Calculation of Temperature Changes in Mass Concrete of Hydro Power Plant

Following the needs of the hydro power plant (HPP) Lesce construction on the river Dobra in Croatia, the development of maximum temperatures in mass concrete blocks of the power-plant’ s gravity dam is analysed. Hardening of early age concrete is connected to chemical processes which go along with a severe temperature and dimensional changes depending on the quantity of cement, heat of hydration, initial temperature of concrete and temperature changes of the environment. When constructing mass concrete elements two conditions are set connected to temperature changes in concrete. One is the maximum temperature that concrete is allowed to achieve because of hydration process. The other condition is much more complex and it refers to the temperature gradient which is forming from the inside out to the surface and it is a consequence of the heat transfer from concrete block to the environment and of the small thermal conductivity of concrete. The problem is mathematically solved using two different methods for the heat transfer problems. First method is Schmidt’ s numerical method. With this method we solved one dimensional transient heat conduction. Second method of solving was a finite element method with the software package Cosmos/m. Problem was with this method solved on the two dimensional model which is subjected to a simetrical load so that results from both methods can be compared. With this method transient analysis was performed taking into account heat transfer through conduction and convection. Computer calculations of different extreme initial conditions and environmental conditions enable detailed analysis of different parameters of construction technology such as: height of blocks, quantity and type of cement, time-table of concreting and so on.