CHAPTE R 1 INTRODUCTION
1.1.
PROJECT AIM
TO ANALYZE AND DESIGN AN OVERHEAD TANK FOR THE USAGE OF COLLEGE AND HOSTEL USING STAAD PRO.
1.2.
SCOPE
The main scope of this project is to apply class room knowledge in the real world by designing an overhead tank. These tanks require large and clear areas unobstructed by the columns. Overhead water tanks are used for domestic water storage and commercial water purposes to maintain flow of water to the general usage usa ge and other water requiring appliances.
1.3
GENERAL
STAAD Pro. V8i is the most popular structural engineering software product for model generation, analysis and multi-material design. It has an intuitive, user-friendly GUI, visualization tools, powerful analysis and design facilities and seamless integration to several other modeling and design software products. The software is fully compatible with all Windows operating systems but is optimized for Windows 7.
The ultimate power tool for Computerized Structural Engineering For static or dynamic
analysis of bridges, containment structures, embedded structures (tunnels and culverts), pipe racks, steel, concrete, aluminum or timber buildings, transmission towers, stadiums or any other simple or complex structure, STAAD Pro has been the choice of design professionals around the world for their specific analysis anal ysis needs.
Our project involves analysis and design of overhead tank using a very popular designing software STAAD Pro (V8i).
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We have chosen STAAD Pro because of its following advantages:
easy to use interface,
conformation with the Indian Standard Codes, versatile nature of solving any type of problem,
accuracy of the solution.
Fig. 1.1 : Staad Pro Outlook
STAAD.Pro consists of the following:
The STA ST A A D .Pr .P r o G r aphical hical User User I nte nter face face: It is used to generate the model, which can then be analyzed using the STAAD engine. After analysis and design is completed, the GUI can also be used to view the results graphically.
The STAAD analysis and design engine: It is a general-purpose calculation engine for structural analysis and integrated Steel, Concrete, Timber and Aluminum design. To start with we have solved some sample problems using STAAD Pro and checked the accuracy of the results with manual calculations. The results were to satisfaction and were accurate. In the
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initial phase of our project we have done calculations regarding loadings on buildings and also considered seismic and wind loads.
Structural analysis comprises the set of physical laws and mathematics required to study and predicts the behavior of structures. Structural analysis can be viewed more abstractly as a method to drive the engineering design process or prove the soundness of a design without a dependence on directly testing it.
To perform an accurate analysis a structural engineer must determine such information as structural loads, geometry, support conditions, and materials properties . The results of such an analysis typically include support reactions, stresses and displacements. This information is then compared to criteria that indicate the conditions of failure. Advanced structural analysis may examine dynamic response, stability and non-linear behavior.
The aim of 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 all the loads and deformations of normal construction and use and have adequate durability and adequate resistance to the effects of seismic and wind. Structure and structural elements shall normally be designed by Limit State Method. Account should be taken of accepted theories, experiment and experience and the need to des ign for durability.
Design, including design for durability, construction and use in service should be considered as a whole. The realization of design objectives requires compliance with clearly defined standards for materials, production, workmanship and also maintenance and use of s tructure in service.
The design of the building is dependent upon the minimum requirements as prescribed in the Indian Standard Codes. The minimum requirements pertaining to the structural safety of buildings are being covered b y way of laying down minimum design loads which have to be assumed for dead loads, imposed loads, and other external loads, the structure would be required to bear. Strict conformity co nformity to loading standards recommended in this code, i t is hoped, will not only ensure the structural safety of the buildings which are being designed.
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CHAPTE R 2 AB A B OUT TH E PR OJ OJE E C T
2.1
ABOUT THE PROJECT
This is an estimated project whose design values can be used for the construction of overhead tank for the college and hostel, GCET Jammu along with other necessary utilities.
This document pertains to the structural designs carried out for a part of above said residential township project for various structures. The development is in the seismic Zone – Zone – IV. IV. The basic wind speed at location of the development is 100 m/s. SBC of soil according to soil investigations is 200 KN/m 2. The design parameters considered are as per Indian Standard Code of practice.
Fig. 2.1 : Rendering View of the t he Overhead Tank
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2.2
STATEMENT OF THE PROJECT
The water demand for various purposes to which the project satisfies are as follows:
NO. OF STUDENTS
Intake capacity
=
320 * 4
Hostel Living students
=
1280 students
=
35% of total students
=
35/100 * 1280
=
448 students
No. of staff members + other employees
=
(500 students approx.)
