fck = 15 N/mm2 Steel,

fy = 415 N/mm2

Span, tread & rise of the stair are taken from the architectural drawings provided. As per IS 456:2000 clause 33.1 Effective span leff

= 5465 mm

Thickness of slab

= = 200 mm


31




Provide 10 mm diameter bars Clear cover

= 25 mm

Effective depth, d

= 170 mm

Rise of stair

= 170 mm

Tread of stair

= 300 mm

Thickness of the waist slab

= 200 mm

Load calculation Dead load of waist slab

√

= √

The self-weight of the steps is calculated by treating the step to be equivalent horizontal slab of thickness equal to half the rise ( ) Self-weight of step

=0.5 =0.5

Floor finish

=1

As per IS: 875(Part 2)-1987 Table-1 Live load

=4

Total service load

= 12.875

Consider 1 m width of waist slab Total service load / m run =12.875 = 12.875 Total ultimate load


= wu =

32




Ultimate design moment Maximum B.M at the center of span is given by; Mu

=

= = 71.85 kNm Check for depth of waist slab =√

=√ =186 mm

Hence the effective depth selected is sufficient to resist the ultimate moment. Reinforcements From sp16, table 22 ⁄ (

)

=1256 mm2

Check for spacing As per IS 456:2000 clause 26.3.3(b)

Maximum spacing

={

}

={


}

33




= 300 mm

Check for area of steel As per IS 456:2000 clause 26.5.2.1 (

) = = 240 mm2

(

)

(

)

Distribution Steel Distribution reinforcement = 0.12

of cross –sectional area

= 240 mm2 Use 8 mm

bars = = 210 mm

Provide 8 mm

bars at 200 mm c/c.

Check As per IS 456:2000 clause 26.3.3(b) Maximum spacing = {

}

={

}

= 450 mm


34




Check for shear

= = 52.68 kN As per IS 456:2000 clause 40.1 τ

= = 0.301 N/mm2

= τ As per IS 456:2000, Table 20 Maximum shear stress,(τ ) τ

τ

(τ )


35




6.5 SLAB DESIGN 6.5.1 GENERAL Reinforced concrete slabs consists the most common type of structural elements used to cover roofs and floors of buildings. One way slabs are ed on opposite sides and the loads are transmitted in one direction. The reinforced concrete slab ed on all the four edges with the two way slabs ratio of long to short span not exceeding 2 are referred to as two way slabs. Slabs projecting from s or beams are termed as cantilever slabs. Reinforced concrete slabs ed only on columns without beams are called as flat slabs sloping slabs are adopted in the case of shell roof etc. In general the main reinforcement in slabs is provided in the principle bending direction of the slab. Most of slab used in building have an overall thickness in the range of 100 mm to 200 mm while thicker slabs in the range of 200 mm to 500 mm is required in the case of bridge decks to resist heavy loads of vehicles the slabs are designed as beams of unit width for a given type of loading and conditions. The percentage of reinforcement in slab is generally low in the range of 0.30 to 0.50 percent.

TYPES OF SLAB Slabs are classified according to the system of used as under. 

Two way spanning slab



Circular and other shapes



Cantilever slabs



Flat slab ed directly on column without beams.

6.5.2 DESIGN OF TWO WAY SLAB

Material constants Use M20 grade concrete and HYSD steel bars of grade Fe415. For M20 Concrete, fck

= 15 N/mm2

For Fe415 Steel, fy

= 415 N/mm2


36




Type of slab Centre to Centre distance of longer span,

=6m

Centre to Centre distance of shorter span,

=4m

Two way slab Type of slab: two adjacent edges discontinuous Preliminary dimensioning As per IS456:2000, clause 24.1, Thickness of slab = = =114 mm Provide a 120 mm thick slab. Assume 20 mm clear cover and 10 mm ϕ bars Effective depth along shorter direction, dx = 95mm Effective depth along longer direction, dy = 85mm Effective span As per IS 456:2000, clause 22(a) Effective span along short and long spans are computed as: =clear span +effective depth =4 +.095 = 4.095 m =clear span +effective depth =6 +.085 = 6.085 m

