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Posted by nileshbhadane123 - 08-17-2017, 12:25 AM |
Hi I want book of design steps of overhead rectangular water tank pdf |
Posted by shahna - 08-17-2017, 12:25 AM |
INTRODUCTION 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. Water or raw petroleum retaining slab and walls can be of reinforced concrete with adequate cover to the reinforcement. Water and petroleum and react with concrete and, therefore, no special treatment to the surface is required. Industrial wastes can also be collected and processed in concrete tanks with few exceptions. The petroleum product such as petrol, diesel oil, etc. are likely to leak through the concrete walls, therefore such tanks need special membranes to prevent leakage. Reservoir is a common term applied to liquid storage structure and it can be below or above the ground level. Reservoirs below the ground level are normally built to store large quantities of water whereas those of overhead type are built for direct distribution by gravity flow and are usually of smaller capacity. 1.1 OBJECTIVE 1. To make a study about the analysis and design of water tanks. 2. To make a study about the guidelines for the design of liquid retaining structure according to IS Code. 3. To know about the design philosophy for the safe and economical design of water tank. 4. To develop programs for the design of water tank of flexible base and rigid base and the underground tank to avoid the tedious calculations. 5. In the end, the programs are validated with the results of manual calculation given in Concrete Structure book. A water tank is used to store water to tide over the daily requirement. In the construction of concrete structure for the storage of water and other liquids the imperviousness of concrete is most essential .The permeability of any uniform and thoroughly compacted concrete of given mix proportions is mainly dependent on water cement ratio .The increase in water cement ratio results in increase in the permeability .The decrease in water cement ratio will therefore be desirable to decrease the permeability, but very much reduced water cement ratio may cause compaction difficulties and prove to be harmful also. Design of liquid retaining structure has to be based on the avoidance of cracking in the concrete having regard to its tensile strength. Cracks can be prevented by avoiding the use of thick timber shuttering which prevent the easy escape of heat of hydration from the concrete mass .the risk of cracking can also be minimized by reducing the restraints on free expansion or contraction of the structure. 1.1 OBJECTIVE 1. To make a study about the analysis and design of water tanks. 2. To make a study about the guidelines for the design of liquid retaining structure according to IS Code. 3. To know about the design philosophy for the safe and economical design of water tank. 4. To develop programs for the design of water tank of flexible base and rigid base and the underground tank to avoid the tedious calculations. 5. In the end, the programs are validated with the results of manual calculation given in .Concrete Structure. 2.1SOURCES OF WATER SUPPLY : The various sources of water can be classified into two categories: Surface sources, such as 1. Ponds and lakes; 2. Streams and rivers; 3. Storage reservoirs; and 4. Oceans, generally not used for water supplies, at present. Sub-surface sources or underground sources, such as 1. Springs; 2. Infiltration wells ; and 3. Wells and Tube-wells. 3.1Water Quantity Estimation The quantity of water required for municipal uses for which the water supply scheme has to be designed requires following data: Water consumption rate (Per Capita Demand in litres per day per head) Population to be served. Quantity= Per demand x Population 3.2 Water Consumption Rate It is very difficult to precisely assess the quantity of water demanded by the public, since there are many variable factors affecting water consumption. The various types of water demands, which a city may have, may be broken into following class Water Consumption for Various Purposes: Types of Consumption Normal Range (lit/capita/day) Average % 1 Domestic Consumption 65-300 160 35 2 Industrial and Commercial Demand 45-450 135 30 3 Public including Fire Demand Uses 20-90 45 10 4 Losses and Waste 45-150 62 25 3.3 Fire Fighting Demand: The per capita fire demand is very less on an average basis but the rate at which the water is required is very large. The rate of fire demand is sometimes treated as a function of population and is worked out from following empirical formulae: Authority Formulae (P in thousand) Q for 1 lakh Population) 1 American Insurance Association Q (L/min)=4637 P (1-0.01 P) 41760 2 Kuchling's Formula Q (L/min)=3182 P 31800 3 Freeman's Formula Q (L/min)= 1136.5(P/5+10) 35050 4 Ministry of Urban Development Manual Formula Q (kilo liters/d)=100 P for P>50000 31623 3.4 Factors affecting per capita demand: Size of the city: Per capita demand for big cities is generally large as compared to that for smaller towns as big cities have sewered houses. Presence of industries. Climatic conditions. Habits of economic status. Quality of water: If water is aesthetically $ people and their medically safe, the consumption will increase as people will not resort to private wells, etc. Pressure in the distribution system. Efficiency of water works administration: Leaks in water mains and services; and un authorised use of water can be kept to a minimum by surveys. Cost of water. Policy of metering and charging method: Water tax is charged in two different ways: on the basis of meter reading and on the basis of certain fixed monthly rate. 3.5 Fluctuations in Rate of Demand: Average Daily Per Capita Demand = Quantity Required in 12 Months/ (365 x Population) If this average demand is supplied at all the times, it will not be sufficient to meet the fluctuations. Seasonal variation: The demand peaks during summer. Firebreak outs are generally more in summer, increasing demand. So, there is seasonal variation . Daily variation depends on the activity. People draw out more water on Sundays and Festival days, thus increasing demand on these days. Hourly variations are very important as they have a wide range. During active household working hours i.e. from six to ten in the morning and four to eight in the evening, the bulk of the daily requirement is taken. During other hours the requirement is negligible. Moreover, if a fire breaks out, a huge quantity of water is required to be supplied during short duration, necessitating the need for a maximum rate of hourly supply. So, an adequate quantity of water must be available to meet the peak demand. To meet all the fluctuations, the supply pipes, service reservoirs and distribution pipes must be properly proportioned. The water is supplied by pumping directly and the pumps and distribution system must be designed to meet the peak demand. The effect of monthly variation influences the design of storage reservoirs and the hourly variations influences the design of pumps and service reservoirs. As the population decreases, the fluctuation rate increases. Maximum daily demand = 1.8 x average daily demand Maximum hourly demand of maximum day i.e. Peak demand = 1.5 x average hourly demand = 1.5 x Maximum daily demand/24 = 1.5 x (1.8 x average daily demand)/24 = 2.7 x average daily demand/24 = 2.7 x annual average hourly demand 4.1Design Periods & Population Forecast This quantity should be worked out with due provision for the estimated requirements of the future. The future period for which a provision is made in the water supply scheme is known as the design period. Design period is estimated based on the following: Useful life of the component , considering obsolescence, wear, tear, etc. Expandability aspect. Anticipated rate of growth of population, including industrial, commercial developments & migration-immigration. Available resources. Performance of the system during initial period. 4.2Population Forecasting Methods The various methods adopted for estimating future populations are given below. The particular method to be adopted for a particular case or for a particular city depends largely on the factors discussed in the methods, and the selection is left to the discrection and intelligence of the designer. 1. Incremental Increase Method 2. Decreasing Rate of Growth Method 3. Simple Graphical Method 4. Comparative Graphical Method 5. Ratio Method 6. Logistic Curve Method 7. Arithmetic Increase Method 8. Geometric Increase Method |