500 members
WATER DEMAND FOR VARIOUS USES:
Day scholars water demand Hostel water demand =
=
50 lphd = 50 * 800 = 40000 litres per day
150 lphd = 150 * 500 = 75000 litres per day
Garden watering demand = 100 litres per day
CLEANING WATER DEMAND:
Civil + Mechanical Block
=
2 * 50
=
100 litres per day
Computer + Electrical + Electronics Block
=
75 litres per day
Common Lecture Hall
=
100 litres per day
Workshop
=
30 litres per day
Administrative Block
=
75 litres per day
Hostel Water Consumption
=
5000 litres per day (@10 litres
=
5380 (litres per day)
per head per day)
TOTAL
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Garden Water Demand
=
100 litres per day
Labs (Civil+ Chemistry) Water Demand
=
30 litres per day
Fire Demand
=
5% of total capacity
Pantry for Hostel
=
15 litres per head per day
=
7500 litres per day
=
30 litres per head per day
=
(30 * 500) litres per day
=
15000 litres per day
Staff members Water Demand
TOTAL CAPACITY
=
1,52,010 litres per day
Applying 20% capacity extra for miscellaneous purposes.
DESIGN CAPACITY
=
1,80,000 litres
MATERIAL PROPERTIES:
CONCRETE All components unless specified in design:
M30 grade all
STE ST E E L HYSD reinforcement of grade Fe 500 confirming to IS: 1786 is used throughout.
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CHAPTE R 3 DESI GN PARAM PA RAME E T E RS
3.
DESIGN PARAMETERS
The program contains a number of parameters that are needed to perform design as per IS: 13920. It accepts all parameters that are needed to perform design as per IS: 456. Over and above it has some other parameters that are required only when designed is performed as per IS: 13920. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed by this manual contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as Millimeter and Newton before performing the concrete design.
3.1.
BEAM DESIGN
Beams are designed for flexure, shear and torsion. If required the effect of the axial force may be taken into consideration. For all these forces, all active beam loadings are prescanned to identify the critical load cases at different sections se ctions of the beams. For design to be performed as per IS: 13920 the width of of the member shall not be less than 200mm.
Also the member shall preferably have a width-to depth ratio of more than 0.3.
Design for Flexure:
Design procedure is same as that for IS: 456. However while designing following criteria are satisfied as per IS: 13920 1.
The minimum grade of concrete shall preferably be M25.
2.
Steel reinforcements of grade Fe415 or less only shall be used.
3.
The minimum tension steel ratio on any face, at any section, is given by:
ρmin =
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The maximum steel r atio atio on any face, at any section, is given by ρmax = 0.025. 4.
The positive steel ratio at a joint face must be at least equal to half the negative steel at that face.
5.
The steel provided at each of the top and bottom face, at any section, shall at least be equal to one-fourth of the maximum negative moment steel provided at the face of either joint.
Design for Shear:
The Shear force to be resisted by vertical hoops is guided by the IS 13920:1993 13920:1993 revision. Elastic sagging and hogging moments of resistance of the beam section at ends are considered while calculating shear force. Plastic sagging and hogging moments of resistance can also be considered for shear design if PLASTIC parameter is mentioned in the input file. Shear reinforcement is calculated to resist both shear forces and torsional moments.
3.2
COLUMN DESIGN
Columns are designed for axial forces and biaxia l moments per IS 456:2000. Columns are also designed for shear forces. All major criteria for selecting longitudinal and transverse reinforcement as stipulated by IS: 456 have been taken care of in the column design of STAAD. However following clauses have been satisfied to incorporate provisions of IS: 13920
1.
The minimum grade of concrete shall preferably be M25.
2.
Steel reinforcements of grade Fe415 or less only shall be used.
3.
The minimum dimension of column member shall not be less than 200 mm.For columns having having unsupported unsupported length exceeding exceeding 4m, the shortest dimension dimension of column shall not be less than 300 mm.
4.
The ratio of the shortest cross-sectional dimension to the perpendicular dimension shall preferably be not less than 0.
5.
The spacing of hoops shall not exceed half the least lateral dimension of the column, except where special confining reinforcement is provided.
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6.
Special confining reinforcement shall be provided over a length l o from each joint face, towards mid span, and on either side of any section, where flexural yielding may occur.
The length lo shall not be less than a) larger lateral dimension of the member at the section where yielding occurs, b) 1/6 of clear span of the member, and c) 450 mm.
7.
The spacing of hoops used as special confining reinforcement shall not exceed of minimum member dimension but need not be less than 75 mm nor > 100 mm.
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CHAPTE R 4 DE SI GN OPER OPER ATI ONS
4.
DESIGN OPERATIONS
STAAD contains a broad set of facilities for designing structural members as individual components of an analyzed structure. The member design facilities provide the user with the ability to carry out a number of different design operations.
These facilities may design problem. The operations to perform a d esign are:
Specify the members and the load cases to be considered in the design.
Specify whether to perform code checking or member selection.
Specify design parameter values, if different from the default values.
Specify whether to perform member selection by optimization.