Load calculation Dead load of waist slab

=

Floor finish

=1

As per IS: 875(Part 2)-1987 Table-1 Live load


=4

37




Total service load

=8

Design ultimate load,

=1.5

8 = 12

Ultimate design moment Refer table 26 of IS 456:2000 and read out the moment coefficients for

Short span moment coefficients: a) –ve moment coefficient = b) + ve moment coefficient =

=0.075 =0.056

Long span moment coefficients: a) –ve moment coefficient = b) + ve moment coefficient =

=0.047 =0.035

(

)=

=

= 15.092 kNm

(

)=

=

11.268 kNm

(

)=

=

9.45 kNm

(

)=

=

7.043 kNm

Check for depth (

)

= 0.138 =√

(

)

=√ =85.38mm

(95 mm) Hence the effective depth selected is sufficient to resist the design ultimate moment.


38




d) Reinforcements along short and long span directions The area of reinforcement is calculated Referring sp16, table 17, for slab thickness 120mm with 8mm and 10mmɸ bars Table 6.2 reinforcement details in two way slab Location

(required)

(provided)

1)short span Edge section

10mmɸ@ 160mm c/c

10mmɸ@ 150mm c/c

Mid span section

10mmɸ@ 220mm c/c

10mmɸ@ 210mm c/c

8mmɸ@ 170mm c/c

8mmɸ@ 160mm c/c

8mmɸ@ 240mm c/c

8mmɸ@ 230mm c/c

2)long span Edge section Mid span section

Table 6.1: Reinforcement details of slab Check for spacing As per IS 456:2000 clause 26.3.3(b)

Maximum spacing

= {

}

= {

}

= 285 mm

Check for area of steel As per IS 456:2000 clause 26.5.2.1 (

)


39




= = 144 mm2 ( (

)

= 373 mm2

)

(

)

Check for deflection: (

)

(

)

fs =

= 373 mm² = 356 mm² ( (

)

)

= = 208.06 Pt =

= 0.39

As per IS 456:2000, fig 4, page 38 Modification factor = 1.7 As per IS 456:2000, clause 23.2.1 ( ) ( ) ( )

= 26 =26 =

= 43

( )

So deflection is safe with provided depth.


40




Check for shear

= = 24.57 kN As per IS 456:2000 clause 40.1 τ

=

= 0.388 N/mm2

= = 0.41 N/mm2

τ

As per IS 456:2000 clause 40.2 Design shear strength of concrete =

τ = 0.53 N/mm 2

= 1.3 As per IS 456:2000, Table 20 Maximum shear stress,(τ ) τ

τ

(τ )

Check for cracking As per IS 456:2000, clause 43.1: 1. Steel provided is more than 0.12 percent 2. Spacing of main steel 3. Diameter of reinforcement Hence cracks will be within the permissible limits


41




6.6 DESIGN OF RCC DOME 6.6.1 GENERAL Concrete domes are generally preferred to cover circular tanks and for roofs of large span structures which are circular in shape such as sports area, mosques, and churches where un interrupted floor space is desirable. The spherical domes ed by ring beam at the base. The thickness of reinforced concrete spherical dome is generally not less than

of the diameter with the values of 50 mm-100 mm for domes in the range of

25m-50m respectively. The reinforcement in the dome is made up of wire mesh and concrete is placed in concentric rings over preformed framework or the dome can be formed by gunniting using micro concrete. 6.6.2 DESIGN OF RCC DOME -central portion above the 2ND floor of Mosque Data: Span of dome,

D = 4.23 m

Thickness of dome,

t = 120 mm

Central rise,

r=2m

M15, ie., fck = 15 N/mm2 Fe415, ie., fy = 415 N/mm2 Compressive strength of steel = 100 N/mm2

