RATIONAL DESIGN FOR - THE ELBOW PORTION OF THE SUBSTRUCTURE OF A HYDEL POWER STATION. (IN THE LONGITUDINAL DIRECTION)

Abstract

A hydel power st4ition can be subdivided into three portions in order to clearly signify their hydraulic and struc-tural functions. These are substructure, intermediate structure and the superstructure. The substructure while acting as a foundation transition member for the power house building also acts as a structurally lctrong member to support load of genarat-ing plant and superstructure floors over the cavity. Due to the complex= shape of the draft tube cavity, there is no fixed method for analysing the elbow portion above the draft tube cavity. Different organisations in the world have put forth various practices. in order to evolve a rational design for this portion of the substructure. twentytwo (22) frames of different proportions have been analysed for finding total tention developed due to the superimposed lotr using the following methods s 1. First Lift method 2. Funicular Curve method 3. Deep Beam method 4. Rigid Frame teethed Photo-elastic results for some of the representative frames were available and the computed results have been compared. From the trends of such comparisons it has been concluded that one need not go in for the lengthy rigid frame-work analysis for the elbow portion of substructure if the height of concrete is half the span of opening or more. The analysis by "deep beam" or "funicular curve" method will not only be simpler requiring less time but will also involve saving in steel.