These operations may be repeated by the user any number of times depending upon the design requirements. Earthquake motion often induces force large enough to cause inelastic deformations in the structure. If the structure is brittle, sudden failure could occur. But if the structure is made to behave ductile, it will be able to sustain the earthquake effects better with some deflection larger than the yield deflection by absorption of energy. Therefore ductility is also required as an essential element for safety from sudden collapse during severe shocks. STAAD has the capabilities of performing concrete design as per IS: 13920. While designing it satisfies all provisions of IS: 456 - 2000 and IS: 13920 for beams and columns.
4.1
GENERAL COMMENTS
This section presents some general statements regarding the implementation of Indian Standard code of practice (IS: 800 - 1984) for structural steel design in STAAD. The design philosophy and procedural logistics for member selection and code checking are based upon the principles of allowable stress design. Two major failure modes are recognized:
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failure by overstressing, and
failure by stability considerations.
The flowing sections describe the salient features of the allowable stresses being calculated and the stability criteria being used. Members are proportioned to resist the design loads without exceeding the allowable stresses and the most economic section is selected on the basis of least weight criteria. The code checking part of the program checks stability and strength requirements and reports the critical loading condition and the governing code criteria. It is generally assumed that the user will take care of the detailing requirements like provision of stiffeners and check the local effects e ffects such as flange buckling and web crippling.
Allowable Stresses: Stresses:
The member design and code checking in STAAD are based upon the allowable stress design method as per IS: 800 (1984). It is a method for proportioning structural members using design loads and forces, allowable stresses, and design limitations for the appropriate material under service conditions. It would not be possible to describe ever y aspect of IS: 800 in this manual. This section, however, will discuss the salient features of the allowable stresses specified by IS: 800 and implemented in STAAD. Appropriate sections of IS: 800 will be referenced during the discussion of various types of allowable stresses.
Multiple Analyses:
Structural analysis/design may require multiple analyses in the same run. STAAD allows the user to change input such as member properties, support conditions etc. in an input file to facilitate multiple analyses in the same run. Results from different analyses may be combined for design purposes. For structures with bracing, it may be necessary to make certain members inactive for a particular load case and subsequently activate them for another. STAAD provides an INACTIVE facility for this type of analysis.
4.2
POST PROCESSING FACILITIES:
All output from the STAAD run may be utilized for further processing by the STAAD.Pro GUI.
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4.3
STABILITY REQUIREMENTS:
Slenderness ratios are calculated for all members and checked against the appropriate maximum values. IS: 800 summarize the maximum slenderness ratios for different types of members. In STAAD implementation of IS: 800, appropriate maximum slenderness ratio can be provided for each member. If no maximum slenderness ratio is provided, compression members will be checked against a maximum value of 180 and tension members will be checked against a maximum value of 400.
4.4
DEFLECTION CHECK:
This facility allows the user to consider deflection as criteria in the CODE CHECK and MEMBER SELECTION processes. The deflection check may be controlled using three parameters. Deflection is used in addition to other strength and stability s tability related criteria. The local deflection calculation is based on the latest analysis results.
4.5
EARTHQUAKE COLLAPSE CHECK:
This checks at each column / beam interface, the program checks that the capacity of the column exceeds the total capacity of all beams that connect to it. The earthquake check only uses the results from Design Groups that have Des ign Briefs from the selected Design Desi gn Code.
4.6
CODE CHECKING:
The purpose of code checking is to verify whether the specified s ection is capable of satisfying satis fying applicable design code requirements. The code checking is based on the IS: 800 (1984) requirements. Forces and moments at specified sections of the members are utilized for the code checking calculations. Sections may be specified using the BEAM parameter or the SECTION command. If no sections are specified, the code checking is based on forces and moments at the member ends.
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CHAPTE R 5 PROJE PRO JE CT ANALYSI ANALYSI S
5.
ANALYSIS OF OVERHEAD TANK USING STAAD PRO V8i
Fig. 5.1 : Isometric View of the Designed Overhead Tank
This overhead tank is designed for 1,80,000 litres for the supply of water to college and hostel students of GCET Jammu having the following specifications:
Take D = Diameter of the water tank
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Average Depth
=
0.75 D
Volume of the water reservoir
=
180000 litres
=
180 m3
* 0.75 D
=
180
D
=
6.74 m
D
=
8.00 m
=
0.75 * 6.74
=
5.00 m
=
D/6
=
1.5 m (approx.)
=
(D/22 + r 2) / 2r
=
(16 + 2.25) / ( 2 * 1.5 )
=
6.0833 m
Diameter of the top dome
=
2 * 6.0833
=
Central rise of the top dome
=
D/6
5/6
=
0.83 m (approx.)
