Design of cost effective composite reinforced brick work-ferro cement water tanks

Abstract

In Sri Lanka, the most of the farmers are in dry rural areas and due to lack of water they can't cultivate in an effective manner. Therefore, there is a great need of designing and constructing of water tanks for rainwater harvesting purposes. This research was carried out to formulate design and construction of water tanks by using low cost materials with easy methods of construction and sufficient strength. Then water tanks can be constructed as fully underground, partially under ground as well as above ground, tanks. Since Sri Lanka is developing country and these tanks are going to be constructed in the rural area, the construction method should be cost effective as well as simple. Ferro-cement is low cost material and it does not require some formwork like in concrete. And also it does not require skilled workers and supervision and also the maintenance is very much easy. The design is based on analytical results obtain from a computer programme. An experimental investigation was carried out to find the properties of the construction materials required for the design. The computer programme had been already developed for the two types of water tanks, which are cylindrical tanks with spherical roof and flat bottom and cylindrical tanks with spherical roof and spherical bottom. This computer programme was further developed to analise the cylindrical tank with conical roof and spherical bottom. All the tank types can be analyzed using this software for fully under ground, partially under ground and above ground tanks. The linear elastic theory of shells is used to develop this programme. The optimum dimensions for the water tanks, which gives the highest strength can be found by using the computer programme. It was found that there are three main parameters, which influence to the combined stress in the tank. The main parameters are, limiting angle of the spherical roof, limiting angle of the spherical bottom and radius of cylindrical tanks. The sensitivity analysis was carried out by varying only one parameter at a time while keeping all the others constant. The analysis was done for all the load cases. According to the results of the parametric study, optimum tank shape was selected for 25m3 capacity tank. The structural design was carried out for the optimum tank shape. A construction process is also presented for the selected tank shape.