Load calculation: The self-weight of the slab = (0.12*1*1)25 = 3.00 kN/m2 Floor finishes

= 1 kN/m2

The total load,

= 4 kN/m2

Factored load

W= 6 kN/m2

Determination of stresses: 1) Meridianal thrust,

MT = MT =


(

)(

)

(R=

42

=

= 2.118 m)




MT = 8.85 kN/m

(sin =

,

= 64.15 )

Meridianal stress, MS =

=(

)

MS = 0.07375 N/mm2

cc

= 0.07375 N/mm2 = 4 N/mm2

(IS 456 : 2000 p.no:81)

Hence, it is safe 2) Hoop thrust,

HT = WR(cos

)

HT = 6*2.118*(cos64.15

)

HT = -3.308 kN/m

Hoop stress, HS =

=(

= -0.027 N/mm2

)

HS = -0.003 N/mm2

cc

= 4 N/mm2

Hence, it is safe But these stresses are very low. Therefore minimum of 0.30% of the dome area will be

adopted as the reinforcement. ie., minimum reinforcement,

Ast = 0.30%(bD) Ast =

*(1000*120)

Ast = 360 mm2 Spacing, s = (

)*1000 = (

)*1000

(assume, diameter = 12

mm) s = 314.16 mm ≈ 300mm c/c Provide main reinforcement of 12 mm diameter @ 300 mm c/c spacing. = 377 mm2

Therefore, actual area, Ast =

Design of ring beam: Hoop tension, Ft =

=

(

)

Ft = 20.14 kN


43




The reinforcement required, Ast = mm2

Ast = Number of bars, n =

=

= 1.78

4 numbers

(assume 12 mm diameter

bars) Provide 4 numbers of 12 mm diameter rods as ring beam reinforcement. Therefore, actual area, Ast = 4*113.10 = 452.40 mm2

Determination of the size of ring beam: The c/s area of the ring beam,

(

(

= 1.20

)

)

= 1.20

(m =

=

13.33) Ac = 11205.36 mm2

(assume square

beam) So, the size of ring beam is given as 150 mm*150 mm.


44




6.7 DESIGN OF WATER TANK 6.7.1 GENERAL The large container in which the water is made to occupy is popularly known as water tank. The main factors want to consider while constructing a water tank is its resistance against crack, corrosion, permeability. Water tightness is also an important criterion in water tanks. Usually richer mixes with M20, M30 concrete are used. The tensile stresses permitted in concrete are restricted to control cracking. In concrete as per IS: 3370, part II, 1965.

TYPES OF WATER TANK  Water tank resting on the ground  Underground tanks  Elevated water tanks on staging 6.7.2 DESIGN OF UNDERGROUND WATER TANK (rectangular) Data: Length

= 3.60m

Breadth

= 1.60m

Depth, H = 0.70m Weight of soil, w = 20 kN/m3 M20, ie.,

fck = 20 N/mm2

Fe415, ie.,

fy = 415 N/mm2

Check for design: 2.25 > 2.00 The long walls are designed as vertical cantilevers and the short walls are designed as the horizontal slabs spanning between long walls. Design of long walls: Vertical reinforcement:


45




The coefficient of earth pressure, ka =

(assume wet soil,

ka =

=6 )

= 0.81

When tank is full: The maximum pressure developed by wet soil, Ps = kawH Ps = 0.81*20*0.70 Ps = 11.34 kN/m2 The maximum water pressure developed, Pw = Ww*H Pw = 10*0.70 = 7.00 kN/m2 Therefore, the net pressure, Pn = 11.34 – 7.00 = 4.34 kN/m2 The maximum bending moment near the water surface, =

= 0.06 kNm

And the maximum bending moment away from the water surface =

= 0.14 kNm

When the tank is empty: There is no water pressure, hence Pw = 0 kN/m2 Therefore, the net pressure, Pn = 11.34 – 0.00 = 11.34 kN/m2 The maximum bending moment near the water surface, =