=
(D/2 2 + r 2) / 2r
=
(5/22 + 0.832) / (2 * 0.83)
=
4.18 m
=
2 * 4.18
4
∗
2
Taking
Height of the cylindrical portion of the beam
Central rise of the top dome
Radius of the top dome
Radius of the bottom dome
Diameter of the bottom dome
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=
=
8/6
=
12.167 m
8.36 m
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Total height of the overhead tank
=
20m
Total height of staging
=
12m
Height of circular portion of water reservoir
=
5m
Height of trapezoidal portion of water reservoir
=
1.5m
Diameter of circular portion of water reservoir
=
8m
Diameter of staging tube
=
5m
5.1
GENERATION OF THE MEMBER PROPERTY:
Fig. 5.2 : Generation of the Property of the top dome plate
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Fig. 5.3 : Generation of the Property of the Ring Beams
Generation of member property can be done in STAAD.Pro by using the window as shown above. The member section is selected and the dimensions have been specified.
The properties of various elements used are as follows :
1. Top Dome Plate
Concrete
150mm thick
2. Circular Region Plate
Concrete
250mm thick
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5.2
3. Trapezoidal Plate
Concrete
250mm thick
4. Ring Beams
Concrete
500 x 500 mm
5. Staging Tube
Concrete
250mm thick
SUPPORTS:
Fig. 5.4 : Fixed Support at Bottom The base supports of the structure were assigned as fixed. The supports were generated using the STAAD.Pro support generator.
5.3
MATERIALS FOR THE STRUCTURE:
The materials for the structure were specified as concrete with their various constants as per standard IS code of practice.
5.4
LOADING:
The loadings were calculated partially manually and rest was generated using STAAD.Pro load generator. The loading cases were categorized as:
1.
Seismic load
2.
Wind load
3.
Dead load
4.
Live load
5.
Load combinations
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5.4.1
SEISMIC LOAD:
The seismic load values were calculated as per IS 1893-2002. STAAD.Pro has a seismic load generator in accordance with the IS code mentioned.
Fig. 5.5 : STAAD utilizes the following procedure to generate the lateral seismic loads
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5.4.2
WIND LOAD:
The wind load values were generated by the software itself in accordance with IS 875. Under the define load command section, in the wind load category, the definition of wind load was supplied. The wind intensities at various heights were calculated manually and feed to the software. Based on those values it generates the wind load at different floors. We consider ASCE-7 for wind loads with basic wind speed of 50 kmph.
Fig. 5.6 : Window showing Wind Force action acti on on Overhead Tank
5.4.3
DEAD LOAD:
5.4.3.1
SELF-WEIGHT:
The self-weight of the structure can be generated by STAAD.Pro itself with the self-weight command given in the load case column.
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5.4.3.2
DEAD LOAD FROM WALLS:
Dead load from walls can also be generated by STAAD.Pro by specifying the wall thickness. Calculation of the load per metre was done considering the weight of wall.
Weight of the wall = density of the wall x volume of wall per unit run
REGION
THICKNESS
HEIGHT
DENSITY
LOAD
(m)
(m)
(kN/m3)
(kN/m)
TOP DOME
0.15
0.1
25
0.375
CIRCULAR
0.25
5
25
31.25
TRAPEZOIDAL
0.25
0.2
25
1.25
STAGING TUBE
0.25
12
25
75
TOP RING
0.5
0.5
25
6.25
BOTTOM RING
0.5
0.5
25
6.25
Fig. 5.7 : Window showing the Self-weight of Overhead Tank
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5.5
LOAD COMBINATION:
The structure has been analyzed for auto load combination considering all the previous loads in proper ratio and generates load combination code as per Indian code under load combination category of general structures.
5.5.1
Combination Rules:
For each Code/Category, each load category can be set with one of three rules:
a) Combine all cases together b) Separate combination for each case c) All possible combinations.
It will take a load combination of earthquake load, wind load, self-weight, dead load &live loads.
Fig. 5.8 : Auto Load Combination Window
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Fig. 5.9 : GUI showing the analyzing window
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CHAPTE R 6 PROJE PRO JE CT DE SI GN
6.1
DESIGN OF OVERHEAD TANK USING STAAD PRO:
The structure was designed for concrete in accordance with IS: 456 codes. The parameters such as Fy, Fck , etc were specified. The window shown below is the input window for the design purpose. Then it has to be specified which members are to be designed as beams and which member are to be designed as columns.
6.2
DESIGN PARAMETERS
Fig. 6.1 : Input Windows for Design Purpose
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FC:
Compressive Strength of concrete
FYMAIN:
Yield Strength for main reinforcement steel (For slabs, it the reinforcement used in both directions)
FYSEC:
6.3
Yield Strength for main reinforcement steel (Only used in beam design)
DESIGN COMMANDS:
DESIGN BEAM :
Design beams for flexure, shear and torsion
DESIGN COLUMN :
Design columns for axial load plus biaxial bending
TAKE OFF :
Print the total volume of concrete and weight of steel Reinforcement for the beams, columns and elements designed.
