3D SEISMIC ANALYSIS OF HYDRAULIC STRUCTURES

Abstract

The earthquake behaviour of the major hydraulic structures is an extremely important problem since many important structures such as concrete gravity dam etc. are being built in the regions of high seismicity. In order to study the behaviour of such structures in general, a popular finite element package "COSMOS" has been used. The capabilities and the limitations of the package in analysing such structures have been studied. Linear static and dynamic analyses have been carried out and free vibration characteristics have been evaluated to understand the behaviour and the effect of modellings on the response. A few problems related with hydraulic structures such as Wye section of a penstock, overflow and non-overflow section of dams and pier section of dams have been chosen to study their behaviour. Although very limited capabilities of the software have been explored, the study has indicated that the preprocessor, solver and postprocessor are very powerful but there are still some limitations. Limitations are very obvious when modelling structures with curved surfaces. A comparison of 2D and 3D responses has been carried out and important conclusions are drawn. As a whole the package is quite robust and capable of handling the hydraulic structures. However, the package is limited to handle the hydrodynamic pressure and therefore it has to be calculated separately as virtual mass and mass are to be lumped at the virtual nodes.