DESIGN OF FLOATING FLOOR AND RIBBED FOUNDATION OF BARRAGE USING CONFORMAL MAPPING TECHNIQUE

Abstract

The main problem encountered in structural design of hydraulic structures , such as a barrage, is uplift pressure. In usual design of barrage , which is called gravity floor system, the floor at downstream side is designed as a counter weight to resist the pressure. In such design practice, a considerable thick floor is required. This solution , therefore , will cause new problems to arise, such as foundation failure due to low bearing capacity of soil, the construction problems like large. excavation, large concreting, and dewatering . Consequently the construction takes a long time and requires much money. In design of hydraulic structure founded on clayey soil (soft soil), uplift pressure can be used to reduce stresses on the soil base. In case of barrage with floating floor and ribbed foundation system, the floor is designed as thin as possible, but structurally the floor must strong enough to resist the pressure without cracking and permitted camber/deflection in the permissible range. The dimension of foundation is thus reduced. The floating floor and ribbed foundation barrage system has light weight but structurally it has high rigidity , because the provision of two or more ribs of reinforced concrete wall below the floor and girders in upper side arranged perpendicular to each other . The lower ribs not only act as foundation but also act as cut off at upstream , down stream and at any intermediate position.