Fig. 6.2 : Design Specifications in STAAD.Pro
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Fig. 6.3 : STAAD Pro Command Input File
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CHAPTE R 7 AN A N A L Y SI S AND AN D DE D E SI G N RE R E SU SUL L TS
7.
ANALYSIS AND DESIGN RESULTS:
7.1
TOTAL APPLIED LOAD 1 (SEISMIC (SEISMIC LOAD)
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7.2
TOTAL APPLIED LOAD 2 (WIND (WIND LOAD)
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7.3
APPLIED LOAD 3 (DEAD LOAD) LOAD) TOTAL APPLIED
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7.4
CONCRETE DESIGN
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Fig. 7.1 : Shear Force Diagram of the Beam 1591
Fig. 7.2 : Bending Moment Diagram of the Beam 1591
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Fig. 7.3 : Reinforcement Detailing of the Beam Section 1591
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Fig. 7.4 : Shear Force Diagram of the Beam 1623
Fig. 7.5 : Bending Moment Diagram of the Beam 1623
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Fig. 7.6 : Reinforcement Detailing of the Beam Section 1623
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7.5
REINFORCEMENT REINFORCEMENT OF TOP DOME :
Hence, provide longitudinal reinforcement = 138.00 mm 2 / metre and transverse reinforcement = 138.00 mm 2 / metre.
7.6
REINFORCEMENT REINFORCEMENT OF THE OVERHEAD TANK (except top dome) :
Hence, provide longitudinal reinforcement = 258.00 mm 2 / metre and transverse reinforcement = 258.00 mm 2 / metre.
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CHAPTE R 8 POST PO ST PROC PROCE E SS SSII NG OF PRO PROJE JE CT
8.
POST PROCESSING MODE
Fig. 8.1 : Window showing Post processing mode of design
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Fig. 8.2 : Max Absolute Plate Stress Contours showing Structural Diagrams
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Fig. 8.3 : Windows showing various graphs
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CHAPTE R 9 F OUNDAT NDATII ON DE SI GN
9.
FOUNDATION DESIGN:
Fig. 9.1 : GUI showing the foundation design of designed project
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The overhead tank is to be designed for mat foundation having the following properties:
9.1
1. Depth of the foundation below GL (Ground Level)
=
5.00 m
2. Meshing Type
=
Triangular
3. Radius of circular footing
=
4.00 m
4. Subgrade Modulus
=
0.001 kip/in 2/in
ANALYSIS OF THE FOUNDATION
Fig. 9.2 : Max Absolute Stresses on the Foundation
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Fig. 9.3 : Window showing Reinforcement Zoning for Longitudinal Bottom
Area of steel Provided
=
6000 mm2
Hence, provide 20 mm bars @ 50 mm c-c spacing
9.2
DESIGN OUTPUT :
Top of Mat Longitudinal Direction Bottom of Mat Longitudinal Direction Zone:- 1 Governing Moment(MGOV)= -8356.881(kN-m/m) For FC <4.0 Effective Depth =
= 4.936 (m)
Limit Moment of Resistance (M umax) = 83915.495 (kNm) = MGOV<= Mumax hence OK Steel Required
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Calculated Area of Steel = 6000.000 (mm2) Minimum Area of Steel = 6000.000 (mm2) Provided Area of Steel = 6000.000 (mm2)
Reinforcement Details Bar No= 20 Maximum Spacing(Smax)(User Specified) = 500.000(mm) Minimum Spacing(Smin)(User Specified) = 50.000(mm) Actual Spacing (S) = 50(mm) Smin<= S <= S max
---------------------------------------
Bottom of Mat Transverse Direction Zone:- 1 Governing Moment(MGOV)= -6508.275(kN-m/m) For FC <4.0 Effective Depth =
= 4.928 (m)
Limit Moment of Resistance (M umax) = 83643.704 (kNm) = MGOV<= Mumax hence OK Steel Required Calculated Area of Steel = 6000.000 (mm2) Minimum Area of Steel = 6000.000 (mm2) Provided Area of Steel = 6000.000 (mm2)
Reinforcement Details Bar No= 20 Maximum Spacing(Smax)(User Specified) = 500.000(mm) Minimum Spacing(Smin)(User Specified) = 50.000(mm) Actual Spacing (S) = 50(mm) Smin<= S <= S max
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CH APTE R 10 10 OVE RH E AD COLUMN COLUMN TYPE TYPE TANK 10.1 OVERHEAD COLUMN TYPE TANK Overhead column type tank are used in today world to increase the safety of the structure against failing. Current design of circular shaft type staging of elevated water tanks are extremely vulnerable under earthquake forces. Shaft type staging contains poor ductility of thin shell section and in addition to that it has lack of load paths and toughness. Hence, the overhead column type tank is more resistant to earthquake and seismic forces.
