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design of overhead water tank pdf ppt
#1

design of overhead water tank pdf ppt

RCC WATER TANK DESIGN BASIS


Reinforced Concrete Water tank design is based on IS 3370: 2009 (Parts I IV). The design depends on the location of tanks, i.e. overhead, on ground or underground water tanks. The tanks can be made in different shapes usually circular and rectangular shapes are mostly used. The tanks can be made of RCC or even of steel. The overhead tanks are usually elevated from the roof top through column. In the other hand the underground tanks are rested on the foundation.

TYPES OF WATER TANK

Basing on the location of the tank in a building s tanks can be classified into three categories. Those are:

Underground tanks
Tank resting on grounds
Overhead tanks
In most cases the underground and on ground tanks are circular or rectangular is shape but the shape of the overhead tanks are influenced by the aesthetical view of the surroundings and as well as the design of the construction.

Steel tanks are also used specially in railway yards. Basing on the shape the tanks can be circular, rectangular, square, polygonal, spherical and conical. A special type of tank named Intze tank is used for storing large amount of water for an area.

The overhead tanks are supported by the column which acts as stages. This column can be braced for increasing strength and as well as to improve the aesthetic views.

BASIS OF CONCRETE WATER TANK DESIGN

One of the vital considerations for design of tanks is that the structure has adequate resistance to cracking and has adequate strength. For achieving these following assumptions are made:

Concrete is capable of resisting limited tensile stresses the full section of concrete including cover and reinforcement is taken into account in this assumption.
To guard against structural failure in strength calculation the tensile strength of concrete is ignored.
Reduced values of permissible stresses in steel are adopted in steel are adopted in design.
CIRCULAR WATER TANK

The simplest form of water tank is circular tank. For the same amount of storage the circular tank requires lesser amount of material. More over for its circular shape it has no corner and can be made water tight easily. It is very economical for smaller storage of water up to 20000000 liters and with diameter in the range of 5 to 8 m. The depth of the storage is between 3 to 4 m. The side walls are designed for hoop tension and bending moments.

PERMISSIBLE STRESSES IN CONCRETE

To ensure impervious concrete mixture linear than M 20 grade is not normally recommended to make the walls leak proof the concretes near the water face need to such that no crack occurs. To ensure this member thicknesses are so designed that stress in the concrete is lesser then the permissible

THE PERMISSIBLE STRESS IN STEEL

The stress in steel must not be allowed to exceed the following values under different positions to prevent cracking of concrete.

When steel is placed near the face of the members in contact with liquid 115 N/ sq mm for ms Bars and 150 N/ sq mm for HYSD bars.
When steel is placed on face away from liquid for members less than 225 mm in thickness same as earlier.
When steel is placed on the face away from the liquid for members 225 mm or more in thickness: 125 N/ sq mm for M.S. bars and 190 N/sq mm for HYSD bars.
BASE FOR FLOOR SLAB

The floor slab should be strong enough to transmit the load from the liquid and the structure itself to the ground without subsidence. The floor slab is usually 150 to 200 mm thick and is reinforced with nominal reinforcement, which may be provided in the form of mesh both at top and bottom face of the slab. Before laying the slab the bed has to be rammed and leveled then a 75 mm thick layer of lean concrete of M 100 grade should be laid and cured. This layer should be covered with tar to enable the floor slab act independently on the bottom layer. In water logged soils the bottom layer of concrete should preferably be of M 15 grade.

MINIMUM REINFORCEMENT FOR WATER TANK

Minimum reinforcement required for 199mm thick sections is 0.3 % of the area of concrete section which reduced linearly to 0.2% for 450 mm thick sections. In case of floor slab for tank resting on ground the minimum reinforcement from practical consideration should not be less than 0.3% of the gross sectional area of the floor slab.

If the thickness of the section (wall, floor or roof slab of the tank) works out to be 225 mm and above two layers of reinforcing steel shall be placed, one near each of the section to make up the minimum reinforcement requirements.

Design Of Overhead Water Tanks
Storage reservoirs and overhead tank are used to store water, liquid petroleum, petroleum products and similar liquids. The force analysis of the reservoirs or tanks is about the same irrespective of the chemical nature of the product. All tanks are designed as crack free structures to eliminate any leakage.
Backed with a team of qualified civil engineers with specialization in various structural design experiance, we undertake various designing project for RCC overhead tanks of various capcities.
This draft standard lays down criteria for analysis, design and construction of reinforced cement concrete staging of framed type with columns or shaft type, for achieving a desirable level safety and durability of the supported liquid storage structure (container). Container may consist of any material like RCC, concrete,ferrocement, steel

CRITERIAS IN DESIGNING OF OVERHEAD TANK
Capacity : Capacity of the tank shall be the volume of liquid it can store between designed full supply level (FSL) and lowest supply level (LSL that is, the level of the lip of the outlet pipe). Due allowance shall be made for applying lining,coating or plastering to the tank from inside if any, when calculating the capacity of tank. The designated capacity
of tank excludes dead storage which is the quantity of liquid below lowest supply level (LSL).

