Thermal stress condition of experimental long blocks during construction period of the bratsk hydroelectric station dam

Abstract

1. The actual on-site investigations confirmed the correctness of the temperature condition as determined for the long experimental blocks. Maintenance of this condition assures a favorable development of thermal stresses, but deviation from it (large temperature drops, deep freezing, intensive cooling) results in surface cracks at the edges of blocks. 2. The formation of a field of thermal stresses in the monoliths is caused by the simultaneous action of their overall cooling and the non-uniform temperature distribution along the longitudinal sections. The following are considered to be favorable factors: a minimum temperature difference between adjacent blocks, low concrete mix temperature, and a prolonged process of exothermic heating. The compressive stresses, conditioned by this process, to a considerable degree compensate the tensile stresses arising from cooling of blocks and, obviously, prevent cracks from forming in the central zone of the monoliths. It is questionable, however, whether under the Siberian conditions the creation of the surface cracks in the long blocks can be avoided. From this standpoint, they have no advantage as compared to the blocks of columnar section. 3. The stresses in the reinforcement of the plate, separating the long blocks from the columnar ones, reach high magnitudes due to seasonal openings of the inter-columnar joints covered by the plate. This should be taken into account in calculating the reinforcement.