Fig. 10.1 : Render View of the Column Type Overhead Tank
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Fig. 10.2 : Geometric View of the Colu Column mn T
43
e Over Overhe head ad Tank Tank
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10.2
GENERATION OF MEMBER PROPERTY
Fig. 10.3 : Plate Thickness of the Circular Tank
10.3
LOADINGS
The loadings of the column type overhead tank is same as described in shaft type overhead tank.
Fig. 10.4 : Loading Diagram of Column Overhead Tank
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10.4
ANALYSIS
Fig. 10.5 : GUI showing the anal yzing window
10.5
DESIGN PARAMETERS
All the design parameters of the column type of overhead tank is same as shaft type overhead tank except the characteristic strength of the cement is M40.
Fig. 10.6 : Window showing the strength of cement
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10.6
PLATE STRESS CONTOURS
Fig. 10.7 : Max Absolute Plate Stress Contours of the Column Type Overhead Tank
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CH APTE R 11 11 AN A N A L Y SI S RE R E SU SUL L TS OF COL C OLUM UMN N OHT OH T 11.1
TOTAL APPLIED LOAD 1 (SEISMIC LOAD)
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11.2
TOTAL APPLIED LOAD 3 (DEAD LOAD)
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11.3
CONCRETE DESIGN
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Fig. 11.1 : Shear Force Diagram of the Column Section 1221
Fig. 11.2 : Bending Moment Diagram of the Column Section 1211
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Fig. 11.3 : Reinforcement Detailing of the Column Section 1221
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Fig. 11.4 : Shear Force Diagram of the Ring Beam Section 1282
Fig. 11.5 : Bending Moment Diagram of the Ring Beam Section 1282
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Fig. 11.6 : Reinforcement Detailing of the Ring Beam Section 1282
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11.4
REINFORCEMENT REINFORCEMENT OF THE TOP DOME
Hence, provide longitudinal reinforcement = 138 mm 2 / metre and transverse reinforcement = 138 mm2 / metre.
11.5
REINFORCEMENT REINFORCEMENT OF THE WATER TANK (except top dome)
Hence, provide longitudinal reinforcement = 438 mm 2 / metre and transverse reinforcement = 438 mm2 / metre.
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MINOR PROJECT
CH APTE R 12 12 F OUNDATI ON DE SI GN OF OF CO COLUMN LUMN OH OH T 12.
FOUNDATION DESIGN
Fig. 12.1 : Window showing the Foundation of Column OHT
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MINOR PROJECT
The overhead tank is to be designed for ISOLATED FOOTING having the following properties:
1. Unit Weight of Concrete
=
30 N/mm2
2. Yield Strength of Steel
=
500 N/mm2
3. Soil Type
=
Drained Condition
4. Unit Weight of Soil
=
22 kN/m3
5. Bearing Capacity of Soil
=
100 kN/m2
12.2
DIMENSIONS OF THE ANALYSED FOOTINGS
Hence, provide ISOLATED footings of φ12 mm at a spacing of 60 mm centre to centre.
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MINOR PROJECT
12.3
DESIGN OUTPUT
FOR ISOLATED FOOTING
Fig. 12.2 : Reinforcement Detailing of Isolated Footing
Footing Size Initial Length (L o) = 1.000 m Initial Width (W o) = 1.000 m Uplift force due to buoyancy = 0.000 kN Effect due to adhesion = 0.000 kN Area from initial length and width, A o =Lo X Wo = 1.000 m2 2 Min. area required from bearing pressure, A min min =P / qmax = 24.458 m
Note: Amin is an initial estimation. P = Critical Factored Axial Load(without self weight/buoyancy/soil). qmax = Respective Factored Bearing Capacity.
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Final Footing Size Length (L2) =
5.400
m
Governing Load Case :
# 11
Width (W2) =
5.400
m
Governing Load Case :
# 11
Depth (D2) =
0.508
m
Governing Load Case :
# 11
Area (A 2) =
29.160
m2
-----------------------------------------------------Pressures at Four Corner
Load Case
Pressure at corner 1 (q1) (kN/m2)
Pressure at corner 2 (q2) (kN/m2)
Pressure at corner 3 (q3) (kN/m2)
Pressure at corner 4 (q4) (kN/m2)
Area of footing in uplift (Au) (m2)
11
86.6277
98.7959
98.7959
86.6276
0.000
11
86.6277
98.7959
98.7959
86.6276
0.000
11
86.6277
98.7959
98.7959
86.6276
0.000
11
86.6277
98.7959
98.7959
86.6276
0.000
If A u is zero, there is no uplift and no pressure adjustment is necessary. Otherwise, to account for uplift, areas of negative pressure will be set to zero and the pressure will be redistributed to remaining corners.
