DYNAMIC CHARACTERISTICS OF A BARRAGE AT VARIOUS STAGES OF CONSTRUCTION

Abstract

The objective of this dissertation is to study dynamic characteristics of a barrage consisting of five bays at various stages of construction using finite element method and to study the dynamic behavior of structure at each stage(height of construction is I .5m) of construction. The Finite Element package, ANSYS has been used to carry out the various analyses. The barrage is located partly on soil and partly on rock. The barrage has been analyzed considering a total of three composite models. Composite models comprise bayl and bay2 in the first model, bay3 and bay4 in the second model and bay5 in the third model. Each model has been analyzed at different stages of construction. Total fourteen stages have been analyzed for each model. The Barrage has been modeled using 3D Solid45 elements (8 noded brick elements). Relevant amount of soil around the Barrage has also been modeled to find out the effect of soil on the structure. Free vibration analysis has been carried out to find out the natural frequencies and mode shapes considering stiffness of the soii and mass and stiffness of the structure. Seismic analysis of the Barrage has been carried out using the response spectra of the site by giving excitation in transverse direction. The weight of structure goes on increasing up to twelfth stage of construction, however at the thirteenth stage of construction top of pier is connected by slab, which changes the behaviors, therefore critical stage of construction is twelfth stage. The study indicates that the intermediate state stresses are likely ,,to exceed the stresses in the completed structure; both in raft and pier. Further, a detailed finite element analysis is more realistic in these situations, which takes into effect various parameters in the study of complex continuum, yielding design values where conventional techniques/methods are incapable of providing a solution.