= 0.16 kNm

And the maximum bending moment away from the water surface =

= 0.37 kNm

The depth of the slab, M = 0.28*bD2 0.37*106 = 0.28*1000*D2 D = 36.35 mm 60 m d = 60 – (15) – ( )

(assume 10 mm diameter)

d = 40 mm


46




for away, Ast = Spacing, s = (

)*1000 = (

= 93.53 mm2

=

)1000 = 840 mm


Maximum spacing, s1 = 3d = 5*60 = 180 mm s2 = 300 mm Provide 10 mm diameter bars @ 180 mm c/c spacing (for 2 faces) = 436.33 mm2


for near, Ast = Spacing, s = (

)*1000 = (

= 40.44 mm2

=

)1000 = 1243 mm


Maximum spacing, s1 = 3d = 3*60 = 180 mm s2 = 300 mm Provide 8 mm diameter bars @ 180 mm c/c spacing (for 2 faces). Therefore, actual area, Ast =

= 280 mm2

Horizontal reinforcement: The horizontal reinforcement area, Ast = 0.30%(bD) Ast =

*(1000*60)

Ast = 180 mm2/2 = 90 mm2 Spacing, s = (

)*1000 = (

)1000 = 558.55 mm

(assume 8 mm

diameter)



= 280 mm2

47




Design of short walls: Horizontal reinforcement: The maximum pressure developed by wet soil = 11.34 kN/m2 The bending moment @ corners for short walls, = 0.46 kNm

=

M=

Therefore, the area of reinforcement, Ast = Spacing, s = (

= 116.28 mm2

=

)*1000 = (

)1000 = 675 mm


Maximum spacing, s1 = 3d = 3*60 = 180 mm s2 = 300 mm Provide 10 mm diameter bars @ 180 mm c/c spacing (for 2 faces). = 436.33 mm2


Vertical reinforcement: The horizontal reinforcement area, Ast = 0.30%(bD) Ast =

*(1000*60)


)*1000 = (

)1000 = 280 mm



= 280 mm2

Design of slab: Assume, the overall depth of slab, D = 100 mm Therefore, the effective depth, d = 100 – (15) – ( )


d = 80 mm


48




The dead load of the slab = (0.08*1*1)25 = 2.00 kN/m2 Assume, live load Assume, floor finish Therefore, total load

= 1.50 kN/m2 = 0.60 kN/m2 W = 4.10 kN/m2 = 2.48 kNm

=

The maximum bending moment, M =

Check for depth, M = Qbd2 2.48*106 = 1.21*1000*d2 d = 45.27 mm < 80 mm

hence, it is safe

Area of main reinforcement: Ast =

= 313.45 mm2

=

Spacing, s = (

)*1000 = (

)1000 = 360.82 mm

(assumed diameter is 12 mm)

Maximum spacing, s1 = 3d = 3*80 = 240 mm s2 = 300 mm Provide 12 mm diameter bars @ 240 mm c/c spacing. = 471.25 mm2


Area of distribution reinforcement: The distribution reinforcement area, Ast = 0.30%(bD) Ast =

*(1000*100)


)*1000 = (

)1000 = 168 mm




= 304.67 mm2

49




CHAPTER 7 SITE VISITS 17.1. SITE VISIT TO APOLLO BUILDERS MANJERI As part of this training, a site visit was conducted to the construction site of apollo builders, Manjeri. It is R.C.C framed structure having two towers. The tower 1 has G+15 floors and the tower 2 has G+ 14 floors. The construction techniques adopted for boring and concreting of Direct Mud Circulation (D.M.C) pile were observed. The hard rock available at the site was at a depth of 10m. The diameters of the piles are 600, 700 and 800 mm. The piles are driven up to a depth of 10 m were hard strata was available. The process of pile driving and concreting of piles were clearly observed and understood. D.M.C pile is Direct Mud Circulation pile where water jet is let through the piling chisel which comes out from bottom with mud. In D.M.C pile foundation the bentonite suspension is pumped into the bottom of the hole through the drill rods and it overflows at the top of the casing. The mud pump should have the capacity to maintain a velocity of 0.41 to 0.76m/s to float the cuttings.