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MINOR PROJECT
Summary of adjusted Pressures at Four Corner Pressure at corner 1 (q1)
Pressure at corner 2 (q2)
Pressure at corner 3 (q3)
Pressure at corner 4 (q4)
(kN/m2)
(kN/m2)
(kN/m2)
(kN/m2)
11
86.6277
98.7959
98.7959
86.6276
11
86.6277
98.7959
98.7959
86.6276
11
86.6277
98.7959
98.7959
86.6276
11
86.6277
98.7959
98.7959
86.6276
Load Case
Details of Out-of-Contact Area (If Any) Governing load case = N/A Plan area of footing = 29.160 sq.m Area not in contact with soil = 0.000 sq.m % of total area not in contact = 0.000% -----------------------------------------------------Check For Stability Against Overturning And Sliding -
Factor of safety against sliding
Factor of safety against overturning
Load Case No.
Along XDirection
Along Z-Direction
About X-Direction
About Z-Direction
1
11.626
2821871.163
12381901.039
20.920
3
674.758
220465831.417
34646616.872
2631.951
4
629.391
231348176.512
32285313.683
2454.993
5
652.075
191748897.142
33460788.309
2543.472
6
652.075
191748897.142
33460788.309
2543.472
7
26.426
6368227.195
17492285.575
46.843
8
9.618
2353147.174
24414479.249
17.558
9
629.391
231348176.512
32285313.683
2454.993
10
629.391
231348176.512
32285313.683
2454.993
11
25.790
6229206.430
17047266.690
45.715
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12
9.016
2208176.476
22851340.222
16.458
13
19.527
4725768.905
15278213.863
34.823
14
3.328
813631.898
5488340.189
6.040
Critical Load Case And The Governing Factor Of Safety For Overturning and Sliding X Direction Critical Load Case for Sliding along X-Direction : 14 Governing Disturbing Force : -54.765 kN Governing Restoring Force : 182.254 kN Minimum Sliding Ratio for the Critical Critical Load Case : 3.328 Critical Load Case for Overturning about about X-Direction : 0 Governing Overturning Moment : 0.000 kNm Governing Resisting Moment : 0.000 kNm Minimum Overturning Ratio for the Critical Load Case 1000000.000 : Critical Load Case And The Governing Factor Of Safety For Overturning Ov erturning and Sliding Z Direction Critical Load Case for Sliding along along Z-Direction : 14 Governing Disturbing Force : 0.000 kN Governing Restoring Force : 182.254 kN Minimum Sliding Ratio for the Critical Load Case : 813631.898 Critical Load Case Case for Overturning about Z-Direction : 14 Governing Overturning Moment : 162.926 kNm Governing Resisting Moment : 984.151 kNm Minimum Overturning Ratio for the Critical Load Case 6.040 :
Moment Calculation Check Trial Depth against moment (w.r.t. X Axis)
Critical Load Case Case = #11
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= 0.452 m
Effective Depth =
Governing moment (Mu) = 1219.578 kNm As Per IS 456 2000 ANNEX G G-1.1C = 0.479107
Limiting Factor1 (K umax umax) = Limiting Factor2 (R umax umax) = Limit Moment Of Resistance (Mumax) =
= 3444.291146 kN/m2 = 3799.815884 kNm Mu <= Mumax hence, safe
Check Trial Depth against moment (w.r.t. Z Axis)
Critical Load Case
= #11 = 0.452 m
Effective Depth =
Governing moment (Mu) = 1282.934 kNm As Per IS 456 2000 ANNEX G G-1.1C = 0.479107
Limiting Factor1 (K umax umax) =
= 3444.291146 kN/m2
Limiting Factor2 (R umax umax) =
= 3799.815884 kNm
Limit Moment Of Resistance (Mumax) =
Mu <= Mumax hence, safe
Shear Calculati Calculation on Check Trial Depth for one way shear (Along X Axis) (Shear Plane Parallel to X Axis)
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Critical Load Case = #11 DX = 0.452 m Shear Force(S) = 845.161 kN Shear Stress(T v) = 346.263783 346.263783 kN/m2 Percentage Of Steel(Pt) = 0.3414 As Per IS 456 2000 Clause 40 Table 19 Shear Strength Of Concrete(T c) = 417.029 kN/m2 Tv< Tc hence, safe
Check Trial Depth for one way shear (Along Z Axis)
Critical Load Case = #11
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DZ = 0.452 m Shear Force(S) = 885.353 kN Shear Stress(T v) = 362.730590 362.730590 kN/m2 Percentage Of Steel(Pt) = 0.3236 As Per IS 456 2000 Clause 40 Table 19 Shear Strength Of Concrete(T c) = 407.600 407.600 kN/m2 Tv< Tc hence, safe
Check Trial Depth for two way shear
Critical Load Case = #11 Shear Force(S) = 2315.931 2315.931 kN Shear Stress(T v) = 1065.670 kN/m2 As Per IS 456 2000 Clause 31.6.3.1 K s =
= 1.000
Shear Strength(Tc)=
= 1250.0000 kN/m2
K s x Tc = 1250.0000 kN/m2 Tv<= K s x Tc hence, safe
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Reinforcement Calculation Calculation of Maximum Bar Size
Along X Axis Bar diameter corresponding to max bar size (d b) = 32 mm As Per IS 456 2000 Clause 26.2.1
Development Length(ld) = Allowable Length(ldb) =
= 1.289 m = 2.275 m
ldb >=ld hence, safe Along Z Axis Bar diameter corresponding to max bar size(db) = 32 mm As Per IS 456 2000 Clause 26.2.1
Development Length(ld) = Allowable Length(ldb) =
= 1.289 m = 2.275 m ldb >=ld hence, safe
Bottom Reinforcement Design Along Z Axis
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Selected bar Size (d b) = Ø10 Minimum spacing allowed (Smin) = 50.000 mm Selected spacing (S) = 52.900 mm Smin <= S <= Smax and selected bar size < selected maximum bar size... The reinforcement is accepted.