Staging : It consists of components of structure supporting a liquid tank (container), to locate it significantly above
general ground level. Pedestals or blocks of short heights supporting a tank will not be called as staging. In general the term staging includes the structuralcomponents for foundations also.

Height of Staging : Height of staging is the difference between the lowest supply level of tank and the average ground level at the tank site.

Liquid Depth : Liquid depth in tank shall be the difference of level between lowest supply level (LSL) and full supply le
vel (FSL) or working top liquid level (WTL) of the tank. In case of liquid being water, the term water depth can be used. The design liquid depth for tank can be more than the liquid depth due to dead storage and due to rise of liquid in freeboard zone to be accounted in design.

Framed Staging : Staging consisting of columns and braces.

Shaft Staging : Staging consisting of shell like a circular or polygonal cylinder or hollow prism.

Liquid Tower : The structure consisting of tank (i.e. container) together with thestaging and foundation is termed as liquid tower.

Force actions : Include bending moments, torsion, shear forces, direct tensionor compression.

NATURE OF WORK FOR RCC OVERHEAD TANK DESIGNING

Documentation shall be prepared which should contain all salientfeatures of the work and engineering data and maintenance scheme of the work. It should cover the following.
Brief data and features like description of liquid to be contained, capacity of tank (in m ), height of free board (in m), staging height (in m).

Foundation investigation report and soil data, type of foundation, probable depthof foundation and net allowable bearing capacity of founding strata. The position of ground water table highest & lowest. Soil classification for seismic design.

Location of tower (e.g. polluted industrial area, sea front area, coastal area,urban area etc.) and purpose of storage of liquid (i.e. public water supply, fire fighting. Industrial etc.), pollutants, salts, soleplates if any in air, soil and ground water.

Specifications of concrete and its grade, type of cement to be used, limits of maximum and minimum cement content, grade of reinforcement bars.

Salient features of structure and construction, method of construction, guidance on release of form work. Clear cover of concrete on reinforcement bars for various members at different locations. Codes, standards, references for construction.

Design loads Density of concrete, liquid, soil, masonry etc.; provisional loads of finishing, flooring, rendering, coating, lining etc. as applicable,railing, parapets,masonry wall etc.; imposed loads on roof,balcony, walkways, platform etc.; Seismic zone, zone factor, response reduction factor, importance factor, critical damping factor, soil factor; Basic wind speed, k1, k2, k3, terrain category, Load of equipment if any etc.; Construction loads; any other loads.

Indian standards referred for design.

Design report containing basis of design, method of structural analysis, detailed computation of loads, structural analysis, design calculations with sizes of members and reinforcement.

Drawing with reinforcement detailing, instructions, brief specifications and notes.Locations of construction joints and its treatment should be specified on the drawing.

Guide for completion drawing, and completion report for record. Record of quality of construction.

Proposed scheme of condition survey and maintenance of structure.
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#2
A water tank is a container for storing liquid. The need for a water tank is as old as civilization, to provide storage of water for use in many applications, drinking water, irrigation agriculture, fire suppression, agricultural farming, both for plants and livestock, chemical manufacturing, food preparation as well as many other uses. Water tank parameters include the general design of the tank, and choice of construction materials, linings. Various materials are used for making a water tank: plastics (polyethylene, polypropylene), fiberglass, concrete, stone, steel (welded or bolted, carbon, or stainless). Earthen pots also function as water storages. Water tanks are an efficient way to help developing countries to store clean water.

Throughout history, wood, ceramic and stone have been used as water tanks. These containers were all naturally occurring and some man made and a few of these tanks are still in service. The Indus Valley Civilization (3000 1500 BC) made use of granaries and water tanks. Medieval castles needed water tanks for the defenders to withstand a siege. A wooden water tank found at the A o Nuevo State Reserve (California) was restored to functionality after being found completely overgrown with ivy. It had been built in 1884.
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#3
(12-24-2012, 03:33 PM)Guest Wrote: plz can u provide ppt of water tank design and report
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#4
plz can u provide ppt of water tank design and report

plz can u provide ppt of water tank design and report
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#5
what is the area for the overhead circular watertank capacity of 500000 litrs
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