OPTIMUM DESIGN OF CONCRETE GRAVITY DAM SECTION CONSIDERING. EARTHQUAKE FORCES

Abstract

With the object of studying the relationships between the upstream and downstream slopes of concrete gravity dams, the earthquake inertia forces developed and the resistance offered by the sections, several sections with different slopes having three different heights have been analysed by the method of dynamic analysis. In this method, one dimensional cantilever method has been used to calculate the natural frequencies and mode shapes. The reservoir empty condition and the reservoir full condition are both considered. The dynamic effect of the water in the reservoir has been de lth with by treating it as "equivalent hydrodynamic mass" as well as hydrodynamic pressure Having determined the natural frequencies and mode shapes , the response of the dam sections is computed using the average acceleration spectra. The total response in various modes ha' been evaluated using mode superposition method according to root-mean-square combination . The results worked out are the dynamic displacements, sheare,moments and effective accelerations along the height. Static and dynamic stresses as well as principal stresses have been worked out on both faces of the sections.It is found that increasing the total slope of the faces reduces the principal tensions. An increase in the upstream slope is more effective in reducing the principal tension on the upstream face.