As Per IS 456 2000 Clause 26.5.2.1
Critical Load Case = #11 Minimum Area of Steel (A stmin stmin) = 3285.360 mm2 Calculated Area of Steel (A st st) = 7897.468 mm2 Provided Area of Steel (A st,Provided st,Provided) = 7897.468 mm2 A stmin area is accepted stmin<= A st,Provided st,Provided Steel area
Based on spacing reinforcement increment; provided reinforcement is Ø10 @ 50.000 mm o.c.
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CH APTE R 13 13 COMPARISON
S.NO.
1.
2.
3.
4.
5.
6.
SHAFT TYPE OVERHEAD
COLUMN TYPE OVERHEAD
TANK
TANK
The characteristic strength of the The characteristic strength of the cement is M30.
cement is M40.
Plate Thickness of the Circular Tank
Plate Thickness of the Circular Tank
is 250 mm.
is 400 mm.
Max. Absolute Plate Stresses acting is Max. Absolute Plate Stresses acting 1.6 N/mm2.
is 2.98 N/mm2.
Cross-Section of the Ring Beam
Cross-Section of the Ring Beam
Section is (500*500) mm.
Section is (750*750) mm.
The Foundation used for the design is
The Foundation used for the design
Mat Foundation.
is Isolated Footing.
The Longitudinal Reinforcement of
The Longitudinal Reinforcement of
the Plate Section of tank is 258 mm2 the Plate Section of tank is 438 mm2
7.
per metre.
per metre.
The area of steel in ring beam cross-
The area of steel in ring beam cross-
section is 1608.5 mm2. ( 8 no’s no’s 16 φ section is 2305.927 mm2. ( 6 no’s 16 16 bars) .
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φ bars + bars + 14 no’s 10 φ bars )
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MINOR PROJECT
Current designs of circular shaft t ype staging of elevated tanks are extremely vulnerable under earthquake forces. In 2001 Bhuj earthquake, another illustr ation of this vulnerability had been seen when many water tank with shaft staging suffered damage as distant as 100 km from from the epicenter. Shaft type staging contains poor ductility of thin shell sections and in addition to that it has lack of redundancy of load paths and toughness. Lateral strength analysis of number of damaged shaft staging clearly show that all of them are either met or exceeded the requirements of IS: 1893(1984), however, they were all f ound to be deficient when compared with the requirements of IBC in similar seismic exposure conditions. IS: 1893(1984) design forces are inexcusably low for the systems which do not have enough ductility or redundancy. The current design parameters seismic codes for elevated tanks result in extremely vulnerable shaft type supporting structures as evidenced in the 2001 Bhuj earthquake. Supporting shafts developed flexural-tension cracks were observed in tanks as far as 100 km away awa y from epicenter regions despite the fact that most had lateral strength far greater that that specified by IS:1893(1984). Multipurpose elevated water storage facility of present invention includes a pillar supporting the elevated water storage tanks t anks which has the flute portion, by rendering overall facil ity more efficiently and aesthetically pleasing. The fluted portion of the tank includes a plurality of the fluted plates, and is coupled to a pillar pil lar by a box girder in preferred personification. per sonification. Additional stiffening rings are also included i ncluded and additional floor can be included above water stored in the tank.
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13.1
DIAGRAMATIC DIAGRAMATIC COMPARISON BETWEEN SHAFT AND COLUMN TYPE OVERHEAD TANK
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