Fig 7.1. D.M.C piling


50




Fig 7.2. Reinforcement in retaining wall

Fig 7.3. Reinforcement in column


51




7.2. SITE VISIT TO APOLLO BUILDERS, CALICUT. The second site visit was to the construction site of apollo builders, Calicut. It has got both the villa and the apartment. The apartment has 2 basement floor and the ground floor for car parking and 6 floors.

Fig.7.4. Reinforcement in beam


52




Fig 7.5. Sunken slab

In villas, foundation and reinforcement of roof slab construction was completed. For two way slabs, the spacing for top and bottom reinforcement is different while for one way slab, the top and bottom spacing are same. Framed section of beam columns were completed for villas.

Fig.7.6 Concealed beam


53




CHAPTER 8 CONCLUSION The industrial training, taken through a period of three months allowed me to gain ample exposure to various field practices in the analysis and design of multistoried buildings and also in various construction techniques used in the industry. The analysis was done using the software package STAAD Pro v8i and the drawing details in Auto CAD 2010. All the structural components were designed manually. The use of the software offers saving in time, It takes value on safer side than manual work. Hence manual design was adopted. The analysis and design was done according to standard specifications to the possible extend. The various difficulties encountered in the design process and the various constraints faced by the structural engineer in deg up to the architectural drawing were also well understood. This training helped to understand and analyse the structural problem faced by the construction industry. Site visits also gave me an exposure to the industry.


54




REFERENCES 1. S.Unnikrishna Pillai & Devadas Menon “Reinforced Concrete Design”. Tata McGraw-Hill Publishing Company Limited, New Delhi, 2003. 2. N Krishna Raju, “Advanced Reinforced Concrete Design”, C.B.S Publishers and Distributers, New Delhi,2004 3. P.C. Varghese, “Advanced Reinforced Concrete Design”, Prentice-Hall of India Private Limited, New Delhi, 2008. 4. Pankaj Agarwal & Manish Shrikhande “Earthquake Resistant Design of Structures”, Prentice-Hall of India Private Limited, New Delhi, 2007. 5. IS: 456-2000, “Indian Standard Plain and Reinforced Concrete-Code of Practice”, Bureau of Indian Standards, New Delhi. 6. IS: 875 (Part I)-1987, “ Indian Standard Code of Practice for Design Loads (Other than earthquake) for Building and Structures”, Bureau of Indian Standards, New Delhi. 7. IS: 875 (Part II)-1987, “ Indian Standard Code of Practice for Design Loads (Other than earthquake) for Building and Structures”,

Bureau of Indian Standards,

New Delhi. 8. IS: 875 (Part III)-1987, “ Indian Standard Code of Practice for Design Loads (Other than earthquake) for Building and Structures”,

Bureau of Indian Standards,

New Delhi 9. IS: 1893 (Part I)-2002, “ Indian Standard Criteria for earthquake Resistant Design of Structures”, Bureau of Indian Standards, New Delhi. 10. IS: 3370 (Part II)-1965, “Indian Standard Code of Practice for Concrete Structures for the Storage of Liquids”, Bureau of Indian Standards, New Delhi.


55




11. IS: 3370 (Part IV)-1967, “Indian Standard Code of Practice for Concrete Structures for the Storage of Liquids”, Bureau of Indian Standards, New Delhi. 12. SP 16: 1980, “Design Aids for Reinforced Concrete to IS:456-1978”, Bureau of Indian Standards, New Delhi. 13. SP 34: 1987, “Hand Book on Concrete Reinforcement and Detailing”, Bureau of Indian Standards, New Delhi. 14. IS 13920: 1993, “Indian Standard Code of Practice for Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces”, Bureau of Indian Standards, New Delhi.


56


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